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108-07 - Ord. Amending County Code Chapter VI Capital Facilities
kn\t-IF t R\ c 0 f ORDINANCE AMENDING CHAPTER VI — CAPITAL FACIL TIES a OF THE MASON COUNTY COMPREHENSIVE PLAN TO INCLUDE AND ADOPT STORMWATER MANAGEMENT PLANS FOR THE AIR YN AND BELFAIR URBAN GROWTH AREAS AN ORDINANCE, amending Chapter vl — Capital Facilities — of the Mason County Comprehensive Mar, under the aufroroty of Chapter 36.70 and 36°7OA RCW° WC=L L f=AS, on AL gust '49 2006, the Weste m Was in ton Gr;•wth Mare r t �s s Board foLnd the Mason_ g �ge� nC� � 1 ���� o�g� County Compre'ensove 'Ian's Capita Facilities element ard L Fedor® Nan for stormwate r management in the :elfair and y dil r UrLoa l Growth Areas ear did .n y d �®� comply with CCW 36°70 °070(3)(d; of the Growth Vanagement Act; and the County red trLrmerous public workshops o encourage pudicoC partoCopatoo g and C.rnment in the drafting of the Storrwater Managemert Plans for the Allyn art �� � f C�r.wh Areas and inc�•�roorafied much ��° � as a P ti° _ y �l�aor Jrban l such pL b,oc C�•mnnent r esL 1; a �o WHE RIts, the County has prepared S:ormwater Managemert Plans r g nor she A yF and 3elfair Urban Growth Areas for ado,oticr by this ordirarce and for hcor orati °tre CapitaFacilities elemer ; and p on into WHEREAS, the Co Comprehensive Ha Allyn and ' &fair U Pioa my has revised tr e Ca oita l Facilities element of tne Mason n to incorporate by reference the Stormwater Management n Growth Areas, ano County aLsf 1, r the NOW THEREF R7F, H ERI BY OR ONIHD, hat the Board of Commissioners of Masor County hereby amends the Capital Facilities Hemen(Chapter Vl) of the Mason County Comprehensive Plan (as attached). DATED this day of September 2007° Board of Commissioners Mason County, Washington ATTEST: tetizt.,10reztas_.., RebecLa S Rogers, Clerks& the Board APPROVED AS Deputy osecuting Attorney BOARS OF COUNT OMMISSIONERS CONTY SRN TON Lynding Erickson, Ch /g r Tim Sheldon, Commissioner Gallagher, Commiloner Mason County Update of County's Stormwater Policies/Regulations and Development of Comprehensive Stormwater Management Plans Belfair Urban Growth Area Stormwater Management Plan: Addendum Submitted to: Mason County Department of Public Works 411 N. Fifth Street Shelton, WA 98584 Submitted by: Otak, Inc. 10230 NE Points Drive Suite 400 Kirkland, WA 98033 Otak Project No. 30784 August 21, 2007 Transmittal Mason County Update of County's Stormwater Policies/Regulations and Development of Comprehensive Stormwater Management Plans Belfair Urban Growth Area Stormwater Management Plan: Addendum Submitted to: Mason County Department of Public Works 41 I N. Fifth Street Shelton, WA 98584 Prepared By Otak, Inc. Joe Simmler, Ph.D. Project Manager Larry Grimm, PE Project Engineer Preface This Addendum to the Belfair Urban Growth Area Stormwater Management Plan (SWM Plan) (Revised edition, July, 2007) has been prepared by Mason County in order to address the additional comments received from the public, regulatory agencies and major stakeholders (Tribes and businesses) since the June 20, 2007 Public Hearing. The original deadline of August 6, 2007 for presentation and submittal to the Western Washington Growth Management Hearings Board has been extended for sixty days to October 6, 2007. During this time, the County has elected to produce this Addendum, presenting further revisions and enhancements to the second draft of the Allyn SWM Plan. The Belfair SWM Plan was funded by the Washington State Legislature through a budget proviso: Washington State Legislature 2005-2007 Capital Budget, Section 325(3). It is being Jointly administered by the Washington State Department of Ecology and the Puget Sound Partnership. Table of Contents Belfair Urban Growth Area Stormwater Management Plan Section I —Introduction Section 2—Receipt of Public Comments Section 3 Countywide Comprehensive SWM Program Section 4—Response to Public Comments: Plan Revision Section 5 Summary of Revisions to Original Draft SWM Plan Section 6—Future Public Involvement and Future Updates to the Plan References List of Tables Table 2-1 Grouping of Comments by SWM Topic Table 4-1 Recommended SWM Programmatic Elements and Costs Table 4-2 Recommended Belfair SWM Program Elements and Costs Figures Figure 3-1—Mason County SWMM Planning Area Map Appendix A —Water Quality, Fish Shellfish and Habitat Report Figure 4-I—Mason County WRIA Map Figure 4 2-2007 Threatened Shellfish Areas Figure 4-3—Allyn Surface Drainages Figure 4-4—North Bay Shellfish Sampling Areas Figure 4-5—Pickering Passage Shellfish Sampling Areas Figure 4-6—Belfair Surface Drainages Figure 4-7 Hood Canal Station #9 Shellfish Sampling Areas Mason County Belfair UGA Stormwater Management Plan i otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNBelfair.doc Section I —Introduction 1.1 Objective and Intent This Addendum to the Belfair Stormwater Management Plan (SWM Plan) was created by Mason County in order to respond to additional public comments received over the last several weeks It includes and addresses the comments received verbally at the June 20, 2007 public meeting and the comments received via letters and in coordination meetings with regulatory agencies since July 2, 2007 when the revised SWM Plan was issued to the public. The receipt and analysis of the various public comments has resulted in an enhanced set of programmatic SWM activities and revised capital improvement program, as documented in this Addendum. Both the completeness and comprehensiveness of the proposed Allyn SWM Plan have been expanded and enhanced. These comments have also been used to structure and guide the development of the Countywide Comprehensive SWM Plan, conceptually presented in Section 3.0. 1 2 Format and Content Public and regulatory comments collected from the June 20, 2007 public meeting and subsequent letters over the following weeks were reviewed, organized by topic and developed into recommended SWM Program enhancements. Each topic resulted in the collection of new information for water quality and shellfish, the expansion of an existing SWM activity or the addition of a new SWM activity or approach to the overall SWM Program. As an example, a decentralized approach has now been adopted to address the drainage related impacts of new development replacing the earlier approach using large regional centralized detention treatment and/or conveyance systems. Also, a new SWM Program initiative has been added to retrofit all existing development using low impact development techniques, such as the bio-retention swale, in order to treat stormwater runoff prior to discharge. Similar SWM Program enhancements have been made for public involvement, design criteria, development standards, maintenance, public education, public involvement, water quality monitoring, inter- and intra-agency coordination and funding. This Addendum and the July 2007 version of the final SWM Plan constitutes the final version of the SWM Plan proposed for the Belfair Urban Growth Area (UGA). 1.3 Overview of Public Process and BOCC Review This Addendum will go through a second public review process beginning August 27, 2007 that consists of a public meeting on September 10, 2007 presentation to the Planning Commission on September 17 2007, and presentation to the Board of County Commissioners (BOCC) at public hearings on September 18, 2007 ( and possibly October 2, 2007) prior to a final decision by the BOCC. Mason County—Belfair UGA Stormwater Management Plan 1 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use \Final TextJJS-MK3-DNBelfair.doc Section 2—Receipt of Public Comments 2.1 Public Review Process For Original Draft of the Belfair SWM Plan: Issued June 2007 The schedule for development and adoption of the Allyn UGA SWM Plan, and its associated public review process, has been driven by an August 6, 2006, Growth Management Hearings Board Final Decision and Order, which mandated the County's submittal of improved and adopted SWM Plan by August 6, 2007. In accordance with this target date, the draft Belfair UGA SWM Plan was developed and made available to the public in early June, 2007. The County hosted a public meeting to receive comments on the plan at the Port of Allyn on the evening of June 20, 2007, with the official comment period closing on June 29, 2007. For Revised Draft Issued July 2007 The plan was revised and re -issued on July 2, 2007, based on comments received at the public meeting and based on written comments from the Department of Ecology (Ecology) and the Puget Sound Action Team (PSAT) (now known as the Puget Sound Partnership (PSP)). A briefing and two public hearings were held on the revised plan. The first public hearing was conducted before the County's Planning Advisory Committee (PAC) on July 9, 2007. A briefing was held before the Board of County Commissioners (BOCC) on July 23, 2007, and the second public hearing was conducted before the BOCC on July 24, 2007. For Final Addendum. Issued September 2007 In early August, the Growth Management Hearings Board granted the County a 60-day extension of its original submittal deadline to October 6, 2007. This extension has provided the County the opportunity to continue to respond to comments and create this Addendum to finalize the SWM Plan. Completion of the Addendum precedes a second formal public review cycle that includes a public meeting scheduled on September 10, 2007, a PAC hearing on September 17, 2007, and a first hearing on adoption by the BOCC, scheduled for September 18, 2007. Should the first BOCC hearing be continued, a final hearing on adoption may be scheduled for October 2, 2007. 2 2 Comments Received The County received comments on the draft plan and revised plan through public meetings, letters, and meetings with regulatory agencies The following is a list of various sources of public comment that have been compiled and addressed in the Master Comment Response Matrix. (Note that the Master Comment Response Matrix is a separate document and is available upon request from the County.) Mason County Belfair UGA Stormwater Management Plan 2 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNBelfair.doc Section 2 Receipt of Public Comments Continued 1. Department of N cology Comment Letter Re• Allyn UGA SWM Plan, 6/29/07, Kim McKee, Unit Supervisor, Southwest Region Water Quality Program 2. Puget Sound Partnership Comment Letter Re• Allyn & Belfair UGA SWM Plans, 6/29/07, Brad Ack, Director 3. Department of Ecology Comment Letter Re: Belfair UGA SWM Plan, 7/2/07, Kim McKee, Unit Supervisor, Southwest Region Water Quality Program 4. Squaxin Island Tribe Letter Re• Allyn UGA SWM Plan, 7/24/07, John Konovsky, Environmental Program Manager 5. Lower Hood Canal Watershed Coalition Letter Re: Stormwater impacts to Hood Canal, 5/26/07, Robert Hager, Co -Chair 6. Lower Hood Canal Watershed Coalition Letter Re: County SW Policy and Regulations, 6/20/07, Robert Hager, Co -Chair 7. Lower Hood Canal Watershed Coalition Letter Re: Belfair UGA SWM Plan, 6/20/07, Robert Hager, Co -Chair 8. PAC Meeting Notes 7-9-07, Barb Robinson, Mason County, Deparuuent of Community Development, Director 9. Allyn Community Association Re: Allyn UGA SWM Plan Technical Issues, 6/29/07, Jeff Carey, President The various comments have been grouped by topic, as presented in Table 2-1, and have been used to shape the content and format of this Addendum to the revised plan. Additional comments taken from Section 10 of the revised plan also have been included in Table 2-1 and are numbered accordingly. Table 2-1 Grouping of Comments by SWM Topic Stormwater Management Topic Priority Public # of Comments Regulatory /Compliance/Programmatic Approval PSWQMP: 2.2.4, 2.16, 2.29 3 18 Basin Planning/Watershed Approval: 2.2.4, 2.18, 2.23, 2.2.2, 6 16 2.13, 3.4 Ranking of Problems: 2.2.4, 2.12, 2.18, 2.23, 2.37, 7.3 6 15 WQ Monitoring: 2.1.1, 2.1.2, 2.17, 7.12, 8.3, 8.14, 10.7, 10.32 8 12 12 4 Funding: 10.21, 10.34 2.1.1, 2.1.2, 2.5, 2.15, 2.17, 2.22, 2.25, 3.17, 7.5, 10.2, 5 17 Phase II NPDHS• 1.1, 1.9, 2.29, 3.17, 10.29 Agency Coordination: 1.5, 2.22, 3.17, 5.3, 7.7, 8.13 6 14 Inspection/Inventory/Maintenance: 1.4, 1.6, 1.10, 2.18, 2.23, 11 6 Mason County Belfair UGA Stormwater Management Plan 3 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use \Final Text-JJS-MK3-DNBelfair.doc Section 2—Receipt of Public Comments Continued 2.37, 3.8, 3.18, 3.19, 5.1, 8.14 7 12 Illicit Discharge Detection and Elimination (IDDE)• 1.8, 1.10, 2.2.4, 2.23, 2.37, 3.16, 3.18 8 11 Public Education: 1.10, 2.1.2, 2.22, 2.37, 3.17, 3.18, 5.2, 7.9 10 7 Public Involvement: 1.10, 2 2 9, 3.18, 3.19, 7.6, 8.14, 9.5, 10.3, 10.9, 10.10 Programmatic: 2.2.4, 3.19 2 20 3 19 Countywide SWMP• 1.7, 2.22, 3.2 Natural Resource Protection/Enhancement Water 10.31, Quality: 2.1.1, 3.6, 2.2.1, 3.10, 2.2.3, 3 2.16, 14, 4.1 (2.31), 4.2, 5.1, 2.35, 5.2, 6.1, 2.36, 2.38, 7.11, 3.1, 8.7, 3.3 21 2 Shellfish: 2.2.3, 2.28, 2.35, 2.38, 4.1, 6.2, 8.2, 8.7 8 10 9 9 Salmon/Habitat: 2.2.3, 2.22, 2.38, 3.14, 4.4, 8.11, 8.13, 10.7, 10.41 25 1 Retrofit Existing/Bioretention/Decentralized CIP: 1.2, 1.4, 1.6, 2.12, 8 6, 8.8, 2.17, 2.22, 8.9, 8.10, 2.40, 9.1, 3.1, 9.2, 3.17, 9.4, 4.1, 9.5, 10.28, 7.10, 8.13, 10.33 10.30, 3.14, 7.11, Development 2005 Manual/Design Standards: 1.10, 2.1, 2.17, 2.22, 3.17, 3.18, 11 5 5.4, 6.1, 6.2, 6.3, 7.2 16 3 Low Impact Development (LID) 1.3, 2.1, 2.7, 2.10, 2.11, 2.14, 2.19, 2.20, 2.21, 2.22, 2.40, 3.7, 3.17 7.8, 7.9, 10.12 9 8 Dispersion Stormwater On-site/Reduction Impervious of of Areas/Retention Native Vegetation: 2.2.1, 2.4, 2.9, 2.32, 2.33, of 2.36, 4.3, 4.4, 5.1 186 Total number of comments received: Of the 186 comments listed in Table 2-1, the top six topics account for 105, or 56% of the comments. The top six most common comments included the following, in order of priority • Retrofit Existing/Bioretention/Decentralized CIP, • Water Quality, • Low Impact Development, • Funding, • 2005 Manual/Design Standards, and • Inspection/Inventory/Maintenance. Additional comments were received from DOE and PSP as well as Washington State Department of Fish and Wildlife on the revised plan as noted in the sources below. Mason County—Belfair UGA Stormwater Management Plan 4 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNBelfair.doc Section 2—Receipt of Public Comments Continued Although not listed in Table 2-1, many of the comments were similar to those presented earlier and have been addressed in the following sections of this Addendum. 1. State Department of Fish and Wildlife Comment Letter Re• Allyn UGA SWM Plan, July 24, 2007 Brad Sele, Regional Shellfish Manager, Fish Program, Region 6 2. Meeting with Kim McKee of Ecology and Bruce Wulkan of the Puget Sound Partnership, July 18, 2007 3 E-mail of additional comments on the revised draft was received from Bruce Wulkan of the Puget Sound Partnership on August 15, 2007. 4 E-mail of additional comments on the revised draft was received from Kim McKee of the Washington State Department of Ecology on August 16, 2007. 2.3 Master Comment Response Matrix The County developed a Master Comment Response Matrix that includes comments received through public meetings, comment letters, emails, and regulatory meetings, as referenced in the preceding section. These comments from the public, regulatory agencies, Tribal and stakeholders have helped guide this second review and update of the proposed SWM Plan. As a result, the revised plan includes additional information on existing conditions related to natural resources, together with a comprehensive program to provide for future development and comply with existing and future regulatory requirements. The Response to Public Comments (Section 4) along with the revised SWM Plan presents the County's responses to all of the public comments received to date, and attempts to be responsive to each major topic, as listed above. These public comments, along with various regulatory requirements and local water quality, flow and habitat information, have also been used as the primary sources of guidance for the development of the comprehensive Countywide SWM strategy presented in Section 3. Mason County—Belfair UGA Stormmater Management Plan 5 otak II: \project\30700\30784\Reports \ Addendum \Final Text -Only JJS to Use\Final TextJJS-MK3-DNBelfair.doc Section 3—Countywide Comprehensive SWM Program 3.1 Stewardship of the Region's Natural Resources Objectives of the Countywide Comprehensive SWM Planning Process Mason County is blessed with a wealth of natural resources that significantly add to the local quality of life and the economy of the region. The County, recognizing its role as one of the primary stewards of these resources is in the process of developing a countywide stormwater management plan (SWM Plan) to both protect and enhance these resources. The primary objective of this plan is to protect water quality, shellfish, habitat, groundwater and their supporting natural processes and functions, to continue to promote and guide new development and to be responsive to existing and future regulatory requirements. 3.2 County's Watershed Planning Process Prioritization of Stormwater and Water Quality Problems The County's SWM Program is in its initial stages of development. The County has not had the opportunity to conduct watershed planning or to complete a comprehensive inventory of stormwater facilities or to assess the problems that stormwater runoff may be causing throughout the County. However, as a result of this initial SWM planning process, research has been undertaken and interviews have been conducted the results of which suggest that the County's current stormwater related water quality problems consist of the following: Nutrient and fecal coliform loadings into sensitive receiving waters. Research by the University of Washington and monitoring by Ecology, County and State departments of health, and State Fish and Wildlife suggest that nutrients and coliforms are having major impacts on local and regional receiving waters and their associated habitat areas. Failing and poorly designed and maintained septic systems have been identified as one of the major sources, and septic maintenance and monitoring programs have been proposed. Also, centralized wastewater collection, conveyance and treatment systems have been proposed for the Belfair and Hoodsport areas, and a small system has already been installed at the end of North Bay near the Allyn UGA. A second major source of nutrient and coliform pollution is through stormwater runoff. While stormwater runoff does not generate these pollutants, it does pick them up from various land uses, concentrates them and transports them directly into sensitive local receiving waters. Most of the runoff in the County is not adequately detained or treated, which causes both flow and habitat problems and increases the need for effective stormwater management, particularly within the more urban and developing areas of the County. Mason County Belfair UGA Stormwater Management Plan 6 otak H:Aproject \30700\30784\Reports \ Addendum \Final Text -Only JJS to Use\Final TextJJS-MK3-DNBelfair.doc Section 3—Countywide Comprehensive SWM Program Continued Impacts to water quality, shellfish and habitat areas. The impacts to local natural resources within Hood Canal and the southern reaches of Puget Sound are well documented. Monitoring within the areas adjacent to the Allyn UGA in North Bay and within the Belfair UGA in the south end of Hood Canal suggest that nutrients, and fecal coliforms from surface water runoff and failing septic systems are degrading water quality, freshwater streams and fish habitat, as well as saltwater shellfish rearing areas. Substantial documentation of these impacts has been recorded and on -going monitoring programs continue to provide updated status of local conditions on an annual basis. Many of the coliform monitoring stations show a steady increase in concentrations which are threatening recreational and commercial shellfish harvesting, and if unchecked will result in the decertification of many of the existing commercial harvest areas. Again, inadequately detained and treated stormwater runoff from developed areas has been identified as one of the primary causes of continued and increasing loadings of pollutants and their resulting degradation of water quality and threats to adjacent shellfish rearing areas. Additional controls of runoff from developed areas, as well as runoff from future developed areas, are being mandated by regulatory agencies, stakeholders and the public Additional development controls and guidance have been suggested in the County's SWM Planning processes to minimize these impacts, as described below in this Addendum. Erosion and sedimentation. Erosion and sedimentation impacts generally have two major sources that often are interrelated, further enhancing the problem and the resulting impacts. Significant erosion can occur when a new site is graded for development After development, the increase in surface water flows often causes downstream channel erosion and undercutting of stream banks. Deposition of eroded sediments smothers sensitive spawning areas and if discharged into marine areas can also degrade shallow shellfish rearing areas. Addressing erosion related problems involves the development and enforcement of effective development standards and design criteria, as well as the effective management of onsite and downstream surface water runoff. Flood control. Flooding is common in certain parts of the County and is often the direct result of land use changes. Having good land use controls, including comprehensive planning, design standards and permit review along with enforcement processes are the primary tools for the control of flooding. Usually flooding is the cumulative effect of a series of major land use changes that occur over time throughout the watershed. Uncontrolled runoff with its associated property and habitat damageis the result of these changes. The effective control of flooding is directly related to the effective control of surface water, both during and after Mason County Belfair UGA Stormniater Management Plan 7 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DABelfair.doc Section 3—Countywide Comprehensive SWM Program Continued land use alterations. A comprehensive stormwater management program is needed within the County to support the County's flood reduction and management efforts. 3.3 Countywide Comprehensive SWM Management Strategy The County s proposed stormwater management strategy is a phased approach that initially focuses on the protection and enhancement of the County's most sensitive natural resources by addressing the SWM issues in the urban areas of the County. This strategy includes the development of a Comprehensive Countywide SWM Plan, with more in-depth technical studies in the areas of Allyn, Belfair, Hoodsport, Union and impacted sensitive areas such as Oakland and Annas Bays. The geographic extent of this initial phase of the countywide SWM strategy, as shown in Figure 3-1, includes: • The Urban Growth Areas of Allyn and Belfair, • The Rural Activity Centers of Hoodsport, Taylortown (I and II), and Union, and • The identified Water Quality Sensitive Areas of Oakland Bay and Annas Bay, as described in the. Oakland Bay Action Plan and Annas Bay Closure Response Strategy. Other urban and sensitive natural resource areas may be added in the future during the annual review and update of the proposed Comprehensive Countywide SWM Plan. 3.4 Focus of the Comprehensive Countywide SWM Plan Emphasis on Water Quality and Effective SWM in Urban Areas The County is committed to enhancing water quality and promoting effective stormwater management especially in its Urban Growth Areas (UGAs) and rapidly urbanizing areas, both within and adjacent to sensitive natural resource areas. This SWM planning strategy, as documented in the Comprehensive Countywide SWM Plan currently under development, is intended to address the drainage related impacts of existing and future development and to protect and enhance water quality, shellfish habitat and groundwater. (1 he draft Comprehensive Countywide S[T M Plan is scheduled for release to the public in the spring of 2008.) Developing a Comprehensive Countywide SWM Plan at this time allows the County to address immediate water quality, shellfish, and habitat needs and the requirements of the Puget Sound Water Quality Management Plan, as well as begin to prepare the County to come into compliance with a future National Pollution Discharge Elimination System (NPD E S) Phase II Municipal Stormwater Permit. Mason County—Belfair UGA Stormauater Management Plan 8 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use \Final Text-JJS-MK3-DNBelfair.doc Taylor Town I Rural Activity Center Taylor Town II Rural Activity Center � Legend clay 9 KITAP COUNTY Streams Streets Railroad Shellfish Protection District Rural Activity Center WRIA Boundary County Boundary Ny I_ __ 1 UGA Boundary Oakland Bay Clean Water District Figure 3-1 Mason County SWMM Planning Area Map W 0 N s 2 E 4 Miles 411 North 5t, P.O. Box 279 Shelton, Waslrngmn 98584 Phone: (360)427-9670 Fax: (360)427-8425 10230 NE Points Drive, Suite400 Kirtland, WasNngem 98033 Plane: (425) 822-4446 Fax: (425) 827-9577 KJproject/30700/30784/GIS/mxds/Figure3_1 MasonCoSWMMVer2.mxd Section 3—Countywide Comprehensive SWM Program Continued 3.5 Relationship to Allyn and Belfair SWM Plans The Allyn and Belfair UGA SWM Plans will complement and support the development of the Comprehensive Countywide SWM Plan. These SWM Plans have been developed by: • Collecting information and characterizing the various drainage areas, ® Evaluating existing facilities and planning for future capital needs, o Reviewing and evaluating regulatory compliance/programmatic needs in comparison to the County's existing surface water management program, ® Combining the recommended capital and programmatic needs together, along with costs and a schedule for implementation, to form the SWM Plan, and o Providing a financial plan, outlining various potential funding mechanisms and amounts of annual revenues. A similar SWM Plan for the Hoodsport area of the County is currently being developed and is expected to be released for public review in the spring of 2008. Shellfish protection and recovery plans are also under development for the Oakland and Annas Bay areas. As these SWM technical documents for the County's UGAs, Rural Activity Centers (RACs), and Water Quality Sensitive Areas (WQSAs) are developed, they will be reviewed by the public and approved by the BOCC and included as technical appendices to the County's Comprehensive SWM Plan. 3.6 A Comprehensive Watershed -Based Approach Elements of the Countywide Comprehensive SWM Plan Similar to the Allyn and Belfair SWM Plans the County s Comprehensive SWM Plan will assume a watershed based management philosophy for the protection of natural resources and the establishment of effective stormwater management throughout the County. This means that the County's Comprehensive SWM Plan will be based upon the technical, programmatic, capital and funding approach needed to achieve natural resource protection objectives, compliance with the PSWQMP and future Phase II NPDES Permit and support continued growth. It will emphasize the protection and enhancement of the natural resources throughout the County. It will include a series of programmatic elements, as well as a capital improvement program (CIP) for both the short- and long- term planning periods. The short term CIP will support growth over the next six years, while the long term CIP will address ultimate buildout, as defined in the County's Comprehensive Plan. In the more urban UGAs, RACs, and WQSAs, the adoption of a comprehensive SWM philosophy will require: Mason County—Be/fair UGA Stormzvater Management Plan 9 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Test JJS-MK3-DNBelfair.doc Section 3—Countywide Comprehensive SWM Program Continued • SWIM Program: Development, adoption and annual implementation and funding of a programmatic approach to stormwater management throughout the area, as presented in the PSWQMP and future NPDES II Permit (and described in the revised SWM Plan and in this Addendum), • Design Criteria for New Development: Adoption of the 2005 Ecology Manual for all new development, Adoption of Low Impact Development (LID), as a requirement of all new development, Review and possible adoption of revisions to the Development Standards of the Comprehensive Plan, requiring all future development be conducted according to current low impact principles that include minimizing new impervious areas, optimizing the preservation of natural vegetation (including the natural understory beneath the tree cover), disconnection of roof drains, infiltration of site runoff, and dispersion of surface runoff sheetflows into the remaining natural vegetation areas. • Hxisting Development:: Retrofit of existing impervious areas to detain and treat runoff from existing development prior to discharge using LID techniques (i.e. bio-retention), • County Road Design: Treating the runoff from all new County roads using LID techniques (i.e. bio-retention, water quality treatment filters, etc.), and • Funding: Establishment of adequate local funding to implement the annual Comprehensive Countywide SWM Program. In the more rural areas of the County, the adoption of a comprehensive SWM philosophy will be conducted in phases, on an as needed basis or until an NPDES II Permit is issued to the County. The SWM Program for the more rural areas will require: • SWM Program: Continued use of the County's existing SWM design criteria, • Design Criteria for New Development. Continued use of the County's existing SWM development standards and zoning codes, • Fxisting Development: Annual inspections and drainage system enhancements by the County Road Maintenance Crew to address small, localized flooding, water quality and sensitive area impacts on an as needed basis, • County Road Design: The treatment of runoff from all new County roads using LID techniques (i.e. bio-retention water quality treatment filters, etc.), and • Funding.: The establishment of adequate local funding to implement annual Comprehensive Countywide SWM Program for the less developed areas of the County. 3.7 Funding and Implementation Creation and Allocation of New Annual Revenues One of the challenges in developing a new Comprehensive Countywide SWM Program will be in creating the amount of new revenue needed to annually develop and operate the Mason County—Belfair UGA Stormwater Management Plan 10 otak FI:\project\30700\30784\Reports \ Addendum \Final Text -Only JJS to Use\Final Text-JJS-MK3-DNBelfair.doc Section 3 Countywide Comprehensive SWM Program Continued Program. Similar to the financial plans presented in the Allyn and Belfair SWM Plans, it is likely that various new revenue sources will need to be created and/or existing revenue sources will need to be reprioritized so that additional revenue can be directed to the new Comprehensive Countywide SWM Program. Creating Levels of Service In the development and implementation of Comprehensive Countywide SWM Program, as well as the SWM Plans for Allyn Belfair, Hoodsport and other sensitive areas, different levels of service will need to be described for each of the SWM planning areas. At least two levels of service are anticipated. The first is for SWM service within the more rural areas of the County. The second would be for SWM service within the more urban areas of the County, including the UGAs, RACs, and WQSAs In general, the level of service and types of service will be determined by the amount and type of revenue generated from within each service area. Annual SWM priorities, work programs, capital project (CIPs) and staffing levels would be defined according to the needs and available revenues from within each service level. It is likely that services within the rural areas would include those services similar to those that are presently being provided, while the services within the more urban areas would include additional design criteria for new development, enhanced maintenance, water quality monitoring inspection/enforcement and capital projects to enhance water quality and mitigate impacted habitat areas. 3.8 Implementation and Annual Reviews to Update and Refine SWM Plan The implementation and funding of the Comprehensive Countywide SWM Plan, as well as the Allyn and Belfair SWM Plans, will emphasize an initial series of recommended, high priority SWM programmatic activities and capital projects. The development of one or more dedicated funding sources has been recommended to meet projected annual revenue needs, however, additional revenues will likely be needed. It is important to recognize that this is not the end of the planning process; rather it is just the beginning. Throughout the continued development and implementation of these SWM Plans, the County will continue to gather data and learn more about the natural systems and the effectiveness of the various SWM initiatives. This information will be used on an annual basis to continue to evaluate the effectiveness of the proposed Plan. Using the process of adaptive management, further refinement and adjustment of the Plan will continue to enhance its overall effectiveness. Mason County Belfair UGA Stormavater Management Plan 11 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNBelfair.doc Section 4—Response to Public Comments: Plan Revision 4.I Overview: Summary of Comments As summarized in Table 2-1 and the Master Comment Response Matrix referenced in Section 2, numerous comments were received on the draft plan from several sources. From a review of these comments several major common topics emerged that were used to help structure the content and format of this Addendum. These common topics were developed into additional stormwater management planning activities, which were used to further expand and refine the proposed SWM Plan for Belfair, as well as create the foundation for the Comprehensive Countywide SWM Program. The additional SWM activities that resulted from the public review/comment process included the following: • Additional documentation and assessment of existing water quality and natural resource conditions, • Additional documentation and analysis of existing SWM drainage problems, • Development of a programmatic approach to SWM, • Fi,nhanced and expanded SWM design criteria and standards for new and redevelopment that emphasize low impact development techniques and promote water quality enhancement, • Review and enhancement of the annual maintenance program, • Redesigning the approach to capital facilities from a centralized, flow control approach to accommodate new development, to a decentralized onsite approach that emphasizes reduced impervious areas, onsite infiltration, retention of native vegetation and onsite dispersion of excess surface flows (i.e. low impact development), • Retrofitting existing development using low impact development techniques (i.e. bio- retention), • Defining the proposed water quality monitoring program, • Use of an expanded public education and involvement program, • Improved inter- and intra-agency coordination, and • Reprioritization and expansion of available funding. Each of these SWM Program elements of the proposed SWM Plan for the Belfair UGA have been further enhanced from the revised July 2007 draft of the SWM Plan in order to increase the protection and restoration of natural resources and respond to local water quality shellfish and habitat concerns, as voiced through the public comment process. Each revised, or refined SWM Program element is discussed in more detail in the following sections. Mason County—Belfair UGA Stormzvater Management Plan 12 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNBelfair.doc Section 4—Response to Public Comments: Plan Revision Continued 4.2 Existing Conditions• Characterization of Water Quality and Natural Resources Comment Summary: Numerous requests were made as to the need to conduct further research and document existing natural resource conditions the condition of current water quality and the status of current recreational and commercial shellfish harvesting. Additional comments were made regarding the need to correlate these observed and documented impacts with the direct discharge of undetained and untreated stormwater runoff from commercial and residential development. Direction was given by regulatory agencies and stakeholders to develop retrofit plans to treat and detain runoff from existing development and establish controls for new development so runoff from future development was minimized and sensitive resource areas were protected. Revised SWM Plan July, 2007). The revised SWM Plan included a section that characterized the study areas, consisting of the Urban Growth Areas, as defined in the County's Comprehensive Plan. While this review of the nature of the study area generally described the SWM Planning Area, it did not present a comprehensive view of the current state of research and monitoring. It noted water quality as an issue of regional concern and documented Ecology posted 303(d) listings and established TMDLs. Sensitive areas, consisting of wetland, stream buffers/habitat areas, fish bearing streams and aquifer recharge/protection were also recorded and mapped. Addendum Response: Due to the length of the report on local and regional water quality, shellfish and habitat resources and documented impacts from stormwater runoff, the text for this response has been included as Appendix A. Budget Impact Related to Revised Plan «uly, 2007): Based on public comment and these technical findings, substantial changes have been made to the proposed SWM Plan to protect and restore water quality, shellfish rearing, stream and fish habitat areas, as well as protect sensitive areas and shallow aquifers. The objective of the SWM planning process has shifted from the establishment of a capital improvement program to accommodate increased flows from future growth, to the development of a SWM Program that supports future growth, while also protecting and enhancing water quality and sensitive habitat areas. Mason County—Belfair UGA Stormwater Management Plan 13 ota k H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use \Final Text-JJS-MK3-DNBelfair doc Section 4—Response to Public Comments. Plan Revision Continued As a result of this change in objectives, the entire focus of this SWM planning process has shifted, from the development of a centralized, regional system of detention, treatment and conveyance to accommodate future development to a decentralized approach that emphasizes the use of low impact development, infiltration, dispersion and natural vegetation retention. The various elements of this natural resource based SWM Progiam are discussed below. 4.3 Existing SWM Drainage Problems Comment Summa y: A few citizens living within the UGA commented that the revised SWM Plan did not adequately document or address several localized existing drainage problems. Revised SI-VM Plan July, 2007): The revised Stormwater Management Plan for the Belfair UGA contained runoff estimates and capacity evaluations for existing drainage conveyance facilities, as well as a summary of reported drainage problems. This information was gathered from site visits, field tours with County staff, and follow up interviews with County maintenance and WSDOT maintenance crews. Additional information was collected and additional engineering analyses of the culverts under SR3 were performed and documented in the revised plans. Key information from those plans is provided in the following summary. 4.3.1 Belfair UGA There are no reported flooding problems at the existing culverts crossing SR 3 or NE Old Belfair Road, except where Mindy Creek crosses SR3. This culvert, if not maintained, can become clogged with debris resulting in localized flooding. An analysis was made of 20 of the culverts crossing SR 3 or \E Old Belfair Road to convey the 25-year peak flow assuming inlet control and a headwater to pipe diameter ratio of 1.25. Of the 20 culverts, 12 had adequate capacity and 8 were recommended for additional investigation of tributary flows and culvert capacity during annual maintenance activities. On the west side of SR 3, north of the Romance Hill Road intersection, it is reported that there is frequent flooding of a yard of a residence lust downstream from Mindy Creek. It is proposed that this problem be corrected as a part of the proposed SR 3 improvements by WSDOT In the northerly part of the commercial area, it is reported that runoff is bypassing catch basins in a commercial area and runningon to SR 3. This should be investigated by County maintenance personnel during annual maintenance and the excess flows should be redirected into the commercial drainage system. Mason County Belfair UGA Stormwater Management Plan 14 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNBelfair.doc Section 4—Response to Public Comments. Plan Revision Continued Addendum Response: Suggestions for increased annual inspections and a few local drainage studies and onsite fixes by the County maintenance crew have been proposed. These activities are consistent with the recommendations presented in the revised SWM Plan. Cooperation with WSDOT during annual maintenance and during the proposed revisions and expansions of SR3 also has been previously recommended. Budget Impact Related to Revised Plan July, 2007): No additional costs have been identified. These small localized drainage studies and their associated fixes have been recommended for inclusion into the County's established annual maintenance program, as proposed in the revised SWM Plan. 4.4 Comprehensive Approach to SWM Comment Summary: Many comments were received about the need to make the proposed SWM Program comprehensive and to structure the SWM Program based on the requirements of the existing Puget Sound Water Quality Management Plan (PSWQMP) and the future National Pollution Discharge Elimination System (NPDES) Phase II Municipal Stormwater Permit. Revised S1VM Plan July, 2007): The revised SWM Plan, presented to the public in July 2007, proposed a number of programmatic SWM activities that were either required by the existing PSWQMP or would be required in a future NPDES Phase II Stormwater Permit. As requested by public comment, the existing and upcoming regulatory requirements of the PSWQMP and the Phase II Permit were used to provide the basic framework for a comprehensive, programmatic approach to SWM that also includes short and long-term capital needs to address existing conditions and future growth. These programmatic SWM elements as presented in Table 8-1 of the revised plan, are summarized in this Addendum as Table 4-1. Mason County—Belfair UGA Stormwater Mana<gement Plan 15 otal< H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use \Final Text-JJS-MK3-DNBelfair.doc Section 4 Response to Public Comments: Plan Revision Continued 4-1—Recommended SWM Programmatic Elements and Costs Table SWMP Element Recommended Satisfies Needs Program Costs ($I,000's) Action PS WQMP NPDES Permit Phase II Shellfish Habitat WQ Yr I Yr 2 Yr 3 Yr 4 Yr 5 Yr 6 Total 1 Public Education* SWM Brochure (LID) X X X $5 $5 $5 $5 $5 $5 $30 2 Public Involvement* - Organize Volunteers/Mtgs X X X $25 $25 $25 $25 $25 $25 $150 3 Illicit (IDDE) - Inventory Facility Discharges & X X X $0 $25 $25 $0 $0 $0 $50 Mapping 4 New Development* - DOE - LID Ordinance Ordinance Manual - - 05 X X X $25 $25 $0 $0 $0 $0 $50 - Manual - - - 05 LID X X $25 $25 $0 $0 $0 $0 $50 Training Training - of Annual O/M Review X X X $0 $10 $10 $10 $10 $10 $50 5 Maintenance - Annual Plus X X X $25 $25 $35 $35 $35 $35 $190 Enhancements 6 SWM Implementation* - Develop Prog System X X $15 $15 $10 $10 $10 $10 $70 Tracking - Program Annual X X $0 $10 $10 $10 $10 $10 $50 Evaluation Mason County—Belfair UGA Stormwater Management Plan 16 H:\protect\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNBelfair.doc otak Section 4—Response to Public Comments. Plan Revision Continued 7 TMDLs X X $0 $0 $0 $0 $0 $0 $0 8 SWM Monitoring* (Addressed Element Program in X X $0 $0 $0 $0 $0 $0 $0 #6) 9 Reporting* (Internal) X $10 $10 $10 $10 $10 $10 $60 10 Basin (Part Co. of study.) Planning current X X $0 $0 $0 $0 $0 $0 $0 11 Develop SWM X $50 $50 $0 $0 $0 $0 $100 Funding - Utility - SDC Study Feasibility X $50 $50 $0 $0 $0 $0 $100 12 WQ - Monitoring Annual Monitoring X X $100 $100 $100 $100 $100 $100 $600 WQ Total: $330 $375 $230 $205 $205 $205 $1550 *Future Staff County 1 $55 $55 $50 $50 $50 $50 $310 (� FTE) Outside Services $275 $320 $180 $155 $155 $155 $1240 Addendum Response: Based on additional public and regulatory comments, the revised SWM Plan (presented in July, 2007) was further expanded to include additional enhancements of the following SWM Program elements described below in Sections 4.5 to 4.11. The financial impact of these additional SWVI activities is summarized in the revised financial plan presented in Section 4.12. Budget Impact Related to Revised Plan July, 2007): In general, no additional revenue has been proposed for the annual implementation of the proposed revised SWM Plan. Annual revenues are projected to remain at about $400,000 per year, based on the multiple funding sources presented in the financial plan. The funds proposed for baseline water quality monitoring ($100K) and the funds proposed for centralized capital facilities ($100K) in the revised plan have been re -assigned to accommodate the new SWM Program priorities established through the public review process, as discussed below and summarized in Section 4.12 of this Addendum. Note that in the revised budget for this Addendum, presented in Table 4-2, some additional funds have Mason County—Belfair UGA Stormwater Management Plan 17 otak I-I:\protect\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text JJS-MK3-DNBelfair.doc Section 4—Response to Public Comments: Plan Revision Continued been added to public education and illicit discharge detection and elimination in years 3, 4, 5 and 6. 4.5 Programmatic Development Design Criteria -Emphasizes Use of 2005 Manual / LID Comment Summary: A common theme to both the public and regulatory comments, as well as those received from the Tribe and the shellfish industry, was the need for the County to adopt the Ecology 2005 Manual in order to protect sensitive areas.. Numerous comments were also received recommending that the County also develop, adopt and require the use of low impact development (LID) throughout the UGA for all future development. Revised Plan Response: The revised SWM Plan recommended adoption of the hcology 2005 Manual and the development of a new ordinance requiring LID throughout the UGA for all new development Addendum Response: These two recommendations have not been changed in this Addendum. The County is intending to adopt the Ecology 2005 Manual and to develop and adopt a LID ordinance as part of the process to adopt this SWM Plan. The LID ordinance will be adopted concurrent to the adoption of this SWM Plan, as a modification to the County's existing land use criteria. LID for all new County Roads: With the documented need to further control the impact of stormwater runoff, the County has also elected to modify theCounty Road Design Standards so that the treatment of runoff is mandated during the design and construction of all new County roads throughout the UGA. The water quality treatment standards will stress the use of water quality filters and the use of bio-retention in roadside swales, along with other LID techniques. Budget Impact Relative to Revised Plan: These SWM recommendations are consistent with the revised SWM Plan and do not require the allocation of additional annual SWM revenues, however, the treatment of runoff from all new County roads within the UGA will increase the price of future road projects. (1 hose costs and the corresponding increases in County road projects have not been included in this SWUM planning analysis.) Mason County—Belfair UGA Stormwater Management Plan 18 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNBelfair.doc Section 4 Response to Public Comments: Plan Revision Continued 4.6 Programmatic: Annual Maintenance Program -Review and Enhancement Comment Summary: Concerns were expressed by the regulatory agencies that runoff from existing County roads was not being properly detained or treated prior to discharge into local receiving waters. They suggested an enhanced maintenance program be put in place that updates current O/M practices and includes a new emphasis on the treatment of runoff from County roads prior to discharge into local receiving waters. Revised Plan Response: The revised SWM Plan stressed the importance of annual maintenance and recommended regular inspection of facilities within the UGA to continue to maintain vegetation, remove debris and enhance coordination with WSDOT in regard to conveyance systems under SR3. There was also the recommendation to begin to inventory the countywide SWM system of drainage facilities in anticipation of the upcoming requirement to establish an illicit discharge detection and elimination (IDDE) program. Addendum Response: This Addendum continues to emphasize of importance of regular annual maintenance by further recommending improvements in the annual maintenance program to conduct small localized drainage studies and construct small CIP fixes in the field on an as needed basis. County Roads has also made the commitment to enhance it efforts to detain and treat stormwater runoff within its roadside ditches by adding water quality treatment filters and other LID techniques, including bio-retention swales in order to reduce pollutant loadings to local sensitive receiving waters. Budget Impact Relative to Revised Plan: The annual SWM O/M program has been increased to conduct regular inspections of its major facilities serving the UGAs, to conduct small studies, to fix local drainage problems (an increase of $20,000 per year), and to begin to design and build water quality treatment facilities within roadside ditches (about $80,000 per year). (Note that this enhanced annual maintenance program would also include the short term CIP activities presented in the revised SWM Plan. Such activities include coordination with WSDOT and routine culvert inspection.) Mason County — B e l f a i r UGA stormwater Management Plan 19 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNBelfair.doc Section 4—Response to Public Comments: Plan Revision Continued 4.7 CIP Strategy - Short -Term: Retrofit of Existing Development Using LID Comment Summary: One of the primary criticisms of the earlier drafts by the regulatory agencies was that the proposed SWM Plan did not address existing water quality problems or attempt to control their various sources. Agencies suggested that an effective SWM Plan for Mason County should contain adequate funding in the capital improvement program to detain and treat stormwater runoff from existing development before it was discharged into local receiving waters. Revised Plan Response: The revised plan, published in July, 2007, proposed to use annual water quality monitoring to define local water quality problems and their sources. This would allow the County to identify and prioritize existing water quality problems for future funding. Proposed water qualitv enhancement activities and projects would be designed and tailored to the nature and extent of the localized problem. The intent was that the highest priority problems would be addressed on an annual basis. Funding for annual water quality monitoring was proposed at $100,000 per year. No additional future funds were identified in the proposed capital program, or allocated to the fixes, that may be needed to address the identified problems. Addendum Response: An Overview: Using LID to Replace Traditional SWM Engineering Techniques: This Addendum proposes to revise the original approach to capital projects Low impact development (LID) will be used to treat existing stormwater runoff, as well as address the stormwater capital needs associated with future development. The addition of water quality treatment to address existing problems is discussed in this section and is the first part of a two part capital improvement strategy The second part is to continue to use LID techniques to address the stormwater needs of future development. Using LID to address future capital needs is presented in the following section, 4 8 This approach replaces the regional, centralized approach that was proposed in the revised SWM Plan to address the future capital needs within the UGA. Using a LID type of an approach emphasizes the objective to reduce existing and future impervious surfaces, optimize the retention of natural vegetation, infiltrate on site as existing soils allow, and disperse runoff in a sheetflow manner into remaining naturally vegetated areas. This approach is in contrast to the traditional engineering approach that would typically route all runoff from the site into a network of regional collection and conveyance facilities that would lead to a series of large, onsite or regional detention and treatment facilities, where the runoff would be treated prior to its discharge to local receiving waters. Mason County—Belfair UGA Stormwater Management Plan 20 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-V K3-DNBelfair.doc Section 4—Response to Public Comments. Plan Revision Continued Using LID to Treat Existing Stormwater Runoff: Rather than relying on water quality monitoring and enhanced maintenance to address the existing water quality problems as presented in the revised SWM Plan, funds have been shifted from annual water quality monitoring to an aggressive program to retrofit the existing drainage system for water quality treatment. Using LID techniques, primarily in the form of bio-retention swales, runoff from existing development would be detained and treated prior to discharge. The emphasis would be on providing water quality treatment. The duration and type of detention would be primarily that needed to provide effective treatment rather than rate control. The goal would be to design and build ten to twelve LID facilities throughout the most urban areas of the UGA over the next six years, approximately two per year. The approach would be to locate approximately five/six of these facilities on existing County property, primarily within the County road right-of-way. The other five/six facilities would be located on existing private property, primarily on the downstream areas of the larger expanses of existing impervious surfaces, such as parking lots and outdoor storage/shipping receiving areas. Retrofitting possibilities for individual commercial properties include infiltration of roof runoff, collection and pretreatment of road and parking area runoff in rain gardens or catch basins with water quality filters, followed by infiltration and treatment within a soil matrix contained in a bio-swale/bio- retention type of design Working with existing residences and commercial businesses would be on a cooperative basis and it is the intent to develop incentives to entice the business community to participate. Financial partnering through the use of grants, loans, and other in -kind services is also being considered. (A technical overview of the use of LID (i.e., bio-retention facilities) for water quality treatment is presented below.) Note that the County is also considering the treatment of runoff from County roads using water quality treatment filters of various designs and removal mechanisms to address the runoff from its impervious surfaces. One device involves the use of a bio-treatment medium within a suspended filter device that would be placed within an open drainage ditch along the County road. These devices would be used in replace of or in concert with the above bio-retention LID types of devices. Technical Review of the Use of LID for Local Water Quality Enhancement: Retrofitting of existing commercial areas with water quality treatment facilities using LID will improve the quality of runoff being discharged from those areas. Bio-retention facilities are a good candidate for retrofits at commercial sites with Hydrologic Soil Type A and B soils. as these Mason County—Belfair UGA Stormwater Management Plan 21 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use \Final Text-JJS-MK3-DNBelfair.doc Section 4—Response to Public Comments. Plan Revision Continued soils are well suited for infiltration of stormwater. With some design modification (i e , adding an under dram) LID techniques could also be used in Type C .and D soils. The 2005 Ecology Stormwater Design Manual lists bio-retention facilities/rain gardens as one option to satisfy basic and enhanced water quality treatment requirements. The 2005 Ecology recommends both Appendix III-C of the 2005 Ecology Manual and The Low Impact Development Technical Guidance Manual for Puget Sound (LID Manual) for design guidance. Both design references area available on the World Wide Web. For a typical commercial site (assuming 85 percent impervious cover and 15 percent landscape cover) located in outwash soil, approximately ten percent of the site is required for a bio-retention facility/rain garden (as determined using MGS Flood to size an infiltration facility that infiltrates at a rate of 1-inch per hour). For example, a 60-foot by 100-foot commercial lot (0.14 acre) would require a 600 square -foot bio-retention facility The project cost, which includes construction and design costs, of a 600 square -foot bio-retention/rain garden is $39,000 (approximately $7 per square foot of area treated). Runoff from roofs does not require water quality treatment if kept separate from street and parking lot runoff. The development of a standard bio-retention design and set of specifications for the UGA that could be adapted to specific sites could help reduce the cost of implementing these facilities. The following figure is taken from the LID Technical Guidance Manual for Puget Sound, 2005, courtesy of Puget Sound Partnership and illustrates a typical bio-retention cross section. This schematic is followed by photos of completed bio-retention facilities (also courtesy of Puget Sound Partnership).. In areas of till soils, where infiltration rates are low, a bioretention with an underdrain system or a different type of water quality treatment option, not relying on infiltration, may need to be selected from the Ecology list of treatment options (located in volume 5 of the 2005 Ecology Manual). Mason County—Belfair UGA Stormniater Management Plan 22 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use \Final Text-JJS-MK3-DNBelfair.doc Section 4—Response to Public Comments: Plan Revision Continued filter strip impervious surface Bioretention cross section, without underdrain Bioretention at Street Edge Alternatives (SEA) Project Seattle selected native plants and hardy cultivars planting :soil mix o liner or filter fabric From the LID Technical Guidance Manual for Puget Sound, 2005 Mason County—Belfair UGA Stormwater Management Plan 23 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNBelffir.doc Section 4 Response to Public Comments: Plan Revision Continued Bioretention at medical center, Olympia Photo by Bruce Wulkan, Puget Sound Action Team Budget Impact Relative to Revised Plan: The annual allocation of $100,000 to water quality monitoring presented in the revised SW1VI Plan has been re -assigned to provide detention and treatment of runoff from existing development throughout the UGA, with emphasis on the more commercial areas and areas of high traffic use. The cost of a bio-retention facility on County right-of-way has been estimated to be about $40,000, depending on local soils and site conditions. Approximately two of these facilities would be designed and built every year over the next six years. About $20,000 would be retained on an annual basis to monitor the performance of one representative bio-retention facility in order to measure performance. Collected information will be used to confirm treatment effectiveness and enhance future designs. (Note that the short-term CIP projects, consisting primarily of maintenance related activities, have been included in the enhanced annual maintenance program described in Section 4.6. Mason County—Belfair UGA Story/water Management Plan 24 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNBelfair.doc Section 4—Response to Public Comments. Plan Revision Continued 4.8 CIP Strategy - Long -Term: A Decentralized Approach Emphasizing LID Comment Summary: The regulatory agencies suggested that the County revise the Comprehensive Plan (Comp Plan) for the UGA in order to further enhance the use of LID techniques. The concept is to use additional LID approaches to address the drainage needs of all new development by changing the way the surface of the land is designed and laid out for future developed. This approach would take the form of revised development standards that would not change the densities presented in the Comp Plan, but would provide guidance that would reduce the amount of impervious area using LID approaches to land development. These land use standards would be used, and would work in concert with, the required 2005 Ecology Manual and the onsite LID ordinance. The goal of this type of an LID -based approach to land use development is to reduce/minimize the amount of new impervious surface, while optimizing the retention of native vegetation. It would emphasize the use of onsite infiltration and the dispersion and treatment of surface water runoff. If used on a uniform basis throughout the UGA this type of a regional decentralized approach to stormwater management could be used in lieu of the design and construction of the traditional large, costly centralized collection, detention, treatment, and conveyance/outfall facilities that require large parcels of land for effective performance. Revised Plan Response: The revised SWM Plan promoted the use of LID by the development and the adoption of an LID ordinance that would work in concert with the N,cology 2005 manual. The SWM Plan promoted the use of onsite detention and infiltration. The onsite drainage systems would be designed to operate along with regional collection, detention and treatment systems that would be primarily paid for by developers at the time the site was developed. Depending on the effectiveness of these systems, the County may or may not be required (at a future date) to design and build additional regional facilities to protect sensitive downstream natural resources and address the accumulative impacts of numerous develops within common watersheds and drainage basins. Regulatory agencies characterized this type of an approach as a traditional, regional and centralized approach of providing stormwater management facilities to support new development. Addendum Response: The County recognizes the potential advantages of taking an LID -based approach to new development through the UGA. It supports the concepts presented by the regulatory agencies and recognizes numerous advantages of adopting such an approach. These advantages would include less disruption of native land resulting in less runoff, and less erosion and sedimentation. This approach would both preserve and protect natural resources by providing enhanced protection of onsite and downstream sensitive areas and Mason County—Belfair UGA Stormwater Management Plan 25 otak I-1:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNBelfair.doc Section 4—Response to Public Comments. Plan Revision Continued natural resources. It also reduces the cost of the County's long-term capital facilities program and may reduce future maintenance costs as well In supporting this concept of land development and an alternative approach to providing future capital facilities for SWM throughout the UGA, the County will commit to further develop and explore these concepts by developing the required land use standards and presenting to the public and BOCC for review during the annual review and update of the County's Comprehensive Plan. Budget Impact Relative to Revised Plan: In response to this LID type of an approach to providing long-term SWM CIP, the $100,000 that had been annually set aside for long-term capital projects has been reassigned to other SWM Program elements and priorities. These other SWM Plan priorities, based on public and regulatory comment, include enhanced maintenance consisting of localized drainage studies and small CIP fixes ($20,000/year) and treatment of runoff in roadside ditches ($80,000/year). The long-term CIP project of relocating the Belfair Creek channel, costing $1.5M and scheduled for Year #15, has been put on hold, along with the Sweetwater Creek Fish Passage Improvements, until the short-term LID retrofit program for water quality treatment has been completed and evaluated. 4.9 Programmatic: Baseline Water Quality Monitoring Comment Summary: Numerous comments cited the significant amount of monitoring information available from state, local agencies and interest groups that documented water quality impacts from stormwater runoff to sensitive receiving waters and other natural resources. Several also expressed concern over the magnitude and immediacy of the need for action to correct observed and previously documented problems. Some suggested treatment approaches such as retrofitting existing development and the use of LID techniques. Others said that all runoff should be treated before it entered into local streams or receiving waters. Revised Plan Response: The June 2007 plan proposed the use of a baseline water quality and habitat study within the UGA to characterize the nature of stormwater runoff and establish the severity of its impacts. Results were to be used by the County to prioritize problem areas and guide the amount and type of future investments that would be needed to address local impacts. In the July 2007 revised SWM plan, this monitoring activity was expanded and additional funds were added to make water quality monitoring a major element of the new SWM Plan. Mason County—Belfair UGA Stormwater Management Plan 26 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Usc\Final TextJJS-MK3-DNBelfair.doc Section 4 Response to Public Comments. Plan Revision Continued Addendum Response: Based on the response of regulatory agencies and the public, as documented in Section 4.2 above, there appeared to be a general consensus that stormwater runoff was already a major problem for water quality, fish/habitat and shellfish within North Bay and the south end of Hood Canal. They suggested that, while additional monitoring would be helpful, the real need was to retrofit existing SWM facilities to detain and treat the runoff from all developed areas. As a result, most of the funds for the water quality monitoring program were shifted to help pay for retrofitting runoff from existing development. The remaining funds (about $20 000) will be focused on characterizing the water quality treatment effectiveness of the proposed bin -retention facilities that will be used to treat runoff from existing development Budget Impact Relative to Revised Plan: No net financial impact $80,000 will be shifted from water quality monitoring to detaining and treating runoff from existing development; $20,000 will be used annually to characterize the water quality treatment effectiveness of a bio-retention low impact development technique. 4.10 Programmatic: Public Education / Involvement Comment Summary: Regulatory agencies commented on the need for additional public education and outreach, as well as on -going public involvement. Most thought that a diversity of education and outreach techniques on an annual basis was needed. Some mentioned the need for the education of residents and the development incentives for them to take corrective action on their own properties. Many expressed the need to develop support for the plans through an on -going public involvement program. Revised Plan Response: The revised SWM Plan recommended distribution of a countywide brochure to the public addressing local stormwater pollution issues and homeowner solutions that included the benefits of LID and drew from available PSAT educational resources. The revised plan also included engaging community stakeholders in SWM planning and implementation within their respective UGAs. This included organizing volunteers to assist in Stream Team activities and various volunteer programs that could include water quality monitoring. Addendum Response: In this Addendum, the County has agreed to the establishment of a SWM Advisory Committee to assist County staff in the development of the County -wide SWM Plan. Mason County—Belfair UGA Stormwater Management Plan 27 otalc H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNBelfair.doc Section 4 Response to Public Comments: Plan Revision Continued As the County develops and implements various public education involvement activities, it would be good to expand the scope or theme of these activities so that everyone, both residential homeowner and business owner/operator, has a defined role in the protection, cleanup and enhancement of local water quality, streams, and shellfish rearing areas. ® For Homeowners: A Source Control Brochure that addresses ways that homeowners can reduce stormwater impacts through source control strategies such as reducing flows, disconnecting and directly infiltrating roof runoff, retaining or re-establishing vegetation onsite, carefully conducting pest management, reduction of lawn chemicals, proper disposal of pet waste, proper disposal of household hazardous wastes, etc. ® For Business: A Source Control Brochure that addresses ways that businesses can reduce stormwater impacts through source control strategies such as spill prevention, covering waste disposal areas to avoid stormwater contamination, integrated pest management, separating and infiltrating roof runoff, proper maintenance practices and frequencies, and retrofitting by adding bio-swales and rain gardens into their landscaping to enhance detention, infiltration, and treatment prior to discharge from their site. Future activities may include: exhibiting at local fairs/public gatherings use of the County's web site, mailings, brochures and volunteer programs for stream team plantings and water quality monitoring. Budget Impact Relative to Revised Plan: The revised SWM Plan provided $30,000 per year over the next six years for public involvement and education. The annual budget for public education has been increased to $25,000 per year in years 3, 4, 5 and 6. 4. I I Programmatic: Inter/Intra-Agency Coordination Comment Summary: In general, agency coordination did not receive much attention in the comments received from the public. The regulatory agencies, however cited the critical need for coordination with WSDOT in order to address local road runoff and common water quality, habitat and receiving water objectives. Jointly -funded water quality detention and treatment projects were also suggested to address regional needs. Revised Plan Response: Intra-Agency Coordination: The revised SWM Plan recommended coordination with WSDOT on maintenance, creek relocations, streetscape improvements and joint -use stormwater facilities. Mason County—Belfair UGA Stormwater Management Plan 28 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNBelfair.doc Section 4 Response to Public Comments. Plan Revision Continued Inter -Agency Coordination: The revised SWM Plan also recommended internal coordination with County Transportation and Parks programs to incorporate LID and water quality benefits into transportation improvements and planned park locations within the UGA. Addendum Response: Stormwater impacts on receiving waters are from diverse sources and often result in cumulative effects from the various land uses within the watershed Effective stormwater management requires teamwork from all the players/contributors to address those impacts. For this reason, this Addendum is including additional recommendations for both agency and internal coordination. In the future, the County intends to increase its level of coordination and cooperation with various local and State agencies, especially WSDOT, City of Shelton and County Public Health. Cooperation is needed on such issues as the design and funding of common local SWM projects, establishment of common design criteria within UGA areas and integrated programs to protect shellfish and restore water quality. The joint implementation of the Oakland Bay and Annas Bay shellfish response plans is already underway and could be used as templates of how to work together effectively to achieve common natural resource goals. These activities would complement and be in addition to the coordination activities already presented and discussed in the revised SWM Plan Quly, 2007) Budget Impact Relative to Revised Plan: The revised SWM Plan provided $30,000 per year over the next six years for public involvement and education. While no additional budget has been specifically recommended in this Addendum for inter/intra-agency coordination, the addition of a County SWM Program Manager will help facilitate the overall coordination of SWM activities throughout the County and the UGA. The cost of enhanced coordination should be able to be absorbed within SWM Program Filement #6, SWM Program Implementation. 4 12 Programmatic: Funding Comment Summa y.: The regulatory agencies stressed the need for the establishment of adequate levels of revenue to effectively implement the proposed SWVI Plan on an annual basis. They proposed setting up a countywide SWM utility and the establishment of developer impact fees. Other comments were received from the public that pointed to the need for the County to hire and train new staff to help develop and implement the proposed SWM projects and activities. Mason County—Belfair UGA Stormwater Management Plan 29 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNBelfair.doc Section 4—Response to Public Comments. Plan Revision Continued Revised Plan Response: The revised SWM Plan developed and presented a financial plan that was annually supported by a diversity of funding sources that included the formation of a UGA-wide SWM Utility. Potentially available annual revenues of up to $374,000 to $440,000 were forecasted, from seven different revenues sources. Annual SWM Program revenue needs of about $400,000 were estimated. The SWM utility was estimated to bring in about $100 000 annually, based on monthly rates of about $120 per year (or about $5-$10 per month) for the average residential homeowner, with commercial land owners paying more based on the amount of impervious area on their parcel. Addendum Response: A revised financial plan for the SWM Plan has been established and is presented in this Addendum. An annual SWM Plan budget of about $400,000 has been retained, and the same revenue sources and annual estimates of revenue have been maintained. Projected annual expenditures match projected annual expenditures of about $400,000. The various financial changes recommended above are summarized in Table 4-2. Table 4-2 Recommended Belfair SWM Program Elements Costs and SWMP Recommended Action Costs ($I,000's) Yr I Yr 2 Yr 3 Yr 4 Yr 5 Yr 6 Yrs 7-26* Element 1 Public Education $5 $5 $25* $25* $25* $25* -- 2 $25 $25 $25 $25 $25 $25 Public Involvement - 3 $0 $25 $25* $25* $25* $25* -- Illicit Discharges (IDDE) 4 $50 $60 $10 $10 $10 $10 New Development - 5 Maintenance $25 $25 $35 $35 $35 $35 6 SWM Prog. Implementation $15 $25 $20 $20 $20 $20 - 7 TMDLs $0 $0 $0 $0 $0 $0 -- 8 so $0 $0 $0 $0 $0 -- SWM Prog Monitor (In #6) 9 Reporting* $10 $10 $10 $10 $10 $10 (Internal) - 10 Basin Planning $0 $0 $0 $0 $0 $0 -- 11 Funding $100 $100 $0 $0 $0 $0 -- 12 WQ Monitoring: Baseline $0 50 50 $0 $0 $0 -- Programmatic Subtotal.: $230 $275 $150 $150 $150 .$150 CIP 1 Yrs I-6:WSDOT/Culrts (In #5) $0 $0 $0 $0 $0 $0 -- 2 $0 $0 $0 $0 $0 $0 -- Yrs7-26:Four Reg. CIP #5) (In $0 $0 $0 $0 $0 $0 -- CIP Subtotal.: Adden. 4.6 Enhanced 0 & M: Study/Fixes $20 $20 $20 $20 $20 $20 -- Mason County Belfair VGA Stormwater Management Plan 30 H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use \Final Text-JJS-MK3-DNBelfair.doc otalc Section 4—Response to Public Comments: Plan Revision Continued 4.6 WQ Treatment of Rd Ditches $80 $80 $80 $80 $80 $80 4.7 Retrofits for Water Quality $80 $80 $80 $80 $80 $80 4.7 WQ Monitoring: Retrofit LID $20 $20 $20 $20 $20 $20 Addendum Subtotal $200 $200 $200 $200 $200 $200 -- Total: = $384/yr) $430 $475 $350 $350 $350 $350 -- (Avg *Increased in the Addendum over the revised SWM Plan, July 2007. Budget Impact Relative to Revised Plan: In general, the following recommendations have been made to the annual budgets presented in this Addendum. • The $100,000 water quality monitoring program has been reduced to $20,000 to evaluate the water quality treatment effectiveness of bio-retention facilities the $80,000 balance has been used to design and build water quality retrofit facilities. • The $100,000 set aside annually for long-term centralized capital projects has been reassigned to other SWM Plan priorities listed below. • Annual maintenance has been increased by $20,000 to conduct small localized drainage investigations and complete small CIP fixes in the field. • A short-term CIP program costing $80,000 per year to retrofit the drainage system to detain and treat stormwater runoff from existing impervious surfaces has been proposed. The short-term CIP retrofit program consists of the design and construction of 10-12 bio-retention facilities throughout the more urbanized areas of the UGA over the next six years at the rate of about two facilities per year. Partnering with local property owners will be needed. • The hiring of one staff person to develop, supervise and implement the County's SWM Program has been recommended Staff responsibilities would includes the funding and implementation of both the Allyn and Belfair SWM Plans. Cost has been estimated to be about $50,000 to $80,000 per year, which could be split between the two SWM Plans. (Note that funding for a staff position can be realized if SWM Program Elements 1, 2, 4, 6, 8 and 9 are performed internally by County Staff.) • Remaining funds, of about $80,000 annually, may be assigned to the enhancement of the annual maintenance program to review and upgrade O/M practices and include retrofitting County road drainage ditches to detain and provide water quality treatment. • Note that as annual revenues increase and more knowledge and experience is gained in implementing the proposed SWVI Plan within the UGA, this initial SWM service level as defined in Table 4-2, will be subject to review and revision on an annual basis as part of the County s annual budgeting process. Mason County—Belfair UGA Stormzvater Management Plan 31 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-vIK3-DABelfair.doc Section 5—Summary of Revisions to Original Draft SWM Plan 5.1 Link between the SWM Plan and WQ in Hood Canal Throughout the development of this Addendum to the SWM Plan for the Belfair UGA, the County has focused on improving local water quality and its related stream/habitat areas. It recognizes and understands the direct link between dean stormwater runoff and the continuation of healthy shellfish rearing areas. It is for these reasons that: • The entire SWM planning strategy has been shifted from supporting new development by collecting and concentrating stormwater runoff and constructing large centralized regional SWM facilities, to an entirely decentralized approach that is based on LID techniques that minimized the impacts of future land use changes, as well as promotes the design and construction of onsite LID systems. • A facility retrofit program has been developed to detain and treat the runoff from existing development using LID techniques. • County road runoff will begin to be treated by retrofitting existing facilities, as well as by adding water quality treatment to all new County road designs. • The important role of regular maintenance has been developed and continues to be stressed, further expanding the need for adequate staffing and funding of O/M programs during the annual budget cycle. • The adoption of the Ecology 2005 Manual and the development and adoption of and LID ordinance continue to be promoted and are recommended. • Citizen and stakeholder input and involvement has been emphasized and expanded to include the development of a citizen advisory committee and a pubic process for the annual review and update of the SWM Plan(s). Citizen volunteers may also play a key role in future program implementation including water quality and habitat monitoring, as well as public education. • The establishment of a self-sustaining dedicated financial program has been developed and has been promoted that includes the development of a stormwater utility, as well as the hiring of a supervisor to help guide the continued development and implementation of the County's SWM Program. Mason County Belfair UGA Stormwater Management Plan 32 otak H:\project\30700\30784\Reports\Addendum\Final Text-OnlyES to Use\Final Text-ES-MK3-DNBelfair.doc Section 6—Future Public Involvement and Future Updates to the Plan 6.1 Ongoing Public Involvement The County has made the commitment to establish a SWM citizen advisory committee to help guide the development of the Countywide SWM Plan. It is expected that this group will continue to play an active role in the public review of the Countywide and Hoodsport SWM Plans, as well as in the annual updates to all of the County's SWM planning efforts which include future updates to the SWM Plans of Allyn and Belfair. 6.2 Future Updates to the SWM Plan The County recognizes the cooperative effort needed for successful and effective SWM planning throughout the County. It intends to conduct an annual review of the effectiveness of each of these proposed SWM Plans and their ability to be integrated into a comprehensive and effective countywide strategy and implementation plan Annual refinements to both the SWM Plan activities, as well as their associated budgets and associated service levels, are anticipated. This review and refinement will continue to occur through an open and well advertised public review process. Mason County Belfair UGA Stern/water Management Plan 33 atak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use \Final Text-JJS- K3-DNBelfair.doc References S. Glascoe and Beale H., Alberti, M., Bidwell, M., Christy, Aimee, May, C. 2006. New Approaches to Shellfish Protection in Puget Sound:: F-F ssential Strategies for Preserving Watersheds and WaterQuality for Shellfish Harvesting. A collaboration between the Puget Sound Action Team, University of Washington Urban Fcology Research Laboratory, Pacific Shellfish Institute, and Battelle Marine Science Laboratories Booth, D B 2000. Forest Cover, Impervious -Surface Area, and the Mitigation of Urbanisation Impacts in King County, Washington. Prepared for King County Water and Land Resources Division. Seattle, Washington. 18 pp. (available at http://depts.washington.edu/cuwrm/resea ch/forest.pdf) Booth, D B , D Hartley and R. Jackson. 2002. Forest Cover, Impervious -Surface Area, and the Mitigation of Stormwater Impacts. Journal of the American Water Resources. Association. 38(3):835 845. Glasoe, S. and A. Christy. 2004. T iterature Review And Analysis: Coastal Urbanisation And Microbial Contamination Of Shellfish Growing Areas Stuart Glasoe and Aimee Christy Puget Sound Action Team, State of Washington Olympia, Washington. Publication #PSAT04-09 Oakland Bay TMDL 2007. http //www.ecy.wa.gov/programs/wq/tmdl/oakland bay/index.html) Ecology 2001 Union River Fecal Coliform Bacteria Total Maximum Daily Load Study, October 2001, Publication No. 01-03-038. http://www.ecy.wa.gov/biblio/0103038.html Ecology 200?. Union River Fecal Coliform Water Clean-up Detailed Implementation Plan http. //www.ecy.wa.gov/biblio/0310066.html Washington State Conservation Commission (WSCC). 2003. Salmon Habitat T imiting Factors Water Resources Inventory Areas 15 (Nest), Kitsap Basin, and 14 (North), Kennedy-Goldborough Basin. Prepared by Michael Kuttle, Jr., Washington State Conservation Commission. (http: / / salmon.scc.wa.go/reports /wrial 4and15.pdf) WRIA 14. 2006 Watershed Management Plan Kennedy-Goldsborough Watershed, Final Unadopted Draft / May 2006 Prepared for the WRIA 14 Planning Unit under Grant G0000107 by Plateau Technical Communication Services) Mason County—Belfair UGA Stormzvater Management Plan 34 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text JJS-MK3-DNBelfair.doc References Continued WDOH. 2006a. Washington State Department Of Health Office Of Shellfish And Water Protection Annual GrowingArea Review forAnnas Bay. http: / /www.doh.wa.gov/ehp /sf/Pub s / gareports.pdf WDOH. 2006b. Washington State Department Of Health Office Of Shellfish And Water Protection Annual Growing Area Review for North Bay. http://www.doh.wa.gov/ehp/sf/Pubs/gareports.pdf WDOH. 2006c. Washington State Department Of Health Office Of Shellfish And Water Protection Annual Growing Area Review for Oakland Bay. http://www.doh.wa.gov/ehp/sf/Pubs/gareports pdf WDOH. 2006d. Washington State Department Of Health Office Of Shellfish And Water Protection Annual Growing Area Review for Pickering Passage. http://www.doh.wa.gov/ehp/sf/Pubs/gareports.pdf Mason County—Belfair UGA Stormwater Management Plan 35 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-VIK3-DNBelfair.doc Appendix A Appendix A— Water Quality, Fish, Shellfish and Habitat Report Introduction Water quality, shellfish, and freshwater and marine habitat conditions are vital water and natural resource issues in Mason County. This addendum to the Stormwater Management Plans for the cities of Belfair and Allyn includes detailed information regarding the status of existing conditions within Mason County as well as a summary of recommendations and on- going protection efforts for these areas of Puget Sound. This section of the amendment is organized to reflect the conditions of water resources in Mason County and, accordingly, is presented with a focus on Water Resource Inventory Area (WRIA) information. Because this region of Puget Sound is so rich in natural resources, there are many organizations (agencies, private companies, and citizens) that are actively working toward the protection of water quality and aquatic habitat. This summary is meant to encapsulate the existing conditions with regard to water quality and shellfish and salmon habitat Due to the broad scope of these issues and their importance to this region, the following review should only be considered a summary or overview of the present state of knowledge and the current activities underway to protect and enhance these regional resources. Mason County includes four separate Water Resource Inventory Areas (WRIAs) including WRIAs 14 (Kennedy-Goldsborough watershed), 15 (Kitsap watershed), 16 (Skokomish- Dosewallips watershed) and 22 (Lower Chehalis watershed), as shown in Figure 4-1. Nearly the entire watershed area of WRIA 14 lies within Mason County (or about 85%, approximately 207,872 acres of the watershed's 244,173 acres). The primary freshwater, marine, and nearshore habitats are within the northeastern portion of WRIA 14 and the western portion of WRIA 15. The western portion of WRIA 15 within Mason County contains only 80,953 acres, or approximately 13% of the 631,196 acres within the WRIA 15 watershed. The cities of Allyn is within WRIA 14, the Kennedy-Goldsborough watershed. The Allyn Urban Growth Area (UGA) is comprised of 1,167 acres in the watershed. Only a small portion of the WRIA 15 area, or about 2,328 acres, comprises the City of Belfair UGA. Although the areas within these two UGAs are relatively small compared to the watersheds, the natural resources located within each of these areas, associated with the North Bay area of southern Puget Sound and the lower end of Hood Canal, are considerable. The water quality, fish and shellfish conditions for WRIAs 14 and 15 are briefly described below. This review is presented according to the following topics: Mason County Stormwater Management Plan 1 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued Existing Conditions Existing Water Quality Conditions Existing Biological Resources Shellfish Salmonid/Fish Resources Monitoring, Protection, and Enhancement Mason County: Stormwater and Water Quality Belfair and Allyn Urban Growth Areas City of Allyn and North Bay Water Quality Shellfish Salmonid Habitat: Stream and Marine Nearshore City of Belfair and South Hood Canal Water Quality Shellfish Salmonid Habitat: Stream and Marine Nearshore Suggestions for Resource Management Stormwater Management / Watersheds Habitat Freshwater: Stream/Riverine Marine: Nearshore Habitats Mason County Stormwater Management Plan 2 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued Existing Conditions Existing Water Quality Conditions The quality of water in many of the WRIA 14 and 15 streams, lakes, and nearshore areas has been degraded, likely due to a combination of various land use activities including, stormwater runoff development of impervious surfaces, logging practices, wastewater from septic systems, and agricultural activities. The Union River and parts of Southern Hood Canal, Oakland Bay and Hammersley Inlet are on the most recent 303(d) list of impaired waters because of high fecal coliform bacteria and/or low stream temperatures. Water quality problems have lead to shellfish harvesting closures in several WRIA 14 and 15 areas in Mason County including Oakland Bay Hammersley Inlet, Pickering Passage, Annas Bay and Hood Canal Station tt9, as shown in Figure 4-1. These areas have been closed to shellfish harvesting because of high fecal coliform concentrations, and are considered as threatened shellfish growing areas by the Washington Department of Health (WDOH) (Figure 4-2). These closures have been linked to stormwater runoff and failing onsite sewage systems, and are threatening the shellfish industry. Ecology is currently working to set Total Maximum Daily Loads (TMDLs) for both nearshore and freshwater areas with observed water quality problems. These include the fecal coliform TMDL for the Union River that was written in 2001, and the fecal coliform and temperature TMDLs currently being developed for Oakland Bay. Existing Biological Resources Shellfish Mason County is an important shellfish rearing and harvesting region of Puget Sound. There are currently many areas for both the public and private harvest of a variety of species including oysters, dams, mussels and geoducks. Particular attention is being paid to the area near the Allyn UGA within North Bay, which contains the Olympia oyster the only native oyster species in the Washington State This species of oyster is currently a candidate species for state listing under the Washington State Endangered Species Act and is a species of concern under the federal Endangered Species Act (ESA). The shellfish resources throughout Puget Sound are being threatened by stormwater runoff, septic discharges, and other types of pollution. Many shellfish rearing and harvesting areas have been impacted. Some of the public and commercial harvesting areas are now decertified Mason County Stormwater Management Plan 3 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A -- Water Quality, Fish, Shellfish and Habitat Report Continued and others continue to be threatened by increasing development and its associated stormwater runoff. Within the Mason County area two shellfish protection/enhancement districts have been established. One within the Annas Bay area of Hood Canal and the other, covering a much larger geographic area, to restore shellfish resources within Oakland Bay. These shellfish areas are shown in Figure 3-1 as sensitive water quality areas. Salmonid/Fish Resources WRTA 14 streams and the Hood Canal nearshore habitat support a number of salmonid species. Unfortunately, the most productive habitats such as salt marshes, lagoons, and shallow bays have already been severely altered or lost within the nearshore areas of Mason County (Kugel, 2002). Summer and fall chum, coho, and chinook salmon, as well as steelhead and both anadromous and resident coastal cutthroat trout use the streams draining to and the neashore waters of Hood Canal. Of these species, Hood Canal summer chum salmon and Puget Sound Chinook were listed as threatened by the National Marine Fisheries Service under the ESA in March 1999. Forage fish such as surf smelt and sand lance, both important food species for anadromous salmonids, also use the nearshore. These species spawn near the high tide line on sand and gravel beaches found along the intertidal zone in Mason County. Within the Belfair drainage, the Union River and its associated tributary streams is especially important to the rearing and sustaining of many of the various salmonid populations listed above. Equally important is the Sherwood Creek watershed adjacent to the Allyn UGA, which currently also supports a variety of salmonid species. Both the Union River and Sherwood Creek systems and their salmonid resources are examined in greater detail in the following sections. Monitoring, Protection, and Enhancement To ensure that these resources are maintained, various regulations, programs, and monitoring efforts are in place to help protect and maintain ecosystem health. New regulations. have recently been established requiring Puget Sound health officers to designate Marine Recovery Areas (MRAs) where specific water quality problems have been identified. Under these new regulations, MRAs must be designated when the Mason County health officer determines off -site stormwater systems (OSS) are a significant factor contributing to concerns associated with the degradation of shellfish growing areas MRAs may also be designated when marine waters are listed by the Department of H cology (Ecology) for water Mason County S t o r m w a t e r Management Plan 4 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued quality degradation, including low dissolved oxygen levels, fecal coliform bacteria, or high nitrogen concentrations. Under these regulations, the 2006legislation directed the Mason County Department of Health Services and Mason County's health officer (as well as the other 11 Puget Sound counties) to take further actions to reduce fecal coliform bacteria pollution and the degradation and loss of marine life in Hood Canal and other marine waters in Puget Sound caused by low -dissolved oxygen conditions. It is envisioned that these MRAs will coordinate with existing TMDL and shellfish recovery districts, integrating action plans and correlating monitoring and data interpretation. Mason County Stormwater and Water Quality Within Mason County, the transformation or urbanization of landscapes from rural to urban land uses has resulted in an increase in impervious surfaces and associated stormwater runoff. During urbanization, forests are cleared and soils are stripped, compacted, and covered over with roads, buildings, and other impervious surfaces. Under this altered scenario, the precipitation that was previously taken up by native vegetation or that moved slowly into and through the soil layer as subsurface flow is now converted to surface overland flow. This results in changes in stormwater quantity and quality. Stormwater quantity is altered through the combination of reduced retention and enhanced conveyance, resulting in changes in seasonal runoff patterns such as lower stream baseflows in the summer, and more stormflow events with higher peak flows that rapidly rise and fall in the winter (Booth 2000). In 2004, the Puget Sound Action Team (PSAT) conducted a literature review of studies linking human modification of the natural landscape with direct and significant effects on the condition of aquatic ecosystems. Both streams and nearshore marine environments were evaluated, and the primary impacts included the fragmentation and loss of habitat, as well as the degradation of water resources and water quality (Glasoe and Christy 2004). One area that was identified as being especially sensitive to changes in stormwater runoff was the nearshore environment used to glow shellfish. The PSAT found that shellfish growing areas receive pollution along three main pathways: (1) direct discharges (sewage outfalls, boaters, marine mammals, etc.); (2) subsurface flows (shoreline onsite sewage systems); and (3) overland flows (stormwater runoff and stream flows) (Glasoe and Christy 2004). Mason County Stormwater Management Plan 5 otak H:\project\30700\30784\Reports\Addendum\Appendix A doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued The studies reviewed by the PSAT also documented high levels of selected pathogens in stormwater discharges. They determined that fecal coliform bacteria concentrations are influenced by several factors including rainfall, land uses, fecal pollution sources, and runoff potential of different surfaces and landscapes (Glasoe and Christy 2004). This is the same correlation identified by Ecology and WDOH, which observed a significant rise in fecal coliform concentrations during storm events within the Mason County UGA's. It has been shown that moderate levels of development within Puget Sound watersheds (10 to 25 percent impervious cover) degrade aquatic habitat quality, including shellfish growing areas, and the degradation increases as development intensifies (Booth 2000; May et al 1997). Low impact development (LID) strategies were identified in several studies in the literature review (Glasoe and Christy 2004) as the most effective means of minimizing the impacts of stormwater runoff rather than strictly relying only on structural BMPs LID strategies are being adopted by many jurisdictions in King, Snohomish, and Thurston Counties as an effective development strategy to minimize stormwater impacts. These same measures would also benefit Mason County in improving water quality conditions within both freshwater and marine environments. Belfair and Allyn Urban Growth Areas Water quality in and around both the Belfair and Allyn UGAs has been reported as degraded (see below for specific examples). Water quality degradation in these areas is associated with both marine and freshwater systems, and is a source of concern for shellfish harvest, salmonid and forage fish habitat, and recreational usage of aquatic resources. Currently, fecal coliform bacteria levels represent the primary contaminant of concern in both the Belfair and Allyn areas. City of Allyn and North Bay Water Quality The City of Allyn and the surrounding area comprise the watershed of North Bay (Figure 4- 3), and include important shellfish rearing areas, as well as habitat for salmon and forage fish. This area has a long history of marine water quality concerns stemming from runoff associated with both shoreline and upland sources; in particular on -site sewage system failures in the early '90s led to closure of many shellfish beds. Although the Allyn Wastewater Treatment Plant improved the marine water quality from failing septic systems Mason County Stormmater Management Plan 6 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued at the time, the area is currently showing a continued overall decline in water quality conditions, principally as a result of elevated fecal coliform levels and low dissolved oxygen concentrations. Both stormwater runoff and septic system discharges are thought to be some of the primary sources for these pollutants (i.e coliforms and nutrients), which are contributing to low dissolved oxygen concentrations within adjacent receiving waters. The North Bay area associated with the City of Allyn has been monitored by the Washington Department of Health (WDOH) for the past ten years (Figure 4-4) Data from the 2006 collection period indicates that several of the monitoring areas have been downgraded to a "threatened" status (stations #1, #7, and #575) or listed as areas "of concern" (stations #11, #12, and #548) due to water quality contamination associated with elevated fecal coliform bacterial levels. WDOH is currently investigating sources of contamination for North Bay. Stormwater runoff, currently untreated in the Allyn area, likely provides much of the non - point source pollution to marine nearshore areas (Kim Zabel, pers. comm.). Shellfish North Bay is considered a shellfish protection area by the WDOH and it is also on the Washington State Department of Ecology's (DO Ft) 303(d) list for fecal coliform bacteria contamination Additionally, the WDOH has prohibited shellfish harvesting along beaches immediately adjacent to Allyn to the southeast because of pollution concernst, and numerous other locations are either threatened or of concern due to elevated bacteria levels (see above). Areas designated as threatened or of concern by WDOH are based on assessments of threats to shellfish growing areas, and in the case of North Bay, these threats are based on bacterial sampling levels and standards established by the National Shellfish Sanitation Program (NSSP). Pickering Passage is located just to the south of North Bay, and marine water from Pickering Passage mixes with water in North Bay —thus, water quality conditions in Pickering Passage are directly related to water quality in North Bay. The WDOH summary shows that all water quahty monitoring stations in the approved portion of the shellfish growing area in Pickering Passage (with the exception of station -1157) pass the NSSP water quality standard(Figure 4- 5). Sampling station #57 fails the NSSP "approved" water quality standard, and the WDOH report also indicates that stations #52 and //58 are "threatened" and station #66 is "of concern ' due to elevated bacteria levels. Because the Pickering Passage area fails to meet the shellfish classification standards, WDOH recommends that a comprehensive evaluation be conducted to determine the appropriate classification for the area. Furthermore, WDOH recommends that a pollution Mason County Stormwater Management Plan 7 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A Water Quality, Fish, Shellfish and Habitat Report Continued source investigation should be initiated to identify and determine the source(s) of contamination to Pickering Passage. Salmonid Habitat: Stream and Marine Nearshore Stream Habitat: Salmonid habitat in the North Bay area consists of nearshore habitat in the bay as well as the stream habitat associated with Sherwood Creek, Anderson Creek, and Lake Anderson Sherwood Creek flows from Mason Lake into Case Inlet in the Puget Sound, and Anderson Creek confluences with Sherwood Creek to the southof Allyn The Washington Department of Fish and Wildlife identify Sherwood and Anderson Creeks as salmon -bearing streams, with several different species utilizing or potentially utilizing the in -stream habitat. Fall Chinook are documented as occurring in the lower portion of Sherwood Creek, and spawning habitat for coho salmon exists throughout the Sherwood and Anderson systems, with a documented presence of coho in several tributaries to both creeks. Spawning habitat for summer and fall chum exists in the Sherwood and Anderson Creek, and presence of fall and summer chum is either documented or presence is presumed in both creeks Winter steelhead are documented as occurring in the mainstem Sherwood Creek, and spawning habitat for this species is found in the Anderson Creek system. The outlet from Lake Anderson provides rearing habitat for both coho and winter steelhead. Marine Nearshore Habitat: Nearshore habitat associated with the Allyn UGA occurs along the western shoreline of North Bay. The nearshore habitat provides critical rearing and estuarine habitat for a variety of different species, in particular the salmonid species. Juvenile salmonids use nearshore habitats for several key life history functions. These habitats provide migration corridors, food production, and refuge from both predators and high- energy water waves (Mason 1970 Mac Donald et al. 1987; Thorpe 1994; Aitkin 1998). In addition, all salmonid juveniles utilize estuarine and nearshore environments to move from their natal stream out into the ocean Williams and Thom 2001). This is a physiologically complex transition and the estuarine environment provides a gradual transition for juveniles to adjust (Simenstad et al. 1982). The nearshore environment also contains marine vegetation associated with estuarine and nearshore marshes which provides shelter to rearing fish by protect juvenile salmon from turbulent wave action (Aitkin 1998). Nearshore habitat associated within North Bay and Case Inlet contains habitat associated with documented forage fish presence, eel grass beds, mudflats, and salt water marshes, and intact portions of the nearshore riparian zone. A high value estuary occurs at the mouth of Sherwood Creek. Salmonid species known to utilize this nearshore habitat include Chinook, coho, churn, sea -run cutthroat, steelhead, sockeye, and bull trout. Issues of concern in the Mason County Stormwater Management Plan 8 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued nearshore habitat associated with North Bay include water quality (fecal coliform, low DO, nitrogen loading, etc.), shoreline armoring, loss of nearshore riparian vegetation, and issues associated with stormwater and wastewater discharge. City of Belfair and South Hood Canal Water Quality Many of the marine water quality concerns described for the City of Allyn also pertain to the City of Belfair. The area of Hood Canal associated with Belfair is currently hsted as prohibited for shellfish harvesting by WDOH due to poor water quality The Mason County Department of Health Services is currently working with WDOH to increase sampling in the Belfair area, as well as to identify bacterial pollution sources within this area. In addition to the concerns in Hood Canal, water quality in the Union River is a concern. The Union River basin is located in a largely rural setting with few prominent urban areas or major point sources of pollution. Belfair, located near the mouth of the Union River, is the largest urban area in the basin (Figure 4-6). Increasing amounts of impervious surface in developed areas in and around Belfair may be decreasing groundwater recharge, increasing erosive storm flows, and directly delivering pollutants to the Union River. Recent storm sampling of streams draining the Belfair urban area show high bacteria concentrations in runoff (Ecology, 2003), and there is currently a TMDL and a water cleanup plan for the Union River for fecal coliform bacteria. Studies conducted as part of the TMDL indicate that dry season bacterial concentrations in the Union River are higher than those in the wet season, suggesting that there is a continuous, steady component to the pollution loading in the Union River. Since concentrations are relatively high during the wet season and flows are dramatically higher, there is also a storm -related component to the pollution loading. Pollution sources in the basin are exclusively non -point, and predominant sources are likely agriculture, onsite disposal (septic) systems, and post -development activities attributable to urban development (e.g., domesticated animals). Shellfish A portion of the Hood Canal 119 monitoring area is located adjacent to the City of Belfair (Figure 4-7), and the portion of this monitoring area impacted by Belfair is listed as prohibited for shellfish harvest. Pollution source identification and correction work is on- going in the area. Fifty-five acres of Belfair State Park tidelands were upgraded from Prohibited to Approved in 2006. However, extreme rainfall and storm water runoff resulted in emergency closures of the area from 1 /30/2006 to 2/4/2006 and from 11 /7/2006 to Mason County S t o r m w a t e r Management Plan 9 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued 11 /14/2006. The area was closed from 8/2/2006 to 9/28/2006 due to a naturally occurring marine pathogen. All stations in the "approved" portion of Hood Canal #9 meet the NSSP standard for an "approved" classification. The WDOH continues to assist Mason County in their pollution source identification work in the City of Belfair. Stimson and Little Mission Creeks and portions of the marine waters in Hood Canal #9 are currently on the 303(d) list for fecal coliform bacteria contamination. Salmonid Habitat. Stream and Marine Nearshore Stream Habitat: Salmonid habitat associated with Belfair UGA consists of nearshore habitat in the Hood Canal and stream habitat associated with Union River and its tributaries. Union River flows from Mason Lake into Case Inlet in the Puget Sound The Washington Department of Fish and Wildlife identify Union River as a salmon -bearing stream, with several different species utilizing or potentially utilizing the in -stream habitat. Fall Chinook are documented as occurring in the Union River, and spawning habitat for Chinook exists in much of the system, with rearing habitat for the species occurring in the lower Union system. Spawning and rearing habitat for coho exist in the system, and summer and fall chum are documented as occurring in tributaries to the Union River. Spawning and rearing habitat for winter run steelhead occur in the Union River, and there is a documented presence of winter steelhead through much of the system. Pink salmon are also documented as occurring in the Union River system. Nearshore Habitat: Similar to the nearshore habitat around Allyn, the nearshore habitat in the vicinity of the Belfair UGA has many of the same habitat features and functions. Saltwater marshes, tidal mudflats, and nearshore riparian habitat all occur in the Belfair area and all provide similar habitat functions and value to salmonids as noted above. Suggestions for Resource Management Management approaches that focus on preserving healthy ecological processes require a thoughtful and planned set of strategies to assess conditions, track changes incorporate new information, and redirect efforts over time to keep the system in balance. Here are a few suggested activities from the literature to help protect and restore watersheds and sensitive habitat areas within the Puget Sound basin. Mason County Stormwater Management Plan 10 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued Stormwater Management / Watersheds Booth et al. (2002) offered the following suggestions to minimize the impacts of stormwater: • Cluster developments that protect half or more of the forest cover, preferentially in headwater areas and around streams and wetlands to maintain intact buffers, • Allow a maximum of 20 percent total impervious area, and substantially less effective impervious area through widespread reinfiltration of stormwater • Provide onsite detention that is realistically designed to control flow durations (not just control peak flows), • Protect riparian buffer and wetland protection zones to minimize road and utility crossings as well s overall clearing, and • Do not allow any construction on steep or unstable slopes. Habitat The following is a summary from the Salmonid Habitat Limiting Factors Water Resource Inventory Areas 15 (West), Kitsap Basin and 14 (North), Kennedy-Goldsborough Basin http://salmon.scc.wa.gov/reports/wrial4andl5.pdf . Two sets of recommendations are presented for two different types of salmonid/fish habitat areas freshwater Stream/riverine and saltwater marine nearshore. Freshwater: Stream/Riverine The Technical Advisory Group for WRIA 1 makes the following recommendations to protect existing habitat and minimize further degradation of riverine habitat conditions: • Protect watershed conditions by preventing sprawling rural residential development. Encourage private forestland owners to continue timber production in a sustainable fashion that protects natural watershed functions (i.e. natural sediment production rates, natural runoff and stream flow regimes, mature riparian forests with coniferous trees, adequate large woody debris and pool abundance) • Protect functional riparian forest buffers to provide shade to maintain cool summer stream temperatures, provide large woody debris necessary to maintain instream salmonid habitat, and filter soil and pollutants from runoff. Where feasible, replant native riparian vegetation at degraded sites. • Protect functional floodplain habitat and where practical, restore lost floodplain habitat. Prevent further floodplain development Decommissioning of an old forest road and construction of a new access road on the lower portion of Anderson Creek is one example of a potential floodplain restoration project. Mason County Stormwater Management Plan 11 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued • Protect the shorelines of lakes, ponds and wetlands that maintain summer stream flows and provide rearing habitat for juvenile salmonids Where practical, restore degraded shorelines. • Maintain cool summer water temperatures and fish passage by preventing conversion of wetlands to shallow man-made lakes (for example Lake Symington and Lake Tahuya). • Remove fish passage barriers. • Minimize installation of impervious surfaces such as rooftops, roads, driveways, and lawns. Educate the public about the importance of minimizing impervious surfaces. • Monitor instream flows and water quality parameters including temperature and dissolved oxygen levels throughout west WRIA 15 and north WRIA 14. • Assess salmonid habitat conditions in the watersheds of the numerous small independent streams in the report area, particularly streams in the Port Gamble Subbasin and streams draining to the north shore (Tahuya-Dewatto and Union -Mission Subbasins) and south shore (North WRIA 14) of the east arm of Hood Canal. Marine: Nearshore Habitats The following recommendations are provided to address similar habitat concerns associated with marine nearshore habitat areas: • 1Hvaluate all road crossings along the Hood Canal shoreline to assess tidal function, sediment transport, and anadromous fish migration and where necessary, implement corrective actions to restore and/or enhance natural tidal processes, sediment transport, and anadromous fish access. • Allow eroding bluffs to function naturally to provide the sediment and large woody debris needed to maintain shoreline features such as beaches, spits, and lagoons, and shoreline habitat complexity. • Where practical, remove intertidal fill to restore/improve natural tidal and sediment transport processes. • Where practical, remove shoreline armoring or replace armor with alternatives including large woody debris and riparian plantings. • Prevent installation of intertidal fill and shoreline armoring, prevent removal of native riparian vegetation, and encourage landowners to install community boat ramps, docks, and piers rather than installing structures at each individual property. • Reduce impervious surfaces and impervious surfaces to reduce the impacts of high winter infiltration of precipitation. Mason County Stormnrater Management Plan 12 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc riSkokomish- Dosewallips (WRIA 16) nnas> COUNTY a-- , TTKitsap (WRIA'rt5) • BELFAIR URBAN GROWTH AREA flood Cana tatio ALLYN URBAN GROWTH AREA • • • • .• auto KI;TYAF- Legend • TMDL Areas • • e- Ca-U:N;TY Threatened Shellfish Growing Areas Within Mason County Streams Streets Railroad • WRIA Boundary 1_ _,I County Boundary UGA Boundary Figure 4-1 Mason County Wria Map 0 N s 2 4 Miles 411 North 5th, P.O. Box 279 Shelton, WasNngbn 98584 Phone: (360)427-9670 Fax: (360)429425 10230 NE Points Drive, Suite 400 Kirkland. WasNngbn 98033 Phone: (425) 822-4446 Fax. (425) 827-9577 K:/project/30700/30784/GIS/mxds/F(gure4_1 MasonWRlAMap.mxd 2007 Threatened Growing Areas Henith Shellfish 2 4 6 7 10 12 13 15 iCC#kYk 8 I 14 l I Sanrsh Soirib Dyes il}t2<LS North Buries Oakland Pickering Ltd Grays Bay wditselie Nahcotta duet' Pkkki'lk Inlet Center Inlet Skagit Ili}' Bay Bay Ilarbr Bay Lagoon .Bay Passage` 1'stktk I�3ay Bay -._�, .__._, .......... P5 -- "sue - S , _ s"` :.. r } f '. 7FE- oympra i LL= 2 '] S�' 1 = .3 Legend 1 �.1 " ;� 614yp , S 0 ' 76 r �= Shoreli .. VlaY a, (Pop r A P E+ereiz Kerrk b edmdrkd n £ �. _-i ._ fi _ - ......... mw t. t ,P, .i.o.an kd .A ro}L 5'<I M 41 , IIt It 11 F I 4 ty S ? ¢ x• FecYeraI Tacoma U$ 40,000) _""}.»ilttl@ h s e = Threatened Highways Counties Shoreine NamedCities m-‘ Areas >= 16 20 Growing G '10 '- liles 5 Threatened 4-2 Shellfish 0 1,500 3,000Feet 411 Shelton, Phone: Fax: ;, Nonh 5th, P.O. Box279 Wastngron 98584 (360)427-9670 (360)427-0425 C0 • 10230 NE Points Kirkland, Washington Phone: (425) Fax: (425) 6;11a Drive, Suite 400 98033 822-4946 827-9577 Figure 2007 AreasAreas © KJproject/30700/30784/GIS/mxds/Addendum/Figure4_2.mxd Legend Drainage Basin Divide Drainage Subbasin Streams Sherwood Devereaux Lake WEST DRAINAGE BASIN s 0 0 co 0 r Source: GIS data and Aerial photography provided by Mason County 2006. Washington State Department of Natural Resources provided Mason County with the stream data used in this report . Disclaimer: This map is not to survey accuracy and is meant for planning purposes only. Figure 4-3 Allyn Surface Drainages 0 1,500 3,000 Feet 411 North 5th, P.O. Box 279 Shelton, WasNngbn 98584 Phone: (360)427.9670 Fat: (360)4Z?-8425 10230 NE Points Drive, Suite 400 Kirkland, WasNngbn 98033 Phone: (425)82211A6 Fax: (425)8279577 K:/protect/30700/30784/GIS/mxds/Addend um/Figure4_3. mxd STATION LOCATIONS AND CLASSIFICATION B Figure 4-4 North Bay Shellfish Sampling Areas 0 1,500 3,000 Feet 411 North 5th, P.O. Box279 Shelton, WasNngbn 98584 Phone: (360) 427-9670 Fax: (360)427-8425 10230 NE Points Drove, Suite 400 K7xland, WasFington 98033 Phone: (425) 822-4446 Fax: (425)827.9577 Kiproject/30700/30784/G IS/mxds/Addend um/Figure4_4. mxd Figure 4-5 Pickering Passage Shellfish Sampling Areas 0 1,500 3,000 Feet 411 North 51h, P.O. Box 279 Shelton, Washington 98584 Phone. (360)427-9870 Far: (360)427-8425 10230 NE Points Drive, Suite 400 Kirkland, WasNngton 98033 Phone: (425) 822-4446 Fax: (425)8279577 K:/p roject/30700/30784/G IS/mxds/Addendum/Figure4_5. mxd Legend a Drainage Basin Divide Drainage Subbasin Streams ___ Streets —+—� Railroad Parcel Boundary ,r'Kitsap / (WRIA 15) ay1' / o° 'cod I /Kennedy- Goldsborough (WRIA 14)) I BELFAIR URBAN GROWTH AREA Union River Viola L'ree r'ibutrrry c Source: GIS data and Aerial photography provided by Mason County 2006. Washington State Department of Natural Resources provided Mason County with the stream data used in this report . Disclaimer: This map is not to survey accuracy and is meant for planning purposes only. Figure 4-6 Belfair Surface Drainages 0 1,500 3,000 Feet 411 North 601 P.O. Box 279 Shelton, WasNngbn 90584 Phone: (360)427-9670 Fac (360)427-8425 10230 NE Points rive, Suite 400 Kirkland, WasNngbn 90033 Phone: (425) 822-4446 Fax: (425) 827-9577 K:/p roj ect/30700/30784/GIS/mxds/Addendum/Fig u re4_6. mxd Figure 4-7 Hood Canal Station #9 Shellfish Sampling Areas 0 1,500 3,000 Feet 411 North 5th, P.O. Box279 Shelton, Washington 98584 Phone: (350)427-9670 Fax: (360)427-8425 10230 NE Points Drive, Suite 400 Kirkland, Washington 98033 Phone: (425) 822-4446 Fax: (425)827.9577 K:/p roj ect/30700/307 84/G I S/mxds/Addendum/F ig ure4_7. mxd • Mason County Update of County's Stormwater Policies/Regulations and Development of Comprehensive Stormwater Management Plans Belfair Urban Growth Area Stormwater Management Plan Submitted to: Mason County Department of Public Works 41 I N. Fifth Street Shelton, WA 98584 Submitted by: Otak, Inc. 10230 NE Points Drive Suite 400 Kirkland, WA 98033 Otak Project No. 30784 June, 2007 Transmittal Mason County Update of County's Stormwater Policies/Regulations and Development of Comprehensive Stormwater Management Plans Belfair Urban Growth Area Stormwater Management Plan Submitted to: Mason County Department of Public Works 411 N. Fifth Street Shelton, WA 98584 Prepared By Otak, Inc. Joe Simmler, Ph.D. Project Manager Larry Grimm, PE Project Engineer Laura Becker, EIT Engineering Designer Preface Belfair Urban Growth Area Stormwater Management Plan This document, entitled Belfair Urban Growth Area Stormwater Management Plan, has been prepared by Mason County in response to a request from the Western Washington Growth Management Hearings Board to enhance and provide additional information as to the need, cost, funding, and schedule for implementation of stormwater manageinent infrastructure improvements over the next six years within the Belfair Urban Growth Area of Mason County, as described in the County's 2005 Comprehensive Land Use Plan. The final Belfair UGA Stormwater Management Plan document will go through extensive local public review, consisting of public meeting(s), a public hearing, and review and approval by the County Board of Commissioners prior to its submittal to the State Boundary Review Board on August 6 2007. Public comments will be addressed and incorporated into this Plan, as appropriate. This is the initial draft of that document. Ala on CountyBe/fair VGA Stormwater ill a s a,g em e n i Plan otak Ji:AProject\30700\30784\Reports \liclfnir S\V\IP\Cover.doc Acknowledgements Mason County Update. of County's Stormwater Policies/Regulations and Development of Comprehensive Stormwater Management Plans Belfair Urban Growth Area Stormwater Management Plan Mason County Board of Commissioners Lynda Ring Erickson District 1 Tim Sheldon —District 2 Ross Gallagher —District 3 Mason County Department of Public Works Charlie Butros, PE, Director Mason County Department of Community Development Barbara Robinson, Director Mason County Department of Health Services Debbie Riley, RS, Environmental Health Manager Table of Contents Belfair Urban Growth Area Stormwater Management Plan Acknowledgements Executive Summary Section 1 Introduction I0 Section 2—Characterization of the Belfair UGA 16 Section 3 Existing Stormwater Facilities 27 Section 4—Future Conditions 30 Section 5—Stormwater Management Criteria 38 Section 6—Stormwater Concept Evaluations 43 Section 7—Stormwater Management Plans 58 Section 8 Costs, Schedule, and Implementation 67 Tables Table E-I—Belfair Stormwater Management Plan: Activities for 2-Year CIP Plan 8 Table 2 1—Hydrologic Soils Group 17 Table 2-2—UGA Streams and Classifications 19 Table 2-3— Existing .Drainage Basin Characteristics 21 Table 4 1 Existing and Future UGA Land Use 30 Table 4 2—Existing and Future UGA Land Use 32 Table 5 1 Minimum Stormwater Management Requirements 38 Table 6-1 Hydrologic Modeling Results 44 Table 6-2 Regional Stormwater Facility Screening Analysis 46 Table 6-3—UGA/SR 3 Joint Use Facility Evaluations 48 Table 6-4 Water Quality Treatment Retrofit Evaluations 50 Table 6-5 Summary of Subbasin Characteristics and Evaluations 53 Table 7 1 Recommended Stormwater Management Plans 60 Table 7-2—Belfair Stormwater Management Plan 63 Figures Figure E-1—Location Map 9 Figure I I —Location Map 15 Figure 2 I —Existing Drainage Basin Boundaries 22 Figure 2 2—Site Soils 23 Figure 2-3—Hydrologic Soil Groups 24 Figure 2-4—Critical Areas Steep Slopes 25 Al a s o n C o n Be/fair UGA Stormwater ,V a n a g e m e n t Plan TOC-i otak 1�:A project \30700\3i784\Reports \Belfair S\VMP\Coccr.doc Table of Contents Belfair Urban Growth Area—Stormwater Management Plan Figure 2-5—Critical Areas —Wetlands Figure 3 Figure 4 Figure 4 Figure 4 Figure 4- Figure 6- Figure 6- Figure 6- 26 -I—Existing Culverts 29 I—UGA Zoning 34 -2 Plan Concept 35 -3—Parks, Trails and Open Space Recommendations 36 4—Transportation Recommendations 37 I —Potential Regional and UGA/SR 3 Joint Stormwater Facility Sites 55 2—Existing Development Potential Retrofit Areas 56 3—Potential Fish Passage Enhancement Sites 57 Appendices Appendix A Low Impact Development Techniques Appendix B—Hydrologic Analysis Appendix C Construction Cost Estimates llaso n CoitnBe/fair UGA Stormwater Management P/an TOC-u otak K:A project \30700\30784\Reports \Brllair SW\IY\C:ovcr.doc Executive Summary Future Growth within the Belfair UGA The Belfair Urban Growth Area (UGA) is expected to continue to grow at a moderate rate over the next several years. According to the Comprehensive Plan, ultimate biiildout of the Belfair UGA will consist of 17 percent commercial, 69 percent residential and the remaining 14 percent as parks and open space. Currently, only about 7 percent of the residential land aiel and 10 percent of the commercial areas are developed, leaving 70 percent of the area to be developed over the next twenty or more years. With this conversion from undeveloped to residential developed areas, substantial stormwater management facilities will be required to support this land use change. Existing Drainage System The Belfair UGA contains about 2,314 acres (see Figure E-1). The topography of the UGA generall) slopes from east to west. Slopes range from flat (0 to 5 percent) to over 30 percent in the hills to the east of SR 3. Runoff in the northerly pait of the LTGA drains to the Union River by a series of small streams. The Union River toughly patallels the west side of the UGA and discharges to Hood Canal. Runoff in southerly portion of the UGA discharges directly to Hood Canal, either as streamflow or as diffused subsurface flow. See Figure E-1 Existing drainage facilities within the LTGA are primarily associated with SR 3 county roads and commercial development adjacent to SR 3 These facilities consist of toad culverts, roadside ditches, onsite water quality and infiltration systems. They complement and work in concert with the streams and subsurface flow throughout the UGA. Fish presence has been documented in many of the streams. Some of the newer commercial developments have onsite water quality and flow controls. However, the majority of the commercial developments are older and release their stormwater runoff untreated and undetained. The stormwater runoff from residential areas is also primarily untreated and undetained. The current level of development in most of the residential areas is low so much of the stormwater is infiltrated or is collected and conveyed by ditch/culvert systems, or drains directly into the numerous local creeks. Approximately half of the UGA is associated with Group A soils (which readily infiltrate stormwater) and half is associated with Group C soils (« hich infiltrate very little). There are numerous wetlands throughout the UGA. The Group A soils promote the infiltration of runoff. In these areas, infiltration has been use as the preferred method of storm\t ater disposal. In general no capacity or flooding problems have been reported within the Belfair UGA except where Mindy Creek crosses SR 3 near Mitchell Lumber. ill is s o n CO/ I 11 ty Be/fair LTGA S t o rm wa t e r Management P/a n 1 otak K:Aproject\30700\30784\Reports\Bdfair S\VNIP\BclfnirS\VNIP.doc Executive Summary Continued Belfair UGA Stormwater Management Plan Stormwater management strategies including both management activities and capital improvement projects (CIPs) for the Belfair UGA have been identified and are proposed for implementation in the following Belfair UGA Stormwater Management Plan. Costs and priorities for implementation have been identified for both the short-term (three year planning period) as well as future ultimate development over the next twenty years, as shown m Table E-1 Each element of the Belfair Stormwater IVlanagement Plan is described below. Activity #I: Adopt Ecology 2005 Manual (Using Existing County Staff) • Develop and adopt an ordinance requiring the use of the Ecology 2005 Manual for all new development -within the Belfair UGA. Activity #2. Establish Dedicated Stormwater Funding for Belfair UGA (Using Existing County Staff) • Develop and implement a dedicated funding mechanism to support stormwater management activities and capital improvements within the Belfair UGA. Activity #3. Adopt Low Impact Development (LID) Ordinance (Using Existing County Staff) • Complete the development and processing of the county -wide LID ordinance. Activity #4. Coordinate with WSDOT Regarding the Relocation of Mindy Creek (as a part of the SR 3 Project) (Using Existing County Staff) • Coordinate with WSDOT on the relocation of Mindy Creek on the east and west sides of SR 3 and the installation of a fish -friendly culvert under SR 3 relative to the stream habitat enhancement objectives of the Belfair UGA Activity #5: Coordinate with WSDOT on Streetscape Improvements (as a part of the SR 3 Project) (Using Existing County Staff) • Coordinate with \X/SDOT on streetscape unpiovements ul areas where right-of-way width may allow water quality facilities (rain gardens, etc.) to be included for treatment of existing impervious areas. Activity #6. Coordination with WSDOT on SR 3 (Using Existing County Staff) • Coordinate with WSDOT to establish the feasibility of joint -use stormwater facilities at proposed SR 3 stormwater treatment and detention sites. The Belfair interest in these AI ason Count is Be/fair VGA Siormwater A'Ianagemeni Plan' 2 otak Imo:Aproject\30700\30784\Reports\Bcllair S\V'\IP\13dfairS\VNIP.doc Executive Summary Continued facilities would be primarily for water quality retrofit purposes and/or to support new future commercial development along the SR 3 corridor. `liming of development with respect to construction of the WSDOT facilities may affect the feasibility of these potential joint -use facilities. Activity #7. Prepare Low Impact Development and Property Owner Water Quality Brochures (Using Existing County Staff) • Prepare and distribute of a brochure describing low impact development techniques for onsite detention and water quality treatment and a. brochure describing actions residential and coininercial property owners can take to improve the quality of stormwatcr being discharged from their properties. Activity #8: Perform Baseline Habitat and Water Quality Study for Belfair UGA Streams • This study would inventory the habitat of the existing streams within the Belfair UGA. It would also involve water quality testing on each stream to determine if problems exist. Any identified problems would be addressed during the implementation of the Belfair Stormwater Management Plan and Comprehensive Plan. Activity #9: Coordinate with Mason County Transportation Department to Incorporate LID and Water Quality Benefits into Transportation Improvements (Using Existing County Staff) • Coordinate with the Mason County Transpoitation Department to incorporate LID and water quality benefits into transportation improvements (sidewalks and landscaping), as identified in the UGA Comprehensive Plan (along Old Belfair Highway). Activity #I0. Coordinate with Mason County Parks Department to Incorporate LID and Water Quality Benefits into Planned Park Improvements (Using Existing County Staff) • Coordinate with Mason County Parks Department to incorporate LID and water quality benefits into park improvements, as identified in the L GA Comprehensive Plan. Activity #1 1: Develop and Conduct a Public Information Program to Promote Public Water Quality Awareness for Private Properties (Using Existing County Staff) • Once the brochures of Activity- 1/7 are available, two or three public informational meetings would be held in Belfair to educate residential and commercial property owners on storm\\ ater pollution and encourage their participation in enhancing the quality of water reaching the Union River and Hood Canal. Mason CoBelfair UGA Stornater Management Plan 3 otak K: Ap, ojcct\30700\30784\Reports\Bel fair \V?dp\Bclfairs\VNrP.doc Executive Summary Continued Activity #I2. Conduct Sweetwater Creek Fish Passage Improvements Study • Conduct a fish passage improvement investigation for Sweetwater Creek. Develop options and costs to eliminate vertical drop fish barrier associated with the water wheel. This activity would start after confirmation from the baseline habitat study (Activity #8) that areas above the water wheel would support fish. The study would include coordination with WDFW on passage design options and a project cost estimate. Activity #I 3. Prepare Belfair Creek Fish Passage Improvements Study • Conduct a fish passage improvement study for Belfair Creek from the east side of SR 3 to the existing active stream west of the commercial area. The stud.) would include an alternatives analysis for stream location, accommodation of existing commercial uses, preparation of preliminary plans, coordination with WDFW and preparation of a project cost estimate. Activity #I4. Develop Cooperative Commercial Water Quality Retrofit Program (Using Existing County Staff) • Develop a cooperative program between Mason County and existing commercial - industrial property owners to retrofit existing commercial areas for water quality treatment, where problems have been identified (in Activity #8), to improve the quality o f stormwater being discharged to the Union River and Hood Canal. A cost sharing formula would be developed as pact of the program with Mason County financing part o f the improvement costs and the property owner financing the rest. Most of the commercial areas adjacent to SR 3 are underlain by Hydrologic Soil Group A soils which generally support infiltration. Retrofitting possibilities for individual commercial - properties include infiltration of roof runoff, collection and pretreatment of road and parking area runoff in rain gardens or fillet catch basins, followed by infiltration and treatment within the soil matrix. Long-term activities (4 — 20 years) include two potential CIP project as outlined below. Activity #I5: CIP No. I-Belfair Creek Relocation and Fish Passage Improvements • Perform final design, right-of-way/property acquisition and construction of the Belfair Creek relocation and fish passage improvement project defined by Activity 1/ 13. Activity #I6. CIP No. 2 Sweetwater Creek Fish Passage Improvements • If this project is determined viable based on the investigation of Activity 1112, perform final design, right-of-way/propeity acquisition and construction of the S\Veet\\ ater Creek fish passage improvement project defined by Activity /112. Mason 6'o as n Be/fa r U G./l S i o rrn wca t e r Al a n ag e>n e n 1 Plan 4 otak K:Aproject\30700\30784\Reports \lBelfair SWi'IP\l3eIfairS\V\IP.doc Executive Summary Continued Stormwater Management Strategies In addition to the management activities and projects discussed above, stormwater • management strategies have been developed for the entire UGA and are presented by subbasin to reflect the soils, existing development, zoning and other characteristics unique to each subbasin. The strategies identify reconunended stormwater approaches to meet the Ecology 2005 Manual requirements for new development and ultimate buildout. Strategies are presented in the Belfair Urban Growth Aiea Stormwater Management Plan. It is anticipated that stormwater improvements associated with new development will be designed, constructed and funded by private developers. Therefore those facilities have not been included in the Belfair CIP program. Costs and Implementation It is likely that the biggest challenge facing the County in the development and implementation of the Belfair Stormwater Management Plan will be the development of the needed revenue within the required timeframe. Implementation Priorities and Schedule Determine Revenue Needs Although difficult to predict, an attempt has been made to identify the priority and tuning of future activities and capital projects in order that future revenue needs can be established. Total costs over the t' enty year capital planning period are estimated to be $1.7M. For this analysis, the twenty year planning period has been divided into two planning periods of 3 and 17 years respectively as shown below. Note that future water quality problems may increase County expenditures under Activity #14, the cooperative water quality ietrofit program. This financial plan would then need to be updated to include the forecasted funding requirements to enhance water quality. Potential Sources of Funding At this point in time, the County is unsure how they will raise the funds needed to support and implement this proposed Stormwatei Management Plan for the Belfair UGA. There are several financial options being considered. These considerations have led to the conclusion that multiple sources of funding may be needed. Funding sources that are currently being considered include: Al a.r o n C o ern tJ —Belfair VGA S t o r m ma / e r AI a n a<gem e n t Plan, 5 otak I<:AProject\30700\30784\Reports \BclfairS\vivIP\BclfairS\VNIP.doc Executive Summary Continued • Formation of a T .ocal Drainage/Stormwater Improvement District, which would have an annual assessment often based on assessed property value, or some other equitable means of establishing value and/or benefit to the various rate payers. • Real _Estate Excise Tax (RI;F,T) funding, which currently amounts to about $1M per year, and is currently being used to pay for a number of capital projects throughout the County. • Public Sector Funding, such as grants and low interest loans from the State (Ecology or the Puget Sound Action Team) or federal government, including federal 319 Water Quality Grants, and the State Public Works Trust Fund and State Revolving Fund. • Formation of a Stormwater Utility (County -wide), where a monthly service fee is assessed to rate payers, often based on the amount of impervious area per parcel, and an incremental portion could be allocated back to the rate payers within the Belfair UGA. • System Development Charges, where any person moving into an upstream drainage area would be required to pay for a portion of the downstream collection, conveyance, detention, treatment, and outfall facilities that may be needed to support continued development within the drainage basin. • SEPA ivtitigation Funds, which would be established on a per development basis, as a project enters and is ultimately approved through the State SEPA review process. • Partnering with prospective developers and land owners, which is especially effective in establishing funding for larger regional drainage facilities. • Other potential, but less likely sources of funding, include: - The County General Find - The County Road .Fiend - Cost Sharing with WSDOT • .,Any potential future road, park, or utility project could also include some funding for making localized drainage improvements, as defined in 'advance though this stormwater planning process. From this list of eleven potential sources of funding, the most likely sources of new future funding in relative order of priority are the following: 1. SLPA mitigation funding. 2. Periodic appropriations from REETI funding. 3. Public sector funding (grants and loans). 4. Annual stipends from a Belfair or county -wide stormwater utility 5. Partial, periodic funding from future road, park, or utility projects. 6. Partnering with developers. It is difficult to estimate how much revenue could be raised by each of these preferred potential funding sources, over what period of time, in order to support the above Ala s o n C o it n Belfair UGA S i o r m w a r e r M a n a g e m e n i Plan 6 otak K:AProject\30700\30784\Reports \ Bel lnir S\C'1IP\Bell/ tirS\V'iAIP.doc Executive Summary Continued annualized Financial Plan. However, being primarily driven by future growth, it is recommended that es cry effort be made to optimize the amount of new revenue from prospective developers, and then augment the remaining funding needed from REE T and pubhc sector funding, as opportunities allow. Future partnering with developers, landowners and WSDOT should assist the County in sharing these regional growth related costs and maintaining the steady, continuous development of the drainage infiasttucture needed to support growth throughout the Belfair UGA. 11a.con Co tnfyy—Bel/arr UGA Siormwater Management Plan 7 otak K:AProject\30700\30784\Reports\I3eIfair SW\IP\]3clfairSWMP.doc Long Term 4-20 Years X X Short Term I -3 Years M X X X X X X X X X X X IN X X X X X X X - X X X X X X Funding Source 1 07 c c c 1.5. w i WSDOT Future Grant Future Grant Future Grant Future Grant To Be Determined To Be Determined Future Grant Future Grant Future Grant Future Grant To Be Determined To Be I Determined 0 0 U 4-20 $ 1,500,000 To Be Determined $ 1,500,000 M — County Staff County Staff or consultant W G or County Staff jjms :(lung:) G County Staff .-- _ ` r _ County Staff In — i n County Staff $ 200,000 Priority High .0 01 = .0 .0 07 High 0 01 = Medium High 0) 0 S .0 0) S Medium High High Low Low Low 07 S = Supporting Agency Mason Co. Mason Co. Mason Co. HCSEG Mason Co. Transportatio n Mason Co. Parks HCSEG HCSEG WSDOT tble I L n-- Lead Agency Mason Co. Mason Co. Mason Co. WSDOT WSDOT WSDOT Mason Co. Mason Co. 6 0 c 0 0 m 2 Mason Co. Mason Co. Mason Co. Mason Co. Mason Co. Mason Co. Mason Co. • 3 4J U Q Activity #1:Adopt Ecology 2005 Manual 'Activity #3: Adopt Low Impact Development Ordinance rrB o+n ,Af th \Arenn-r nn rnlnrc.+irn nf nninr+„ rrooU ne, r,,r+ rt auv I on atreetscape improvements for water ect Activity #6: Coordinate with WSDOT on joint -use stormwater facilities as part of the SR 3 project Activity #7: Prepare Low Impact Development and Property Owners Guide to Stormwater Pollution Control Brochures Activity #8: Perform baseline habitat and water quality study for Belfair UGA streams Activity #9: Coordinate with Mason Co. Trasportation Department to incorporate LID and WQ benefits into transportation improvements as identified in the UGA Plan. Activity #10: Coordinate with Mason Co. Parks Department to incorporate LID and WQ benefits into planned park locations as identified in the UGA Plan. Activity #11: Develop and conduct public information program to promote water quality awareness for private properties Activity #12: Perform Sweetwater Creek Fish Passage Improvements Study Activity #14: Develop cooperative commercial water quality retrofit program with cost sharing provisions crovements Activity # Io: uir No, z — aweetwater ureeK rlsn passage improvements tir found feasible by Activity #9) Total ($1,700,000 + Grants) dicated stormwater fundinn Activity #13: Perform Belfair Creek Fish Passag 0. O C7 c 0 0 0 O c C W c O E O as 0 D O O 'U W U) 0 K:\project\30700\30784\Reports\Belfair SWMP\BelfairSWMPTables7.xls amm Drainage Basin Divide Drainage Subbasin Streams Streets Tributar v To Coulter Creek Figure E-1 Location Map Belfair Stormwater Management Plan 0 1,500 3,000 Feet 411 tt'c,• SzczNzi Pak 1]2312 NE o;a5 E.e. <.y., <p;. K..,'n'i Eai. 224 z12E1E2I--iii? KJproject/30700/30784/GIS/mxds/Belfair/Figures/ArcGIS9.2/LocationMapVer2.mxd Section I —Introduction Background Comprehensive land use planning by Mason County has resulted in establishing the Belfair community as an Urban Growth Area (UGA). Other UGAs established by the County include the communities of Allyn and Hoodsport and the City of Shelton. This report provides the Stormwater Management Plan (SWMP) to support development within the Belfair UGA. The Belfair UGA is located northeast of the City of Shelton, southwest of Bremerton, and east of Hood Canal, as shown in Figure 1-1. The Belfair UGA includes a mix of existing residential, light industrial and commercial areas. The residential development is generally located away from State Route 3 (SR 3) which bisects the UGA. Light industrial development is located principally in the northerly part of the UGA along either side of SR 3. Commercial development is concentrated along east and west sides of SR 3 in the southerly part of the UGA. The proposed zoning for Belfair generally follows the existing land use patterns. Stormwater management for the UGA will need to address both existing development with vehicular pollution generating surfaces and as well as runoff from future development. The majority of runoff from the Belfair UGA drains to Hood Canal, either directly or indirectly via a series of six streams that discharge into the Union River or Hood Canal. From north to south the streams include: Viola, Irene, Belfair, Mindy, Sweetwater and .Alder Creeks. A significant portion of the region's discharge is conveyed into the Union River and Hood Canal as subsurface flow. Photo I —SR 300 Crossing the Union River ill a n o n C o it n -- B e l f a i r L- G A ,S' f o r m m a t e r Al a n a J,7 e m e n i Plan 10 otak IN:Aprt,jcet\30700\. Jt84\Repots\RcltairSV NJP\ReIEairS\6'\IP.de Section 1—Introduction Continued \Xtater quality issues associated with both existing and future land use are a key element of this Stormwater Management Plan. Hood Canal's marine ecosystem is at risk because of low levels of dissolved oxygen as well as nutrient, sediment, and other pollutant loadings. The Puget Sound Action Team has suggested that the dissolved oxygen problem is the result of three factors that play a significant role including: • Poor overall water circulation. • Stratification of water that discourages mixing of surface -to -deeper water. • Increased input of human -influenced nutrients materials (especially nitrogen) that cause rich plankton and algae blooms, which proliferate, add oxygen to surface waters, then die and sink to the bottom where they decompose and use up oxygen in the process. The Hood Canal Dissolved Oxygen Program (HCDOP), which is a partnership of 38 organizations including Mason County, is actively addressing the low dissolved oxygen issue in Hood Canal. HCDOP has two integrated and. complementary arms: the Corrective Action and Education Group and the Integrated Assessment and Modeling (IAM) study. The HCDOP has a number of projects underway in a variety of areas including education and involvement, sewage management, stormwater management and hatchenT management. In the area of stormwater management, one of the HCDOP 2006-2007 projects is to complete stormwater management plans for both Belfair and Hoodsport. Washington State Department of Ecology has issued a grant to Mason County to help fund the preparation of these two plans. This report provides the stormwater management plan for the Belfair area, as defined in the County's Comprehensive Plan. Al a s on Con Photo 2 Public Education Poster Posted Near the Union River 13eljair t7CA Stormwater Management Ilan 11 otak ]::Apro cct\30700\3078-I\Reports\flclfair S\X'NP\Bcll;urti\\'\iP_t.Ioc Section I —Introduction Continued Purpose and Scope The purpose of this report is to develop the Stormwater Management Plan (SWMP) for the community of Belfair, Mason Count), Washington, in response to the stormwater element of the 2006 Belfair Urban Growth. Area (UGA) Comprehensive Plan. The scope of this Stormwater Management Plan includes: 1. Characterization of existing stormwater conditions within the Belfair UGA. 2. An estimate of future conditions based on zoning defined in the County's 2005 Comprehensive Plan. 3. Hydrologic modeling and engineering analyses to determine the size and location of facilities needed to accoinmodate existing and future growth. 4. Development of an appropriate stormwater strategy to address existing and future development needs, as tailored to the specific characteristics of the study aiea. 5. Presentation of the proposed Belfair Stormwater Management Plan, including proposed projects and activities, costs, piiorities, permitting, financing, and implementation considerations over a three and twenty year planning period Authorization This study has been authorized by the Mason County Board of Commissioners and is being jointly initiated by the Departments of Public Works and Community Development. The Mason Count) Department of Health Services has also been invited to participate. The development of the Belfair UGA Stormwater Management Plan has been funded in part by a grant to Mason County by the Washington State Department of Bcolog) along With a local match from Mason County. This study is part of a larger stormwater and regulatory compliance planning effort currently being undertaken by the County entitled' Update o f Connty'.r Storimvater Policies/IZeplations and Development of Complehoisive StormwaterManagement Plan Ibr Mason Collllty cwd the Communities of .13e/f iir, .Allyn, and .l oodiport. This larger county -wide stoup\eater management planning program is expected to be completed by the end of 2007 and includes the development of stormwater management plans for the County and the areas of Allyn, Belfair and Hoodsport. It also includes the development of updated design criteria, policies, and funding mechanisms foi stormwater management throughout the County. Mason CountBe/fair LTG Stormmater Man at emeni Plan 12 otalc K:Aproject \30700\30784\Reports\Bclfaii S\V vIP\BcllairS\V/\IP.doc Section I —Introduction Continued Regulatory Requirements This Stormwater Management Plan has been prepared to be consistent with the requirements set forth in the Ecology 2005 Stormwater Management Manual for Western Washington and existing Mason County codes and regulations. These design criteria are also consistent with the 2000 Puget Sound Water Quality Management Plan and the 2005-2007 Conservation Plan Update. Additional discussion of the design criteria used to develop the Belfair Storinnvater Management Plan is presented in Section 5. Stormwater Planning Approach The Belfair UGA contains varying soils, slopes and land uses, all of which influence stormwater management. Management methodologies to meet iegulatoiy requirements include land use and zoning controls to guide individual development, joint -use opportunities (with proposed SR 3 storm facilities), coordination with local salmon and «titer quality groups and the tribes, approaches to retrofit and mitigate existing development, and area-wide/regional stormwater facilities as opportunities allow. The approach taken in developing this Stormwater Management Plan has been to analyze and develop stormwater plans on a subbasin or wateished basis. The existing characteristics of each subbasin in terms of size, soils, slopes, and land use were initially quantified using GIS methods Information available on stream systems was the reviewed to identify those streams that are fish bearing, including those that may have fish barriers. Future zoning impervious areas were then quantified for each subbasin by GIS methods \Z7ith this information including an inventor) of existing facilities alternative methods of stormwater management within individual subbasins were developed and evaluated. Alternative methods were screened based on the feasibility for future development, joint- use, retrofit and area-wide/regional facility type solutions. From the screening analyses, recommended stormwater management projects and activities were developed for each subbasin. From this list of proposed stormy, ater management initiatives, both short-term and long-term CIP programs were prepared. Report Content and Organization The Belfair UGA Stormwater Management Plan is presented as a series of discrete sections that generally follow the flow of work culminating in the piesentation of recommended activities, capital projects and costs. The report is composed of the following eight sections: Alason Corantr UGA Stormn'cater Aianagement Plan 13 otak K:Aproject\30700\30784\Reports\13elfair S\V71ATP\BelfairS\VNIP.doc • Section 1 • Section 2 ® Section 3 ® Section ® Section 5 ® Section 6 Section I —Introduction Continued documents the goals and authorization for the study. characterizes the Belfair UGA study area. describes existing facilities and problems. analyzes future conditions needed to support ultimate development. outlines regulatory mandated design criteria. conducts modeling and performs engineering analyses to support existing and future/ultimate development. • Section 7 presents the iecommended SWM Plan for the Belfair UGA. • Section 8 lists priorities, and presents costs and funding sources for implementation. Stormwater Management Planning Activities in Study Area Two stormwater related planning activities have been recently completed that impact stormwater management planning within the Belfair UGA study area. In Match 2005, Perteet, Inc. completed the "Belfair Urban Improvements Project Feasibility Report" for Mason County. Technical Memorandum 4 of that report addresses stormwater management for Highway SR 3. It identifies alternatives for stormwater treatment and detention of the runoff from the proposed SR 3 widening and improvements. In general, while there are some opportunities for joint -use stormwater management facilities bet een the County and WSDOT, tuning, funding and local development of and/or redevelopment opportunities will determine their cost-effectiveness and practicality. In May 2006, Engineering Services Associates completed the "Lower Union River Stormwater Study" for the Hood Canal Salmon Enhancement Gioup, Mason County and Mason County Conservation District. This stud) was funded by the Department of Ecology in 2003 as part of the Lower Union River Restoration Study. The study states that 'a major part of the project was to monitor, study, and develop a plan to reduce or eliminate pollution from storm water drainages in the Belfair Urban Growth Area (UGA)." (i.e., existing development). Currently , the Washington State Department of Transportation (WSDOT) is planning the SR 3 Belfaii Bypass project. The proposal is to construct a high-speed bypass \\ith limited access on the east side of the Belfair UGA: Its purpose is to relieve congestion in the communit\ of Belfair by re-routing through traffic. Stormwater management facilities for the bypass project ill be designed, constructed and operated by WSDO f, Opportunities to include them as potential regional stormwater facilities to also accept existing and future stormwater runoff have been considered in the development of the Belfair SWI\1h Plan. Ala son County—Belfair I'GA Stormwater Management Plan 14 otak K:\project\307(1(i\307$ 4\Reports\Belfair S\E MI) \ Beni rS\Vt\1V.Joc Drainage Basin Divide Drainage Subbasin Streams Streets } Railroad Figure 1-1 Location. Map Belfair Stormwater Management Plan 0 1,500 3,000 Feet 411 `l-f `t-i.?O. 8> 214 _n .. _ 54 •.-ti?. !?3 422i- li F‘. a —.]; 427E42E KJprotect/30700/30784/GIS/mxds/Belfa it/Figures/ArcG IS9.2/LocationMapVer2.mxd Section 2—Characterization of the Belfair UGA Existing conditions relating to stormwater management in the Belfair UGA are described in this section They include a review of the topography of the stud) area, -along with the drainage basins, soils and land cover as they affect runoff, streams and receiving waters and the presence of fish. Topography and Drainage Basins The Belfair UGA contains about 2,314 acres. The UGA is about 2.9 miles in distance north to south and averages about 1.3 miles wide east to west. The topography of the UGA generally slopes from east to west. Slopes range from flat (0 to 5 percent) to over 30 percent in the hills to the east of SR 3. Runoff in the northerly part of the UGA chains to the Union River by a series of small streams. The Union River toughly parallels the west side of the UGA and discharges to Hood Canal. Runoff in southerly portion of the UGA discharges directly to Hood Canal, eithei as streamflow or as diffused subsurface flow. A total of 19 drainage subbasins have been delineated within the Belfair LTGA as shown in Figure 2-1, together with directions of flow and 100-foot contours. SR 3 provides the westerly boundary for subbasins in the easterly pait of the UGA. The Union River and the Hood Canal shoreline provide the w esterly boundary for subbasins located along the west side of SR 3. Portions of these subbasins are located west of the westerly UGA boundary. There are areas outside the UGA that are tributary to the UGA from the north, east and south, as shown in Figure 2-1. The magnitude of these areas is not large in comparison to size of the UGA and it subbasins. In the easterly part of the UGA there are a few smaller subbasins which dram to the east rather than to Union River or Hood Canal. These areas drain principally to Coulter Creek and 1 ider Lake. Soils The soils within the Belfair UGA, as mapped by the Natural Resources Conservation Service (NRCS), formed). the U.S. Soil Conservation Service (SCS), are shown in Figure 2-2. To facilitate runoff calculations and hydrologic planning, soils are assigned to one of four hydrologic soil groups b) the NRCS based on their infiltration capabilities of the soil as shown in Table 2-1 Mason Counts-13e/fair UGA S/o rviwa/er Al ana4en/ent Plan 16 otak K:A project \30700\30784\Reports \Belfair S\V v1P\13eliairS\v\IP.doc Section 2—Characterization of the Belfair UGA Continued 2-1 Soil Groups Table Hydrologic Soil Group Infiltration Area Within (ac) UGA Percent area of (%) UGA Characteristic A High for aggregated deep infiltration, sand silts or low runoff, loess, as 1,150 50% B Moderate moderately such as sandy infiltration, coarse loam -textured as for soils 3 0.1 C Slow textured shallow organic infiltration sandy content soil such loan, as as for clay soils fine- loam, low in 1,038 45% D Very swelling slow infiltration and plastic claypan such as 117 5% The distribution of soils v ithin the UGA by their hydrologic soil group is shown in Figure 2- 3. Approximately half of the UGA is associated with Group A soils and half associated with Group C soils. There are minor areas of Group B and Group D soils in the UGA. Group A and B soils which are generally located in the lower, flatter areas of the UGA, promote infiltration of runoff. In these areas, infiltration would be the preferred method of stoimwater disposal. Group C and D soils, located in the upland areas of the study area do not have much infiltration capacity and, as a result, constructed stormwater facilities will be needed to support development in these areas. Sensitive Areas Sensitive areas include steep slopes (areas with slopes of 15 percent or more), hydric soils, wetlands, and geologic hazards, which include landslide, seismic and erosion hazards. (Refer to Mason County Draft 2006 Critical Area Update for hazard area criteria). Critical areas within the UGA (as provided in the shape files obtained from Mason County) are delineated in Figures 2-4 and 2-5. Areas exist within the Belfair UGA, especially within Subbasins 10 through $0 that have land with slopes exceeding 15 percent. The steeper slopes will tend to reduce the ultimate development potential of those properties. Steep slopes are shown on Figure 2-4. Al a so n Count] B e l Jai r L? GA S /o rni za'a t e r zV a iz as e rrz e as / Pla 11 17 otak K:Aproject\30700\3t17S4\Reports\13clfan S\VN1P\Ben fairs\V%11P.doc Section 2 Characterization of the Belfair UGA Continued There are numerous wetlands throughout the UGA. Over half of Subbasin 100 is defined as wetlands by The National Wetlands Inventory (NWI). Elsewhere in the UGA, isolated. wetlands are present particularly in the northern part of the UGA west of SR 3. Wetlands are shown on Figure 2-5. Photo 3-Wetland on Irene Creek; east side of Old Belfair Highway Sensitive areas pose constraints on development in terms of setbacks and mitigation requirements. These constraints will need to be addressed by future development. Fish Bearing Streams and Receiving Waters Streams located within the UGA are described in Table 2-3 and graphically shown in Figures 2-4 and 2-5. The permanent water type classification is taken from the Washington Department of Natural Resources (WDNR). The receiving water for each water course is also provided. The WDNR classification definitions are provided below. 'I`ipe Fish Type "S" Shorelines Type "Np" Non -Fish Perennial Type "Ns" Non -Fish Seasonal Letter "N"—Non-Fish Letter Unknown Al a so n Co II n Cy BelfairL' GS/ o rm iNa t e r Al a u a em e u/ P /a a 18 otak ,project \ .30700 \ 30784 \ Rep \ Bel fair S\\%UP\Bella irS\V':V P.doc Section 2—Characterization of the Belfair UGA Continued As the non -fish UGA streams have not been differentiated as "Np" or "Ns" by WDNR, "N" has been used for non -fish streams. UGA Streams and 2-2 Classifications Table Subbasin ID Water Course WDNR Water Receiving Water* Type # 10 Unnamed Drainage U HC Course 20 Alder Creek F HC 30 Sweetwater Creek F FTC 40 Unnamed Course Drainage U I IC 50 Mind) Creek F" IIC 60 Unnamed Course Drainage U HC 70 Belfair Creek F UR 80 Unnamed Course Drainage U UR 90 Unnamed Course Drainage U CD 100 Cieek / Wetland N HC 110 Belfair Creek -N UR 120 Irene Creek U UR 130 Unnamed Course Drainage U UR 140 viola Creek N UR 150 Unnamed Drainage U CD Course 160 Unnamed Course Drainage U UR 200 Unnamed Course Drainage U CC 210 Unnamed Course Drainage U CC 770 Unnamed Drainage U LL Course tHC=I Iood Canal, UR= Union River, Cat Closed Depression, CC— Coulter Creek LL= Lider Lake '''"West of SR 3 only As may be noted, four streams have been classified as fish bearing by the WDNR. These include Alder Cieek, Sweetwater Creek, Mindy Creek and Belfair Creek. The streams Mason Co»rrBe/fair UGA Sform») ter Ala na1gement Pl-an 19 otak li:Aproject \30700\30784\Reports\Bella ir S\V\IP\Bella irS\P\IP.doc Section 2—Characterization of the Belfair UGA Continued classified as Unknown should be investigated further to determine if they are fish bearing. It is likely that all streams within the Belfair UGA are available to fish. Some stranding with existing barriers has been noted in this study. Photo 4—Belfair Creek, east of SR 3 Land Use The majority of land within the Belfair UGA is currently dedicated to low -density residential and forested areas. Commercial uses are located principally adjacent to SR 3. Industrial uses are present within the UGA and are primarily located to the northeast in Subbasins 90, 140, 150 and 160. Details of existing land use by subbasin are provided in Section 4. Existing Drainage Basin Characteristics Summary The existing characteristics of the Belfair UG1 subbasins are summarized in Table 2-3. These include stream and receiving area information, subbasin areas including both total and area within the UGA, hydrologic soil group areas, and topographic slope information This information has been used in part to develop stormwater management strategies for each subbasin, as presented in Section 6. fVlorson Conn1_j'— Belfair LC A Siormilwaler _llanagemen/ Plan 20 ota k Is: lroject\30700\30784\Reports\Belfair S\V\1P\IiclfairS\VNIP.doc Range of topograp _ Lil I Q ud 0 r 1 83.2 COC) N 19.5 0 ri N r II) - to LC)d ) oi 00 65.7 ' 4 N 122.0 V N. 95.0 50.5 137.7 56.4 54.21 O) cci 1106.2 N O ONE' Lfl 6 o\° v 0 0 0 O 0 r 0 0) 0 0 f� o 0 0 N .- 0 0 0) 0 N r 0 0 O) r 0 0 N 0 C r 0 O 0 0 r r 0 0 N 0 N 0 0 d- r 0 0 O r 0 o r� r p 00 v N r tf) N N O) r 8.6 V 5.0 N 6 d- CO r r 25.9 20.7 d' r 47.8 CO r CO N CO r 6 r 54.51 15.0 CO r t- r CO N "I"CO h co 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 o 0 0 %0'0 p 0 0 -. O 0 0 o 0 0 r- 0 0 O 0 0 o 0 0 0 0 0.0% 0.0% -. 0 0 0 0 0 0 0 u rd o O 0.0'. 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 6 1.8 0 O 0 o 0.01 0.01 0.0 0.0 0.01 CO o 0 o 0 0 0 p 0 0 O p 0 � 0 O 0.0%°I p 0 O O o 0 O O 0 0 tf) r 0 0 0 O 0.0% 0 0 m O V 0 0 co O) N 0 0 co O) 0 0 O O 0 0 CO 0) 0 0 O O 0 0 r V 0 0 O O 0 O o 0 0 0 0 0 r to (ac) 0.0 0 O 0.0 0.0 0 O 0.0 N to O O 0.0 to v in N r 24.5 0.01 18.51 0 O C7 r. r 0.01 O O 0.0 117.4 1 0 e O O O O %L'OI. O O to ct CO O O to N O O O En C) O r C) O O I� O O p0 49.5% O O Cn O O O C71 C�) 38.7% O O Co 4 0) O O R of O O co. LC) p O N co N O O O LC) O) O O N R C) O O 0) O CA 44.8%f 'rid.-O cis 0 CO 4 O T r �' 6 N 7 cm N N 241.0 CO O 72.7 0 r 13.4 C) O 14.8 CO N 50.51 N N. 101.3 44.3 10.21 CO o m o 0 O O 0 0 O 0 o O 0 Ca O 0 O 0 0 o 0 0 O 0 0 CO 0„., O O 0 O O 0 N r 0 0 O 8e, N to p N 0 o O O %9'0 0 O 0 0 O O 0 O O o r O (ac) o O 0.0 O 0 0.0 0.0 0.0 0.0 o O 0.0 O 0 cc) O r O O) O 0.4 o O IC-. r 0.0 O O O O N N Q O O O r 2)90 CO O co t) t() co LO CO N. O 0 o O O 0) O O) 1 O N oOO 6 r CA Ycl- N O - r N: CO O CO _O t Q 0 OO Lf) O N. O ct O - O N O O OO 0 o O 0) CO OO 0 OnOO O ) Nt (ac) 16.5 N 6 co ct to co CO 4O CO _ V LC) CO CO C CO CO N N to U) d- LC) 15.7 134.9 0.01 148.21 CON W V CO r COr tO r N O O N 0 Subbasin Area 000 s. ,.+ as CC HC HC HC HC 0 2 HC CC D UR CD HC CC D __ D UR UR CD CC Z CC CC LL I i i e Qa D U. LL D D LL LL. D D Z Z O D D D D D D 1 Z Water Unnamed Drainage Course Alder Creek Sweetwater Creek U nnamed Drainage Course Romance Hill Drainage Mindy Creek Belfair Creek U nnamed Drainage Course Creek / Wetland •Belfair Creek Irene Creek U nnamed Drainage Course Viola Creek U nnamed Drainage Course Jnnamed Drainage U nnamed Drainage I Course U nnamed I Cow it it Downstream of UGA2 0 \o 0 o \0 0 0 0 \0 0 0 o 0 0 0 d \0 0 0 o \0 0 0 0 \o 0 0 0 \0 0 o o 0.0%. \0 0 rn a) r` d \0 0 rn o \o 0 m tri r 22.1 \° 0 Ci \0 0 0 0 \o 0 r` 0 r \o 0 o 0 \ 0 O 0 \0 0 0 0 .--- 0 0 0.0 O O O O O O 0.0 O O O 6 0.0 O O 156.7 CO N 49.9 72.3 N O r 0 O m 4 co 0.01 0.0 0.0 O) 6u co Upstream of UGA1 o 0 0 O 0 0 6? CO CO %O'0 0 0 O 0 0 0 O 0 0 O 0 0 CO r 0 0 0 O 0 0 (.0 C) N 0.0% 0 0 0 O 0 0 0 O 0 0 0 O 0 0 O 0 0 N O 0 0 V RO N 0 0 I%0'0 0 0 0 6 0 0 O ID"r al 35.8 0.0 0.0 O O O O N W 0.0 r O 0.0 0 O 0 O 0.0 0.0 00 O 121.0 0 O 0.0 O O 0 N d Q o 0 r O 0 r r 0 0 6 0 r et o co N 0 0 M 0 to 4 rD 0 ct 6 o C) CO a co d- o co r 0 d-. r 0 r 6 0 d- CO 0 Ch 4 0 a r r 0 O 4 0 r 66 0 '4 0 0 r 0 N -J %4) J J 0 0 0 0) O 0 0 0 C O O N O. d) 0 'D C) N C p. O H 0 ro a)• ir U c o O CLI II ra cc D LL 0) C S c0) O 0 0 o O = CC 11 IT t Z 3 O o a N r c 0 0 cis 0 N sc. 0 .G) N - _ N ) 150 T c UN o 0 n v) O C Q CO LL Z A i-' PI). CO LL Z m GIS data and Aerial photography from Mason 2006. Disclaimer: This map is not to survey cy and is meant for planning purposes only. NE MCKNIGHTRD ON BLVD ;ENE"GARRICK l'N Lit :t, 5 to 15% t,15to30% I Pit la, 0 to 5% la, 5 to 15% ON!BCVO Ne - Norma, 0 to 3% Oa - Orcas, 0 to 2% Sa - Saxon, 5 to 15% Tb - Tanwax, 0 to 2% Tn -Tidal Marsh W - Water Legend Soil Boundary Line --► Drainage Direction Drainage Subbasin Boundary and No. 100 Ft Contour County Boundary Saturated Soil eologic Soil B C D US data and Aerial photography from Mason )06. Disclaimer: This map is not to survey and is meant for planning purposes only. pr `PPPr Prt " , 14.•?;,,M, irrirrpryrrro:, pr-rr rr-pt, rerPrr- sprti.r. ,'rrr.PPr;rrtr„pf:;r3pit " r 4,7 :ream 'known Brcentage 5% - 30% 30% tream Buffer 3IS data and Aerial photography from Mason 006. Disclaimer: This map is not to survey and is meant for planning purposes only. NE FERN ON NEBELLLFAI,RT Alder°Creek NE,NEWKIRK,R NE MCKNIGHT"RD Roance D ainage W 3m sown > data and Aerial photography from Mason 6. Disclaimer: This map is not to survey id is meant for planning purposes only. NE TIMA RD ERN VD PSSG REMC PFOA E2EMN PEMAH P_,SSCH PEMCH E2EMP POWHH:PSSC e. UfRE,LN NEBELFAIR ST E NEWKIRK,R NE GARRICKiLN PSSC Tributary Coulter NWI Wetland Descriptions E2AB/USN - Estuarine, Intertidal, Aquatic Bed/Unconsolidated Shore E2EM/USN - Estuarine, Intertidal, Emergent/Unconsolidate Shore, R E2EMN - Estuarine, Intertidal, Emergent, Regularly Flooded E2EMP- Estuarine, Intertidal, Emergent, Irregrularly Flooded PABH - Palustrine, Aquatic Bed, Permanently Flooded PEMAH - Palustrine, Emergent PEMC - Palustrine, Emergent, Seasonally Flooded Section 3-4---Existing Stormwater Facilities Existing drainage facilities within the UGA are primarily associated with SR 3, county roads and commercial development adjacent to SR 3. These facilities consist of road culverts, roadside ditches, onsite water quality and infiltration systems. These elements of the Belfait drainage system are described in this Section. They complement and work in concert with the natural elements of the drainage system characterized in the preceding section. Roadway Culverts The location and size of the 22 existing culverts crossing SR 3 and NE Old Belfair Highway are shown in Figure 3-1. They vary in size from 12 to 54 inches in diameter. Typically roadside ditches collect road and adjacent property runoff and convey it to the culverts. Some portions of SR 3 north of the intersection with NE Old Belfair Road have catch basin and cross pipe systems instead of roadside ditches. No capacity problems have been reported by WSDOT or Mason County with these culverts except where Mindy Creek crosses SR 3 near Mitchell Lumber. Mindy Creek flows into an 18-inch corrugated metal pipe that is connected to a piped collection system for SR 3. This system crosses SR 3 and goes under the Mitchell Lumber yard before it daylights again. In discussing this system with the County, it was noted that this system, if not maintained, can become clogged with debris which has resulted in localized flooding in the past. Photo 5 Mindy Creek crosses SR 3 near Mitchell Lumber 17 arson Co u n l J----Belfair U GA S to rnr nma t e r Al a s a,g errr e a t P /a rr otak 1<:AIxojca \307UO\ 30784\Reports\Bel Fair SvVN \I3d fairs\V ? 1 P.doc Section 3—Existing Stormwater Facilities Continued Private Drainage Systems Within the commercial areas and residential developments, there are both public and private storm drainage facilities. Some of the newer commercial developments, such as the QFC grocery store and the car wash for example, have onsite \vatei quality and flow controls. However, the majority of the commercial developments are older and release their stormwater runoff untreated and undetained. The stormwater runoff from residential areas is also primarily untreated and undetained The current level of development in most of the residential areas is low so much of the stormwater is infiltrated, or is collected and conveyed by ditch/culvert systems, or drains directly into the numerous local creeks. Some of the newer residential developments provide onsite water quality treatment and detention. The development on top of Romance l-lill Road has its own stormwater facility located on the east side of SR 3. This system provides for «ater quality treatment and infiltration of treated stormwater. Mason Corrnt—BelJair UGA Stormwater A'ianagemenl Plan 28 otak Imo:Aproject\30700\30784\Reports\Bellair SVV\IP\BclfairSVV\IP.doc County Boundary : GIS data and Aerial photography from Mason 2006. Disclaimer: This map is not to survey :y and is meant for planning purposes only. 7reneCreek ON'BLVD liutaryyTo ultere Ere W 2 Section 4—Future Conditions Future conditions relating to stortnwater management within the Belfair UGA are described in this section. These are defined by future zoning as presented in the Belfair Comprehensive Plan (2005) and its associated land use cover criteria. Belfair Comprehensive Land Use Plan The Belfair Comprehensive Plan includes proposed future zoning for the Belfair UGA. The proposed zoning is shown in Figure 4-1. Future land use cover assumptions for the proposed zoning range from 35 to 90 percent impervious area, as shown in Table 4 1. Approximately 17 percent of the Belfair UGA is currently developed. Existing and 4-1 UGA Land Use Table Future UGA Land % Impervious % Pasture % Grass Zoning Uses LTA 2 98 0 R-3 35 0 65 R-5 40 0 60 R-10 50 0 50 B-I 85 0 15 FR 85 0 15 GC 85 0 15 GC-BI 85 0 15 MU 85 0 15 ROW 90 0 10 Zoning Classifications ROW Right of way B-I Business Industrial FR Festival Retail GC General Commercial GC-BI General Commercial & Business Industrial LTA Long 1 erm Agricultural MU Mixed Use R-10 Multi Family Residential R-3 Single Family Residential R-5 Medium Density Residential _4 - defined by Ma COun7/)' Pla/1nznj Deparimeni Alas on Con n/y Belfair UGA Stormnwater 11Ianagemeuf Plan 30 otak K:Aprojcc\30700\30784\Reports \ Bel fair SW1\1P\13clfairS\V\IP.doc Section 4—Future Conditions Continued Future Drainage Basin Characteristics Summary Existing land uses within the UGA, along with the future land uses defined by the proposed zoning, are shown in Table 4-1 for each subbasin. As may be noted from Table 4-2, approximately 69 percent of the UGA will be dedicated to residential land uses as compared to about seven percent in the existing condition. Also, approximately 17 percent of the UGA will be dedicated commercial -industrial uses as compared to about ten percent in the existing condition. The future residential development of 69 percent reflects conversion of much of the existing undeveloped areas in the UGA, which currently amount to 83 percent of the UGA area. With this conversion from undeveloped to residential developed areas, substantial stormwater management facilities will be required to support this land use change. Coordination with Belfair Comprehensive Plan In addition to the zoning discussed above, The Belfair Urban Growth Area Plan outlines strategic concepts for the future land use in the Belfair UGA. The three strategic concepts addressed in this section are: intense development centers, expanding the parks, trails, open space and public facilities, and recommended transportation improvements. Each of these concepts has opportunities for being integrated into a cohesive regional drainage system that protects natural functions as well as enhances the water quality of Hood Canal. The first strategic concept focuses more intense development in three commercial centers along SR 3. This concept is shown in Figure 4 2, Plan Concept (Belfair Urban Growth Area Plan). Dense development centers present numerous opportunities for shared and/or regional stormwater facilities. Partnering, including the sharing of costs, may occur among developers, and/or with the County. The second strategic concept expands the parks, trails, open space and public facilities throughout the UGA. This concept is shown m Figure 4-3, Parks, Trails, Open Space, and Public Facility (Belfair Urban Growth Area Plan). Proposed paiks also present opportunities for shared use and regional facilities such as enhanced stream buffets through the parks, and/or water features that could also beincorporated into future stormwater facilities. Shared use opportunities are discussed further in Section 6. The third strategic concept proposed transportation improvements throughout the UGA.. This concept is shown in Figure 4-4, Transportation Recommendations (Belfau: Urban Mason Coant)—Belfair UGA tlManagerneni Plan 31 otak K:Aproject\30700\30784\Reports\Belfair S\VN1P\13c]fairS\V \1Y.doc County Proposed Zoning Within UGA R-3 o v.=N 7 N N 0 M C5oc6 co 7 r ui r oc0oLri N co 0 O) 0 CO o ri o 0 0 27.• re V N .-- O) N r c0 0 N Cr) CO N CO N N 6) 4 O CO W r O O 28.9 O O Cr) N O) CD U) r CO 6 N 6 N V' N O O CD 6 O p if M O MU o o M co 0 O 6 0 co 07 0 N N co 0 N N 0 V 0 N 0 N 4 0 O r 0 O O 0 co N CO 0 co O_ r. 0 c0 -r-- %0'0 0 O O 0 O O 0'0 0 co O 0.0% 0 O O 0 O a) u .`o. 0 OD N M o O 0 6 Cr) co M r 14.0 N O r V N O O 7 COV O co) O M O . O O . O O el 0 co 6 O 6 O O O) Q O Q 00 0 0 0 0 0 0 0 0 06 0 0 0 0 O 0 0 O 0.0% 0 0 6 0 0 0 0 0 0 %0'0 0 6 0 O O •0 N 4 0 O O o O 6 0.0% a 0 O 0 O O 0 N O J n 0 0 0 0 0 0 CD 6 O 0.0 0 O 0 6 0 O 0 O 0'0 8.2 0 0 r 0) O 6 O 6 O O CD O O CO N E6 0o 0 0 . O 0 0 O 0 0 O 0 0 6 0 O O 0 0 O 0 0 O 0 0) co 0 U) O 0 O O 0 O O 0 N M 0 O 0 0 U) 0 0 M 6 0 o 0 O 0 O O 0 0 6 0 O O 0 d' V' U O .A. O O O O O O O O O O O O r O CV r 0 oi 0 O 0 O 8.4 O O O N r N 6 co O 6 O 6 co O O O N O U v 0 000 o00 0 0 0 0 0 0 oo0) 000 0 0 0 N 0 0 • v0v,o aidN4 0 0 0 0 0 O0 60 0 0 0 6 0.0% 0 0 0 0 0 0 0 0 oUi 0 CO 0 u re 0 . O 0 . O 0 O 0 6 0 O 0.0 3.0 N N r V O O O O r co 10 O r 0 O 0.0 O 6 O 6 O 6 O 6 O O co O) N K o 0 O O 0 O O 0 O O 0 O O 0 0 O 0 0 O 0 0 O 0 O O 0 0 O 0 0 O 0 N 03 co 0 N O 0 O O 0 O O ....tit O 6 0 0 6 0 O 6 0 0 6 0 O O 0 CO O LL t O ._ O O O O O 0 O O 6 0.0 0 O C. O O O O O r O r 0 N O O O O 0 6 0 O O 6 O O O . O_ co Zit) 0 0 0 O O 0 O O 0 O O 0 0 0 0 0 06 0 0 %O.0 0 0000 O 0 O 0 O 0 O 0 O 0 0 r 0 0 CO 0) 0 c0 N 0 O O 0 0 O 0 O 0 0 co O 0 Ci co O O O O O O 0 O O O 0.0 0.0 0 O 0 O 0 O 0 O 0.0 O O CO T U) m 0 O 0 6 N O p. N ROW C142 0 O V 0 M 6 0 O 66 0 (. 0 0 N 0 0 M 0 N V 0 0 O) 0 ( 4 0 N V 0 O) O 0 N O 0 NO C 0 O) 67 0 O 0 O 4 o 0 6 a O 6 o 0 O 0 O O co N O r N 00 O r l0 M N N r N CO U) r M r Cr) O N [t CO <t CO N r N O V r r U) V co N O O O 6 0 O O a) Q Undeveloped 000 N o CO N O O) N O O) 0 CO 4 N 000 0) M CO NO N N N N O) 0 O O CO 0000 N O CO D) (.0 O co• CO N CO 57.4°% 87.4% 43.4% 0 0 N N 0 0 O O r 0 0 O O r 0 LC) • O (D 0 N CO a R LO r r CO ai M a) N 0 CO 6 N O) O V N M O r a) N CO M 6 r 0) M CO r N N 0 V r 0 M CV O o) V O O V' M C' CO a) a)O) 106.60 N co O 1925.6 Industrial 0 000 O 0 O 0 O 06 0 0 000 0 O 0 O 0 O 0 N r 0000 N N 0 O 0 O 0 M 00 O O O 4 0 O O 0 0 d' 6 0 O 6 0 O 6 0 O D) co N O co 0 0 0 0 0 0 0 O 0 0 0 0 0 0 N N U) 0 r O 0 O 0 'd' Oi 0 O 0) ai O ai co N ai N 0 O 0 6 d' O V N O N Commercial 000 0 d' O O 0 co O 000 -N O Vr CO c-U a CO 6 000. O O) O r N N U) Lo N 00 O O N N 0 O O 0 O O 0 0 O a 0 6 0 0 O 00a ac) CO r 0.2 0 O Cr) O 0) U) 0 O r -7713 O) N r 0 O 17.6 Cr) 04 N CO . 0 O r O 0 O O O O O O O O O N M Section 4—Future Conditions Continued Growth Area Plan). For some of these recommendations, such as the SR 3 widening improvements and the alternative North/South bypass, WSDOT is the lead agency and preliminary plans have already been developed Such projects may present partnering opportunities between the County and WSDOT. For other transportation related drainage opportunities, such as Old Belfair Highway sidewalk and landscape improvements, the County is the lead agency and is planning on considering Low Impact Development water quality treatment of road runoff as a part of these improvements. These three strategic concepts were considered during the development of this stormwater plan and are addressed further in Section 6 of this document in developing, evaluating, and suggesting drainage facilities to compliment and support continued development throughout the region. Mason Corrnlp—Be/fair UGA Slormwaler Alanagement P/an 33 otak K:\project\3(1700\3(1784\Reports\13clfair S\VNIP\l3clfairS\V\IP.doc ouear�i 31S data and Aerial photography from Mason D06. Disclaimer: This map is not to survey and is meant for planning purposes only. v ur cc m J DESCRIPTION Business Industrial Festival Retail General Commercial 'General Commercial & Business Industria Long Term Agricultural Mixed Use Multi Family Residential_ ;Single Family Residential Medium Density Residential )NiBLVD NE'A�DER CREEK LN ., z derCreek Plan Concept 1. Fucus murc *iivcrne intense development in Three centers: 1 t C?Ih end to attanv�debe lays r9c1y ntCt1.1Th1&ttial * L.Wort»T1 :es pmvlde nw of pnlosk ixn..r.r„e,! i a uq •,rjhr am rittuayrnptranl • Sahli))) eente Ic ant:haat:0 clucatonel mei` rWCwattanal ,authtiles 2. Upgrade SE-3 co • earpttt 4.1Nbf Gnrticl: • Ir?aal !rwnr 111111ml log pedeilris Ord 95te*/ i t pic.ltrocra) • Cn:4Jt pz aterethe r Mgt! for 3 trSrr;llb+_t N) tb$otti route re. quality tiring And ist, rat cnvironmcnt • hots wslar rr.iatry tnn9Dr on • btu a n:m ritrvttk tr2^rtri 1r41 eti ti nra 1 11166Nt surd natural G.Iaracm * coined antiaeapc.Y nepttbcdluojs xx�h trctia, reek• !tnd poblie ^.ar. e• air Sub -Area Piau l Figure 4-2 Plan Concept Belfair Stormwater Management Plan K:/project/30700/30784/G IS/mxds/Belfair/Figures/ArcG IS9.2/LocationMapVer2.mxd Parks, Trails, Open Space, and Public Facility Recommendations amass 'It A ."-treamccnidcrs aid 'Hnliand rraas Iaererehris l bsnt craj i±t:q ronoar 'eccuruw FnFosv1 P&L rr prnad rar$t Prvrowtd rnsacnal xall kNrOYifit ball I1todaIl wallanrJtrnI r,s{arn Prop xsd w.elk,n. 113II IV) rcbFluat) IkrIB Ped ltra't rriendy siretiscap s Fapmnd fl ozw; candor - 7n:1 wanner, prninciinn dew Expand Ilse s;stem nr 1r llls a€Aflcaled with rtke rteler b'eefist ds Expand ub +: Iat -k, c nic r and cr�klEne:lti protection Add Irrfroved acreas at bodge is this lorAi .sail - C011n0ck d :rail ptilteau , r ' teal HIIIFdctes -t lcighbernoed Par< B -Ifair Sub Create walkways and Die'/des tacilibes along - the tall-u corridor -Ntinhbcwhcod P,y-k ;turn of trio Plan Figure 4-3 Parks, Trails" Open Space, and Public Facility Recommendations E3elfa'r Stormwater Management Plan P b 2? :li: rt, --`9b^tis tii K:/project/30700/30784/GIS/mxds/Belfair/Figures/ArcGIS9.2/LocationMapVer2.mxd Transpo ti©n Rec©mm ndatians • • • • 1-5: Truck access improvements along SR-3 on the plateau T-4: Provide traffic calming and ',. entry improvements along SR-3 T-9: Connect existing roads in conjunction with rew development T-7: Signalize intersection T-8: Provide Old • Qelfair Highway/ (Main Street) improvements between SR-3 and Clifton Lane T-3: Provide safety improvertten SR 3/SR 300 Intersection T-9: Develop local access Roads in conjunction with rew development T-1: Upgrade SR-3 to three - lane configuration and enhance bicycle and pedestrian access T-2: Provide safety improvements at SR 3/SR-1 06 intersection T-6: Develop an alternative North/South bypass route on the plateau T-4: Provide traffic calming and entry improvements along SR-3 ilfair Sub -Area Plan 9 --�--_ • Figure 4-4 Transportation Recommendations Belfair Stormwater Management Plan sr. r .t5cPO Ba.1'f wS�n�PemfsO. F. _ e..> Fa( Kaprotect/30700/30784/GIS/mxds/Belfair/Figures/ArcG IS9.2/LocationMapVer2.mxd Section 5—Stormwater Management Criteria The current Mason County stormwater requirements are based on Ecology's 1992 Stormwater Management Manual for the Puget Sound For this study, the 2005 Ecology Stormwater Management Manual for Western Washington (Ecology 2005 M'inual) has been used to help protect water quality and habitat of I-Iood Canal and the Union River. The use of the 2005 Ecology Manual also reflects a condition in the grant from E~ cology to Mason County for continuing this stormwater planning `,work. The following summarizes the stonnwater management criteria for Belfair. In addition to the Ecology 2005 Manual, this section also recommends the use of Low Impact Development (LID) techniques (currently under development by the County), in conjunction with the continued use of the County's new small parcel stormwater management requirements for low density residential development. Minimum Stormwater Management Requirements The regulatory requirements for stormwater management are contained in the Ecology 2005 Manual and in the various Mason County codes and regulations. The Ecology 2005 Manual sets foith ten minimum iequirements for stormwater management that arc required for development and redevelopment These are listed in Table 5-1 and have been used throughout the development of the Belfair Stormwater Management Plan. All stormwater plans must demonstrate compliance with these applicable minimum requirements. (The full text of the minimum requirements should be referred to for a complete understanding of the requirements and when and how they ale to be applied.) Ecology 2005 Manual: Minimum 5-1 Management Requirements Table Stormwater 1 Preparation 2005Manual/ of Stormwatei shall prepareaStormmetter Site Plans - All Site projects meeting the thre.Jholds [outlined in the Ecology Plan far local government review. 2 Construction Stormwater new plus replaced impervious surfaces more of land midst prepcne a COnstructi0n Pollution total Prevention 2,000 S1J2TP (S\VPP) square leet Plan a part 07' - Projects in rvhicb the new, replaced, or more, or disturb 7,000 sglnar e f eet or of the Dom/water Site Plan. 3 Source Control .Practices (BMP.r) of shall Pollution be -All selected, designed, known, available and reasonable source control Best Management and maintained according to [the Ecology 2005 Manual/. =1 Preservation maintained, practicable. adver:re dissipation. dirchaws manlier d0wnstream I\atural by jr Drainage Systems and om the project site shall which nmolf is discharged receiving waters and dwn Outfalls caw at fr0m igr adietlt the the -Natural drainage natural location, project site nmst properties. .All patterns shall be to the maximum extent not cause sgnlficant outfal%r require energy of and Then luipact t0 Ala.ron Count,—Be1/air UGA Stormwater ilianagement Plan 38 K_Aproject\30700\30784\Reports\Belt-air S\\%'SIP\13elfairS\VN1]'.doc otalc Section 5— Stormwater Management Criteria Continued 5 On -site Stormwater to infiltrate, disperse, and flooding or erosion impacts. Management — Projects .should employ' On -Site Siorlmvater Management retain .rtorllmater runoff on.rite to the maximum extent feasible .BMPs without causing 6 Runoff discharge prohibited, through 'Treatment use — [Many stormwater;flom fbr the discharge -Site StormwaterManaaen;ent projects] achieved require e construction pollution -generating by infiltration Bt1IPs. of .rtoimlvaler treatment lad lilies. Direct impel -pious surfaces togr'ourld water is or dispersion of rimoff/:from residential sites of except untreated of On t Flow impervious storlllrvater discharge Control sus f directly, to [an — Projects must pro. vide flow control to reduce the Impacts ofstormwater'rune from Gees and land cover conversions. The requirement r'ement applies to projects that di charge or indirectly through a conveyance .system, into afresh water— exceptfor that approved direct discharge receiving water] 8 Wetlands vegetation, and Protection — Discharges to wetlands shall substrate shamanistic, necessrn?' to support maintain the Ly'drologic conditions, hpdropLyiic e.\irling lend designated uses. 9 Basin/Watershed requirements... as Identified Planning Projetts may be subject t0 equivalent or more .Ctringent MInUl um Watershed Plans. — in Basin/ 10 Operation proposed operation and storinwater shall be Maintenance identified —.An facilities and .B111Pr, operation and maintenance manual... shall be provided for all and the par iy (or parties) responsible lbr the maintenance and The applicability of the minimum requirements is defined for both new development and redevelopment projects, as summarized below: New Development Projects. As quoted from the Ecology 2005 Manual, ".All new development sl all be regal ed to comply with Minimum Requirement #2" (entitled Construction Stormwater Pollution Prevention). "The lbllowilrg new development shall comply with Minimum Requirements # 1 through #5 Ibr the new and replaced impervious Rupees and the land disturbed (if the proposed new development): • Creates or adds 2,000 square fiel, or'greater, of new, replaced, or new plus replaced impervious J7nr face area, or • Has land disturbing activiyy of 7,000 squarepeet or greaten The f ollowing new development shall comply with Minimum Requirements # 1 through # 10 jor the new iinperyious sus faces and the converted pervious san, faces (if the proposed new development: • Creates or ad& 5,000 square leet, or more, of new impervious surface area, or • Converts 3/4 acres, or more, of native vegetation to lawn or Landscaped areas, or • Converts 2.3 acres, or more, o f native vegetation to pasture." Redevelopment Projects. As quoted from the Ecology 2005 Manual, "all redevelopment shall be itquir'ed to comply with Minimum Requirement #2. In addition, all redevelopment that exceeds certain lIason County .Belfair UGA Stormwater Jllanagemen/ Plan 39 otak K:A project \30700\30783\Reports\I3ellair S\V\IP\BelfairS\vA1Y.doc Section 5— Stormwater Management Criteria Continued thresholds shall be required to comply with addition/ Minimum Requirements as f Dhows. ▪ Redevelopment shall comply with Minimum Requirements # 1 through #5 Ibr the new and replaced impervious suifacec and the land disturbed (if): - The new, replaced, or total of nem plus replaced impervious sunl2ces is 2,000 square fret or more, or - The redevelopment involves more than 7,000 square feet or more land disturbing activities. • Redevelopment shall comply with Minimum Requirements # 1 through # 10 for the new imperious surfaces and converted pervious areas (if new redevelopment): Adds 5,000 square feet or more of new impervious smjaces or; - Converts 1/4 acres, or more, of native vegetation to lawn or landscaped areas, or - Converts 2.5 acres, or more, of native vegetation to pasture. • if the tunellym the impervious surfaces and conversed pervious surfaces is not separated/rout ri11r0ff from other sulfates on the project site, the sto77nwatel' treatment fiuilities must be sired Ibr the enure flow that is directed to them." • Also note that: "The local goverment may. allow the Minimum Requirements to be met.* all equivalent (flow and pollution characteristics) area within the same site. For public roads' projects, the equivalent area does not have to be within the project hints, but must drain to the same receiving water:" Existing developed properties are not required to meet the stormwater regulatory requirements discussed above unless the} undergo redevelopment. Flow Rate Control Requirements In regard to flow control, the stormwater compliance criteria used in this stormwater planning study are taken directly from the Ecology 2005 Manual for Western Washington. The compliance criteria, set foith in the Manual for basins requiring rate control, are as follows: 1. Stor/mvater discharge shall match pre -developed conditions flow duration values from 1 of the 2,year flow frequency through the 50,year,jlow frequency. (ilatchilrg flow durations e11s711es that any potential erosion problems downstream of the development are not exacerbated by the proposed development.) 2. Developed peak discharge fates should match pre -developed conditions peak flows for the 2-, 10-, and 50-year retur7l periods. (Matchiilg peak flows ensures that the downstream gstem hill continue to have the capacity to cony y the expected flow mates.) Note that the Ecology 2005 Manual flow control requirement applies only to stormwater runoff that discharges into flesh water. The 2005 Manual does not define flow control requirements for freshwater discharges into salt water receiving water bodies. Thus for some Ma s OP County — Be/fair U G A 5torm ;v a t e r M a n a; e »rent Plan 40 otak 1i:Aproject\ i0700\ 30784\Reports\13e1 Eai \VMP\13c1 iirS\\'\1P.doc Section 5— Stormwater Management Criteria Continued of the subbasins in the Belfair UGA, stormwater discharges after treatment could be directly discharged into Hood Canal without detention. These subbasins are hrnited to Subbasins 10, 40 and 100. Water Quality Treatment Requirements The Fcology 2005 Manual presents two sets of requirements for the selection of water quality treatment methods, depending on the type of development that is being constructed The Basic Treatment Menu is the standard for most residential developments, including those that discharge into salt water. However, there is also the Enhanced Treatment Menu that applies to developments with a more intense use of impervious areas and greater potential for pollutants leaving the site, including new roads and highways, and commercial and multi -family developments. These two menus are summarized below: The .Basic Water Treatment Menu allows any of the following options to be used: -Bio-infiltration Swale -Stormwater Treatment Wetland -Infiltration -Combined Detention and \X'etpool Facilities -Sand Filters-Bioretention/Rain Garden - Bio filtration Swales -Ecology Embankment -Filter Strips - `StormFilter' with ZPGTm media - Basic Wetpond-Wctvault To meet the Basic requirements, it is common for a developer to use either bio- infiltration/bio-filtration swales or some form of a wetpond, depending on the shape and amount of space available on the site. Wetponds are sized with continuous simulation models to treat the volume associated with the 91 percent exceedance value of all flows during the period of simulation, which is generally equivalent to 0.72 tunes the amount of precipitation of the 2-year, 24 hour storm event per the Ecology 2005 Manual. The Enhanced Wale, ,Oa/i/jy Treatment Menu allows any of the following options: -Infiltration with Appropriate Pretreatment -Large Sand Filter - Amended Sand Filter - Stormwater Treatment Wetland - Compost-amended Filter Strip -Two Facility Treatment Train -Bioretention/Rain Garden - Ecology Embankment To meet the Enhanced requirements, a developer will often use a two facility treatment train or a constructed wetland. Sand filters may also be requited for special pollutant removals such as nutrients. 1la.ron Ccunt J—Be/Ja r IT G A S l o r m w a l e r M a n a g e m e n t Plan 41 K:Aproject\ 30700\307$4\Reports\Bclfair SWMP\BclfairSW\IP.doc otak Section 5 Stormwater Management Criteria Continued Low Impact Development Techniques Ecology encourages the use of Low Impact Development (LID) techniques for stormwater management where appropriate. Mason County is currently considering the adoption of a LID ordinance, and approval by the Commissioners is expected by the end of the year. The Low Impact Development Technical Guidance Manual for the Puget Sound describes LID as follows: Low impact development (LID) is a stormwater sttategy that emphasizes conservation and use of natural site_ features integrated with distributed, small-scale stormwater control' to more close/y mimic natuialhyclrologi patterns in residential, commercial, and industrial settings. LID techniques have been considered in the development of the stormwater alternatives for the Belfair UGA, and are presented in Appendix A. LID techniques may reduce or eliminate the size of stormwater facilities and infrastructure. LID would be especially effective in areas with Group A (out\vash) soils, such as Everett and Indianola which are generally found the lowei elevations of the Belfair UGA, as shown in Figure 2-3. Outwash soils ale generally «ell drained with little generation of surface runoff. Such soils are well suited for LID techniques such as downspout dispersion and the use of permeable pavement. There are a large variety of LID options available; descriptions of potential LID options are included in Appendix A. Mason County Small Parcel Stormwater Site Plan Requirements Mason County Ordinance No. 114-06 provides requirements for managing storm drainage on small sites. A "Small Parcel Stormwater Site Plan" is required whenever a building application is made for residential development with more than 2,000 square feet of new roof, paving, gravel or parking area. The plan consists of a written description of the proposed stormwater management features, an erosion and sediment control plan to be followed during construction, and a residential site improvement plan which shows how stormwater runoff will be controlled after construction. The Small Parcel Stormwater Site Plan process complies with Ecology's Minimum Technical Requirements tt1 through -1/5. These requirements apply to developments with less than 5,000 square feet of impervious area under Ecology's definitions. Thus the Small Parcel Stotnnwater Plan requirements may also be applied to residential development bet\\ een 2,000 and 5,000 square feet. Above 5,000 square feet Technical Requirements /11 through //10 apply, and exceed the County's small parcel requirements. ilia on Coatntyy—Be/Jain UGA Stormwater Management Plan 42 otak 1i:Aproject\30700\3078 4\Reports\Belta;r SWNIP\Bel arr \l"'\IP.doc Section 6—Stormwater Concept Evaluations The development, evaluation and selection of stormwater management concepts for the Belfair UGA are described in this section. The evaluations were performed subbasin by subbasin and included consideration of the following: • Subbasin size and proposed land use • Receiving water and the presence of fish • Subbasin soils and the potential to infiltrate stormwater • Proposed land use • Potential for regional stormwater facilities within a subbasin or subbasins • Potential for joint -use stormwater facilities by expanding the proposed SR 3 widening project facilities to accommodate UGA development • Potential to implement water quality retrofit facilities for existing commercial areas • Potential fish passage improvements These evaluations provided the guidance to develop a recommended stormwater management plan for each subbasin. Resulting recommended plans and associated capital improvement projects are described in Section 7. As a part of these evaluations, hydrologic modeling was performed to quantify preliminary) watet quality and detention volume requirements for the types of land uses allowed by the UGA zoning and the local soil conditions within each subbasin. 'The results of the modeling are presented first, followed by the results of the evaluation of stormwater management concepts for regional facilities, joint -use facilities, water quality retrofitting and fish passage improvements for each subbasin. A summaiy of the stormwater engineering anal) sis is presented at the end of this section. Hydrologic Modeling Hydrologic modeling for the Belfair UGA was completed using a continuous -simulation model, MGSFIood, Version 3. I\IGSFIood is a continuous, rainfall -runoff model developed specifically for stormwater facility design in Western Washington It based on, and is consistent with, the design requirements of the Ecology 2005 Manual. The program uses the H PA Hydrologic Simulation Program -Fortran (HSPF) model for computing runoff from rainfall. MGSFIood uses one -hour time step precipitation data to predict flow rates. A GIS analysis \\ as used to delineate soil -cover areas for modeling. The modeling -v. as performed to estimate preliminary water quality treatment, detention and infiltration pond volumes for the types of development allow, ed by the Belfair zoning as well as for existing business -industrial developments that may wish to redevelop Water quality treatment will be required. Detention volumes were calculated only for Hydrologic Soil Mason Co r n i j—B e! f a i r UGA S l o rm w a t e r Ma n ag em e a t Plait 13 otak 1K:Aproject\30700\30784\Reports \13clfair S\VNIP\13elfairS\FNIY.doc Section 6—Stormwater Concept Evaluations Continued Group C (till) soils which generally do not allow significant amounts of infiltration. Runoff in Group A (outwash) and Group B soils was assumed to be fully infiltrated and thus no detention facilities Ns, ere proposed in these areas. The modeling was performed for conceptual ten -acre basins and the results converted to a unit acre basis. The results of the hydrologic modeling are presented in Appendix B and summarized in Table 6-1. Table 6-1 Hydrologic Modeling Results Rate Control and Water Quality Volumes (2005 DOE) Proposed Condition Typical Results Per I Acre Developed Land Use Developed Zoning Impervious Area Grass Area \\yet Pond Detention Volume (cf) Infiltration Footprint incl access (sf) (ac) Volume (cf) Pond Volume (cf) (ac) R-3 3.5 6.5 4,600 11,200 5,500 R-5 4 6 4,800 13,800 6,900 — R-10 5 5 5,100 14,800 7,300 MU2 8.5 15 6,700 18,300 8,500 — ROW 9 1 6,900 19,400 8,900 — Ex_BI_60 6 4 5,500 16,700 8,100 — Ex_BI_80 8 2 6,400 19,800 9,400 — MU(0.5) 8.5 1.5 6,300 17,700 8,500 — MU(1.0) 8.5 1.5 6,300 11,200 5,800 — MU(2.0) 8.5 1.5 6,300 8,500 4,700 — Zoning Classifications R-3 Single Family Residential R-5 Medium Density Residential R-10 Multi Family Residential MU Mixed Use EX BI 60 Existing BI 60% Impervious EX BI 80 Existing BI 80% Impendous The values given in Table 6-1 are for one developed acre. Multiplication of the values times a proposed development area will give a rough approximation of the volumes and land areas required for needed stormwater facilities. The land area estimates include a 20-foot maintenance width allowance on all four sides of the detention/treatment ponds. These estimates were also used to determine preli_minaiy land requirements for potential regional storm\eater facilities as a part of the facility evaluation process. Al a.ro n Co n n i i Be/fair UGYI S i o rm w a t e r Al a n ag em e n t Plan 44 otak K:AProject\30700\30784\Reports\13clfair S\C'\IP\BclfairS\Vr\IP.doc Section 6—Stormwater Concept Evaluations Continued Regional Facility Analysis Regional stormwater facilities are generally a cost-effective way to provide stormwater management for multiple users in a watershed. Regional facilities can also reduce future operation and maintenance costs, as typically only one or two facilities are constructed and operated for a large drainage area. Funding of regional facilities can be by private developers or by the County. A latecomer fee can be used by the County to recover costs as properties are developed and connect to the regional facility. Soil groups within the subbasins were the key factor in determining the potential for regional facilities In areas with Soil Group A or B, infiltration of stormwater in or nearby areas that are being developed is desirable; this reduces the cost of construction and the use of additional conveyance facilities. Collection of stormwater and. conveyance to an offsite regional site is also not as desirable as it changes the natural location of the infiltration. This can affect ground water recharge regimes as well as ground water contributions to stream flows. Subbasins with significant areas of Soil Group C soils are the most likely for the use of area - wide or regional detention stormwater facilities. This soil group is prevalent in the higher elevations east of SR 3 and is principally zoned residential. These regional facilities would most likely be constructed by private developers diming the development process. As a part o f the planning and feasibility deteuni nation of regional facilities, stream systems in each of the subbasins should be evaluated to determine if there would be any negative impacts such as reduction in base flows. Flow mitigation measures may be needed such as flow splitters to direct base flo« s and peak flows to mimic natural conditions and to bypass high flows downstream to lower regional facilities. All nineteen subbasins within the Belfair UGA were evaluated for the potential use of regional facilities. The key criterion was the extent of soil Group C in the subbasin. As a part o f the evaluation, core business areas and parks locations, as defined in the Belfair Comprehensive Plan (refer to Figures 4-2 and 4-3) were reviewed in regard to regional facility planning concepts. The results of these evaluations are presented in Table 6-2. Subbasins that were determined to have the potential use of regional facilities included nine o f the nineteen subbasins (Subbasins 30, 70, 80, 90, 120, 150, 160, 200, and 210). The potential locations for these regional facilities in each of the respective subbasins are shown in Figure 6-1. (Table 6-2 should be referred to for deciding information on whether of not a subbasin was judged feasible for regional facilities.) Ala.ron Connt1—Bel fair VGA Stormwater ill anasement Plan 45 otak K:A project \30700\30784\Reports\Belfair S\V\IP\13dfairS\V\IP.doc Regional Stormwater Facility Screening Analysis En 4-4 N E E 0 v N ca Cti v 50 0 O 1-0 v v Ln ^U • v O O N cc ✓ .-1 r r 2 •r 0 n U ✓ -U a ) H o U • 70 r- r H w « �R Cro a) O n otn • —I v s 0 i 0 w 4.4 O U 4.4 ti v 101 Ln ..0 O a O cn .v^..4 0 1 0 ale C.) 'u owe rti 0 4-10 U en J 0 'U • O N .`a N 0 U v 0-4 0 O 0 M en N 0 V) CH CZ O 0• v n O r • r O 0 2 O �T r 0 a) p .) r p rIri o d 0 v 0 O c v • ti • N v 0 1-4 v F-{ cc r w • 0 in • 0 • • n 0 en n .y « v v C.) N • w a) .v+ Ct 4..i 0 y 0 Q7 0 CO • N .4 re O L ) v b c. LCZ by ti T tn r v n -a b0 ''- • C. b� o • v CU U • 1.4 O w 1) y p "0 w O • tt .0 U ct cC G • U6) are ca L) the O bp O .� • cn • C' m N 0en .0 T U v ,CU r . o M bA 0. ac 0 v O U v « 0 U v O v 0 O H -ti • b r 0 0 1-4,11 y 1• r (1.) • y N 0 0Lin a) 1.4 W 1-4 cn • O v N en .b v C.) .b 0 i N o U W r i • 4-4 0 n U 1) H G\ bA r O M)J 1.n N-, -o v O O n 0 N � 44 0 C.) ✓ 1CZ 1 0 NO -u -o « Ca• s N 1 •y • .r U U • w r O i N p "t • o • O G O • v Hj v Nen • .7 :C U rt ai '1'40 o U v 0 [� H 50 r 74. CI) 0 0.4 H 0 O 'U v O ct .ti :a en O U G 0 vin n O �n 04 CIS U • 0 cn v U v • O • O v v .n - 70 • 0 r 0 „ el N O CLI Sr) H " n 'U • n �. ~ n on 0 O v o L'• ‘.0W 0 O 0 414 v en 0 v r 0 .� « Cn en CJ 4- • v 0 U C.) 1:1 n+ a w 0 v\ 0 v rt Pio .b v 0 .-1 cC N • n 0 v O « Q.) ram+ en r 0 N V e) n. en 0 N 14-1 J C.) Zw0 0 • U w N N yr ct •ao et en U v c� O 0 0 4-0 Potential for ct c 0 a) 0 h O frez 0 0 z 0 N U 0 z n v 0 N v N v 0 Subbasin Area Within UGA V et In rr M co 1 G" r c d• Lei to h N N et N Q 4) 0 1- M N .44 M 00 .4 V O 3 36 rn CD 41 06 00 CD esi cR CD (lc 0 04 .41 141 CIL cci 1.0 art I di Itte cc hP Section 6—Stormwater Concept Evaluations Continued UGA and WSDOT SR 3 Combined Facility Analysis The proposed SR 3 Widening Project through Belfair will require stormwatei treatment and detention facilities. Conceptual design of facilities for two stormwater alternatives has been developed by WSDOT and is reviewed in the SR 3 project report (Technical Memorandum No. 4) prepared by Perteet, Inc., for Mason County Alternative 1 provides for detention of net area increases in impervious areas from new roadway development and the release of flows to streams or by dispersed discharge. Alternative 2 proposes direct discharge to Hood Canal from the most southerly stormwater facility (west of Subbasins 10 and 100) and detention in the north pact of the project where the road alignment is distant from the Hood Canal shoreline. Discharge fiom the northerly facilities would also be by release of flows to streams or by dispersed discharge. For both alternatives, enhanced treatment of runoff from the entire width of the roadway is proposed through the use of constructed stormwater treatment wetlands. The locations of the stormwater facilities proposed in the SR 3 project report are shown in Figure 6-1. Not all UGA subbasins are tributary to a potential SR 3 stormwater facility. Those that are tributary \veie evaluated for possible expansion and use as joint -use facilities in accepting and treating other local/regional stormwater runoff. The results of the evaluations are presented in Table 6-3. Subbasins 10, 30, 40, 50, 60, 100, 110 and 120 have the potential to be served by joint -use facilities as they can gravity discharge to the SR 3 facilities. Opportunities for Regional Coordination The most likely non -SR 3 contributors to a joint -use facility would be from new or redeveloped commercial areas located along SR 3 and the large majority of existing and zoned business -industrial areas are located in Soil Group A soils Thus, infiltration of treated stormwater within these developed areas may be feasible and a viable alternative to the expansion of a WSDOT moadway storm facility into a regional joint -use facility. Analyses of alternatives on a site specific basis would need to be performed. Due to the timing and parcel -by -parcel nature of future development and redevelopment opportunities for the integiation of local drainage needs with proposed WSDOT SR 3 facilities is not likely to occur except perhaps in isolated instances. Water Quality Retrofit Analysis All UGA subbasins with commercial and industrial areas were evaluated for the potential water quality retrofitting. In general, the existing commercial areas within the Belfair UGA adjacent to SR 3 (with a few exceptions) do not have stormwater treatment facilities. An Mason County Belfair UGA Stormwater llanacgement Plan 47 otak K:Aproject\307(.i)\30784\Reporic\Bellair S\V%\IP\Belfairti\V'\IP.doc ao "C C CU N C C C • .c C C 6b O w V L u0 (d c9 L 0 N it C CL O U N N Comments . C r u L.)J N/;1 - no site available Potential joint facility Potential joint facility C is Potential joint facility Potential joint facility :J r c .' UC +.. No facility available Basindownstream of SR3, some potential for l 1 & 1-2 facilities for areas close to SR-3. ter". — CJ 4C..` C Cn I C L "J 54 Does not drain to SR3 llocs not drain to SR3 Does not drain to SR3 Does not drain to SR3 Does not drain to SR3 (; 99.9" No Does not drain to SR3 C.' ;-• J L 0 H A J C .ro •O UN r Z J' T J' > J' Z Z ✓- 1" Y Z Z Z Z Z Z Cd C N O d —. c. Cad �; .; _ C.-.r 4 c: c. t>1 Primary Hvdrolocic Soil 0.. L. V .... Cl CI• .1 , dadVOi N CCl 0 - - e 6-3 In n- 1 Subbasin Area Q 0 C ...0 1) et V; c- �r1 1, re "I' c C 68.7 C V -/- lfl \: .- C1 C1 K; Cl 15.7 r M. n ^ .- \: CI .: V .- CI .— -CM N S Total Area (ac) n rl — 1 c `. 344.1 125.4 251.1 C.1 "t c . x r1 �.1 ..... .- r- c C L U — _ _. — .__ _ .__i UR — .� _. J v • .._J �. �. -- Water Type D - — D — — D J Z Z D D. Z ...) —. J .l J Water Course Unnamed Drainage J Svvcctvvater (seek Unnamed Drainage .f r _ —Ft Miindv (;reek Bclfair (seek Unnamed Drainage Unnamed Drainage (;reek / Wetland _ Pr.— Unnamed Drainage J C. I :_ c.c.r. ^ F F. Cf. r ^ P < Unnamed Drainage .. Cf. c' ^ F P.. J .. tr., N rm 7 1 Subbasin ID # — 2tl 4(1 OS .- rl •C I CI Section 6 Stormwater Concept Evaluations Continued approach that retrofits existing commercial areas to provide for water quality treatment of runoff before discharging to Union River and Hood Canal would be beneficial and is an important consideration for the development of the UGA. Commercial areas of potential water quality retrofit are defined by areas of commercial and/or industrial development on either side of SR 3 within the UGA. These areas are shown in Figure 6-2. Photo 5—Belfair Creek crosses SR 3 through a 48-inch culvert. Existing development is in the background. Factors considered in the evaluations included developed commercial and/or industrial area, primary- soil group, the potential to use a joint -use facility and the potential to use LID methods. The results of the evaluations are presented in Table 6-4. In 15 of the 19 subbasins, either joint -use facilities or Low Impact Development methods (or both) provide the potential for water quality retrofit. The comment column of Tablc 6-4 should be referred to for information on whether or not retrofitting was applicable foi a subbasin and if so how water duality retrofitting could be accomplished. Fish Passage Improvement Analysis The Belfair UGA contains both fish bearing and non -fish bearing streams, as shown in Figure 2-4, according to the stream survey information obtained from DNR. The fish bearing streams were reviewed for possible improvements that would restore or facilitate the passage of fish. Fish passage barriers include non -fish friendly culverts beneath SR 3, culverts within commercial areas and vei tical height barriers. Solutions include fish -friendly Al a n Conn 1) Bella i r- UGA S t o rm m a t e r Management Plan 49 otak K xojeci 30700\307&I\Rep, c\13c1Fair S\t`iAIP\Bclfair5\V'`\tP.doc c O ect 0 CU 4-3 0 a) 1- ct a L d) Comments LID retrofit is encouraged, however due to the small amount of existing developmi used for retrofit of existing development (depending on when facility is constructer No existing development to retrofit. 4. `'. J ? G 1.ID retrofit is encouraged, however due to the limited amount of space between c may be limited. Joint facility may be used for retrofit of existing development (dupe I,JD rctroftt is encouraged, however due to the limited amount of space between el, may be limited. Joint facility may be used for retrofit of existing development (dope Joint facility may be used for retrofit of existing development (depending on when shows a proposed downtown park that may provide a location for LID retrofit. C'_ 0 w u w C) ra • 1sxisting water quality treatment is by dispersion as stormwatcr infiltrates at a local improved by providing pre-treatment in the form of a filter strip, ram garden or oil Joint facility may be used for proposed development and retrofit of existing dcvclo I?listing water quality treatment is by dispersion as stormwatcr flows to I lood Can: by providing pre-treatment in the form of a filter strip, ram garden or other 1,1D tot Joint facility may be used for retrofit of existing development (depending on when treatment (such as the open channel through the QI C parking lot) can be improve( strip, rain garden or other 1,1D technique. Underground storm filter vaults may be i the space to use ',ID techniques. Existing water quality treatment (achcivcd by dispersion) can be improved by provi garden or other 1AD technique. Underground storm filter vaults may be installed tc to use LID techniques. joint facility may be used for retrofit of existing devclopmet lC ': , Cl 4-4 G 1,xisting water quality treatment (achcivcd by dispersion) can be improved by provi garden or other 1.I1) technique. I,ID retrofit is encouraged, the extent of existing water quality treatment is unlanow 1,ID retrofit is encouraged, the extent of existing water quality treatment is unknow No existing development to retrofit. IJD retrofit is encouraged, however due to the small amount of existing developm( cu w prvvwc prc-ncarment upstream or cxtsnng [re meats and SR3 die retrofit benefits may be limited. J on when facility is constructed). 1- 0 G en N_ f .hT. eal rt t cC G r u R. J G u 0 . •% y C C.L �+ ii C 7..)-o U -t tr ri X 0 0 O > 0 b _ y J Z 0 k J Z 4J N n Z Z Z U i1 r J i• J i' J i- J i^ 0 i- J i' i• J 7' Z U r :J i-' Yes Z ! J .-1 nt Caw 0 0. O C J d' Yes Z J it J i' U i" J :, 7: C) n Z ? C) ;. J 0 ;. .. Z .. Z .. ZZZZZ .. .. .. N (n 0 " �; C ° Ce N rm. ,� 100.0% c re) c-R co c If -i c o In m r 0 O in' 0 r� cN 0 r 4 r �� oo '- w o to c: --1 a CI v ..-nr c — r M a in — to o M 4No c, o in r O O to c r C cc. O to.--: c.. 0 c' . p N0 V •� 0 0 `. O n- v O dnoJD / I / / / ..� L c I I / / / / 1 0 L- CIZi E 0 - 0 O G 0 a-. O N C O\o 1" 1/40 0 N. CO to Co O o0 r 57% o ..O -000 O c` I, I VI (ac) en .-4 Cl O co O M CT to O 7.8 `-' t^ i'�' rl V' M Ct`I CI elO o 14.0 t+1 .6 28.7 O O 0 O O 4 Subbasin Area c :EQ In -o to _ . o r r ‘.0 0 en -r yo c'N r i �i 7 f t N r r M c, C - c`d .0 o — rl _vT -- nl cc +C Total Area (ac) _1 el)M ri N 212.6 l -1 o0 7-4 -r c o 4 v r Co — rt 7 n 4 tri CI • --' to C.1 '0 r N o IA _1- o t") M - 06 00 203.9 I r-\o o O -- ei M -3- .6 O C`i e1 o tko J--) _ _ J _J • v _ '�- ID_J CD v v •--• 9 U v 1 1✓ (CI 0 I-). D _J _ U � 7 7 D / D ID D D ID L9- r Section 6 Stormwater Concept Evaluations Continued culvert system, stream relocations, and fish ladders. The locations of potential improvements are shown in Figure 6-3 and described below. • Belfair Creek Belfair Creek is typed by WDNR as fish bearing in its Forest Practices Water Typing mapping. The section of the creek through the commercial area on the west side of SR 3 is piped for about 600 feet. Reinstatement of the creek through this section would require the purchase of private property, construction of a new stream channel and appropriate stream bank .landscaping, and construction of a fish -friendly culvert system from the east side of SR 3 to the beginning of the new stream channel. The preliminary estimate of project cost for this is $1,500,000. • Mindy Creek —Mindy Creek is similar to Belfair Creek in that it is piped beneath SR 3 and through a commercial area on the west side of SR 3. The SR 3 project report provides an improvement plan for Mindy Creek that eliminates the piped section by rerouting the creek to the south on the east side of SR 3 and then beneath SR 3 via a fish friendly culvert. From this point, a new stream channel would convey flow to the southwest where it would join the existing Mindy Creek stream channel. This study concurs with and supports the concept presented for Mindy Creek. Photo 6 Fish Friendly Culvert at SR 3 at Sweetwater Creek Sweetwater Creek —This creek has a fish friendly culvert beneath SR. 3. However, on the east side of SR 3, a fish blockage exists. The blockage is a drop of about six feet associated with a water wheel. It may be possible to install a fish ladder to provide passage around this obstruction. However, the stream channel condition for fish is not known upstream of the obstruction. It is recommended that a reconnaissance study be MasonCount:), Bellair Lr G t1 .S' f o r rr m a z e r Al a rr a,ge mmr e n t Plan 51 otak K: Aproject \3(t71W \ 30784 \ [I I' s\Belfair S\\';1IP\BellairS\\'\IRdoc • Section 6---Stormwater Concept Evaluations Continued made of Sweetwater Creek to determine the appropriateness and feasibility of a fish passage facility to improve this potential fishery resource. Photo 7—Waterwheel Fish Blockage Upstream of SR 3 Unnamed Channel The SR 3 Widening Project Report also mentions a fish blockage at the 24-inch culvert crossing of an unnamed channel. This blockage should be field investigated and improvements defined. Subbasin Design Parameter Summary Design parameters for each Belfair subbasin are presented in Table 6-5. The parameters include the subbasin area, soils, existing land use, proposed land use, primary and secondary method of runoff rate control, water quality treatment standard, and the potential as determined from screening analyses for regional stormwater facilities, joint -use facilities with the SR 3 improvement project, water quality retrofitting of the existing commercial area and for fish passage improvements. These parameters provided the guidance used to define the stormwater management approach for each subbasin. Nor example, a subbasin with principally residential development and soils with good infiltration characteristics (such as Subbasin 20) would not be a good candidate for a regional stormwater facility. This is because infiltration is readily available for new development and through the use of more expensive regional facilities is not needed. Mason Conn f - Bella/ r U G A S i o r m in a t e r Al a n a cg e m c n t Plan 52 otak li:Aprojcct\30700\3078 4\Reports\13clln[ \\ iAIY\13r1 rS\C'NIP.doe N C 0 ct Lb W C u 4) i cd U c cn ct N 0 >. cd E N p) C UA C`a •U rr 'U v. '() 0 .._ U ..-. U .-. ti �.re or V U _..K. U ro rr�. U o'r--. U re .--. 0 GC --. U .--. 0 ro U 0 U r x v. et S. F° VI Rate Control Method Secondary n n n� n n n - n n r, r, n r, (, r 10 O. _ P.c. r- ..- .-_. _ r1" ex, _. 'l. ..J _ ._ r-..'-. J) •- Cf: _ •-• r _ ROW Land Use N L. 0 O d . -tCn . t I - r . in -- CA o 't _- _ . _ Fr .- y C _ - t ._ C. In _ _ `. __ - 0ot Future Residential in �; 7 - in 33°0 -c. a. — - - Fatal O - - 00 0 "00 (n n o C7 0 (`1 M CI 0 _ - = C1 1 100°0 t - r - Cl - M - r+': "011• - ^ CI 35°0 - c .^� o Co _ o t _ _ ... CI M-. CC Future C`I (n ? (`' M M .. N %• CI c` �' "01Z to r rr `. �;, n - — — c.� �^. CI �' - "' ...... u'1 CI O (ac) in r - Cl o x 25.8 ti; in 1n •1 95.7 ,.r; Cl 567.4 B-I, FR, GC & M iY L1 1.1J In ..-. 7 _ J .... (ac) re,CI 0.0 cM ^ -y x 15.1 '-n — c �'^• CI C1 n] 14.0 ul in r CI 0.0 rt C! Hydrologic Soil Group for areas within the UGA Secondary 1 44.8°0 0. 1 .. C.0 ..--a! ! ! ! 0 (..9 ct oM �. c, lt'; V to x' Le) r -- x — ill C (`1 - r 51.3°h M -f Lfl c '0 r V In -- r d L L Q in vl r. C 0 r 4 125.4 110.9 C.I Ci 15.7 r ,.M .: Ca CI in F CI un CI N -I--7 1 64.0 v rr vi -- 0,1 ' 267.6 t en x re-,, CI c1 en 4 119.2 �, Receiving Water _ IEC _ ._ _, _ L `. _ .J UR _ ._. re. .J ^ v r _ Ci `. _ Water J = = J J J 7 N J N J . _J -- In r. u.. - ._ ,.r., c -_ ._ ,_ a 7.3 V ddd It. r r r ti U 770, UU - "a v C r' N -i ^ C ' '- i.J r _N 0 tt cCI 5 _ v v• i N - 775 .71 • (40 V 7 bd.)f, r. -o c er U \ VC 717.3 - 7 - J G V " a 'J • r C \ U r - Rate Control Method t r r n 'I. rposi r Section 6—Stormwater Concept Evaluations Continued Recommended stormwater plans for each Belfair subbasin are presented in Section 7. These are developed for each subbasin based on the results of the evaluation of parameters as defined in this section. For example, the subbasin size, soil group type, future zoning and joint -use facility availability all influence the sub basin's stormwater management plan. Ma a n Conn,y Belfair U GA S t o rm m at e r Al a n ag em e n t Plan 54 otak K:Aproject\30700\ 3078 {\Reports\Bc1fair SW\IP\Bel fairSWNIP.doc rroposeu vv racniryr Potential Joint Use Facility Potential Region S\W Site Hydrologic Soil Type A County Boundary Belfair UGA Boundary 3IS data and Aerial photography from Mason 006. Disclaimer: This map is not to survey and is meant for planning purposes only. IE County Boundary Proposed SR3 SW Facility! Potential Joint Use Facility Commercial Industrial Residential GIS data and Aerial photography from Mason 2006. Disclaimer: This map is not to survey cy and is meant for planning purposes only. gene creek IE O4 1 wz NE,Gp:RRICKI: A )n-Fish FED ream iknown :ounty Boundary eifair UGA Boundary ;IS data and Aerial photography from Mason )06. Disclaimer: This map is not to survey and is meant for planning purposes only. ,•-,7' f „ (V" ;12 V -±- ' it, IR NE FE Abandon Piped Section of Mindy Creek tfitte40, , 4 nig,BEITAIR ST NE NEWKIWRIDI Belfair Creek Proposed Fish Passage Improvements Mindy Creek Proposed ReAlignment and Fish Passage Culvert Section 7—Stormwater Management Plans Based on the previous analyses described in Section 6, stormwater management strategies including both projects and management activities have been developed for the Belfair UGA. These strategies have been developed and ate presented by subbasin to reflect the soils, existing development, zoning and other characteristics unique to each subbasin within the study area. The management strategies presented in following Belfair Stormwater Management Plan focus on enhancing the design criteria for new de\ elopments as well as studies and projects aimed at enhancing water quality and habitat functions within the Belfair LTGA. The fast priority is a recommendation to use the Ecology 2005 Manual requii ements for new development and ultimate buildout. It is anticipated that most future stormwater improvements associated with new development will be designed, constructed and funded by private developers, and have therefore not been included in the Mason County, Belfair SWAM Plan or associated CIP program. The exception would be if the County determined that it would be in the public's best interest to acquire a potential regional stormwater site because of its strategic location with respect to drainage considerations. This advance purchase of the site would likely be paid back by future development. Summary of Findings • The following are the key findings associated with the development of the Belfair UGA Stormy ater Management Plan: • There are no identified existing major flooding or hydraulic capacity problems within the Belfair UGA and, as a result no major system upgrades are being recommended. • Fish blockages are present on Belfair Creek and Mindy Creek and projects to correct both of these blockages have been identified. • Baseline habitat and water quality data are not available for the streams in the Belfair U GA. A program is recommended to obtain this information so that problems can be identified and projects developed to address any significant problems. • Ecology has established a Total Maximum Daily Load for fecal coliform bacteria for the U nion River. Activities are identified to enlist the public through educational means to reduce fecal coliforin bacteria as well as other pollutants associated with existing stormwater discharges. Water qualit) retrofit potentials have been identified for each subbasin with existing commercial -industrial development should they be needed to address the water quality problems in the Union River and Hood Canal. For identified problems, a cooperative ietrofit program has been proposed with potential funding developed on a cost sharing basis by property owners and Mason County with support from future grant funds. Mason County—Belfair UGA Stormwater 1\1anasement Plan 58 otak K:Aprojcct\30700\30784\Reports\13clfair S\V\IP\13clfairS\V\IP.doc Section 7—Stormwater Management Plans Continued • The Belfair Comprehensive Plan contains plans for future park and transportation improvements; coordination of these regional planning efforts with stormwater recommendations as provided in plan. • The use of regional stormwater facilities in the Belfair UGA will, with limited exceptions, be most applicable to the residential zoned areas cast of SR 3. Subbasins with the regional SWIM facilities potential have been identified. • Due to topography and existing and future land uses, there are limited opportunities to coordinate the regional drainage needs of the UGA with development of SR 3 drainage facilities proposed by WSDOT. Recommended Stormwater Management Strategies for Each Subbasin Recommended stormwatet management projects and activities for the Belfair subbasins are presented in Table 7-1. Implementation of these plans will be principally by private developers as new projects are constructed within each of the subbasins. Fot each Belfair UGA subbasin, the stormwater strategy includes the following: • 'Type of development • Type of needed water quality and rate control facilities • Potential water quality retrofit opportunities for existing commercial -industrial development • Potential use of regional SR 3 joint -use stormwater facilities • Consistency with Belfair Comp Plan and vision for ultimate development. • Opportunities to coordinate with future County infrastructure projects (especially transportation projects) • Proposed fish passage improvements The desirability of coordinating with WSDOT on joint -use stormwater facilities, water quality retrofitting of existing commercial areas and implementation of fish passage improvements is acknowledged and reflected in this plan. Whenever practical, these types of regional project have been promoted and included in this plan. The various elements of the recommended stormwater management activities for the Belfair UGA are presented in Table 7-2. Implementing actions, investigation and programming activities and CIP projects are included in the activities which span a 20-\ ear period Mason Collnlj— Belfair UCA Sfornater :llanasemen/ Plan 59 otak IC: Aproject\3(I700\30784\Reports \ Bel Eli r SWNW \ Bel (airS\V\IP.doc Et J 5 \ i -0 l J• '� ~ j n iJ . G C gL4. c: UJ ri a ... _ .i Regional or SR 3 joint -use stormwater facility program J cJ r. v. tn 3 C. NA-'l'ype .\ soils present Tl is is a large residential basin with primarily Type C soils. Regional facilities or multiple -project shared facilities are possibilities. Such facilities would be best funded privately. loins -use project with SR 3 Pond . possibilities. Such facilities would be v. I Dint -use I 'acility: :her for water quality retrofit adjacent to SR 3. ity: Fossil 1 1 ' either for water qua] •cial adjacent to SR 3. Existing commercial water quality retrofit program N.\ - only a small area of commercial is present. future site evaluation for LID application recommended. N;\ - No existing commercial is present. Future site evaluation for 1,11) application recommended. N:\ - No existing commercial is present. future site evaluation for 1,11) application recommended. :res of existing commercial presence of Type ;\ soils, the lack of id the distance to Flood Canal would .te treatment of this runoff may be rfacc discharge through the soils in the resin 100. further analysis of to collection in Subbasin 40 and bbasin 100 would be necessary to a lcquate soil treatment. Approximately 6 acres of commercial development is existing. This area is a candidate for water quality retrofit. Treatment facilities could be located in Subbasin 50; or down -gradient in Subbasin 100 either as a standalone facility or partially in a joint -use facility with the SR-3 project (Perfect Ponds J, 1< and 1.) in Subbasin 100. 60; or doyen -gradient in Subbasin 100 either as a standalone facility or in a joint -use facility with the SR-3 project (Perteet Pond 12). This would be a combined project with Subbasin 50, Mindy Creek. Approximately 15 acres of commercial development is existing and this will increase to about 26 acres in the future condition. This area is a candidate for water quality retrofit. Treatment facilities would be located in Subbasin 80 as a standalone facility. Joint use opportunity with the in this basin. Potential wale ,es may exist at the proposed the proposed Perteet Pond Type of development and water quality and rate control facilities Roughly half commercial and half residential development. 'Treated stormwater will be infiltrated. 86% residential development. 'I'hc large majority of stormwater will be infiltrated. 91% residential development. About two -third of the .development will have detention and discharge to the creek. The remainder will infiltrate. me -third commercial and two-thirds residential Lent. The majority of the stormwater will be Romance 11111 Drainage system. About 14 acres of commercial development is planned for the future of which 6 acres is existing. Some of this development will likely be redevelopment of existing commercial properties. Roughly half commercial and half residential development. "Treated stormwater will be infiltrated. ential development. About 82% of the development lave detention and discharge to the drainage system. 51 % R-10). About 72% of the development will detention and discharge to the creek system. "I'h Subbasin Area C LE Q v in 40.5 M - co __, -Y G, O -t V 1— cA No 0 re -t 1 "' +_ 0 Total Area V co r'1 r1 to CJ1 cal M -1- co -t G�V �-h r c(: V •O -t 7 M �. in cal Receiving Water N _N r\CLu11111 ICI IUCCJ JLVI I I IVVdtCI I. Id1 Id6C1I ICI IL F ldl l3 \ \ n I-, eu \ \ \ \ Regional facilities or multiple -project shared facilities are Regional or SR 3 joint -use stormwater facility program ['his is a large principally commercial basin with equal .rcas of Type :\ and C soils. Regional facilities or This is a large principally commercial basin with equal areas of Type ;\ and C soils. Regional facilities or multiple -project shared facilities are possibilities. Such facilities would be best funded privately. Joint -use d/\\ \ ly 40%'Type C soils. Regional facilities :t shared facilities are possibilities. Such best funded privately. loint-use ulsuggns 11etus - \'N4 \ \ \ \ \ This is a large principally commercial basin with equal areas of Type A and C soils. Regional facilities or multiple -project shared facilities are possibilities. Such facilities would be best funded privately. \\ \\\ 1 /�_C - __fl /_ /\jj • 'Approximately 24 acres of commercial development is existing and this will remain at about 24 acres in the future condition. (Ibis area is a candidate for water quality retrofit. 'Treatment facilities would be located in Subbasin 110 as a standalone facility, or possibly for part of the area in a joint -use facility with the SR-3 project (SR 3 Pond N) in Subbasin 110. Joint facility may be used for retrofit of existing development (depending on when facility is constructed). I?xisting water quality treatment (such as the open channel through the OI+C: parking lot) can be improved by providing pre-treatment in the form of a filter strip, rain garden or other 1,I1) technique. Underground storm filter vaults may be installed to retrofit existing developments that lack the space to use l,I! techniques, proximately 28 acres of commercial development is ;ring and this will incrcasc to about 42 acres in the Ire condition. 'Ibis area is a candidate for water quality ofit. 'Treatment facilities would be located in Subbasin NA - No existing commercial ;\pproximatcly 16 acres of commercial development is existing and this will increase to about 24 acres 111 the future condition. This area is a candidate for water quality retrofit. Treatment facilities would be located in Subbasin 140 as a standalone facility. ;\pproximatcly 57 acres of commercial development is existing and this will incrcasc to about 96 acres in the future condition, This area is a candidate for water quality retrofit. 'Treatment facilities would be located in Subbasin 150 as a standalone facility. Approximately 29 acres of commercial development is existing and this will incrcasc to about 71 acres in the Approximately 10.5 acres of co existing and will increase to abc Approximately 18 acres of cc existing and this will incrcasc future condition. This area is retrofit. Treatment facilities Type of development and water quality and rate control facilities 23% 11l O residential development, 759/0 commercial development. About 50% of the development will have detention and discharge to the creek system. The remainder will infiltrate within or near individual project areas. 35% residential development, 63% commercial development. About 50% of the development will .infiltrate within or near individual project areas. The remainder will have detention and discharge to a creek 33% R-10 residential development, 569/0 commercial development. The existing commercial area is about 58% of the basin, so there will be only a minor change from existing to future commercial land use. In theory, about one-third of the development could be infiltrated within or near individual project areas. 1 Iowevcr, the extent of the existing subbasin development will likely provide a lesser fraction that will infiltrate. The remainder will have detention and discharge to a creek system or by dispersion. Redevelopment criteria will apply to much of this subbasin. levelopment, 164/0 commercial bout one-half of the development will r near individual project areas. The Eve detention and discharge to the creek 1009/o R-3 residential development. Nearly all areas will have detention and discharge to a creek system or by dispersion. 76(1/0 residential development, 139/o commercial development. ;\bout 759/0 of the development will infiltrate within or near individual project areas. The remainder will have detention and discharge to creek systems or by dispersion 969/o B-1 commercial development. About 50% of the development will infiltrate within or near individual project areas. The remainder will have detention and discharge to existing systems or by dispersion. 69% residential development, 26% commercial development. About 679/o of the development will Subbasin Area / / m ± / \ 1 / % / y , / D Total Area cc tao \ _ / = z § J 7 7 7 Regional or SR 3 joint -use stormwater facility program :eeional I acilic�i:'1'his is a medium sized residential basin 2e zonal l cacility: This is a medium sized residential basin with a 60/40 split between Type .\ and C soils. Regional facilities or multiple -project shared facilities are possibilities. Such facilities would be best funded privately. a r r r. Existing commercial water quality retrofit program N;\ - No existing commercial N:\ - No existing commercial Approximately 4 acres of business -industrial development is existing and this will increase to about 10 acres in the future condition. This area should be field reviewed to determine if it is a candidate for water quality retrofit. If so, treatment facilities would be located in Subbasin 220 as a standalone facility. 100% R-5 residential development. About 62% of the development will infiltrate within or ucar individual project areas. 'I'hc remainder will have detention and discharge to creek systems or by dispersion. 100% 13-I commercial development. Nearly all areas will have detention and discharge to a creels system or by dispersion. control c, c< ci o 231=1.1 ci c< ca o _ -7 Ki co M Long Term 4-20 Years X X Short Term 1-3 Years M X X X X X X X X X X X cV X X X X X X X — X X X X X X Funding Source 0) c E. y m w0 WSDOT Future Grant Future Grant Future Grant Future Grant To Be Determined To Be Determined Future Grant Future Grant Future Grant Future Grant To Be Determined To Be Determined N 0 U 0 $ 1,500,000 To Be Determined 0 0 R. ci te _ W r` J 3 County Staff or consultant (,aunty `toff County Staff County Staff County Staff County Staff County Staff County Staff County Staff _ it ✓ County Staff i 1 0 0l. 00 N Y •� 0 L. a L S L S High 0 S .c S S S 7 a) 2 High L S L S Medium High High Low Low Low Supporting Agency Mason Co. Mason Co. Mason Co. HCSEG Mason Co. Transportatio n Mason Co. Parks HCSEG HCSEG WSDOT rablE Lead Agency Mason Co. Mason Co. Mason Co. WSDOT WSDOT WSDOT Mason Co. Mason Co. Mason Co. Mason Co. Mason Co. Mason Co. Mason Co. Mason Co. Mason Co. Mason Co. • 1 u Q Activity #1:Adopt Ecology 2005 Manual Activity #2: Establish dedicated stormwater funding for Belfair UGA 'Activity #3: Adopt Low Impact Development Ordinance Activity #4: Coordinate with WSDOT on relocation of Mindy Creek as a part of the SR3 project Activity #b: uooramate wan vvavu I on atreetscape Improvements Tor water quality as part of the SR 3 project Activity #b: uoorainate wan vvauu 1 on joint -use stormwater -facilities as part or the SR 3 project Activity #7: Prepare Low Impact Development and Property Owners Guide to Stormwater Pollution Control Brochures Activity #8: Perform baseline habitat and water quality study for Belfair UGA streams Activity #9: Coordinate with Mason Co. Trasportation Department to incorporate LID and WO benefits into transportation improvements as identified in the UGA Plan. Activity #10: Coordinate with Mason Co. Parks Department to incorporate LID Activity #11: Develop and conduct public information program to promote water quality awareness for private properties Activity #12: Perform Sweetwater Creek Fish Passage Improvements Study Activity #14: Develop cooperative commercial water quality retrofit program with cost sharing provisions CIP No. 1 — Belfair Creek relocation and fish passage Activity #16: CIP No. 2 — Sweetwater Creek fish passage improvements (if found feasible by Activity#9) Total ($1,700,000 + Grants) Activity #13: Perform Belfair Creek Fish Passag Q 7 2 C 0) E 0) 0 c as c c W 0 E U a 0 0 C7 w 0 K:\project\30700\30784\Reports\Belfair SWMP\BeltairSWMPTables7.xls Section 7—Stormwater Management Plans Continued Each proposed short-term activity (1-3 years) is described below. Activity #I: Adopt Ecology 2005 Manual. (Using existing County staff) • Develop and adopt an ordinance requiring the use of the Ecology 2005 Manual for all new development within the Belfair UGA. Activity #2. Establish Dedicated Stormwater Funding for Belfair UGA. (Using existing County staff) • Develop and implement a dedicated funding mechanism to support stormwater management activities and capital improvements within the Belfair UGA. Activity #3. Adopt Low Impact Development (LID) Ordinance. (Using existing County staff) • Complete the development and processing of the county -wide LID ordinance. Activity #4. Coordinate with WSDOT Regarding the Relocation of Mindy Creek (as a Part of the SR 3 Project) (Using existing County staff) • Coordinate with WSDOT on the relocation of Mindy Creek on the east and west sides of SR 3 and the installation of a fish -friendly culvert under SR 3 relative to the stream habitat enhancement objectives of the Belfair UGA Activity #5: Coordinate with WSDOT on Streetscape Improvements (As a Part of the SR 3 Project) (Using existing County staff) • Coordinate with WSDO'I' on streetscape improvements in areas where right-of-way width may allow water quality facilities (rain gardens, etc.) to be included for treatment of existing impervious areas. Activity #6. Coordination with WSDOT on SR 3 (Using existing County staff) • Coordinate with WSDOT to establish the feasibility of joint -use stormwater facilities at proposed SR 3 stormwater treatment and detention sites. The Belfair interest in these facilities would be primarily for water qualit) retrofit purposes and/or to support new future commercial development along the SR 3 corridor. Timing of development with respect to construction of the WSDOT facilities may affect the feasibility of these potential joint -use facilities. Activity #7. Prepare Low Impact Development and Property Owner Water Quality Brochures (Using existing County staff) • Prepare and distribute of a brochure describing low impact development techniques for onsite detention and water quality treatment and a brochure describing actions Mason Conn/ y—Be!Jair UGA Siormwater rllanagement Plan 64 otak 1..:Aproject\30700\3f78 4\Reports\13clfair S\VNIP\l3clfaivS\ViA1P.doc Section 7—Stormwater Management Plans Continued residential and commercial property owners can take to improve the quality of stormwater being discharged from their properties. Activity #8: Perform Baseline Habitat and Water Quality Study for Belfair UGA Streams • This study would inventory the habitat of the existing streams within the Belfair UGA. It would also involve water qualit} testing on each stream to determine if problems exist. Any identified problems «ould be addressed during the implementation of the Belfair Stormwater Management Plan and Comprehensive Plan. Activity #9: Coordinate with Mason County Transportation Department to Incorporate LID and Water Quality Benefits into Transportation Improvements (Using Existing County Staff) • Coordinate with the Mason County Transportation Depaitment to incorporate LID and water quality benefits into transportation improvements (sidewalks and landscaping), as identified in the UGA Comprehensive Plan (along Old Belfair Highway). Activity #10. Coordinate With Mason County Parks Department to Incorporate LID and Water Quality Benefits into Planned Park Improvements (Using Existing County Staff) • Coordinate v.ith Mason County Parks Depaitment to incorporate LID and water quality benefits into park unprovements, as identified in the UGA Comprehensive Plan. Activity #1 1. Develop and Conduct a Public Information Program to Promote Public Water Quality Awareness for Private Properties (Using Existing County Staff) • Once the brochures of Activity #7 ale available, two or three public informational meetings would be held in Belfair to educate residential and commercial property owners on sto11n\; ater pollution and encourage their paiticipation in enhancing the quality of water reaching the Union River and Hood Canal. Activity #12: Conduct Sweetwater Creek Fish Passage Improvements Study. • Conduct a fish passage improvement investigation for Sweetwater Creek. Develop options and costs to eliminate vertical drop fish barrier associated with the water wheel. This activity would start after confirmation from the baseline habitat study (Activity tt8) that areas above the water wheel would support fish. The study would include coordination with WDFW on passage design options and a pioject cost estimate. Activity #13. Prepare Belfair Creek Fish Passage Improvements Study. • Conduct a fish passage improvement study for Belfair Creek from the east side of SR 3 to the existing active stream west of the commercial area. The stud) would include an alternatives analysis for stream location, accommodation of existing commercial uses, Mason County Belfair LICA Stornaler Management Plan 65 otak K:Aproject\30700\30784\Reports\&air S'X'NIP\lielfairtiW\IP.doc Section 7—Stormwater Management Plans Continued preparation of preliminary plans, coordination with \ 1DFW and preparation of a project cost estimate. Activity #I4. Develop Cooperative Commercial Water Quality Retrofit Program (Using Existing County Staff) • Develop a cooperative program between Mason County and existing commercial - industrial property owners to retrofit existing commercial areas for water quality treltment, where problems have been identified (in Activity #8), to improve the quality o f stormwater being discharged to the Union River and Hood Canal. A cost sharing formula would be developed as part of the program with Mason County financing part o f the improvement costs'and the property owner financing the rest. Most of the commercial areas adjacent to SR 3 are underlain by Hydrologic Soil Group A soils which generally support infiltration. Retrofitting possibilities for individual commercial properties include infiltration of roof runoff, collection and pretreatment of road and parking area runoff in rain gardens or filter catch basins, followed by infiltration and treatment within the soil matrix. Long-term activities (4 — 20 years) include two potential CIP project as outlined below. Activity #15. CIP No. 1 Belfair Creek Relocation and Fish Passage Improvements • Perform final design, right-of-way/property acquisition and construction of the Belfair Creek relocation and fish passage improvement project defined by Activity // 13. Activity #I6. CIP No. 2 - Sweetwater Creek Fish Passage Improvements • If this project is determined viable based on the investigation of Activity 1112, perform final design, right-of-way/property acquisition and construction of the S\veet\t ater Creek fish passage improvement project defined by Activity 412. Mason Con a t y —Be/fair U Gt1 S t o rm npa t e r i1I an a<S' e m e n t Plan 66 K:\project\ 0700\30784\Reports \ Bel fair S\V/\IP\13elCal rS\V\IP.doc otak Section 8—Costs, Schedule and Implementation Costs. How Much Funding is Needed by When? It is likely that the biggest challenge facing the County in the development and implementation of the Belfair Stormwater Management Plan will be the development of the needed revenue within the required timefranne. Implementation Priorities and Schedule Determine Revenue Needs Although difficult to predict, an attempt has been made to identify the priority and tuning of future activities and capital projects in order that future revenue needs can be established. Total costs over the t\\ enty year capital planning period are estimated to be $1.7M. For this analysis, the twenty year planning period has been divided into two planning periods of 3 and 17 years respectively as shown below. Note that future water quality problems may increase County expenditures under Activity tt14, the cooperative water quality retrofit program. This fmanciql plan would then need to be updated to include the forecasted funding requirements to enhance water quality. Potential Sources of Funding At this point in time, the County is unsure how they will raise the funds needed to support and unplement this proposed Stormwater Management Plan for the Belfair UGA. There are several financial options being considered. These considerations have led to the conclusion that multiple sources of funding may be needed. Funding sources that are currently being considered include: • Formation of a Local Dial nage/Stom/water Improvement aside!, which would have an annual assessment often based on assessed property value, or some other equitable means of establishing value and/or benefit to the various rate payers. • Real Estate Excise Tax (RF_BT) funding, which currently amounts to about $11\4 per year and is currently being used to pay for a number of capital projects throughout the County. • Public Sector .Fundirtg, such as grants and low interest loans from the State (Ecology or the Puget Sound Action Team) or federal government, including federal 319 Water Quality Grants, and the State Public Works Trust Fund and State Revolving Fund. • Formation of a Stormwatcr Uti/it}y (County -wide), where a monthly service fee is assessed to rate payers, often based on the amount of impervious area per parcel, and an incremental portion could be allocated back to the rate payers within the Belfair UGA. • System; Development Chows, where any person moving into an upstream drainage area would be required to pay for a portion of the downstream collection, conveyance, dlason County Belfair UGA Stormwater Management P/an 67 otak li:Aproject \30700\30784\Reports\Belfair SWNIP\13eIfairS\VNIP.doc Section 8—Costs, Schedule and Implementation Continued detention, treatment, and outfall facilities that may be needed to support continued development within the drainage basin. ® SEPA Mitigation .Futile, which would be established on a per development basis, as a project enters and is ultimately approved through the State SEPA review process. ® Purinerzng with prospective developers and land owners, which is especially effective in establishing funding for larger regional drainage facilities. o Other potential, but less likely sources of funding, include: - The County General .Fund - The County Road .Fund - Cost Sharing with UWSDOT • qy potential future road, park,, or utility project could also include some funding for making localized drainage improvements, as defined in advance though this stormwater planning process. From this list of eleven potential sources of funding, the most likely sources of new future funding in relative order of priority are the following: 1. SERA mitigation funding 2. Periodic appropriations from REST funding 3. Public sector funding (grants and loans) 4. Annual stipends from a Belfair or county -wide stormwater utility 5. Partial, periodic funding from future road, park, or utility projects 6. Partnering with developers Future partnering with developers, landowners and WSDOT should assist the County in sharing these regional growth related costs and maintaining the steady, continuous development of the drainage infrasu.ucture needed to support growth throughout the Belfair UGA. • Stormwater Management and Funding Strategy 1 he stormwater management plan proposed for the Belfair UGA has been designed according to the 2005 Ecology Manual. It is based on the latest stormwater modeling and management technology and protocols. The proposed Short -Term activities totaling $200,000 over the next three years is a reasonable level of funding that matches the region's immediate drainage needs It is anticipated that this local funding will be augmented by future grant funds. The proposed Long -Term Plan elements over) ears 4 through 20 total $1,500 000 to enhance Belfair Creek. This amount may increase if fish passage improvements ale found to be needed. Mason Con Belfair UGA Stormmater ?Management Porn 68 otak K:Aproject\30700\30784\Reports\Bel kir S\V NIP \Bel airs\\'\1P.doe Appendix A —Low Impact Development Techniques Appendix A — Low Impact Development Introduction Low Impact Development (LID) is an innovative approach that uses state-of-the-art science and technology to manage urban stormwater by working with the hydrological cycle and its associated natural processes. The goal of LID is to design new development or redevelopment in a way that minimizes the impacts of the new impervious surfaces, its surface water runoff, and its non -point soul ces of pollution sources, in a way that that is consistent with the natural hydrological cycle for the site and the watershed. Using LID, stormwater is managed in a series of small, cost- effective landscape features, similar to existing natural systems, located on each lot rather than being conveyed and managed in larger pond facilities, located at the bottom of the basin. Applicability to Mason County Much of the Mason County Area is largely undeveloped Due to the site -specific nature of LID designs, it is difficult to propose LID site planning on such a large planning level, without conceptual drawings of the proposed developinent(s). Therefore, the intent of this appendix is to introduce general LID concepts, strategies, and case studies in the form of a brief literature review that may be applied within Mason County. LID designs for surface water management generally do not replace needed surface water management detention and water quality treatment facilities; however, they can be used to reduce the size of these facilities. They are also often used to achieve infiltration, water quality enhancement, aquifer recharge, low flow augmentation, and other natural functions that most conventional surface water management facilities are not normally designed to achieve. LID Goals The primary goal of LID is to mimic the predevelopment site hydrology by using site specific design techniques to store, treat, infiltrate, evaporate, and detain runoff. Using these techniques helps to reduce off -site runoff, enhance groundwater recharge, and provide opportunities for improving water quality (Prince George's County, Maryland, 1999). Reported water quality benefits of LID practices are summarized in Table B.1. In general, LID strategies are most effective at removing total suspended solids and metals, followed by biological oxygen demand and bacteria, and finally by the removal of total phosphorous and nitrogen. 1 otak K:\project\30700\30784\Reports\l3elfair SWAMP\LID_Appendix\AppendixA-LID.doc 00/06/07 Appendix A — Low Impact Development Conttnued Table B.1 Reported Pollutant Removal Efficiency of LID Practices Total P Total N Zinc Lead BOD Bacteria TSS LID Practice Bio-retention - 81 43 99 99 - - Dry Well 80-100 40 40 40-60 80-100 80-100 60-80 60-80 Infiltration Trench 80-100 40-60 40-60 80-100 80-100 60-80 60-80 20-100 0-60 0-60 20-100 20-100 0-80 - Filter/Buffer Strip Vegetated 30-65 10-25 0-15 20-50 20-50 - - Swale Infiltration 90 65 50 80-90 80-90 - - Swale Wet Swale 80 20 40 40-70 40-70 - - Reference #4 and #7 By attempting to maintain the pre -development hydrological balance, LID designs often contribute to other environmental benefits. For example, many LID practices incorporate landscape plantings which create habitat features. Landscaping can also be used to attenuate heating -island effects common in many urban areas. Comparison of Conventional and LID Stormwater Management Approaches The fundamental concept of LID design is to treat rainfall on -site through site and building specific designs. One LID design objective is to capture as much rainfall on site as possible, and then return it to its natural hydrologic pathways (i.e. infiltration and evapotranspiration) or reuse it at the source. On the other hand, conventional stormwater management typically routes water to a pond. or infiltration area, often located off site. Table B 2 summarizes how conventional stormwater management and LID can be used to alter or preserve the natural hydrologic regime. 2 otak IC: \project\30700\3078 4\Reports\Belfair SR'MP\LID_Appendix\Append ixA-LID.doc OG/OG/07 Appendix A — Low Impact Development Continued Comparison of Conventional Impacts on and Hydrologic B.2 Stormwater Cycle Management Table the LID Hydrologic Parameter Conventional LID Vegetation/Natural Cover typically into drainage not incorporated designs. used development to maintain hydrology pre - Time of Concentration shortened, product of drainage reduced as efficiency a by -increased approximate conditions where predevelopment possible to Runoff Volume increases in runoff volume controlled conditions to predevelopment Peak Discharge controlled design criteria to predeveloped controlled conditions to fox predeveloped all storms Runoff increased, small, more especially frequent for storms controlled conditions to foi predeveloped all storms Frequency Rainfall (Interception, Depression Abstractions Storage) Infiltration, large elements reduction in all maintained predevelopment to conditions Groundwater Recharge reduction in recharge maintained predevelopment to conditions Reference#1. LID Designs and Practices LID practices to maintain hydrologic functions can include the following: • Impervious Surface Control Devices -alternative pavers, green roof etc. • Infiltration Facilities -dry well, infiltration trench, etc. • Semi -natural Conveyance System—bioretention, grass swale, bioswale, etc. • Storage — cistern, rain barrel • Landscaping - effective grading, installation of plants for water quality and quantity control. Each of these LID practices is briefly described below. Impervious Surface Control Devices Runoff from new impervious surfaces is the primary cause of flooding and stream degradation. Reducing the amount of new impervious surface area in development is one of the most effective methods to achieve a reduction in the total volume of runoff. For example, most residential streets can be as narrow as 22 to 26 feet wide without sacrificing emergency access, on -street parking, or vehicular and pedestrian safety. A shift to narrower streets can result in a 5 to 20 percent overall reduction in impervious area. Reducing road area also reduces paving costs. 3 otak K:Aproject A30700A30 81\Reports\Beltair SVVTIP\LID_Appen ixAAppeulixA-LHD.doe 06/OG/07 Appendix A — Low Impact Development Conttnued Examples of narrow residential street widths from different regions of the country are listed in Table B.3. of Narrow Residential B 3 Street Widths Table Examples State Jur tsdictzon Standard Arizona City of Phoenix 28 feet(parking on both sides) California City of Novato 24 28 feet feet (both (both sides, 2 5 to to 4 15 du du) ) sides, Colorado City of Boulder 20 20 22 26 26 feet feet feet feet feet (150 (no (one (both (one parking, ADT) 350 500 350 350 ADT) — ADT) 1000 1000 ADT) ADT) side, sides, side, — Delaware Delaware DOT 21 feet (one side) Florida City of Orlando 28 22 feet feet (both (both sides, sides, res. res. lots lots <55 >55 feet feet wide) wide) Maine City of Portland 24 feet (one side) Maryland Howard County 24 feet (1000 ADT) Michigan City of Birmingham 26 20 feet feet (both (one side) sides) Montana City of Missoula 26 32 12 feet feet feet (both (both (alley) sides, sides, 3 81— 80 200 du) du) — New Mexico Albuquerque 28 feet (one side) New Jersey 20 28 feet feet (no (one parking, side, 0 0 3500 — 3500 ADT) ADT) — Oregon City of Portland 26 20 feet feet (both (one sides) side) Pennsylvania Bucks County 12 16 20-22 26 28 feet 18 (alley) feet (one (one feet (no (no side, side, parking, parking, 200 200 ADT) 200 1000 200 — ADT) ADT) 1000 ADT) — feet feet — Tennessee City of Johnson City 22 24 feet feet feet (<240 — 28 ADT) feet ADT) — 1500 ADT) (240 28 (>1500 4 otak K:A project \30700A30784\Reports ABelfair SWMP\LID_:AppenthxAAppendix, -LID.doc OG/06/07 Appendix A — Low Impact Development Continued of Narrow B.3 (cont.) Street Widths Table Residential Examples State Jurisdiction Standard Vermont City of Burlington 30 feet (both sides) Washington City of Kirkland 12 20 24 feet feet feet feet (alley) (one (both (both side) sides, sides) low density only) 28 W. Virginia Morgantown 22 feet (one side) Wisconsin City of Madison 27 28 feet feet (both (both sides, sides, <3 3 du/ac) - 10 du/ac) ADT du = dwelling = average daily unit traffic Reference #2 and #3 Other typical LID approaches include alternative roadway layout (Figure B.1) and reduced parking standards (Table B 4) The potential results of impervious surface reduction, or on the overall effective impervious area, are listed in Table B 5 Note how small reductions in the total impervious area can have a relatively large reduction of the amount of on -site impacts and resulting effective impervious area within the watersheds _ GRIDIRON 1 i „1 20,800 FRAGMENTED RARALLEL 19,000 Approximate lineal feet of pavement LOOPS WARPED AND PARALLEL LOWPOPS 16,500 15,300 LOLLIPOPS ONA STICK 15,600 Reference #11 Figure B.1 - Length of pavement of various roadway layout options. K:\Project\30700\3078'l\Reports\3elfair SW\IP\LID_Appendix\Appendix -L1D.doc 06/06/07 5 otak Appendix A - Low Impact Development Continued Conventional Minimum Table B.4 Parking Ratios Land Use Parking Requirement Actual Average Demand Parking Typical Parking Ratio Range Single-family homes 2 spaces per dwelling unit 1.5 - 2.5 1.11 spaces per dwelling unit Shopping center 5 1000 ft2 GFA 4.0 6.5 3.97 per 1000 ft2 GFA spaces per - Convenience store 3.3 spaces pei 1000 ft2 GFA 2.0 - 10.0 Industrial 1.48 per 1000 ft2 GFA 1 space per 1000 ft2 GFA 0.5 - 2.0 Medical/dental office 5.7 spaces per 1000 ft2 GFA 4.5 - 10.0 4.11 per 1000 ft2 GFA GFA = Gross floor area of a building without storage or utility spaces. Reference # 11, #14, and #15 Table B.5 Basin and Site Coverage Assessment Reduction Analysis Results Potential Strategy Impervious Surface Reduction Percentages (%) Site Basinwide -Specific Total Effective Total Effective 1. installing Reduce residential the walks sidewalks on one side by 50 of the percent street by 1.33 1.00 1.59 0.83 only. 2. Reduce residential sidewalks from 5 feet 0.53 0.40 0.64 0.33 width to 4 feet width. 3. a. Reduce feet to 27 local feet. access street widths from 32 2.50 2.00 2.98 3.12 3.50 2.80 4.17 4.37 b. Reduce feet to 25 local feet. access street widths from 32 6.00 4.80 7.15 7.49 Reduce local from 32 c. access street widths feet to 20 feet. 4. a. Reduce commercial parking by 5 percent. 2.67 2.67 1.04 1.37 5.33 5.33 2.09 2.74 b. Reduce commercial parking by 10 percent. c. Reduce commercial parking by 20 percent. 10.67 10.67 4.18 5.47 5. a. Reduce multifamily packing by 5 percent. 0.74 0.74 0.16 0.21 b. Reduce multifamily parking by 10 percent. 1.48 1.48 0.32 0.42 c. Reduce multifamily packing by 20 percent. 2.95 2.95 0.64 0.84 6. a. Reduce multifamily commercial, roof areas industrial, by 10 percent. and 4.25 4.25 1.38 .094 b. Reduce multifamily commercial, roof areas industrial, by 20 percent. and 8.50 8.50 2.76 1.89 Reference #15 6 otak Ii:A project \30700A307&1\Reports VI3elfair SWTIP\LID_Appendix\AppendixA-LID.doc 06/06/07 Appendix A — Low Impact Development Conttnued Alternative Pavers Alternative pavers are permeable or semi -permeable surfaces that can be used for driveways, parking lots, and walkways. Figure B 2 shows typical alternative pavers. The effectiveness of alternative pavers will vary depending on the soil layer underneath. Underlying soils need to have a permeability between 0.5 and 3 0 inches per hour. The City of Seattle gives credit for porous pavement (Table B.6) in computing runoff rates from a developed site. ftVIoJ .. 1% c Course of x- -- (a) Pervious concrete 41ISGf�t7� (c) Unit pavers/bricks/stone poky- f" IG•2 rgeeptio IL (e) Crushed aggregate fang* A, "fr ¢6.ry o- r, rtpet FILTP& catA35E, dr t 6 r)e$'' 7 (b) Porous asphalt Agee7{ n-if Crew) Cam Dori 5oet L (d) Turf block (f) Cobbles Reference #17 Figure B 2 - Alternative Pavers Ii:\project \30700\30 784\Reports\Belfair S\\'\IP\LID ppendix\App en dlxA-LID.doc 0G/06/07 7 otak Appendix A — Low Impact Development Continued Table B 6 Porous Pavement Impervious Surface Reduction Credit SCS Hydrologic Soil Group A B C D Curve Number (without credit) Curve Number (with credit) 98 78 98 85 98 89 98 91 Reference #16 Due to the permeability of porous pavers, there is some risk of contaminating groundwater, although most paving alternatives have some pollutant removal effects through the infiltration process Therefore, they should be located at least two to five feet above the seasonally high groundwater table and at least 100 feet away from drinking water wells1 Other design considerations for alternative pavers are listed as Table B 7 Design Criteria for Alternative B.7 Pavers Table Design Criterion Guidelines Site Take to water check soil table, for boring soil and to permeability depth a depth to bedrock. of at porosity, least 4 feet depth below of seasonally bottom of high pavers Evaluation flat Not recommended as possible. on slopes greater than 5%. Best with slopes as Minimum inches infiltration per hour. rate 3 feet below bottom of pavers: 0.5 Minimum depth to bedrock and seasonally high water table: 4 feet. Minimum setback from water supply wells: 100 feet. downgradient, Minimum setback 30 meters from building (100 feet) foundations: upgiadient. 10 feet Not amounts recommended windblown in areas sediment where wind erosion supplies significant of Drainage area should be less than 15 acres. Traffic Conditions Use access for roads. low -volume automobile parking areas and lightly used Avoid moderate to high traffic areas and significant truck traffic. Avoid of snow sand, cleaning snow salt, removal other operation. deicing Post chemicals with signs to restrict associated the use with and activities. typically 'Please refer to the new draft State Underground Injection Control Rule, 2005. 8 otak K:\project.\30700\3078d\Reports\Belfair SWDIP\L D_Appendix\AppendixA-LID.doc 06/06/07 Appendix A — Low Impact Development Continued Table B.7 (cont.) Design Criteria for Alternative Pavers Design Criterion Guidelines Design Volume Storm Storage Highly variable; depends upon regulatory requirements. Typically design for storm water runoff volume produced in the tributary watershed by the 6-month, 24-hour duration storm event. Drainage Design Storm Time for Minimum 12 hours. Maximum: 72 hours. Recommended: 24 hours. Construction Excavate and grade with light equipment with tracks or oversized tires to prevent soil compaction. As needed, pavement area divert before storm water and during runoff away construction. from planned A layers: typical 1) porous porous pavement asphalt course, cross-section 2-4 inches consists thick; of 2) the filter following aggregate course; 3) reservoir course of 1.5-3-inches of washed rock; and 4) filter fabric Porous Placement Pavement Paving temperature: 240° 260° F. Minimum air temperature: 50° F. Compact with one or two passes of a 10-ton roller. Prevent any vehicular traffic on pavement for at least two days. Pretreatment Pretreatment recommended to treat runoff from off -site areas. For example, place a 25-foot wide vegetative filter strip around the perimeter of the porous pavement where drainage flows onto the pavement surface. Reference #18 Green Roofs Green roof applications can be appropriate for some commercial and multi -family residential lots where the buildings occupy a large portion of the site A layer of absorbent soil on the top of building retains rainfall and allows it to evaporate or transpire from the rooftop vegetation. The runoff from a green roof passes through the absorbent soil layer to an underdrain layer (there is no surface runoff), and therefore, peak runoff iates are attenuated. Green roofs provide multiple benefits such as attenuation of heat island effects which help to save on the energy cost of the building and sound reduction. Green roofs are classed into two categories: extensive green roofs; shallow soil layer of 3 to 7-inch 20-34 lb/square feet weight intensive green roofs; thick soil layer of 8-inch to 8-foot K:\project\30700\30784 2eports\I3elfair S\\'DIP\LID_Appendix\Append xA-LID.doc 00/00/07 9 otak Appendix A — Low Impact Development Continued 80-150 lb/square feet weight Recently, new technologies have made green roofs lighter to reduce the additional cost of supporting structure of the building. Figure B 3 shows typical green roof profiles. Ram or Sprikler Growing Medium Root Barrier Dram Core Separation Fabric Insulation Roof Membrane Structural Support Ram or Sprikler Growing Medium Sand and Gravel Root Barrier Insulation Roof Membrane Structural Support Reference #19 Figure B.3 - Green Roof Profile As the least weight green roof, sedum roof has been tested at many locations. Sedum is diy-tolerant plant that can grow with a thin soil layer (one to two-inch). It reduces the weight of green roof five to eight lb/square feet, eliminating the need for additional structural support. Figure B 4 shows sedum roof profiles and details. Reference #20 Planting mat ......... .. Drainage mat Figure B.4 - Sedum Roof Profile and Detail Studies show that about one -foot of soil depth is needed to achieve the maximum reduction in runoff rate from prolonged winter storms. However, significant reduction in runoff rates from short intense storms that occur during dry weather periods can be achieved with as little as four inches of soil depth. \project\;307U0 \3U78-1 eports \ Betfair SWAIP\ LID_Appendix AAppeixlixA-L] D,doe 06/06/07 I0 otak Appendix A — Low Impact Development Continued The City of Portland gives new green roofs the same credit as forest cover, allowing a curve number of 48 for roof gardens (intensive green roof) and a curve number of 61 for Eco-Roof (extensive green roof). In Germany, 3-inch green roofs have been found to be cost effective, and appreciable runoff will not begin until rainfall amounts exceed 0.6 inch. Infiltration Facilities — Dry Well Dry wells are small, excavated trenches backfilled with aggregate. They function as infiltration systems and are often used to control runoff from building rooftops Dry well designs can be modified to act as catch basins, where they both collect and infiltrate direct surface runoff. Figure B.5 shows a typical detail of a dry well. WILDING FOlINOATION ROOF L .ADER SURCHARGE: PIPE I LTER ABRIC LO&. NIMUM FOOT PLATE St! 8LO<CK in CAP WITH S MIN NU 2' EW TOP LID 3'.121 085ER\AT14h4 WELL BEDROCK OR HIGH WATER TABLE Reference #7 Figure B.5 - Typical Dry Well Section Infiltration Facilities Infiltration Trench An infiltration trench is a shallow excavated trench that has been backfilled with coarse stone aggregate. It can be an underground reservoir of subsurface basin (Figures B.6 and B.7). Stormwater runoff is diverted into the trench and is stored until it can be infiltrated into the soil, usually over a period of several days. Infiltration trenches are a good design option in sandy soils where the depth to the maximum wet -season water table of haldpan is greater than three to six feet. (Note: The new draft of the Washington State Underground Injection Control Rule has specific design recommendations for dry wells based on soil types and risk of aquifer contamination.) IC:\project \30700\30784\Reports\Be]fair S\V1\1 3\ LID. Appendix AAppendlixA-LID-doc00/06/07 otak Reference #21 Appendix A — Low Impact Development Contanued 163mratialcwnalTicn taps akaToole' Wm" Gt d cxdtx Iry _` 50 10 -303 mien cr pent:MO ? %M ClOth InceS tao un Figure B.6 - Subsurface Infiltration Trench Bioretention Bioretention is a water quality and water quantity control practice. It uses the chemical, biological, and physical properties of plants, microbes, and soils for removal of pollutants from stormwater runoff. Bioretention typically is used to treat small (0.25-1.0 acre), highly impervious surfaces such as paiking lots and commercial areas. It is designed to contain an average annual storm event of about 0.5 — 0.7 inches of rainfall (Reference #21). Bioretention consists of grass buffer strips (pretreatment area), ponded area, planting soil, sand bed, organic layer (mulch), and vegetation. A conceptual illustration for a bioretention area is presented in Figure B.8. The bioretention area design provides infiltration and water storage for uptake by vegetation. 12 otak K:\project\30700\3078:1\Reports\Ilelfair SWNIP\LID_Appendix\AppemixA-LID.doc 0G/0G/07 Appendix A — Low Impact Development Contbnued :a a ;o q P okt t --wa washed rook 4" rigid or E" flexible perforated pipe overflow splash block fitter fabric t.44°o ait44 u vo • .A 01 7o Ap614Vo csl fine PROFILE VIEW NTS SECTION A NTS roof drain eto mesh screen oA/water separator C8 Gump w/solid lid compacted backff 4° rigid or e" flexible perforated pipe washed rook 1 1/2"-3/4" Reference #16 Figure B.7 - Underground Infiltration Trench The surface of the planting soil is depressed to allow for ponding of runoff. Collected runoff is infiltrated through a surface organic layer of mulch and/or a ground cover to the planting soil The runoff is stored in the planting soil where it is discharged over a period of days to the native soil underlying the bioretention area. Bioretention areas should be designed as an off-line treatment system. In off-line systems, the "first flush' , which is the most contaminated sheet flow, is retained, and large). flows are bypassed into the normal stoim drain system. Such a design prevents the first flush from being washed out by higher discharges associated with on-line systems Bioretention has many potential side benefits other than water quality treatment. Plantings can improve the aesthetic value of the site as well as providing ecological value, such as improved habitat for small animals, shade, privacy screens, and wind breaks. 13 otak Ii:\Project \30700\30784\Reports\Belfair S\B\SP\LID_Appendix\AppendixA-LID.doc 00/06/0? Appendix A — Low Impact Development Continued Overflow outlet 4 A , Top of vegetated berm Limit of Disturbance Bioretention area limit Grass filter strip recommended length 20 feet Ground cover or mulch layer Sheet flow Grass filter stabilization Limit of pavement Near vertical sidewalis =1 llj1 11 I Sheet flow Minimum freeboard 0.2 feet from maximum ponding depth Maximum ponded water depth (specific to plant soil texture) f A j Plan view (not to scale) •-- Planting soil -- tirillQ;ib r(j'11iin ''j I1 1' uumintitntfn' nr Bioretention area Ground cover or mulch layer IN•SITU Material Saturated Perme abi l i ty Greater than 0.5 inches per hour Section A -A (not to scale) '""% %% Existing edge of pavement ►! I® 5' min. 11 1111 .1111 2-4' min. it 3:1 max. slope Reference #7 Figure B.8 - Plan View and Section of Bioretention Area Cost seduction is another benefit of bioretention facilities. In Prince George's County, Maryland, a case study demonstrated that bioretention can be an economical alternative for providing treatment for the fiist half -inch of runoff from 14 otak ICAproject \30700A30784\Reports\Belfair SWMP\LID_Appendix\AppendixA-J ID.doc 0G/0GI07 Appendix A — Low Impact Development Continued commercial and residential sites. For example, the total estimated cost of a water quality treatment facility for an office building was reduced from $174,000 with oil - grit separators to $111,600 with a bioretention area For other office building sites, evaluated, bioretention practices reduced the amount of storm drainpipe from 800 to 230 feet. Grass Swale Grass swales provide a series of vegetated open channels that are designed specifically to treat and attenuate stormwater runoff. They are best applied on a relatively small scale (generally less than five acres of impervious surface). There are many design variations including dry swales, wet swales, and biofiltration swales. These systems work well along roadways, driveways, and parking lots. • Dry swales are similar in design to bioretention areas. They typically have a sand/soil mix layer that meets minimum permeability required at the bottom of the channel. An underdrain system is also installed under the soil bed. Typically, the underdrain system is created by a gravel layer which encases a perforated pipe. Stormwater treated by the soil bed flows into the underdrain, which conveys treated stormwater back to the storm conveyance system (Figure B 9) Wet swales intersect the groundwater and behave like a linear wetland cell. This design variation incorporates a shallow permanent pool and wetland vegetation to provide stormwater treatment. One disadvantage to the wet swale is that shallow standing water in the swale can cause public nuisance by providing mosquito breeding habitat. A biofiltration swale is similar to a dry swale It is more specifically designed for the treatment of stormwater. The primary pollutant removal mechanisms are filtration by grass blades which enhance sedimentation, trapping, and adhesion of pollutants to the grass and thatch Biofiltration swales generally do not effectively remove dissolved pollutants. Maintaining dense vegetation is the key to its effectiveness. Therefore a swale should receive a minimum of six -hours of sunlight daily during the summer months for healthy grass growth. A swale must dry between storms to maintain vegetation in good condition. For permanent saturated soil conditions, a wet biofiltration swale should be installed. Because typical grass dies when soil saturation exceeds two weeks, vegetation specifically adapted to saturated soil conditions should be used. 15 otak K:Aproject \30 700A30784\Reports\I3elfair SWI\IP\LID_AppendixVAppendixA-LID.doc 06/06/07 Reference #1 Appendix A — Low Impact Development Continued Figure B 9 - Plan View and Section of Dry Swale Grass filter strips are vegetated areas intended to treat sheet flow from adjacent impervious areas Filter strips function by reducing runoff velocities and filtering sediment and other pollutants. With proper maintenance, filter strips can provide relatively high pollutant removal. Grass filter strips require a relatively large amount of space, typically equal to the impervious area they treat. The land requirements for this piactice can be a ciitical drawback in urban environments, where land prices are high. (Reference #1) 16 otak IS \project \30700\30 784\Reports\Belfair S\VMMP\LID_AppencUx\.App@mi nA-Ll D.doc 06/06/07 Appendix A — Low Impact Development Continued Storage Rain barrels and cisterns are low-cost, effective, and easily maintainable storage units applicable to both residential and commercia]industrial site. Rain barrels operate by retaining a predetermined volume of rooftop runoff. In general, cisterns have a larger capacity and are installed either on rooftop or underground. Washington State Department of Ecology's stormwater design manual suggests that cisterns should provide at least 1,000 gallons of storage to have any significant hydrologic effect. Costs and Benefits Conventional and LID stormwater management costs are difficult to compare, because "marginal costs" are rarely defined for either approach. Some case studies and pilot programs show at least a 25 to 30 percent reduction in costs associated with site development, stormwater fees, and maintenance for residential developments that use LID strategies. These savings are achieved by reductions in clearing, grading, pipes, ponds, inlets, curbs, and paving. However, many LID projects have not been fully assessed in the long run due to its early stage in implementation. Some of this basic information is also lacking for conventional stormwater management as well. For instance, the costs to retrofit and repair an entire pipe system after 50 or 60 years are rarely estimated for conventional management. (Reference #8) In addition, costs are site specific Each project will be unique based on the site's soil conditions, topography, existing vegetation, land availability, etc. Some commonly seen cost benefits of LID projects include the following: 1. Multi -functionality —In many projects, LID was originally designed as a landscaped feature before its functionality as a stormwater control was introduced. In these situations, the landscaping and construction costs for stormwater have not been included and financially appear to be free Additionally, the cost of maintaining the landscaped areas is typically included in the project cost and not in the cost of the stormwater system. 2 Lower lifecycle costs —It is important to take into account not just the initial capital costs but also those over the structure's lifetime, which can include operation, repair, maintenance, and decommissioning. Many LID techniques are self-perpetuating, easily repairable, or can be left as natural areas at the end of their functional lifetime, while conventional facilities may require high costs to take out of commission, repair, maintain, and/or replace. 3. Reduced off -site costs —Since LID addresses stormwater trunkline conveyance at its source, it is unlikely to incur major off -site costs in the form of conveyance network or outfalls. Most conventional techniques will require an off -site conveyance network to collect the stormwater from the on -site system, resulting 17 otak Ii:\Project \30700\30784\Reports \IIelfair SWMIP\LID_Appendix\AppencixA-LID.doc 08/00/07 Appendix A — Low Impact Development Continued in additional project costs for the enhancement of downstream systems as urban areas expand 4. Functional use of open space land —LID practices, such as bioretention, can usually be designed as part of the development's open space. Unlike large detention ponds, if these multifunctional LID practices are distributed throughout set -aside open space or previously designated landscaped land they can contribute to a more pack -like and community -friendly setting without incurring any additional costs for land allocation to the drainage system. LID techniques will become less expensive over time as a growing number of competing LID practitioners drive down prices and the technology becomes standard Roofscapes Inc. expects that overall cost of green roof systems to decline by about 25 percent over the next couple of years (Reference #12). Currently, costs of each LID technique are estimated as follows: • Green roof $5.6 to $14 /squaie feet2 • Absorbent landscaping/Bioretention; $2.3 to $6.5 /square feet3 • Dry swale (80 percent bioretention area): $1.8/square feet to $5.2/square feet (Reference #1) • Porous pavement: $2 to $3 /square feet (conventional asphalt costs $0.5 to $1/square feet) • Infiltration facilities . $2.8/square feet to $16/square feet • Manually constructed cisterns (reinforced concrete, size of 3,000 gallons): $1,000 Summary: Applicability of LID to Mason County Due to its natural setting, there will be many opportunities to use LID designs for the management of surface water runoff as the land within Mason County continue to develope. Table B.8 summarizes the applicability of the five major practices of LID design briefly discussed in the above literature review. 2 Extensive roofs are in the lower range, and intensive roofs are in the higher range. A pilot project in the City of White Rock, BC, which has a four -inch deep soil layer, costs about $8.4/square feet than a conventional impervious roof (Reference #5) 3 Sites with six-inch deep absorbent soil layer are in the lower range, and sites with 1.5-foot deep absorbent soil layer in the higher range. 18 otak K:\project\30700\30 784\Reports\Belfair SWnMP\LID_Appendix\AppendixA-LID. doe 06/06/0 i Appendix A — Low Impact Development Continued Potential Applicability of LID within Mason County Table B.8 Practices LID Practice Applicability to Mason County Examples Impervious Control Surface Porous Green Roofs Pavement - - Could design Could design be incorporated be incorporated into into any any building building Infiltration Dry Infiltration Well Trench - Recommended some infiltration. - infiltration attenuation and for rooftop of for conveyance, some storms detention runoff, and some provides provides Facilities Recommended Semi -Natural Conveyance System Bioretention Grass Swale/Biosw Filter ale - - - Include Good treatment. Good with for small for parking landscaping site lots. attenuation where and possible. Strips Storage Cistern Rain Barrel - - Of Could watering limited be use used (unless for some of a dry large season scale). Landscaping of Plants Grading - - Of large Recommend landscape costs to the limited scale. stormwater and provide incorporating natural space benefit aesthetic LID areas unless into to of save look a Effective Use green and site In general, LID strategies can be beneficial and are recommended for future development within Mason County. The greatest attraction of the LID in surface water management design is the ability to better mimic some of the naturally occurring drainage systems. As development occurs, LID strategies could be used to simulate these natural systems. The challenge for the Mason County land owners is to determine which LID strategies should be used and where should they be located. LID designs typically require land, and typically are more costly than conventional drainage designs. Unless they can be incorporated into required landscape and open -space areas, the use of the conventional regional detention and treatment systems may still be the best way for a land owners or developers to optimize the amount of land available for new construction Clearly a reasonable tradeoff will need to be made between costs, availability of land, and the cost and ability to mitigate environmental impacts as development within Mason County continues. 19 otak K:\project\30700\30784\Reports\Belfair SWMP\LIDAppendix\AppenclixA-LlD.doc 06/06/07 • References Appendix A — Low Impact Development Continued 1. Better Site Design Fact Sheet homepage, http://www.stormwatercenter.net 2. Center for Watershed. Protection. 1998 Better Site Design. A Handbook for Changing Development Rules in Your Community. Ellicott City, MD 3. Cohen, A. Narrow Streets Database. Congress for the New Urbanism. Available online at: www.sonic.net/abcaia/narrow htm 4. CRC, 1996; Davis et al. 1997; MWCG, 1987; Urbonas and Stahre, 1993; Yousef et al., 1985; Yu et al., 1992; Yu et al., 1993. 5 Effectiveness of Stormwater Source Control, Greater Vancouver Sewerage & Drainage District, 2002 6. Introduction to LID, Low Impact Development Center Inc., http://www.lid- stormwatei.nethntro/background.htm#1 7 Low -Impact Development Design Strategies, An Integrated Design Approach, Prince George's County, Maryland, 1999 8 Low -Impact Development, Mary Catherine Hager, Stormwater January/February 2003 9. Municipal Guide to Low Impact Development, Low Impact Development Center Inc., http://www.lowimpactdevelopment.org/hd%20articles/Municipal LID.pdf 10. Natural Approach to Stormwater Management, Puget Sound Action Team, March 2003 11. Parking Generation, 2;0 edition. Institute of Transportation Engineers, Washington, DC. 1987. 12. Roofscape Inc., homepage, http://www.roofineadow.com/ 13. SEA Street homepage, Seattle Public Utility, httn://www.seattle.gov/util/SEAStreets/default htm 14. Smith, Thomas. Flexible Parking Requirements Planning Advisory Service Report No.. 377. American Planning Association, Chicago, IL. 40 pp. 1984 20 otak K:Aproject A30700A3078 4\ReportsV13elfair SVPn4P\LID_AppendixAAppenclixA-LID.doc 06/06/07 Appendix A — Low Impact Development Continued 15. Wells, Cedar. Impervious Surface Reduction Technical Study. Draft Report. City of Olympia Public Works Department. Washington Department of Ecology, Olympia, WA. 1994. 16. City of Seattle. Flow Control Technical Guidance Manual, November, 2000. 17. Green Streets. Innovative Solutions for Stormwater and Stream Crossings, Metro June 2002. 18. Stormwater Technology Fact Sheet, Porous Pavement, EPA, September, 1999. 19. Amergreen Roof Garden System, http://www.americanwick.com/pdf/amergreen.pdf. 20. Thin -Layer Roof Top Greening System Using Sedum Carpet, http://www.takenaka.co.initakenaka-e/techno/lolo-sedum/. 21. Schueler, T.R., Controlling Urban Runoff A Practical Manual for Planning and Designing Urban Best Management Practice, Metropolitan Washington Council of Governments. 1987. 22. The Bioretention Manual. Programs and Planning Division, Department of Environmental Resources, Price George's County, Maryland, November 2001. 21 otak IC: AprojectA30700A30784AReports\I3elfair \LID AppendixVAppenilixA-LID.doc 06/00/07 Appendix B Hydrologic Analysis 0 ƒ k CL CC CO1.12 ƒ \ 0 Typical Results Per 1 Acre Developed Footprint incl. access 00000 00000 CO R n © _ 7<oR37 -E �\ 13,8001 \\ \ 19,4001 'c 3 \ z 0> 00000 \\f\\ F««<mm Wet l Volt j Detention4 Top Area incl. Access5 e 54,6001 0 / 72,900 85,100 89,400 3 j 51,600 54,900 \ \ 69,000 COED q§ // <I Active Storage Depth S00CD CD rr Dimensi Erwwww k 31,3001 42,100 45,000 54,500 57,800 Rate Control and Water Quality Volumes for new develol Bot foot' Bottom 125x250 0000 =orCl //\/ /Q/2 7 E 126,600 163,600 1 174,500 00 \ CV 3 & tor Del % 111,900 138,200 147,500 183,400 194,200 / E « Water Quality3 c o WQ Footprint 31,300 42,100 45,0001 54,500 57,800 in c WQ Depth »#nro j/\/\ a » \ Basic Wet Pond / 47,8001 50,900 66,800 68,500 .- > Proposed Condition Land Use Developed Grass Area 7 6.5 co Impervious Area \\`rr/Cr) n</±R CC 0 LY / _ N ck CO Single Family Residential Medium Density Residential Multi Family Residential Mixed Use j Festival Retail 1 Business Industrial (General Commercial General Commercial & Business Industrial Right of way Long Term Agricultural 0 \ MU GC ROW LTA6 0 _mf7 _ ® 0 /3 §»z\ 0 6. LTA results were not calculated. Development in LTA should refer to the Mason County small parcel development guide. K:\project\30700\307841Reports\Belfair SWMP\MGS Appendix\SummaryTables.xls, Proposed \ ƒ \ a\St %§@ >a- ocn uEO \\\ infiltration Ponds Footprint incl. access fa \\/ LC) « Typical Results Acre Develol f�1�. /\\ Itrati 'ond Infiltration Ponds Top Area incl. Access"' 85,100 58,0001 46,500 \ Area at Max El. £ 65,300 42,400 / m Active Storage Depth \rnn 000 Dimensi Bottom footprint \ 54,500 \\ Bottom /\\\ /ac a) E At Active Storage Depth 209,300 / Cr; 101,500 At Riser f 177,000 112,200 85,400 > ƒrr J mmm Total Inflov Volum Hydraulic Conductivity /tre~ aleu uolleali!1u1 Grgo C Proposed Condition Land Use Developed Grass Area \\// ESN snoiAJadwi 7 8.5 gr oa \// 222 \ °•; 2. G0oc 2s > 'E=u=§ -0 at 3 io cc //yam = r •.• m®a= /26c< wawa« :\project\30700\30784\Reports\Belfair SWMP\MGS Appendix\SummaryTables.xls, Prolnfil o bring existing development up to 2005 DOE standards Footprint incl. access NCCS 00 0 0 v r Detention Volume 00 o CC) 0 CO C) Results Develol 0 Wet Pond Volume C 5,500 6,400 U Detention° Top Area incl. Access5 0 0 C) co 0 0 N. CD N • () 0 O 0 P (0 LLI N a) Q Active Storage Depth (ft) 3.00 0 O M Dimensi Bottom footprint t 51,200 61,3001 0 Bottom 0ZEx091. 0 0 At Active Storage Depth 197,300 O O N U v <1 N L. N c o O O O 198, 2001 o •Q Water Quality? tensions WQ Footprint C 51,200 61,300 co eoo n in a) E O Basic Wet Pond S. 55,200 64,300� > Land Use Developed Grass Area � N cr C O Impervious Area oi CO CO 173 O U W Land Use' 0 O Ex BI_80 m x1 W ai N tlJ .� O 4=. 0a) C a) O. O L N 0 co O co C C ca m o 1 > CO -a; Q cl)) E C 2 a) o c 0) m C m 6 > m c o `m0 m ate) 3 c E E a) o 0 to a' • 7 m a) rn m m 0 I— Q O 4.4 • m 4- N O m OS -O 2 a) a) N Q QE O. 2 O. c O N Oco 0 Ca C a) Ct O a) C U c m 0 O O > CO C O L. O N C C _ 0 -p W < 0 < ci4tri K:\project\30700\30784\Reports\Belfair SWMP\MGS_Appendix\SummaryTables.xls, Existing Table 6-1 Hydrologic Modeling Results Rate Control and Water Quality Volumes (2005 DOE) Typical Results Per 1 Acre Developed Proposed Condition Land Use Developed Wet Pond Detention Infiltration Footprint access (cf) incl. Zoning Impervious Area (ac) Grass (ac) Area Volume (cf) Volume (cf) Pond Volume (cf) R-3 3.5 6.5 4 600 11,200 5 500 — R-5 4 6 4,800 13,800 6,900 — R-10 5 5 5,100 14,800 7,300 — MU2 8.5 15 6,700 18,300 8,500 — ROW 9 1 6,900 19,400 8,900 — Ex_BI_60 6 4 5,500 16,700 8,100 — Ex_BI_80 8 2 6,400 19,800 — 9,400 MU(0.5) 8.5 1.5 6,300 17,700 8,500 — MU(1.0) 8.5 1.5 6,300 11,200 5,800 — MU(2.0) 8.5 1.5 6,300 8 500 4,700 — Zoning Classifications R-3 Single Family Residents, R-5 Medium Density Reside R-10 Multi Family Residential MU Mixed Use EX BI 60 Existing BI 60% Impervi EX BI 80 Existing BI 80% Impervi K:\project\30700\30784\Reports\Belfair SWMP\MGS Appendix\SummaryTables.xls, Table 6-1 Results MGS FLOOD PROJECT REPORT Program Version: 3.12 Run Date: 05/08/2007 4:33 PM Input File Name: Project Name. Analysis Title: Comments: ROWTiII.fld Belfair SWMP Right of Way (ROW) Till 90% Maximum impervious coverage allowable ********** Precipitation Input********** Precipitation Station Data Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station 455549 Montesano Evaporation Station . 456803 Puyallup At Site 25-Year, 24-Hour Precipitation (inches): 4.80 Gage 25-Year, 24-Hour Precipitation (inches) : 5.46 Precipitation Scale Factor : 0.878 Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default 10/01 /1954-10/01 /1999 ********** Default HSPF Parameters Used (Not Modified by User) *************** Number of Subbasins: 1 ***Tributary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasin Total Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Lateral 1 Lateral 2 ********** Watershed Definition ********** ********** Subbasin Number: 1 ********** Predeveloped 10.000 O .000 O .000 0.000 0.000 O .000 O .000 O .000 10.000 Area(Acres) Developed To Node Bypass Node 0.000 0.000 O .000 1.000 O .000 O .000 0.000 0.000 9.000 10.000 O .000 0.000 O .000 0.000 O .000 O .000 O .000 O .000 Lateral Flow Connnections Predeveloped Surface Interflow Grnd Water Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Surface Node Node Node Node Node Node Node Node Developed Interflow Grnd Water Node Node Node Node Node Node Node ROWTi11RPT.rtf 1 of 4 ***Subbasin Connection Summary*** S ubbasin 1 > Node 1 *** By -Pass Area Connection Summary *** N o By -Passed Areas in Watershed U pstream Node No. Node 1 *** Postdeveloped Node Connection Summary Link Type Downstream Node Pond Node 2 P redeveloped Compliance Node: Postdeveloped Compliance Node. Link No. 1, Pond: Pond 1 *** Predeveloped Structure Summary*** None *** Postdeveloped Structure Summary*** U pstream Node: 1, Downstream Node Prismatic Pond Option Used Pond Floor Elevation Riser Crest Elevation Max Pond Elevation Max Storage Depth Pond Bottom Length Pond Bottom Width Pond Side Slopes Pond Bottom Area Area at Riser Crest El Volume at Riser Crest Area at Max Elevation Vol at Max Elevation Hydraulic Conductivity Depth to Water Table Riser Geometry Riser Structure Type Riser Diameter Common Length Riser Crest Elevation 2 : 100.00ft : 103.10ft : 103 50ft 3.10 ft . 340.0 ft 170.0 ft : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 ft/ft : 57800. sq-ft : 67,632. sq-ft 1.553 acres 194,220. 4.459 68951. 1.583 acres 221,528. 5.086 ac-ft 0.00 100.00 : Circular : 24.00 in : 0.170 ft : 103.10 ft Hydraulic Structure Geometry Number of Devices: 2 ---Device Number 1 --- Device Type Invert Elevation Diameter Orientation Elbow : Circular Orifice : 100.00 ft : 3.00 in Horizontal : No --- Device Number 2 --- Device Type : Vertical Rectangular Orifice Invert Elevation Length Height Orientation Elbow : 102.00 ft : 2.00 in : 18.00 in : Vertical : No cu-ft ac-ft sq-ft cu-ft ft/dy ft ROWTi11RPT.rtf 2 of 4 ***********Postdeveloped Hydraulic Rating Table************* Postdeveloped Pond Water Surface Elevation Statistics Postdeveloped Water Surface Elevation Data (ft) Recurrence Interval Computed Using Gringorten Plotting Position Tr (yrs) Link: 1 ** 1.05-Year 1.11-Year 1.25-Year 2.00-Year 3.33-Year 5-Year 10-Year 25-Year 50-Year 100-Year Record too 101.215 101.534 101.679 102.100 102.509 102.653 102.793 102.850 102.877 ** Short to Compute Peak WSEL for These Recurrence Intervals Postdeveloped Infiltrated Water Statistics Volume Statistics Computed for Entire Simulation Statistic Link: 1 Total Inflow Volume (ac-ft) Total Volume Infiltrated (ac-ft) Percent Infiltrated Node No: 1 1921. 0.00 % ***********Water Quality Facility Data ************* Basic Wet Pond Volume (91% Exceedance): 68508. oil-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 102762. cu-ft 2-Year Discharge Rate : 3.591 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 1.88 cfs Off-line Design Discharge Rate (91% Exceedance): 1.07 cfs Computed Flow Sputter Data Orifice Diameter 5 00 inches Baffle Wall Height (WQ Design Depth): 2.50 feet Baffle Wall (Weir) Length: 3.47 feet (41 7 inches) Ratio: WQ Depth/Orifice Diameter: 6.0 (>=2 PASS) Node No: 2 Basic Wet Pond Volume (91 % Exceedance): 25603. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume. 38405. cu-ft 2-Year Discharge Rate : 0.364 cfs ROWT111RPT.rtf 3 of 4 ***********Compliance Point Results ************* P redeveloped Compliance Node: 1 P ostdeveloped Compliance Node: 2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ** 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Record too Short 0.680 0.862 0.975 1.057 1.168 * * * * to Compute Peak 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Discharge for These 0.364 0.628 O .714 O .750 O .867 * * * * Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped Y%Q2 (Must be Less Than 0%): Maximum Excursion from YZQ2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): - 35.2% PASS - 35.2% PASS - 10.0% PASS 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS ROWTi11RPT.rtf 4 of 4 MGS FLOOD PROJECT REPORT Program Version: 3.12 Run Date: 05/15/2007 1:46 PM Input File Name. Project Name: Analysis Title: Comments: ExB160_T.fld Belfair SWMP EX_BI TiII 60% impervious existing business -industrial ********** Precipitation Input********** Precipitation Station Data Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station 455549 Montesano 10/01/1954-10/01/1999 Evaporation Station : 456803 Puyallup At Site 25-Year, 24 Hour Precipitation (inches): 4.80 Gage 25-Year, 24-Hour Precipitation (inches) : 5.46 Precipitation Scale Factor : 0.878 Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *"**"********** Number of Subbasins: 1 ***Tributary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasin Total Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Lateral 1 Lateral 2 ********** Watershed Definition ********** ********** Subbasin Number: 1 ********** Predeveloped 10.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 10.000 Area(Acres) Developed To Node Bypass Node 0.000 0 000 0.000 4.000 0.000 0.000 0.000 0.000 6.000 10.000 0 000 0 000 0 000 O 000 O 000 O 000 0 000 0 000 Lateral Flow Connnections Predeveloped Developed Surface Interflow Grnd Water Surface Interflow Grnd Water Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node ExBI60 TRPT.rtf 1 of 4 ***Subbasin Connection Summary*** S ubbasin 1 > Node 1 *** By -Pass Area Connection Summary *** N o By -Passed Areas in Watershed U pstream Node No. N ode 1 *** Postdeveloped Node Connection Summary*** Link Type Downstream .Node Pond Node 2 Predeveloped Compliance Node: Postdeveloped Compliance Node: L ink No. 1, Pond: R-3 Pond 1 2 *** Predeveloped Structure Summary*** none *** Postdeveloped Structure Summary*** Upstream Node : 1, Downstream Node: 2 Prismatic Pond Option Used Pond Floor Elevation Riser Crest Elevation Max Pond Elevation Max Storage Depth Pond Bottom Length Pond Bottom Width Pond Side Slopes Pond Bottom Area Area at Riser Crest El Volume at Riser Crest Area at Max Elevation Vol at Max Elevation Hydraulic Conductivity Depth to Water Table Riser Geometry Riser Structure Type Riser Diameter Common Length Riser Crest Elevation • • • • • • • • • • • 100.00ft 103.00ft 103.50ft 3.00 ft 320.0 ft 160.0 ft : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 ft/ft : 51200. sq-ft : 60,164. sq-ft 1.381 acres : 166,865. cu-ft : 3.831 ac-ft : 61721. sq-ft . 1.417 acres : 197,325. cu-ft : 4.530 ac-ft 0.00 ft/dy 100.00 ft : Circular : 24.00 in : 0.190 ft : 103.00 ft Hydraulic Structure Geometry N umber of Devices: 2 ---Device Number 1 --- Device Type : Circular Orifice Invert Elevation : 100.00 ft Diameter : 3.10 in Orientation : Horizontal Elbow : No --- Device Number 2 --- Device Type : Vertical Rectangular Orifice Invert Elevation Length Height Orientation Elbow : 102.00 ft : 2.70 in : 18.00 in : Vertical : No *** Post -Developed Link Statistics *** ExBI60 TRPT.rtf 2 of 4 Postdeveloped Water Surface Elevation Data (ft) Recurrence Interval Computed Using Gringorten Plotting Position Tr(yrs) Link: 1 ** 1.05-Year 1.11-Year 1.25-Year 2.00-Year 3.33-Year 5-Year 10-Year 25-Year 50-Year 100-Year Record too 101.039 101.194 101.391 101.842 102.225 102.385 102.480 102.544 102.669 ** Short to Compute Peak WSEL for These Recurrence Intervals Postdeveloped Infiltrated Water Statistics Volume Statistics Computed for Entire Simulation Statistic Link: Total Inflow Volume (ac-ft) Total Volume Infiltrated (ac-ft) Percent Infiltrated Node No: 1 1 1709. 0. 0.00 % ***********Water Quality Facility Data ************* Basic Wet Pond Volume (91 % Exceedance): 55184. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 82776. cu-ft 2-Year Discharge Rate : 2.980 cfs 15-Minute Timestep Water Quality Treatment Design Discharge On-line Design Discharge Rate (91 % Exceedance): 1.32 cfs Off-line Design Discharge Rate (91 % Exceedance): 0 73 cfs Computed Flow Splitter Data Orifice Diameter: 4 00 inches Baffle Wall Height (WQ Design Depth): 2.79 feet Baffle Wall (Weir) Length: 2.77 feet (33 2 inches) Ratio: WQ Depth/Onfice Diameter: 8.4 (>=2 PASS) Node No: 2 Basic Wet Pond Volume (91 % Exceedance): 25703. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume. 38554. cu-ft 2-Year Discharge Rate : 0.348 cfs ExBI60 TRPT.rtf 3 of 4 ***********Compliance Point Results ************* Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Tr (Years) Discharge (cfs) Postdevelopment Runoff Tr (Years) Discharge (cfs) ** 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Record too Short 0.680 O .862 O .975 1.057 1.168 * * * * to Compute Peak 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Discharge for These 0.348 0.539 0.603 0.663 0.774 * * * * Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped 1/2Q2 (Must be Less Than O%): Maximum Excursion from %Q2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be Tess than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): -27.9% -27.9% -56.2% 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS PASS PASS PASS bxBI60 TRPT.rtf 4 of 4 MGS FLOOD PROJECT REPORT Program Version: 3.12 Run Date: 05/15/2007 1:57 PM Input File Name. Project Name: Analysis Title: Comments: ExBI80_T.fld Belfair SWMP EX_BI Till 80% impervious existing business -industrial ********** Precipitation Input********** Precipitation Station Data Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station : 455549 Montesano 10/01/1954-10/01/1999 Evaporation Station : 456803 Puyallup At Site 25-Year, 24-Hour Precipitation (inches): 4.80 Gage 25-Year, 24-Hour Precipitation (inches) : 5.46 Precipitation Scale Factor : 0.878 Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** Number of Subbasins: 1 ***Tributary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasin Total Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Lateral 1 Lateral 2 ********** Watershed Definition ********** ********** Subbasin Number: 1 ********** Predeveloped 10.000 0.000 o .000 0.000 o:o o O .000 O .000 O .000 10.000 Area(Acres) Developed To Node Bypass Node 0.000 0 000 0.000 2.000 0.000 0.000 0.000 0.000 8.000 10.000 0 000 0.000 0.000 0.000 O .000 O .000 0.000 0.000 Lateral Flow Connnections Predeveloped Developed Surface Interflow Grnd Water Surface Interflow Grnd Water Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node ExBI80 JRPT.rtf 1 of 4 i'*'t Post -Developed Link Statistics Postdeveloped Water Surface Elevation Data (ft) Recurrence Interval Computed Using Gringorten Plotting Position Tr (yrs) Link: 1 ** *** 1.05-Year 101.112 1.11-Year 101.358 1.25-Year 101.530 2.00-Year 101.893 3.33-Year 102.235 5-Year 102.345 10-Year 102.484 25-Year 102.534 50-Year 102.601 100-Year ** Record too Short to Compute Peak WSEL for These Recurrence Intervals Postdeveloped Infiltrated Water Statistics Volume Statistics Computed for Entire Simulation Statistic Link: 1 Total Inflow Volume (ac-ft) 1850. Total Volume Infiltrated (ac-ft) 0. Percent Infiltrated 0.00 % ***********Water Quality Facility Data ************* Node No: 1 Basic Wet Pond Volume (91 % Exceedance): 64318. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume. 96477. cu-ft 2-Year Discharge Rate : 3.385 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 1.69 cfs Off-line Design Discharge Rate (91% Exceedance): 0.95 cfs Computed Flow Splitter Data Orifice Diameter: 4 00 inches Baffle Wall Height (WQ Design Depth): 4.80 feet Baffle Wall (Weir) Length: 1.44 feet (17.3 inches) Ratio: WQ Depth/Onfice Diameter 14.4 (>=2 PASS) Node No: 2 Basic Wet Pond Volume (91% Exceedance): 24705. cu-ft Computed Large Wet Pond Volume, 1 .5*Basic Volume. 37057. cu-ft 2-Year Discharge Rate : 0.384 cfs ExBI8O_TRPT.rtf 3 of 4 ***********Compliance Point Results ************* Predeveloped Compliance Node: Postdeveloped Compliance Node: 1 2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Tr (Years) Discharge (cfs) Postdevelopment Runoff Tr (Years) Discharge (cfs) ** 2-Year 0.680 2-Year 5-Year 0.862 5-Year 10-Year 0.975 10-Year 25-Year 1.057 25-Year 50-Year 1.168 50-Year 100-Year ** 100-Year 200-Year ** 200-Year Record too Short to Compute Peak Discharge for These O .384 O .625 O .717 0.754 0.859 * * * * Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped'AZQ2 (Must be Less Than 0%): Maximum Excursion fromYZQ2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%)• Percent Excursion from Q2 to Q50 (Must be less than 50%): - 29.5% PASS - 29.5% PASS -8.3% PASS 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS ExBI80 TRPT.rtf 4 of 4 MGS FLOOD PROJECT REPORT Program Version: 3.12 Run Date: 05/18/2007 2:34 PM Input File Name. Project Name: Analysis Title: Comments - infiltration of 1"/hr MU_Infil_1_O.fld Belfair SWMP Mixed Use (MU) Outwash - Infiltration 85% Maximum impervious coverage allowableAssumed conservative ********** Precipitation Input********** Precipitation Station Data Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station 455549 Montesano Evaporation Station : 456803 Puyallup At Site 25-Year, 24 Hour Precipitation (inches): 4.80 Gage 25-Year, 24-Hour Precipitation (inches) 5.46 Precipitation Scale Factor : 0.878 Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default 10/01 /1954-10/01 /1999 ********** Default HSPF Parameters Used (Not Modified by User) *************** ********** Watershed Definition ********** ********** Subbasin Number: 1 ********** Number of Subbasins: 1 ***Tributary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasin Total Till Forest Till Pasture Till Grass Outwash Outwash Outwash Wetland Impervious L ateral 1 L ateral 2 Forest Pasture Grass Predeveloped 0.000 0.000 O .000 10.000 O .000 0.000 0.000 0.000 10.000 Area(Acres) Developed To Node Bypass Node O .000 0 000 O .000 O .000 0.000 0.000 1.500 0.000 8.500 10.000 0 000 0 000 0 000 0 000 0 000 0 000 0 000 0 000 Lateral Flow Connnections Predeveloped Surface Interflow Grnd Water Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Developed Surface Interflow Grnd Water Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node MU Infil 1 ORPT.rtf 1 of 4 ***Subbasin Connection Summary*** Subbasin 1 > Node 1 *** By -Pass Area Connection Summary *** No By -Passed Areas in Watershed *** Postdeveloped Node Connection Summary*** U pstream Node No. Link Type Downstream Node N ode 1 Pond Node 2 P redeveloped Compliance Node: 1 Postdeveloped Compliance Node: 2 *** Predeveloped Structure Summary*** None *** Postdeveloped Structure Summary*** Link No. 1, Pond: MU Infil-Pond Upstream Node : 1, Downstream Node: 2 P rismatic Pond Option Used Pond Floor Elevation Riser Crest Elevation Max Pond Elevation Max Storage Depth Pond Bottom Length Pond Bottom Width Pond Side Slopes Pond Bottom Area Area at Riser Crest El Volume at Riser Crest Area at Max Elevation Vol at Max Elevation Hydraulic Conductivity Depth to Water Table Riser Geometry Riser Structure Type Riser Diameter Common Length Riser Crest Elevation : 100.00ft : 103.00ft : 103.50ft . 3.00 ft : 260.0 ft : 130.0 ft : L1= 3.00 L2= 3.00 W 1= 3.00 W2= 3.00 ft/ft : 33800. sq-ft : 41,144. sq-ft 0.945 acres : 112,236. cu-ft : 2.577 ac-ft : 42431. sq-ft 0.974 acres : 133,118. cu-ft : 3.056 ac-ft . 2.00 ft/dy . 100.00 ft : Circular : 24.00 in : 0.000 ft : 103.00 ft Hydraulic Structure Geometry N umber of Devices: 0 MU Infil 1 ORPT.rtf 2 of 4 *** Post -Developed Link Statistics *** Postdeveloped Water Surface Elevation Data (ft) Recurrence Interval Computed Using Gringorten Plotting Position Tr(yrs) Link: 1 ** 1.05-Year 1.11-Year 1.25-Year 2.00-Year 3.33-Year 5-Year 10-Year 25-Year 50-Year 100-Year Record too 101.060 101.079 101.157 101.590 102.230 102.382 102.663 102.838 102.920 ** Short to Compute Peak WSEL for These Recurrence Intervals Postdeveloped Infiltrated Water Statistics Volume Statistics Computed for Entire Simulation Statistic Link: Total Inflow Volume (ac-ft) Total Volume Infiltrated (ac-ft) Percent Infiltrated Node No: 1 1 1698. 1698. 100.00 % ***********Water Quality Facility Data ************* Basic Wet Pond Volume (91 % Exceedance): 63344. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume. 95016. cu-ft 2-Year Discharge Rate : 3.390 cfs 15-Minute Timestep Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 1.79 cfs Off-line Design Discharge Rate (91% Exceedance): 1.03 cfs Computed Flow Splitter Data Orifice Diameter: 4 00 inches Baffle Wall Height (WQ Design Depth): 5.62 feet Baffle Wall (Weir) Length: 1.09 feet (13.1 inches) Ratio: WQ Depth/Onfice Diameter: 16.9 (>=2 PASS) Node No: 2 2-Year Discharge Rate : 0.000 cfs MU Infil I ORPT.rt.f 3 of 4 ***********Compliance Point Results ************* Predeveloped Compliance Node: 1 Postdeveloped Compliance Node 2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ** 2-Year 0.047 2-Year 1.590E-05 5-Year 0.149 5-Year 2.379E-05 10-Year 0.277 10-Year 2.663E-05 25-Year 0.455 25-Year 2.852E-05 50-Year 0.511 50-Year 2.869E-05 100-Year ** 100-Year ** 200-Year ** 200-Year ** Record too Short to Compute Peak Discharge for These Recurrence Intervals ** Point of Compliance Flow Duration Data *** **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped'/2Q2 (Must be Less Than 0%): Maximum Excursion from%%Q2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS O.O% PASS 0.0% PASS 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS MU Infil 1 ORPT.rtf 4 of 4 MGS FLOOD PROJECT REPORT Program Version: 3.12 Run Date: 05/18/2007 2:37 PM Input File Name. Project Name. Analysis Title: Comments* infiltration of 2"/hr MU_Infil_2_O.fld Belfair SWMP Mixed Use (MU) Outwash - Infiltration 85% Maximum impervious coverage allowableAssumed conservative ********** Precipitation Input********** Precipitation Station Data Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station 455549 Montesano Evaporation Station : 456803 Puyallup At Site 25-Year, 24-Hour Precipitation (inches): 4.80 Gage 25-Year, 24-Hour Precipitation (inches) : 5.46 Precipitation Scale Factor : 0 878 Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default 10/01 /1954-10/01 /1999 ********** Default HSPF Parameters Used (Not Modified by User) *************** Number of Subbasins: 1 ***Tributary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasin Total Till Forest Till Pasture Till Grass Outwash Outwash Outwash Wetland Impervious Lateral 1 Lateral 2 Forest Pasture Grass ********** Watershed Definition ********** ********** Subbasin Number: 1 ********** Predeveloped 0.000 0.000 0.000 10.000 0.000 0.000 0.000 0.000 10.000 Area(Acres) Developed To Node Bypass Node 0.000 0 000 0.000 0 000 O .000 0 000 O .000 0 000 O .000 0 000 1.500 0 000 O .000 0 000 8.500 0 000 10.000 0.000 Lateral Flow Connnections Predeveloped Developed Surface Interflow Grnd Water Surface Interflow Grnd Water Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node MU Infi1 2 ORPT.rtf 1 of 3 ***Subbasin Connection Summary' S ubbasin 1 > Node 1 *** By -Pass Area Connection Summary *** No By -Passed Areas in Watershed *** Postdeveloped Node Connection Summary *" U pstream Node No. Link Type Downstream Node Node 1 Pond Node 2 Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 2 *** Predeveloped Structure Summary *** None *** Postdeveloped Structure Summary *** Link No, 1, Pond: MU Infil-Pond Upstream Node : 1, Downstream Node: 2 Prismatic Pond Option Used Pond Floor Elevation Riser Crest Elevation Max Pond Elevation Max Storage Depth Pond Bottom Length Pond Bottom Width Pond Side Slopes Pond Bottom Area Area at Riser Crest El Volume at Riser Crest Area at Max Elevation Vol at Max Elevation Hydraulic Conductivity Depth to Water Table Riser Geometry Riser Structure Type Riser Diameter Common Length Riser Crest Elevation : 100.00ft 103.00ft : 103.50ft 3.00ft : 230.0 ft 110.0 ft : L1= 3.00 L2= 3.00 W 1= 3.00 W2= 3.00 ft/ft : 25300. sq-ft : 31,744. sq-ft . 0.729 acres : 85,383. cu-ft : 1.960 ac-ft : 32881. sq-ft . 0.755 acres : 101,527. cu-ft : 2.331 ac-ft . 4.00 ft/dy . 100.00 ft : Circular : 24.00 in : 0.000 ft : 103.00 ft Hydraulic Structure Geometry N umber of Devices: 0 *** Post -Developed Link Statistics Postdeveloped Water Surface Elevation Data (ft) Recurrence Interval Computed Using Gringorten Plotting Position Tr (yrs) Linty 1 1.05-Year 1.11-Year 1.25-Year 2.00-Year 3.33-Year 5-Year 10-Year 25-Year 50-Year 100-Year ** Record too 100.841 100.888 100.989 101.425 101.856 102.059 102.435 102.758 102.909 ** Short to Compute Peak *** WSEL for These Recurrence Intervals MU Infil 2 ORPT.rtf 2 of 3 Postdeveloped Infiltrated Water Statistics Volume Statistics Computed for Entire Simulation S tatistic Link: 1 Total Inflow Volume (ac-ft) 1698. Total Volume Infiltrated (ac-ft) 1698. P ercent Infiltrated 100.00 % ***********Water Quality Facility Data ************* N ode No: 1 Basic Wet Pond Volume (91 % Exceedance): 63344. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume. 95016. cu-ft 2-Year Discharge Rate : 3.390 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 1.79 cfs Off-line Design Discharge Rate (91% Exceedance): 1.03 cfs Computed Flow Splitter Data Orifice Diameter: 4.00 inches Baffle Wall Height (WQ Design Depth): 5.62 feet Baffle Wall (Weir) Length: 1.09 feet (13.1 inches) Ratio: WQ Depth/Orifice Diameter: 16.9 (>=2 PASS) N ode No: 2 2-Year Discharge Rate : 0.000 cfs ***********Compliance Point Results ************* Predeveioped Compliance Node: 1 Postdeveloped Compliance Node: 2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gnngorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ** 2-Year 0.047 2-Year 1.429E-05 5-Year 0.149 5-Year 2.055E-05 10-Year 0.277 10-Year 2.442E-05 25-Year 0.455 25-Year 2.803E-05 50-Year 0.511 50-Year 2.866E-OS 100-Year ** 100-Year ** 200-Year ** 200-Year ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped%ZQ2 (Must be Less Than 0%): Maximum Excursion from%Q2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS 0.0% PASS 0.0% PASS 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS MU Inf1 2 ORPT.rtf 3 of 3 MGS FLOOD PROJECT REPORT Program Version: 3.12 Run Date: 05/18/2007 2:29 PM Input File Name. MU_Infil_.5_O.fld Project Name. Be[fair SWMP Analysis Title: Mixed Use (MU) Outwash - Infiltration Comments- 85% Maximum impervious coverage allowableAssumed conservative infiltration of 0.5"/hr based on DOE'05 ********** Precipitation Input********** Precipitation Station Data Selected Climatic Region Number 16 Full Period of Record Available used for Routing Precipitation Station 455549 Montesano Evaporation Station : 456803 Puyallup At Site 25-Year, 24 Hour Precipitation (inches): 4.80 Gage 25-Year, 24-Hour Precipitation (inches) : 5.46 Precipitation Scale Factor : 0.878 Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default 10/01 /1954-10/01 /1999 ********** Default HSPF Parameters Used (Not Modified by User) *************** Number of Subbasins: 1 ***Tributary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasin Total Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Lateral 1 Lateral 2 ********** Watershed Definition ********** ********** Subbasin Number: 1 ********** Predeveloped 0.000 O .000 O .000 10.000 O .000 O .000 0.000 0.000 10.000 Area(Acres) Developed To Node Bypass Node O .000 0 000 0.000 0 000 O .000 0 000 0.000 0 000 0.000 0 000 1.500 0 000 0.000 0 000 8.500 0 000 10.000 0.000 Lateral Flow Connnections Predeveloped Surface Interflow Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Developed Grnd Water Surface Interflow Grnd Water Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node MU Infil .5 ORPT.rtf 1 of 3 ***Subbasin Connection Summary*** Subbasin 1 > Node 1 *** By -Pass Area Connection Summary *** N o By -Passed Areas in Watershed *** Postdeveloped Node Connection Summary*** U pstream Node No. Link Type Downstream Node Node 1 Pond Node 2 Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 2 ***Predeveloped Structure Summary *** None *** Postdeveloped Structure Summary *** Link No. 1, Pond: MU Infil-Pond Upstream Node : 1, Downstream Node: 2 Prismatic Pond Option Used Pond Floor Elevation Riser Crest Elevation Max Pond Elevation Max Storage Depth Pond Bottom Length Pond Bottom Width Pond Side Slopes Pond Bottom Area Area at Riser Crest El Volume at Riser Crest Area at Max Elevation Vol at Max Elevation Hydraulic Conductivity Depth to Water Table Riser Geometry Riser Structure Type Riser Diameter Common Length Riser Crest Elevation : 100.00ft : 103.00ft : 103.50ft 3.00ft 330.0ft . 165.0 ft : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 ft/ft sq-ft sq-ft 54450. 63,684. 1.462 acres 177 020. cu-ft 4.064 ac-ft 65286. sq-ft 1.499 acres 209 251. cu-ft 4.804 ac-ft 1.00 ft/dy 100.00 ft : Circular : 24.00 in : 0.000 ft : 103.00 ft Hydraulic Structure Geometry N umber of Devices: 0 *** Post -Developed Link Statistics *** Postdeveloped Water Surface Elevation Data (ft) Recurrence Interval Computed Using Gringorten Plotting Position Tr (yrs) Links 1 ** 1.05-Year 1.11-Year 1.25-Year 2.00-Year 3.33-Year 5-Year 10-Year 25-Year 50-Year 100-Year Record too 100.879 100.974 101.175 101.613 102.143 102.204 102.450 102.772 102.744 ** Short to Compute Peak WSEL for These Recurrence Intervals MU Infil .5 ORPT.rtf 2 of 3 Postdeveloped Infiltrated Water Statistics Volume Statistics Computed for Entire Simulation Statistic Link; 1 Total Inflow Volume (ac-ft) 1698. Total Volume Infiltrated (ac-ft) 1698. Percent Infiltrated 100.00 35 ***********Water Quality Facility Data ************* Node No: 1 Basic Wet Pond Volume (91 % Exceedance): 63344. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume. 95016. cu-ft 2-Year Discharge Rate : 3.390 cfs 15-Minute Timestep Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 1.79 cfs Off-line Design Discharge Rate (91% Exceedance): 1 03 cfs Computed Flow Splitter Data Orifice Diameter: 4 00 inches Baffle Wall Height (WQ Design Depth): 5.62 feet Baffle Wall (Weir) Length: 1.09 feet (13.1 inches) Ratio: WQ Depth/Orifice Diameter: 16.9 (>=2 PASS) Node No: 2 Basic Wet Pond Volume (91% Exceedance): 2. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume. 2. cu-ft 2-Year Discharge Rate : 0.000 cfs *****Compliance Point Results ************* Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 2 ***Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ** 2-Year 0.047 2-Year 1.616E-05 5-Year 0.149 5-Year 2.217E-05 10-Year 0.277 10-Year 2.451E-05 25-Year 0.455 25-Year 2.770E-05 50-Year 0.511 50-Year 2.872E-05 100-Year ** 100-Year ** 200-Year ** 200-Year ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped 1AQ2 (Must be Less Than 0%): Maximum Excursion from'/4Q2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS 0.0% PASS 0.0% PASS 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS MU 1nfi1 .5 ORPT.rtf 3 of 3 MGS FLOOD PROJECT REPORT Program Version: 3.12 Run Date: 05/08/2007 1:28 PM Input File Name. Project Name: Analysis Title: Comments: R3Till.fld Belfair SWMP R-3 Till 35% Maximum impervious coverage allowable ********** Precipitation Input********** Precipitation Station Data Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station : 455549 Montesano 10/01/1954-10/01/1999 Evaporation Station : 456803 Puyallup At Site 25-Year, 24-Hour Precipitation (inches): 4.80 Gage 25-Year, 24-Hour Precipitation (inches) : 5.46 Precipitation Scale Factor 0.878 Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *"*"*********** Number of Subbasins: 1 ***Tributary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasin Total Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Lateral 1 Lateral 2 ********** Watershed Definition ********** ********** Subbasin Number: 1 ********** Predeveloped 10.000 0.000 0.000 0.000 O .000 O .000 O .000 O .000 10.000 Area(Acres) Developed To Node Bypass Node O .000 0 000 O .000 6.500 0.000 0.000 0.000 0.000 3.500 10.000 O 000 O 000 0 000 0 000 O 000 O 000 0 000 O .000 Lateral Flow Connnections Predeveloped Developed Surface Interflow Grnd Water Surface Interflow Grnd Water Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node R3Ti11RPT.rtf 1 of 4 *** Subbasin Connection Summary*** S ubbasin 1 > Node 1 *** By -Pass Area Connection Summary *** No By -Passed Areas in Watershed *** Postdeveloped Node Connection Summary*** U pstream Node No. Link Type Downstream Node Node 1 Pond Node 2 P redeveloped Compliance Node: 1 P ostdeveloped Compliance Node: 2 *** Predeveloped Structure Summary*** None *** Postdeveloped Structure Summary*** Link No. 1 Pond: R-3 Pond U pstream Node : 1, Downstream Node: 2 P rismatic Pond Option Used Pond Floor Elevation Riser Crest Elevation Max Pond Elevation Max Storage Depth Pond Bottom Length Pond Bottom Width Pond Side Slopes Pond Bottom Area Area at Riser Crest El Volume at Riser Crest Area at Max Elevation Vol at Max Elevation Hydraulic Conductivity Depth to Water Table Riser Geometry Riser Structure Type Riser Diameter Common Length Riser Crest Elevation : 100.00ft : 103.20ft : 103.50ft 3.20ft : 250 0 ft . 125.0 ft : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 ft/ft : 31250. sq-ft : 38,819. sq-ft 0.891 acres : 111,891. cu-ft : 2.569 ac-ft : 39566. sq-ft 0.908 acres : 123,642 cu-ft : 2.838 ac-ft 0.00 ft/dy 100.00 ft : Circular : 18.00 in : 0.160 ft : 103.20 ft Hydraulic Structure Geometry N umber of Devices: 2 ---Device Number 1 --- Device Type : Circular Orifice Invert Elevation Diameter Orientation Elbow : 100.00 ft : 3.00 in : Horizontal : No --- Device Number 2 --- Device Type : Vertical Rectangular Orifice Invert Elevation Length Height Orientation Elbow : 102.00 ft : 1.60 in : 16.00 in : Vertical : No R3TillRPT.rtf 2 of 4 *** Post -Developed Link Statistics *** Postdeveloped Water Surface Elevation Data (ft) Recurrence Interval Computed Using Gringorten Plotting Position Tr (yrs) Link* 1 ** 1.05-Year 101.060 1.11-Year 101.406 1.25-Year 101.603 2.00-Year 102.146 3.33-Year 102.475 5-Year 102.620 10-Year 102.800 25-Year 102.909 50-Year 102.930 100-Year ** Record too Short to Compute Peak WSEL for These Recurrence Intervals Postdeveloped Infiltrated Water Statistics Volume Statistics Computed for Entire Simulation Statistic Link: 1 Total Inflow Volume (ac-ft) 1533. Total Volume Infiltrated (ac-ft) 0. Percent Infiltrated 0.00 Is ***********Water Quality Facility Data ************* Node No: 1 Basic Wet Pond Volume (91% Exceedance): 46142. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume. 69213. cu-ft 2-Year Discharge Rate : 2.497 cfs 15-Minute Timestep Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.87 cfs Off-line Design Discharge Rate (91 % Exceedance): 0 48 cfs Computed Flow Splitter Data Orifice Diameter: 3.50 inches Baffle Wall Height (WQ Design Depth): 2.07 feet Baffle Wall (Weir) Length: 3.93 feet (47.2 inches) Ratio: WQ Depth/Orifice Diameter: 7.1 (>=2 PASS) Node No: 2 2-Year Discharge Rate : 0.372 cfs R3Tt]1RPT.rtf 3 of 4 ***********Compliance Point Results ************* Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Tr (Years) Discharge (cfs) Postdevelopment Runoff Tr (Years) Discharge (cfs) ** 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Record too Short O .680 O .862 O .975 1.057 1.168 * * * * to Compute Peak 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Discharge for These 0.372 0.563 O .655 O .711 O .939 * * * * Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped %%Q2 (Must be Less Than O%): Maximum Excursion from'/%Q2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): - 24.4% PASS - 24.4% PASS -16.7% PASS 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS R3Ti11RPT.rtf 4 of 4 MGS FLOOD PROJECT REPORT Program Version: 3.12 Run Date: 05/08/2007 12:55 PM Input File Name. RSTill.fld Project Name: Belfair SWMP Analysis Title: R-5 Till Comments: 40% Maximum impervious coverage allowable ********** Precipitation Input********** Precipitation Station Data Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station 455549 Montesano Evaporation Station : 456803 Puyallup At Site 25-Year, 24-Hour Precipitation (inches): 4.80 Gage 25-Year, 24-Hour Precipitation (inches) : 5.46 Precipitation Scale Factor : 0 878 Evaporation Scale Factor 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default 10/01/1954-10/01 /1999 ********** Default HSPF Parameters Used (Not Modified by User) *************** ********** Watershed Definition ********** ********** Subbasin Number: 1 ********** Number of Subbasins: 1 ***Tributary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasin Total Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious L ateral 1 L ateral 2 Predeveloped 10.000 O .000 O .000 O .000 O .000 0.000 0.000 O .000 10.000 Area(Acres) Developed To Node_ Bypass Node 0.000 O .000 6.000 O .000 O .000 0.000 O .000 4.000 10.000 O .000 0.000 O .000 0.000 0.000 O .000 O .000 O .000 0.000 Lateral Flow Connnections Predeveloped Developed Surface Interflow Grnd Water Surface Interflow Grnd Water Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node R5Til1RPT.rtf 1 of 4 *** Subbasin Connection Summary*** S ubbasin 1 > Node 1 *** By -Pass Area Connection Summary *** No By -Passed Areas in Watershed U pstream Node No. Node 1 *** Postdeveloped Node Connection Summary*** Link Type Downstream Node Pond Node 2 Predeveloped Compliance Node: Postdeveloped Compliance Node: Link No. 1, Pond: R-3 Pond 1 2 *** Predeveloped Structure Summary*** None *** Postdeveloped Structure Summary*** Upstream Node : 1, Downstream Node Prismatic Pond Option Used Pond Floor Elevation Riser Crest Elevation Max Pond Elevation Max Storage Depth Pond Bottom Length Pond Bottom Width Pond Side Slopes Pond Bottom Area Area at Riser Crest El Volume at Riser Crest Area at Max Elevation Vol at Max Elevation Hydraulic Conductivity Depth to Water Table Riser Geometry Riser Structure Type Riser Diameter Common Length Riser Crest Elevation 2 : 100.00ft : 103.00ft : 103.50ft 3.00 ft 290.0ft . 145.0 ft : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 ft/ft : 42050. sq-ft : 50,204. sq-ft 1.153 acres 138,201. 3.173 51626. 1.185 acres 163 647. 3.757 ac-ft 0.00 100.00 : Circular : 24 00 in : 0.170 ft : 103.00 ft Hydraulic Structure Geometry N umber of Devices: 2 ---Device Number Device Type Invert Elevation Diameter Orientation Elbow : Circular Orifice : 100.00 ft : 3.10 in : Horizontal : No --- Device Number 2 --- Device Type : Vertical Rectangular Orifice Invert Elevation Length Height O rientation Elbow : 101.60 ft : 2.00 in : 17.00 in : Vertical : No cu-ft ac-ft sq-ft cu-ft ft/dy ft R5Ti11RPT.rtf 2 of 4 *** Post -Developed Link Statistics *** Postdeveloped Pond Water Surface Elevation Statistics P ostdeveloped Water Surface Elevation Data (ft) Recurrence Interval Computed Using Gringorten Plotting Position Tr (yrs) Link: 1 ** 1.OS-Year 1.11-Year 1.25-Year 2.00-Year 3.33-Year 5-Year 10-Year 25-Year 50-Year 100-Year Record too 100.886 101.177 101.351 101.793 102.062 102.171 102.323 102.407 102.439 ** Short to Compute Peak WSEL for These Recurrence Intervals Postdeveloped Infiltrated Water Statistics Volume Statistics Computed for Entire Simulation S tatistic Link: 1 Total Inflow Volume (ac-ft) 1568. Total Volume Infiltrated (ac-ft) 0. P ercent Infiltrated 0.00 % ***********Water Quality Facility Data ************* Node No: 1 Basic Wet Pond Volume (91 % Exceedance): 47786. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume. 71679. cu-ft 2-Year Discharge Rate : 2.576 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91 % Exceedance): 0.96 cfs Off-line Design Discharge Rate (91% Exceedance): 0 52 cfs Computed Flow Splitter Data Orifice Diameter: 3 75 inches Baffle Wall Height (WQ Design Depth): 1.88 feet Baffle Wall (Weir) Length: 4.58 feet (55.0 inches) Ratio: WQ Depth/Onfice Diameter: 6.0 (>=2 PASS) Node No: 2 Basic Wet Pond Volume (91 % Exceedance): 25712. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume. 38568. cu-ft 2-Year Discharge Rate : 0.381 cfs R5T111RPT.rtf 3 of 4 ***********Compliance Point Results ************* Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Tr (Years) Discharge (cfs) Postdevelopment Runoff Tr (Years) Discharge (cfs) ** 2-Year 0.680 2-Year 5-Year 0.862 5-Year 10-Year 0.975 10-Year 25-Year 1.057 25-Year 50-Year 1.168 50-Year 100-Year ** 100-Year 200-Year ** 200-Year Record too Short to Compute Peak Discharge for These 0.381 0.570 0.663 0.715 0.841 ** ** Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped Y%Q2 (Must be Less Than 0%): Maximum Excursion from'%Q2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): -27.3% -27.3% -8.3% 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS PASS PASS PASS R5T111RPT.rtf 4 of 4 MGS FLOOD PROJECT REPORT Program Version: 3.12 Run Date: 05/08/2007 12:54 PM Input File Name. Project Name. Analysis Title: Comments: R10TiII.fld Be!fair SWMP R-10 Till 50% Maximum impervious coverage allowable ********** Precipitation Input********** Precipitation Station Data Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station 455549 Montesano 10/01/1954-10/01/1999 Evaporation Station : 456803 Puyallup At Site 25-Year, 24 Hour Precipitation (inches): 4.80 Gage 25-Year, 24-Hour Precipitation (inches) : 5.46 Precipitation Scale Factor : 0.878 Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** Number of Subbasins: 1 ***Tributary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasin Total Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Lateral 1 Lateral 2 ********** Watershed Definition ********** ********** Subbasin Number: 1 ********** Predeveloped 10.000 O .000 O .000 O .000 0.000 O .000 O .000 O .000 10.000 Area(Acres) Developed To Node Bypass Node 0.000 0 000 0.000 5.000 O .000 O .000 O .000 O .000 5.000 10.000 0 000 O 000 0 000 O 000 O 000 O 000 O 000 0.000 Lateral Flow Connnections Predeveloped Developed Surface Interflow Grnd Water Surface Interflow Grnd Water Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node Node R10T111RPT.rtf 1 of 4 *** Subbasin Connection Summary*** Subbasin 1 > Node 1 *** By -Pass Area Connection Summary *** N o By -Passed Areas in Watershed U pstream Node No. Node 1 *** Postdeveloped Node Connection Summary **' Link Type Downstream Node Pond Node 2 P redeveloped Compliance Node: 1 Postdeveloped Compliance Node: 2 *** Predeveloped Structure Summary*** None *** Postdeveloped Structure Summary*** Link No. 1, Pond: R-3 Pond U pstream Node : 1, Downstream Node: 2 Prismatic Pond Option Used Pond Floor Elevation Riser Crest Elevation Max Pond Elevation Max Storage Depth Pond Bottom Length Pond Bottom Width Pond Side Slopes Pond Bottom Area Area at Riser Crest El Volume at Riser Crest Area at Max Elevation Vol at Max Elevation Hydraulic Conductivity Depth to Water Table Riser Geometry Riser Structure Type Riser Diameter Common Length Riser Crest Elevation : 100.00ft : 103:OOft : 103.50ft 3.00ft : 300.0 ft 150.0 ft : L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 ft/ft : 45000. sq-ft : 53,424. sq-ft 1.226 acres : 147,455. cu-ft : 3.385 ac-ft : 54891. sq-ft 1 260 acres : 174,523. cu-ft : 4.006 ac-ft . 0.00 ft/dy . 100.00 ft : Circular : 24.00 in : 0.180 ft : 103.00 ft Hydraulic Structure Geometry N umber of Devices: 2 ---Device Number 1 --- Device Type : Circular Orifice Invert Elevation : 100.00 ft Diameter : 3.00 in Orientation : Honzontal Elbow : No --- Device Number 2 --- Device Type Invert Elevation Length Height Orientation Elbow Vertical Rectangular Orifice : 101.75 ft : 2.00 in : 17.00 in : Vertical : No R1OTi11RPT.rtf 2 of 4 *** Post -Developed Link Statistics *** Postdeveloped Pond Water Surface Elevation Statistics Postdeveloped Water Surface Elevation Data (ft) Recurrence Interval Computed Using Gringorten Plotting Position Tr (yrs) Link: 1 ** 1.05-Year 101.021 1.11-Year 101.266 1.25-Year 101.459 2.00-Year 101.929 3.33-Year 102.259 5-Year 102.338 10-Year 102.496 25-Year 102.584 50-Year 102.626 100-Year ** Record too Short to Compute Peak WSEL for These Recurrence Intervals Postdeveloped Infiltrated Water Statistics Volume Statistics Computed for Entire Simulation Statistic Link: 1 Total Inflow Volume (ac-ft) Total Volume Infiltrated (ac-ft) Percent Infiltrated Node No: 1 1639. 0. 0.00 % ***********Water Quality Facility Data ************* Basic Wet Pond Volume (91% Exceedance): 50865. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 76298. cu-ft 2-Year Discharge Rate • 2 778 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91 % Exceedance): 1.13 cfs Off-line Design Discharge Rate (91% Exceedance): 0.62 cfs Computed Flow Splitter Data Orifice Diameter: 4.00 inches Baffle Wall Height (WQ Design Depth): 2.05 feet Baffle Wall (Weir) Length: 4.19 feet (50.3 inches) Ratio: WQ Depth/Orifice Diameter: 6.1 (>=2 PASS) Node No: 2 Basic Wet Pond Volume (91% Exceedance): 25112. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume. 37667. cu-ft 2-Year Discharge Rate : 0.367 cfs R1 OT111RPT.rtf 3 of 4 ***********Compliance Point Results ************* Predeveloped Compliance Node: Postdeveloped Compliance Node: 1 2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Tr (Years) Discharge (cfs) Postdevelopment Runoff Tr (Years) Discharge (cfs) ** 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Record too Short 0.680 2-Year 0.862 5-Year 0.975 10-Year 1.057 25-Year 1.168 50-Year 100-Year 200-Year to Compute Peak Discharge for These 0.367 0.571 0.666 0.721 0.842 ** ** Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped %Q2 (Must be Less Than 0%): Maximum Excursion from %Q2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): -34.9% PASS -34.9% PASS -10.0% PASS 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS • R1 OTi11RPT.rtf 4 of 4 Appendix C—Construction Cost Estimates Baseline Water Quality Monitoring Program This estimate is based on the following assumptions. ' e ( $ 28,800 $ 24,000 $ 18,000 $ 74,800.00 o O O O O O N 6 N e p 0 0 a a 0 0 CCOoo r r r r al W Hours 20 360 240 180 O O co N with help from a consultant Grab samples will be collected by County Staff (following training by consultant) to a consultant for analysis (40hrs, 6 ti Ito a lab for testing (60hrs, 61 Consultant will train County Staff to collect be prepared U a) O c O E a) 0 0) c a) E a) 0) 0) C O _O N .0 1- vi 0) c "c (U O O Q) O . O O a) C a) 0 N O (6 0 a) ▪ 0 ° a) a) L 0) 0) X Oa) row- O > O O 0 U • O '5 N a) -o 0 O L L. 0 a) E 0 E (a L 0 0 0 Tam • a) 0 Y a) 0 O 4O 0 O c C O 0 0 • 0 0) C L O C O E N O O a) c 0) C .o C O r 0 0 O a) 0 0 0 Q C i a) a) -a 0 C L- m a) C a) L O K:\project\30700\30784\Data\Cost\Belfair\CIP_Estimates.xls, WQStudy (0 E N W N 0 0 0 a) O n 0 2 0 T C � O N 23. .Q c (0 z a) `a) C a) c0 ti) m CL Stream and Habitat Assessment and Mapping Program a) 0 v) (a m v) c 0 a E O O a) c O .O a) U) u) a) E a) s H $ 12,000 . 0 0 0 0 0 0 o odi 0 `t cp d CD 0. 0 0 0 0 0 0 r r r ,� (1.62 0 40i 40 N r 0 by a consultant teams and ) .O .0 a) a w 0 .D to a (0 E .O C CO a) N (0 .O (0 ((0 -a O c 0 N N a 4) a_ -o c 0 co - a) t 0 0 a 46 c (0 0 O (0 O (0 c a) E co (0 a) co u? (0 (0 0 -c a) (0 Its 0 "O c 0 a) > c U a) E 0 U O -0 N a a a) a O (6 E N .n a) co 0 0 0 0 O Q) • L- s) a • c N E W • o a) a) O 0 O O (0 CD 0 K:\project\30700\30784\Data\Cost\Belfair\CIP_Estimates.xls, Habitat a) 2 tin C!) ❑ a) N N W O U U a) we - a) E a) O Q E a) O) a. N U N () L: a) a) a) Q U t a) ai N O O CO 0- 000 o CD 0 o CO- 0- CI CO r 0 O CO • 6<} co- O ao EPr a) �- • U) OD > CD CD O 0 O CO (o yN(�i (1)r U O x U) L a C U c0 E co a) N r W 0 O M Fish Passage Culvert (Olympic Region WSDOT Bid History Data) 0 0 0 o O 0 0 0 o O O O O O 0 (n 0 O Lo N r CO CO EFT 69 O O 0 O O r 69 O O O0 O 0 O r r Eft 69 s 0� X x <( 03> tr- ti a R1 ro co- c c0 CO (0 re ❑❑❑'- O 0 o . c (0 _ts 2 2 ± -a -a 'o mmm Q. H rue 000E CO Cn O)) co O O O 4O N 0 N N rL 0‘O U U U a) Q_ a a.c E E E >' >, _>' a) OOOa 0 0 O O O 0 0 O (O (n o (n (. O) O d' M r 0 O 0 (n N (f69KT69 i0Tut U >->- U < U U < CO O O M r 00 CO r 0 0 r r o ° r N N CO 0 0) d^ r CO r O CO CO O CO- N O r ti O Md'COr• CO et) CO 69 VI r CO 69 0) Cr/ CA SUBTOTAL $ 10 CO O O O CC Ci O O U 0 F- 0 Z • Q ❑ cc H co Z _O U) 0 Q.' W CONTINGENCY CONSTRUCTION SUBTOTAL 0 co CO CD 0 CV r (9 ?co • $ (O O (f) a) N N 'p O J 1— O F U w 0 Cr 0. Q W za 2 z 0 CC U 1- F z 0 0 K:\project\30700\30784\Data\Cost\Belfa 4_ • E NIPPlire pt-ss LT7 FRS S c-C7 gm- ,� r ry Pa e 5 A4r2 -r PA -Cc ``/ Pa 6Z Si Cos L tM? c,: RvLdPr ✓ �13 � Gc, S(- A- L. i csf c-1(\e‘ k w iAlp-civc c._ Frpek t o (t T Vcc}13 I( •r u)(ffbe x`isp- �u 9 cl 0\2.47 4 i Aus does r.v- r fruc.tc2d.,e- s- front. wrejoak EA v r crn ►,n,eAt\. (/c Sc r\ �-- q2-5/07- Mason County Update of County's Stormwater Policies/Regulations and Development of Comprehensive Stormwater Management Plans Allyn Urban Growth Area Stormwater Management Plan: Addendum Submitted to: Mason County Department of Public Works 41 I N. Fifth Street Shelton, WA 98584 Submitted by: Otak, Inc. 10230 NE Points Drive Suite 400 Kirkland, WA 98033 Otak Project No. 30784 August 21, 2007 Transmittal Mason County Update of County's Stormwater Policies/Regulations and Development of Comprehensive Stormwater Management Plans Allyn Urban Growth Area Stormwater Management Plan: Addendum Submitted to: Mason County Department of Public Works 411 N. Fifth Street Shelton, WA 98584 Prepared By Otak, Inc. Joe Simmler, Ph D Project Manager Larry Grimm, PE Project Engineer Preface This Addendum to the Allyn Urban Growth Area Stormwater Management Plan (SWM Plan) (Revised edition, July, 2007) has been prepared by Mason County in order to address the additional comments received from the public, regulatory agencies and major stakeholders (Tribes and businesses) since the June 20, 2007 Public Hearing. The original deadline of August 6, 2007 for presentation and submittal to the Western Washington Growth Management Hearings Board has been extended for sixty days to October 6, 2007. During this time, the County has elected to produce this Addendum, presenting further revisions and enhancements to the second draft of the Allyn SWM Plan. The Allyn SWM Plan was funded by Mason County. The development of the Mason County SWM Planning process is being jointly administered by the Washington State Department of Ecology and the Puget Sound Partnership. Table of Contents Allyn Urban Growth Area—Stormwater Management Plan Section I —Introduction Section 2 Receipt of Public Comments Section 3—Countywide Comprehensive SWM Program Section 4—Response to Public Comments: Plan Revision Section 5 Summary of Revisions to Original Draft SWM Plan Section 6—Future Public Involvement and Future Updates to the Plan References List of Tables Table 2-1—Grouping of Comments by SWM Topic Table 4-1—Recommended SWM Programmatic Elements and Costs Table 4-2 Recommended Allyn SWM Program Elements and Costs Figures Figure 3-1 Mason County SWMM Planning Area Map Appendix A —Water Quality, Fish Shellfish and Habitat Report Figure 4 I —Mason County WRIA Map Figure 4 2-2007 Threatened Shellfish Areas Figure 4-3—Allyn Surface Drainages Figure 4-4 North Bay Shellfish Sampling Areas Figure 4-5 Pickering Passage Shellfish Sampling Areas Figure 4-6 Belfair Surface Drainages Figure 4-7 Hood Canal Station #9 Shellfish Sampling Areas Mason County —Allyn U G A S t o r m w a t e r Management Plan i otak I-I:\project \30700\30784\Reports \ Addendum \Final TextOnlyJJS to Use \Final Text JJS-MK3-DNAllyn.doc Section I —Introduction 1.1 Objective and Intent This Addendum to the Allyn Stormwater Management Plan (SWM Plan) was created by Mason County in order to respond to additional public comments received over the last several weeks. It includes and addresses the comments received verbally at the June 20, 2007 public meeting and the comments received via letters and in coordination meetings with regulatory agencies since July 2, 2007 when the revised SWM Plan was issued to the public. The receipt and analysis of the various public comments has resulted in an enhanced set of programmatic SWM activities and revised capital improvement program, as documented in this Addendum. Both the completeness and comprehensiveness of the proposed Allyn SWM Plan have been expanded and enhanced. These comments have also been used to structure and guide the development of the Countywide Comprehensive SWM Plan, conceptually presented in Section 3.0. 1.2 Format and Content Public and regulatory comments collected from the June 20, 2007 public meeting and subsequent letters over the following weeks were reviewed, organized by topic and developed into recommended SWM Program enhancements Each topic resulted in the collection of new information for water quality and shellfish, the expansion of an existing SWM activity or the addition of a new SWM activity or approach to the overall SWM Program. As an example, a decentralized approach has now been adopted to address the drainage related impacts of new development replacing the earlier approach using large regional centralized detention treatment and/or conveyance systems. Also, a new SWM Program initiative has been added to retrofit all existing development using low impact development techniques, such as the bio-retention swale, in order to treat stormwater runoff prior to discharge. Similar SWM Program enhancements have been made for public involvement, design criteria, development standards, maintenance, public education, public involvement, water quality monitoring, inter- and intra-agency coordination and funding. This Addendum and the July 2007version of the final SWM Plan constitutes the final version of the SWM Plan proposed for the Allyn Urban Growth Area (UGA). 1.3 Overview of Public Process and BOCC Review This Addendum will go through a second public review process beginning August 27, 2007 that consists of a public meeting on September 10, 2007 presentation to the Planning Commission on September 17 2007, and presentation to the Board of County Commissioners (BOCC) at public hearings on September 18, 2007 (and possibly October 2, 2007) prior to a final decision by the BOCC. Mason County — Allyn U G A Stormwater Management Plan 1 otak H:\project\30700\30784\Reports\AAddendum\Final Text -Only JJS to Use\Final Text JJS-MK3-DNtlllyn.doc Section 2—Receipt of Public Comments 2.1 Public Review Process For Original Draft of the Allyn SWM Plane Issued June 2007 The schedule for development and adoption of the Allyn UGA SWM Plan, and its associated public review process, has been driven by an August 6, 2006, Growth Management Hearings Board Final Decision and Order, which mandated the County's submittal of improved and adopted SWM Plan by August 6, 2007. In accordance with this target date, the draft Allyn UGA SWM Plan was developed and made available to the public in early June, 2007. The County hosted a public meeting to receive comments on the plan at the Port of Allyn on the evening of June 20, 2007, with the official comment period closing on June 29, 2007. For Revised Draft Issued July 2007 The plan was revised and re -issued on July 2, 2007, based on comments received at the pubhc meeting and based on written comments from the Department of Kcology (Ecology) and the Puget Sound Action Team (PSAT) (now known as the Puget Sound Partnership (PSP)). A briefing and two public hearings were held on the revised plan. The first public hearing was conducted before the County's Planning Advisory Committee (PAC) on July 9, 2007. A briefing was held before the Board of County Commissioners (BOCC) on July 23, 2007, and the second public hearing was conducted before the BOCC on July 24, 2007. For Final Addendum. Issued September 2007 In early August, the Growth Management Hearings Board granted the County a 60-day extension of its original submittal deadline to October 6, 2007. This extension has provided the County the opportunity to continue to respond to comments and create this Addendum to finalize the SWM Plan. Completion of the Addendum precedes a second formal public review cycle that includes a public meeting scheduled on September 10, 2007, a PAC hearing on September 17, 2007, and a first hearing on adoption by the BOCC, scheduled for September 18, 2007. Should the first BOCC hearing be continued, a final hearing on adoption may be scheduled for October 2, 2007. 2.2 Comments Received The County received comments on the draft plan and revised plan through public meetings, letters, and meetings with regulatory agencies The following is a list of various sources of public comment that have been compiled and addressed in the Master Comment Response Matrix. (Note that the Master Comment Response Matrix is a separate document and is available upon request from the County) Mason County Allyn UGA Stormwater Management Plan 2 otal< H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNAllyn.doc Section 2—Receipt of Public Comments Continued 1. Department of Ecology Comment Letter Re• Allyn UGA SWM Plan, 6/29/07, Kim McKee, Unit Supervisor, Southwest Region Water Quality Program 2. Puget Sound Partnership Comment Letter Rem Allyn & Belfair UGA SWM Plans, 6/29/07, Brad Ack, Director 3. Department of hcology Comment Letter Re: Belfair UGA SWM Plan, 7/2/07, Kim McKee, Unit Supervisor, Southwest Region Water Quality Program 4. Squaxin Island Tribe Letter Rem Allyn UGA SWM Plan, 7/24/07, John Konovsky, Environmental Program Manager 5. Lower Hood Canal Watershed Coalition Letter Re: Stormwater impacts to Hood Canal, 5/26/07, Robert Hager, Co -Chair 6. Lower Hood Canal Watershed Coalition Letter Re: County SW Policy and Regulations, 6/20/07, Robert Hager, Co -Chair 7. Lower Hood Canal Watershed Coalition Letter Re: Belfair UGA SWM Plan, 6/20/07, Robert Hager, Co -Chair 8. PAC Meeting Notes 7-9-07, Barb Robinson, Mason County, Department of Community Development, Director 9. Allyn Community Association Re• Allyn UGA SWM Plan Technical Issues, 6/29/07, Jeff Carey, President The various comments have been grouped by topic, as presented in Table 2-1, and have been used to shape the content and format of this Addendum to the revised plan. Additional comments taken from Section 10 of the revised plan also have been included in Table 2-1 and are numbered accordingly. Table 2-I—Grouping of Comments by SWM Topic Stormwater Management Topic Priority Public # of Comments Regulatory /Compliance/Programmatic Approval 3 18 PSWQMP: 2.2.4, 2.16, 2.29 Basin Planning/Watershed Approval: 2.2.4, 2.18, 2.23, 2.2.2, 6 16 2.13, 3.4 6 15 Ranking of Problems: 2.2.4, 2.12, 2.18, 2.23, 2.37, 7.3 8 12 WQ Monitoring: 2.1.1, 2.1.2, 2.17, 7.12, 8.3, 8.14, 10.7, 10.32 12 4 Funding 10.21, 10.34 2.1.1, 2.1.2, 2.5, 2.15, 2.17, 2.22, 2.25, 3.17, 7.5, 10.2, 5 17 Phase II NPDFS• 1.1, 1.9, 2.29, 3.17, 10.29 Agency Coordination: 1.5, 2.22, 3.17, 5.3, 7.7, 8.13 6 14 Mason County Allyn UGA Stormwater Management Plan 3 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNAllyn.doc Section 2—Receipt of Public Comments Continued 11 6 Inspection/Inventory/Maintenance: 1.4, 1.6, 1.10, 2.18, 2.23, 2.37, 3.8, 3.18, 3.19, 5.1, 8.14 7 12 Illicit Discharge Detection and Elimination (IDDH)• 1.8, 1.10, 2.2.4, 2.23, 2.37, 3.16, 3.18 8 11 Public Education: 1.10, 2.1.2, 2.22, 2.37, 3.17, 3.18, 5.2, 7.9 10 7 Public 10.9, 10.10 Involvement: 1.10, 2.2.9, 3.18, 3.19, 7.6, 8.14, 9.5, 10.3, 2 20 Programmatic: 2.2.4, 3.19 3 19 Countywide SWMP 1.7, 2.22, 3.2 Natural Resource Protection/ N nhancement Water 10.31, 2.1.1, Quality: 3.6, 2.2.1, 3.10, 2.2.3, 3 2.16, 14, 4.1 (2.31), 4.2, 5.1, 2.35, 5.2, 6.1, 2.36, 2.38, 7.11, 3.1, 8.7, 3.3 21 2 Shellfish: 2.2.3, 2.28, 2.35, 2.38, 4.1, 6.2, 8.2, 8.7 8 10 9 9 Salmon/Habitat: 2.2.3, 2.22, 2.38, 3.14, 4.4, 8.11, 8.13, 10.7, 10.41 25 1 Retrofit Existing/Bioretention/Decentralized CIP 1.2, 1.4, 1.6, 2.12, 8.6, 2.17, 8.8, 2.22, 8.9, 8.10, 2.40, 9.1, 3.1, 9.2, 3.17, 9.4, 4.1, 9.5, 10.28, 7.10, 8.13, 10.33 10.30, 3.14, 7.11, Development 2005 Manual/Design Standards: 1.10, 2.1, 2.17, 2.22, 3.17, 3.18, 11 5 5.4, 6.1, 6.2, 6.3, 7.2 Low Impact Development (LID). 1.3, 2.1, 2.7, 2.10, 2.11, 2.14, 16 3 2.19, 2.20, 2.21, 2.22, 2.40, 3.7, 3.17, 7.8, 7.9, 10.12 9 8 Dispersion of Stormwater On-site/Reduction of Impervious Areas/Retention of \ative Vegetation: 2.2.1, 2.4, 2.9, 2.32, 2.33, 2.36, 4.3, 4.4, 5.1 186 Total number of comments received: Of the 186 comments listed in Table 2-1, the top six topics account for 105, or 56% of the comments. The top six most common comments included the following, in order of priority. • Retrofit Existing/Bioretention/Decentralized CIP, • Water Quality, • Low Impact Development, • Funding, • 2005 Manual/Design Standards, and • Inspection/Inventory/Maintenance. Additional comments were received from DOFH and PSP as well as Washington State Department of Fish and Wildlife on the revised plan as noted in the sources below. Mason County Allyn UGA Stormzvater Management Plan 4 otak H:A project \30700\30784\Reports \ Addendum \Final Text -Only JJS to Use\Final TextES-MK3-DNAllyn.doc Section 2 Receipt of Public Comments Continued Although not listed in Table 2-1, many of the comments were similar to those presented earlier and have been addressed in the following sections of this Addendum. 1. State Department of Fish and Wildlife Comment Letter Re• Allyn UGA SWM Plan, July 24, 2007 Brad Sele, Regional Shellfish Manager, Fish Program, Region 6 2. Meeting with Kim McKee of Ecology and Bruce Wulkan of the Puget Sound Partnership, July 18, 2007 3 E-mail of additional comments on the revised draft was received from Bruce Wulkan of the Puget Sound Partnership on August 15, 2007. 4 E-mail of additional comments on the revised draft was received from Kim McKee of the Washington State Department of Ecology on August 16, 2007. 2.3 Master Comment Response Matrix The County developed a Master Comment Response Matrix that includes comments received through public meetings, comment letters, emails, and regulatory meetings, as referenced in the preceding section. These comments from the public, regulatory agencies, Tribal and stakeholders have helped guide this second review and update of the proposed SWM Plan. As a result, the revised plan includes additional information on existing conditions related to natural resources, together with a comprehensive program to provide for future development and comply with existing and future regulatory requirements. The Response to Public Comments (Section 4) along with the revised SWM Plan presents the County's responses to all of the public comments received to date, and attempts to be responsive to each major topic, as listed above. These public comments, along with various regulatory requirements and local water quality, flow and habitat information, have also been used as the primary sources of guidance for the development of the comprehensive Countywide SWM strategy presented in Section 3. Mason County —Allyn UGA Stormwaler Management Plan 5 otak H:\project\30700\30784\Reports\Addendum\Final TextOnlyJJS to Use\Final Text-JJS-MK3-DNAllyn.doc Section 3—Countywide Comprehensive SWM Program 3.1 Stewardship of the Region's Natural Resources Objectives of the Countywide Comprehensive SWM Planning Process Mason County is blessed with a wealth of natural resources that significantly add to the local quality of life and the economy of the region. The County, recognizing its role as one of the primary stewards of these resources, is in the process of developing a countywide stormwater management plan (SWM Plan) to both protect and enhance these resources. The primary objective of this plan is to protect water quality, shellfish, habitat, groundwater and their supporting natural processes and functions, to continue to promote and guide new development and to be responsive to existing and future regulatory requirements. 3 2 County's Watershed Planning Process Prioritization of Stormwater and Water Quality Problems The County's SWM Program is in its initial stages of development. The County has not had the opportunity to conduct watershed planning or to complete a comprehensive inventory of stormwater facilities or to assess the problems that stormwater runoff may be causing throughout the County. However, as a result of this initial SWM planning process, research has been undertaken and interviews have been conducted, the results of which suggest that the County's current stormwater related water quality problems consist of the following: Nutrient and fecal coliform loadings into sensitive receiving waters. Research by the University of Washington and monitoring by Ecology, County and State departments of health, and State Fish and Wildlife suggest that nutrients and coliforms are having major impacts on local and regional receiving waters and their associated habitat areas. Failing and poorly designed and maintained septic systems have been identified as one of the major sources, and septic maintenance and monitoring programs have been proposed. Also, centralized wastewater collection, conveyance and treatment systems have been proposed for the Belfair and Hoodsport areas, and a small system has already been installed at the end of North Bay near the Allyn UGA. A second major source of nutrient and coliform pollution is through stormwater runoff. While stormwater runoff does not generate these pollutants, it does pick them up from various land uses, concentrates them and transports them directly into sensitive local receiving waters. Most of the runoff in the County is not adequately detained or treated, which causes both flow and habitat problems and increases the need for effective stormwater management, particularlywithin the more urban and developing areas of the County. Mason County — Allyn UGA Stormwater Management P l a n 6 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text JJS-MK3-DNAllyn.doc Section 3 Countywide Comprehensive SWM Program Continued Impacts to water quality, shellfish and habitat areas. The impacts to local natural resources within Hood Canal and the southern reaches of Puget Sound are well documented. Monitoring within the areas adjacent to the Allyn UGA in North Bay and within the.Belfair UGA in the south end of Hood Canal suggest that nutrients, and fecal conforms from surface water runoff and failing septic systems are degrading water quality, freshwater streams and fish habitat, as well as saltwater shellfish rearing areas. Substantial documentation of these impacts has been recorded and on -going monitoring programs continue to provide updated status of local conditions on an annual basis. Many of the coliform monitoring stations show a steady increase in concentrations which are threatening recreational and commercial shellfish harvesting, and if unchecked will result in the decertification of many of the existing commercial harvest areas. Again, inadequately detained and treated stormwater runoff from developed areas has been identified as one of the primary causes of continued and increasing loadings of pollutants and their resulting degradation of water quality and threats to adjacent shellfish rearing areas. Additional controls of runoff from developed areas, as well as runoff from future developed areas, are being mandated by regulatory agencies, stakeholders and the public. Additional development controls and guidance have been suggested in the County's SWM Planning processes to minimize these impacts, as described below in this Addendum. Erosion and sedimentation. I- rosion and sedimentation impacts generally have two major sources that often are interrelated, further enhancing the problem and the resulting impacts. Significant erosion can occur when a new site is graded for development. After development, the increase in surface water flows often causes downstream channel erosion and undercutting of stream banks. Deposition of eroded sediments smothers sensitive spawning areas and if discharged into marine areas can also degrade shallow shellfish rearing areas. Addressing erosion related problems involves the development and enforcement of effective development standards and design criteria, as well as the effective management of onsite and downstream surface water runoff. Flood control. Flooding is common in certain parts of the County and is often the direct result of land use changes Having good land use controls, including comprehensive planning, design standards and permit review along with enforcement processes are the primary tools for the control of flooding. Usually flooding is the cumulative effect of a series of major land use changes that occur over time throughout the watershed. Uncontrolled runoff with its associated property and habitat damage is the result of these changes. The effective control of flooding is directly related to the effective control of surface water, both during and after Mason County Allyn UGA Stormwater Management Plan 7 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text JJS-MK3-DNAllyn.doc Section 3 Countywide Comprehensive SWM Program Continued land use alterations. A comprehensive stormwater management program is needed within the County to support the County's flood reduction and management efforts. 3.3 Countywide Comprehensive SWM Management Strategy The County s proposed stormwater management strategy is a phased approach that initially focuses on the protection and enhancement of the County's most sensitive natural resources by addressing the SWM issues in the urban areas of the County. This strategy includes the development of a Comprehensive Countywide SWM Plan, with more in-depth technical studies in the areas of Allyn, Belfair, Hoodsport, Union and impacted sensitive areas such as Oakland and Annas Bays. The geographic extent of this initial phase of the countywide SWM strategy, as shown in Figure 3-1, includes: • The Urban Growth Areas of Allyn and Belfair, ® The Rural Activity Centers of Hoodsport, Taylortown (I and II), and Union, and ® The identified Water Quality Sensitive Areas of Oakland Bay and Annas Bay, as described in the Oakland Bay Action Plan and Annas Bay Closure Response Strategy. Other urban and sensitive natural resource areas may be added in the future during the annual review and update of the proposed Comprehensive Countywide SWM Plan. 3.4 Focus of the Comprehensive Countywide SWM Plan Emphasis on Water Quality and Effective SWM in Urban Areas The County is committed to enhancing water quality and promoting effective stormwater management especially in its Urban Growth Areas (UGAs) and rapidly urbanizing areas, both within and adjacent to sensitive natural resource areas. This SWM planning strategy, as documented in the Comprehensive Countywide SWM Plan currently under development, is intended to address the drainage related impacts of existing and future development and to protect and enhance water quality, shellfish, habitat and groundwater. (The draft Comprehensive Countywide SWM Plan is scheduled for release to the public in the spring of 2008.) Developing a Comprehensive Countywide SWM Plan at this time allows the County to address immediate water quality, shellfish, and habitat needs and the requirements of the Puget Sound Water Quality Management Plan, as well as begin to prepare the County to come into compliance with a future National Pollution Discharge Elimination System (NPD ES) Phase II Municipal Stormwater Permit. Mason County —Allyn UGA Stormzvater Management Plan 8 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text JJS—MK3-DNAllyn.doc Taylor Town I Rural Activity Center Taylor Town II Rural Activity Center ALLYN URBAN GROWTH AREA 4/ Legend Streams Streets Railroad KI TAP. QOU°N:TY'- Shellfish Protection District Rural Activity Center WRIA Boundary L- __ County Boundary I UGA Boundary Oakland Bay Clean Water District Figure 3-1 Mason County SWMM Planning Area Map 0 W N s 2 H 4 Miles 411 North 5th, P.O. Box 279 Shelton, WasNngbn 98584 Phone: (360)427-9670 Fax: (360)427-8425 10230 NE Points Drive, Suite 400 Kirkland, WasNngbn 98033 Phone: (425) 822-4446 Fax: (425)627-9577 K:/project/30700/30784/GIS/mxds/F(gure3_1 MasonCoSWMMVer2.mxd Section 3—Countywide Comprehensive SWM Program Continued 3.5 Relationship to Allyn and Belfair SWM Plans The Allyn and Belfair UGA SWM Plans will complement and support the development of the Comprehensive Countywide SWM Plan. These SWM Plans have been developed by: • Collecting information and characterizing the various drainage areas, • Evaluating existing facilities and planning for future capital needs, • Reviewing and evaluating regulatory compliance/programmatic needs in comparison to the County's existing surface water management program, • Combining the recommended capital and programmatic needs together, along with costs and a schedule for implementation, to form the SWM Plan, and • Providing a financial plan, outhning various potential funding mechanisms and amounts of annual revenues. A similar SWM Plan for the Hoodsport area of the County is currently being developed and is expected to be released for public review in the spring of 2008. Shellfish protection and recovery plans are also under development for the Oakland and Annas Bay areas. As these SWM technical documents for the County's UGAs Rural Activity Centers (RACs), and Water Quality Sensitive Areas (WQSAs) are developed, they will be reviewed by the public and approved by the BOCC and included as technical appendices to the County's Comprehensive SWM Plan 3.6 A Comprehensive Watershed -Based Approach Elements of the Countywide Comprehensive SWM Plan Similar to the Allyn and Belfair SWM Plans the County s Comprehensive SWM Plan will assume a watershed based management philosophy for the protection of natural resources and the establishment of effective stormwater management throughout the County. This means that the County's Comprehensive SWM Plan will be based upon the technical, programmatic, capital and funding approach needed to achieve natural resource protection objectives, compliance with the PSWQMP and future Phase II NPDES Permit and support continued growth. It will emphasize the protection and enhancement of the natural resources throughout the County. It will include a series of programmatic elements, as well as a capital improvement program (CIP) for both the short- and long- term planning periods The short term CIP will support growth over the next six years, while the long term CIP will address ultimate b iildout, as defined in the County's Comprehensive Plan. In the more urban UGAs, RACs, and WQSAs, the adoption of a comprehensive SWM philosophy will require: Mason County Allyn UGA Stormwater Management Plan 9 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNAllyn.doc Section 3 Countywide Comprehensive SWM Program Continued • SWM Program: Development, adoption and annual implementation and funding of a programmatic approach to stormwater management throughout the area, as presented in the PSWQMP and future NPDES II Permit (and described in the revised SWM Plan and in this Addendum), • Design Criteria for New Development: Adoption of the 2005 Ecology Manual for all new development, Adoption of Low Impact Development (LID), as a requirement of all new development, Review and possible adoption of revisions to the Development Standards of the Comprehensive Plan, requiring all future development be conducted according to current low impact principles that include minimizing new impervious areas, optimizing the preservation of natural vegetation (including the natural understory beneath the tree cover), disconnection of roof drains, infiltration of site runoff, and dispersion of surface runoff sheetflows into the remaining natural vegetation areas. • 1-4xisting Development: Retrofit of existing impervious areas to detain and treat runoff from existing development prior to discharge using LID techniques (i.e. bio-retention) • County Road Design: Treating the runoff from all new County roads using LID techniques (i.e. bio-retention, water quality treatment filters, etc.), and • Funding:: Establishment of adequate local funding to implement the annual Comprehensive Countywide SWM Program. In the more rural areas of the County, the adoption of a comprehensive SWM philosophy will be conducted in phases, on an as needed basis or until an NPDES II Permit is issued to the County. The SWM Program for the more rural areas will require: • SIYM Program: Continued use of the County's existing SWM design criteria, • Design Criteria for New Development. Continued use of the County's existing SWM development standards and zoning codes, • 1-4xisting Development: Annual inspections and drainage system enhancements by the County Road Maintenance Crew to address small, localized flooding, water quality and sensitive area impacts on an as needed basis, • County Road Design: The treatment of runoff from all new County roads using LID techniques (i.e. bio-retention, water quality treatment filters, etc.), and • Funding: The establishment of adequate local funding to implement annual Comprehensive Countywide SWM Program for the less developed areas of the County. 3.7 Funding and Implementation Creation and Allocation of New Annual Revenues One of the challenges in developing a new Comprehensive Countywide SWM Program will be in creating the amount of new revenue needed to annually develop and operate the Mason County Allyn UGA Stormwater Management Plan 10 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNA11yn.doc Section 3—Countywide Comprehensive SWM Program Continued Program. Similar to the financial plans presented in the Allyn and Belfair SWM Plans, it is likely that various new revenue sources will need to be created and/or existing revenue sources will need to be reprioritized so that additional revenue can be directed to the new Comprehensive Countywide SWM Program. Creating Levels of Service In the development and implementation of Comprehensive Countywide SWM Program, as well as the SWM Plans for Allyn Belfair, Hoodsport and other sensitive areas, different levels of service will need to be described for each of the SWM planning areas. At least two levels of service are anticipated. The first is for SWM service within the more rural areas of the County. The second would be for SWM service within the more urban areas of the County, including the UGAs, RACs, and WQSAs. In general, the level of service and types of service will be determined by the amount and type of revenue generated from within each service area. Annual SWM priorities, work programs, capital project (CIPs) and staffing levels would be defined according to the needs and available revenues from within each service level. It is likely that services within the rural areas would include those services similar to those that are presently being provided, while the services within the more urban areas would include additional design criteria for new development, enhanced maintenance, water quality monitoring inspection/enforcement and capital projects to enhance water quality and mitigate impacted habitat areas. 3.8 Implementation and Annual Reviews to Update and Refine SWM Plan The implementation and funding of the Comprehensive Countywide SWM Plan, as well as the Allyn and Belfair SWM Plans, will emphasize an initial series of recommended, high priority SWM programmatic activities and capital projects. The development of one or more dedicated funding sources has been recommended to meet projected annual revenue needs, however, additional revenues will likely be needed. It is important to recognize that this is not the end of the planning process; rather it is just the beginning. Throughout the continued development and implementation of these SWM Plans, the County well continue to gather data and learn more about the natural systems and the effectiveness of the various SWM initiatives. This information will be used on an annual basis to continue to evaluate the effectiveness of the proposed Plan. Using the process of adaptive management, further refinement and adjustment of the Plan will continue to enhance its overall effectiveness. Mason County —Allyn UGA Stormzvater Management Plan 11 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only AS to Use \Final Text-JJS-MK3-DNA11yn.doc Section 4—Response to Public Comments. Plan Revision 4.1 Overview: Summary of Comments As summarized in Table 2-1 and the Master Comment Response Matrix referenced in Section 2, numerous comments were received on the draft plan from several sources. From a review of these comments several major common topics emerged that were used to help structure the content and format of this Addendum. These common topics were developed into additional stormwater management planning activities, which were used to further expand and refine the proposed SWM Plan for Allyn, as well as create the foundation for the Comprehensive Countywide SWM Program. The additional SWM activities that resulted from the public review/comment process included the following: • Additional documentation and assessment of existing water quality and natural resource conditions, • Additional documentation and analysis of existing SWM drainage problems, • Development of a programmatic approach to SWM, • Enhanced and expanded SWM design criteria and standards for new and redevelopment that emphasize low impact development techniques and promote water quality enhancement, • Review and enhancement of the annual maintenance program, • Redesigning the approach to capital facilities from a centralized, flow control approach to accommodate new development, to a decentralized onsite approach that emphasizes reduced impervious areas, onsite infiltration, retention of native vegetation and onsite dispersion of excess surface flows (i.e. low impact development), • Retrofitting existing development using low impact development techniques (i.e. bio- retention), • Defining the proposed water quality monitoring program, • Use of an expanded public education and involvement program, • Improved inter- and intra-agency coordination, and • Reprioritization and expansion of available funding. Each of these SWM Program elements of the proposed SWM Plan for the Allyn UGA have been further enhanced from the revised July, 2007 draft of the SWM Plan in order to increase the protection and restoration of natural resources and respond to local water quality shellfish and habitat concerns, as voiced through the public comment process Each revised, or refined SWM Program element is discussed in more detail in the following sections. Mason County Allyn UGA Stormwater Management Plan 12 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNA11yn.doc Section 4—Response to Public Comments. Plan Revision Continued 4.2 Existing Conditions• Characterization of Water Quality and Natural Resources Comment Summary: Numerous requests were made as to the need to conduct further research and document existing natural resource conditions the condition of current water quality and the status of current recreational and commercial shellfish harvesting. Additional comments were made regarding the need to correlate these observed and documented impacts with the direct discharge of undetained and untreated stormwater runoff from commercial and residential development Direction was given by regulatory agencies and stakeholders to develop retrofit plans to treat and detain runoff from existing development and establish controls for new development so runoff from future development was minimized and sensitive resource areas were protected. Revised SWAM Plan «uly, 2007). The revised SWM Plan included a section that characterized the study areas, consisting of the Urban Growth Areas, as defined in the County's Comprehensive Plan. While this review of the nature of the study area generally described the SWM Planning Area, it did not present a comprehensive view of the current state of research and monitoring. It noted water quality as an issue of regional concern and documented Ecology posted 303(d) listings and established TMDLs. Sensitive areas, consisting of wetland, stream buffers/habitat areas, fish bearing streams and aquifer recharge/protection were also recorded and mapped. Addendum Response: Due to the length of the report on local and regional water quality, shellfish and habitat resources and documented impacts from stormwater runoff, the text for this response has been included as Appendix A. Budget Impact Related to Revised Plan Duly, 2007): Based on public comment and these technical findings, substantial changes have been made to the proposed SWM Plan to protect and restore water quality, shellfish rearing, stream and fish habitat areas, as well as protect sensitive areas and shallow aquifers. The objective of the SWM planning process has shifted from the establishment of a capital improvement program to accommodate increased flows from future growth, to the development of a SWM Program that supports future growth, while also protecting and enhancing water quality and sensitive habitat areas. Mason County Allyn UGA Stormwater Management Plan'' 13 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use \Final TextJJS-MK3-DNAllyn.doc Section 4 Response to Public Comments. Plan Revision Continued As a result of this change in objectives, the entire focus of this SWM planning process has shifted, from the development of a centralized, regional system of detention, treatment and conveyance to accommodate future development, to a decentralized approach that emphasizes the use of low impact development, infiltration, dispersion, and natural vegetation retention. The various elements of this natural resource based SWM Program are discussed below. 4.3 Existing SWM Drainage Problems Comment Summary: A few citizens living within the UGA commented that the revised SWM Plan did not adequately document or address several localized existing drainage problems. Revised SWM Plan July, 2007): The revised Stormwater Management Plan for the Allyn UGA contained runoff estimates and capacity evaluations for existing drainage conveyance facilities, as well as a summary of reported drainage problems. This information was gathered from site visits, field tours with County staff, and follow up interviews with County maintenance and WSDOT maintenance crews. Additional information was collected and additional engineering analyses of the culverts under SR3 were performed and documented in the revised plans. Key information from those plans is provided in the following summary. 4.3.I Allyn UGA Three hydra] lic analyses were performed to assess existing drainage conditions and to size future drainage conveyance facilities; estimates of existing culvert/outfall capacities under SR3 and their ability to convey flow from development during the next six years were undertaken; and the sizing of CIP conveyance and outfall systems was performed under land use conditions projected to occur over the next six years. In response to a reported flooding problem at Wade Street and SR 3, the Wade Street and SR 3 culvert evaluation indicated adequate capacity and it was recommended that this problem be further investigated during annual maintenance to determine its cause (blockage higher than expected flows, etc.) The evaluation of the eleven existing WSDOT culverts under SR 3 indicated that eight of the culverts have adequate capacity for the next six years and three of the culverts require additional investigation/maintenance because of near capacity or flooding conditions. The only other reported problem is a flooding problem that occurs during major rain events at the southeast corner of the intersection of E Wheelwright and Lakeland Drive, where runoff coming down N, Lakeland Drive crosses the intersection and floods the mobile home community located on the south side of E Wheelwright Street. This problem should be Mason County — Allyn UGA Stormwater Management Plan 14 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNAIIyn.doc Section 4—Response to Public Comments. Plan Revision Continued investigated by .County Maintenance and correction proposed, as suggested in Activity #2 of the short-term stormwater CIP for Allyn Addendum Response: Proposed actions include increased annual inspections, a few local drainage studies, along with onsite fixes by the County maintenance crew. These activities are consistent with the recommendations presented in the revised SWM Plan. Cooperation with WSDOT during annual maintenance and during the proposed revisions and expansions of. SR3 also has been previously recommended. Budget Impact Related to Revised Plan July, 2007): No additional costs have been identified These small localized drainage studies and their associated fixes have been recommended for inclusion into the County's established annual maintenance program, as proposed in the revised SWM Plan. 4.4 Comprehensive Approach to SWM Comment Summary: Many comments were received about the need to make the proposed SWM Program comprehensive and to structure the SWM Program based on the requirements of the existing Puget Sound Water Quality Management Plan (PSWQMP) and the future National Pollution Discharge Elimination System (NPDES) Phase II Municipal Stormwater Permit. Revised SI"M Plan «uly, 2007): The revised SWM Plan, presented to the public in July 2007, proposed a number of programmatic SWM activities that were either required by the existing PSWQMP or would be required in a future NPDES Phase II Stormwater Permit. As requested by public comment, the existing and upcoming regulatory requirements of the PSWQMP and the Phase II Permit were used to provide the basic framework for a comprehensive, programmatic approach to SWM that also includes short and long-term capital needs to address existing conditions and future growth. These programmatic SWM elements as presented in Table 8-1 of the revised plan, are summarized in this Addendum as Table 4-1. Mason County — Allyn U G A Stormwater Management Plan 15 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNAllyn.doc Section 4 Response to Public Comments: Plan Revision Continued 4-I—Recommended SWM Programmatic and Costs Table Elements SWMP Element _ Recommended Action Satisfies Needs Program Costs ($ I,000's) PS WQMP NPDES Permit Phase II WQ Yr I Yr 2 Yr 3 Yr 4 Yr 5 Yr 6 Total Habitat Shellfish 1 Public Education* - SWM Brochure (LID) X X X $5 $5 $5 $5 $5 $5 $30 2 Involvement* Public - Organize Volunteers/Mtgs X X X $25 $25 $25 $25 $25 $25 $150 3 Illicit (IDDE) - Inventory Mapping Facility Discharges & X X X. $0 $25 $25 $0 $0 $0 $50 4 New Development* - DOE - LID Ordinance Ordinance Manual - 05 X X X $25 $25 $0 $0 $0 $0 $50 - Manual - - - 05 LID X X $25 $25 $0 $0 $0 $0 $50 Training Training - of Annual O/M Review X X X $0 $10 $10 $10 $10 $10 $50 5 Maintenance - Annual nhancements Plus X X X $25 $25 $35 $35 $35 $35 $190 I-i 6 SWM Implementation* - Develop Prog System X X $15 $15 $10 $10 $10 $10 $70 Tracking - Program Evaluation Annual X X $0 $10 $10 $10 $10 $10 $50 Mason County —Allyn UGA Stormwater Management Plan 16 H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNAllyn.doc otak Section 4—Response to Public Comments: Plan Revision Continued 7 TMDLs X X $0 $0 $0 $0 $0 $0 $0 8 SWM Monitoring* (Addressed Element Program in X X $0 $0 $0 $0 $0 $0 $0 #6) 9 Reporting* (Internal) X $10 $10 $10 $10 $10 $10 $60 10 Basin (Part Co. of study.) Planning current X X $0 $0 $0 $0 $0 $0 $0 11 Develop SWM X $50 $50 $0 $0 $0 $0 $100 Funding - Utility - SDC Study Feasibility X $50 $50 $0 $0 $0 $0 $100 12 WQ - Monitoring Annual Monitoring X X $100 $100 $100 $100 $100 $100 $600 WQ $330 $375 $230 $205 $205 $205 $1550 Total: *Future Staff ( County $55 $55 $50 $50 $50 $50 $310 1 FTE) Outside Services $275 $320 $180 $155 $155 $155 $1240 Addendum Response: Based on additional public and regulatory comments, the revised SWM Plan (presented in July, 2007) was further expanded to include additional enhancements of the following SWM Program elements described below in Sections 4.5 to 4.11. The financial impact of these additional SWM activities is summarized in the revised financial plan presented in Section 4.12. Budget Impact Related to Revised Plan Oruly, 2007). In general, no additional revenue has been proposed for the annual implementation of the proposed revised SWM Plan Annual revenues are projected to remain at about $400,000 per year, based on the multiple funding sources presented in the financial plan. The funds proposed for baseline water quality monitoring ($100K) and the funds proposed for centralized capital facilities ($100K) in the revised plan have been re -assigned to accommodate the new SWM Program priorities established through the public review process, as discussed below and summarized in Section 4.12 of this Addendum. Note that in the revised budget for this Addendum, presented in Table 4-2, some additional funds have Mason County — Allyn U G A S t o r m w a t e r Management Plan 17 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNA1Iyn.doc Section 4—Response to Public Comments: Plan Revision Continued been added to public education and illicit discharge detection and elimination in years 3, 4, 5 and 6. 4 5 Programmatic* Development Design Criteria -Emphasizes Use of 2005 Manual / LID Comment Summary: A common theme to both the public and regulatory comments, as well as those received from the Tribe and the shellfish industry, was the need for the County to adopt the Ecology 2005 Manual in order to protect sensitive areas. Numerous comments were also received recommending that the County also develop, adopt and require the use of low impact development (LID) throughout the UGA for all future development. Revised Plan Response: The revised SWM Plan recommended adoption of the Ecology 2005 Manual and the development of a new ordinance requiring LID throughout the UGA for all new development Addendum Response: These two recommendations have not been changed in this Addendum. The County is intending to adopt the Ecology 2005 Manual and to develop and adopt a LID ordinance as part of the process to adopt this SWM Plan. The LID ordinance will be adopted concurrent to the adoption of this SWM Plan, as a modification to the County's existing land use criteria. LID for all new County Roads: With the documented need to further control the impact of stormwater runoff the County has also elected to modify the County Road Design Standards so that the treatment of runoff is mandated during the design and construction of all new County roads throughout the UGA. The water quality treatment standards will stress the use of water quality filters and the use of bio-retention in roadside swales, along with other LID techniques. Budget Impact Relative to Revised Plan: These SWM recommendations are consistent with the revised SWM Plan and do not require the allocation of additional annual SWM revenues, however, the treatment of runoff from all new County roads within the UGA will increase the price of future road projects. Those costs and the corresponding increases in County road projects have not been included in this SWIM planning analysis. Mason County Allyn UGA Stormwater Management Plan 18 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNAllyn.doc Section 4—Response to Public Comments. Plan Revision Continued 4.6 Programmatic: Annual Maintenance Program -Review and Enhancement Comment Summa y.: Concerns were expressed by the regulatory agencies that runoff from existing County roads was not being properly detained or treated prior to discharge into local receiving waters. They suggested an enhanced maintenance program be put in place that updates current O/M practices and includes a new emphasis on the treatment of runoff from County roads prior to discharge into local receiving waters. Revised Plan Response: The revised SWM Plan stressed the importance of annual maintenance and recommended regular inspection of facilities within the UGA to continue to maintain vegetation, remove debris and enhance coordination with WSDOT in regard to conveyance systems under SR3 There was also the recommendation to begin to inventory the countywide SWM system of drainage facilities in anticipation of the upcoming requirement to establish an illicit discharge detection and elimination (IDDI-i) program. Addendum Response: This Addendum continues to emphasize of importance of regular annual maintenance by further recommending improvements in the annual maintenance program to conduct small localized drainage studies and construct small CIP fixes in the field on an as needed basis. County Roads has also made the commitment to enhance it efforts to detain and treat stormwater runoff within its roadside ditches by adding water quality treatment filters and other LID techniques, including bio-retention swales in order to reduce pollutant loadings to local sensitive receiving waters. Budget Impact Relative to Revised Plan: The annual SWM O/M program has been increased to conduct regular inspections of its major facilities serving the UGAs, to conduct small studies, to fix local drainage problems (an increase of $20,000 per year), and to begin to design and build water quality treatment facilities within roadside ditches (about $80,000 per year). (Note that this enhanced annual maintenance program would also include the short term CIP activities presented in the revised SWM Plan. Such activities include coordination with WSDOT and routine culvert inspection.) Mason County Allyn UGA Stormavater Management Plan 19 otal< H:Aproject\30700\30784\Reports \ Addendum \Final Text -Only JJS to Use\Final TextJJS-MK3-DNAllyn.doc Section 4—Response to Public Comments. Plan Revision Continued 4.7 CIP Strategy - Short -Term: Retrofit of Existing Development Using LID Comment Summary: One of the primary criticisms of the earlier drafts by the regulatory agencies was that the proposed SWM Plan did not address existing water quality problems or attempt to control their various sources. Agencies suggested that an effective SWM Plan for Mason County should contain adequate funding in the capital improvement program to detain and treat stormwater runoff from existing development before it was discharged into local receiving waters. Revised Plan Response: The revised plan, published in July, 2007, proposed to use annual water quality monitoring to define local water quality problems and their sources. This would allow the County to identify and prioritize existing water quality problems for future funding. Proposed water quality enhancement activities and projects would be designed and tailored to the nature and extent of the localized problem. The intent was that the highest priority problems would be addressed on an annual basis. Funding for annual water quality monitoring was proposed at $100,000 per year. No additional future funds were identified in the proposed capital program, or allocated to the fixes, that may be needed to address the identified problems. Addendum Response:: An Overview: Using LID to Replace Traditional SWM Engineering Techniques: This Addendum proposes to revise the original approach to capital projects Low impact development (LID) will be used to treat existing stormwater runoff, as well as address the stormwater capital needs associated with future development The addition of water quality treatment to address existing problems is discussed in this section and is the first part of a. two part capital improvement strategy. The second part is to continue to use LID techniques to address the stormwater needs of future development. Using LID to address future capital needs is presented in the following section, 4.8. This approach replaces the regional, centralized approach that was proposed in the revised SWM Plan to address the future capital needs within the UGA. Using a LID type of an approach emphasizes the objective to reduce existing and future impervious surfaces, optimize the retention of natural vegetation, infiltrate on site as existing soils allow, and disperse runoff in a sheetflow manner into remaining naturally vegetated areas. This approach is in contrast to the traditional engineering approach that would typically route all runoff from the site into a network of regional collection and conveyance facilities that would lead to a series of large onsite or regional detention and treatment facilities, where the runoff would be treated prior to its discharge to local receiving waters. Mason County Allyn UGA Stormwater Management Plan 20 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNAllyn.doc Section 4 Response to Public Comments: Plan Revision Continued L sing LID to Treat Existing Stormwater Runoff: Rather than relying on water quality monitoring and enhanced maintenance to address the existing water quality problems as presented in the revised SWM Plan, funds have been shifted from annual water quality monitoring to an aggressive program to retrofit the existing drainage system for water quality treatment. Using LID techniques, primarily in the form of bio-retention swales, runoff from existing development would be detained and treated prior to discharge. The emphasis would be on providing water quality treatment The duration and type of detention would be primarily that needed to provide effective treatment rather than rate control. The goal would be to design and build ten to twelve LID facilities throughout the most urban areas of the UGA over the next six years, approximately two per year. The approach would be to locate approximately five/six of these facilities on existing County property, primarily within the County road right-of-way. The other five/six facilities would be located on existing private property, primarily on the downstream areas of the larger expanses of existing impervious surfaces, such as parking lots and outdoor storage/shipping receiving areas. Retrofitting possibilities for individual commercial properties include infiltration of roof runoff, collection and pretreatment of road and parking area runoff in rain gardens or catch basins with water quality filters, followed by infiltration and treatment within a soil matrix contained in a bio-swale/bio- retention type of design. Working with existing residences and commercial businesses would be on a cooperative basis and it is the intent to develop incentives to entice the business community to participate. Financial partnering through the use of grants, loans, and other in -kind services is also being considered. (A technical overview of the use of LID (i.e., bio-retention facilities) for water quality treatment is presented below.) Note that the County is also considering the treatment of runoff from County roads using water quality treatment filters of various designs and removal mechanisms to address the runoff from its impervious surfaces. One device involves the use of a bio-treatment medium within a suspended filter device that would be placed within an open drainage ditch along the County road. These devices would be used in replace of or in concert with the above bio-retention LID types of devices. Technical Review of the Use of LID for Local Water Quality F nhancement: Retrofitting of existing commercial areas with water quality treatment facilities using LID will improve the quality of runoff being discharged from those areas. Bio-retention facilities are a good candidate for retrofits at commercial sites with Hydrologic Soil Type A and B soils as these Mason County —Allyn UGA Stormwater Management Plan 21 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text JJS-MK3-DNAllyn.doc Section 4—Response to Public Comments. Plan Revision Continued soils are well suited for infiltration of stormwater. With some design modification (i.e., adding an under dram) LID techniques could also be used in Type C and D soils. The 2005 Ecology Stormwater Design Manual lists bio-retention facilities/rain gardens as one option to satisfy basic and enhanced water quality treatment requirements. The 2005 Ecology recommends both Appendix III-C of the 2005 Ecology Manual and The Low Impact Development Technical Guidance Manual for Puget Sound (LID Manual) for design guidance. Both design references area available on the World Wide Web. For a typical commercial site (assuming 85 percent impervious cover and 15 percent landscape cover) located in outwash soil, approximately ten percent of the site is required for a bio-retention facility/rain garden (as determined using MGS Flood to size an infiltration facility that infiltrates at a rate of 1-inch per hour). For example, a 60-foot by 100-foot commercial lot (0.14 acre) would require a 600 square -foot bio-retention facility. The project cost, which includes construction and design costs, of a 600 square -foot bio-retention/rain garden is $39,000 (approximately $7 per square foot of area treated). Runoff from roofs does not require water quality treatment if kept separate from street and parking lot runoff. The development of a standard bio-retention design and set of specifications for the UGA that could be adapted to specific sites could help reduce the cost of implementing these facilities. The following figure is taken from the LID Technical Guidance Manual for Puget Sound, 2005, courtesy of Puget Sound Partnership and illustrates a typical bio-retention cross section. This schematic is followed by photos of completed bio-retention facilities (also courtesy of Puget Sound Partnership). In areas of till soils, where infiltration rates are low, a bioretention with an underdrain system or a different type of water quality treatment option, not relying on infiltration, may need to be selected from the Ecology list of treatment options (located in volume 5 of the 2005 Ecology Manual). Mason County Allyn UGA Stormwater Management Plan 22 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNA11yn.doc Section 4—Response to Public Comments: Plan Revision Continued filter strip ater flow ..... i. Bioretention cross section, without underdrain Bioretention at Street Edge Alternatives (SEA) Project Seattle selected native plants and hardy cultivars planting soII mix no liner or filter fabric From the LID Technical Guidance Manual for Puget Sound, 2005 Mason County — Allyn U G A S t o r m w a t e r Management Plan 23 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use \Final TextJJS-MK3-DNAllyn.doc Section 4 Response to Public Comments: Plan Revision Continued Bioretention at medical center, Olympia Photo by Bruce Wulkan, Puget Sound Action Team Budget Impact Relative to Revised Plan: The annual allocation of $100,000 to water quality monitoring presented in the revised SWM Plan has been re -assigned to provide detention and treatment of runoff from existing development throughout the UGA, with emphasis on the more commercial areas and areas of high traffic use The cost of a bio-retention facility on County right-of-way has been estimated to be about $40,000, depending on local soils and site conditions. Approximately two of these facilities would be designed and built every year over the next six years. About $20,000 would be retained on an annual basis to monitor the performance of one representative bio-retention facility in order to measure performance. Collected information will be used to confirm treatment effectiveness and enhance future designs. (Note that the short-term CIP projects, consisting primarily of maintenance related activities, have been included in the enhanced annual maintenance program described in Section 4.6. Mason County Allyn UGA Stormwater Management Plan 24 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text JJS-NII{3-DNAllyn.doc Section 4—Response to Public Comments. Plan Revision Continued 4.8 CIP Strategy - Long -Term: A Decentralized Approach Emphasizing LID Comment Summa y: The regulatory agencies suggested that the County revise the Comprehensive Plan (Comp Plan) for the UGA in order to further enhance the use of LID techniques. The concept is to use additional LID approaches to address the drainage needs of all new development by changing the way the surface of the land is designed and laid out for future developed. This approach would take the form of revised development standards that would not change the densities presented in the Comp Plan, but would provide guidance that would reduce the amount of impervious area using LID approaches to land development These land use standards would be used, and would work in concert with, the required 2005 Ecology Manual and the onsite LID ordinance. The goal of this type of an LID -based approach to land use development is to reduce/minimize the amount of new impervious surface, while optimizing the retention of native vegetation. It would emphasize the use of onsite infiltration and the dispersion and treatment of surface water runoff. If used on a uniform basis throughout the UGA, this type of a regional decentralized approach to stormwater management could be used in lieu of the design and construction of the traditional large, costly centralized collection, detention, treatment, and conveyance/outfall facilities that require large parcels of land for effective performance. Revised Plan Response: The revised SWM Plan promoted the use of LID by the development and the adoption of an LID ordinance that would work in concert with the Ecology 2005 manual. The SWM Plan promoted the use of onsite detention and infiltration. The onsite drainage systems would be designed to operate along with regional collection, detention and treatment systems that would be primarily paid for by developers at the time the site was developed. Depending on the effectiveness of these systems, the County may or may not be required (at a future date) to design and build additional regional facilities to protect sensitive downstream natural resources and address the accumulative impacts of numerous develops within common watersheds and drainage basins. Regulatory agencies characterized this type of an approach as a traditional, regional and centralized approach of providing stormwater management facilities to support new development. Addendum Response: The County recognizes the potential advantages of taking an. LID -based approach to new development through the UGA. It supports the concepts presented by the regulatory agencies and recognizes numerous advantages of adopting such an approach These advantages would include less disruption of native land resulting in less runoff, and less erosion and sedimentation. This approach would both preserve and protect natural resources by providing enhanced protection of onsite and downstream sensitive areas and Mason County Allyn UGA Stormwater Management Plan 25 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNAllyn.doc Section 4—Response to Public Comments. Plan Revision Continued natural resources. It also reduces the cost of the County's long-term capital facilities program and may reduce future maintenance costs as well In supporting this concept of land development and an alternative approach to providing future capital facilities for SWM throughout the UGA, the County will commit to further develop and explore these concepts by developing the required land use standards and presenting to the public and BOCC for review during the annual review and update of the County's Comprehensive Plan. Budget Impact Relative to Revised Plan: In response to this LID type of an approach to providing long-term SWM CIP, the $100,000 that had been annually set aside for long-term capital projects has been reassigned to other SWM Program elements and priorities. These other SWM Plan priorities, based on public and regulatory comment, include enhanced maintenance consisting of localized drainage studies and small CIP fixes ($20,000/year) and treatment of runoff in roadside ditches ($80,000/year). The long-term CIP program to provide four centralized regional collection and conveyance systems, costing $2.53M and beginning in Year #10, has been cancelled. 4.9 Programmatic: Baseline Water Quality Monitoring Comment Summary: Numerous comments cited the significant amount of monitoring information available from state, local agencies and interest groups that documented water quality impacts from stormwater runoff to sensitive receiving waters and other natural resources. Several also expressed concern over the magnitude and immediacy of the need for action to correct observed and previously documented problems. Some suggested treatment approaches such as retrofitting existing development and the use of LID techniques. Others said that all runoff should be treated before it entered into local streams or receiving waters. Revised Plan Response: The June 2007 plan proposed the use of a baseline water quality and habitat study within the UGA to characterize the nature of stormwater runoff and establish the severity of its impacts. Results were to be used by the County to prioritize problem areas and guide the amount and type of future investments that would be needed to address local impacts. In the July 2007 revised SWM plan, this monitoring activity was expanded and additional funds were added to make water quality monitoring a major element of the new SWM Plan. Mason County Allyn UGA Stormwater Management Plan 26 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNAllyn.doc Section 4 Response to Public Comments. Plan Revision Continued Addendum Response:: Based on the response of regulatory agencies and the public, as documented in Section 4.2 above, there appeared to be a general consensus that stormwater runoff was already a major problem for water quality, fish/habitat and shellfish within North Bay and the south end of Hood Canal. They suggested that while additional monitoring would be helpful, the real need was to retrofit existing SWM facilities to detain and treat the runoff from all developed areas. As a result, most of the funds for the water quality monitoring program were shifted to help pay for retrofitting runoff from existing development. The remaining funds (about $20,000) will be focused on characterizing the water quality treatment effectiveness of the proposed bio-retention facilities that will be used to treat runoff from existing development. Budget Impact Relative to Revised Plan: No net financial impact $80,000 will be shifted from water quality monitoring to detaining and treating runoff from existing development; $20,000 will be used annually to characterize the water quality treatment effectiveness of a bio-retention low impact development technique. 4.10 Programmatic: Public Education / Involvement Comment Summary: Regulatory agencies commented on the need for additional public education and outreach, as well as on -going public involvement. Most thought that a diversity of education and outreach techniques on an annual basis was needed. Some mentioned the need for the education of residents and the development incentives for them to take corrective action on their own properties. Many expressed the need to develop support for the plans through an on -going public involvement program. Revised Plan Response: The revised SWM Plan recommended distribution of a countywide brochure to the public addressing local stormwater pollution issues and homeowner solutions that included the benefits of LID and drew from available PSAT educational resources. The revised plan also included engaging community stakeholders in SWM planning and implementation within their respective UGAs. This included organizing volunteers to assist in Stream Team activities and various volunteer programs that could include water quality monitoring. Addendum Response:: In this Addendum, the County has agreed to the establishment of a SWM Advisory Committee to assist County staff in the development of the County -wide SWM Plan. Mason County Allyn UGA Stormwater Management Plan 27 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text JJS-MK3-DNA11yn.doc Section 4—Response to Public Comments: Plan Revision Continued As the County develops and implements various public education involvement activities, it would be good to expand the scope or theme of these activities so that everyone, both residential homeowner and business owner/operator, has a defined role in the protection, cleanup and enhancement of local water quality, streams, and shellfish rearing areas. 0 For Homeowners: A Source Control Brochure that addresses ways that homeowners can reduce stormwater impacts through source control strategies such as reducing flows, disconnecting and directly infiltrating roof runoff, retaining or re-establishing vegetation onsite, carefully conducting pest management, reduction of lawn chemicals, proper disposal of pet waste, proper disposal of household hazardous wastes, etc. For Business: A Source Control Brochure that addresses ways that businesses can reduce stormwater impacts through source control strategies such as spill prevention, covering waste disposal areas to avoid stormwater contamination, integrated pest management, separating and infiltrating roof runoff, proper maintenance practices and frequencies, and retrofitting by adding bio-swales and ram gardens into their landscaping to enhance detention, infiltration, and treatment prior to discharge from their site. Future activities may include: exhibiting at local fairs/public gatherings use of the County's web site, mailings, brochures and volunteer programs for stream team plantings and water quality monitoring. Budget Impact Relative to Revised Plan: The revised SWM Plan provided $30,000 per year over the next six years for public involvement and education. The annual budget for public education has been increased to $25,000 per year in years.3, 4, 5 and 6. 4.1 I Programmatic: Inter/Intra-Agency Coordination Comment Summary: In general, agency coordination did not receive much attention in the comments received from the public. The regulatory agencies, however cited the critical need for coordination with WSDOT in order to address local road runoff and common water quality, habitat and receiving water objectives. Jointly -funded water quality detention and treatment projects were also suggested to address regional needs. Revised Plan Response: Intra-Agency Coordination: The revised SWM Plan recommended coordination with WSDOT on maintenance, creek relocations, streetscape improvements and joint -use stormwater facilities. Mason County — Allyn U G A S t o r m w a t e r Management Plan 28 H:Aproject\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNAllyn.doc otak Section 4—Response to Public Comments: Plan Revision Continued Inter -Agency Coordination: The revised SWM Plan also recommended internal coordination with County Transportation and Parks programs to incorporate LID and water quality benefits into transportation improvements and planned park locations within the UGA. Addendum Response: Stormwater impacts on receiving waters are from diverse sources and often result in cumulative effects from the various land uses within the watershed Effective stormwater management requires teamwork from all the players/contributors to address those impacts. For this reason, this Addendum is including additional recommendations for both agency and internal coordination. In the future, the County intends to increase its level of coordination and cooperation with various local and State agencies, especially WSDOT, City of Shelton and County Public Health. Cooperation is needed on such issues as the design and funding of common local SWM projects, establishment of common design criteria within UGA areas and integrated programs to protect shellfish and restore water quality. The joint implementation of the Oakland Bay and Annas Bay shellfish response plans is already underway and could be used as templates of how to work together effectively to achieve common natural resource goals. These activities would complement and be in addition to the coordination activities already presented and discussed in the revised SWM Plan (July, 2007) Budget Impact Relative to Revised Plan: The revised SWM Plan provided $30,000 per year over the next six years for public involvement and education. While no additional budget has been specifically recommended in this Addendum for inter/intra-agency coordination, the addition of a County SWM Program Manager will help facilitate the overall coordination of SWM activities throughout the County and the UGA. The cost of enhanced coordination should be able to be absorbed within SWM Program Element #6, SWM Program Implementation. 4.12 Programmatic: Funding Comment Summa y: The regulatory agencies stressed the need for the establishment of adequate levels of revenue to effectively implement the proposed SWM Plan on an annual basis. They proposed setting up a countywide SWM utility and the establishment of developer impact fees. Other comments were received from the public that pointed to the need for the County to hire and train new staff to help develop and implement the proposed SWM projects and activities. Mason County — Allyn UGA Stormwater Management Plan 29 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNAIlyn.doc Section 4 Response to Public Comments. Plan Revision Continued Revised Plan Response: The revised SWM Plan developed and presented a financial plan that was annually supported by a diversity of funding sources that included the formation of a UGA-wide SWM Utility. Potentially available annual revenues of up to $374,000 to $440,000 were forecasted, from seven different revenues sources. Annual SWM Program revenue needs of about $400,000 were estimated. The SWM utility was estimated to bring in about $100 000 annually, based on monthly rates of about $120 per year (or about $5-$10 per month) for the average residential homeowner, with commercial land owners paying more based on the amount of impervious area on their parcel. Addendum Response• A revised financial plan for the SWM Plan has been established and is presented in this Addendum An annual SWM Plan budget of about $400,000 has been retained, and the same revenue sources and annual estimates of revenue have been maintained. Projected annual expenditures match projected annual expenditures of about $400,000. The various financial changes recommended above are summarized in Table 4-2. Table 4-2 Recommended Allyn SWM Program Elements and Costs SWMP Costs ($ I ,000's) Recommended Action Yr I Yr 2 Yr 3 Yr 4 Yr 5 Yr 6 Yrs 7-26* Element 1 Public Education $5 $5 $25* $25* $25* $25* 2 Public Involvement $25 $25 $25 $25 $25 $25 3 $0 $25 $25* $25* $25* $25* -- Illicit Discharges (IDDE) 4 $50 $60 $10 $10 $10 $10 New Development 5 Maintenance $25 $25 $35 $35 $35 $35 -- 6 $15 $25 $20 $20 $20 $20 -- SWM Prog. Implementation 7 TMDLs $0 $0 $0 $0 $0 $0 -- 8 $0 $0 $0 $0 $0 $0 -- SWM Prog Monitor (In #6) 9 Reporting* $10 $10 $10 $10 $10 $10 -- (Internal) 10 Basin Planning $0 $0 $0 $0 $0 $0 -- 11 Funding $100 $100 $0 $0 $0 $0 -- 12 WQ Monitoring: Baseline $0 $0 $0 $0 $0 $0 Programmatic Subtotal: $230 $275 $150 $ 150 $150 $ 150 -- CIP 1 Yrs I (In #5) $0 $0 $0 50 $0 $0 -- -6:WSDOT/CuIrts 2 $0 $0 $0 $0 $0 $0 -- Yrs7-26:Four Reg. CIP (In #5) $0 $0 $0 $0 $0 $0 -- CIP Subtotal.: Adden. 4.6 Enhanced 0 & M: Study/Fixes $20 $20 $20 $20 $20 $20 -- Mason County Allyn UGA Stormwater Management Plan 30 H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNAllyn.doc otal< Section 4—Response to Public Comments. Plan Revision Continued 4.6 WQ Treatment of Rd Ditches $80 $80 $80 $80 $80 $80 -- 4.7 Retrofits for Water Quality $80 $80 $80 $80 $80 $80 -- 4.7 WQ Monitoring: Retrofit LID $20 $20 $20 $20 $20 $20 Addendum Subtotal $200 $200 $200 $200 $200 $200 Total: = $384/yr) $430 $475 $350 $350 $350 $350 -- (Avg * Increased in the Addendum over the revised SWM Plan, July 2007. Budget Impact Relative to Revised Plan: In general, the following recommendations have been made to the annual budgets presented in this Addendum. • The $100,000 water quality monitoring program has been reduced to $20,000 to evaluate the water quality treatment effectiveness of bio-retention facilities the $80,000 balance has been used to .design and build water quality retrofit facilities • The $100,000 set aside annually for long-term centralized capital projects has been reassigned to other SWM Plan priorities listed below. • Annual maintenance has been increased by $20,000 to conduct small localized drainage investigations and complete small CIP fixes in the field. • A short-term CIP program costing $80,000 per year to retrofit the drainage system to detain and treat stormwater runoff from existing impervious surfaces has been proposed. The short-term CIP retrofit program consists of the design and construction of 10-12 bio-retention facilities throughout the more urbanized areas of the UGA over the next six years at the rate of about two facilities per year. Partnering with local property owners will be needed. • The hiring of one staff person to develop, supervise and implement the County's SWM Program has been recommended. Staff responsibilities would includes the funding and implementation of both the Allyn and Belfair SWM Plans. Cost has been estimated to be about $50,000 to $80,000 per year, which could be split between the two SWM Plans. (Note that funding for a staff position can be realized if SWM Program hiements 1, 2, 4, 6, 8 and 9 are performed internally by County Staff.) • Remaining funds, of about $80,000 annually, may be assigned to the enhancement of the annual maintenance program to review and upgrade O/M practices and include retrofitting County road drainage ditches to detain and provide water quality treatment. • Note that as annual revenues increase and more knowledge and experience is gained in implementing the proposed SWM Plan within the UGA, this initial SWM service level as defined in Table 4-2, will be subject to review and revision on an annual basis as part of the County s annual budgeting process. Mason County —Allyn UGA Stormwater Management Plan 31 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNAllyn.doc Section 5—Summary of Revisions to Original Draft SWM Plan 5.1 Link between the SWM Plan and Shellfish in North Bay Throughout the development of this Addendum to the SWM Plan for the Allyn UGA, the County has focused on improving local water quality and its related stream/habitat areas. It recognizes and understands the direct link between clean stormwater runoff and the continuation of healthy shellfish rearing areas. It is for these reasons that. • The entire SWM planning strategy has been shifted from supporting new development by collecting and concentrating stormwater runoff and constructing large centralized regional SWM facilities, to an entirely decentralized approach that is based on LID techniques that minimized the impacts of future land use changes, as well as promotes the design and construction of onsite LID systems. • A facility retrofit program has been developed to detain and treat the runoff from existing development using LID techniques. • County road runoff will begin to be treated by retrofitting existing facilities, as well as by adding water quality treatment to all new County road designs. • The important role of regular maintenance has been developed and continues to be stressed, further expanding the need for adequate staffing and funding of O/M programs during the annual budget cycle.. • The adoption of the Ecology 2005 Manual and the development and adoption of a LID ordinance continue to be promoted and are recommended. • Citizen and stakeholder input and involvement has been emphasized and expanded to include the development of a citizen advisory committee and a pubic process for the annual review and update of the SWM Plan(s). Citizen volunteers may also play a key role in future program implementation including water quality and habitat monitoring, as well as public education. • The establishment of a self-sustaining dedicated financial program has been developed and has been promoted that includes the development of a stormwater utility, as well as the hiring of a supervisor to help guide the continued development and implementation of the County's SWM Program. Mason County —Allyn UGA Stormwater Management Plan 32 otak I -:\ project \30700\30784\Reports \Addendum\Final Text -Only JJS to Use\Final Text JJS-MK3-DNA1Iyn.doc Section 6—Future Public Involvement and Future Updates to the Plan 6.1 Ongoing Public Involvement The County has made the commitment to establish a SWM citizen advisory committee to help guide the development of the Countywide SWM Plan. It is expected that this group will continue to play an active role in the public review of the Countywide and Hoodsport SWM Plans, as well as in the annual updates to all of the County's SWM planning efforts which include future updates to the SWM Plans of Allyn and Belfair. 6 2 Future Updates to the SWM Plan The County recognizes the cooperative effort needed for successful and effective SWM planning throughout the County. It intends to conduct an annual review of the effectiveness of each of these proposed SWM Plans and their ability to be integrated into a comprehensive and effective countywide strategy and implementation plan Annual refinements to both the SWM Plan activities, as well as their associated budgets and associated service levels, are anticipated This review and refinement will continue to occur through an open and well advertised public review process. Mason County Allyn UGA Stormzvater Management Plan 33 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text JJS-MK3-DNAllyn.doc References S. Glascoe and Beale H., Alberti, M., Bidwell, M., Christy, Aimee, May, C. 2006. New Approaches to Shellfish Protection in Puget Sound: Essential Strategies for Preserving Watersheds and WateroQuality for Shellfish Harvesting A collaboration between the Puget Sound Action Team, University of Washington Urban Ecology Research Laboratory, Pacific Shellfish Institute, and Battelle Marine Science Laboratories Booth, D B 2000. Forest Cover, Impervious -Surface Area, and the Mitigation of Urbanization Impacts in King County, Washington. Prepared for King County Water and Land Resources Division. Seattle, Washington. 18 pp. (available at http://depts.washington.edu/cuwrm/research/forest.pdf) Booth, D B , D Hartley and R. Jackson. 2002. Forest Cover, Impervious -Surface Area, and the Mitigation of Stormavater Impacts. Journal of the American Water Resources Association. 38(3):835 845. Glasoe, S. and A. Christy. 2004. Literature Review And Analysis: Coastal Urbanization And Microbial Contamination Of Shellfish Growing Areas Stuart Glasoe and Aimee Christy Puget Sound Action Team, State of Washington Olympia, Washington. Publication #PSAT04-09 Oakland Bay TMDL 2007. hap: //www.ecy.wa.gov/programs /wq/tmdl/oakland bav/index.html) Ecology 2001 Union River Fecal Coliform Bacteria Total Maximum Daily Load Study, October 2001, Publication No. 01-03-038. http://www.ecy.wa.gov/biblio/0103038 html Fcology 200?. Union River Fecal Coliform Water Clean-up Detailed Implementation Plan http.//www.ecy.wa.gov/biblio/0310066.html Washington State Conservation Commission (WSCC). 2003. Salmon Habitat Limiting Factors Water Resources Inventory Areas 15 (Wiest), Kitsap Basin, and 14 (North, Kennedy-Goldborough Basin. Prepared by Michael Kutde, Jr., Washington State Conservation Commission. (http://salmon scc.wa.go/reports/wrial4and15.pdf) WRIA 14. 2006. Watershed Management Plan Kennedy Goldsborough Watershed Final Unadopted Draft / May 2006 Prepared for the WRIA 14 Planning Unit under Grant G0000107 by Plateau Technical Communication Services) Mason County — Allyn U G A S t o r m zv a t e r Management Plan 34 otal< H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final TextJJS-MK3-DNAllyn.doc References Continued WDOH. 2006a. Washington State Department Of Health Office Of Shellfish And Water Protection Annual Growing Area Review forAnnas Bay. http:/Pw•ww.doh.wa.gov/ehp/sf/Pubs /gareports.pdf WDOH. 2006b. Washington State Department Of Health Office Of Shellfish And Water Protection Annual Growing Area Review for North Bay. http://www.doh wa.gov/ehp/sf/Pubs/gareports.pdf WDOH. 2006c. Washington State Department Of Health Office Of Shellfish And Water Protection Annual Growing Area Review for Oakland Bay. http://www.doh.wa.gov/ehp/sf/Pubs/gareports.pdf WDOH. 2006d. Washington State Department Of Health Office Of Shellfish And Water Protection Annual Growing Area Review for Pickering Passage. http://www.doh.wa.gov/ehp/sf/Pubs/gareports.pdf Mason County —Allyn UGA Stormwater Management Plan 35 otak H:\project\30700\30784\Reports\Addendum\Final Text -Only JJS to Use\Final Text-JJS-MK3-DNA11yn.doc Appendix A Appendix A — Water Quality, Fish, Shellfish and Habitat Report Introduction Water quality, shellfish, and freshwater and marine habitat conditions are vital water and natural resource issues in Mason County. This addendum to the Stormwater Management Plans for the cities of Belfair and Allyn includes detailed information regarding the status of existing conditions within Mason County as well as a summary of recommendations and on- going protection efforts for these areas of Puget Sound. This section of the amendment is organized to reflect the conditions of water resources in Mason County and, accordingly, is presented with a focus on Water Resource Inventory Area (WRIA) information. Because this region of Puget Sound is so rich in natural resources, there are many organizations (agencies, private companies, and citizens) that are actively working toward the protection of water quality and aquatic habitat. This summary is meant to encapsulate the existing conditions with regard to water quality and shellfish and salmon habitat Due to the broad scope of these issues and their importance to this region, the following review should only be considered a summary or overview of the present state of knowledge and the current activities underway to protect and enhance these regional resources. Mason County includes four separate Water Resource Inventory Areas (WRIAs) including WRIAs 14 (Kennedy-Goldsborough watershed), 15 (Kitsap watershed), 16 (Skokomish- Dosewallips watershed) and 22 (Lower Chehalis watershed), as shown in Figure 4-1. Nearly the entire watershed area of WRIA 14 lies within Mason County (or about 85%, approximately 207,872 acres of the watershed s 244,173 acres). The primary freshwater, marine, and nearshore habitats are within the northeastern portion of WRIA 14 and the western portion of WRIA 15. The western portion of WRIA 15 within Mason County contains only 80,953 acres, or approximately 13% of the 631,196 acres within the WRIA 15 watershed. The cities of Allyn is within WRIA 14, the Kennedy-Goldsborough watershed. The Allyn Urban Growth Area (UGA) is comprised of 1,167 acres in the watershed. Only a small portion of the WRIA 15 area, or about 2,328 acres, comprises the City of Belfair UGA. Although the areas within these two UGAs are relatively small compared to the watersheds, the natural resources located within each of these areas, associated with the North Bay area of southern Puget Sound and the lower end of Hood Canal, are considerable. The water quality, fish and shellfish conditions for WRIAs 14 and 15 are briefly described below. This review is presented according to the following topics: Mason County Stormwater Management Plan 2 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A - Water Quality, Fish, Shellfish and Habitat Report Continued Existing Conditions Existing Water Quality Conditions Existing Biological Resources Shellfish Salmonid/Fish Resources Monitoring, Protection, and Enhancement Mason County: Stormwater and Water Quality Belfair and Allyn Urban Growth Areas City of Allyn and North Bay Water Quality Shellfish Salmonid Habitat: Stream and Marine Nearshore City of Belfair and South Hood Canal Water Quality Shellfish Salmonid Habitat: Stream and Marine Nearshore Suggestions for Resource Management Stormwater Management / Watersheds Habitat Freshwater: Stream/Riverine Marine: Nearshore Habitats Mason County Stormwater Management Plan 3 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued Existing Conditions Existing Water Quality Conditions The quality of water in many of the WRIA 14 and 15 streams, lakes, and nearshore areas has been degraded, likely due to a combination of various land use activities including, stormwater runoff development of impervious surfaces, logging practices, wastewater from septic systems, and agricultural activities The Union River and parts of Southern Hood Canal, Oakland Bay and Hammersley Inlet are on the most recent 303(d) list of impaired waters because of high fecal coliform bacteria and/or low stream temperatures Water quality problems have lead to shellfish harvesting closures in several WRIA 14 and 15 areas in Mason County including Oakland Bay, Hammersley Inlet, Pickering Passage, Annas Bay and Hood Canal Station #9, as shown in Figure 4-1. These areas have been closed to shellfish harvesting because of high fecal coliform concentrations, and are considered as threatened shellfish growing areas by the Washington Department of Health (WDOH) (Figure 4-2). These closures have been linked to stormwater runoff and failing onsite sewage systems, and are threatening the shellfish industry. Fcology is currendy working to set Total Maximum Daily Loads (TMDLs) for both nearshore and freshwater areas with observed water quality problems. These include the fecal coliform TMDL for the Union River that was written in 2001, and the fecal coliform and temperature TMDLs currently being developed for Oakland Bay. Existing Biological Resources Shellfish Mason County is an important shellfish rearing and harvesting region of Puget Sound. There are currendy many areas for both the public and private harvest of a variety of species including oysters, clams, mussels and geoducks. Particular attention is being paid to the area near the Allyn UGA within North Bay, which contains the Olympia oyster —the only native oyster species in the Washington State. This species of oyster is currently a candidate species for state listing under the Washington State fi,ndangered Species Act and is a species of concern under the federal Fi,ndangered Species Act (ESA). The shellfish resources throughout Puget Sound are being threatened by stormwater runoff, septic discharges, and other types of pollution. Many shellfish rearing and harvesting areas have been impacted. Some of the public and commercial harvesting areas are now decertified Mason County Stormwater Management Plan 4 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A -- Water Quality, Fish, Shellfish and Habitat Report Continued and others continue to be threatened by increasing development and its associated stormwater runoff. Within the Mason County area two shellfish protection/enhancement districts have been established. One within the Annas Bay area of Hood Canal and the other, covering a much larger geographic area, to restore shellfish resources within Oakland Bay. These shellfish areas are shown in Figure 3-1 as sensitive water quality areas. Salmonid/Fish Resources WRIA 14 streams and the Hood Canal nearshore habitat support a number of salmonid species. Unfortunately, the most productive habitats such as salt marshes, lagoons, and shallow bays have already been severely altered or lost within the nearshore areas of Mason County (Kuttel, 2002). Summer and fall chum, coho, and chinook salmon, as well as steelhead and both anadromous and resident coastal cutthroat trout use the streams draining to and the neashore waters of Hood Canal. Of these species, Hood Canal summer chum salmon and Puget Sound Chinook were listed as threatened by the National Marine Fisheries Service under the ESA in March 1999. Forage fish such as surf smelt and sand lance, both important food species for anadromous salmonids, also use the nearshore. These species spawn near the high tide line on sand and gravel beaches found along the intertidal zone in Mason County. Within the Belfair drainage, the Union River and its associated tributary streams is especially important to the rearing and sustaining of many of the various salmonid populations listed above H,qually important is the Sherwood Creek watershed adjacent to the Allyn UGA, which currently also supports a variety of salmonid species. Both the Union River and Sherwood Creek systems and their salmonid resources are examined in greater detail in the following sections. Monitoring, Protection, and Enhancement To ensure that these resources are maintained, various regulations, programs, and monitoring efforts are in place to help protect and maintain ecosystem health. New regulations have recently been established requiring Puget Sound health officers to designate Marine Recovery Areas (MRAs) where specific water quality problems have been identified. Under these new regulations, MRAs must be designated when the Mason County health officer determines off -site stormwater systems (OSS) are a significant factor contributing to concerns associated with the degradation of shellfish growing areas MRAs may also be designated when marine waters are listed by the Department of Ecology (Ecology) for water Mason County S t o r m w a t e r Management Plan 5 otak H:\project\30700\30784\Reports\Addendum\Appendix A doc Appendix A -- Water Quality, Fish, Shellfish and Habitat Report Continued quality degradation, including low dissolved oxygen levels, fecal coliform bacteria, or high nitrogen concentrations. Under these regulations, the 2006 legislation directed the Mason County Department of Health Services and Mason County's health officer (as well as the other 11 Puget Sound counties) to take further actions to reduce fecal coliform bacteria pollution and the degradation and loss of marine life in Hood Canal and other marine waters in Puget Sound caused by low -dissolved oxygen conditions. It is envisioned that these MRAs will coordinate with existing TMDL and shellfish recovery districts, integrating action plans and correlating monitoring and data interpretation. Mason County Stormwater and Water Quality Within Mason County, the transformation or urbanization of landscapes from rural to urban land uses has resulted in an increase in impervious surfaces and associated stormwater runoff. During urbanization, forests are cleared and soils are stripped, compacted, and covered over with roads, buildings, and other impervious surfaces. Under this altered scenario, the precipitation that was previously taken up by native vegetation or that moved slowly into and through the soil layer as subsurface flow is now converted to surface overland flow. This results in changes in stormwater quantity and quality. Stormwater quantity is altered through the combination of reduced retention and enhanced conveyance, resulting in changes in seasonal runoff patterns such as lower stream baseflows in the summer, and more stormflow events with higher peak flows that rapidly rise and fall in the winter (Booth 2000). In 2004, the Puget Sound Action Team (PSAT) conducted a literature review of studies linking human modification of the natural landscape with direct and significant effects on the condition of aquatic ecosystems. Both streams and nearshore marine environments were evaluated, and the primary impacts included the fragmentation and loss of habitat, as well as the degradation of water resources and water quality (Glasoe and Christy 2004). One area that was identified as being especially sensitive to changes in stormwater runoff was the nearshore environment used to grow shellfish. The PSAT found that shellfish growing areas receive pollution along three main pathways: (1) direct discharges (sewage outfalls, boaters, marine mammals, etc.); (2) subsurface flows (shoreline onsite sewage systems); and (3) overland flows (stormwater runoff and stream flows) (Glasoe and Christy 2004). Mason County Stormwater Management Plan 6 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A— Water Quality, Fish, Shellfish and Habitat Report Continued The studies reviewed by the PSAT also documented high levels of selected pathogens in stormwater discharges. They determined that fecal coliform bacteria concentrations are influenced by several factors including rainfall, land uses, fecal pollution sources, and runoff potential of different surfaces and landscapes (Glasoe and Christy 2004). This is the same correlation identified by Ecology and WDOH, which observed a significant rise in fecal coliform concentrations during storm events within the Mason County UGA's. It has been shown that moderate levels of development within Puget Sound watersheds (10 to 25 percent impervious cover) degrade aquatic habitat quality, including shellfish growing areas, and the degradation increases as development intensifies (Booth 2000; May et al 1997). Low impact development (LID) strategies were identified in several studies in the literature review (Glasoe and Christy 2004) as the most effective means of minimizing the impacts of stormwater runoff rather than strictly relying only on structural BMPs. LID strategies are being adopted by many jurisdictions in King, Snohomish, and Thurston Counties as an effective development strategy to minimize stormwater impacts. These same measures would also benefit Mason County in improving water quality conditions within both freshwater and marine environments Belfair and Allyn Urban Growth Areas Water quality in and around both the Belfair and Allyn UGAs has been reported as degraded (see below for specific examples). Water quality degradation in these areas is associated with both marine and freshwater systems, and is a source of concern for shellfish harvest, salmonid and forage fish habitat, and recreational usage of aquatic resources. Currently, fecal coliform bacteria levels represent the primary contaminant of concern in both the Belfair and Allyn areas. City of Allyn and North Bay Water Quality The City of Allyn and the surrounding area comprise the watershed of North Bay (Figure 4- 3), and include important shellfish rearing areas, as well as habitat for salmon and forage fish. This area has a long history of marine water quality concerns stemming from runoff associated with both shoreline and upland sources; in particular on -site sewage system failures in the early '90s led to closure of many shellfish beds. Although the Allyn Wastewater Treatment Plant improved the marine water quality from failing septic systems Mason County Stormwater Management Plan 7 otak 4:\project\30700\30784\Reports \ Addendum \Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued at the time, the area is currently showing a continued overall decline in water quality conditions, principally as a result of elevated fecal coliform levels and low dissolved oxygen concentrations. Both stormwater runoff and septic system discharges are thought to be some o f the primary sources for these pollutants (i.e coliforms and nutrients), which are contributing to low dissolved oxygen concentrations within adjacent receiving waters. The North Bay area associated with the City of Allyn has been monitored by the Washington Department of Health (WDOH) for the past ten years (Figure 4-4) Data from the 2006 collection period indicates that several of the monitoring areas have been downgraded to a "threatened" status (stations #1, #7, and #575) or listed as areas "of concern" (stations #11, #12, and #548) due to water quality contamination associated with elevated fecal coliform bacterial levels. WDOH is currently investigating sources of contamination for North Bay. Stormwater runoff, currently untreated in the Allyn area, likely provides much of the non - point source pollution to marine nearshore areas (Kim Zabel, pers. comm.). Shellfish North Bay is considered a shellfish protection area by the WDOH, and it is also on the Washington State Department of Ecology's (DOE) 303(d) list for fecal coliform bacteria contamination Additionally, the WDOH has prohibited shellfish harvesting along beaches immediately adjacent to Allyn to the southeast because of pollution concernst, and numerous o ther locations are either threatened or of concern due to elevated bacteria levels (see above). Areas designated as threatened or of concern by WDOH are based on assessments o f threats to shellfish growing areas, and in the case of North Bay, these threats are based on bacterial sampling levels and standards established by the National Shellfish Sanitation Program (NSSP). Pickering Passage is located lust to the south of North Bay, and marine water from Pickering Passage mixes with water in North Bay thus, water quality conditions in Pickering Passage are directly related to water quality in North Bay. The WDOH summary shows that all water quality monitoring stations in the approved portion of the shellfish growing area in Pickering Passage (with the exception of station #57) pass the NSSP water quality standard(Figure 4- 5). Sampling station 457 fails the NSSP "approved" water quality standard, and the WDOH report also indicates that stations 7'52 and I/58 are "threatened" and station #66 is "of concern due to elevated bacteria levels. Because the Pickering Passage area fails to meet the shellfish classification standards, WDOH recommends that a comprehensive evaluation be conducted to determine the appropriate classification for the area. Furthermore, WDOH recommends that a pollution Mason County Stormwater Management Plan 8 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued source investigation should be initiated to identify and determine the source(s) of contamination to Pickering Passage. Salmonid Habitat: Stream and Marine Nearshore Stream Habitat: Salmonid habitat in the North Bay area consists of nearshore habitat in the bay as well as the stream habitat associated with Sherwood Creek, Anderson Creek, and Lake Anderson. Sherwood Creek flows from Mason Lake into Case Inlet in the Puget Sound, and Anderson Creek confluences with Sherwood Creek to the southof Allyn The Washington Department of Fish and Wildlife identify Sherwood and Anderson Creeks as salmon -bearing streams, with several different species utilizing or potentially utilizing the in -stream habitat. Fall Chinook are documented as occurring in the lower portion of Sherwood Creek, and spawning habitat for coho salmon exists throughout the Sherwood and Anderson systems, with a documented presence of coho in several tributaries to both creeks. Spawning habitat for summer and fall chum exists in the Sherwood and Anderson Creek, and presence of fall and summer chum is either documented or presence is presumed in both creeks Winter steelhead are documented as occurring in the mainstem Sherwood Creek, and spawning habitat for this species is found in the Anderson Creek system. The outlet from Lake Anderson provides rearing habitat for both coho and winter steelhead. Marine Nearshore Habitat: Nearshore habitat associated with the Allyn UGA occurs along the western shoreline of North Bay. The nearshore habitat provides critical rearing and estuarine habitat for a variety of different species, in particular the salmonid species. Juvenile salmonids use nearshore habitats for several key life history functions. These habitats provide migration corridors, food production, and refuge from both predators and high- energy water waves (Mason 1970 Mac Donald et al. 1987; Thorpe 1994; Aitkin 1998). In addition, all salmonid juveniles utilize estuarine and nearshore environments to move from their natal stream out into the ocean (Williams and Thom 2001). This is a physiologically complex transition and the estuarine environment provides a gradual transition for juveniles to adjust (Simenstad et al. 1982). The nearshore environment also contains marine vegetation associated with estuarine and nearshore marshes which provides shelter to rearing fish by protect juvenile salmon from turbulent wave action (Aitkin 1998). Nearshore habitat associated within North Bay and Case Inlet contains habitat associated with documented forage fish presence, eel grass beds, mudflats, and salt water marshes, and intact portions of the nearshore riparian zone. A high value estuary occurs at the mouth of Sherwood Creek. Salmonid species known to utilize this nearshore habitat include Chinook, coho, chum, sea -run cutthroat, steelhead, sockeye, and bull trout. Issues of concern in the Mason County Stormzvater Management Plan 9 otak H:\project\30700\30784\Reports\Addendum\Appendix A doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued nearshore habitat associated with North Bay include water quality (fecal coliform, low DO, nitrogen loading, etc.), shoreline armoring, loss of nearshore riparian vegetation, and issues associated with stormwater and wastewater discharge. City of Belfair and South Hood Canal Water Quality Many of the marine water quality concerns described for the City of Allyn also pertain to the City of Belfair. The area of Hood Canal associated with Belfair is currently listed as prohibited for shellfish harvesting by WDOH due to poor water quality. The Mason County Department of Health Services is currently working with WDOH to increase sampling in the Belfair area, as well as to identify bacterial pollution sources within this area. In addition to the concerns in Hood Canal, water quality in the Union River is a concern. The Union River basin is located in a largely rural setting with few prominent urban areas or major point sources of pollution. Belfair, located near the mouth of the Union River, is the largest urban area in the basin (Figure 4-6). Increasing amounts of impervious surface in developed areas in and around Belfair may be decreasing groundwater recharge, increasing erosive storm flows, and directly delivering pollutants to the Union River. Recent storm sampling of streams draining the Belfair urban area show high bacteria concentrations in runoff (Ecology, 2003), and there is currently a TMDL and a water cleanup plan for the Union River for fecal coliform bacteria Studies conducted as part of the TMDL indicate that dry season bacterial concentrations in the Union River are higher than those in the wet season, suggesting that there is a continuous, steady component to the pollution loading in the Union River. Since concentrations are relatively high during the wet season and flows are dramatically higher, there is also a storm -related component to the pollution loading. Pollution sources in the basin are exclusively non -point, and predominant sources are likely agriculture, onsite disposal (septic) systems, and post -development activities attributable to urban development (e.g., domesticated animals). Shellfish A portion of the Hood Canal /19 monitoring area is located adjacent to the City of Belfair (Figure 4-7), and the portion of this monitoring area impacted by Belfair is listed as prohibited for shellfish harvest. Pollution source identification and correction work is on- going in the area. Fiftv-five acres of Belfair State Park tidelands were upgraded from Prohibited to Approved in 2006. However, extreme rainfall and storm water runoff resulted in emergency closures of the area from 1 /30/2006 to 2/4/2006 and from 11 /7/2006 to Mason County Stormwater Management Plan 10 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued 11 /14/2006 The area was closed from 8/2/2006 to 9/28/2006 due to a naturally occurring marine pathogen All stations in the "approved" portion of Hood Canal #9 meet the NSSP standard for an "approved" classification. The WDOH continues to assist Mason County in their pollution source identification work in the City of Belfair. Stimson and Little Mission Creeks and portions of the marine waters in Hood Canal #9 are currently on the 303(d) list for fecal coliform bacteria contamination. Salmonid Habitat: Stream and Marine Nearshore Stream Habitat: Salmonid habitat associated with Belfair UGA consists of nearshore habitat in the Hood Canal and stream habitat associated with Union River and its tributaries. Union River flows from Mason Lake into Case Inlet in the Puget Sound. The Washington Department of Fish and Wildlife identify Union River as a salmon -bearing stream, with several different species utilizing or potentially utilizing the in -stream habitat Fall Chinook are documented as occurring in the Union River, and spawning habitat for Chinook exists in much of the system, with rearing habitat for the species occurring in the lower Union system. Spawning and rearing habitat for coho exist in the system, and summer and fall chum are documented as occurring in tributaries to the Union River. Spawning and rearing habitat for winter run steelhead occur in the Union River, and there is a documented presence of winter steelhead through much of the system Pink salmon are also documented as occurring in the Union River system. Nearshore Habitat: Similar to the nearshore habitat around Allyn, the nearshore habitat in the vicinity of the Belfair UGA has many of the same habitat features and functions. Saltwater marshes, tidal mudflats, and nearshore riparian habitat all occur in the Belfair area and all provide similar habitat functions and value to salmonids as noted above. Suggestions for Resource Management Management approaches that focus on preserving healthy ecological processes require a thoughtful and planned set of strategies to assess conditions, track changes incorporate new information, and redirect efforts over time to keep the system in balance. Here are a few suggested activities from the literature to help protect and restore watersheds and sensitive habitat areas within the Puget Sound basin. Mason County Stormwater Management Plan 11 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued Stormwater Management / Watersheds Booth et al. (2002) offered the following suggestions to minimize the impacts of stormwater: • Cluster developments that protect half or more of the forest cover, preferentially in headwater areas and around streams and wetlands to maintain intact buffers, • Allow a maximum of 20 percent total impervious area, and substantially less effective impervious area through widespread reinfiltration of stormwater, • Provide onsite detention that is realistically designed to control flow durations (not just control peak flows), • Protect riparian buffer and wetland protection zones to minimize road and utility crossings as well s overall clearing, and • Do not allow any construction on steep or unstable slopes. Habitat The following is a summary from the Salmonid Habitat Limiting Factors Water Resource Inventory Areas 15 (West), Kitsap Basin and 14 (North), Kennedy-Goldsborough Basin http.//salmon.scc.wa.gov/reports/wrial4andl5.pcif . Two sets of recommendations are presented for two different types of salmonid/fish habitat areas freshwater Stream/riverine and saltwater marine nearshore. Freshwater: Stream/Riverine The Technical Advisory Group for WRIA 1 makes the following recommendations to protect existing habitat and minimize further degradation of riverine habitat conditions: • Protect watershed conditions by preventing sprawling rural residential development. H ncourage private forestland owners to continue timber production in a sustainable fashion that protects natural watershed functions (i.e. natural sediment production rates, natural runoff and stream flow regimes, mature riparian forests with coniferous trees, adequate large woody debris and pool abundance) • Protect functional riparian forest buffers to provide shade to maintain cool summer stream temperatures, provide large woody debris necessary to maintain instream salmonid habitat, and filter soil and pollutants from runoff. Where feasible, replant native riparian vegetation at degraded sites. • Protect functional floodplain habitat and where practical, restore lost floodplain habitat. Prevent further floodplain development Decommissioning of an old forest road and construction of a new access road on the lower portion of Anderson Creek is one example of a potential floodplain restoration project. Mason County Stormwater Management Plan 12 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc Appendix A — Water Quality, Fish, Shellfish and Habitat Report Continued • Protect the shorelines of lakes, ponds and wetlands that maintain summer stream flows and provide rearing habitat for juvenile salmonids Where practical, restore degraded shorelines. • Maintain cool summer water temperatures and fish passage by preventing conversion of wetlands to shallow man-made lakes (for example Lake Symington and Lake Tahuya). • Remove fish passage barriers. • Minimize installation of impervious surfaces such as rooftops, roads, driveways, and lawns. Educate the public about the importance of minimizing impervious surfaces. • Monitor instream flows and water quality parameters including temperature and dissolved oxygen levels throughout west WRIA 15 and north WRIA 14. • Assess salmonid habitat conditions in the watersheds of the numerous small independent streams in the report area, particularly streams in the Port Gamble Subbasin and streams draining to the north shore (Tahuya-Dewatto and Union -Mission Subbasins) and south shore (North WRIA 14) of the east arm of Hood Canal. Marine: Nearshore Habitats The following recommendations are provided to address similar habitat concerns associated with marine nearshore habitat areas* • Evaluate all road crossings along the Hood Canal shoreline to assess tidal function, sediment transport, and anadromous fish migration and where necessary, implement corrective actions to restore and/or enhance natural tidal processes, sediment transport, and anadromous fish access. • Allow eroding bluffs to function naturally to provide the sediment and large woody debris needed to maintain shoreline features such as beaches, spits, and lagoons, and shoreline habitat complexity. • Where practical, remove intertidal fill to restore/improve natural tidal and sediment transport processes. • Where practical, remove shoreline armoring or replace armor with alternatives including large woody debris and riparian plantings. • Prevent installation of intertidal fill and shoreline armoring, prevent removal of native riparian vegetation, and encourage landowners to install community boat ramps, docks, and piers rather than installing structures at each individual property. • Reduce impervious surfaces and impervious surfaces to reduce the impacts of high winter infiltration of precipitation. Mason County Stormwater Management Plan 13 otak H:\project\30700\30784\Reports\Addendum\Appendix A.doc /`Skokomish- Dosewallips (WRIA 1.6) r • • • • • • • BELFAIR URBAN GROWTH AREA hood% , Station., ALLYN URBAN GROWTH AREA • • • Legend • TMDL Areas ratiir s' River Threatened Shellfish Growing Areas Within Mason County Streams Streets —I-- Railroad y..•.• WRIA Boundary County Boundary UGA Boundary Figure 4-1 Mason County Wria Map W 0 N s 2 4 Miles 411NOAh5th, PO Box279 Stiellon, Washngton 98584 Phone (360) 427-9670 Fa( ' (360)427-8425 10230 NE Pools Drive, Suite 400 Ni'iland, Washington 98033 Phone: (425) 822-4446 Fay: (425)827-9577 K:/project/30700/30784/GIS/mxds/Figure4_1 MasonWRlAMap.mxd 2007 Threatened Shellfish Areas : SHealth Growing 4 6 3 1tl 12- 1 2 7 & 13 14 l �13 a Sami.sh So€till t North Burley Oakland Pickering Filucy bid (:nays Bay Naselk Naltcotta eats 11nas yes iclie Center Mats Inlet Skagit Bay Bay 13ay Harbor Bay Lag( t Bay Passage I3a} Bay - y r - '. - _ -- l.+ � Threatened Highways Counties Shoreline �; t 0 , x Federal • pubum i �q„ s Ftedm Berlevus r�$ kTd« ,n Legend ; ; - wattle Way s 7 rsfix. r...ti.ay F ?i /J i [I 2f. VG L b )t %t 04 4( sf T b'41 r!torri..ry r , , y e1J MI? i-'4 tn3P YG 81 .� _ „w; s:R s , �",'% .,. — - C mpia 411 "a. � Areas 404000) :a Mlles _ {, Growtn€g (Pop 10 Cities $ Named a— as 20 4-2 Shellfish 0 1,500 3,000 Feet North Shelton, Phone: Fax: Box279 98584 10230 Kirkland, Phone: Fax: a Drive, Suite 400 98033 822-4446 827-9577 0 NE Poirts Washogton (425) (425) Figure 2007 Areas411 Threatened © SIh. P.O. Washington (360) 427-9670 (360)427-8425 K:/project/30700/30784/G I S/mxds/Addendum/Fig ure4_2. mxd -- Kennedy- Goldsborough (WRIA 14) Drainage Bas'n Divide Drainage Subbasin Streams ---- Streets- - ( ) Railroad Parcel Boundary 1'! Allyn UGA ALLYN URBAN GROWTH AREA Anderson Creek Sherwood Kitsap (WRIA 15) (id ------- WEST DRAINAGE BASIN i fir_ ., EAST+DRAIN A( Lake - BASIN Anderson. 0 0 0 0 0 t- Source: GIS data and Aerial photography provided by Mason County 2006. Washington State Department of Natural Resources provided Mason County with the stream data used in this report . Disclaimer: This map is not to survey accuracy and is meant for planning purposes only. Figure 4-3 Allyn Surface Drainages 0 1,500 3,000 Feet 411 Norlh 51h, P.0_ Box279 Sheltm, Washngton 98584 Phone. (360) 427-9670 Far: (3E0)427-8425 10230 NE Poirts Drive, Sete 400 Kirkland, Washington 98033 Phone: (425) 822-4446 Fax: (425) 827-9577 K:/project/30700/30784/GIS/mxds/Addendum/Figure4_3.mxd TAT1ON LOCATIONS AND CLASSIFICATION SOLJNDARI Figure 4-4 North Bay Shellfish Sampling Areas 0 1,500 3,000 Feet 411 North 5(h, P.O. Box 279 Slie un,Washinglon 98584 Phone: (360)427-9670 Fax: (360) 427-8425 10230 NE Poirts Brrve, Sue 4W Kirkland, WasNngton 98033 Phow: (425) 622-4446 Fax: (425)827.9577 K:/p roj ect/30700/30784/G I S/m xd s/Addendum/F ig u re4_4. mxd Figure 4-5 Pickering Passage Shellfish Sampling Areas 0 1,500 3,000 Feet 411 North 5th, P.O. Box 279 Shelton, Washington 98584 Phone: (360) 427-9670 Fax. (360)427-8425 10230 NE Pail -is Drive, Suite 400 Kirland, Washington 98033 Phone: (425) 822-4446 Fax (425) 827-9577 K:/p ro;ect/30700/30784/G I S/mxds/Addend um/F igure4_5. mxd Legend simen Drainage Basin Divide Drainage Subbasin_ Streams Streets �-� Railroad Parcel Boundary Belfair UGA Waterbody Cf1"Son a5c° 7 o0 'J -so Kennedy- Goldsborough (Wf RIA 14)' BELFAIR URBAN GROWTH AREA Union River kib1a Cre�e�k lributa Cat Source: GIS data and Aerial photography provided by Mason County 2006. Washington State Department of Natural Resources provided Mason County with the stream data used in this report Disclaimer: This map is not to survey accuracy and is meant for planning purposes only. Figure 4-6 Belfair Surface Drainages 0 1,500 3,000 Feet 411 North 5th, P.O. Box 279 Shehon, WasN.nglon 98584 Plane: (360) 427-9670 Fax: (360) 427-8425 10230 NE Poinls Drive, Sue 400 Kiland, Washington 98033 Phone: (425) 822-4446 Fax: (425) 827-9577 K:/protect/30700/30784/GIS/mxds/Addendum/Figure4_6.mxd Figure 4-7 Hood Canal Station #9 Shellfish Samphng Areas 0 1,500 3,000 Feet 411 North5lh, P 0 Box 279 Shelton, Washngton 98684 PhDra (360) 427-9670 Fax (350) 427-8425 10230 NE Poirls Dnve, Su%400 )(Alan], Washngton 98033 Phone (425) 822-4446 Far (425) 827.95/7 K:/pro/ect/30700/30784/G IS/mxds/Addend um/Figure4_7. mxd Transmittal Mason County Update of County's Stormwater Policies/Regulations and Development of Comprehensive Stormwater Management Plans. Allyn Urban Growth Area Stormwater Management Plan Submitted to: Mason County Department of Public Works 411 N. Fifth Street Shelton, WA 98584 Prepared By Otak, Inc. Joe Simmler, Ph D Project Manager Larry Grimm, PE Project Engineer Laura Becker, EIT Engineering Designer Preface Allyn Urban Growth Area Stormwater Management Plan This document, entitled Allyn Urban Growth Area Stormwater Management Plan, has been prepared by Mason Count) in response to a request from the Western Washington Growth Management Hearings Board to enhance and provide additional information as to the need, cost, funding, and schedule for implementation of storm\eater management infrastructure improvements over the next six years within the Allyn Urban Growth Area of Mason County, as described in the County's 2005 Comprehensive Land Use Plan. The final Allyn UGA Stormwater Management Plan document will go through extensive local public review, consisting of public meeting(s), a public hearing, and review and approval by the County Board of Commissioners prior to its submittal to the State Boundary Review Board on August 6, 2007. Public comments will be addressed and incorporated into this Plan, as appropriate. This is the initial draft of that document. This project has been funded entirely by Mason County. Mason County Allyn UGA Stormneater Management Plait otak K:\project\30700\30784\Reports\Allyn S\vi\dP Update \Final Report\Allyn SWAT Report.doc Table of Contents Allyn Urban Growth Area—Stormwater Management Plan Acknowledgements Executive Summary Section I —Introduction I Section 2—Characterization of the Allyn UGA 15 Section 3—Existing Stormwater Facilities 23 Section 4—Future Conditions 29 Section 5—Regulatory Design Criteria 32 Section 6—Hydrologic Modeling and Engineering 38 Section 7—Stormwater Management Plan 57 Section 8 Costs, Schedule, and Implementation 65 Tables Table E-I—Allyn SWM Plan: Short -Term Project Costs for Six Year CIP Plan Short - Term CIP 5 Table E-2—Allyn SWM Plan: Long -Term Stormwater Project Costs for Ultimate Development 5 Table E-3—Financial Plan for the Allyn Stormwater Management Plan Annualized Revenue Needs Over the Twenty Year Planning Period 8 Table E-4—Long Term CIP Cost Impact Analysis Results I 0 Table 4 I —Future Land Use Cover Assumptions 29 Table 5 I —Regulatory Requirements 32 Table 6 I —Future Subbasin Groupings 42 Table 6-2 Density vs Water Quality and Detention Volumes 45 Table 6-3 East Uplands: Water Quality Treatment & Outfall Requirements 5 I Table 6-4—Sherwood Creek Basin Results 54 Table 6-5—Shoreline WQ Requirements 55 Table 7-I—Short-Term CIP Costs (Six Year CIP Plan) 60 Table 7-2—Long-Term CIP Costs (Twenty Year Buildout) 62 Table 8- 1 Financial Plan 65 Mason Cazrnty Allyn UGA Stormwater Management Plan TOC-i otak K:\project\30700\30784\Reports\Allyn SW\{P Update \Final Report\Allyn SWM Report.doc Table of Contents Allyn Urban Growth Area Stormwater Management Plan Table 8-2—Long Term CIP — Cost Impact Analysis 68 Table 8-3—Long Term CIP - Cost Impact Analysis 72 Figures Figure E I —Study Area 2 Figure E-2—Location of CIP Projects 6 Figure I -1—Location Maps 13 Figure 2 I —Existing Drainage Basin Boundaries I Figure 2 2—Site Soils I9 Figure 2-3—Critical Areas 21 Figure 2-4—Land Use 22 Figure 3 I—LakeLand Village Map 24 Figure 3 2 Existing Conditions 27 Figure 4-I—UGA Zoning 30 Figure 4 2 Zoning Constraints Revisions 3 I Figure 6 I —Modeling: Existing Subbasin Boundaries 40 Figure 6 2—Modeling. Future Subbasin Boundaries 41 Figure 6-3—LakeLand Village Density vs WQ and Detention Volumes 44 Figure 6-4—Stormwater Management Areas 46 Figure 6-5 Proposed Stormwater Facilities: Long Term Six Year CIPS 50 Appendices Appendix A LakeLand Village Stormwater Facility Information Appendix B Low Impact Development Techniques Appendix C—Hydrologic Analysis Appendix D—Hydraulic Analysis Appendix E--Construction Cost Estimates Appendix F—Su,ested Scope for Culvert/Outfall Inventory and Analysis Mason County Allyn UG.A Storzn aler Management Plan TOC-ii otak K:\project\30700\30784\Reports\Alllnt S\C-SIP Update \bind Report \Allyn SWM Report.doc Table of Contents Allyn Urban Growth Area Stormwater Management Plan Appendix G—Preliminary Analysis of Existing Culvert Analysis Mason Cortnty—Allyn UGA Slel-mmater• Management Plan TOC otak K:\project\30700\30784\Report,\All yn S\-i\IP Update Final Repo Al S\\2t.I Report.doc Acknowledgements Mason County Update of County's Stormwater Policies/Regulations and Development of Comprehensive Stormwater Management Plans Allyn Urban Growth Area Stormwater Management Plan Mason County Board of Commissioners Lynda Ring Fnckson—District 1 Tim Sheldon District 2 Jayni Kamin District 3 Mason County Department of Public Works Charlie Butros, Ph, Director Mason County Department of Community Development Emmett Dolby, Director Mason County Department of Health Services Debbie Riley, RS, Environmental Health Manager Mason County —Allyn UGA Stormwater Management Plan otak I<:\project\30700\30784\Reports\Allyn SWMP Update \Final Report \Allyn SV(%1 Report.doc Executive Summary Allyn Urban Growth Area Stormwater Management Plan Future Growth VVithin the Allyn UGA The Allyn Urban Growth Area (UGA) is expected to continue to grow at a moderate rate over the next several years. While there may be some new commercial and new redevelopment, most of the new development is expected to be residential. .According to the County, about 60 percent (30 homes) of the 50 new homes per year will be locating within the LakeLand Village Development, and the remaining 40 percent (20 homes) will be generally located within the drainage basins on either side of LakeLand Village Drive Photo 1 Existing Drainage System North Bay For the purpose of this engineering analysis and estimate of future drainage infrastructure needs, the Allyn UGA was divided into two major stormwater management areas, as shown i i Figure E-1. The West Drainage Basin includes the LakeLand Village Development and drains into Sherwood Creek and Devereaux Lake. The East Drainage Basin includes those drainages that flow to the cast and discharge directly into North Bay (Case Inlet of Puget Sound). Mason Coataly llyn UGA Sin rmwater Management Plan 1 otak IC: \project\30700\3078-4\Reports\_lll}n S\ MI? Update \Final Report\Allyn S\V\I Report.c'loc Legend ..®.w Drainage Basin Divide Drainage Subbasin Streams - Streets Railroad Parcel Boundary Allyn UGA £y►_ + EAST DRAINAGE Lake BASIN Anderson. z ; 1 CO Figure F-1 Study Area Allyn Stormvater anagement. Plan 0 1,500 3,000 Feet 411 l:_rthit PO. I4,44 2?a W. strion 5463: Wine: r441-27-$10 Fax (844}tflt425 10[11 t.E V;ay.. Ori-n,S4;t 4&J KN3r J.'Waste:ptrn s5033 F44440.: (4258224443 Fa 4:2i) ®n 5n Kiproject/30700/30784/G IS/mxds/Figures/StudyArea. mxd Executive Summary Allyn Urban Growth Area Stormwater Management Plan The drainage system within the East Drainage Basin of the UGA is composed primarily of ditches within road rights -of -way and a series of culverts which convey runoff under State Route #3 (SR3) directly into North Bay. The drainage within the West Drainage Basin is contained almost entirely within the LakeLand Village Developmen.t. Almost all drainage from the LakeLand Village Development drains into Lake Anderson, a man-made regional amenity that performs regional detention prior to discharge into Anderson Creek, a tributary of Sherwood Creek, which ultimately discharges into North Bay. A small northwest portion (about 80 acres) of the LakeLand Village Development discharges primarily as shallow interstitial groundwater into Devereaux Lake. There are few existing drainage problems within the Allyn UGA. Within th.e East Drainage Basin, the drainage at the end of East Wade Street occasionally forms a localized pond during larger storm events, prior to entering a culvert under SR3 and discharging into North Bay. There are no major drainage problems within the LakeLand Village Development, located within the West Drainage Basin. At the present time, the County is primarily responsible for drainage infrastructure planning and construction within the East Drainage Basin and the LakeLand Village Development Corporation is primarily responsible for stormwater management and facilities within the West Drainage Basin. The County, however, is responsible for maintenance and repair/replacement of all drainage systems within the County road rights -of -way, which include the roads within LakeLand Village. Photo 2 Anderson Lake 'son CountyLIGA Stormwater Management Plan 3 otak K:Aproject \30700\30784\Reports \Allyn S\V? [P Update \I final Report Allyn SWNI Report.doc Executive Summary Allyn Urban Growth Area Stormwater Management Plan Allyn UGA Stormwater Management Plan The drainage infrastructure needed to support development within the Allyn UGA, as well as ultimate buildout, has been identified and proposed for implementation in the following Allyn UGA Stormwater Management Plan. Costs and priorities for implementation have been identified for both the short-term (six year planning period) as well as future ultimate development over the next twenty years. Short -Term Infrastructure Needs Due to a continued moderate rate of growth, with most development being residential and locating within the LakeLand Village Development (i.e. the West Drainage Basin), and due to the capacity that likely remains within the existing drainage system, no capital projects have been proposed «ithin the West Diainage Basin of the Allyn UGA over the next six years. An analysis of the runoff generated by the 120 new homes projected to be located within the East Drainage Basin (on either side of LakeLand Village Drive) over the next six years shows that new development will require only about ten percent of the existing capacity of the culverts under SR3 that discharge into North Bay. Assuming these culverts are not at capacity and are not blocked, as evidenced by the lack of existing flooding, there should be enough capacity remaining in the existing drainage system to collect and convey this new incremental increase in stormwater runoff under SR3 and into North Bay over the next six years. LakeLand Village Development Corporation will continue to design, construct and fund any new drainage facilities needed within the West Drainage Basin. The County will continue to provide maintenance, including repair and replacement, of those existing and new drainage facilities located within the Count) road rights -of -way. Thus, the recommended Stormwater Management Plan for the next six years primarily addresses the East Drainage Basin and includes a series of activities, including maintenance, in order of their respective priorities and costs, as shown in Table E-1 Drainage infrastructure costs over the next six years total $660,000 and averages $110,000 per year. Implementing this capital facilities plan within the East Basin is primarily the County's responsibility. Mason County Allyn UGA Stormwater Management Plan 4 otak K:\project\30700\3078 +\Reports\.Allyn S\VIP Update\Final Report\Allyn SWAT Report.doc Executive Summary Allyn Urban Growth Area Stormwater Management Plan Table E- I —Allyn SWM Plan: Short -Term Project Costs for Six Year CIP Plan Schedule (Year #) Yr Annual 1-2 Cost Yr 3-6 ($) Total Activity # Project/Activity Priority 1 Use existing Co. staff. Activity #1: Coordination WSDOT High with 1-2 $30,000 $30,000 $60,000 Activity #2: Inventory Capacity Analysis high and Annually$50,000 $50,000 $300,000 #3: Culvert Maintenance High .Activity Annually $50,000 $50,000 $300,000 Activity #4: Property Acquisition High Begin Yr.1Use existing Counter staff Activity #5: Secure Funding (Ongoing rocess) high 1 Use existing County staff #6: Activity Low Impact Development Brochure High Total $130,000 $130,000 $660,000 Long -Term Infrastructure Needs for Ultimate Buildout East Drainage Basin Ultimate development within the East Drainage Basin of the Allyn UGA is likely to take place over the next twenty or more years, and will require major regional stormwater capital improvements consisting of enhanced collection and conveyance, four new outfalls to North Bay, and regional water quality treatment within the East Drainage Basin. These facilities include the capital projects presented in Table E-2, listed in relative order of priority and cost. Total costs to support ultimate development within the Allyn UGA are estimated to be $15M. Proposed capital projects are shown in Figure E-2 Table E 2—Allyn SWM Plano Long Stormwater Project -Term Costs for Ultimate Development Project Estimated Cost ($) 980,000 CIP .#1A: East Evans Street Conveyance System 3,040,000 CIP #1B: h Street Conveyance ast Wade System 4,460,000 CIP #2• Evans Street Conveyance, Outfall & WQ Pond(s)* 2,780,000 CIP #3: Wade Conveyance, Outfall & WQ Ponds*) 700,000 CIP #4: Kayak Park Conveyance, Outfall & WQ Pond(s)* 3,170,000 CIP #5: Power Easement Conveyance, Outfall &WQ Pond(s)* Total $15,130,000 Does not include the cost of land and easement acquisition. Mason County UGA Storinn'ater Management Plan 5 K:\project\30700\3078 4\Reports\Allyn SAC%\dP Update \Final Report\_lllyn SWM Repoct.doc otak I Li 1.. OO CO ca 51) Executive Summary Allyn Urban Growth Area Stormwater Management Plan West Drainage Basin Within the West Drainage Basin, the LakeLand Village Development is planning to construct the final phase of development in the northwest corner of the site. This will complete the development of the West Drainage Basin of the Allyn UGA. The needed drainage facilities and their costs are the responsibility of the LakeLand Village Development Corporation. In the future, the County will still be responsible for the maintenance of the drainage facilities within the County road rights -of -way. Thus, the County is not planning any new capital drainage projects within the West Drainage basin, since these will continue to be designed and constructed on an as -needed basis by the LakeLand Village Development Corporation. Photo 3 Sherwood Creek Costs and Implementation It is likely that the biggest challenge facing the County in the development and implementation of the Allyn Stormwater Management Plan will be the development of the needed revenue within the required timeframe. <llason Conlily r'{llyn VGA Storut/uaicr Mana,gement. Plan 7 otak I<:Aproject\30700\30784\Repo rts\Allyn SWMP Update \Final Report \rlllpn SWI\I Repoctdoc Executive Summary Allyn Urban Growth Area Stormwater Management Plan Costs: Funding and Timing Implementation Priorities and Schedule Determine Revenue Needs Although difficult to predict, an attempt has been made to identify the priority and timing of future activities and capital projects in order that future revenue needs can be established. Presented in Table E-3 is an estimate of how much new revenue will be needed over what period of time. For this analysis, the twenty year planning period has been divided into four planning periods of 6, 4, 5, and 5 years respectively, as shown below. Total costs over the twenty year capital planning period are estimated to be $15M, with $3.83M deferred beyond this period as described in the note to Table E-3 Average annual costs for each of the four planning periods are $110,000, $1,005,000, $892,000, and $556,000, respectively. The next six years will requii e the least, $110,000 per year. Years 7 through 15 will require approximately $1M per year. And with the deferral of CIP projects #4 and #5 out beyond the twenty year planning process, the annual cost fot years 16-20 is about $552,000. Table E-3 Financial Plan for the Allyn Stormwater Management Plan Annualized Revenue Needs Over Twenty Year Planning Period the Cost ($ in I ,000s) Schedule (yrs/$ I 000s) Relative Priority for Implementation I -6 7-10 11-15 16-20 Short -Term Activities: $660 $660 Long-term Activities: $980 $980 + CIP #1A0 E Evans Collection + CIP #1B• E Wade Collection $3,040 $3,040 + CIP #24 Evans St Culvert/Outfall $4,460 $4,460 $2,780 $2,780 + CIP #3: Wade St Culvert/Outfall $700 + CIP #4: Kayak Pk Culvert/Outfall* $3,170 + CIP #5: Power Ea Culvert/Outfall Total: $15,130 $660 $4,020 $4,460 $2,780 $110 $1,005 $ 892 $556 Annual Estimate: * It is d fficult to estunate when ultimate buildout will occur. The most northern and southern ends of the Allyn UGA within the Fast Drainage Basin will likely be the last to be. developed. As a result, from a financial planning perspecti\ e, the funding fot these r o cul\ ert/outfall projects has been postponed until after the twenty year capital planning period. Thus, projects CIP /14 and #5 have been deferred beyond the 20 year planning period. Mason County Allyn UGA Siormwater Management Plan 8 otak K:\project\30700\30784\Reports\Allyn S\VtvIP Update \Final Report\Allyn S\\'\.I Report.doc Executive Summary Allyn Urban Growth Area Stormwater Management Plan Potential Sources of Funding At this point in time, the. County has not yet determined how they will raise the funds needed to support and implement this proposed stormwater management plan for the Allyn UGA. There are several financial options being considered These considerations have led to the conclusion that multiple sources of funding will be needed. Funding sources that are currently being considered include: • Formation of a Local .Drainage/Stormwater Improvernerat District; which would have an annual assessment often based on assessed property value, or some other equitable means of establishing value and/or benefit to the various rate payers. • Real Mutate Excise Tax (REE7) funding, which currently amounts to about $1M per year, and is currently being used to pay for a number of capital projects throughout the County. • Public Sector Funding, such as grants and low interest loans from the State (Ecology or the Puget Sound Action Team) or federal government, including federal 319 Water Quality Grants, and the State Public Works Trust Fund and State Revolving Fund. • Formation of a Stormwater Utility (County -wade, where a monthly service fee is assessed to rate payers, often based on the amount of impervious area per parcel, and an incremental portion could be allocated back to the rate payers within the Allyn UGA. • System Development Charges, where any person moving into an upstream drainage area would be required to pas for a portion of the downstream collection, conveyance, detention, treatment, and outfall facilities that may be needed to support continued development within the drainage basin. • SEPA Mitigation Funds, which would be established on a per development basis, as a project enters and is ultimately approved through the State SEPA review process. • Partnering with prospective developers and land owners, which is especially effective in establishing funding for larger regional drainage facilities. • Other potential, but less likely sources of funding, include: - The County General Fund - The County Road Fund - Cost Sharing with IVSDOT • ATI potential f tture road, park, or tail/ y project could also include some funding for making localized drainage improvements, as defined in advance though this stormwater planning process. From this list of eleven potential sources of funding, the most likely sources of new future funding in relative order of priority are: 1. Partnering with developers. 2. S Ft PA mitigation funding. 3. Periodic appropriations from RF KT funding. Mason County—Alljiaa UGA Stormwater Management Plan 9 otak K:\project\30700\30784\Reports\Allyn S\\ 1IP update\Final Report\_lllyn S\V'\vI Report.doc Executive Summary Allyn Urban Growth Area Stormwater Management Plan 3. Periodic appropriations from REET funding. 4. Public sector funding (grants and loans). 5. Annual CIP stipends from a county -wide stoiunwater utility. 6. Partial, periodic funding from future road, park or utility projects. It is difficult to estimate how much revenue could be raised by each of these preferred potential funding sources, over what period of time in order to support the annualized Financial Plan. However, being primarily driven by future growth, it is recommended that every effort be made to optimize the amount of new revenue from prospective developers, and then augment the remaining funding needs from REST and public sector funding as opportunities allow. Future partnering with developers, land owners, WSDOT, and the Port of Allyn should assist the County in sharing these regional growth -related costs and maintaining the steady, continuous development of the drainage infrastructure needed to support growth throughout the Allyn UGA. Summary of Cost Impact Analysis Using a Cost Impact Analysis, the County is able to reduce its long-term CIP costs to $3.5M, or by77 percent as shown in Table E-4, with developers assuming the balance of the remaining $11.6M. E-4 Long CIP Cost Impact Analysis Results Table Term Conveyance Detention WQ Outfall Treatmt Total CIP $5,230,000 $-0- $8,670,000 $1,230,000 $15,130,000 Total Costs: Impact Analysis: Co. Reductions Cost $2,620,000 $-0- $8,670,000 $ 308,000 $11,598,000 Revised Costs: Co. $2,610,000 $-0- $-0- $ 922,000 $ 3,532,000 Costs Developer: to $2,620,000 Not Estimated $8,670,000 $ 308,000 $11,598,000 Mason County —Allyn UGA Stormwater Management Plan 10 otak K:\project\30700\30784\Reports\Allyn SWMP Update \Final Report \Allyn SWivf Report043007.doc Executive Summary Allyn Urban Growth Area Stormwater Management Plan Suggested Alternative Stormwater Management Plan & Funding Strategy Based on the above Cost Impact Analysis, the following Stormwater Management and Funding Strategy is suggested for consideration by the County and the citizens of the Allyn community. The Allyn UGA Stormwater Management Plan and funding strategy are composed of the following recommendations, including refinements to the proposed Long - Term CIP Plan for the Allyn UGA • Water quality treatment is provided on-site/regional by each new developer. • Detention is provided onsite by each new developer, where required. • County pays for 50 percent of the new regional collection and conveyance systems, with developers paying for the remaining 50 percent. • County pays for 75 percent of the new regional outfalls, with developers paying for 25 percent. Mason County Allyn UGA Stormwater Management Plan 11 otak K:\project\30700\30784\Reports\Allyn S\ViviP Update\Final Report\All}n S\Yivr Report043007.doc Section ! Introduction Purpose and Scope Presented in this report is the Stormwater Management Plan (SWMP) for the community of Allyn, Mason County, Washington. This plan has been prepared to support the stormwater element of the 2006 Allyn Urban Growth Area (UGA) Comprehensive Plan. The Allyn UGA is located south of Belfair, adjacent to North Bay (Case Inlet) and east of Hood Canal, as shown on Figure 1-1. The Allyn UGA includes residential and commercial areas to the east, located within the Kast Drainage Basin, and the LakeLand Village community located to the west, which dominates the West Drainage Basin. The scope of this Stormwater Management Plan includes: 1. Characterization of existing stormwater conditions within the Allyn UGA. 2. An estimate of future conditions based on interim zoning set forth in the County's 2005 Comprehensive Plan. 3. Hydrologic/hydraulic modeling and engineering analyses to determine the number and size of facilities needed to accommodate existing and future growth. 4. Development and selection of stormwater management alternatives to meet existing and future development needs. 5. Presentation of the proposed Allyn stormwater capital improvement program (CIP), including proposed projects and activities, costs, priorities permitting, financing, and implementation considerations. The Allyn UGA Stormwater Management Plan responds to comments received by Mason Count) from the Western Washington Growth Management Hearings Board', which stated "the County must address the area -wide infrastructure needs for storm water management because of the increase in impervious surfaces inherent in a UGA."This Plan contains a stormwater capital facilities plan element that responds to that comment and is compliant with 36.70A.70)3, RCW 36.70A110.(3), and Goal 12 of the Growth Management .Act (GMA), CH. 36.70A. RWC. Authorization This study has been authorized by the Mason County Board of Commissioners and is being jointly initiated by the Departments of Public Works and Community Development. The Mason Count) Department of Health Services has also been invited to participate. The development of the Allyn UGA Stormwater .Management Plan has been entirely funded by Mason County. 1 Western \Washington Growth Management Hearings Board Final Decision and Order for Case N o. 06-2-2005, August 14, 2006. Mason County .Allyn UGA Stormier Management Plan 12 otak K:\ project \30700\3078d\Reports\Allyn SM. IP Update \Final Reporc\Allyn S\l'-\I Report.doc Flood Canal los Drainage Bas'n Divide Drainage Subbasin Streams Streets Railroad Parcel Boundary Allyn UGA ALLYN URBAN GROWTH AREA e Anderson Cree cc Devereaux Lake WEST DRAINAGE BASIN Lake Anderson. \.l co 0 Figure 1-1 Location Map Allyn Stouuwater Management Plan 0 1,500 3,000 Feet 4111.:rh5h P0_Ikn21h .am,W Iihibn5"s54 FYem 15'442T'S+7D Fax: ((ieo)421.6a25 P rrw.osia� Sybn 9i9ii (4211 P.22.4443 (32M fib 3577 K:/project/30700/30784/GIS/rnxds/Figures/LocationMapvER2 mxd Section I —Introduction Continued This study is part of a larger stormwater and regulatory compliance planning effort currently being undertaken by the County entitled* Update of County s Stormwater Policies/Regulations and Development of Comprehensive Stormwater Management Plan for Mason County and the communities of Allyn, .Befair;, and Hoodsport. This larger county -wide SWM planning program is expected to be completed by the end of 2007. Regulatory Requirements This stormwater management plan has been prepared to be consistent with the requirements set forth in the Ecology 2005 Stormwater Management Manual (SWMM) for the Western Washington and existing Mason County codes and regulations. These design criteria are also consistent with the 2000 Puget Sound Water Quality Management Plan and the 2005-2007 Update. Additional discussion of the design criteria used to develop the Allyn Stormwater Management Plan are presented in Section 5. Report Content and Organization The Allyn UGA Stormwater Management Plan is presented in discrete sections that generally follow the flow of work, culminating in the presentation of recommended capital projects and costs. The report is composed of the following eight sections: • Section 1—documents the goals and authorization for the study. • Section 2—characterizes the Allyn UGA study area. • Section 3 describes existing facilities and problems. • Section 4—analyzes future conditions needed to support ultimate development. • Section 5 outlines the regulatory mandated design criteria. • Section 6—conducts modeling and performs engineering analyses of needed facilities for existing and future/ultimate development. • Section 7presents the recommended SWM Plan for the Allyn UGA. • Section 8 lists priorities and presents costs and funding sources for implementation. Mason County Allyn UGA Stornezvater Management Plan 14 otak h:\project\30700\30784\Reports\Allyn S\VtIP Update \Final Report \Allyn S\XI I Repoct.doc Section 2—Characterization of the Allyn UGA bxisting conditions relating to stormwater management within the Allyn UGA are described in this section. Hydraulics/Hydrology and Topography The All) n Urban Growth Area includes two major drainage basins: the West Drainage Basin and the East Drainage Basins. These two major basins have been further subdivided into four drainage subbasins: Subbasin 1-Anderson Lake, Subbasin 2—Devereaux Lake in the West Basin, and Subbasin 3—North Bay, and Subbasin 4—Sherwood Creek in the Fast Basin. The location and boundaries of these basins are shown in Figure 2-1. For the purposes of this planning study, Subbasins 1 and 2 have been grouped together within the West Basin, and Subbasins 3 and 4 have been grouped together within and the East Basin. (Note that the subbasin boundary delineations shown in Figure 2-1 are based on GIS topography from the County, site visit observations, and information provided by the LakeLand Village.) Subbasin 1 Anderson Lake is the westerly basin that drains into Lake Anderson, Sherwood Creek, and ultimately North Bay. It contains most of the LakeLand Village Development. Subbasin 2—Devereaux Lake is the most northwesterly basin, and it includes a small portion of the drainage from LakeLand Village and drains into Devereaux Lake. Subbasin 3—North Bay is the most easterly basin and includes the area east of the Anderson Lake Basin and drains directly into North Bay (Case Inlet). Subbasin m1 Sherwood Creek includes the southernmost areas of the .Allyn UG.k which drains directly into Sherwood Creek. West Drainage Basin Subbasin I —Anderson Lake The Anderson Lake subbasin contains approximately 90 percent or more of the land area within the LakeLand Village development, and about 60 percent of the total land area within the .Allyn UGA. This is the most heavily developed ',primarily residential) subbasin within the Allyn UGA. The topographic ielief of this western basin consists of a shallow valley that drains from north to south and ultimately into Anderson Lake. The discharge of Anderson Lake is one of the tiibutaiies of Sherwood Creek. Anderson Lake is a man-made lake that was created about 20 years ago as part of the LakeLand Village Development. The majority of the LakeLand Development drains into this lake before discharging into Sherwood Creek, and ultimately into North Bay. Subbasin 2—Devereaux Lake In the most northwest area of the Anderson Lake Basin, is a small portion of the LakeLand Village Development (less than ten percent of the area of LakeLand Village) that drains into Aiason Co>rnlj'—Allyn UGA Stornmwater Management Plan 15 otak K:\project\30700\30784\Reports\.11lyn SWN[P Update\Final Report\_11len SR-1[ Report.doc I || m Section 2 Characterization of the Allyn UGA Continued Devereaux Lake. The topography in this small subbasin slopes downward to the north and drains toward Lake Devereaux. Runoff in this northwesterly basin reportedly reaches Devereaux Lake primarily as subsurface flow. This subbasin is largely undeveloped at this time, however, designs are currently being proposed by LakeLand Village for development in the near future. Photo Ai Anderson Lake East Drainage Basin Subbasin 3—North Bay The North Bay subbasin of the East Drainage Basin contains about 30 percent of the land area within the Allyn UGA. (It is made up of the East Uplands and Shoreline Stormwater Management areas, as will be discussed later in this report.) It is sparsely developed within its upper reaches, but is densely developed with a mix of commercial and residential along either side of SR3 and along the shoreline of North Bay. This subbasin contains a series of twelve small, relatively steep sloped drainages that discharge directly- into North Bay. In this easternmost basin, the existing roads and numerous culverts (eleven culverts) under SR3 define many of the subbasin boundaries, as shown in Figure 2-1. There are also another two culverts under SR3 and three culverts under North Bay Road in the north end of the UGA. Mason County Allyn VGA Stornrwaier <1lanagement Plan 17 otak K:Aproject\30700\3078d\RTorts \_Allyn SR'N•IP Update \Final Report\ Allyn S\ 7 f Report.doc Section 2—Characterization of the Allyn UGA Continued Surface water and shallow ground water flow (interflow) typically discharge to the east until they are intercepted by a roadside ditch running in a north -south direction along SR3. Stormwater collected in the ditch along SR3 then flows in the ditch, parallel to the road, until it encounters one of ten culverts, and then flows through these culverts to the east, discharging directly into North Bay. The slope of this easterly basin is from west to east, down to North Bay and ranges from 25 to 5 percent, as the land gradually slopes toward the beach along North Bay. Subbasin 4-Sherwood Creek In the southernmost subbasin, surface water runoff drains directly into Sherwood Creek, where contours are roughly parallel to the creek alignment. Slopes in this area typically range from 50 to 10 percent, as the steeply sloped ravine slopes toward the beach along North Bay. Only a small portion (< ten percent) of the Allyn UGA is located within this subbasin. Soils The soils within the Allyn UGA, as mapped by the Natural Resources Conservation Service (FRCS), formerly the U.S. Soil Conservation Service (SCS), are shown in Figure 2-2 Nearly half of the soils present are Alderwood gravelly sandy loam, with about 15 percent of the soils characterized as Sinclair spotty loam. Both of these soils are underlain by a cemented till layer at depths of 28 to 48 inches. This layer has a low permeability and permanently restricts infiltration of stormwater. In general, there is little infiltration within the Allyn UGA except in relatively small isolated pockets. Most runoff flows over the surface or as shallow interstitial, shallow groundwater until it reaches Anderson Lake or North Bay. There is, however, the presence of relatively small amounts of Everett and Indianola gravelly sandy loam and loamy sand units, which have good infiltration capabilities. They represent less than ten percent of the UGA soils, and are generally located along the North Bay shoreline, within the flatter areas of Sherwood Creek, and in a couple small areas in the most western areas of the Lake Anderson subbasin, as shown in Figure 2-2. Minor areas of Indianola loamy sand (excessively drained), McKenna gravely loam (poorly drained) and Norma silt loam (poorly drained) are also present in small isolated locations within the study area Due to the soil types, most stormwater will run directly off, following local topography, with little natural detention, treatment or infiltration. AIason County Allyn UGA Stormwater Management Plan 18 otak K:\project\30700\30784\Reports\Allyn SWMP Update \Final Report\Allyn SWIM Reportdoc -J 0 0 QO CO 0 as 4.1 .-14 • r...1 Section 2—Characterization of the Allyn UGA Continued Sensitive Areas Sensitive areas include steep slopes (areas with slopes of 15 percent or more), hydric soils wetlands, and geologic hazards, which include landslide, seismic and erosion hazards. (Refer to Mason County Draft 2006 Critical Area Update for hazard area criteria). Critical areas within the UGA (as provided in the shape files obtained from Mason County) are delineated in Figure 2-3. Note the substantial amount of area within the Allyn UGA, especially within the East Drainage Basin, that has land with slopes exceeding 15 percent, which will reduce the ultimate development potential of these properties. Land Use Existing land uses within the Anderson Lake subbasin and the western portions of the North Bay subbasin are primarily residential and recreational (golf course), as shown in Figure 2-4. 'I'he Devereaux Lake subbasin is currently undeveloped The existing land uses within the North Bay subbasin are largely forest of pasture, interspersed with small amounts of residential. A thin strip of commercial area exists along either side of State Highway #3 and along the beach of North Bay. The southerly, Sherwood Creek basin has a small amount of dispersed single family residential development in the flatter areas, directly adjacent to the stream. Elsewhere in the basin, the primary land use on the steeper slopes is forested in native trees and vegetation. Portions of the Port of Allyn are located within the Allyn UGA. The Port of Allyn property is located east of SR3 and north of East Drum Street as well as Kayak Park. The Port's facilities include a pier that extends out into North Bay. Ivioson County —Allyn ("GA Stornater Management Plan 20 otak h:\project\30700\30784\Reports\Allyn SnCN{P Update \Final Report\Allyn S AI Report.doc -J I I ,5 e, s< eDgE E -42 al 0 0 a, 0 as 0;3 0) 4.7. 2 17i r-' tO• "'"' lal Open Open V) " Eb < es. Section 3—Existing Stormwater Facilities Existing Stormwater Facilities Within the Allyn UGA, Mason County constructs and maintains the public drainage facilities consisting primarily of ditches and culverts within the County road rights -of -way. Within the LakeLand Village Development, in the West Drainage Basin, there are both public and private storm drainage facilities. The storm drainage facilities located within the platted road rights -of -way are County -owned and Count) -maintained. Outside of the public rights -of -way, the stormwater facilities are owned and maintained by the LakeLand Village Development Corporation. Elsewhere, throughout the East Drainage Basin, the County is responsible for providing and maintaining the drainage facilities to support existing and future development. As noted in Section 2, for the purpose of managing stormwater within the Allyn UGA, the UGA has been divided into two major stormwater management areas: the West Drainage Basin and the H ast Drainage Basin. This division represents the unique drainage, soils, and topographic features that allow the west half of the UGA to drain into Anderson Lake and discharge into North Bay via Sherwood Creek, and the east half of the study area to drain directly into North Bay. West Drainage Basin (Including Anderson Lake and Devereaux Lake Subbasins) The 775-acre LakeLand Village Development, as shown in Figure 3-1, impacts three of the four basins (Basins #1—Anderson Lake, #2 Devereaux Lake and #4—Shervood Creek) within the .Allyn UGA. It has its own stormwater management plan and owns and maintains its own stormwater facilities. The "LakeLand Village Storm Drainage Report" is attached as Appendix A. It has been prepared by the LakeLand Village Development Corporation to describe and document the nature and functions of the LakeLand Village stormwater system. Stormwater runoff from the LakeLand development and the 27 hole golf course is collected in a ditch and culvert system along public and private roads. Most of the runoff is conveyed to Anderson Lake. Anderson Lake is the largest of ten constructed detention wetponds within the development (McCullough). Anderson Lake outlets to Anderson Creek, which flows to Sherwood Creek and enters into North Bay at the south end of the UGA. Small portions of the existing LakeLand Village Development drain south into Anderson Creek, north to Lake Devereaux, or east to North Bay. Future LakeLand development in the northwest area of the UGA (Subbasin 2 Devereaux Lake) is planned to drain principally to Devereaux Lake. Mason County Allyn UGA Stormwater Management Plan 23 otak K:\project\30700\30784\Reports\Allyn SR7dP Update \Final Report\Allyn SWAI Report.doc .4. 1 —1. j �T( Olt 1Ilk I IMMO • 1 �tIr. + t Wit+ f k . (> , . 1 s{ f t€ • J V R e /X i sfilN4G1 t -.2, b.� f , . 1 D ler !t e ) 11�`° UDR 9• Np f t RY 4 is t�s55.15 t 1�I/1® .< pt�Ie® ;`ram llnq� t s. yr®! 'Y 91 .Si ► t y� ,t ® 1►1�trtr�w ,�{{yy- }/ {gypp y� .54. .`"{',.� a •a 1 I at Xi tir 's if, t ;tt pus �,rr A3 f ,. ► e . ., low go ' rARy , !+�i� 'aim a vA , /� t ; ® . ax° • �' ai t�r� ��j is*�QC ey1• ` I i t` rf 4 MI4 e� I � It" tit �k. r hr Cil+o i� rfwPOND15 �����;1�+ ; -•� a� ' r` { 1 t ,,If �i ,,, +1'� "'►�e��6 Eiq (' dip aaara• .eir. lit 4. 7 ri ass f 100.' A f l �tf°rl. •jsf ►� rat ill ANDER$d N 1 �i �� CREEK O O �® ' 1�,�r. „ c $ ✓ f f ` t aRA(,NA �y sq :1 , t $ At to a 4 f fJ l�ry. ±( GI. il 4NV lile Li; es t° ' t ►Ar d ai1G!aJi �1�'�i z fa—" LAKELAND VILLAGE WATERSHED AND 5' CONTOURS Figure 3-1 Lakeland Allyn Stormwater Village Management Map Plan ""~""5� `� � 2 'W �.:,... 20 ?Wardt., e• 4,ta V#cra OM 421-:1372 Ftcre. (4251522,14.:5 Fxe: (:MP 427-.V Fax j-25)S275+11 KJproject/30700/30784/G IS/mxds/Figures/LocationMapvER2. mxd Section 3 Existing Stormwater Facilities Continued East Drainage Basin (Including North Bay and Sherwood Creek Subbasins) The existing Allyn stormwater conveyance system is characterized by ditches and culverts, natural channels, and one short section of catch basin inlets along the west side of SR3 between East LakeLand Drive and East Wade Street. The drainage from this basin discharges to North Bay either through culverts under SR3, or under the bridge at Sherwood Creek, as shown in Figure 2-1. In the Fast Drainage Basin, the culvert inlet locations along SR3 shown in Figure 2-1, were established from a review of the County's runoff analyses for the Wheelwright Street area, Washington Department of Transportation (WSDOT) construction documents for SR3, and field reconnaissance. The culverts are estimated to range in diameter from 18 inches to 24 inches. Photo 5 Existing Culvert Crossing Under SR3 All a s o n C; a it n i y A/ n U G A S t o r m w a t e r dl a n a g e m e n t Plan 25 otak h:Aproject \30700\3078.1\Repo rts\Allyn SWMP Update\hi lid Repo0\Allyn S\ vi Reportdoc Section 3 Existing Stormwater Facilities Continued The Allyn/Wheelwright Runoff Analysis'" included a subbasin map, which showed the delineation of three subbasins and the approximate location of eight culverts crossing SR3 that outfall into North Bay. Two additional culverts under SR3 (south of LakeLand Drive) have also been verified by construction drawings provided by WSDOT. Otak engineers - performed drainage reconnaissance of the study area during the months of October and November, 2006. The culvert locations identified in the Wheelwright analysis and on WSDOT plans were used as a guide to find and verify the culverts in the field The inlets to these ten culvert crossings under SR3 were sighted in the field; however, only one outlet was found. (The culvert outlets that were not found are believed to be either underwater, located on private property, or to have been buried. The WSDOT plan sheets show the culvert outlets at sea level, and therefore are likely to be visible only during low tide.) On -Site Stormwater Detention Ponds in the East Basin In addition to the stormwater facilities, including ten wetponds, located within the LakeLand Village Development, there are two existing stormwater ponds within the UCA. The church located at the south end of Wheelwright Road has a small onsite stormwater pond. And a second pond is located at the assisted care facility on East Masterson Street, just east and down the hill from the facility, as shown .in Figure 3-2. Photo 6 Onsite Stor iiwater Pond by the Church 2 Allyn/Wheel tight Runoff Analysis, by Alan A. Tahja, Mason County, December 29,1995 llasois Connty /illyn UG.f1 .S%ormunateanagement Plan 26 otak K:Aproject\30700\30784\ Reports \Allyn SWNIP Update al Report \Allyn SWAT Report.doc Aittf..117, 'OF - J I I 4 - 0 O • 0 W as J r", bi) • 4.1 Section 3 Existing Stormwater Facilities Continued Existing Conditions Current Reported Drainage Deficiencies West Drainage Basin Existing stormwater deficiencies within LakeLand Village Development are documented on page 18 of the "LakeLand Village Storm Drainage Report, ' included in Appendix A. They are minor in nature and, being largely private systems, are the responsibility of the LakeLand Village Development Corporation. The drainage facilities, however, that are within the County load rights -of -way, including the roads within LakeLand Village, are the County's responsibility for maintenance, repair, and replacement as needed. East Drainage Basin Outside of LakeLand Village only one stormwater deficiency has been documented within the Allyn UGA. It is believed to be associated with the increased runoff associated with land clearing on the above sloping properties. This deficiency, noted by County staff in October 2006, is a small flooding problem located at the southwest corner of East Wade Street and SR3. It is a low spot at the inlet to an existing 12-inch culvert that goes under SR3, as shown in Figure 3-2. This localized ponding is contained on the west side of SR3 and has not been documented to flow over the highway. Mason County —Allyn UGA Stormwater Mlanagement Plan 28 otak K:\project\30700\30784\Reports\Allyn SWMP Update\Final Report\Allyn SWM Report043007.doc Section 4 Future Conditions Future conditions relating to stormwater management within the Allyn UGA are described in this section. These are defined by future zoning, as presented in the A113 n Comprehensive Plan (2005) and its associated land use cover criteria, as shown in Figure 4-1. Allyn Comprehensive Land Use Plan The Allyn Comprehensive Plan includes proposed future zoning for the Allyn UGA. Future land use cover assumptions for the proposed zoning range from 15 to 100 percent impervious area, as shown in Table 4-1 The degree of development assumed for several areas was modified in a meeting between Mason County Staff and Otak in those areas where development would be constrained by steep slopes'. These modifications reduced the maximum allowable impervious area percentages for those areas. The modified maximum allowable impervious area assumptions have been included in lower half of Table 4-1. The areas with reduced land use densities due to steep slopes aie shown in `hatched' areas in Figure 4-2. 4 I —Allyn UGA: Future Land Use Assumptions Table Cover Description % % Forest % Pasture % Grass % Water Impervrous UGA Zoning Land Uses R-1 40 0 0 60 0 R-1P 50 0 0 50 0 R-1R 65 0 0 35 0 R-2 60 0 0 40 0 R-3 70 0 0 30 0 CM 90 0 0 10 0 FIC 80 0 0 20 0 POS 15 0 0 85 0 VC 100 0 0 0 0 VR 90 0 0 10 0 A'iodified Land Uses Effective Area is 0 0 25 25 50 0 Impervious R2 — 60% Developable 35 0 40 24 0 Right of Wa) 90 0 0 10 0 land use = Future 3 30 25 42 0 Existing Steep Slopes 0 50 50 0 0 3 Personal Communication: Steve Goins, Senior Planner, Mason County, November 15, 2006. Mason Count) .Allyn UGH Stormwater lfanagenient Plan K:\project\30700\3078 4\Reports\Allyn S\VL"v[P Update \Final Report\Allyn SWi Report.doc 29 otak ci) C E 92 4'10222aa'co a Li- 5.0 11 VJ (6 p N a) O la t4 O) o w N Section 5—Regulatory Design Criteria Regulatory Requirements Minimum Stormwater Management Requirements The regulatory requirements for stormwater management are contained in *Ecology's 2005 Stormwater Management Manual for Western Washington (SWMM) and in the various Mason County codes and regulations. The SWMM sets forth ten minimum requirements for stormwater management that are required for development and redevelopment. These are listed in Table 5-1. All stormwater plans must demonstrate compliance \\ ith these applicable minimum requirements. (Note that the full text of the minimum requirements should be referred to for a complete understanding of the requirements.) Ecology 2005 Manual: Minimum 5- I Management Requirements Table Stormwater Minimum Requirement Requirement 1 Preparation [outlined local of in the government Stormwater Site 2005 Manual Plans shall prepare meeting the thresholds a Stormwater Site Plan fbr —Allprojects Ecology review. 2 Construction which square Construction Stormwater net»plus as part Pollution 7,000 replaced square of the Storimvater (SWPP) surfaces or more of land Site Plan. — Projects in total 2,000 must prepare a Prevention impervious feet or or disturb Plan the new, feet or more, S replaced, IPPP 3 Source Control control Best Management maintained according of Pollution to [the Practices — All (BMPs) 2005 known, shall Manual]. available and reasonable source be selected, designed, and Ecology 4 require Preservation drainage occur which impact of discharged shall Natural patios. be location, from receiving maintained, Drainage Systems and and discharges to the maximum extent the project site must not waters and downgradient. Outfalls from the practicable. cause properties. significant —1\Tatural project Then All site shall manner by adverse outfalls patterns at the natural runoff is to downstream energy dins ]Mason County Allyn UGA Stormwater Management Plan K:\project\30700\30784\ReportstAllyn SWAMP Update \Final Report\Allyn S\V\I Report.doc 32 otak Section 5—Regulatory Design Criteria Continued 5 On -site Stormwater Stormwaterivlanagement runoff onsite impacts. maximum Management BLVIPS — Projects should employ On -Site disperse, and retain stormwater without causing flooding or erosion to the to infiltrate, extent feasible 6 Runoff treatment generating discharge through use Direct by of On -Site [Mary discharge tormwater projects/ require construction of untreated stormmater to ground water is prohibited, or dispersion of runoff Management BMPs. of stormwater from pollution- except for the from residential sites Treatment facilities. impervious achieved — surfaces infiltration S 7 Flow stormwater requirement through to Control runoff applies a conveyance [art approved — from direct Projects must provide flow control to reduce impervious surfaces and land cover conversions. to projects that discharge stormrwater directly, system, into afresh water— except forprojects discharge receiving water] the impacts of The or indirectly that discharge 8 Wetlands conditions, support existing hydropfytic Protection — Discharges to wetlands shall maintain the hydrologic vegetation, and .substrate characteristics necessary to and designated uses. 9 Basin/Watershed stringent minimum requirements... Planning — Projects may be subject to as identified in Basin/ [Watershed equivalent or more Plans. 10 Operation shall (or and be provided responsible for Maintenance — An all proposed stormwater for the maintenance operation and maintenance facilities and BMPs, and operation shall manual... and the party parties) be identified. Minimum Requirements for New Development As quoted from the 2005 SWIM Manual: All new development shall be required to comply with ?vlinzrraurN Requirement #2, entitled Constrztetion Stormwater Pollution Prevention. New development shall comply with Minimum Requirements # 7 through II _ for the new and replaced impervious surfaces and the land disturbed (if the proposed new development): • Creates or adds 2,000 square feet, or greater, of new, replaced, or new plus replaced impervious suface area, or- • Has land disturbing activiy of 7,000 square feet or greater Mason County Allyn UGA Stormier Management Plan 33 otak K:\project\30700\3078.4\Reports\Allyn SWN[P Update\Final Report\Allyn S\V? I Repoct.doc Section 5—Regulatory Design Criteria Continued The following new development shall comply with Minimum Requirements # 1 through # 10 for the new impervious surfaces and the converted pervious su faces (if the proposed new development): • Creates or adds 5,000 square feet, or more, of new impervious surface area, or • Converts 3/4 acres, or more, of native vegetation to lawn or landscaped areas, or • Converts 2.5 acres, or more, of native vegetation to pasture. Minimum Requirements for Redevelopment As quoted from the 2005 Manual: All redevelopment shall be required to comply with Minimum .Requirement #2. In addition, all redevelopment that exceeds certain thresholds shall be required to comply with additional Minimum Requirements as follows. • Redevelopment shall comply with Minimum Requirements # 1 through #5 for the new and replaced impervious surfaces and the land disturbed (if): - The new, replaced, or total of new plus replaced impervious surfaces is 2,000 square feet or more, or - The redevelopment involves more than 7,000 square feet or more kind disturbing activities. • Redevelopment shall comply with Minimum Requirements # 1 through # 10 for the new impervious surfaces and converted pervious areas (if the new redevelopment): • Adds 5,000 square feet or more of new impervious surfaces or, - Converts 3/4 acres, or more, of native vegetation to lawn or landscaped areas, or - Converts 2.5 acres, or more, of native vegetation to pasture. • If the runoff from the impervious su faces and converted pervious surfaces is not separated from runoff from other surfaces on the project site, the stormwater treatment facilities must be sized for the entire flow that is directed to them. • Also note that: The local government may allow the Minimur Requirements to be met for an equivalent (flow and pollution characteristics) area within the same site. For public roads' projects, the equivalent area does not have to be within the project limits, but must drain to the same receiving water Flow Rate Control Requirements In regard to flow control, the stormwater compliance criteria used in this stormwater planning study are taken directly from 1 cology's 2005 SWMM for Western Washington. The compliance criteria, set forth in the SWMM for basins requiring rate control, are as follows: 1. Storniwater discharge shall match pre -developed conditions flow duration values from % of the 2 year flow frequency through the 50year flow frequency. Matching flow durations ensurer that ary potential erosion problems downstream of the development are not exacerbated by the proposed development.) Mason County —Allyn UGA Stormwater Management Plan 34 otak K:\project\30700\30784\Reports\Allyn SWINAP Update \Final Report\Allyn S\VN-I Report.doc Section 5—Regulatory Design Criteria Continued 2. Developed peak discharge rater should match pre -developed conditions peak flows for the 2-, 10-, and 5 0- year return periods. (Matching peak flows ensures that the downstream system will continue to have the capacity to carry the expected flow rates.) Direct Discharges to Saltwater Do Not Require Detention Note that the 2005 SW1\4.I\4 manual's flow control requirement applies only to stormwater runoff that discharges into fresh water. The 2005 Manual does not define flow control requirements for freshwater discharges into salt water receiving water bodies .Thus for the Allyn UGA, stormwater discharges into salt water, such as Puget Sound, do not need to meet any special detention requirements and may be directly discharged into North Bay. Water Quality Treatment Requirements The 2005 SWIM presents t\vo sets of requirements for the selection of water quality treatment methods, depending on the type of development that is being constructed. The Basic Treatment Menu is the standard for most residential developments, including those that discharge into salt water. However, there is also the Enhanced Treatment Menu that applies to developments with a more intense use of impervious areas and greater potential for pollutants leaving the site, including new roads and highways and commercial developments. These two menus are summarized below: The Basic Water Quality Treatment Menu allows any of the following options to be used: -Bio-infiltration Swale-Stormwatei Treatment Wetland -Infiltration -Combined Detention and Wetpool Facilities -Sand Filters -Bioretention/Rain Garden -Bio-filtration Scales -Ecology H mbankment -Filter Strips - `StormFilter' with ZPGTM media -.Basic Wetpond-Wetvault To meet the Basic requirements, it is common for a developer to use either bio- infiltration/bio-filtration swales or some form of a wetpond, depending on the shape and amount of space available on the site. Wetponds are sized with continuous simulation models to treat the volume associated with the 91 percent exceedance value of all flows during the period of simulation, which is generally equivalent to 0.64 times the amount of precipitation of the 2-year, 24 hour storm event. Mason County Allyn UGA Stormwater Management Plan 35 otak IC: \project\30700\3078 4\Reports\Allyn S\C'.\IP update\Final Report\Allen SWM Report.doc Section 5—Regulatory Design Criteria Continued The hnhanced WaterQuality Treatment Menu allows any of the following options: - Infiltration with Appropriate Pretreatment - Large Sand Filter - Amended Sand Filter -Stormwater Treatment Wetland - Compost-amended Filter Strip - Two Facility Treatment Train - Bioretention/Rain Garden -Ecology Embankment To meet the h nhanced requirements, a developer will often use a two facility treatment train or a constructed wetland Sand filters may be required for special pollutant removals such as nutrients. Low Impact Development Techniques Ecology encourages the use of Low Impact Development (LID) techniques for stormwater management where appropriate. The Low Impact Development Technical Guidance Manual for the Puget Sound describes LID as follows Low impact development (1ID) is a stormwater strategy that emphasizes conservation and use of natural site features integrated with distributed, small-scale stormwater control) to more closely mimic natural hydrologic patterns in residential, commercial, and industrial settings. LID methods are presented in Appendix B. LID techniques have been considered in the development of the stormwater alternatives for the Allyn UGA. LID techniques may reduce or eliminate the size of stormwater facilities and infrastructure. LID would be especially effective in areas with outwash soils, such as Everett and Indianola, as shown in Figure 2-2. Outwash soils are well drained with little generation of surface runoff. Such soils are well suited for LID techniques such as downspout dispersion and permeable pavement. There are a large variety of LID options available; descriptions of potential LID options are included in Appendix B. Flow Control and Water Quality Treatment Within the Allyn UGA East Drainage Basin: East Uplands and Shoreline Subbasins It is fortunate that much of the East Drainage Basin of the Allyn UGA lies next to and can discharge directly into such a large receiving water body, as the southern reaches of Puget Sound (i.e. Case Inlet/North Bay). Discharging directly into such a large, local recei\ing water eliminates the need for any onsite detention, although onsite water quality treatment requirements still must be met. Thus, much of the stormwater runoff from the Allyn UGA can be discharged directly into North Bay without any onsite or regional detention according to Ecology s 2005 design standards. Mason County Allyn UGA ,Stormwater Management Plan 36 otak h:\project\30700\30784\Reports\Allyn S\ViIP Update \Final Report \Allyn SW:\[ Report.doc Photo 7 Section 5 Regulatory Design Criteria Continued North Bay From South End of UGA Looking North West Drainage Basin and Sherwood Creek and Unnamed Tributary Any new development within Anderson Lake and Devereaux Lake Subbasins within the West Drainage Basin, along with the two streams in the F,ast Drainage Basin, Sherwood Creek in the south and an unnamed drainage tributary to North Bay, as shown in Figure 2-1, will require flow control as well as water quality treatment since they discharge into existing streams prior to discharging into North Bay. This is also true for the drainage that drains toward Devereaux Lake. These requirements help to reduce scour, erosion, and sediment transport within these local streams and help to preserve remaining ecological and habitat functions. Drainage in the Devereaux Lake subbasin may be infiltrated in local outwash soil deposits. Mason Corrnty Alj'n C'G.A. Stormn'aier illanacgenien/. Plan 37 otak K:Aproject\30700\30784\Reports\Allyn SWMP Update\Final Report\Allyn SWM Reportdoc Section 6—Hydrologic Modeling and Engineering Presented in this section is the development and selection of stormwater management alternatives for the Allyn UGA. The selected alternatives will form the UGA's stormwater facility plan. The objective of the plan is to address existing drainage problems and mitigate stormwater impacts from future development. Ilydrologic modeling performed to size the stormwater facilities is described, as well as the development of the stormwater improvements to accommodate future conditions in the UGA. Both onsite and regional options have been considered in the development of the recommended stormwater management alternatives. Hydrologic Modeling Hydrologic modeling was used in the development of the Allyn UGA Stormwater Management Plan to evaluate existing stormwater facilities and identify those facilities needed to support future development. Results of the modeling, described below, were used to identify and size water quality, rate control, and outfall facilities within the Allyn UGA. Because the major regional and onsite drainage facilities within the West Drainage Basin are owned by the LakeLand Village Development Corporation, the focus of this hydrologic modeling effort has been on the East Drainage Basin that discharges directly into North Bay. Modeling for the West Drainage Basin, as provided by the LakeLand Village Development Corporation, is described in Appendix A. In this section the modeling methodology for the East Drainage Basin is initially described. The results of facility sizing, based on the flow results of the model under existing and future conditions, are then presented for applicable basins. Proposed stormwater capital improvement projects were developed based on these modeling results and the associated engineering analyses to meet the needs of future development. Modeling Methodology The hydrologic analysis for the Allyn UGA was completed using a continuous simulation model, MGSFlood, Version 3. MGSFlood is a continuous, rainfall -runoff model developed specifically for stormwater facility design in Western Washington. It based on, and is consistent with, the design requirements of the 2005 Stormwater Management Manual for Western Washington. The program uses the Hydrologic Simulation Program -Fortran (HSPF) routine for computing runoff from rainfall. MGSFlood uses one -hour time step precipitation data to predict flow rates. A GIS analysis was used to delineate soil -cover areas for modeling. Results of the hydrologic and hydraulic modeling are presented in Appendices C and D, respectively. Mason Co7117t3—Allyn UGA Storminater Management Plan K:\project\30700\30784\Reports\Allyn SWNIP Update \Final Repo Allyn S\Vj\{ Report.doc 38 otak Section 6—Hydrologic Modeling and Engineering Continued West Basin: Existing and Future Conditions Modeling Note that no modeling or engineering was performed for the West Drainage Basin (i.e. the LakeLand Village Development). This analysis was performed by the LakeLand Development Corporation and is presented in Appendix A. East Drainage Basin: Existing and Future Conditions Modeling In the East Drainage Basin, existing conditions were modeled to verify reported existing flooding. Future conditions were modeled to identify needed stormwater facility improvements to support ultimate buildout of the Allyn UGA based on the land uses described in the Allyn Comprehensive Plan, as summarized earlier in Table 4-1. Subbasin boundaries foi existing and future modeling analyses are shown in Figures 6-1 and 6-2, respectively. Note that these existing subbasin boundaries have been modified during the modeling process to accommodate the capital projects needed to support ultimate development. As graphically shown in Figure 6-2, a number of subbasins have been re- routed and/or combined with other subbasins to reduce the number and cost of needed regional treatment, culvert, and outfall facilities. Existing Conditions Modeling Flooding has been reported at the southwest corner of East Wade Street and SR3. This is a low spot located at the inlet to an existing 12-inch culvert that goes under SR3. The MGSF1ood analysis, however, shows that this existing 12-inch concrete culvert should be adequate to convey the flows from this subbasin (Subbasin EE030) with a headwater diameter ratio of less than 1.25. The slope of the existing culvert was estimated, based on WSDOT as -built data of other culverts within the Allyn area that cross under SR3 and discharge into North Bay. Based on this finding, this culvert may be blocked or may otherwise have a limited flow capacity. The existing culvert should be further analyzed to ensure the assumed culvert slope was modeled correctly, and to determine the remaining life of the culvert. Inspection and maintenance is required and is recommended to determine. if the culvert should be cleaned and/or- any blockages removed to ensure full design capacity is available. Future Conditions Modeling For future conditions modeling, the East Drainage Basin was delineated into 12 subbasin areas, including the Sherwood Creek subbasin. These .drainages were grouped and named according to their proposed discharge location. Table 6-1 lists the grouped drainages and shows which subbasins they contain and their drainage areas. Also shown is the rate Mason County Allyn UGA Stormwater Management Plan 39 otak K:\project\30700\30784\Reports\Allyn SWIVIP Update\Final Report\Allyn SWM Report043007.doc av II dtekaffreptr.../. NS w Li U.- 'r-0-'114At°76- 74.4'477,' 50 5 0 Of) Section 6—Hydrologic Modeling and Engineering Continued control/outfall location and the type of water quality treatment that was used. Consistent with the 2005 Ecology Manual, the more intensely developed commercial areas discharging to fresh water require the use of the enhanced water quality treatment menu. The subbasins for future condition modeling are graphically displayed in Figure 6-2. The labeling of each subbasin in Figure 6-2, such as EF010, designates which subbasins were grouped together for collective analyses using the model. Table 6 I Drainage Basin: Future Conditions Subbasin Groupings —East Area (ac) Flow Control / Outfall Water Quality Subbasin #(s)* Subbasin Name Sherwood North Creek SF010 52 1 Flow discharge control to and creek Basic Required Menu Sherwood South Creek SF020, 0030 21.1 Enhanced Menu discharge Flow control to and creek (HC Required zoning) Unnamed Creek EF015 18 2 Discharge to channel Basic Menu Required Kayak Park F.F080 25.6 Direct discharge outfall to new Basic Required Menu 127.6 Direct discharge outfall to new Basic Required Menu Evans Street EF040, EF050 Wade Street 53.7 Direct discharge to new Basic Menu EF030, EF035 outfall Required 86.7 Direct discharge outfall to new Basic Required Menu EF010, EF025 EF020, Tacoma Easement Power Total Area: 385.0 * SF = Sherwood Creek Future, EF = East Uplands Future illason County —Allyn UGA Stormn'ater Management Plan 42 otak K:\project\30700\30784\Reports\.Allyn SV'?vtP Update \Final Report\_\]lyn SWM Reporr.doc Section 6 Hydrologic Modeling and Engineering Continued Engineering Analysis: Alternative Analysis and Sizing Rational and Approach to Stormwater Management To develop the drainage infrastructure needed to service both existing and future land uses within the Allyn UGA, stormwater management strategies were developed for both the West and East Drainage Basin West Drainage Basin: Stormwater Management Strategy and Discussion The West Drainage Basin is contained totally within the LakeLand Village Development. Stormwater management planning for this basin is being performed by the LakeLand Village Development Corporation. The majority of the West Drainage Basin has already been developed and most of the major stormwater management facilities ale already in place. (See Appendix A for a descnption of the drainage facilities within the LakeLand Village Development.) The remainder of the West Basin (in the most northwest corner) is planned to be platted in the near future. This includes approximately 80 acres located in the northwest corner of the UGA. Runoff from this newest phase of the proposed LakeLand Village Development will drain primarily to Lake Devereaux, with some runoff draining to Anderson Lake The "Lakeland Village Storm Drainage Report" (Appendix A) presents two development alternatives for the northwest comer of the UGA. (The drainage system for the rest of the LakeLand Village Development has already been constructed.) One alternative is for a 60- acre development; the other is for an 81-acre development. Implementation of the selected alternative will complete buildout of the LakeLand Village Development. The required water quality and detention volumes were calculated for both of these two proposed alternatives. Results are provided in Table 6-2 (Table 5) and Figure 6-3 (Figure 17) taken from the `LakeLand Village Storm Drainage Report," included in Appendix A. LID techniques were included as additional recommended management tools in the analysis. Mason County —Allyn UGA Stormwater Management Plan 43 otak K:\project\30700\30784\Reports\Allyn SWMP Update\Final Repoli\Allyn SWIVI Repoit043007.doc umen Required (acf 0) 14 12 10 8 6 4 2 0 2 Density vs WO and Detention Volumes using StormShed2G ) 3 4 Density (DU/Ac) 6 —et— 60 Ac WQ Volum e+S heet3l$A$6 60 Ac Detention Vol (acft) 81 Ac WQ Volume (Acft) 81 Ac Detention Vol (acft) Figure 6-3 Density vs WQ and Detention Volumes Allyn Stormwater Management Plan 4I1 North P0 &n.21 etrp,e ,rm3an4=54 flz�n (.p6J<2Yy70 t.0 p.1)42'5425 492910E P Y4 DM su"csdtn roar,), rran�ae vr•rf/r (425)Sfl Fat (425)F.ZT S71 KJproject/30700/30784/GIS/mxds/Figures/DensityVSWAandDetention.mxd Section 6—Hydrologic Modeling and Engineering Continued Table 6 2 Density vs Water Quality and Detention Volumes (From Appendix A, Table 5) Density vs Water Qualtu and Detention Volumes for Development of Drainage Basin Deveraux - 2 Future 60 Ac Alt 81 Ac Alt Density WQ Vol (acft) Detention (acft) Vol WQ Vol (acft) Detention (acft) Vol 2 7.5 7.722 10 10.257 3 7.9 8.242 10.5 10.972 4 8.3 8.736 11 11.635 6 8.8 9.36 11.7 12.48 East Drainage Basin: Stormwater Management Strategy and Discussion For the purpose of developing stormwater management strategies and associated facilities to meet the conditions within the East Drainage Basin, the basin was divided into three major stormwater management areas (SWMAs). The various subbasins within each of these SWMAs were then grouped according to common land use, soils, drainage, topography, water quality treatment needs, detention, and discharge characteristics. The result was the creation of three stotuiwater management areas, as listed and described below. These areas are shown in Figure 6-4. • Stormwater Management Area # 1 The East Uplands SWMA includes the area between the east boundary of the West Drainage Basin and SR3 and the east side of North Bay Road; it includes eleven subbasins that discharge through culverts under SR3 before entering North Bay. This SWMA also includes a small unnamed tributary, at the most northern end of the SWMA This subbasin must have onsite water quality treatment. (Note that the future flows of this subbasin do not exceed the flows of existing conditions, when the flows from the upper area of the drainage area have been directed to the south to the East Wade Street Outfall, and therefore no onsite or regional detention is required under full buildout conditions.) • Stonnwater Management Area # 2—The Shoreline SWMA includes all the parcels that ate east of SR3 and North Bay Road, and discharge directly over the beach and into North Bay. • Stormwater Management Area # 3—The Sherwood Creek SWMA includes the two subbasins located on either side of the Sherwood Creek that discharge directly into the creek just prior to passing under the SR3 bridge and into North Bay. This segregation of the three SWMAs within the East Basin is based on the different stormwater management strategies being proposed to meet stonnwater quantity and quality :standards for each area, as described below. Mason, County Allyn UGA Stormwater Management Plan 45 otak K:\project\30700\30784\Reports\Allyn SWMP Update\Final Report\Allyn S\X/M Report043007.doc Figure 6-4 Stormwater Management Areas Allyn Stormwater Management Plan ,SxN_RELINE ST R_MWATER ANAGEMENT AREA .:i1 t.G h€N PO Lux 213 ed. tI thilfrgl 55594 2'cre (310t521.515 popITNi425 :au ar, CO slVI nS5333 (425) 522 445 (425) 62Tb577 K:/project/30700/30784/GIS/mxds/Figures/S WManagementAreasVer2.mxd Section 6—Hydrologic Modeling and Engineering Continued • SWMA #1—requires onsite or regional collection and treatment; discharges underneath SR3 into North Bay, ® SWMA #2 requires onsite water quality treatment; discharges directly into North Bay, and • SWMA #3—requires onsite detention with water quality treatment; discharges to a creek. The majority of the East Upland and Shoreline SWIVIAs are allowed by Ecology to discharge directly (without any onsite detention) into North Bay, after the basic onsite water quality treatment requirements have been met. The Sherwood Cieek SWIVIA discharges into an existing stream, and therefore require flow control (detention) to meet the stream protection standards in addition to onsite water quality treatment. Stormwater Management Area #1—East Uplands SWMA (Subbasins #EE 080, 070, 060, 050, 045, 042, 040, 030, 025, 020, 015, 010) The drainages within Stormwater Management Area #1 East Uplands SWMA were grouped together because they had similar land use, topography and soils. Also, from a stormwater management perspective, they could all be developed with only onsite water quality treatment with the all flows being allowed to be directly discharged into North Bay. As discussed below, stoimwater management alternatives were considered for both the short- term and long-term (ultimate buildout) conditions. Recommended approaches have been presented for collection/conveyance, detention, and water quality treatment. Two main options for the Last Uplands SWIVIA have been developed. The Short -Term Option addresses existing conditions and the Long -Term Option accommodates future development and ultimate buildout. East Uplands SWMA: Short -Term Alternative Collection/Conveyance, Water Quality Treatment, and Discharge Outfalls The Short -Term Option addresses existing conditions and ensures that the existing drainage sy stem is used as long as it has adequate capacity to accommodate both existing and incremental future growth. This option proposes to continue to discharge existing and future flows through existing culverts under SR3 and directly into North Bay. New development will need to perform water quality treatment. Existing development can continue to discharge untreated runoff until redevelopment occurs and onsite water quality treatment will be required. No regional facilities are proposed in this short-term approach. Also, no new collection and conveyance systems are being proposed at this time, until after an inventory and assessment of the existing conveyance pipes can be made. Mason Con aaty—Allyn UG.A Stormivater Management Plan 47 otak IC:Aproject\30700\30784\Reports\Ally SWMP Update\Final Report\Allyn SWI\I Report.doc Section 6—Hydrologic Modeling and Engineering Continued Currently this approach, with its existing system of ditches along road rights -of -way and culverts under SR3, seems to be functioning well, with local flooding at only one location during the larger storm events. To fully develop and validate this approach, an investigation of the capacity and condition of each of the eleven culverts and outfalls is needed. A proposed scope for this anal) sis is presented in Appendix F (This culvert analysis has been included in the recommended Allyn Stormwater Management Capital Improvement Plan (CIF) presented in Section 7). Once the culvert inventory/analysis has been completed, and with the capacities of the existing culverts known, a routing plan for existing and future flows to individual culverts can be performed and temporary late control facilities can be sized for any culverts with inadequate capacity. Regional water quality treatment facilities could also be sized and located, if desired, at this time. With the condition of culverts known, an assessment of the remaining service life of individual culverts can be made. Repair or replacement needs can be then be scheduled and included in the financing plan. This alternative requires coordination with, and approvals from, WSDOT, Port of Allyn and various property owners. Preliminary Engineering Analysis: Verification of Culvert Capacity in Short -Term An analysis of the runoff generated by the new 120 homes to be located within the East Drainage Basin on either side of LakeLand Village Drive over the next six years indicates about 6.7 cfs of new runoff during the 25 year, 24 hour event. This is about ten percent of the existing capacity of the four local culverts that pass drainage under SR3 and into North Bay Assuming these culverts are not at capacity and not blocked, as evidenced by the lack of existing flooding, there may be enough capacity remaining in the existing drainage system to collect and convey this new incremental increase in stormwater runoff under SR3 and into North Ba) over the next six years Details of this preliminary engineering analysis are presented in Appendix F. Recommendation for the Short -Term in the East Drainage Basin It is recommended that in the short-term, the County should continue to use the existing system of ditches, culverts, and outfalls to allow existing and future runoff to drain directly into North Bay. New development should be required to perform onsite water quality treatment. The validity of this approach should be confirmed by the suggested culvert analysis. East Uplands SWMA: Long -Term Alternative Mason County Allyn UGA Stornrwater Management .Plan K:Aproject\30700\30784\Reports \Allyn S\V'V[P Update\Final Report\tlllsm S\XTM Report.doc 48 otak Section 6—Hydrologic Modeling and Engineering Continued East Uplands SWMA: Long -Term Alternative A long-term option will be needed as growth continues on the slopes above SR3 and North Bay, and the existing collection and conveyance system approaches its maximum design capacity. This alternative requires the installation of new outfalls under SR3 that are sized to continue to direct all future development/redevelopment discharges directly into to North Bay, along with conveyance improvements and a number of regional water quality treatment facilities. These long-term capital projects needed for future ultimate development are shown in Figure 6-5. As with the Short -Term Recommendation, new development will need to perform water quality treatment using proposed regional facilities Existing development can continue to discharge untreated runoff until redevelopment occurs This long-term option was created to accommodate future growth. At some point in time, the capacity of the existing eleven culverts under SR3 will not be adequate to convey the increased flows from new development. When this occurs, the County (and WSDOT, Port of Allyn, and future developers) will be faced with the choice of either providing upstream regional •detention or creating a new collection, conveyance, and discharge/outfall system to North Bay. This alternative proposes the design and construction of four new culverts under SR3, and will require a number of easements from WSDOT and pnvate property owners. For this alternative, future conditions were modeled and facilities sized assuming existing culverts crossing SR3 would continue to convey SR3 runoff and that the new outfalls would convey all other runoff (from both new development and redevelopment) from the East Upland subbasin. Collection/Conveyance Systems In the future, when a new outfall is constructed, a collection/conveyance system along the west shoulder of SR3 will be needed to ensure runoff from the uplands is conveyed to regional water quality treatment facilities and the new outfalls. West of SR3, the current collection system of ditches and culverts will likely be adequate for the near term, as discussed in the Short -Term Option. However, as development continues upstream without flow control, increased runoff will begin to exceed the conveyance capacity of the existing ditches. At that time, implementation of the expanded pipe and ditch collection systems, shown in Figure 6-5 as the East Wade Street Conveyance (C TP # 1A) and the East Wade Street Conveyance (C1P# 1B), will be required Each of the four proposed outfall projects contain a conveyance line along the west shoulder of SR3. The expanded Mason County —Allyn. UGA Stormwater Management Plan 49 otak K:\project\30700\30784\Reports\Allyn S\X/MP Update\Final Report\Allyn S\XTM Report043007.doc I LI < - z Jo 0 0 0 U) 0 C6 0 - 4-4 Section 6 Hydrologic Modeling and Engineering Continued collection/conveyance system throughout the East Upland SWIM has been presented as CIP projects #1A and #1B. Regional Water Quality Treatment The acreage requirements for water quality facilities described in the long-term option are shown in Table 6-3. Note that potential sites for some of the proposed regional water quality treatment facilities have been identified and are shown in Figure 6-5.Also shown in Figure 6-5 are the recommended sites and acreages needed for future potential property acquisitions that may be used as public opens space for water quality facilities. Table 6-3—East Uplands Subbasin: East Uplands SWMA # I Long Term Option—Outfall Water Quality Requirements and Proposed Outfall Discharge Peak (cfs) Water Quality Location Basin Area (ac) 25 Year (cfs) 100 Year (cfs) Volume (cf) l Average Depth (ft) Required Area (ac)2 Diameter Kayak Park 18 in 25.6 9 2 11.5 89,700 3 0.8 42 in 127.6 56.0 70.6 608,300 3 5.6 Evans Street Wade Street 30 in 53.7 28.4 37.6 320,400 3 2.9 36 in 86.7 39.9 51.3 433,400 3 3.9 Tacoma Power Easement 1: Volume betsed on treating 100°A of runoff. 2• 'Taken as 120% of average pond area to account for berms, access, etc. The wetpond area requirements for regional facilities throughout the East Uplands Subbasin to support future/ultimate development will be large, as evident in the 127.6 acres required for the Evans Street regional water quality treatment facility. To reduce the amount of needed land, it may be beneficial to deepen the proposed wetpond(s), as local groundwater conditions allow. A maximum depth of eight feet is allowed by the 2005 SWWI\-1; three feet is the maximum for ponds with emergent vegetation. (Note that with shallow ground water, the State's new Underground Injection Control Rule may also apply.) 'I`he public has already suggested that the 1.56 acre parcel of land located at the northeast corner of the intersection of LakeLand Drive and Wheelwright Street be used for a regional facility. Such a facility could treat tunoff from land west of Wheelwiight Street, however, a second facility will still be needed to treat runoff from east of Wheelwright Street. While multiple sites and flo\\ splitters require a more extensive conveyance system, they help to AIa.roa County Allyn L'GA SLornawe ler Management Plan 51 otak h:\project\30700\30784\Reports\Allyn S\VMP Update \Final Report\Allyn SWiNI Report.doc Section 6—Hydrologic Modeling and Engineering Continued alleviate the space requirements by developing fewer, but larger regional water quality treatment facilities within the Evans Street Subbasin. Photo 8 Public Suggested Site of Regional Water Quality Treatment Culverts and Discharge Outfalls For ultimate buildout within the Allyn UGA, the long-term option is recommended. This alternative proposes the construction of four new, larger pipes under SR3, enclosing some of the ditches along the west shoulder of SR3 into a buried pipe to accommodate commercial growth, and the creation of regional water quality treatment facilities that can accommodate all new development and redevelopment within the UGA. The locations and size of long- term outfall and water quality treatment components are shown in Table 6-4. Stormwater Management Area #1: East Uplands - Unnamed Creek Subbasin (Subbasins # EF 010 and 015, located at the north end of the Allyn UGA) The Unnamed Channel subbasin is unique because it discharges to an open channel, but does not require flow control. Flow control is avoided because enough area under the proposed future developed condition is able to be routed away from the channel (to the Tacoma Power Easement outfall) that the future development does not increase the peaks or durations of the Mason County —Allyn UGA Stormurater Management Plan 52 otak IC \project: \ 30700\ 307( 4 \Reports \ Allyn S\V\fl? Update_ \Final Report\Allyn Swi\[ Rcport.doc Section 6—Hydrologic Modeling and Engineering Continued resulting stormwater flows in the channel above those of existing conditions. Under existing conditions subbasins EE010 and EE015 (45.3 acres combined) are tributary to the unnamed creek. Under future conditions, EF015 (18.2 acres) flows into the creek channel, and HF010 is re-routed to flow to the south and discharge into North Bay through one of the culvers that passes under SR3. Water quality treatment is required in this basin prior to discharge to the stream channel. Treatment may be provided in a regional basin -wide facility, such as a wetpond or constructed wetland located adjacent to the channel, or alternately by onsite techniques. Future potential sites for such a facility are shown in Figure 6-5. Collection and conveyance systems will also be needed in this subbasin, as future development occurs. Water quality treatment requirements for ultimate buildout of the Unnamed Creek Subbasin total 76,200 cubic feet. Note that future conveyance for this subbasin has not been sized and a cost estimate has not been prepared.) Stormwater Management Area #2 Sherwood Creek SWMA (Subbasins # SE 010, 020, and 030) Flow control and water quality treatment are required in the two Sherwood Creek subbasins prior to the discharge of stormwater into Sherwood Creek. Regional detention facilities were considered in these subbasins however, they are not recommended due to the dispersed type of development and unfavorable environmental conditions (i.e. unfavorable soils and steep slopes). One potential site for regional treatment is this subbasin is shown in Figure 6-5. Much of the area in these subbasins is constrained by steep slopes that Lappear to make some parcels undevelopable. Other parcels are only developable in a manner that will not increase the existing impervious area currently existing on the parcel. Because of this, parcel -by -parcel type of onsite flow control and water quahty treatment for new development are recommended. Mason County UGA Stormwater Management Plan 53 otak K:\project\30700\30784\Reports\ Allyn SWTvIP Update \Final Report\Allyn S\\C:\C Report.doc Section 6 Hydrologic Modeling and Engineering Continued Photo 9 Sherwood Creek: Photo taken from SR3 Looking Upstream. The hydraulic analysis (10-acre basin) produced unit rate control and water quality requirements for the two land uses zoned for the Sherwood Creek subbasins. The results of this analysis are listed below in Table 6-4. Table 6-4--East Drainage Basin: Hydraulic Sherwood Creek Basins Results Long -Term Option Land Use Zoning R-1 H.0 Percent Impervious 40°- o 80`i0 Rate ControlDetention Volume (cf/ac) 14,900 22,900 * I.;nhanccd stortnwater treatment required Pond Bottom (sflac) 4,300 6,600 Water Quality Basic Wetpond (cflac) 4,400 6,100* As expected, the required volume to treat Highway Commercial (IIC) development is greater than the required volume to treat Residential (R-1), because highway Commercial is allowed to have a greater percentage of property covered by impervious area. Onsite water quality Alason Lonoty Allyn VGA Slorillwater illrana,genreat Plan 54 otak 4<:Aproject\30700\30784\Reports\Allyn S 'N-IP Update. \Final Report\.11lyn Swli Report.doc Section 6—Hydrologic Modeling and Engineering Continued wetponds and constructed wetlands are recommended for these commercial areas because they can also be designed to accommodate the required detention. Howevei, other water quality methods are also acceptable. Alternative LID water quality treatment options are provided in Appendix E. Stormwater Management Area #3—Shoreline SWMA (Subbasins #EF 090 and EF 1 00) Per the 2005 Ecology Manual, direct discharge is allowed to North Bay without the need for onsite or regional detention. Thus, runoff from the Shoreline SWMA can drain directly into North Bay, without detention, however, water quality treatment is required for any new development. Because of the narrow shape of the Shoreline basin, regional basin -wide treatment is not an option, however, onsite water quality treatment is required and is recommended The treatment requirement varies with the type of development being proposed. Table 6-6 shows how water quality requirements vary with the different proposed zonings along the shoreline. (Land use code R-1 represents residential with homes with six homes per acre, VR represents increased residential densities to include apartments and condominiums, and VC represents the increased densities associated with commercial development.) The unit area results, per acre of development, are based on the analysis of a small hypothetical ten -acre basin within each of the land use types. East Drainage Basin: Shoreline Table Water 6-5 Quality Treatment Requirements Long -Term Option Land Use Requirement per Acre of Development Zoning Percent Impervious Wet Pond Volume (CF) Per Acre R-1 40% 4,400 90% 6,500 VR VC 100% 7,000 Recommendation for the Long -Term in the East Drainage Basin: To support ultimate buildout, it is recommended that the County construct the collection/conveyance systems within road rights -of -way, select sites and construct regional Mason County Allyn UG.A Storm/pater Management Plan 55 otak K:\project\30700\3078 I\.Reports\Allyn S\V i\. P Update \ Fit al Report \Allyn S\C \I Report.doc Section 6—Hydrologic Modeling and Engineering Continued water quality treatment facilities, and construct new regional outfalls to convey stormwater runoff into North Bay. Mason County —Allyn UGA Siormwater Management Plan 56 otak K:\project\30700\30784\Reports\Allen SWMP Update \Final Report\Allen S\\ i\t Repot doc Section 7—Stormwater Management Plan Stormwater Management Recommendations West Drainage Basin Short- and Long -Term Strategies Stormwater management with the West Drainage Basin, including planning, design, funding, and construction will remain the responsibility of the LakeLand Village Development Corporation. The County will continue to provide maintenance of existing systems within the County road rights -of -ways. Stormwater Management Recommendations —East Drainage Basin Short -Term Strategy U sing onsite stormwater management techniques, developers in the short-term (i.e. the next six years) are responsible for stormwater planning and design in accordance with County codes and standards. Both conventional and Low Impact Development (LID) techniques are applicable for onsite stormwater management, as local soils allow. Developers will be required to detain and treat stormwater onsite prior to discharge to the existing collection systems and ultimate discharge to North Bay. An inspection of the existing outfalls is recommended to determine their condition and capacity, prior to pursuing this alternative, to confirm the availability of existing culvert/discharge capacity to accommodate anticipated growth over the next six years. Some flow control (i.e. detention on the upstream side of SR3) may be needed over time where/when existing local culvert capacity does not meet future needs, however, these small, local detention facilities have not been included in this short-term capital improvement plan. N o new major capital collection, conveyance, detention, treatment, or discharge facilities have been proposed for the short-term. Within the East Uplands area, the existing lack of drainage easements and public rights -of - way for the road system presents challenges for the County to convey runoff to existing points of discharge (i.e. the series of culverts that pass under SR3 into North Bay). Cooidination with and approval by Washington State Department of Transportation and other property owners will be required Suggested short-term stormwater management strategies for each of the three SWMAs within the East Drainage Basin include the following: East Uplands SWMA: Existing collection, conveyance, and discharge facilities will continue to be used fot new development, directly discharging increased stormwater runoff directly into N orth Bay without detention. New development, however, will be required to treat Mason County —.Allyn UGA Star/ter Management Plan 57 otak K:Aproject\30700\30784\Reports\A]lyn SWA.IP Update\Final Report\Allyn S\VM Report.doc Section 7—Stormwater Management Plan Continued stormwater onsite prior to discharge from the site. No onsite or regional detention is required Shoreline (Including Unnamed Creek Subbasin) SWMA: Similar to the East Uplands SWIVIA, existing collection, conveyance, and discharge facilities will continue to be used for new development; direct discharge into North Bay can continue without detention, however, onsite or regional water quality treatment will be required prior to discharge. Sherwood Creek SWMA: All new development within this subbasin will be required to both detain and treat all new runoff onsite prior to discharge to the creek. Long -Term Strategy Regional water quality treatment facilities are proposed to support future/ultimate development in order to cost-effectively serve all properties within the basin. The use of regional facilities is the preferred approach and design, land acquisition and construction activities are expected to realize `economies of scale". An enhanced collection and conveyance system, leading to four new culverts under SR3, the design and construction of a number of regional water quality treatment facilities is also recommended to accommodate increased future flows. The use of onsite facilities should be used only where appropriate (i.e. in Sherwood and Unnamed Creek drainages). One challenge is that collection and conveyance facilities are normally located within public rights -of -way, which are currently limited in the East Upland area of the Allyn UGA. The Allyn UGA Comprehensive Plan documents the County s desire to acquire more property for Public Open Space that could be used to accommodate public facilities, such as regional detention and water quality treatment facilities. Public Open Spaces, if located near existing and/or proposed outfalls, could potentially be designed to include some of these regional stormwater. facilities. Suggested long-term stormwater management strategies for each of the three SWIVIAs within the East Drainage Basin include the following: East Uplands SWMA: Ditch collection and conveyance system improvements will be needed to convey increased runoff to regional water quality treatment facilities and then to the four, new larger culverts to be constructed under SR3 leading to North Bay. Shoreline (and Unnamed Creek) SWMA: As in the short-term, onsite water quality treatment w ill continue to be required on a per parcel basis as development occurs No onsite or regional detention will be required for development in the future, and no regional water quality treatment is recommended due to the lack of elevation and slope (foi gravity operated systems) and proximity to North Bay. Regional or onsite water quality treatment is suggested for the Unnamed Creek Subbasin. AI risen County —Allyn UGA Stormwater Management Plan 58 otak K:\project\30700\30784\Reports\Allyn S\\.1{P Update \Final Report \Allyn SW_\I Report.doc Section 7—Stormwater Management Plan Continued operated systems) and proximity to North Bay. Regional or onsite water quality treatment is suggested for the Unnamed Creek Subbasin. Sherwood Creek SWMA: As with the short-term strategy, all new development within this subbasin will be required to detain and treat all new runoff onsite prior to discharge to the stream Due to the few number of homes and their location generally next to the stream, no regional detention or water quality treatment facilities have been suggested. Stormwater Management Plan for the Allyn UGA West Drainage Basin The capital improvement program (CIP) for the LakeLand Village Development (West Basin) will be undertaken by the developer. Needed facilities for the alternative development plans are described in Appendix A. The County has little direct involvement or financial responsibilities in the design or construction of the capital drainage projects needed to support the ultimate buildout of the LakeLand Village Development. Stormwater Management Plan for the Allyn UGA East Drainage Basin Within the East Drainage Basin, the County is the lead in designing constructing, and funding needed drainage facilities required to support ultimate development. The stormwater management strategyfor the East Basin has been divided into a short-term (six year) capital facilities plan and a long term (twenty year) plan to support ultimate development. Short -Term Capital Improvement Plan: Six Year Implementation Plan $660,000 The following is a recommended implementation plan for stormwater management in the Allyn UGA over the next six years. It involves a series of coordination inventory, maintenance, property acquisition, and funding activities. No major capital stormwater facilities have been recommended in the short-term because the existing drainage system appears to have the needed capacity to accept additional stormwater runoff as new development occurs. Onsite water quality treatment and detention will continue to be required for new development. Full buildout to the Countys proposed zoning is not anticipated within this time -frame, therefore, these recommendations have been tailored to accommodate the projected level of new development (i.e. 120 homes) that may occur, while the County prepares for additional development in the future. Recommended activities are presented below. he annual and Mason County —Allyn UGA Stormwater Management Plan 59 otak K:\project\30700\30784\Reports\Allyn S\X/Iv1P Update\Final Report\Allyn S\X/ivl Report043007.doc Section 7—Stormwater Management Plan Continued Table 7-I—Allyn SWM Plan: Short Term Project Costs for Six Year CIP Plan Schedule (Year #) Yr Annual I Yr 3-6 Cost ($) Total Activity # Project/Activity Priority -2 Activity #1: Coordination with WSDOT High # 1 Use existing Co. staff. # 1-2 $30,000 $30,000 $60,000 Activity #2• Inventory and Capacity Analysis High Annually $50,000 $50,000 $300,000 Activity HI Culvert Maintenance High Annually $50,000 $50,000 $300,000 Activity #4: Property Acquisition High Begin Yr.1 Use existing Co. staff. Activity #5: Secure Funding (Ongoingprocess) High #1 Use existing Co. staff. Activity #6: Low Impact Development Brochure High Total $110,000 $100,000 $660,000 Hach proposed short-term activity is described below. Activity #I: Coordination with WSDOT (Using existing County staff) Coordinate with WSDOT to establish a regular annual maintenance program for the existing culverts/outfalls. The use of a memorandum of understanding for the continued use and upgrade of these culverts over time may be useful as the area continues to grow. Activity #2. Inventory and Capacity Analysis (Estimate: $60,000, a one-time cost) Determine the capacity and condition of the existing culverts crossing SR3 within the Allyn UGA Depending on the timing and intensity of new development, the County may be able to manage the stormwatei runoff of the next few years using these existing facilities. To verify this assumption, the County should conduct a survey, inventory, and analysis of the existing culverts. Our preliminary analysis (presented in Appendix F) suggests that only eleven percent of the available pipe capacity would be needed to accommodate expected future development over the next six years. The survey of existing culverts should include ditches, storm sewer facilities, culverts, inverts, edge of pavement, and pavement centerline. An accompanying inventory of identified culverts will record blockages as well maintenance and repair/replacement needs so their full conveyance potential can be realized. Remaining culvert life should be established in older to assist facility planning. With the culverts properly inventoried their available capacity should be analyzed to document the excess capacity that may be available to accept runoff from new development. Based on the results of this study the outfall diameters for the foul proposed culverts proposed for the long-term, may be able to be reduced by optimizing the use of the existing system of culverts and outfalls. Mason County —Allyn UG.A Stornrmater Management Plan 60 otak h:\project\30700\30784\Reports\Allyn SWNIP Update. \Final Report\:°111yn S\Vi? [ Report.doc Section 7—Stormwater Management Plan Continued Activity #3. Culvert Maintenance (Annual estimate: $50,000) Remove any blockages and perform maintenance, repairs, and replacements as identified during the above inventory to achieve the full design capacity of existing culverts/outfalls. Activity #4: Property Acquisition (Annual appropriation: $50,000) The stormwater facilities recommended to accommodate ultimate development of the proposed zoning will require the acquisition of new County rights -of -way for new stormwater collection systems, new outfalls, and basin -wide water quality treatment facilities. Currently, the County has limited rights -of -way within the Allyn UGA. This activity begins the incremental process of annually acquiring the rights -of -way needed for both short-term enhancements and long-term ultimate buildout. Activity #5: Secure Funding (Using existing County staff) Identifying and securing the needed funding will take time and should begin within the next one to two years. Acquiring the needed funding will likely be the most critical element of this recommended stormwater management plan for the Allyn UGA. Multiple sources will be needed, including the development of new revenue sources at the County level and the creation of new joint funding opportunities with WSDOT, developers, the business community, the Port of Allyn, and local land owners. Activity #6. Low Impact Development Brochure (Using existing County staff) The preparation and distribution of a brochure describing low impact development techniques for onsite detention and water quality treatment is an inexpensive way for the County to guide new development. It also can be used to provide ideas to local residents for redevelopment to enhance water quality throughout the UGA, as well as prolong the use of the existing culverts under SR3 Long -Term. Capital Improvement Projects for Ultimate Buildout—$15,130,000 Although it is difficult to predict the various drainage alternatives that may present themselves as the Allyn UGA develops, it is clear that additional drainage facilities will be needed for collection and conveyance, as well as detention, treatment, and ultimate discharge to North Bay. To accommodate this future need, six regional stormwater management projects have been proposed to support the ultimate development of the East Drainage Basin of the Allyn UGA. They are composed of a collection and conveyance system in the East Evans Street and East Wade Street subbasins, and the design and construction of four, new, larger culverts and outfalls underneath SR3 (with conveyance along the west shoulder of SR3) that discharge to North Bay. Mason County UG.4 Stormwater Management Plan 61 otak K:\projecA30700\30784\Reports\Allyn S\VMP Update \Final Report \Allpa meld Report.doc Section 7—Stormwater Management Plan Continued As continued development occurs within the Allyn UGA, additional conveyance and discharge systems will be required to accept, convey, and discharge the increased stormwater runoff from new development. It is difficult to predict when and in what order these various facilities will be needed. It is likely that future drainage studies that accompany new land use proposals will determine when, where, and what size these facilities will need to be. Studies to optimize the use of existing facilities and minimize the size of new regional facilities will be undertaken at that time. It is likely that the costs to the County will be reduced by partnering with WSDOT, developers, and local businesses and landowners, and • that the County should aggressively create and pursue these more creative funding options. Recommended capital projects (CIPs) to support ultimate development of the Fast Drainage Basin of the Allyn UGA, have been previously shown in Figure 6-5. The total cost for this long-term plan is estimated to be $15,130,000, as shown in Table 7-2. Table 7-2 Allyn SWM Plan* Long Term Stormwater Project Costs for Ultimate Development Estimated Cost Project ($) 980,000 CIP #1A: East Evans Street Conveyance System. 3,040,000 CIP #1B0 East Wade Street Conveyance System 4,460,000 CIP #2: Evans St. Conveyance, Outfall & WQ Pond(s) 2,780,000 CIP #3: Wade Conveyance, Outfall & WQ Pond(s) 700,000 CIP #4: Kayak Pk. Conveyance, Outfall & WQ Pond(s) 3,170,000 CIP #5: Power Ease Conveyance, Outfall &WQ Pond(s) Total $15,130,000 Does not include the cost of land and easement acquisition. CIP # I A: East Evans Street Conveyance System: $980,000 The Evans Street Conveyance System may be one of the first capital facilities needed to support long-term future development within the Allyn UGA. Additional collection and conveyance will be needed to convey increased stormwater flows to North Bay using the existing culverts under SR3. Most of the new development is expected to locate just upstream and across the street, which will at some point in time exceed the capacity of the existing collection s) stem, which is currently composed mostly of shallow culverts and roadside ditches. Mason Coranty— .Allyn UGA Storma/ ater :Management Plan K:\project\30700\3078d\Reports\Allyn SR'NIP Update\17inal Report \Allyn SWM Report.doc 62 otak Section 7—Stormwater Management Plan Continued CIP #I B: East Wade Street Conveyance System: $ 3,040,000 It is difficult to determine when additional conveyance within the upstream areas of the East Evans Street Outfall will be needed. Very likely it will need to be installed in a phased, piece - by -piece fashion to accommodate future grow th within the subbasin. Because of the limitations of the existing system, it may not take much development before some new collection and conveyance facilities will be needed CIP #2. Evans Street Conveyance, Outfall, and Regional WQ Pond(s)—$4,460,000 The Evans Street Conveyance, Outfall, and Regional Water Quality Treatment Pond(s) will likely be one of the first culvert/outfall projects needing to be built. Most of the new growth over the next six years is expected to occur just upstream, within the drainages on either side of East LakeLand Drive. This level of development will generate increased stormwater flows that will eventually exceed the capacity of the four local existing culverts under SR3, requiring the need for additional conveyance and discharge capacity. Water quality treatment on a regional basis has been proposed CIP #3. Wade Street Conveyance, Outfall, and Regional WQ Pond(s): $2,780,000 Currently the Wade Street drainage area is largely undeveloped with few roads. however, it is currently platted and road rights -of -way have been defined so this area is ready for new development given the right local economic conditions. An extensive system of new conveyance lines have been proposed for this area that will substantially increase the rate and amount of new stormwater that will leach the two existing outfalls under SR3 which currently drain this area As with the Power Easement Conveyance, Outfall, and Regional Water Quality Treatment Pond(s) project, this area would be a good area for the creation of regional facilities and partnering with future developers to reduce County costs. CIP #4. Kayak Park Conveyance, Outfall, and Regional WQ Pond(s) $700,000 The Kayak Park Conveyance, Outfall, and Regional Water Quality Treatment Pond(s) will accept increased flows from the southern portion of the East Basin of the Allyn UGA. It is a relatively small drainage area that is currently served by four culverts under SR3. The need for this capital improvement will be entirely determined by the rate and type of new construction that occurs on the hillsides lust upstream. It is likely to be one of the lower priority regional drainage improvement projects. Cost sharing with new developers is recommended as future development opportunities Mason County Allyn UGA. Storinwoter Management Plan 63 otak h:\project\30700\30784\Reports\Allyn SV :NIP Update \Final Report\All3n SR'\I Repoit.doc Section 7—Stormwater Management Plan Continued allow. CIP #5. Power Easement Conveyance, Outfall, and Regional WQ Pond(s)—$3,170,000 The Power Easement Conveyance, Outfall, and Regional Water Quality Treatment Pond® will accept increased flows from the most northern area of the East Basin of the Allyn UGA. It drains a significant area and comprises almost one third of the entire area within the East Drainage Basin. There are no culverts under SR3 or outfalls to North Bay within this drainage area at the present time. The area is almost entirely forested with few existing roads. Like many of these projects, the need for this capital improvement will be entirely determined by the rate and type of new construction that occurs on the hillsides just upstream. Because there are no major existing drainage facilities at this time, it may not take much new development to require some enhanced drainage facilities within this area of the UGA. This area presents another good opportunity for regional facilities for both detention and water quality treatment, as well as a id partnering with future developers to reduce County costs. Mason County —Allyn UGA Stormier Management Plan 64 otak K:\project\30700\3078 4\Reports\,llltn S\\I{P Update \Final Report\Allyn SWAT Report.doc Section 8 Costs, Schedule and Implementation Costs. How Much Funding is Needed by When? Implementation Priorities and Schedule Determine Revenue Needs Although difficuk to predict, an attempt has been made to identify the priority and timing of future activities and capital projects in order that future revenue needs can be established. Presented in Table 8-1 is an estimate of new revenue which will be needed over what period of time For this analysis, the twenty year planning period has been divided into four planning periods of 6, 4, 5, and 5 years respectively as shown below. Total costs over the twenty year capital planning period are estimated to be $15.1M, as shown in Table 8-1. Average annual costs for each of the four planning periods are $110,000, $1,005,000, $892,000, and $556,000, respectively. The next six years will require the least, $110,000 per yeai. Years 7 through 15 will require approximately $1M per year. And with the deferral of (:IP projects # 4 and # 5 out beyond the twenty year planning process, as described in the footnote to Table 8-1, the annual cost for years 16-20 is about $556,000. Table 8- I Financial Plan for the Allyn Stormwater Management Plan Annualized Revenue Needs Over the Twenty Year Planning Period ($ in Cost I ,000s) Schedule (yrsl$1000s) Relative Priority for Implementation 1-6 7-10 1 1- 15 16-20 Short -Term Activities: $660 $660 Long-term Activities: + CIP # 1A: E Evans Collection $980 $980 + CIP # 1B• E Wade Collection $3,040 $3,040 + CIP # 2: Evans St Culvert/Outfall $4,460 $4,460 $2,780 $2,780 + CIP # 3: Wade St Culvert/Outfall + CIP # 4: Kayak Pk Culvert/Outfall* $700 + CIP # 5: Power Ea Culvert/Outfall $3,170 Total: $15,130 $660 $4,020. $4,460 $2,780 Annual Estimate: $110 $1,005 $ 892 $556 ` It is difficult to estimate when ultimate buildout will occur. The most northern and southern ends of the Allyn UGA within the East Drainage Basin will likely be the last to be developed. As a result, from a fmincial planning perspective, the funding for these two culvert/outfall projects has been postponed until After the twenty year capital planning period. Thus, projects (:FP # 4 and # 5 have been deferred beyond the 20 year planning period.. Mason County —Allyn UGA Stormwater Management Plan 65 otak K:\project\30700\30784\Reports\Allyn SWMP Update\Final Report\Allyn S\XNI Report043007.doc Section 8—Costs, Schedule and Implementation Continued Potential Sources of Funding At this point in time, the County is unsure how they will raise the funds needed to support and implement this proposed Stormwater Management Plan for the Allyn UGA. There are several financial options being considered. These considerations have led to the conclusion that multiple sources of funding will be needed. Funding sources that are currently being considered include: • Formation of a Local Drainage/StormzxaterIirprozenrnt District, which would have an annual assessment often based on assessed property value, or some other equitable means of establishing value and/or benefit to the various rate payers. • Real Estate Excise Tax (REE 7) funding, which currently amounts to about $1M per year, and is currently being used to pay for a number of capital projects throughout the County. • Public Sector Funding such as grants and low interest loans from the State (Ecology or the Puget Sound Action Team) or federal government, including federal 319 Water Quality Grants, and the State Public Works Trust Fund and State Revolving Fund. • Formation of a Stormuater Utility(County-wcle), where a monthly service fee is assessed to rate payers, often based on the amount of impervious area per parcel, and an incremental portion could be allocated back to the rate payers within the Allyn UGA. • SytemDezeloprrrnt Charges, where any person moving into an upstream drainage area would be required to pay for a portion of the downstream collection, conveyance, detention, treatment, and outfall facilities that may be needed to support continued development within the drainage basin. • SEPA Mitigation Funds, which would be established on a per development basis, as a project enters and is ultimately approved through the State SEPA review process. • Partnering -with prospective developers and land owners, which is especially effective in establishing funding for larger regional drainage facilities. • Other potential, but less likely sources of funding, include: The County General Fund - The County Road Fund - Cost Sharing with WSDOT • Any potential future read, park, or utility project could also include some funding for making localized drainage improvements, as defined in advance though this stormwater planning process. From this list of eleven potential sources of funding, the most likely sources of new future funding in relative order of priority are the following: 1. Partnering with developers. 2. SEPA mitigation funding. Mason County A llyn UGA Stormwater Management Plan 66 otak K:\project\30700\30784\Reports\Allyn S\XTIvIP Update \Final Report\Allyn S\XII Report043007.doc Section 8 Costs, Schedule and Implementation Continued 3. Periodic appropriations from REET funding. 4. Public sector funding (grants and loans). 5. Annual CEP stipends from a county -wide stormwater utility. 6. Partial, periodic funding from future road, park, or utility projects. It is difficult to estimate how much revenue could be raised by each of these preferred potential funding sources, over what period of time, in order to support the above annualized Financial Plan. However, being pnmarily driven by future growth, it is recommended that every effort be made to optimize the amount of new revenue from prospective developers, and then augment the remaining funding needed from REET and public sector funding, as opportunities allow. Future partnering with developers, landowners, WSDOT, and the Port of Allyn should assist the County in sharing these regional growth related costs and maintaining the steady, continuous development of the drainage infrastructure needed to support growth throughout the Allyn UGA. Stormwater Management and Funding Strategy Creation of Practical Approaches to Reduce/Share Costs The stormwater capital facilities plan proposed for the Allyn UGA has been designed according to the 2005 Ecology Manual. It is based on the latest stormwater modeling and management technology and protocols, and is technically sound. However, from a planning perspective the proposed stormwater management plan must be realistic, equitable, and able to be funded and implemented at the local level. The proposed Short -Tenn OP Plan totaling $660,000 and averaging $110,000 over each of the next six years is a reasonable level of funding that matches the local drainage needs, as well as the County's and community's ability to pay. The proposed Long -Term OP Plan totaling $15.1M and averaging about $1M per year for years seven through twenty (ultimate buildout), on the other hand, is a significant capital investment. For the County and local community to generate this type of new revenue will be very challenging, and may limit the effectiveness and usefulness of the proposed Allyn SWM Plan. It is for these reasons that an alternative drainage management and funding strategy is being proposed for the long-term, ultimate buildout of the Allyn UGA. It is based on the following planning level costimpact analysis. Mason County —A llyn UGA Stormwater Management Plan 67 otak K:\project\30700\30784\Reports\Allyn S\KRvIP Update \Final Repoli\Allyn SWIVI Report043007.doc Section 8 Costs, Schedule and Implementation Continued Cost Impact Analysis: Optimization of Available Funds The following cost impact analysis evaluates the relative costs and benefits of the conveyance, detention, water quality treatment, and outfall facilities proposed in the long- term CIP Plan for the Allyn UGA. Relative costs for each type of capital facility are presented in Table 8-2 Different management approaches are considered and discussed to cut costs, create new revenue, and/or share costs more equitablywith those causing the need for and/or benefiting from the various proposed regional drainage facilities. Table 8-2 Long Term CIP - Cost Impact Analysis Project Name Conveyance Detention WQ Treatmt Outfall Total CIP # 1A EEvans $980,000 -0- -0 -0 $980,000 Convey 1B EWade Convey $3,040,000 -0 -0 -0 $3,040,00 2 Evans St. $500,000 -0 $3,630,000 $330,000 $4,460,000 3 Wade St. $640,000 -0 $1,910,000 $230,000 $2,780,000 4 Kayak Pk. $10,000 -0 $540,000 $150,000 $700,000 5 Power Ease. $60,000 -0 $2,590,000 $520,000 $3,170,000 Total $5,230,000 -0 $8,670,000 $1,230,000 $15,130,000 In general, the proposed management strategy is based upon the following criteria: • The County should not take on any additional drainage responsibilities other than those required to be in compliance with the 2005 Ecology Manual and the Puget Sound Water Quality Management Plan (2000) and the 2005-07 Update. • New development should pay for its fair share of the new, required, onsite and regional drainage facilities. • There are currently no major water quality, flooding or maintenance problems associated with the current drainage system within the Allyn UGA. That is, there are no major outstanding capital drainage needs or associated financial obligations that currently exist • The County is currently not required to retrofit existing development retroactively for detention or water quality treatment, thus it is not requiring that existing residential or commercial development retrofit their respective sites. • A relative cost-effective stourrwater management system and CIP and maintenance plan is important to the existing and future Allyn community in terms of quality of life and its ability to attract and sustain a steady and reasonable level of economic development. Mason County Allyn UGA Stormwater Management Plan 68 otak K:\project\30700\30784\Reports\Allyn S\X/MMSP Update \F nal Report\Allyn SReport043007.doc Section 8—Costs, Schedule and Implementation Continued ® There is a net regional benefit to the community of Allyn, as well as to Mason County, for supporting and sustaining a healthy economy and sustained level of new development withm the Allyn UGA, although it is difficult to put a price or value on this sustained level of economic development. Collection/Conveyance Facilities—$5,230,000. Proposed CIP: While each of the six CIP projects contain some level funding to enhance local collection and conveyance systems, CDs # 1A and # 1B (costing over $4M), are entirely dedicated to the construction of an extensive new collection/conveyance system within the drainage basins on either side of East. LakeLand Dnve and East Wade Street. These areas are expected to see the most of the growth over the next 5-10 years. Managenvnt Recon Rndatioiv Developers should pay for most if not all of these regional downstream drainage conveyance costs. the County will continue to pay for enhancements to the conveyance system as it expands the system of roads within the growing UGA. In -pact on County S WM CIP Budget: Reduces County CTP needs by about $2.62M over the next 20 years. Detention Facilities—$0 Proposed CIP: No regional detention facilities have been proposed with the SWM CIP Plan for the Allyn UGA at this time because almost all new development can discharge increased stormwater flows directly into North Bay without any onsite or regional detention. The exceptions to this are those developments that will be discharging into local streams, such as those new developments within the Sherwood and Unnamed Creek sub -basins. Anal)szs• Each new development should locate any needed detention onsite and should be solely responsible for its cost. The County is not responsible for these types of onsite drainage systems. ManagenentRecorrmmndation° Developers pay for required onsite detention systems. Impact on County S WM CIP Budget: None. Regional Water Quality Treatment Facilities $8,670,000 Proposed CIP: Each of the four major drainage projects proposed, C1P projects # 2-# 5, have included funding for the design and construction of new regional water quality treatment facilities. These funds cunentlytotal $8.67M and do not include the cost of land or of the Mason County —Allyn UGA Stormwater Management Plan 69 otak K:\project\30700\30784\Reports\Alyn SWMP Update\Final Report\Allyn SWM Report043007.doc Section 8—Costs, Schedule and Implementation Continued easements that will be required for construction, which could double the required funding needed. Management Recorrmvndation° Providing regional water quality treatment, while attractive to the County, would be a challenge because the County currently does not have the needed funding for the upfront costs, and there are numerous logistical issues associated with the County buying land and building these facilities in advance of new development. This is particularly true since the rate of development in the Allyn UGA, while steady, has been rather slow and widely distributed throughout the UGA. At this point in time, without a designated source of funding, it is suggested that the County not develop any regional water quality treatment facilities on its own. Rather, all water quality treatment should be required to be established on -site, for each new individual development. If a developer comes in with a large enough development, it may be possible to build one or two of these regional facilities, with the County contributing to a small portion of the costs. Cost sharing with the business community and Port is also possible. Impact on SWM CIP Budget: Saves the County approximately $8.67M. Outfall Facilities—$1,230,000 Proposed CIP: One of the most critical needs of the Allyn SWM Plan is the ability to pass increased stormwater from new development under SR3 and directly into North Bay. The eleven existing culverts seem to be doing a good job for the moment, as the Short -Term Activity # 2: Culvert Inventory and Analysis will confirm. They are expected to be adequate for at least the next six years. However, at some point additional collection and conveyance will be needed to address future flows from new development. A series of four new culverts under SR3 with outfalls to North Bay have been proposed, at a total cost of about $1.23M. (Land, easements, and permitting will also need to be added to these proposed costs.) They are located south of East Steve Place, at the end of East Evans Street, at the end of East Wade Street, and at the end of the Bonneville Power Easement. ManagemvntRecommendation° In light of the eleven culverts that already exist and the high cost of the new additional outfall facilities, every effort needs to be made to reduce future costs by optimizing the use of the eleven existing culverts before any new outfalls are created. More will be known after the completion of Culvert Inventory and Analysis (Short -Term Activity # 2). At that time a more refined design and financial strategy can be developed. For the present, some cost savings can be realized by minimizing the use of pipe and using open channels as much as possible. In the future, building these regional outfall facilities on an as - Mason County Allyn. UGA Stormwater Management Plan 70 otalc K:\project\30700\30784\Reports\Allyn S\VIv P Update\Final Repori\Alllyn SWI I Report043007.doc Section 8—Costs, Schedule and Implementation Continued needed basis and having developers pay for this increased outfall capacity is a reasonable approach. In pact on S WM CTP Budget Saves the County # 1.23M. (Note: Without the n;sults of the Culzert Inzentory and Anal)5is (Short TermA ctizity # 2), it is difficult to assess how large or how mzny future regional outfalls will lr needed Adding in the cost of lancl and required easerrrnts zeill further increase the Si. 23M crest of these proposed facilities. There are a number of technical approaches that could he used to further ref ne the designs and the cysts of these facilities; these mom detailed design studies should be performed upon the con pletion of the Culzert Inzentory and naosis) Summary of Cost Impact Analysis Using the above Cost Impact Analysis the County is able to reduce its long-term CIP costs to $2.61M, as shown in Table 8-3, with developers assuming the balance of the remaining $12.52M. 8-3 Long CIP Cost Impact Analysis Results Table Term Conveyance Detention WQ eatmt Outfall Ti Total CIP $5,230,000 $-0- $8,670,000 $1,230,000 $15,130,000 Total Costs: Impact Analysis: Co. Reductions Cost $2,620,000 $-0- $8,670,000 $1,230,000 $12,520,000 Revised Costs: Co. $2,610,000 $-0- $-0- $-0- $2,610,000 Costs Developer. to $2,620,000 Not Estimated $8,670,000 $1,230,000 $12,520,000 Suggested Alternative Stormwater Management Plan and Funding Strategy Based on the above Cost Impact Analysis, the following Stormwater Management and Funding Strategy is suggested for consideration by the County and the citizens of the Allyn community. The SWM Management Plan and Funding Strategy ale composed of the following recommendations, including refinements to the proposed Long -Term OP Plan for the Allyn UGA: ® Water quality treatment is provided onsite (or regionally) by each new developer. ® Detention is provided onsite by each new developer, where required. ® County pays for some of the new regional collection and conveyance systems that are located within the County road right-of-ways. Construction will occur as the County builds new roads within the UCTA. Mason County —Allyn - UGA Stormwater Management Plan 71 otak K:\project\30700\30784\Reports\Allyn S\X7iiv1P Update\Final Report\Allyn SWM Report043007.doc Section 8—Costs, Schedule and Implementation Continued New regional outfalls will be paid for by developers. Findings and Recommendations In addition to the above financial analysis, which obligates the County to continue to pay for drainage collection and conveyance systems within the Allyn UGA in conjunction with future road projects, the following suggestions are made to ensure that future development. of the drainage infrastructure within the Allyn UGA occurs according to the proposed Stormwater Management Plan. They include the recommendations: 1. To create new and additional sources of rezenue to support CIP design and construction, 2. The establishment of enhanced stormzeater design standards to ensure future development uses the most current design criteria for new drainage related facilities, and 3. An enhanced program to monitor 'neater quality, reduce/eliminate contaminating/polluting sources, and ensure local receiving water quality standards are meet to support the continued rearing and harvesting of shellfish. Each recommendation is further described below. 1. Development of New Revenue for SWM Plan implementation: Funding is critical for the implementation of this Stormwater Management Plan for the Allyn Urban Growth Area (UGA). Six of the most likely sources of new revenue have been listed and evaluated in the above financial analysis. Of those sources, three should be actively pursued and developed to determine feasibility and public acceptance. These include the formation of a stotnrwater utility within the Allyn UGA (although county -wide should also be considered), the development of developer impact fees (sometimes called system development charges) to help support the new capital projects (both conveyance and outfalls) caused by growth, and the pursuit of grants, loans, and other stipends from the State and other funding sources. Similar to the continued impacts of growth being addressed in this SWM Plan for the Allyn UGA, the County should form a stormwater utility within all heavily developed and rapidly developing areas of the County, based on clezelopnrnt density, in order to help fund growing stormwater and water quality management needs throughout the County and address regulatory compliance related responsibilities. 2. Creation and Adoption of New SWM Design Criteria for the Allyn UGA: To be consistent with the current regulatory requirements, including the Puget Sound Water Quality Management Plan (2005-2007) and the State's new General NPDES II Permit for Municipal Stormwater rn Westem Washington (1-17-07), this Allyn SWM Plan has been Mason County —A llyn UGA Stormwater Management Plan 72 K:\project\30700\30784\Reports\Allyn SWMP Update\Final Report\Allyn SWM Repot043007.doc otak Section 8—Costs, Schedule and Implementation Continued developed using the Ecology 2005 Stonuwater Management (S` Manual for Western Washington. The County is currently using stormwater design criteria from the Ecology 1992 Stormwater Design Manual. For this proposed Allyn SWM Plan to be effectively implemented, and equitably funded, it is critical that the County adopt the Ecology 2005 SWM design criteria for use in the Eastern Basin of the Allyn in order to ensure local water quality needs are met, and that all future development builds new stormwater facilities according to existing State and federal stormwater requirements Adopting the 2005 Manual would allow the County to require and enforce the requirement that all new developers provide on -site water quality treatment, as suggested in the proposed SWM Plan for the Allyn UGA. 3. Design and Establish a Water Quality Monitoring/Enhancement Program: The County should design, set up, fund, and implement a pro -active stormwater monitoring program aimed at identifying and eliminating the sources of water quality contamination within North Bay, especially those that are directly attributable to the Allyn UGA. 'fins program needs to be carefully designed and implemented in order to avoid undue costs. The primary focus should be on shellfish rearing areas and areas of water quality TMDL violations. The purchase of staff, equipment, training, and lab services would be involved, along with the need to work cooperatively with violators. A new and dedicated funding source is also needed to support this new initiative. Mason County —Allyn. UGA Stormwater Management Plan 73 ocal< K:\project\30700\30784\Reports\Allyn S\V1vIP Updare\Final Report\Allyn SWIVI Report043007.doc Appendix A—LakeLand Village Stormwater Facility information LAKELAND VILLAGE STORM DRAINAGE REPORT December 6fh, 2006 By: Pat McCullough, PE INTRODUCTION: This report is being prepared at the request of the Mason County Planning Department for submittal to the Washington State Growth Management Board. The purpose of this report is threefold: 1. To describe the existing storm drainage facilities in LakeLand Village. 2. To evaluate conveyance and water quality performance of the existing storm drain system in LakeLand Village. 3. To propose design criteria for the future development of LakeLand Village that complies with the current Mason County storm water ordinance and preserves the water quality of Anderson Lake and Lake Deveraux. (Authors Note: Lake Deveraux can be spelled Lake Devereaux.) EXISTING CONDITIONS: Area Description: LakeLand Village in located on the western boundary of the Allyn Urban Growth Area. The development includes approximately 775 acres of land, of which 649 acres is developed. LakeLand Village is currently approved for a total of 942 residential units. As of December, 2006 approximately 750 residential units have been constructed in the development. The development is served water by the LakeLand Village Water Company. Sewer is provided by Mason County via the North Bay Sewer System. The development includes and 27 hole golf course and numerous other community facilities. Table 1 below presents a time table of the development of the property from 1966 to present. Figures 1 and 2 presents a 2005 the watershed boundaries, areas and topography. 1 d TABLE 1 LAKELAND VILLAGE DEVELOPMENT HISTORY DIVISION NO. 1 2 3 4 5 Generation 1 Golf Course - 9 Holes 6 7 8 9 10 Generation 2 Golf Couse - 9 Holes 11 11A Generation 3 Golf Course - 9 Holes 12-A 12-B Subtotal DATE PLATTED 5/2/1966 7/18/1967 7/24/1967 7/17/1969 4/22/1970 1970 7/27/1970 11 /17/1975 8/27/1979 4/28/1980 1/18/1982 1985 1/10/1985 1 /22/1991 1995 1995`. 2000 NO. OF LIVING UNITS 150 27 10 37 115 88 84 14 21 19 134 28 137 78 REMARKS Lot 151 - Lake Lot 116 - Canal Lot 89 - Clubhouse Lot 41- Dam Lots A Tennis Lot B Stables Lot 136 Pro Shop, Lot 135 Condo Site Phase 1 Phase 2 942 Living Units 94 Condominiums 848 Residential Lots 2 • • • ® \ , Y Mp ,z \� '' t : rut 1 - Ke .)\ \sees ƒot.wm�» : • : \ FIGURE 1; LAKELAND VILLAGE WATERSHEDS 3 FIGURE 2: LAKELAND VILLAGE WATERSHED AND 5' COUNTOURS LakeLand Village Soils: The surface soils of the Anderson Lake Watershed and the Southern portion of the Lake Dever ux watershed are shown in Figures 3 and Figures 4. This information waste ken from a site specific soils study done by the Soil Conservation Service (SCS) in 1959 prior to Construction of the dam. A description of these saltypes taken from the SCS report is asfollows: 4 Norma Silt Loam: A deep basin soil of glacial origin that has a dark colored silt loam surface high in organic matter over stratified layers of porous gravels and sands, silt lenses and compacted clay and sand layers. This moderately high fertile soil has a high water table and n eeds drainage for maximum crop production. Norma Silt Loam is a Class D soil. Alderwood Gravelly Sandy Loam. A glacial till upland soil having a brown surface over a cemented gray hardpan that begins at about 24 inches. This gravelly, droughty infertile soil is best adapted to tree growing. Alderwood Gravelly Sandy Loam is Class C soil. The upper 2 to 4 feet is typically free draining in its undisturbed state and readily absorbs rain water S inclair Shotty Loam. A glacial till upland soil having a shotty, grayish - brown acid surface over a cemented gray hardpan that begins at about 28 inches. This low fertility soil needs drainage for the best crop production and is excellent for growing trees Sinclair Shotty Loam is a Class C soil. Everett Gravelly Sandy Loam. These are excessively drained pale - brown gravelly soils developed upon loose, porous glacial drift and o utwash gravels at about 18 inches in depth. These shallow, gravelly droughty, low fertility soils are best adapted to Christmas tree growing. Everett Gravelly Sandy Loam is a Class A soil. It is free draining and can infiltrate over 20 inches of water an hour. Everett Gravelly Loamy Sand: These are excessively drained, coarse textured, gravelly terrace and upland soils with loose gray gravels and sands beginning at about 12 inches in depth. These shallow, gravelly, very drought, low fertility soils are best adapted for Christmas tree growing. Everett Gravelly Loamy Sand is a Class A or B soil. O rcas Peat, shallow: An organic soil composed mostly of sphagnum moss. This low fertility peat is unfit for agricultural use. Orcas Peat, shallow is class D soil. Mukilteo Peat An organic soil composed largely of remains of sedges and coarse water -tolerated grasses. It occupies very poorly drained basins which remain very wet throughout most of the year unless artificial drainage is furnished. Depth to mineral substratum is over 24 inches. Mukilteo Peat is a class D soil. S emiahmoo Muck A black colored muck soil developed from well decomposed sedge and water plant remains. Depth to gravelly substrata is over 36 inches. Artificial drainage is needed for best crop production. Semiahmoo Muck is a class D soil. 5 The Orcas Peat, Semiahmoo Muck, and Mukilteo Peat soils are typically classified as hydric soils. They are shown in Figures 3 and 4 and predominate under and around Anderson Lake, the golf course ponds and near Lake Deveraux. In 1991 through 2005 over 180 soil test pits have been dug in LakeLand Village for the purpose of classifying the surface soils for septic systems These soil log tests have verified the SCS soil survey results. FIGURE 3: SURFACE SOILS IN THE NORTH END OF THE LAKLAND VILLAGE DRAINAGE BASIN 6 !Sta� iMll�lllllllli/j�� IRMI►,� I►u Elifintis FIGURE 4: SURFACE SOILS N THE SOUTH END OF THE LAKELAND VILLAGE DRAINAGE BASIN 7 LakeLand Village Drainage Basin Hydrology: The LakeLand Village development drains to three drainages. 525.5 acres of the development drains south to Anderson Lake which drains into Anderson Creek. 64.5 acres of the development drains directly into Anderson Creek. 121.6 acres drains north to Lake Deveraux. 63.4 acres drains to the east to the town of Allyn The easterly and southerly flowing drainages flow to Case Inlet in Puget Sound. The northerly flowing drainages drain to Lake Deveraux and down Deveraux Creek to Hood Canal. Figure 5 further illustrates the LakeLand Village Drainage Basins. Figure 5 also includes the area of each drainage basin Deveraux Drainages 1 through 4 north to Lake Deveraux, The Farm Basin, Rock Creek, Golf Course, Early Lakeland Village, Railroad Drainage, and Lake Basins flow to Anderson Lake. The Anderson Creek No. 1 and No. 2 drainages flow directly into Anderson Creek and Allyn No. 1 through No. 4 drainages flow east down the hill to the down of Allyn Several of the drainage basins were further divided into sub drainage basins to facilitate hydraulic modeling of the watersheds. 8 rt ,, "n tau. • • ....`�. .�«:w*67 FIGURE 5: LAKELAND VILLAGE WATERSHEDS AND DETENTION POND LOCATIONS Existing Drainage Facilities: The drainage facilities in Lakeland Village have been constructed over the last 40 years by Anderson and Sons, the Lakeland Village owner and developer. Until 1992 there were no drainage regulations in Mason County other then those needed to protect the roadways. The first designed storm water detention ponds were installed as part of Division 12 in 1995 through 2002. However, the developer should be applauded for developing a storm water treatment, storage, and 9 treatment system that exceeds all the current standards set forth in the 2005 Western Washington Hydraulics Manual They began in 1960 by constructing Anderson Lake is a very effective at reducing the rate of storm flow in the unnamed outlet stream and; subsequently in Sherwood Creek. The lake will store 230 acre feet of water before it overflows the crest of the dam. Later revisions to the outlet weir in the auxiliary spillway increased the storage capacity of the lake by 45 acre feet and substantially reduced down stream flow. Anderson Lake was formed by the construction of a 21 foot high earthen dam at the outlet of a natural wetland bog that was fed by springs which flow continuously at the rate of 160 gallons per minute. The dam was designed by the United States Soil Conservation Service (SCS) in 1964. A pictorial representation of the Anderson Lake darn is shown in Figure 6. Bob and Don Anderson built the dam with the assistance of the SCS and the close inspection of professional civil and soils engineers. They report that the key under the upper embankment of the dam extendsl8 feet down into a hard clay. material 4�=t ,;:, .Hdttakr• •s . ^` '\' GATE �•t •E vras' snit lXPENYithe GORE WTyeY »»ENCN..: PElm0115- rat:ARAIN• (Seir [Ai FIGURE 6. TYPICAL SMALL DAM The Anderson Lake dam is regularly inspected by the Dam Safety Division of the Department of Ecology. A detailed inspection report was published on August 10, 1990 which completely updated the structural analysis of the dam and the hydraulic analysis of the watershed. The outlet of the lake is controlled by a box -like weir structure with a one foot notch in the front. (See Figure 6) As the water in the lake rises it reaches the top of the notch and flows over the three sides of the weir box. When the level of the lake reaches one foot over the weir box, the dual 36 inch culverts in Westlake Drive begin to control how much water can flow out of the lake. As the Lake level reaches 2.4 feet over the weir box, the storm water will begin to flow down the road side ditches in Westlake Drive. At a lake level of 2.75 feet over the top of the weir box the storm water begins to overflow Westlake Drive. The November 24, 1990 storm dumped 6.1 inches of rain on 10 the watershed during a 24 hour period. The flows into the lake reached 266 (120,000 gallons per minute) cubic feet per second during the peak period of storm. The flow out of the lake reached approximately 123 cubic feet per second and the level of the water at the twin 36 inch culverts on Westlake Drive was just below the top of the headwall. (Elev. 104.0 on the assumed datum) A graphical representation of proceeding discussion is shown in Figure 8 which is the Anderson Lake Auxiliary Spillway stage discharge curve developed by the Dam Safety and amended to show the 100 year flood flow computed by the author. ' $r FIGURE 7: ANDERSON LAKE OUTLET WEIR BOX SS M a OCAL L.EV•T 109.00 108.00 107.00 106.00 105.00 104.00 103.00 102.00 101.00 LAKE ANDERSON SPILLWAY DISCHARGE LVATION 107.5 = THE CREST ELEVATION OF ANDERSON DAM H EVELOPM EL. 103 -TOP OF NOTCH IN WIER BOX 0 100 200 300 400 500 600 FLOW IN CUBIC FEET PER SECOND 700 800 900 FIGURE 8: ANDERSON LAKE SPILLWAY STAGE DISCHARGE CURVE The majority of the storm drainage in Lakeland Village is conveyed using open ditches. Most of the open ditches over 4% to 5% grade have rock check dams or are lined with quarry spalls to prevent erosion. This open ditch system provides a filtering and runoff infiltration function. 11 Figures 15 and 16 represent the inventory of drainage fixtures that the author made in December 2006. There are a total of 10 detention ponds and 12 water quality ponds in the LakeLand Village storm water conveyance, treatment and storage system. All the detention ponds are a combination detention pond and wet pond. The outlet structures for Ponds 4, 7 and 9 are culverts behind railroad or road fills. All the other outlet structures are risers with or without orifices and overflow weirs. (See Figures 9 through 14) The total area of water quality ponds is 5.3 acres not counting the 45 acre Anderson Lake. If Anderson Lake is included the area of water quality treatment increases to 50.3 acres or 9.6% of the Anderson Lake Watershed. There are 14.62 acres of DetentionNVetpond Ponds that create approximately 30 acre feet of detention storage not counting Anderson Lake (230 acre feet). • • `fL - :%:4: LL_• .it..,..t..__.,•"etia. FIGURE 9: DEVERAUX —POND 8 aiq ' r-IV „4: i-^'u^r�i?mot:.......,....•3a 'C .......... :C" • Xt... : -... ^'......':SY"agirtaCw.»-taw_. L'iit "_y'... • ..r• 9. FIGURE 11: ROCKY CREEK POND 2 'r t - -==_'_ = �,3>a..n x...:.r .::s-:cue} r:' y;:� F::^.•';T:.:n:::_• '=• c= •1s;w :: ;;: i.. r v_a'....nufiz T wr,; •••arr.,- a .x1 ::=-f st^i:......_�...:':i _'M�,7.:»»..,w:- °y'�.•^v:.--:�Y _ •k.,: ram ' ••• r�-=:?cir.::i:_ ^ i ; z:: =ii? - _ _ _ _ - - :ti: - • " - . e - �! FIGURE 13: ROCKY CREEK POND 6 • IV FIGURE 10: POND 8 OVERFLOW DIKE FoL ' sn,.•Tltl _- _ .+,r ::.R'w!"fi" . h l,N S` S^ •. - .................. So _ SvM- _ mo-a+C :! 'ce::ua. ... .... :3-m ayi FIGURE 12: ROCKY CREEK POND 10 C2dthew 0 FIGURE 14: ROCKY CREEK 12 FIGURE 15: NORTH DRAINAGE FACILITIES INVENTOR WITH DRAINAGE SUBBASINS. 13 FIGURE 16: SOUTH DRAINAGE FACILITIES INVENTOR WITH DRAINAGE SUBBASINS. 14 A major goal of the water quality treatment design.criteria for the Anderson Lake and Lake Deveraux storm drainage systems was to maintain a very low concentration of phosphorus in the storm water entering the lakes. In the LakeLand Village EIS a goal of 19 micro grams per liter of phosphorus was established as a goal for maintaining the pristine character of the lakes. Anderson Lake is tested twice a year for the following parameters: Anderson Lake: Mid Lake Station Total Nitrogen Total Phosphorus Chlorophyll A Temperature and Dissolved Oxygen Fecal Coliform Over the last 3 years Phosphate levels have averaged 15 micro grams per liter. This level of phosphorus concentration puts Anderson Lake in the Oligotrophic category. See Table 3 Below. The storm water that flows to Lake Deveraux flows to and through Pond 8 which is located in the northwest corner of the LakeLand Village development. Pond 8 has been monitored for the same parameters as Anderson Lake for the last 10 years. The phosphorus levels in the outlet of Pond 8 have been about the same or lower then those in Anderson Lake. Table 2 summarizes the condition of Anderson Lake and Deveraux Lake. 15 TABLE 2 CURRENT CONDITIONS OF ANDERSON LAKE AND LAKE DEVEREAUX PHYSICAL DATA Lake Area Lake Volume Mean Depth Maximum Depth S horeline Length Bottom Slope Bottom Geology Inflow Groundwater Runoff Direct Rainfall Outflow Evaporation S eepage S herwood Creek CHEMICAL DATA ANDERSON LAKE 44 Acres 370 Acre Feet 8.4 Feet 16 Feet (Near Dam) 12,244 Feet 2% to Flat on Bottom Sedimentary/Muck 338 Acre Feet 475 Acres Feet (Ave) 201 Acre Feet (Ave) 110 Acre Feet N egligible 904 Acre Feet LAKE DEVEREAUX 94 Acres 1800 Acre Feet 19 Ft. 55 Ft. 13,200 Ft. 2.4% S edimentary/Meta. High Flow/Unknown 933 Acre Ft. 431 Acre Ft.. 235 Acre Ft. High/Unknown U nnamed Creek Sample Time/Site = Summer at Surface S ecchl Disk (Visibility) Dissolved Oxygen Total Nitrite Total Nitrate Total Amonia Total Phosphorus Ortho Phosphate Chlorophyll A Water Temperature Fecal Coliform 12 to 16 Feet S aturation/Unstratified 0.001 mg/I 0.011 mg/I 0.020 mgll 0.017 mgll 0.006 mg/I 1 mg/Cubic M 33-75 Deg. Far 5 -10 col/100 ml 21 Ft S aturated/Stratified 0.00 mgll 0.00 mgll 0.05 mg/I .004 mg/I 0.002 mg/1 U nknown 33-75 Deg. Far 3 co1/100 ml 16 TABLE 3 LAKE CLASSIFICATION BASED ON ANNUAL MEAN VALUES OF TOTAL PHOSPHORUS AND WATER CLARITY (Secchi Disk) Units are Micrograms/Liter and Feet Based on a Study of 200 Lakes by Vollenweider Trophic Status OLIGOTROPHIC ESOTROPHIC EUTROPHIC iYPEREUTROPHIC Parameter Total Phosphorus Mean 8 Range 3 - 18 Shecchi Disk (Ft, Mean 30 Range 17 - 56 27 11 - 96 84 16 - 386 13 8 5-27 HYDRAULIC COMPUTER ANALAYSIS 750-1200 3-24 1.5-1.8 In the last week of November and the first week of December 2006 the author visually surveyed all the drainage facilities in the LakeLand Village watershed in order to develop an As -Built computer model of the existing storm drainage system (Note the November 2006 was the wettest month in recorded history for this area ) My first observation was that the entire LakeLand Village storm drainage system preformed extremely well during November. There were no flooding or erosion issues in the watersheds in the month of November 2006 or during two previous storm events that approached the 100 year storm event magnitude in the last 10 years. Several changes to the system design and previously existing facilities were noted: 1. The Lake Deveraux-1 Drainage Sub Basin has increased from 71 acres to 134 acres because of piping installed in the Generation 3 Golf Course. 2. 18.4 acres of golf course and residential drainage that was designed to be directed to Farm Pond 3 (See Figures 5 and 9) flows into the drainage below Farm Pond 3. The developer is about to construct Division 14 in this drainage. The storm drainage conveyance system to the Farm Pond 3 in the Farm Pond Drainage will be expanded to include the undeveloped lands in the drainage basin. The storm water conveyance system in the proposed Division 14 will direct this storm runoff to the Farm Pond as originally planned 3. The outflow piping from Pond 7 which is the last detention pond in the Rock Creek Drainage was changed from 2 18" CMP Culverts to 3 18' ADS Culverts. This change was made by Mason County to eliminate the roadway overflow from Pond 7 4. Mason County has replaced two 12" CMP culverts in Old Ranch Road in the Golf Course drainage basin with 18" CMP culverts. This change resolved a local flooding problem for downstream property owners. The existing storm drainage system for LakeLand Village was computer modeled using StormShed 2G developed by Engenious Systems of Seattle, Washington and the Western Washington Hydraulic Model 3 (WWHM — Version 3). An earlier version of the StormShed 2G model was used to design the storm drainage system for Division 12 in 1991 - 1993. The StormShed 2G model is an `event" model that applies 17 a 24 hour storm of various recurrence intervals to the landscape and then calculates the flows and volume of storm water runoff. The results of the StormShed 2G modeling is shown below in Table 4. TABLE 4 1 AS -BUILT FLOW RATES FOR THE LAKELAND VILLAGE DRAINAGE BASINS AS AND PONDS OF 12-06-06 IN Cubic Feet per Second (CFS) 14 Detention Basin or Wet- WQ 2 yr 10 yr 25 yr 100 yr Built As 100 Completed yr Design in BASIN Pond 1991 Pond1 1.8279 4.6635 9.2338 11.547 15.5656 29.23 Rock Creek Pond2 5.795 11.1553 23.4551 29 2865 39.8378 39.8 Rock Creek Panda 1.2512 3.1848 5.8093 6.8447 8.196 23.85 Farm Drainage Pond4 16.9204 27.9856 39.5828 44.0002 61.493 26.1 Farm Drainage Ponds 10.0778 18.5481 29.7927 30.6658 32.1086 55.26 Golf Course Drainage Pond° 1.9863 4.7 9.4 11.9 16A 26 Rock Drainage Creek Outfall Pond7 11 2576 20.7073 50.6572 67,6842 86 69 Golf Course Drainage Outfafl Pond 8 16.7 26.4 42.7 51.6 67.4 40.15 Deveraux Lake Pond10 5.0574 11.4277 25.5079 31.2779 40 6616 New Pond Mid Above Rock Creek = Pond 2 ELLV-1 5.8747 9.4951 14.7298 17.2495 21.497 No Change Early LLV ELLV-2 4.0333 6.5194 10.1141 11.8444 14.7613 No Change Early LLV ELLV-3 3.1976 5.1682 8.0175 9.389 11.7009 No Change Early LLV ELLV-4 5.7259 9.2547 14.3569 16.8128 20.9528 No Change Early LLV RailRoadPond 5.9825 9.9989 14.8124 16.978 20.3991 25.25 Existing Pond LakeAnderson 7.9562 13.5563 61.0576 81.5075 102.1243 124.4 Outfall Anderson to Creek A review of the As -Built flows shown in Table 4 verses the 100 year design flows reveals the following- 1. The increased area in the Deveraux 1 drainage basin resulted in an increase of the 100 year outflow from Pond 8 of 27.3 cfs Pond 8 has ample capacity to store the additional runoff. The outflow structure needs to be modified to restore the release rate from Pond 8 to 40 cfs. 2. The change in the outlet structure in Pond 7 of the Rock Creek Drainage resulted in 15 cfs more flow into Anderson Lake from this drainage. No change is recommended because the outflow from Anderson Lake 22.3 cfs less the planned for the 100 year storm. 3. All the 12" culverts in the four Early LakeLand Village drainage basins (ELLV- 1 through 4) that cross Lake Shore Drive need to be replaced with new 24" ADS culverts from the ditch to Anderson Lake. 4, The Farm Creek drainage needs to be modified to comply with the proposed design. The culverts on Lake Shore Drive should be improved by Mason County Department of Public Works. The revisions to the Lake Deveraux-1 basin and the Farm basin should be made by the developer. 18 FUTURE DEVELOPMENT: Approximately 126 acres remains to be developed in LakeLand Village. 46 acres of the undeveloped property lies east of the railroad tracks in the Farm Creek Basin (primarily) and 80 acres lies west of the railroad tracks. 60 acres of the property east of the railroad tracks flows to Lake Deveraux and 20 acres flows to Anderson Lake. Mason County is proposing to allow 6 units per acre development densities for the LakeLand Village The developer has requested that an additional 40 acres be included in the LakeLand Village development and in the Allyn Urban Growth Area. The planning for the future development of LakeLand Village has been underway for several months but is not yet complete. It is important that the future development of LakeLand Village continue to incorporate water quality treatment and storm water detention in the design of storm water facilities Table 5 and Figure 17 presents both the water quality and detention volumes required for the development of the Deveraux-2 drainage sub basin. Two alternatives were considered The 60 acre alternative includes the property currently in the Allyn UGA. The 81 acres alternative includes 21 acres of the property currently outside the Allyn UGA but within the Deveraux — 2 drainage basin. TABLE 5 Density vs Water Qualtu and Detention Volumes for Future Development of Drainage Basin Deveraux - 2 60 Ac Alt 81 Ac Alt Density WQ Vol (acft) Detention (acft) Vol WQ (acft) Vol Detention (acft) Vol 2 7.5 7.722 10 10.257 3 7.9 8.242 10 5 10.972 4 8.3 8.736 11 11.635 6 8.8 9.36 11 7 12.48 19 Storage Volumen Required (acft 14 12 10 8 6 4 2 0 Density vs WQ and Detention Volumes using StormShed2G � ;5 ,..:..1...c—�, , L t_.2 A .. 7 r I 4 e 1 [ \ f...e. c� 1174;9 ;� • (4 n to .( -. -,� ems.+d a ksrea- at w ..4 'fir ,,.14 �; w i 4' AidT r j fi • { VIVA. '3?. I ..t:1 rv' .YR iJ. s ,r 4' rdytti siy� 'fw rr 1 .=si * tier.- ek. 3 4 Density (DU/Ac) 6 -+ - 60 Ac WQ Volume+Sheet3!$A$6 60 Ac Detention Vol (acft) 81 Ac WQ Volume (Acft) 81 Ac Detention Vol (acft) FIGURE 17 Various Low Impact Development (LID) alternatives were evaluated. It was determined that the if the roof and driveway drainage for a 4 unit per acre development in the Deveraux Lake — 2 basin were infiltrated into the ground on site the regional detention pond volume could be reduced by more then 50%. The water quality volume remains about the same. LID should be incorporated into the project at every opportunity, particularly for the residential lot development The proposed drainage facilities for the future development of LakeLand Village should continue to focus on preservation of the water quality of Anderson Lake and Lake Deveraux. 20 Appendix B--Low Impact Development Techniques Appendix B — Low Impact Development Introduction Low Impact Development (LID) is an innovative approach that uses state -of -the art science and technology to manage urban stormwater by working with the hydrological cycle and its associated natural processes. The goal of LID is to design new development or redevelopment in a way that minimizes the impacts of the new impervious surfaces, its surface water runoff, and its non -point sources of pollution sources, in a way that that is consistent with the natural hydrological cycle for the site and the watershed. Using LID, stormwater is managed in a series of small, cost- effective landscape features, similar to existing natural systems, located on each lot rather than being conveyed and managed in larger pond facilities, located at the bottom of the basin. Applicability to Mason County Much of the Mason County Area is largely undeveloped Due to the site -specific nature of LID designs, it is difficult to propose LID site planning on such a large planning level, without conceptual drawings of the proposed development(s). Therefore, the intent of this appendix is to introduce general LID concepts, strategies, and case studies in the form of a brief literature review that may be applied within Mason County. LID designs for surface water management generally do not replace needed surface water management detention and water quality treatment facilities; however, they can be used to reduce the size of these facilities. They are also often used to achieve infiltration, water quality enhancement, aquifer recharge, low flow augmentation, and other natural functions that most conventional surface water management facilities are not normally designed to achieve. LID Goals The primary goal of LID is to mimic the predevelopment site hydrology by using site specific design techniques to store, treat, infiltrate, evaporate, and detain runoff. Using these techniques helps to reduce off site runoff, enhance groundwater recharge, and provide opportunities for improving water quality (Prince George's County, Maryland, 1999). Reported water quality benefits of LID practices are summarized in Table B.1. In general, LID strategies are most effective at removing total suspended solids and metals, followed by biological oxygen demand and bacteria, and finally by the removal of total phosphorous and nitrogen. t otak K:\project\307D0\30784\Reports\Allyn SWIM Update \ Appendices \B_LJD\AppendixII-LID.doc 01112/07 Appendix B - Low Impact Development Continued Table B.1 Reported Pollutant Removal Efficiency of LID Practices Total P Zinc Lead TSS LID Practice Total N BOD Bacteria Bio-retention - 81 43 99 99 - - Dry Well 80-100 40-40 40-60 80-100 80-100 60-80 60-80 Infiltration Trench 80-100 40-60 40-60 80-100 80-100 60-80 60-80 Filter/Buffer Strip 20-100 0-60 0-60 20-100 20-100 0-80 - Vegetated Swale 30-65 10-25 0-15 20-50 20-50 - - Infiltration 90 65 50 80-90 80-90 - - Swale Wet Swale 80 20 40 40-70 40-70 - - Reference #4 and #7 By attempting to maintain the pre -development hydrological balance, LID designs often contribute to other environmental benefits For example, many LLD practices incorporate landscape plantings which create habitat features. Landscaping can also be used to attenuate heating -island effects common in many urban areas. Comparison of Conventional and LID Stormwater Management Approaches The fundamental concept of LID design is to treat rainfall on -site through site and building specific designs. One LID design objective is to capture as much rainfall on site as possible, and then return it to its natural hydrologic pathways (i.e. infiltration and evapotranspiration) or reuse it at the source. On the other hand, conventional stormwater management typically routes water to a pond or infiltration area, often located off site Table B.2 summarizes how conventional stormwater management and LID can be used to alter or preserve the natural hydrologic regime. 2 otak K:\project\30700\30784\Reports\Aliyn SWMP Update \Appendices\B_LID\Appendix$-LID.doc 01/12/07 Appendix B — Low Impact Development Continued Table B.2 Comparison of Conventional and LID Stormwater Management Impacts on the Hydrologic Cycle Conventional LID Hydrologic Parameter Vegetation/Natural typically into drainage not incorporated designs. used development to maintain hydrology pre - Cover Time of Concentration by where possible to shortened, reduced as a -increased approximate predevelopment conditions product of drainage efficiency Runoff Volume increases in runoff volume controlled to predevelopment conditions Peak Discharge controlled design criteria to predeveloped controlled conditions to for predeveloped all storms increased, especially for controlled conditions to for predeveloped all storms Runoff Frequency small, more frequent storms Rainfall Abstractions large reduction in all maintained predevelopment to conditions elements (Interception, Infiltration, Depression Storage) reduction in recharge maintained to Groundwater Recharge predevelopment conditions Reference#1. LID Designs and Practices LID practices to maintain hydrologic functions can include the following: • Impervious Surface Control Devices -alternative pavers, green roof etc. • Infiltration Facilities -dry well, infiltration trench, etc. • Semi -natural Conveyance System bioretention, grass swale, bioswale, etc. • Storage - cistern, rain barrel • Landscaping - effective grading, installation of plants for water quality and quantity control. Each of these LID practices is briefly described below. Impervious Surface Control Devices Runoff from new impervious surfaces is the primary cause of flooding and stream degradation. Reducing the amount of new impervious surface area in development is one of the most effective methods to achieve a reduction in the total volume of' runoff. For example, most residential streets can be as narrow as 22 to 26 feet wide without sacrificing emergency access, on -street parking, or vehicular and pedestrian safety. A shift to narrower streets can result in a 5 to 20 percent overall seduction in impervious area. Reducing road area also reduces paving costs. 3 otak IS'\project\30700\30788\Reports\AByn SA'NIP Update \Appendices\B_LID\Appendixs-LID.doc 01/12/07 Appendix B — Low Impact Development Continued Examples of narrow residential street widths from different regions of the country are listed in Table B.3. of Narrow B.3 Street Widths Table Examples Residential State Jurisdiction Standard Arizona City of Phoenix 28 feet(parking on both sides) California City of Novato 24 28 feet feet (both (both sides, sides, 2 5 to to 4 du 15 ) du) Colorado City of Boulder 20 20 22 26 26 feet feet feet feet feet (150 (no parking, side, side, ADT) 350 500 350 350 ADT) 1000 ADT) ADT) sides ADT) 1000 — (one (both (one — Delaware Delaware DOT 21 feet (one side) Florida City of Orlando 28 22 feet feet (both (both sides, sides, res. res. lots lots <55 >55 feet feet wide) wide) Maine City of Portland 24 feet (one side) Maryland Howard County 24 feet (1000 ADT) Michigan Giiy of Birmingham 26 20 feet feet (both (one sides) side) Montana City of Missoula 26 32 12 feet feet feet (both (both. (alley) sides, sides, 3 81— — 80 200 du) du) New Mexico Albuquerque 28 feet (one side) New Jersey 20 28 feet feet (no (one parking, side, 0 0 3500 3500 ADT) ADT) — — Oregon City Portland 26 20 feet feet (both (one sides) side) of Pennsylvania Bucks County 12 16 20-22 26 28 feet — feet feet 18 (alley) feet feet (one (one (no (no side, side, parking, parking, 200 200 ADT) 200 1000 200 ADT) ADT) 1000 ADT) — — Tennessee City of Johnson City 22 24 feet feet feet (<240 — 28 (>1500 feet ADT) ADT) (240 — 1500 ADT) 28 4 otak I{ \ project \30700\30784\Repoits\Allyn SWYMP 'Update \Appendices\B_LID\AppendixB-LID.doc 01/12/07 Appendix B —Low Impact Development Continued of Narrow (cont.) Street Widths Table B.3 Examples Residential State Jurasdictton Standard Vermont City of Burlington 30 feet (both sides) Washington City of Kirkland 12 20 24 28 feet feet feet (alley) (one (both (both side) sides, sides) low density only) feet W. Virginia Morgantown 22 feet (one side) Wisconsin City of Madison 27 feet 28 feet (both (both sides, sides, <3 3 du/ac) - 10 du/ac) ADT du = average daily unit traffic = dwelling Reference #2 and #3 Other typical LID approaches include alternative roadway layout (Figure B.1) and reduced parking standards (Table B.4). The potential results of impervious surface reduction or on the overall effective impervious area, are listed in Table B.S. Note how small reductions in the total impervious area can have a relatively large reduction of the amount of on -site impacts and resulting effective impervious area within the watersheds. FRADNIENTED WARPED LQPPS AND ON POPS JWW EL LOWPQPS STICK MIEN - r\ \\. SAID \ \ ...E.7) 1 L \D II "J'r. ( PT L t. � ny yr \ .�i y rj 20,800 lt000 Approximate lineal feet of paver 16,600. 15,3to 15,6D0 Reference #11 Figure B.1- Length of pavement of various roadway layout options. 5 otak lc: \project\30700\30784\Reports\Allyn SWMP Update \Appendices\B .LID\AppendixB-LID.doc 01/12/07 Appendix B - Low Impact Development Continued Table B 4 Conventional Minimum Parking Ratios Parking Requirement Actual Average Parking Land Use Parking Ratio Typical Range Demand Single-family 2 dwelling 1.5 2.5 1.11 dwelling homes spaces per unit - spaces per unit Shopping center 5 spaces 1000 ft2 GFA 4.0 6 5 3.97 1000 ft2 GFA per - per Convenience store 3.3 spaces 1000 ft2 GFA 2.0 10.0 per -- Industrial 1 space 1000 ft2 GFA 0.5 2.0 1.48 1000 ft2 GFA per - per Medical/dental 5.7 spaces 1000 ft2 GFA 4.5 4.11 1000 ft2 GFA office per -10.0 per GFA = Gross floor building area of a without storage or utility spaces. Reference # 11, #14, and #15 Table B 5 Basin and Site Coverage Assessment Reduction Analysis Results Potential Strategy Impervious Surface Percentages Reduction (%) Site -Specific Basinwide Total Effective Total Effective 1. Reduce installing only. residential the walks sidewalks on one side by 50 of the percent street by 1.33 1.00 1.59 0.83 2. Reduce residential sidewalks from 5 feet 0.53 0.40 0.64 0.33 width to 4 feet width. 2.50 2.00 2.98 3.12 3. a. Reduce feet to 27 local feet, access street widths from 32 b. Reduce local access street widths from 32 3.50 2.80 4.17 4.37 feet to 25 feet. c. Reduce local access street widths from 32 6.00 4.80 7.15 7.49 feet to 20 feet. 2.67 2.67 1.04 1.37 4. a. Reduce commercial parking by 5 percent. 5.33 5.33 2.09 2.74 b. Reduce commercial parking by 10 percent. 10.67 10.67 4.18 5.47 c. Reduce commercial parking by 20 percent. 0.74 0.74 0.16 0.21 5. a. Reduce multifamily parking by 5 percent. 1.48 1.48 0.32 0.42 b. Reduce multifamily by 10 parking percent. c. Reduce multifamily parking by 20 percent. 2.95 2.95 0.64 0.84 4.25 4.25 1.38 .094 6. a. Reduce multifamily commercial, roof areas industrial, by 10 percent and 8.50 8.50 2.76 1.89 b. Reduce commercial, industrial, and multifamily roof areas by 20 percent. Reference #15 6 otak K:\project\30700\30784\Reports\Allyn SWMP 'Update \Appendices\B_LID\Appendix$-LID doc 01/12/07 Appendix B — Low Impact Development Continued Alternative Pavers Alternative pavers are permeable or semi -permeable surfaces that can be used for driveways, parking lots, and walkways. Figure B.2 shows typical alternative pavers. The effectiveness of alternative pavers will vary depending on the soil layer underneath. Underlying soils need to have a permeability between 0.5 and 3.0 inches per hour. The City of Seattle gives credit for porous pavement (Table B.6) in computing runoff rates from a developed site. (a) Pervious concrete ecogit Set Atfrot (c) Unit paver s/br cks (e) Crushed aggregate one. (b) Porous: asphalt. (d) Turf block (f) Cobbles Reference #17 Figure B.2 — Alternative Pavers 7 otak K:\project\30700\30784\Reports\Allyn SWMP Update \Appendices\B_LID\Appendix&LYD.doc 01/12/07 Appendix B — Low Impact Development Conttnued Table B.6 Porous Pavement Impervious Surface Reduction Credit SCS Hydrologic Soil Group A B G D Curve Number (without credit) Curve Number (with credit) 98 78 98 85 98 89 98 91 Reference #16 Due to the permeability of porous pavers, there is some risk of contaminating groundwater, although most paving alternatives have some pollutant removal effects through the infiltration process Therefore, they should be located at least two to five feet above the seasonally high groundwater table and at least 100 feet away from drinking water wells'. Other design considerations for alternative pavers are listed as Table B 7 Table B.7 Design Criteria for Alternative Pavers .Design Criterion Guidelines Take boring Site Evaluation soil to a depth of at least 4 feet below bottom of pavers to check for soil permeability porosity, depth of seasonally high water table, and depth to bedrock. Not flat recommended as possible. on slopes greater than 5%. Best with slopes as Minimum infiltration rate 3 feet below bottom of pavers: 0.5 inches per hour. Minimum depth to bedrock and seasonally high water table: 4 feet. Minimum setback from water supply wells: 100 feet Minimum setback from building foundations: 10 feet downgradient, 30 meters (100 feet) upgradient. Not recommended in areas where wind erosion supplies significant amounts of windblown sediment. Drainage area should be less than 15 acres Traffic Conditions Use for low -volume automobile parking areas and lightly used access roads. Avoid moderate to high traffic areas and significant truck traffic. Avoid snow removal operation. Post with signs to restrict the use of snow sand, cleaning salt, and activities. other deicing chemicals typically associated with `Please refer to the new draft State Underground Injection Control Rule, 2005. 8 otak IC: \project\30700\30784\Reports\Allyn S\'JMP Update \ Appendices \B_LID\AppendixB•L[D_doc 01112I07 Appendix B — Low Impact Development Conttnued . Table B 7 (cont.) Design Criterta for Alternative Pavers Design Criterion Guidelines Design Volume Storm Storage Highly variable; depends upon regulatory requirements. Typically design for storm water runoff volume produced in the tributary watershed by the 6-month, 24-hour duration storm event. Drainage Design Storm Time for Minimum 12 hours. Maximum: 72 hours Recommended: 24 hours. Construction Excavate and grade with light equipment with tracks or oversized tires to prevent soil compaction. As needed, divert storm water runoff away from planned pavement area before and during construction. A typical porous pavement cross-section consists of the following layers: 1) asphalt course, 2 4 inches thick; 2) filter porous aggregate rock; and course; 4) filter 3) fabric reservoir course of 1.5-3-inches of washed Porous Pavement Paving temperature: 240° - 260° F. Placement Minimum air temperature: 50° F. Compact with one or two passes of a 10-ton roller. Prevent any vehicular traffic on pavement for at least two days. Pretreatment Pretreatment recommended to treat runoff from off -site areas. For example, place a 25-foot wide vegetative filter strip around the perimeter of the porous pavement where drainage flows onto the pavement surface. Reference #18 Green Roofs Green roof applications can be appropriate for some commercial and multi -family residential lots where the buildings occupy a large portion of the site. A layer of absorbent soil on the top of building retains rainfall and allows it to evaporate or transpire from the rooftop vegetation. The runoff from a green roof passes through the absorbent soil layer to an underdrain layer (there is no surface runoff), and therefore, peak runoff rates are attenuated. Green roofs provide multiple benefits such as attenuation of heat island effects which help to save on the energy cost of the building and sound reduction. Green roofs are classed into two categories: • extensive green roofs; shallow soil layer of 3 to 7-inch 20-34 1b/square feet weight • intensive green roofs; thick soil layer of 8-inch to 8-foot 9 otak K:\project\30700\30784\Reports\Allyn SWMP Update\Appendices\S LID\AppendixII-LID.doc 01/12/07 Appendix B — Low 80-150 lb/square feet weight mpact Development Continued Recently, new technologies have made green roofs lighter to reduce the additional cost of supporting structure of the building. Figure B.3 shows typical green roof profiles. Rain or $prikier Growing: Medium Root Barrier Drain Core Separation Fabric Insulation Roof Membrane: Structural Support Rain or Sprikler •-Growing Medium Sand and Gravel Root Barrier Insulation Roof Membrane Structural Support Reference #19 Figure B.3 - Green Roof Profile As the least weight green roof, sedum roof has been tested at many locations. Sedum is dry -tolerant plant that can grow with a thin soil layer (one to two-inch). It reduces the weight of green roof five to eight lb/square feet, eliminating the need for additional structural support. Figure B.4 shows sedum roof profiles and details. z14t t t t•-• t� ;fir _ Reference #20 s. PIant n g mat:, irainajge mat_`. Figure B.4 - Sedum Roof Profile and Detail Studies show that about one -foot of soil depth is needed to achieve the maximum reduction in runoff rate from prolonged winter storms. However, significant reduction in runoff rates from short intense storms that occur during dry weather periods can be achieved with as little as four inches of soil depth. 10 otak K:\project\30700\30784\Reports\Allyn SWMP Update \Appendices\B_LID\AppendixB-LID.doc 01/12107 Appendix B — Low Impact Development Continued The City of Portland gives new green roofs the same credit as forest cover, allowing a curve number of 48 for roof gardens (intensive green roof) and a curve number of 61 for Eco-Roof (extensive green roof). In Germany, 3-inch green roofs have been found to be cost effective, and appreciable runoff will not begin until rainfall amounts exceed 0.6 inch. Infiltration Facilities— Dry Well Dry wells are small, excavated trenches backfilled with aggregate They function as infiltration systems and are often used to control runoff from building rooftops Dry well designs can be modified to act as catch basins, where they both collect and infiltrate direct surface runoff. Figure B 5 shows a typical detail of a dry well. 1116 Nor five at UUILDINf FOUN€ 4Tta :TOP' LID Ati6 N WELL. EK..�l�t i WATER TFd3LE Reference #7 Figure B.5 - Typical Dry Well Section Infiltration Facilities —Infiltration Trench An infiltration trench is a shallow excavated trench that has been backfilled with coarse stone aggregate. It can be an underground reservoir or subsurface basin (Figures B.6 and B.7). Stormwater runoff is diverted into the trench and is stored until it can be infltrated into the soil, usually over a period of several days. Infiltration trenches are a good design option in sandy soils where the depth to the maximum wet -season water table or hardpan is greater than three to six -feet. (Note: The new draft of the Washington State Underground Injection Control Rule has specific design recommendations for dry wells based on soil types and risk of aquifer contamination ) otak K:\project\30700\30784\Reports\Allyn SWMP Update \Appendices\B_L1D\AppendixB-LID.doc 01/12/0 7 • 44 Reference #21 Appendix B — Low Impact Development Continued Figure B.6 - Subsurface Infiltration Trench Bioretention Bioretention is a water quality and water quantity control practice. It uses the chemical, biological, and physical properties of plants,microbes, and soils for removal of pollutants from stormwater runoff. Bioretention typically is used to treat small (0.25-1.0 acre), highly impervious surfaces such as parking lots and commercial areas. It is designed to contain an average annual storm event of about 0.5 — 0.7 inches of rainfall (Reference #21). Bioretention consists of grass buffer strips (pretreatment area), ponded area, planting soil, sand bed, organic layer (mulch), and vegetation. A conceptual illustration for a bioretention area is presented in Figure B.8. The bioretention area design provides infiltration and water storage for uptake by vegetation. 12 otak Kc\project\30700\30784\Reports \Allyn SWMP Update \ Appendices \B_LID\Append xB•LID.doc 01/22107 Appendix B — Low Impact Development Continued • 4" r.laId or err: 4iO forated:plpr ......................... .....lb overflow splash blodt 4,4.44 VI44--- wad lirod{( 6i4 0^�f fllteir fabric • tte flue. (nosh ecre.n PROFILE VIEW NTS SacTIOH A NTS roof dr n ittor sump' h fid lid .' dgld are' flexff.s perforated pipe Reference #16 Figure B 7 - Underground Infiltration Trench The surface of the planting soil is depressed to allow for ponding of runoff. Collected runoff is infiltrated through a surface organic layer of mulch and/or a ground cover to the planting soil The runoff is stored in the planting soil where it is discharged over a period of days to the native soil underlying the bioretention area. Bioretention areas should be designed as an off-line treatment system. In off-line systems, the "first flush' , which is the most contaminated sheet flow, is retained, and larger flows are bypassed into the normal storm drain system. Such a design prevents the first flush from being washed out by higher discharges associated with on-line systems. Bioretention has many potential side benefits other than water quality treatment. Plantings can improve the aesthetic value of the site as well as providing ecological value, such as improved habitat for small animals, shade, privacy screens, and wind breaks. 13 otak K:\project\ 30700\30784\Reports\Allyn SWMP Update\Appendices\B_LID\AppendixB-LID.doc 01/12/01 A Tap 6f j vegetetet! berm mit of Disturbance • Trees Shrub Bioretentton area limit Grass filter strip ruruur. ;nv...,,.;..- .e..:,,.u. rec®mmeoded t Minimum•f►eeboard• 0.2 feet from maximum • ponding depth Maximum ponded Grass fitter water depth (specific to plant sod texture) Appendix B — Low Impact Development Continued Overflow outlet Ground cover or newish layer Sheet flow Limit of pavement Near verti sidewalls sr Sheet flow A 4 R{aa view (not to scale) Bloretentlon area Ground cover or mulch Layer INASITU Material SaturatedPerrneability Greater than O.5.inches per hour length:2O feet Existing edge of pavement --►� �®-----5' min. ni A �IIIIiL=' 1 fill 2-4' min. Section A -A (not to scale) 31 max. slope Reference #7 Figure B.8 - Plan View and Section of Bioretention Area Cost reduction is another benefit of bioretention facilities. In Prince George's County, Maryland, a case study demonstrated that bioretention can be an economical alternative for providing treatment for the first half -inch of runoff from 14 otak K:\project\30700\30734\Reports\Allyn SWMP Update \Appendices\B_LID\AppendixB-LID.doc 01/12/07 Appendix B — Low Impact Development Continued commercial and residential sites. For example, the total estimated cost of a water quality treatment facility for an office building was reduced from $174,000 with oil - grit separators to $111,600 with a bioretention area. For other office building sites, evaluated, bioretention practices reduced the amount of storm drainpipe from 800 to 230 feet. Grass Swale Grass swales provide a series of vegetated open channels that are designed specifically to treat and attenuate stormwater runoff. They are best applied on a relatively small scale (generally less than five acres of impervious surface) There are many design variations including dry swales, wet swales, and biofiltration swales. These systems work well along roadways, driveways, and parking lots. Dry swales are similar in design to bioretention areas. They typically have a sand/soil mix layer that meets minimum permeability required at the bottom of the channel. An underdrain system is also installed under the soil bed. Typically, the underdrain system is created by a gravel layer which encases a perforated pipe. Stormwater treated by the soil bed flows into the underdrain, which conveys treated stormwater back to the storm conveyance system (Figure B 9) Wet swales intersect the groundwater and behave like a linear wetland cell. This design variation incorporates a shallow permanent pool and wetland vegetation to provide stormwater treatment. One disadvantage to the wet swale is that shallow standing water in the swale can cause public nuisance by providing mosquito breeding habitat. A biofiltration swale is similar to a dry swale. It is more specifically designed for the treatment of stormwater. The primary pollutant removal mechanisms are filtration by grass blades which enhance sedimentation, trapping, and adhesion of pollutants to the grass and thatch. Biofiltration swales generally do not effectively remove dissolved pollutants Maintaining dense vegetation is the key to its effectiveness. Therefore a swale should receive a minimum of six -hours of sunlight daily during the summer months for healthy grass growth. A swale must dry between storms to maintain vegetation in good condition. For permanent saturated soil conditions, a wet biofiltration swale should be installed. Because typical grass dies when soil saturation exceeds two weeks, vegetation specifically adapted to saturated soil conditions should be used. 15 otak K:\project\30740\30784\Reports\Allyn SWMP Update \Appendices\B_LID\Appendi`8-LiD.doc 01/12/0 7 Reference #1 Appendix B — Low Impact Development Continued Figure B.9 - Plan View and Section of Dry Swale Grass filter strips are vegetated areas intended to treat sheet flow from adjacent impervious areas. Filter strips function by reducing runoff velocities and filtering sediment and other pollutants. With proper maintenance, filter strips can provide relatively high pollutant removal. Grass filter strips require a relatively large amount of space, typically equal to the impervious area they treat. The land requirements for this practice can be a critical drawback in urban environments, where land prices are high. (Reference #1) tb otak K\project\30700\30784\Reports\Allyn SW1v1P Update \Appendices\B_LID\Appendi R-LID.doc 01/12/07 Appendix B — Low Impact Development Continued Storage Rain barrels and cisterns are low-cost, effective, and easily maintainable storage units applicable to both residential and commercial/industrial site. Rain barrels operate by retaining a predetermined volume of rooftop runoff. In general, cisterns have a larger capacity and are installed either an rooftop or underground. Washington State Department of Ecology's stormwater design manual suggests that cisterns should provide at least 1,000 gallons of storage to have any significant hydrologic effect. Costs and Benefits Conventional and LID stormwater management costs are difficult to compare, because "marginal costs' are rarely defined for either approach. Some case studies and pilot programs show at least a 25 to 30 percent reduction in costs associated with site development, stormwater fees, and maintenance for residential developments that use LID strategies. These savings are achieved by reductions in clearing, grading, pipes, ponds, inlets, curbs, and paving. However, many Lill projects have not been fully assessed in the long run due to its early stage in implementation. Some of this basic information is also lacking for conventional stormwater management as well. For instance, the costs to retrofit and repair an entire pipe system after 50 or 60 years are rarely estimated for conventional management. (Reference #8) In addition, costs are site specific Each project will be unique based on the site's soil conditions, topography, existing vegetation, land availability, etc. Some commonly seen cost benefits of LID projects include the following: 1. Multi -functionality —In many projects, LID was originally designed as a landscaped feature before its functionality as a stormwater control was introduced. In these situations, the landscaping and construction costs for stormwater have not been included and financially appear to be free. Additionally, the cost of maintaining the landscaped areas is typically included in the project cost and not in the cost of the stormwater system. 2 Lower lifecycle costs —It is important to take into account not just the initial capital costs but also those over the structure's lifetime which can include operation, repair, maintenance, and decommissioning. Many LID techniques are self-perpetuating, easily repairable, or can be left as natural areas at the end of their functional lifetime, while conventional facilities may require high costs to take out of commission, repair, maintain, and/or replace. 3. Reduced off -site costs -Since LID addresses stormwater trunkline conveyance at its source, it is unlikely to incur major off -site costs in the form of conveyance network or outfalls. Most conventional techniques will require an off -site conveyance network to collect the stormwater from the on -site system, resulting 17 otak K:\nroiect\30700\30784\Reports\Allyn SWMP Update \Appendices\B_LID\AppendicB-LID,doe 01/12l0 7 Appendix B — Low Impact Development Continued in additionalproject costs for the enhancement of downstream systems as urban areas expand 4. Functional use of open space land LID practices, such as bioretention, can usually be designed as part of the development's open space. Unlike large detention ponds, if these multifunctional LID practices are distributed throughout set -aside open space or previously designated landscaped land they can contribute to a more park -like and community -friendly setting without incurring any additional costs for land allocation to the drainage system. LID techniques will become less expensive over time as a growing number of competing LID practitioners drive clown prices and the technology becomes standard Roofscapes Inc. expects that overall cost of green roof systems to decline by about 25 percent over the next couple of years (Reference #12). Currently, costs of each LID technique are estimated as follows: • Green roof; $5.6 to $14 /square feet2 • Absorbent landscaping/Bioretention; $2.3 to $6.5 /square feet3 • Dry swale (80 percent bioretention area): $1.8/square feet to $5.2/square feet (Reference #1) • Porous pavement: $2 to $3 /square feet (conventional asphalt costs $0.5 to $1/square feet) • Infiltration facilities : $2.8/square feet to $16/square feet • Manually constructed cisterns (reinforced concrete, size of 3,000 gallons): $1,000 Summary: Applicability of LID to Mason County Due to its natural setting, there will be many opportunities to use LID designs for the management of surface water runoff as the land within Mason County continue to develope_ Table B 8 summarizes the applicability of the five major practices of LID design briefly discussed in the above literature review. 2 Extensive roofs are in the lower range, and intensive roofs are in the higher range. A pilot project in the City of White Rock, BC which has a four -inch deep soil layer, costs about $8.4/square feet than a conventional impervious roof. (Reference #5) 3 Sites with six-inch deep absorbent soil layer are in the lower range, .and sites with 1.5-foot deep absorbent soil layer in the higher range. 18 otak K:\project\30700\30784\Reports\Allyn SWMP Update \ Appendices \B_LID\AppendidB-LID.doc 01/12/07 Appendix B — Low Impact Development Continued Table B.8 Potential Applicability of LID Practices within Mason County LID Practice Applicability to Mason County Examples Porous Pavement - Could be incorporated into any building Impervious Control Surface Green Roofs - design Could design be incorporated into any building Infiltration Facilities Dry Well - Recommended for rooftop runoff, provides some attenuation of storms and some infiltration. Infiltration Trench Recommended for - conveyance, provides infiltration and some detention Semi -Natural Bioretention Grass Swale/Bioswale Filter Strips - Include with landscaping where possible. - - Good treatment. Good for for small parking site lots attenuation and Conveyance System Storage Cistern - - Of Could limited be use used (unless for of some dry a Large season scale). Rain Barrel watering Landscaping Effective Use of Plants Grading - Of limited stormwater benefit unless of a - large Recommend landscape scale. and incorporating green space LID areas into to save costs and provide natural aesthetic look to the site In general, LID strategies can be beneficial and are recommended for future development within Mason County. The greatest attraction of the LTD in surface water management design is the ability to better mimic some of the naturally occurring drainage systems As development occurs, LID strategies could be used to simulate these natural systems. The challenge for the Mason County land owners is to determine which LID strategies should be used and where should they be located. LID designs typically require land, and typically are more costly than conventional drainage designs. Unless they can be incorporated into required landscape and open -space areas, the use of the conventional regional detention and treatment systems may still be the best way for a land owners or developers to optimize the amount of land available for new construction. Clearly a reasonable tradeoff will need to be made between costs, availability of land, and the cost and ability to mitigate environmental impacts as development within Mason County continues. 19 otak K:\project\30700\30784\Reports\Allyn SWMP 'Update \ Appendices \B_LID\AppendixB-LID.doe 01/l2/07 References Appendix B — Low Impact Development Continued 1. Better Site Design Fact Sheet homepage, http://www.stormwatercenter.net 2. Center for Watershed Protection. 1998. Better Site Design. A Handbook for Changing Development Rules in Your Community. Ellicott City, MD 3. Cohen, A. Narrow Streets Database. Congress for the New Urbanism. Available online at: www.sonic.net/abcaia/narrow.htm 4. CRC, 1996; Davis et al. 1997; MWCG, 1987; Urbonas and Stahre, 1993; Youse£ et al., 1985; Yu et al., 1992; Yu et al., 1993. 5 Effectiveness of Stormwater Source Control, Greater Vancouver Sewerage & Drainage District, 2002 6. Introduction to LID, Low Impact Development Center Inc., http://www.lid- stormwater.nethntro/background.htm#1 7 Low -Impact Development Design Strategies, An Integrated Design Approach, Prince George's County, Maryland, 1999 8 Low -Impact Development, Mary Catherine Hager, Stormwater January/February 2003 9. Municipal Guide to Low Impact Development, Low Impact Development Center Inc , http://www.lowimpactdevelopment org/lid%20articles/Municip al LID.pdf 10. Natural Approach to Stormwater Management, Puget Sound Action Team, March 2003 11. Parking Generation, 2nd edition. Institute of Transportation Engineers, Washington, DC 1987. 12. Roofscape Inc., homepage, http://www.roofineadow com/ 13. SEA Street homepage, Seattle Public Utility, http://www.seattle.gov/util/SEAStreets/default.htm 14. Smith, Thomas. Flexible Parking Requirements. Planning Advisory Service Report No. 377. American Planning Association, Chicago, IL. 40 pp. 1984 20 otak IC: \project\30700\30784\Reports\Allyn SWMP Update \Appendices\B LID\AppendixB•LID_doc 01/12/0 7 Appendix B -- Low Impact Development Continued 15. Wells, Cedar. Impervious Surface Reduction Technical Study. Draft Report. City of Olympia Public Works Department. Washington Department of Ecology, Olympia, WA. 1994. 16. City of Seattle. Flow Control Technical Guidance Manual, November, 2000. 17. Green Streets Innovative Solutions for Stormwater and Stream Crossings, Metro June 2002. 18. Stormwater Technology Fact Sheet, Porous Pavement, EPA, September, 1999. 19. Amergreen Roof Garden System, http://www.americanwick.com/pdf/amergreen.pdf. 20. Thin -Layer Roof Top Greening System Using Sedum Carpet, http://www.takenaka.co,ip/takenaka-e/techno/lolo-sedum/. 21. Schueler, T.R., Controlling Urban Runoff A Practical Manual for Planning and Designing Urban Best Management Practice, Metropolitan Washington Council of Governments. 1987. 22. The Bioretention Manual. Programs and Planning Division Department of Environmental Resources, Price George's County, Maryland, November 2001. 21 otak li:\project\30 700\30784\Reports\Allyn SWMP 'Update \ Appendices \B_.ID\AppendixB-LID.doc 01/12/07 Low Impact Development (LID) Screening Matrix Comments �o. GIS includes information such as topography, d water features (including wetlands and ins) that can be shared with property owners. contact information in a brochure distributed to Lice iason Co. GIS includes information such as topography, uls, and water features (including wetlands and )odplains) that can be shared with property owners. rovide information and examples in a brochure distributed the public. Provide information and exampl to the public. Mason Co. GIS includes info= soils, and water features (includ floodplains) that can be shared Provide information and exam] to the public. Applicability ) / All subbasins § . Cn / PO C\ /$ ) Q c $ . f / §0/ 50 $ t E » « * /iceƒ / 2 / /Limin q phase planning is perfon on LID elements. Site trs to placing developrne tally sensitive areas (wet] e open spaces, tree save areas, and temporary an five buffer zones. It also :e to areas where st tuctu will exist after construct rent. Loodpl Desch] pn ad )ad c: sign. :e the site. 'dresses a primal is system impervi 3r infiltra )sely mir on of the P 2 5 8 8 1 ) § § q \ planning and 4. Preserving native soils and vegetation 7 \ & \ ƒ 0 \ \ Cr) ƒ rl versity Pierce County Extension, Low Impact Development Guidance Manual for Puget Sound, Update \ Appendices \B L[D\LIDScreening Low Impact Development (LID) Screening Matrix instead of curb and gutter infrastructure. :enance of their right of way. l examples in a brochure distributed Mason County proposed zoning currently limits tl structure size and the maximum allowable lot cov many of the proposed zones. comment examples ac), highl nercial arc 1 cn .c w cd M i All basins BP, R-3, POS, VC, VR cn 0 .a cP and grading, the primary LID mize site disturbance through of grading and retaining his technique seeks to minimize tions and control sediment yield 'unction to collect, store and linear basis such as in roadway medians. The sloped biodetention technique uses gra; vegetative barriers such as .hedgerows on co. detain stormwater and reduce pollutant load known as "rain gard ition of stormwater id Ls a lec .ttei prl • Lail Wi wl; ire l al: 6) Z 5. Clearing and grading 6. Bioretention cells 7. Sloped biodetention 8. Bioretention swales En 4-4 10. Maintenance tr as rn a-) H H cc K:\project\30700\30784\Reports\Allyn SWMP Update \Appendices\B—LID\LIDScrceningMatr& LR.doc Screening Matrix J C N 0 0 cu 4-3 V 0- E 0 J Enm m ents Provide information and examples in a. brochure distributed to the public. recharge, no space 1 y (US GBC) ls, not suitable for h .ntial for failure, rec Si C Description v 2 i 1.' p 0 PO RRil v ..0 j 0 0 0.0 v '-' 5 d 't3 lrlWO O ca 44-0 .-. to441 f� U p cc i1 U y' p v 0 Li-4p ca ro rC u4-1 til L)y id hto amu vcv d 4-1 O ' y'' 4' 'La yv i c�1 n ci 0- bA t.lO v•444 cn HvU istur] 3logic :sinl ions V't-o ,� V y v V v 1-C4 u 0 ij ci, U bA al0. Q Ov rb 0 as vcgi u0 O e} v ;a b.Q g u 4 a: a.) bA O bA 04 ..� v .a) , ti cd •. n . a a ccd v y 0 0 cn . N ,? A •v R _ s' v v v as v 'd �' as `d a+ . �i ,p Cd '� �+ �' i-' 1� + ri ,F,>ii:ia r 0' C .r) i 4 ed CS hZit0 O cC 'd v • o • ♦ Q too v 0 flcu ' pU .t� VA° H O CI) hnique v .0 03 '.' v Amend >nstructio: a) N ,-`a Gk K:\project\30700\30784\Reports\Allyn SWM) Update \ Appendices \B_LID\LIDScrecningMatiix L.R.doc le information and examples in a brochure distributed public. Basins with well draining soil and low % impervious it v 5 aformation and examples in a brochure distill blic. loi .! U O H CI • 50.4 0 ci 0 0 cis iescription Applicability .a 0 .5 1 0 ei O rn cd fn CI v cd Low density Residential zoning areas te re re V 0 byA cst O H v 7 CQj O 0 V ra C ;tol G4SA an Ear Y prc run e are. and 0 0 0 b0.0 "0 0 ci •N u ti 4 0" y 0 C bNO H 0 g v t0aFt '0 a v V s "� p O E u o -. v ,- H + u" H O 0 v, '� O v f=, .ii o O• H v 4, O 4_1 0 O v O y .7 ro O v (u n ivs c� _ H Ov "v v :� "'cci w v 0 O a.s t) 'g W Ct" y R "ic O O w > N ° hnique t+-1 0 I O H 15. Homeowner education Downspout rsion "d N et 44 ao v eh ations K:\project\30700\30784\Reports\Allyn SWMP Update \Appcndices\H,.UD\LlDScreenin Low Impact Development (LID) Screening Matrix Comments Helps reduce the size of regional facilities subbasins requiring rate control. ice water quality feature is economical some habitat (US Green Building ps work best with low velocity flows. Good for large developments, or region] volume control, high removal efficiency, : value, Requires significant space, some m not economical for small developments. Subbasins requiring rate control EF010, EF015, SF010, SF020, and SF030 outfalls at enough space to ovide her WQ icility Upstream of outfalls and/or at shared use public open space • / ( u 7 / \ / / ai / AN CU� uoudiiasai issy slopes located adjacent to an sbject to vehicular traffic. oved by the action of grass blades Gmentation and trapping and ants to the grass. Filter strips are for sheet flow over the entire filter er harvesting (also knov the collection and storaj estic or irrigation purpc ems include a collectior device (tank or vault) ai ei ar; a sa m Ld, in :ed Q cr \ Constructed ;land 17. Roof stormy harvesting systen \ o u \ 2 \ - % m j Appendix C--Hydrologic Analysis MGSFIood :Analysis MGS Flood, Version 3. 0 O r N -o 03 a) CD O 0 CA CV N_ r r a) 0 CC ma a 0 0 3,800 4,400 4,200 3,600 0 0 00 0 0 0 0 0 CD 0 I Wet F (CI NI Top Area (SF) 4,495 r NA NA NA < <C r 0 (ffiN N I Results I Develop z Z 12,139 z NA NA (3) `n LCI CI z z Design Discharge a) co co r CO 1.26 8.7 -4 u) d° 0 4 ci E di U a) co N N N cv 10 u) 4 M O) r N ter Qual as e0 N r .0 N 4 r r r r e — c o aWnlOA 92,437 76,221 CO CO 433,449 a) C) CO I"- CO U C m 0 32C O 0 01 r co tention !_ a) o At Riser (cfs) N. 256,505 NA NA NA co O Z. Z ® co CO O c a) E ❑ 0 CO C)) (� G) NA NA Z CI) N p AI /_L Z Z r r 100,800 0 < '� NA < Q o Q Bottc Areal O o a. Z z z z 00 Surface Water Runoff* Cr O N N C cri 9.1 / 7.8 CC) Cam] co N COr cp 0) 6 co Ci) 7, co6 N r '� 1'" N 4.5/2.7 1.3 / 0.7 3.3 / 3.6 CY) co d CD CA O) N 0 (7 CQ 4 l() r N r 52.15 N 25.59 0) �? r CO C7 to N C4 CO /VOGV basin (ac) r • r N r Sherwood Creek North Sherwood Creek South k Park tfall Evans St. Outfall c Inamec panne basi _ vvauc 1 Outfal a. 2 ® w * Predeveloped / Postdevelopment for basin requiring rate control Cfl 0 O N 'C N L2 Cei Q G O N CD N O (0 > cLJ O 0 .0 .0 O "-° -0 "C3 T. 91 a) Y so 0 , OS 20 Typical Results Per 1 Acre Developed a) cN 0.05 228,532 260,456 60,2001 1.751 1.021 22,9001 6,600, 6,1001 0.181 0.10 t 0 a> Jor0 o, Wet Pond (CF) 4,400 Footprint (SF) a O CO a Detention (CF) O 0 0) d v-- N C W d RO fJ t Design C G""O - i-- :'' 7 Cf i. C 0 0 co 0) E 7 Basic Wet Pond (cf) 43,789 ti Detention G) E At Max (cfs) co CO CO ti r- hi -171 148,294 > it U Q Max Storage Depth (ft) O N C7 O CO imensioi Bottom (sf) I 42,0501 65,4801 Bottom (ftxft) CO It LC) c0 X 0) N X O cc) }posed Condition Land Use Developed CO N Acres Gra: W O CO O d Cb U N Q a E x HC t3) _C_ G O N cL K:\project\30700\30784\WaterRes1MGS\TestPlotSummary.xls, 11-22-06 MGSF1ood Analysis Kayak Park MGS FLOOD PROJECT REPORT Program Version: 3.09 Run Date: 12/06/2006 9:45 AM Input File Name: PortPark__noSR3.fld Project Name: Port Park no SR-3 - New Outfall Analysis Title: Proposed runoff to proposed port park outfall - no SR-3 Comments Basin EF080 drains to the proposed port park outfall. Looked up long. and lat. online. Requires WQ treatment. ********** Precipitation In putn******** Extended Precipitation Timeseries Selected Climatic Region Number: 7 Full Period of Record Available used for Routing Precipitation Station 950056 Puget West 56 in MAP 10/01/1939-10/01/2097 Evaporation Station : 951056 Puget West 56 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********** Watershed Definition ********** Number of Subbasins: 1 *"********Subbasin Number: 1 *********" ***Tributary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasin Total Subbasin 1 --- -- ----> Node 1 Predeveloped 1.270 2.480 5.630 O .800 0.670 5.280 O .000 9.460 25.590 Area(Acres) --------------w_._ ------------Developed---------- Bypass Node 0•000 0 000 0 000 0 000 0 000 O 000 a 000 O 000 O 000 To Node 1.270 2.480 5.630 O .800 O .670 5.280 O .000 9.460 25.590 *** Subbasin Connection Summary*** *** By -Pass Area Connection Summary *** No By -Passed Areas in Watershed Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 1 *** Postdeveloped Structure Summary *** K:\project\30700\30784\WaterRes\MGS\PortPark\PoItPark noSR3\Kayak_noSR3short.rtf 1 of 2 MGSF1ood Analysis Kayak Park ***********Water Quality Facility Data ************* Node No: 1 Basic Wet Pond Volume (91 % Exceedance): 89734. cu-ft Computed Large Wet Pond Volume, 1.5*Banc Volume. 134601. cu-ft 2-Year Discharge Rate : 4.325 cfs 15-Minute Timestep Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 2.22 cfs Off-line Design Discharge Rate (91% Exceedance): 1.26 cfs Computed Flow Splitter Data Onfice Diameter: 5.00 inches Baffle Wall Height (WQ Design Depth): 3.46 feet Baffle Wall (Weir) Length. 5.05 feet (60.5 inches) Ratio: WQ Depth/Orifice Diameter: 8.3 (>=2 PASS) ***********Compliance Point Results ************* Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 1 ***Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Tr (Years) Discharge (cfs) Postdevelopment Runoff Tr (Years) Discharge (cfs) ** 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Record too Short 4.325 5.89E 6.892 9.164 10.423 11.490 12.818 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year to Compute Peak Discharge for These 4.325 5.898 6.892 9.164 10.423 11.490 12.818 Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped %Q2 (Must be Less Than 0%): Maximum Excursion from %Q2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS 0.0% PASS 0.0% PASS 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS K:\project\30700\30784\WaterRes\MGS\PoItPark\PortPaIk noSR3\Kayak_noSR3short.rtf 2 of 2 MGSF1ood Analysis Evans St. Outfall MGS FLOOD PROJECT REPORT Program Version: 3.09 Run Date: 12/06/2006 10:17 AM Input File Nam Project Name: Analysis Title: Comments and lat. online. e. Evans_noSR3.fld Evens St. - New Outfall - no SR3 improvements Proposed runoff to proposed Evans St. Outfall Basins EF040 and 050 drain to the proposed outfall. Looked up long. Requires WQ treatment. ********** Precipitation Input********** Extended Precipitation Timesenes Selected Climatic Region Number: 7 Full Period of Record Available used for Routing Precipitation Station 950056 Puget West 56 in MAP 10/01/1939-10/01/2097 Evaporation Station : 951056 Puget West 56 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User)*****"******** Number of Subbasins: 1 ***Tributary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass wetland Impervious Subbasin Total ********** Watershed Definition ********** *`A"A""** Subbasin Number: 1 ********** -.w-»---------- --- - ----Area{Acres) •Developed----------- Predeveloped To Node Bypass Node 10.260 15.880 32.020 O .000 O .000 0.910 0.140 68.380 127.590 Subbasin 1 > Node 1 10.260 15.880 32.020 0.000 0.000 0.910 0.140 68.380 127.590 O .000 O .000 O .000 O .000 O .000 O .000 O .000 O .000 O .000 ***Subbasin Connection Summary*** *** By -Pass Area Connection Summary*** No By -Passed Areas in Watershed • Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 1 *** Postdeveloped Structure Summary*** K:\project\30700\30784\WaterRes\MGS\Evans\Evans_noSR3\Evans_noSR3short.rtf 1 of 2 Tr (Years) Discharge (cfs) MGSF1ood Analysis Evans St. Outfall ***********water Quality Facility Data ************* Node No: 1 Basic Wet Pond Volume (91 % Exceedance): 608335. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 912503. cu-ft 2-Year Discharge Rate : 29.961 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 15.20 cfs Off-line Design Discharge Rate (91% Exceedance): 8.70 cfs Computed Flow Splitter Data Orifice Diameter: 12 00 inches Baffle Wall Height (WQ Design Depth): 4.96 feet Baffle Wall (Weir) Length:.17.43 feet (209.2 inches) Rato: WQ Depth/Orifice Diameter: 5.0 (>=2 PASS) *** Point of Compliance Flow Frequency Data *** Recurrence interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) ** 2-Year 29.961 2-Year 29.961 5-Year 36.424 5-Year 36.424 10-Year 44.999 10-Year 44.999 25-Year 56.031 25-Year 56.031 50-Year 65.805 50-Year 65.805 100-Year 70.548 100-Year 70.548 200-Year 83.002 200-Year 83.002 Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped Y2Q2 (Must be Less Than 0%): Maximum Excursion from%Q2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS 0.0% PASS 0.0% PASS 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS K:\project\30700\30784\WaterRes\MGS\Evans\Evans_noSR3\Evans_noSR3short.rtf 2 of 2 MGSF1ood Analysis Wade St. Outfall MGS FLOOD PROJECT REPORT Program Version. 3.09 Run Date: 12/06/2006 10:08 AM Input File Name: Wade_noSR3.fld Project Name: Wade St. - New Outfall - No SR-3 improvements Analysis Title: Proposed runoff to proposed Wade St. Outfall Comments Basins EF030 and 035 drain to the proposed outfall. Looked up long and lat. online. Requires WO treatment. ********** Precipitation Input********** Extended Precipitation Timeseries Selected Climatic Region Number: 7 Full Period of Record Available used for Routing Precipitation Station 950056 Puget West 56 in MAP 10/01/1939-10/01/2097 Evaporation Station : 951056 Puget West 56 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User)*************** Number of Subbasins: 1 ***Tributary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasin Total Subbasm 1 ------ > Node 1 ********** Watershed Definition ********** ********** Subbasin Number: 1 "********* ---Area(Acres) -----------Developed--------- Predeveloped 1.260 1.260 8.241 0.030 O .030 O .020 O .000 42.829 53.670 To Node 1.260 1.260 8.241 0.030 0.030 0.020 0.000 42.829 53.670 • Bypass Node O 000 a o00 O 000 o.000 (Lou O .000 O .000 O .000 O .000 ***Subbasin Connection Summary *** *** By -Pass Area Connection Summary *** No By -Passed Areas in Watershed Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 1 K:\project\30700\30784\WaterRes\MGS\Wade\Wade_noSR3\Wade_noSR3short.rtf 1 of 2 MGSF1ood Analysis Wade St. Outfall ***********Water Quality Facility Data ************* Node No: 1 Basic Wet Pond Volume (91% Exceedance): 320424. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 480636. cu-ft 2-Year Discharge Rate : 16.363 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 9.34 cfs Off-line Design Discharge Rate (91% Exceedance): 5.45 cfs Computed Flow Splitter Data Orifice Diameter: 9.00 inches Baffle Wall Height (WQ Design Depth): 6.15 feet Baffle Wall (Weir) Length: 6.72 feet (80 7 inches) Ratio: WQ Depth/Orifice Diameter: 8.2 (>=2 PASS) *** Point of Compliance Flow Frequency Data Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Tr (Years) Discharge (cfs) Postdevelopment Runoff Tr (Years) Discharge (cfs) ** 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Record too Short 16.363 20.214 24.076 28.347 33.615 37.573 42.971 to Compute Peak 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Discharge for These 16.363 20.214 24.076 28.347 33.615 37.573 42.971 Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped%%Q2 (Must be Less Than 0%): Maximum Excursion from'/zQ2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% 0.0% 0.0% 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS • PASS PASS PASS K:\pro.ect\30700\30784\WaterRes\MGS\Wade\Wade_noSR3\Wade_noSR3short.rtf 2 of 2 MGSFIood Analysis Tacoma Power Easement Outfall MGS FLOOD PROJECT REPORT Program Version: 3.09 Run Date: 12/0612006 10:01 AM Input File Name: Project Name. Analysis Title: Comments- Basins EF010, 020 and 025 drain to the proposed power easement outfall. Looked up long. and lat. online. Requires WQ treatment. Tacoma_noSR3.fld Tacoma Power Easement - New Outfall - no SR-3 Proposed runoff to proposed Tacoma Power Easement outfall ********** Precipitation input********** Extended Precipitation Timeseries Selected Climatic Region Number: 7 Full Period of Record Available used for Routing Precipitation Station : 950056 Puget West 56 in MAP 10/01/1939-10/01/2097 Evaporation Station : 951056 Puget West 56 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********** Watershed Definition ********** Number of Subbasins: 1 **********Subbasin Number: 1 ********** ***Tributary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass wetland Impervious Subbasin Total Subbasin 1 > Node 1 Predeveloped 5.210 5.070 25.850 O .150 0.150 O .120 0.000 50.170 86.720 Area(Acres)----•--- -..- -----Developed Bypass Node 0 000 O 000 O 000 O 000 O 000 O 000 0 000 O 000 0 000 To Node 5.210 5.070 25.850 O .150 O .150 O .120 O .000 50.170 86.720 *** Subbasin Connection Summary *** *** By -Pass Area Connection Summary *** No By -Passed Areas in Watershed Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 1 K:\proj ect\3 0700 \3 07 84 \WaterRes\MGS\Tacoma\Tacoma_noSR3\Tacoma_noSR3short.rtf loft MGSF1ood Analysis Tacoma Power Easement Outfall Tr (Years) Discharge (cfs) Node No: 1 ***********Water Quality Facility Data ******** Basic Wet Pond Volume (91 % Exceedance): 433449. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 650173. cu-ft 2-Year Discharge Rate : 21.543 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 11 15 cfs Off-line Design Discharge Rate (91% Exceedance): 6.40 cis Computed Flow Splitter Data Orifice Diameter: 9 00 inches Baffle Wall Height (WQ Design Depth): 8.47 feet Baffle Wall (Weir) Length. 5.96 feet (71.5 inches) Ratio: WQ Depth/Orifice Diameter: 11.3 (>=2 PASS) * *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) ** 2-Year 21.543 2-Year 21.543 5-Year 26.223 5-Year 26.223 10-Year 32.581 10-Year 32.581 25-Year 39.895 25-Year 39.895 50-Year 47.357 50-Year 47.357 100-Year 51.251 100-Year 51.251 200-Year 59.746 200-Year 59.746 Record too Short to Compute Peak Discharge for These Recurrence Intervals Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped'/Q2 (Must be Less Than 0%): Maximum Excursion from %Q2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS 0.0% PASS 0.0% PASS 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS K:\project\30700\30784\WaterRes\MGS\Tacoma\Tacoma_noSR3\Tacoma_noSR3short.rtf 2 of 2 MGSFIood Analysis Sherwood North • MGS FLOOD PROJECT REPORT Program Version: 3.09 Run Date: 11/29/2006 8:25 AM Input File Name. Sherwood_N.fld Project Name. Sherwood Creek North Basin Analysis Title: Sherwood Creek Basins SP010 and SF010 Comments• Sherwood Creek subbasins SP010 and SF010. Looked up long. and lat. online. Requires RC and WQ ********** Precipitation Input***"****** Extended Precipitation Timeseries Selected Climatic Region Number: 7 Full Period of Record Available used for Routing Precipitation Station : 950056 Puget West 56 in MAP 10/01/1939-10/01/2097 Evaporation Station : 951056 Puget West 56 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** Number of Subbasins: 1 ***Tnbutary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasin Total Subbasin 1-------=----> Node 1 ********** Watershed Definition'"'******** ********** Subbasin Number: 1 ********** Predeveloped 20.140 3.460 6.020 8.020 0.000 3.370 5.430 5.710 52.150 Area(Acres) --------------------- -----------Deve loped----- ..... To Node 3.820 3.930 16.850 0.000 0.000 7.120 3.250 17.180 52.150 Bypass Node o aoa 0 000 0 000 0 000 0 000 0 000 O 000 O 000 0.000 *** Subbasin Connection Summary*** *** By -Pass Area Connection Summary *** No By -Passed Areas in Watershed U pstream Node No. Node 1 ***Postdeveloped Node Connection Summary*** Link Type Downstream Node Pond Node 2 P redeveloped Compliance Node: Postdeveloped Compliance Node: 1 2 K:\project\30700\30784\W aterRes\MGS\Sherwood_N\SherN_short.rtf 1 of MGSF1ood Analysis Sherwood North Link No. 1, Pond: North Pond Postdeveloped Structure Summary*" Upstream Node : 1, Downstream Node: 2 Prismatic Pond Option Used Pond Floor Elevation Riser Crest Elevation Max Pond Elevation • Max Storage Depth Pond Bottom Length Pond Bottom Width Pond Side Slopes Pond Bottom Area Area at Riser Crest El Volume at Riser Crest Area at Max Elevation Vol at Max Elevation Hydraulic Conductivity Depth to Water Table Riser Geometry Riser Structure Type Riser Diameter Common Length Riser Crest Elevation 100.o0ft 102.90ft 104.00ft 2.90 ft 480.0 ft 210.0 ft L1= 3.00 L2= 3.00 W1= 3.00 W2= 3.00 ft/ft 100800. sq-ft 113,109. sq-ft 2.597 acres : 309,997. : 7.117 : 117936. 2.707 acres : 437,024. : 10.033 0.00 100.00 : Circular : 36.00 in : 0.900 ft : 102.90 ft Hydraulic Structure Geometry Number of Devices: 2 --Device Number 1 -- Device Type Invert Elevation Diameter Onentation Elbow : Circular Orifice : 100.00 ft : 8.90 in : Horizontal : No -- Device Number 2 --- Device Type : Vertical Rectangular Orifice Invert Elevation : 101.10 ft Length Height Orientation Elbow : 11.10 in : 23.50 in : Vertical :No cu-ft ac-ft sq-ft cu-ft ac-ft in/hr ft Postdeveloped Water Surface Elevation Data (ft) Recurrence Interval Computed Using Gnngorten Plotting Position Tr (yrs) Link: 1 1.05-Year 1.11-Year 1.25-Year 2.00-Year 3.33-Year 5-Year 10-Year 25-Year 50-Year 100-Year 100.663 100.774 100.921 101.314 101.563 101.741 102.096 102.381 102.719 102.794 K:\prof ect\30700\30784\W aterRes\MGS\Sherwood_N\SherN_short.rtf 2 of 3 MGSF1ood Analysis Sherwood North Tr (Years) Discharge (cis) Postdeveloped Infiltrated Water Statistics Volume Statistics Computed for Entire Simulation Statistic Linkt 1 Total Inflow Volume (ac-ft) Total Volume Infiltrated (ac-ft) Percent Infiltrated Node No: 1 20850. 0. 0.00 % ***********water Quality Facility Data ************* Basic Wet Pond Volume (91% Exceedance): 193100. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 289650. cu-ft 2-Year Discharge Rate : 8.795 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91 % Exceedance): 4.37 cfs Off-line Design Discharge Rate (91% Exceedance): 2.46 cfs Computed Flow Splitter Data Orifice Diameter: 6.25 inches Baffle Wall Height (WQ Design Depth): 5.37 feet Baffle Wall (Weir) Length: 5.56 feet (66.7 inches) Ratio: WQ Depth/Orifice Diameter: 10.3 (>=2 PASS) Node No: 2 Basic Wet Pond Volume (91 % Exceedance). 156776. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 235164. cu-ft 2-Year Discharge Rate : 2.712 cfs ***********Compliance Point Results ************* Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) ** 2-Year 5-Year 10-Year 25-Year 50-Year 4.480 6.621 8.182 10.489 12.676 100-Year 13.841 200-Year 14.259 Record too Short to Compute Peak 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Discharge for These 2.712 4.150 5.492 7.396 8.467 8.971 9.821 Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped'/2Q2 (Must be Less Than 0%): Maximum Excursion from Y%Q2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): -6.7% PASS -2.8% PASS -14.0% PASS 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS K:\project\30700\30784\WaterRes\1vIGS\Sherwood N\SherN_short.rtf 3 of MGSFIood Analysis Sherwood South MGS FLOOD PROJECT REPORT Program Version: 3.09 Run Date: 11/29/2006 8:56 AM Input File Name: Project Name. Analysis Title: Comments: Sherwood_S.fld Sherwood Creek South Basin Sherwood Creek Basins SP020,030 & 5E020,030 Sherwood Creek subbasins SP020,030 & SF020,030. Looked up long. and lat. online. Requires RC and WQ ********** Precipitation Input********** Extended Precipitation Timeseries Selected Climatic Region Number: 7 Full Period of Record Available used for Routing Precipitation Station 950056 Puget West 56 in MAP 10/01/1939-10/01 /2097 Evaporation Station : 951056 Puget West 56 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User)*************** ********** Watershed Definition ********** Number of Subbasins: 1 **********Subbasin Number: 1* ***Tnbutary to Node: 1 ***Bypass to Node : None Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasin Total Subbasin 1------------> Node 1 Predeveloped 11.890 0.940 1.580 3.080 0.000 0.970 2.150 0.520 21.130 Area(Acres) -----------Developed To Node 1.180 1.220 5.310 0.000 0.000 2.470 0.800 10.150 21.130 ** Bypass Node O .000 0.000 O .000 O .000 O .000 O .000 O .000 O .000 O .000 ***Subbasin Connection Summary*** *** By -Pass Area Connection Summary*** No By -Passed Areas in Watershed *** Postdeveloped Node Connection Summary*** Upstream Node No. Link Type Downstream Node Node 1 Pond Node 2 Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 2 IC: \pro;ect\30700\30784\WaterRes\MGS\Sherwood_S\SherS_Short.rtf 1 of MGSF1ood Analysis Sherwood South *** Postdeveloped Structure Summary*** Link No. 1, Pond: South Pond Upstream Node : 1, Downstream Node: 2 Prismatic Pond Option Used Pond Floor Elevation Riser Crest Elevation Max Pond Elevation Max Storage Depth Pond Bottom Length Pond Bottom Width Pond Side Slopes Pond Bottom Area Area at Riser Crest El Volume at Riser Crest Area at Max Elevation Vol at Max Elevation Hydraulic Conductivity Depth to Water Table Riser Geometry Riser Structure Type Riser Diameter Common Length Riser Crest Elevation : 100.00ft : 103.00ft : 104.00ft 3.00 ft : 400.0 ft : 200.0 ft : Lis 3.00 L2= 3.00 W1= 3.00 W2= 3.00 ft/ft : 80000. sq-ft : 91,124. sq-ft . 2.092 acres : 256,505. cu-ft : 5.889 ac-ft : 94976. sq-ft : 2.180 acres : 349 524. cu-ft : 8.024 ac-ft 0.00 in/hr 100.00 ft : Circular : 30.00 in : 0.410 ft : 103.00 ft Hydraulic Structure Geometry Number of Devices: 2 ---Device Number 1 Device Type invert Elevation Diameter Orentation Elbow : Circular Orifice : 100.00 ft : 4.50 in : Horizontal : No — Device Number 2 — Device Type : Vertical Rectangular Orifice Invert Elevation : 101.50 ft Length : 4.50 in Height : 18.02 in Orientation : Vertical Elbow : No *** Post -Developed Link Statistics *** Postdeveloped Water Surface Elevation Data (ft) Recurrence Interval Computed Using Gringorten Plotting Position Tr (yrs) Link: 1 1.05-Year 1.11-Year 1.25-Year 2.00-Year 3.33-Year 5-Year 10-Year 25-Year 50-Year 100-Year 100.861 100.950 101.044 101.533 101.775 101.996 102.336 102.520 102.845 102.905 K:\project\30700\30784\WaterRes\MGS\Sherwood_S\SherS_Short.rtf 2 of 3 MGSF1ood Analysis Sherwood South Postdeveloped Infiltrated Water Statistics Volume Statistics Computed for Entire Simulation Statistic Link: 1 Total Inflow Volume (ac-ft) Total Volume Infiltrated (ac-ft) Percent Infiltrated Node No: 1 9600. 0. 0.00 % ***********water Quality Facility Data ************* Basic Wet Pond Volume (91% Exceedance): 92437. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 138655. cu-ft 2-Year Discharge Rate : 4.469 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 2.35 cfs Off-line Design Discharge Rate (91% Exceedance): 1 35 cfs Computed Flow Splitter Data Orifice Diameter: 5.00 inches Baffle Wall Height (WQ Design Depth) 3 93 feet Baffle Wall (Weir) Length: 3.84 feet (46.1 inches) Ratio: WQ Depth/Orifice Diameter: 9.4 (>=2 PASS) Node No: 2 2-Year Discharge Rate : 0.677 cfs ***********Compliance Point Results ************* Predeveloped Compliance Node: 1 Postdeveloped Compliance Node: 2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Tr (Years) Discharge (cfs) Postdevelopment Runoff Tr (Years) Discharge (cfs) ** 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Record too Short 1.304 2.073 2.560 3.332 3.844 4.520 4.587 to Compute Peak 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Discharge for These 0.677 1.114 1.587 2.212 2.464 2.585 2.599 Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped %Q2 (Must be Less Than 0%): Maximum Excursion from %Q2 to Q2 (Must be Less Than 0%): Maximum Excursion from 02 to Q50 (Must be less than 10%): Percent Excursion from Q2 to Q50 (Must be less than 50%): 7.2% -4.0%a -1.0% 3.6% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS PASS PASS PASS K:\prof ect\30700\30784\WaterRes\MGS\Sherwood_S\SherS_Short.rtf 3of3 MGSFIood Analysis Unnamed Channel MGS FLOOD PROJECT REPORT Program Version: 3.09 Run Date: 11/29/2006 8:55 AM Input File Name. UnnamedTrib.fld Project Name: Unnamed Channel Basins 010 and 015 Analysis Title: Unnamed Channel Basin 010 and 015 Comments- Rate Control for Unnamed Channel Basins 010, and 015. PreDev and Dev land use. Looked up long. and lat. online. Requires RC and WQ ********** Precipitation Input********** Extended Precipitation Timeseries Selected Climatic Region Number: 7 Full Period of Record Available used for Routing Precipitation Station 950056 Puget West 56 in MAP 10/01/1939-10/01/2097 Evaporation Station : 951056 Puget West 56 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** Number of Subbasin: 1 ***Tnbutary to Node: 1 ***Bypass to Node : 3 Till Forest Till Pasture Till Grass Outwash Forest Outwash Pasture Outwash Grass Wetland Impervious Subbasizx Total S ubbasin 1 - - --> Node 1 • ********** Watershed Definition ********'*"' ***t****" Subbasin Number: 1 ********** Developed---- ----- Predeveloped To Node Bypass Node 23.880 0.930 3 080 9.110 0.930 8.390 7.610 8.560 11.110 1.500 0.000 0.000 O .000 0.000 0.000 O .480 0.640 0.000 O .000 0.000 0.000 2.710 7.140 4.510 45.290 18.200 27.090 *** Subbasin Connection Summary*** *** By -Pass Area Connection Summary *** Subbasin 1: By -Pass 27.090 Acres to Node 3 *** Postdeveloped Node Connection Summary*" U pstream Node No. Link Type Downstream Node Node 1 Copy Node 2 P redeveloped Compliance Node: 1 Postdeveloped Compliance Node: 2 *** Postdeveloped Structure Summary*** Link No. 1, Copy U pstream Node : 1, Downstream Node: 2 Copy Upstream to Downstream Node • K: \project\3 07 00\3 07 84\W aterRes\MGS\Unnam edTrib\Unn amed_short. rtf 1 of MGSFIood Analysis Unnamed Channel ***********water Quality Facility Data ************* Node No: 1 Basic Wet Pond Volume (91% Exceedance): 76221. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 114331. cu-ft 2-Year Discharge Rate : 3.614 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 1.71 cfs Off-line Design Discharge Rate (91% Exceedance): 0.96 cfs Computed Flow Splitter Data Orifice Diameter: 4.50 inches Baffle Wall Height (WQ Design Depth): 3.06 feet Baffle Wall (Weir) Length 4.93 feet (59.1 inches) Ratio: WQ Depth/Orifice Diameter: 8.2 (>=2 PASS) Node No: 2 Basic Wet Pond Volume (91 % Exceedance): 76221. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume. 114331. cu-ft 2-Year Discharge Rate : 3.614 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On line Design Discharge Rate (91% Exceedance): 1.71 cfs Off-line Design Discharge Rate (91 % Exceedance): 0 96 cfs Computed Flow Splitter Data Orifice Diameter: 4 50 inches Baffle Wall Height (WQ Design Depth): 3.06 feet Baffle Wall (Weir) Length: 4.93 feet (59.1 inches) Ratio: WQ Depth/Orifice Diameter: 8.2 (>=2 PASS) Node No: 3 Basic Wet Pond Volume (91% Exceedance): 93300. cu-ft Computed Large Wet Pond Volume, 1.5*Basic Volume: 139950_ cu-ft 2-Year Discharge Rate : 3.456 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance)• 1 49 cfs Off-line Design Discharge Rate (91 % Exceedance): 0.84 cfs Computed Flow Splitter Data Orifice Diameter: 4 00 inches Baffle Wall Height (WO Design Depth): 3.73 feet Baffle Wall (Weir) Length: 4.25 feet (51.0 inches) Ratio: WQ Depth/Orifice Diameter: 11 2 (>=2 PASS) ***Point of Compliance Flow Frequency Data *** Recurrence Interval Computed lJsing Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ** 2-Year 5-Year 10-Year 25-Year 50-Year 100-Year 200-Year Record too Short 3.316 2-Year 5.310 5-Year 7.166 10-Year 9.064 25-Year 10.762 50-Year 11.474 100-Year 12.192 200-Year to Compute Peak Discharge for These 3.614 4.820 6.029 7.817 8.914 9.285 11.020 Recurrence Intervals **** Flow Duration Performance According to Dept. of Ecology Criteria **** Excursion at Predeveloped %Q2 (Must be Less Than D%): Maximum Excursion from'AAQ2 to Q2 (Must be Less Than 0%): Maximum Excursion from Q2 to Q50 (Must be less than 10%): Percent Excursion from Q2 to 050 (Must be less than 50%): -46.0% -42.2% -37.1% 0.0% PASS * POND MEETS ALL DURATION DESIGN CRITERIA: PASS PASS PASS PASS K:\project\30700\30784\WaterRes\MGS\UnnamedTrib\Unnamed short.rtf 2 of 2 Land Use Data to w (a,a;(OrON00 ru) W 7 N W W (O (O nrN CO (o pi O pi < r (O i- h 1- W 0 (o) 0 w CO o co r i o o 0 0 0 o O 4.85 5E020 I uN) O r0u)(q)f Co 0 r N 0 0) 0 CI 0 N O. info aiui o06cri(dCd +7170r 0 w 4) O o 0 0 0 0 0 0 0.00 0 CO N 0 0 iu ua 1. 196'L cop CO Iso'L W CO 7 LO 9i V r r 50.94 I 06033 C n opN C 0 N 0 COO 0 N r ! OD c i o on O 6O(Or o j EE080 Cn r1O CO6 rrrr mh LO NV 0) Q.) N 0 0 CO )p r EE070 N cq QV 0 N 0 to N N N r R N CD CDN O S S o 8 w 0 t r'Nto O V r o 0 0 0 O O r< r w O O w at r Tr N 0 uO)O 0 0 NCEO00 0 0 CO 6 F- o (Oaio 66 •cr-000 OIO �'CO NO a) co1) o 1 vi r O w Ili EE042 ID mr- 0 18.47 O.W 0 0.22I O N m 0 m N r N V to N O 7.82 rr 0 N 13.821 0000co N a 8 w w I I EF01O I EE015 I EE020 1 EE025 I EE030 1 ((OOON N N N-O M O O OO I 20.46 r C'i CO 0 0 oo o fD r 7 CO 0nr la CO ro M Cob r co Nm CO O 0 O O 0 79.36' IU! I H13LC YUKI N 0 NN CO N. 0.341 (OQOO (O Oi N r N 0 r M r CO I+ N N rIDCOv00000 Y ill 3-1 r r A (O waC: H S Irig t_ .a0 43 m D F D 1 Y .. r I j ) O 71 O N co W > H Wednesday, 11/22/06 vrn3wo10+CO)IOI N CO OD o O O N V N CO m O 1- Q r o O (0 W 000000000 O O N O U. W to � it;C4 O o N- O O W O (0 O r N O 70,00 CO Oi0 o 7NO ISM a) N O O u. .0oOOOOo0oog m m x 0 N J O(NM N o O 0 6 O O r n(V t o m o it w o m 0 w n r o 0 m o 0 o Q 0 o o 0 co r 0 O N 0 N r 2.481 W C 0 o CO. O. O CD I (j O O h N w EF070 I 000000000 O 0 0a 0 0 0 0 0 0 0 0 00 6 0 LL w O 0 N O O� CO O O r- 0 O 0 0 cD o 0 LL w in 00000000 0 - 0 a 8 LL w N 000000000 00'0 CD U. W OOiO�6 r-N co CO O (7 O CIr04 O O o (d 0 00 'Cl- O U. M 111 to 0 LL w (r00 C6 m Pi 0 00000 1 0£0: O p N CCV r 0 0 0 0 0 0 06 O O 0 N. w N6OOr0.i00 0 LL w N 0) ) ^CO N 00 M co 6 V't CO CO O w (O O) en O](Or 0 N 00000 V C? Q rr =0 C N LO 0 00 0.641 0 18.201 r N za _w 0 o,— o 0 0 0 21.781 > A Ti p 66r o ro u r. 1. w - d_ EFhH000co5 l9 n Y ' — PERLND Data for basins requiring rate control. Predeveloped areas modeled as forest. Data modifications are shown in red. Basin North of Creek Existing r'A -4< _rEs,` Fut-Ex _ SE010 t 7 Difference y I y y 11.47 - Imp 5.71 s :;- :' TI1I-F 20.14 - ` 7_,�-t' -16.32 4 0.47- Till-P 3.46 ; Till-G 6.02 - w. o �: 10.83 ,'""l'" tiM ' Out-F 6.12" -6.12 v.m.., IL Out-P 1.9 r` ii'rs✓?n s sue. -1.9'' :d�;�aj�0.9r ;fk` .a"tu. :a Out-G 3.37"* 1.57 • - 3' , >ore 6 ° Sat 5.43%_ 0 gw-ataijz Water 0 =,fl 0 : _ __ Totals 52 15 _naW . '�,'" 9 N-' Swapped 0.04 ac TIII-P from N to S to make existing and future areas the same. Swapped 2.18 from Out-G to Sat b/c saturated won't become unsaturated. Difference with (-) sign shows what needs to be shown as forest in the Pre-Dev. Moved 1.9 ac from Out-P to Out-F for PreDev. South of Creek Existing =1?'• Fut-Ex ,T,w_ :u fn SE020 SE030 SE Total re S 2 03, Difference ,m4 0* 0.52 9.634:?=• Imp 0.52 0 Till-F 8.11 3.78 11.89 g_ lt'Iti -10.71 J ` 1 18 Till-P 0.94 0 0.94 ;a z r 0.28 ;amp. Till-G 1.58 0 1.58 W==i-;-• 3.73 t/ 0 2.51 # -2.51 Out-F 2.51 ;w x Out-P 0.57 0 0.57 _- w .s.::::; -0.57*. 17"- �-l� a• _ Out-G 0.97 0 0.97 :- s._'' ====0.15 ---..Q.,, �w Sat 1.08 1.07 2.15 .... -._. 1' _.: °""; 0;fi Water _.,.._ o r^3;«t��fwwa • Totals 16.28 4.85 21.13 tom_,°:r -- = i 2 - M:r_:....:.. ='µ Swapped 0.04 ac from N to S to make existing and future areas the same. SF030 is 0 00 ac Swapped 1.35 from Out-G to Sat b/c saturated won't become unsaturated. Difference with (-) sign shows what needs to be shown as forest in the Pre -Rev. Moved 0.57 ac from Out-P to Out-F for PreDev. K:1project1307001307841WaterRes\MGS\PERLND_Data.xls, Sherwood E -. U Y Q) L2 2 C T. To- o -0 C E to 2 ca co CO Q) CD ® J DC IMO -..•at-fi r .. :l • R. r :_ti^ C Cl.) es. i`t�5. a— Ott i?��', ..Erca. If- t Fr _ use. t C'4Xs.:'...- t - Difference 'ttNr- V'.(Omy-tpCflOb x OO NOMne'- LLl QOOiONO Ns" O B 11.651 4.01 O O O co .t 45.2' O 45. (A O) O 1 r Co jug' : o:sr`. T.IVv."..TY� .}' ^' .tS. .CC.M r n- Future ZSt:e L YY. h' . �itFT 7ArY9- '[Y..':C I� 4Sr ce:aa;o Yr-t, '�n'}SG G .11 _ x'T . a ^Z - », zr mat Pe - r 114443 0* ~ m, tt4.. N'3 tit '.. C. (:ma;S fit[ laM.�Y �L::ATh. [ 0 r 0 Co Co 0 0 0 0 Q} L CO LC) CO tC) 0 r6') NCO{ OQtCI OO))0OC)00(0 O InrC0000 r O LL w O l---. r OD CO r00000 L0OOrm. v ri m r N 60.da Water 0 0 0 Totals 21.79 23.50 45.29 Future - Existina 1 EE010 1 EE015 11 Subtotal O r co r r d- (D CO l'•-• OD r CO CO r V N CO CA t� O r O N CO cO CO r r cD CO O - •-4- O) N C\f C')) r (O T• tt) O r O A 6 r to C)'t O O O O o r O t'7 N r (D r D r 5 3 7 3) :o LLn0LLdC? ILEkkk00®tn v K:\project\30700\30784\WaterRes\MGS\PERLND_Data.xls, UnNamed Proposed New Direct Discharge Outfalis -*Without SR-3 improvements PERLND data is modified (in red) to remove the assumption that SR-3 ROW will be developed to 90% impervious. SR-3 ROW is removed because it is a State highway (not County) and will require enhanced water quality treatment. County roads/ROW in Allyn have low enough traffic volumes that basic water quality treatment is adequate. Land use was modified in the following manner: 1) Determine the area of SR-3 ROW in each basin with proposed regional WQ treatment 2) Impervious: remove 0.9*SR-3 area and replace with 0.53*SR-3 area (0 53 for 60' ROW) 3) Grass: remove 0.1 *SR-3 area and replace with 0.47*SR-3 area (0.47 for 60' ROW) Replacement percentages are based on 2, 12 lanes with 4' shoulders (32'wide impervious) The percent impervious is the impervious width divided by ROW width ROW W(ft) % grass 47% % Imp 60 53% 100 32% 68% 135 24% 76% Kayak Park Outfall EF080 Kayak* Imp 10.24 9.460 TIII-F 1.27 1.27 Till-P 2.48 2.48 TIII-G 4.85 5.630 Out-F 0.8 0.8 SR-3 Area 1.528065 ac Remove 1.375 ac. Imp 0.153 ac. Till-G Replace 0.595041 ac. Imp 0.933023 ac. TIII-G Out-P 0 67 0 67 Out-G 5.28 5.28 Sat 0 0 Water 0 0 Totals 25.59 25.59 Tacoma Power Easement Outfall EF010 EF020 EF025 Total Power* SR-3 Area 3.047521 ac Remove 2.743 Imp Imp 4.51 33.96 12.82 51 29 50. / 7 0.305 ac. ac. Till-G Till-F 3.08 1.49 0.64 5 21 5.21 Till-P 3.08 1.35 0.64 5.07 5.07 Till-G 11.11 12.31 1.31 24.73 25.85 Replace 1.625344 1.422176 ac. Imp ac. Till-G Out-F 0 0 0.15 0.15 0.15 Out-P 0 0 0.15 0.15 0.15 Out-G 0 0 0.12 0.12 0.12 Sat 0 0 0 0.00 0.00 Water 0 0 0 0.00 0.00 Totals 21.78 49.11 15.83 86.72 86.72 K:1project1307001307841WaterRes\MGS\PERLND_Data.xis, Direct (ROW) 5 of 7 Wade Street Outfall EF030 EF035 Total Wade* SR-3 Area 2.076446 ac 3.57 43 59 42.829 Imp 40.02 TiII-F 1.26 0 1.26 1.26 Remove 1.869 0.208 ac. ac. Imp Till-G TiII-P 1.26 0 1.26 1.26 Till-G 7.08 0.4 7.48 8.241 Out-F 0.03 0 0.03 0.03 Replace 1.107 Imp 0.969 ac. ac. Till-G Out-P 0.03 0 0.03 0.03 Out-G 0.02 0 0.02 0.02 Sat 0 0 0.00 0 Water 0 0 0.00 0 Totals 49.70 3.97 53.67 53.67 Evans St. / Lake! nd Drive Outfall EF040 EF050 Total Evans* SR-3 Area 1.188 ac Imp 39.75 29.07 68 82 68.38 Till-F 10.26 0 10.26 10.26 Remove 1.069 0.119 ac. ac. Imp Till-G Till-P 15.88 0 15.88 15.88 Till-G 30.86 0.72 31.58 32.02 Out-F 0 0 0.00 0 Replace 0.634 ac. Imp Out-P 0 0 0.00 0 0.554 ac. Till-G Out-G 0.12 0.79 0.91 0.91 Sat 0.06 0.08 0.14 0.14 Water 0 0 0.00 0 Totals 96.93 30.66 127.59 127.59 K:lproject1307001307841WaterRes\MGSIPERLND_Data.xls, Direct (ROW). 6 of 7 Shoreline Subbasins Existing Landuse - Allyn UGA RESULTANT PERLND/TABLE FORMAT EE090 EE100 Totals Imp 0.47 9.7 10.17 TiII-F 0.19 7.36 7.55 TiII-P 0.16 3.65 3.81 TiII-G 0.27 7.03 7.3 Out-F 0.23 6 2 6.43 Out-P 0.59 4.89 5.48 Out-G 1.23 6 7.23 Sat 0.69 4.36 5.05 Water 0 1.75 1.75 3.83 50.94 54.77 Totals Future Landuse - Allyn UGA RESULTANT PERLND/TABLE FORMAT EF090 EF100 Total Imp 1.73 32.29 34.02 Till-F 0 0 0 TiII-P 0 0 0 Till-G 0.31 9.02 9.33 Out-F 0 0 0 Out-P 0 0 0 Out-G 1.42 7.12 8.54 Sat 0.37 2.54 2.91 Water 0 0 0 3.83 50.97 54.80 Totals Sum of Existing Till Sum of Ex Outwash Sum of Future Till Sum of Fut Outwash 18.66 19.14 9.33 8.54 K:1project1307001307841WaterRes\MGS\FERLND_Data.xis, Shoreline Appendix D----Hydraulic Analysis EXISTING CULVERTS CROSSING SR3 IN ALLYN Culvert Capacity (culverts numbered from north to south Culvert# Type Inlet Capacity Use Location Diameter (cfs)* (cfs)** 1 18 CMP Headwall 8 8 N of Wade 2 12 Concrete Projecting 3 3 S of Wade 3 18 Concrete Projecting 10 10 N of Drum 4 18 Concrete Projecting 10 10 NI of Lakeland Dr 5 24 Concrete Projecting 18 18 S of Lakeland Dr 6 24 ? Projecting 15 to 18 16 N of Steve 7 24 ? Headwall 16 to 17 16 S of Steve 8 18 ? Projecting 8 to 10 8 Kayak Park 9 12 Concrete Projecting 3 3 Kayak Park 10 18 ? ? 8 to 10 8 S of Kayak Park Sum of Existing Culvert Capacity*** 100 Note: This assumes all culverts are in good condition and clean of debris *Capacity is calculated assuming inlet control with a 25yrHW/D ratio of 1.25 **Used the lower of the two estimates when pipe type or inlet were unclear ***This does not include the culverts crossing E North Bay Rd at the north end of the UGA ANTICIPATED NEW DEVELOPMENT (vic. Lakeland Drive and Wheelwright) Based on conversations with Mason County, 120 new homes are anticipated to be built west of Wheelwright, near Lakeland Drive. The anticipated development density is approximately 4 units per acre. 120 new homes at 4homes/acre develops 30 acres. The following results from MGSFIood analysis are used to estimated the increased runoff from 120 houses. Acres Land Runoff (CFS) Runoff (CFS/10 acre developed, 25-yr 100-yr 25-yr 100-yr 10 TF 1.31 1.58 1.31 1.58 25.59 9.16 11.49 3.58 4.49 37% Imp. Increase in Runoff 10 Developed) 2.27 2.91 (per acres Acres of new development Rate of increase in 25-yr runoff Increase in 25-yr runoff 30 acres 2.27 CFS /10 ac 6.80 CFS Existing local capacity (culverts 4-7) 60.0 CFS Increase in 25-yr runoff / Existing local capacity 0.11 11 % of the existing capacity If the existing culverts are already at capacity, then the HW/D ratio will increase from 1.25 to 1.5. K.1project1307001307841WaterRes\CulvCapacity.xls to x v z DIAMETER 0 STANDARD C. M CHART.2 180 168 156 144 132 120 108 96 84 72 60 STRUCTURAL PLATE CIA, EXAMPLE D. 36 inehti (3.0 fnr) 04 66 cf HW 4 r1• 0 (Cher) 1.6 5.4 2.1 6-.3 2.2 6.6 eD IA tot - 3 (2) e. 5. - 4. 3. (3) 5 - 4. e 1.5 r co ac 54 / w w - I 0 0 - 10,000 8,000 - 6,000 - 5,000 4,000 - 3,000 2,000 1,000 800 - 600 500 - 400 300 soa = 200 _E 48o - 80 -� ary 40 / 1 6 5 / =f3 r 1 12 BUREAU OF PUBLIC ROADS JAN 1963 2 1.0 are 4.1 *TRANCE ;a1 `le TYPE ()1 PP-74 le Headwall Y Jr d� Prol,cting i Mitered to conform to slops To use score (2) or (3) projatl horitontally to scale (r), the4. u se straight inclined lino thr_agh O and 0 stales, or reverse is illustrated. 182 . 7 . 8 . 7 L 1.5 - 1.0 .8 . 6 . 5 • .5 HEADWATER DEPTH FOR C M PIPE CULVERTS WITH INLET CONTROL to w r 0 z 1- AMETER OF CULVE 180 168 156 144 132 120 108 96 1.0,000 81000 - 6,000 5,000 L 4,000 - 3,000 2,000 1,000 r- 800 84 - 600 500 72 - 400 300 vs 60 v 6 200 Ei 100 54 48 / ¢ O C60 w� 12 gc Eso EXAMPLE 0•42 inches (3.5 twt) 0.120 et* 11 ' 0 2.5 2.1 2.2 aD is fall NM hat awe 7.4 7.7 CHART 1 (1) (2) (3) 6. a 5 -5. - 4. 4. r r 6. 5. - 4. or 3. 3. Iwo - 2. 5' Odle with hradwail .14,,firifroove snit with htadwall 1' (Sy Groove and y i pralecting t3 ,� �,! _ f ; ,✓ To ua4 scats (2) or (3) pro)sct 5 r.' horizontally is seals Within use straight inclined Hal through D and 0 stales, or ratan* as illustrated. 2 r.o HEADWATER SCALES 2 53 REVISED MAY 1964 BUREAU Of PUBLIC RCL&03 JAN. 1963 181 2. !a - 1.5 DImMir .8 7 8 1.5 L 2. 1.5 - 1.0 ,_ 1.0 - .9 Imo -.7 . 9 . 8 min low .5 L▪ 5 HEADWATER DEPTH FOR CONCRETE PIPE CULVERTS WITH INLET CONTROL Appendix E—Construction Cost Estimates • Preliminary Cost Opinion - CIP #1A Evans Street Collection System MMM Project No::30784 Client Mason County File Name. UplandEvans.xls Date1/12/2007 Item No. Quantity Plan Unit Item Description Price Unit Estimated Cost GRADING 1 360 TON $15 $5,400 GRAVEL BORROW SURFACING 2 415 TON CRUSHED SURFACING TOP COURSE $125 $51,875 3 280 TON $125 $35,000 ASPHALT TREATED BASE 4 140 TON PAVEMENT ASPHALT CONCRETE CL B $200 $28,000 DRAINAGE 5 250 CY REGRADE EXISTING DITCH $30 $7,500 6 2,400 LF REINF. CONC. PIPE 12-INCH $45 $108,000 7 860 LF REINF. CONC, PIPE 18-INCH $55 $47,300 8 360 LF REINF. CONC. PIPE 24-INCH $75 $27,000 7 5 EA CATCH BASIN TYPE 1L $2,000 $101000 8 3 EA CATCH BASIN TYPE 2 48-INCH $4,000 $12,000 9 2 EA $6,000 $121000 CATCH BASIN TYPE 2, 60-INCH 10 34,000 SF SHORING OR EXTRA EXCAVATION CLASS B $1.00 $34,000 SUBTOTAL $378,075 $15,123 ESCALATION YEAR 2005 TO 2006 @ 4% SUBTOTAL $393,198 EROSION & SEDIMENT CONTROL 5% $19,660 TRAFFIC CONTROL 8% $31,456 CONTINGENCY 30% $117,959 SUBTOTAL $562,273 MOBILIZATION 10% $56,227 CONSTRUCTION SUBTOTAL (Rounded) $618,600 STATE SALES TAX 8.3% $51,344 ENGINEERING/LEGAUADMIN 25% $154,650 CONSTRUCTION MANANGEMENT 20% $123,720 PERMITTING 5% $30,930 PROJECT SUBTOTAL (Rounded) $979,300 2006 dollars TOTAL ESTIMATED PROJECT COST (Rounded) $980,000 Notes: 1. The above cost opinion is in 2006 dollars and does not include future escalation, financing, or O&M costs. 2. The order -of -magnitude cost opinion has been prepared for guidance in project evaluation from the information available at the time of preparation and for the assumptions stated. The final costs of the project will depend on actual labor and material costs, actual site conditions, productivity, competitive market conditions, final project scope and schedule, and other variable factors. As a result, the final project costs will vary from those presented above. Because of these factors, funding needs for individual projects must be scrutinized prior to establishing the final project budgets. K:\project\30700\307841Data\Cost\Final\UplandEvans.xls, Cost Est Quantity Cates - Evans St. Upland collection and conveyance system Pipe Excavation pipe dia (OD) pipe dia (0D) =1 2`ID trench width pipe = OD + 2° street repair width = trench width + 2' average depth to pipe invert total trench depth trench length Pavement Disturance Width trench excavation pipe area (using OD) pipe bedding trench backfill shoring Pavement Repair Pavement Disturbance VVidth Trench Length Assume half gets paved: HMA (2" thick) ATB (4" thick) And the other half gets CSTC: CSTC (6" thick) Ditch Re -Grading (assumes 6" off WP for length of ditch) Lenth (ft) 3150 feet 1.0 1.2 3.2 5.2 3.0 4.1 2400 5.2 area SF feet 1.5 1.8 3.8 5,8 3.5 4.7 860 5.8 area SF feet 2.0 2.4 4.4 6.4 4.0 5.2 360 6.4 area SF volume CF TON 13.1 1.1 9.1 1.3 196B0 12-in 5.2 2400 17.7 2.5 11.9 1.3 8000 1 B-in 5.8 860 22.9 4.5 14.8 1,3 3750 24-in 6.4 360 54,921 37,436 4,691 330.00 Streik.RepaU: ,Ariptite,E, or t4$2ve Tieichb[fn Ape ®eEdug add 8% s?:::4� `rtif r'3= arAz:5i if v' r. 356 'w.•f' r 'L•' �. 33944.4;-:' CF CF CF CY Ton add 10% W. 1040.0 415.7 192.0 61.0 126 138.60 F 4 2080.0 831.3 384.0 122.0 251 276.10 ':F 00 CF OF CF CY Ton add 10% ,. 3120.0 1247.0 576.0 183.1 376 413.60 is . -; r..e: v2; . , i-::.,- CY add 10% USE 233.33 256.67 250 00 i Area (sf) 2.0 K:\prolect\30700\30784\Data\Cost\FinailUplandEvans.xls, Quanity Calc Preliminary Cost Opinion - CIP #1 B Wade St. Collection System Project No.:30784 Client: Mason County File Name.UplandWade xis Date 1/12/2007 Item No. Quantity Plan Unit Item Description Price Unit Estimated Cost GRADING 1 1,200 TON GRAVEL BORROW $15 $18,000 SURFACING 2 1,360 TON CRUSHED SURFACING TOP COURSE $125 $170,000 3 900 TON ASPHALT TREATED BASE $125 $112,500 4 450 TON PAVEMENT ASPHALT CONCRETE CL B $200 $90,000 DRAINAGE 5 11,050 LF REINF. CONC. PIPE 12-INCH $45 $497,250 6 625 LF REINF. CONC. PIPE 18-INCH $55 $34,375 7 625 LF REINF. CONC. PIPE 24-INCH $75 $46,875 6 27 EA CATCH BASIN TYPE 1 L $2,000 $54,000 7 3 EA CATCH BASIN TYPE 2 48-INCH $4,000 $12,000 8 4 EA CATCH BASIN TYPE 2, SO -INCH $6,000 $24,000 9 111,200 SF SHORING OR EXTRA EXCAVATION CLASS B $1.00 $1111200 SUBTOTAL $1,170,200 ESCALATION YEAR 2005 TO 2006 @ 4% $46,808 SUBTOTAL $1,217,008 5% EROSION & SEDIMENT CONTROL $60,850 TRAFFIC CONTROL 8% $97,361 CONTINGENCY 30% $365,102 SUBTOTAL $1,740,321 MOBILIZATION 10% $174,032 CONSTRUCTION SUBTOTAL (Rounded) $1,914,400 STATE SALES TAX 8.3% $158,895 25% ENGINEERING/LEGAUADMIN $478,600 CONSTRUCTION MANANGEMENT 20% $382,880 PERMITTING 5% $95,720 PROJECT SUBTOTAL (Rounded) $3,030,500 2006 dollars TOTAL ESTIMATED PROJECT COST (Rounded) $33040,000 1 Notes: 1. The above cost opinion is in 2006 dollars and does not include future escalation, financing, or O&M costs. 2. The order -of -magnitude cost opinion has been prepared for guidance in project evaluation from the information available at the time of preparation and for the assumptions stated. conditions, final project The final costs of the project scope and schedule, and other will depend on actual labor and material costs, variable factors. As a result, the final project actual site conditions, productivity, competitive market costs will vary from those presented above. Because of these factors, funding needs for individual projects must be scrutinized prior to establishing the final project budgets. K:\project\30700\30784\Data\Cost\Final\UplandWade.xls, Cost Est Quantity Calcs - Wade Upland collection and conveyance system Pipe Excavation pipe dia (ID) pipe dia (OD) = 1.2*ID trench width pipe = OD + 2' street repair width = trench width ¢ 2' average depth to pipe invert total trench depth trench length Pavement Disturance Width trench excavation pipe area (using OD) pipe bedding trench backfill shoring Pavement Repair Pavement Disturbance Width Trench Length Assume half gets paved: HMA (2" thick) ATB (4" thick) And the other hall gets CSTC: CSTC (6" thick) feet 1.0 1.2 3.2 5.2 3.0 4.1 11050 5.2 area SF feet 1.5 1.8 3.8 5.8 3.5 4.7 625 5.8 area SF feet 2.0 2.4 4,4 6.4 4.0 5.2 625 6.4 area volume SF CF �-=sv atia.z's' TON 13.1 17.7 22.9 170,320 1.1 2.5 4.5 9.1 11.9 14.8 117,370 1.3 1.3 1.3 15,800 1,090.00 90610 5820 6500 12-in 5.2 11050 CF 4788.3 9576.7 CF 14365.0 CF CF 18-in 5.8 625 302.1 604.2 906.3 24-in 6.4 625 CF 333.3 666.7 CF 1000.0 CY 200.9 401.8 CY 602.6 Ton 412 824 Ton 1236 Slree reaad • trvaemdc Nitive Tre ich Biagi awe Bedtlin2 aei Excavtlion add 8% 1,177 111164.4 add 10% 453.20 906.40 add 10% 1,359.60 K1project\30700\307841Data\Cost\Final\UplandWade.xls, Quanity Calc Preliminary Cost Opinion - CIP #2 New Outfall at Evans Street Project No.:30784 Client: Mason County Date:1 /12J2007 Item No. Quantity Plan Unit Item Description Price Unit Estimated Cost GRADING 1 45 TON GRAVEL BORROW $15 $675 SURFACING 2 60 TON ASPHALT TREATED BASE $125 $7,500 3 30 TON $200 $6,000 PAVEMENT ASPHALT CONCRETE CL B {QTY, <500} DRAINAGE 4. 250 LF REINF. CONC. PIPE 42 INCH $170 $42,500 5 100 LF HDPE 42-INCH I.D. WATER SIDE IN TRENCH $510 $51,000 6 1 EA HDPE PIPE TERMINUS CONC. ANCHOR $1,000 $1,000 7 2 EA $6,000 $12,000 CATCH BASIN TYPE 2, 60-INCH 8 5,300 SF $1.00 $5,300 SHORING OR EXTRA EXCAVATION CLASS B SUBTOTAL $125,975 ESCALATION YEAR 2005 TO 2006 @ 4% $5,039 SUBTOTAL $131,014 5% $6,551 EROSION & SEDIMENT CONTROL TRAFFIC CONTROL 8% $10,481 CONTINGENCY 30% $39,304 SUBTOTAL $187,350 10% $18,735 MOBILIZATION CONSTRUCTION SUBTOTAL (Rounded) $206,100 STATE SALES TAX 8.3% $17,106 25% $51,526 ENGINEERING/LEGAL/ADMIN CONSTRUCTION MANANGEMENT 20% $41,220 PERMITTING 5% $10,305 PROJECT SUBTOTAL (Rounded) $326,300 2006 dollars i TOTAL ESTIMATED PROJECT COST (Rounded) $330,000 Notes: 1. The above cost opinion is in 2006 dollars and does not include future escalation, financing, or O&M costs. 2. The order -of -magnitude cost opinion has been prepared for guidance in project evaluation from the information available at the time of preparation and for the assumptions stated. The final costs of the project will depend on actual labor and material costs, actual site conditions, productivity, competitive market conditions, final project scope and schedule, and other variable factors. As a result, the final project costs will vary from those presented above. Because of these factors, funding needs for individual projects must be scrutinized prior to establishing the final project budgets. K:\project\30700\30784\Data\Cost\Final\Evans-pipe_r1. xls Outfall Est Quantity Calcs New Outfall at Evans Street Poe Excavation pipe dia (ID) pipe dia (OD)=1.2*ID trench width pipe = OD + 2' street repair width = trench width + 2' average depth to pipe invert total trench depth trench length Pavement Disturance Width trench excavation pipe area (using OD) pipe bedding trench backlit! shoring Pavement Repair Pavement Disturbance Width Trench Length Removal HMA (2" thick) ATB (4" thick) SF 2050 feet 3.5 4.2 6.2 8.2 5.5 6.9 350 8.2 area volume SF CF 42.5 14,865 13.8 24.6 8,607 0.9 325 4800 volume CY 560 TON 320 20 40.00 ovei ream, add 10% 42-in 82 250 (assumes all but the last 1001will be paved over) SY 228 CF CY 342 12.65 683 25.31 Ton add 10% Erzgasitgi 26 28.60 w tjyp 52 _f EipibulxiiteatS 57.20 K:\prolect130700\307841Data\Cost\Final\Evans-pipe_r1.xls, Outfall Cale Preliminary Cost Opinion CIP #2 Conveyance System to New Outfall at Evans Street Along SRProject No.:30784 Client: Mason County Date:1112/2007 Unit Item Description Price Unit Estimated Item No. Quantity Plan Cost GRADING 1 355 TON GRAVEL BORROW $15 $5,325 SURFACING 2 230 TON ASPHALT TREATED BASE $125 $28,750 3 155 TON $200 $31,000 PAVEMENT ASPHALT CONCRETE CL B {QTY, <500} DRAINAGE 4 1,400 LF REINF. CONC PIPE 18-INCH $55 $77,000 5 8 EA CATCH BASIN TYPE 2, 48-INCH $4,000 $32,000 6 15,900 SF SHORING OR EXTRA EXCAVATION CLASS B $1.00 $15,900 SUBTOTAL $189,975 ESCALATION YEAR 2005 TO 2006 @ 4% • $7,599 SUBTOTAL $197,574 EROSION & SEDIMENT CONTROL 5% $9,879 TRAFFIC CONTROL 8% $15,806 CONTINGENCY 30% $59,272 $282,531 SUBTOTAL MOBILIZATION 10% $28,253 CONSTRUCTION SUBTOTAL (Rounded) $310,800 STATE SALES TAX 8.3% $25,796 ENGINEERING/LEGAUADMIN 25% $77,700 CONSTRUCTION MANANGEMENT 20% $62,160 PERMITTING 5% $15,540 PROJECT SUBTOTAL (Rounded) $492,000 2006 dollars TOTAL ESTIMATED PROJECT COST (Rounded) $500,000 Notes: 1. The above cost opinion is in 2006 dollars and does not include future escalation, financing, or O&M costs. 2_ The order -of -magnitude cost opinion has been prepared for guidance in project evaluation from the information available at the time of preparation and for the assumptions stated. The final costs of the project will depend on actual labor and material costs, actual site conditions, productivity, competitive market conditions, final project scope and schedule, and other variable factors. As a result, the final project costs will vary from those presented above. Because of these factors, funding needs for individual projects must be scrutinized prior to establishing the final project budgets. K:\project\30700\30784\Data\Cost\Final\Evans-p ipe_r1.xls Convey Est Quantity Oaks 18-in conveyance system Evans Street Pipe Excavation pipe dia (ID) pipe dia (OD) = 1.21D trench width pipe = OD + 2' street repair width = trench width + 2' average depth to pipe invert total trench depth trench length Pavement Disturance Width trench excavation pipe area (using OD) pipe bedding trench backfill shoring Pavement Repair Pavement Disturbance Width Trench Length Removal HMA (2" thick) ATB (4" thick) feet 1.5 1.8 3.8 5.8 4.0 5.2 1400 5.8 area SF 19.6 2.5 11.9 3.2 14420 volume CF 27,398 16,655 volume CY 1,020 620 12" r r Wd.3 OOt25 ---1 TON eel Repair Wooded or Nava Trench Bacia Pipe Setting Over Excavation add 10°/ f5E 4,522 170 320.00 352.00 35600 15862 •15900: 18-in 5.8 1400 (assumes all but the last 100' will be paved over) SF 8120 SY 903 CF CY 1353.333 50.12 2707 100.25 add 10% 993.30 Ton add 10% 103 113.30 '' .' .'155A0 206 226.60 : <230300; K:\proiect130700\30784\Data\Cost\Final\Evans-pipe_rl.xls, Convey Cale Preliminary Cost Opinion - CIP #2 Water Quality Treatment for New Outfall at Evans Street Project No.:30784 Client' Mason County Date:1/12/2007 Item No. Quantity Plan Unit Item Description Unit Price Cost Estimated DRAINAGE 1 608,335 CF WATER QUALITY TREATMENT WET POND $2.30 $1,399,171 SUBTOTAL $1,399,171 ESCALATION YEAR 2005 TO 2006 © 4% $55,967 SUBTOTAL $1,455,137 EROSION & SEDIMENT CONTROL 5% $72,757 TRAFFIC CONTROL 8% $116,411 CONTINGENCY 30% $436,541 SUBTOTAL $2,080,846 MOBILIZATION 10% $208,085 CONSTRUCTION SUBTOTAL $2,289,000 (Rounded) STATE SALES TAX 8.3% $189,987 ENGINEERING/LEGAUADMIN 25% $572,250 CONSTRUCTION MANANGEMENT 20% $457,800 PERMITTING 5% $114,450 PROJECT SUBTOTAL (Rounded) $3,623,500 2006 dollars TOTAL ESTIMATED PROJECT COST (Rounded) $3,630,000 I Notes: 1. The 2. The the assumptions conditions, these factors, above cost order-oi-magnitude stated. final project funding opinion is in cost The final scope needs for 2006 dollars and opinion has been costs of the project and schedule, and individual projects does not include future escalation, financing, or prepared for guidance in project evaluation from will depend on actual labor and material costs, other variable factors. As a result, the final project must be scrutinized prior to establishing the final O&M costs. the information available actual site conditions, costs will vary from project budgets. at the time of productivity, presented preparation competitive above. and for market Because of those K:\project\30700\30784\Data\Cost\Final\Evans-pipe_rl.xls WQ Est Preliminary Cost Opinion - CJP #3 New Outfall at Wade Street Project No.:30784 Client: Mason County Date:1 /12/2007 r r Item No. Quantity Plan Unit Item Description Price Unit Estimated Cost GRADING $15 $675 1 45 TON GRAVEL BORROW SURFACING 2 50 TON ASPHALT TREATED BASE $125 $6,250 3 25 TON PAVEMENT ASPHALT CONCRETE CL B {QTY, <500} $200 $5,000 DRAINAGE 4 250 LF REINF. CONC. PIPE 30-INCH $106 $26,500 5 100 LF HDPE 30-INCH I.D. WATER SIDE IN TRENCH $318 $31,800 6 1 EA HDPE PIPE TERMINUS CONC. ANCHOR $1,000 $1,000 7 2 EA CATCH BASIN TYPE 2, 60-INCH $6,000 $12,000 8 4,400 SF SHORING OR EXTRA EXCAVATION CLASS B $1.00 $4,400 SUBTOTAL $87,625 ESCALATION YEAR 2005 TO 2006 © 4% $3,505 SUBTOTAL $91,130 EROSION & SEDIMENT CONTROL 5% $4,557 TRAFFIC CONTROL 8% $7,290 CONTINGENCY 30% $27,339 SUBTOTAL $130,316 MOBILIZATION 10% $13,032 CONSTRUCTION SUBTOTAL (Rounded) $143,400 STATE SALES TAX 8.3% $11,902 25% $35,850 ENGINEERING/LEGAL/ADMIN CONSTRUCTION MANANGEMENT 20% $28,680 PERMITTING 5% $7,170 PROJECT SUBTOTAL (Rounded) $227,100 2006 dollars TOTAL ESTIMATED PROJECT COST (Rounded) $230,000 i Notes: 1. The above cost opinion is in 2006 dollars and does not include future escalation, financing, or O&M costs. 2. The order -of -magnitude cost opinion has been prepared for guidance in project evaluation from the information available at the time of preparation and for the assumptions stated. The final costs of the project will depend on actual labor and material costs, actual site conditions, productivity, competitive market conditions, final project scope and schedule, and other variable factors. As a result, the final project costs will vary from those presented above. Because of these factors, funding needs for individual projects must be scrutinized prior to establishing the final project budgets. K:\project\30700\30784\Data\Cost\Final\Wade-plpe_rl.xls Outfall Est Quantity Cafes New Outfal) at Wade Street Pipe Excavation pipe dia (ID) pipe dia (OD) =1.2*ID trench width pipe = OD + 2' street repair width = trench width + 2' average depth to pipe invert total trench depth trench length Pavement Disturance Width trench excavation pipe area (using OD) pipe bedding trench backfill shoring Pavement Repair Pavement Disturbance Width Trench Length Removal HMA (2" thick) ATB (4" thick) SF 1750 5•.... feet 2.5 3.0 5.0 7.0 4.5 5.8 350 7 area volume volume SF CF CY 28.8 10,063 380 7.1 17.9 6 277 240 1.3 438 4030 TON 20 40.00 30-in 7 250 (assumes all but the last 1001 will be paved over) SY 195 CF CY 292 10.80 583 21.60 Ton 23 45 • inkintedor Nawc • TrOalDpckro o ®t Enamullon add 10% '.gfaikusEg 44.00TT10pQ- 4433 - ` Wt -.`Y M Alta. r m—x;> 1. add 1 0% ii,K2.ittftE,44 214.50 >E-�22£I)A _ �__.. : -_:. add 10"/" wlfS y 25.30 is rivet 49.50 Oft K:\project\307001307B4\Data\Cost\FinallWade-pipe_rl.xls, outfalt Calc Preliminary Cost Opinion » CEP #3 Conveyance System to New Outfall at Wade Street Along SR3Project No.:30784 Client: Mason County Date:1/12/2007 Price Unit Estimated Item Plan Cost No. Quantity Unit Item Description GRADING 1 210 TON GRAVEL BORROW $15 $3,150 SURFACING 2 310 TON ASPHALT TREATED BASE $125 $38,750 3 155 TON PAVEMENT ASPHALT CONCRETE CL B {QTY, <500} $200 $31,000 DRAINAGE 4 1,900 LF REINF. CONC. PIPE 18-INCH $55 $104,500 5 12 EA CATCH BASIN TYPE 2, 48-INCH $4,000 $48,000 6 19 400 SF SHORING OR EXTRA EXCAVATION CLASS B $1.00 $19,400 SUBTOTAL $244,800 $9,792 ESCALATION YEAR 2005 TO 2006 @ 4% SUBTOTAL $254,592 EROSION & SEDIMENT CONTROL 5% $12,730 TRAFFIC CONTROL 8% $20,367 CONTINGENCY 30% $76,378 SUBTOTAL $364,067 MOBILIZATION 10% $36,407 CONSTRUCTION SUBTOTAL (Rounded) $400,500 STATE SALES TAX 8.3% $33,242 ENGINEERING/LEGAL/ADMIN 25% $100,125 20% $80,100 CONSTRUCTION MANANGEMENT PERMITTING 5% $20,025 PROJECT SUBTOTAL (Rounded) $634,000 2006 dollars TOTAL ESTIMATED PROJECT COST (Rounded) $640,000 Notes: 1. The above cost opinion is in 2006 dollars and does not include future escalation, financing, or O&M costs. 2. The order -of -magnitude cost opinion has been prepared for guidance in project evaluation from Me information available at the time of preparation and for the assumptions stated. The final costs of the project will depend on actual labor and material costs, actual site conditions, productivity, competitive market conditions, final project scope and schedule, and other variable factors. As a result, the final project costs will vary from those presented above. Because of these factors, funding needs for individual projects must be scrutinized prior to establishing the final project budgets. K:\project\30700\30784\Data\Cost\Final\W ade-pipe_rl .xls Convey Est Quantity Calcs 18-in conveyance system Pipe Excavation pipe dia (ID) pipe dia (OD) = 1.2'ID trench width pipe = OD + 2' street repair width = trench width + 2` average depth to pipe invert total trench depth trench length Pavement Disturance Width trench excavation pipe area (using OD) pipe bedding trench backfill shoring Pavement Repair Pavement Disturbance Width Trench Length Removal HMA (2" thick) AT13 (4" thick) feet 1.5 1.8 3.8. 5.8 3.5 4.7 1900 5.8 area SF volume CF - H volume CY TON 17.7 33,573 1,250 2.5 11.9 22,604 840 1.3 2,527 100 17670 .: pnpwNetive ted. Tren<h backl0 • Ada over Excavation.. _ . add 10% eg3l$, 190.00 209.00 21i? 4f) 19437 FalAsalitT szz 18-in 5.8 1900 (assumes all but the last 100' will be paved o SF SY 11020 1225 CF CY 1836.667 68.02 3673 136.05 ver) add 10% 1,347.50 Ton add 10a/a �:aSE. 140 154.00._of 279 306.90 "• K:lproiect\307001307841Data\CoshFinal\Wade-pipe_rl .xls, Convey Calc Preliminary Cost Opinion - CIP #3 Water Quality Treatment for New Outfall at Wade Street Project No.:30784 Client: Mason County Date:1/1212007 Price Unit Estimated Cost Item Plan No. Quantity Unit Item Description DRAINAGE $2.30 $736,975 1 320,424 CF WATER QUALITY TREATMENT WET POND $736,975 SUBTOTAL ESCALATION YEAR 2005 TO 2006. © 4% $29,479 SUBTOTAL $766,454 EROSION & SEDIMENT CONTROL 5% $38,323 TRAFFIC CONTROL 8% $61,316 CONTINGENCY 30% $229,936 SUBTOTAL $1,096,030 10% $109,603 MOBILIZATION CONSTRUCTION SUBTOTAL (Rounded) $1,205,700 STATE SALES TAX 8.3% $100,073 ENGINEERING/LEGAUADMIN 25% $301,425 CONSTRUCTION MANANGEMENT 20% $241,140 PERMITTING 5% $60,285 (Rounded) $1,908,700 PROJECT SUBTOTAL 2006 dollars TOTAL ESTIMATED PROJECT COST (Rounded) $1,910,000 Notes: 1. The above cost opinion is in 2006 dollars and does not include future escalation, financing, or O&M costs. 2. The order -of -magnitude cost opinion has been prepared for guidance in project evaluation from the information available at the time of preparation and for the assumptions stated. The final costs of the project will depend on actual labor and material costs, actual site conditions, productivity, competitive market conditions, final project scope and schedule, and other variable factors. As a result, the final project costs will vary from those presented above. Because of these factors, funding needs for individual projects must be scrutinized prior to establishing the final project budgets. K:\project130700\30784\Data\Cost\Final\Wade-pipe_ri.xls WQ Est Preliminary Cost Opinion - CIP #4 New Outfall at Kayak Park Project No.:30784 Client Mason County Date:1/12/2007 Unit Item Description Price Unit Estimated Cost Item No. Quantity Plan GRADING 1 90 TON GRAVEL BORROW $15 $1,350 SURFACING 2 35 TON ASPHALT TREATED BASE $125 $4,375 3 17 TON $200 $3,400 CONCRETE CL B PAVEMENT ASPHALT {QTY, <500} DRAINAGE 4 250 LF $55 $13,750 REINF. CONC. PIPE 18-INCH 5 100 LF HDPE 18-INCH I.Q. WATER SIDE IN TRENCH $165 $16,500 6 1 EA $1,000 $1,000 HDPE PIPE TERMINUS CONC. ANCHOR 7 2 EA CATCH BASIN TYPE 2, 54-INCH $5,500 $11,000 8 3,400 SF B $1.00 $3,400 SHORING OR EXTRA EXCAVATION CLASS SUBTOTAL $54,775 ESCALATION YEAR 2005 TO 2006 @ 4% $2,191 SUBTOTAL $56,966 5% $2,848 EROSION & SEDIMENT CONTROL TRAFFIC CONTROL 8% $4,557 CONTINGENCY 30% $17,090 SUBTOTAL $81,461 MOBILIZATION 10% $8,146 CONSTRUCTION SUBTOTAL (Rounded) $89,700 STATE SALES TAX 8.3% $7,445 25% $22,425 ENGINEERING/LEGAUADMIN CONSTRUCTION MANANGEMENT 20% $17,940 PERMITTING 5% $4,485 PROJECT SUBTOTAL $142,000 (Rounded) 2006 dollars TOTAL ESTIMATED PROJECT COST (Rounded) $150,000 Notes: 1. The above cost opinion is in 2006 dollars and does not include future escalation, financing, or O&M costs. 2. The order -of -magnitude cost opinion has been prepared for guidance in project evaluation from the information available at the time of preparation and for the assumptions stated. The final costs of the project will depend on actual labor and material costs, actual site conditions, productivity, competitive market conditions, final project scope and schedule, and other variable factors. As a result, the final project costs will vary from those presented above. Because of these factors, funding needs for individual projects must be scrutinized prior to establishing the final project budgets. K:\project\30700\30784\Data\Cost\Finai\Kayak-ditch_rt .xls Outfall Est Quantity Cates New Outfall at Kayak Park Pipe Excavation pipe dia (ID) pipe dia (OD)=1.2*ID trench width pipe = OD + 2' street repairwidth = trench width+ 2' average depth to pipe invert total trench depth trench length Pavement Disturance Width trench excavation pipe area (using OD) pipe bedding trench backfill shoring Pavement Repair Pavement Disturbance Width Trench Length Removal HMA (2" thick) ATB (4" thick) SF 1160 CF feet 1.5 1.8 3.8 5.8 4.0 5.2 300 5.8 area volume volume SF CF CY TON 19.6 5,871 220 2.5 11.9 3,569 140 3.2 969 40 80.00 3090 add 10% 88.00 _ 33992 18-in 5.8 200 (assumes all but the last 100' will be paved over) SY 129 WI• rar••••.", „c?r al= add 10°l° ° ' 141.90 T is CY Ton add 10% 193 7.16 15 16.50 _..__. 387 14.32 30 33.00 ;t _ K:\project\30700130784\Data\Cost\Final\Kayak-ditch_rl.xls, Outtall Calc Preliminary Cost Opinion - CIP #4 Conveyance System to New Outfall at Kayak Park Along SR3 Project No.:30784 Client: Mason County Date:1/12/2007 Item No. Quantity Plan Unit Item Description Price Unit Estimated Cost DRAINAGE 1 120 CY REGRAIJE EXISTING DITCH $30 $3,600 SUBTOTAL $3,600 ESCALATION YEAR 2005 TO 2006 @ 4% $144 SUBTOTAL $3,744 EROSION & SEDIMENT CONTROL 5% $187 TRAFFIC CONTROL 8% $300 CONTINGENCY 30% $1,123 SUBTOTAL $5,354 MOBILIZATION 10% $535 CONSTRUCTION SUBTOTAL (Rounded) $5,900 STATE SALES TAX 8.3% $490 ENGINEERING/LEGAL/ADMIN 25% $1,475 CONSTRUCTION MANANGEMENT 20% $1,180 PERMITTING 5% $295 PROJECT SUBTOTAL (Rounded) $9,400 2006 dollars TOTAL ESTIMATED PROJECT COST (Rounded) $10,000 I Notes: I. The above cost 2. The order -of -magnitude the assumptions stated. conditions, final project these factors, funding opinion is in 2006 dollars cost opinion has been The final costs of the scope and schedule, needs for individual projects and project and other does prepared not include future escalation, financing, or for guidance in project evaluation from will depend on actual labor and material costs, variable factors. As a result, the final project be scrutinized prior to establishing the final O&M costs, the information available at the time of preparation actual site conditions, productivity, competitive costs will vary from those presented above, Because project budgets. and market for of must i K:\project130700130784\Data\Cast\Final\Kayak-ditch_rl.xls Convey Est Preliminary Cost Opinion - CIP #4 Water Quality Treatment for New OutfaII at Kayak Park Project No.:30784 Client: Mason County Date:1 /12/2007 Unit Estimated Item No. Quantity Plan Unit Item Description Price Cost DRAINAGE 1 89,734 CF WATER QUALITY TREATMENT WET POND $2.30 $206,388 SUBTOTAL $206,388 ESCALATION YEAR 2005 TO 2006 @ 4% $8,256 SUBTOTAL $214,644 EROSION & SEDIMENT CONTROL 5% $10,732 TRAFFIC CONTROL 8% $17,171 30% $64,393 CONTINGENCY SUBTOTAL $306,941 MOBILIZATION 10% $30,694 CONSTRUCTION SUBTOTAL (Rounded) $337,700 STATE SALES TAX 8.3% $28,029 ENGINEERING/LEGAUADMIN 25% $84,425 CONSTRUCTION MANANGEMENT 20% $67,540 PERMITTING 5% $16,885 PROJECT SUBTOTAL (Rounded) $534,600 1 2006 dollars TOTAL ESTIMATED PROJECT COST (Rounded) $540,000 Notes: 1. The above cost opinion is in 2006 dollars and does not include future escalation, financing, or O&M costs. 2. The order -of -magnitude cost opinion has been prepared for guidance in project evaluation from the information available at the time of preparation and for the assumptions slated. The final costs of the project will depend on actual labor and material costs, actual site conditions, productivity, competitive market conditions, final project scope and schedule, and other variable factors. As a result, the final project costs will vary from those presented above. Because of these factors, funding needs for individual projects must be scrutinized prior to establishing the final project budgets. K:\project\30700130784\Data\Cost\Final\Kayak-ditch_rl.xls WQ Est Preliminary Cost Opinion - CIP #5 New Outfall at Powerline Easement Project No.:30784 Client: Mason County Date:1/12/2007 Item No. Quantity Plan Unit Item Description Price. Unit Estimated Cost GRADING 1 90 TON $15 $1,350 GRAVEL BORROW SURFACING 2 150 TON $125 $18,750 ASPHALT TREATED BASE 3 75 TON $200 $15,000 PAVEMENT ASPHALT CONCRETE CL B {QTY, <500) DRAINAGE 4 700 LF REINF. CONC. PIPE 36-INCH $121 $84,700 5 100 LF $363 $36,300 HDPE 36-INCH I.D. WATER SIDE IN TRENCH 6 1 EA , $1,000 $1,000 HDPE PIPE TERMINUS CONC. ANCHOR 7 5 EA CATCH BASIN TYPE 2, 60-INCH $6,000 $30,000 8 11,100 SF SHORING OR EXTRA EXCAVATION CLASS B $1.00 $11,100 SUBTOTAL $198,200 $7,928 ESCALATION YEAR 2005 TO 2006 @ 4% SUBTOTAL $206,128 EROSION & SEDIMENT CONTROL 5% $10,306 TRAFFIC CONTROL 8% $16,490 CONTINGENCY 30% $61,838 SUBTOTAL $294,763 10% $29,476 MOBILIZATION (Rounded) $324,300 CONSTRUCTION SUBTOTAL STATE SALES TAX 8.3% $26,917 NEERING/LEGAUADMI N 25% $81,075 ENGI CONSTRUCTION MANANGEMENT 20% $64,860 PERMITTING 5% $16,215 PROJECT SUBTOTAL (Rounded) $513,400 2006 dollars i TOTAL ESTIMATED PROJECT COST (Rounded) $520,000 Notes: 1. The above cost opinion is in 2006 dollars and does not include future escalation, financing, or O&M costs. 2_ The order -of -magnitude cost opinion has been prepared for guidance in project evaluation from the information available at the time of preparation and for the assumptions stated. The final costs of the project will depend on actual labor and material costs, actual site conditions, productivity, competitive market conditions, final project scope and schedule, and other variable factors. As a result, the final project costs will vary from those presented above. Because of these factors, funding needs for individual projects must be scrutinized prior to establishing the final project budgets. K:\project\30700\30784\Data\Cost\Fi nal\Powe rli ne-ditch_rl .xls Outf all Est Quantity Calcs New Outfall at Poweriine Easement Pipe Excavation pipe dia (ID) pipe dia (OD)=1.21D trench width pipe = OD + 2' street repair width = trench width + 2° average depth to pipe invert total trench depth trench length Pavement Disturance Width trench excavation pipe area (using OD) pipe bedding trench backfill shoring Pavement Repair Pavement Disturbance Width Trench Length Removal I-IMA (2" thick) ATB (4" thick) feet 3.0 3.6 5.6 7.6 5.0 6.3 800 7.6 area volume volume SF CF CY TON • H SIieirRottw iawateaor;kM- Trench' lc(11 e .Ovei:Ex®vclen• add 10% n = w:-=:; ri ,ay: 'Ir Zi =**_ ::.. 88.0o Y*t}'-,rf __. .._ 11088i a:M ::.....�._ ^..Y c 1.2`!•s SF SY add 10% .t::'.rt 1 �r^ix 5320 592 651.20 `ki . .. t:; ;;i l CF CY Ton add 10% glitzySERE 887 32.84 68 74.80 s _ 1773 65.68 135 148.50 Ct;150i0_; ....•,.,4 35.3 28,224 1,050 10.2 21.2 16,949 630 1.1 896 40 80.00 10080 36-in 7.6 700 (assumes all but the last 100' will be paved over) K:lproject\307001307841DatalCost\Final\Powerline-ditch_rl.xls, Outfall Calc Preliminary Cost Opinion - CIP #5Conveyance System to New Outfall at Powerline Easement Ali, cji3Bt 0784 North Bay Road Client: Mason County Date:1/12/2007 Unit Estimated Item Plan Price Cost No. Quantity Unit Item Description DRAINAGE 1 700 CY REGRADE EXISTING DITCH $30 $21,000 SUBTOTAL $21,000 ESCALATION YEAR 2005 TO 2006 ® 4% $840 SUBTOTAL $21,840 EROSION & SEDIMENT CONTROL 5% $1,092 TRAFFIC CONTROL 8% $1,747 CONTINGENCY 30% $6,552 SUBTOTAL $31,231 MOBILIZATION 10% $3,123 CONSTRUCTION SUBTOTAL (Rounded) $34r400 STATE SALES TAX 8.3% $2,855 25% $8,600 ENGINEERING/LEGALJADMIN CONSTRUCTION MANANGEMENT 20% $6,880 5% $1,720 PERMITTING PROJECT SUBTOTAL (Rounded) $54,500 2006 dollars 1 I I TOTAL ESTIMATED PROJECT COST (Rounded) $60,000 Notes: 1. The above cost opinion is in 2006 dollars and does not include future escalation, financing, or O&M costs. 2. The order -of -magnitude cost opinion has been prepared for guidance in project evaluation from the information available at the time of preparation and for the assumptions staled. The final costs of the project will depend on actual labor and material costs, actual site conditions, productivity, competitive market conditions, final project scope and schedule, and other variable factors. As a result, the final project costs will vary from those presented above. Because of these factors, funding needs for individual projects must be scrutinized prior to establishing the final project budgets. K:\project130700130784\Data\Cost\Final\Poweriine-ditch_r1.xls Convey Est Prepared by sherin 1/12/2007 Page 1 Item Plan Unit Estimated No. Quantity Unit Item Description Price Cost DRAINAGE TREATMENT WET POND $2.30 $996,933 1 433,449 CF WATER QUALITY SUBTOTAL $996,933 ESCALATION YEAR 2005 TO 2006 r0 4% $39,877 SUBTOTAL $1,036,810 EROSION & SEDIMENT CONTROL 5% $51,841 TRAFFIC CONTROL 8% $82,945 CONTINGENCY 30% $311,043 SUBTOTAL $1,482,638 MOBILIZATION 10% $148,264 CONSTRUCTION SUBTOTAL (Rounded) $1,631,000 STATE SALES TAX 8.3% $135,373 ENGINEERINGILEGAL/ADMIN 25% $407,750 CONSTRUCTION MANANGEMENT 20% $326,200 PERMITTING 5% $81,550 PROJECT SUBTOTAL (Rounded) $2,581,900 2006 dollars TOTAL ESTIMATED PROJECT COST (Rounded) $2,590,000 I Notes: 1. The above cost opinion is in 2006 dollars and does not include future escalation, financing, or O&M costs. 2. The order -of -magnitude cost opinion has been prepared for guidance in project evaluation from the information available at the time of preparation and for the assumptions stated. The final costs of the project will depend on actual labor and material costs, actual site conditions, productivity, competitive market final factors. As the final from those Because conditions, project scope and schedule, and other variable a result, project costs will vary presented above. of these factors, funding needs for individual projects must be scrutinized prior to establishing the final project budgets. K:\project130700\30784\Data\Cost\Final\Powerline-ditch_ri.xls WQ Est a) O N 0 c O C N (.Q OOt(70 (D CO N c CO 098 LO N (0 O O r C l0017Z 0 O O 0 . N r r r *Ditch 1 O O O O LO - el CO c CO O O OO O0 '- C) r C O o Outfall 1 Along SR3 (I N r O O 0�0. 10 v 0 b 181 42 O O C CO E 0 Thai *tool 1001 O O EE (LI r 'Conc. (LF)l 250 OOL N O Location 1 Y Evans 1 ePeM Jemodi CO 0 0 Co N W a) D O) 0 c a) J O) c O Cd e c N C a) 0 ik) > Q) .O Q) C O E O a) N as a) ..o C_ 0) 0) C 0 C 0 O s 0 c (o cvl N Co n c TO. CQ U) W 0 c c O 5 To C ▪ < • c > Q) n.a) E U7 • O 6.0 LL Q) u) O at C6 Ca) to O i i-1 c C-- 0o a) UT TES ( -Cica a) c 0 a) c c - J c o N N D L a) U) D K:\project\30700\307841Data\Cost\FinaRTakeoff.xls, Convey This page is used to calculate a cost ($/CF water quality) Calculations are done based on a water quality facility that fits on a 1 acre lot Length (ft) Width (ft) Area (sf) Area (ac) *Elev Lot Lines 200 218 43600 1.00 0 Toe 190 208 39520 0.91 0 of slope Top of slope 184 202 37168 0.85 1 Top of slope 178 196 34888 0.80 1 WQ WSE 172 190 32680 0.75 0 154 172 26488 0.61 -3 Top of Sediment Bottom of Sediment 148 166 24568 0.56 -4 *Elevation 0 is the ground surface. Negative is cut, Positive is fill. Site Clearing 1 Acre at Volume Cut (average end area method) Area at surface (sf) Area at bottom (sf) Average area (sf) Depth (ft) Volume Volume Fill (average end Area at (sf) Area at surface (sf) Average area (sf) Depth (ft) Volume 25% for compaction Wet Pond Seeding Seeding 32680 24568 28624 4 4,241 CY Cut 4,300 CY Cut at area method) 2280 6840 4560 1 169 CY Cut 42 CY Cut 300 CY Cut 32680 SF at 10920 SF at 1,200 per acre costs $ $ 20.00 per CY t excavatow7 orn> Si rQG4... .. - r:=• 0[IOGY costs 1,200 86,000 Sno.Co_Fd,_._r_':Portd berrxis:is $:12 3/tgn (a(i4.:•Qn/GYah0 $22 :7:Sit :Men;--2006 0.:* ; . : Fdl andtoinpac bin-:6".lifts_r:.:.:: $ 23.00 per CY Water Quality Volume (average end area method) Area at surface (sf) 32680 Area at bottom (sf) 26488 Average area (sf) 29584 Depth (ft) 3 Volume 88,752 CF 88,800 CF costs $ 6,900 2.00 , per SF costs $ 65,360 1,00 , per SF costs $ 10,920 Total Cost $ 170,380 oopno:500: regula seed r g.eosts:per .: SnoCo data: ($2,59:an - SO 64 tekOectively).. Unit Price $ 1.92 per CF of Water Quality Treatment $ 0.38 20% contingency $ 2,30 per CF of Water Quality Treatment K:1project1307001307841Data\Cost\Final\Takeoff.xls, WQ Appendix F---Suggested Scope for Culver.t./_Outfall. inventory an.d Analysis Appendix F Su__ested Scope for Culve utfall Invento and Analysis The continued use of the existing ten culverts/outfall pipelines under SR3, currently draining the East Drainage Basin of the Allyn UGA, should be coordinated WSDOT. A field investigation, as stated earlier in Section 6, is needed to define the condition and capacity of the existing SR3 culverts, pipelines, and outfalls. With this information, alternative facihties to serve the East Uplands Area can be developed and compared. The scope of this SR3 culvert/outfall pipeline investigation should include the following: • Perform research at WSDOT to try to obtain additional as -built information on the culverts/outfalls. • Request right -of -entry permission to allow investigation on private properties. • Visit expected outfall terminal sites at low tide to verify their locations; perform survey and establish size and condition. • Determine pipeline/structure conditions by video camera or other techniques. • Perform a hydraulic analysis of each culvert/outfall pipeline to determine its capacity at high tide design conditions. • Estimate the remaining life/replacement schedule for each culvert/outfall pipeline, assuming a 40-year planning period for new facilities. • Summarize the findings and recommendations resulting from the investigation in a technical memorandum. Upon completion of the outfall investigation, it is recommended that outfall alternatives be developed compared, and documented in a technical memorandum. Key information in the memorandum would include: • Maximum potential of the existing culvert/outfall system to serve the East Uplands. • Definition of detention needed using only the existing outfall system. • Development and comparison of two to four alternatives using combinations of existing and/or new outfalls, detention as requited, and water quality treatment facilities. • Property acquisition and construction/maintenance easement requirements should be defined. Schematics esttmates of implementation costs, and anticipated permitting requirements should be presented for each proposed capital improvement. After selection of a preferred alternative by Mason County, a project schedule would be prepared Following approvals and funding, implementation of the project could begin. K:\project\30700\30784\Reports\Allyn SWf IP Update\Appendices\AppendixF.doc Table 1 EXISTING CULVERTS CROSSING SR3 IN ALLYN from north to south Culvert # Diameter Type Inlet Capacity (cfs)* Use (cfs)** Location 1 18 CMP Headwall 8 8 N of Wade 3 3 S Wade 2 12 Concrete Projecting of Concrete Projecting 10 10 N of Drum 3 18 10 N Lakeland Dr 4 18 Concrete Projecting 10 of 5 24 Concrete Projecting 18 18 S of Lakeland Dr 6 24 ? Projecting 15 to 18 16 N of Steve 7 24 ? Headwall 16 to 17 16 S of Steve 8 18 ? Projecting 8 to 10 8 Kayak Park 9 12 Concrete Projecting 3 3 Kayak Park 10 18 ? ? 8to10 8 SofKayakPark Sum of Existing Culvert Capacity*** 100 Note: This assumes all culverts are in good condition and clean of debris *Capacity is calculated assuming inlet control with a 25yrHW/D ratio of 1.25 **Used the lower of the two estimates when pipe type or inlet were unclear ***This does not include the culverts crossing E North Bay Rd at the north end of the UGA ANTICIPATED NEW DEVELOPMENT (vic. Lakeland Drive and Wheelwright) Based on conversations with Mason County, 120 new homes are anticipated to be built west of Wheelwright, near Lakeland Drive. The anticipated development density is approximately 4 units per acre. 120 new homes at 4homes/acre develops 30 acres. The following results from MGSFlood analysis are used to estimated the increased runoff from 120 houses. Runoff (CFS) Runoff (CFS/10 acre developed) Acres Land 25-yr 100-yr 25-yr 100-yr 10 TF 1.31 1.58 1.31 1.58 4.49 25.59 37% imp. 9.16 11.49 3.58 Increase in Runoff (per 10 acres Developed) 2.27 2.91 Acres of new development Rate of increase in 25-yr runoff Increase in 25-yr runoff 30 acres 2.27 CFS /10 ac 6.80 CFS Existing local capacity (culverts 4-7) 60.0 CFS Increase in 25-yr runoff / Existing local capacity 0.11 11 % of the existing capacity If the existing culverts are already at capacity, then the HW/D ratio will increase from 1.25 to 1.5. K:\pro)ect\30700\30784\Reports\Aliyn SWMP Update\Appendices\F_CulvertCapacity\CuivCapacity.xls APPendix G—Preliminary Analysis of Exiting Culvert Capacity Appendix G: Preliminary Analysis of Existing Culvert Capacity According to the County (S. Goins, Personal Communication, 12-14-06), the anticipated grown in the Allyn UGA is forecasted to be 50 residential units per year, 60-percent of which will be located within the LakeLand Village Development (Mason County phone call). The County anticipates the remaming residential development (about 120 residential units over the next 6 years) to be concentrated west of East Wheelwright Street, on either side of East Lakeland Drive; development may extend as far north as East Sellegren Road and as far south as the south end of Wheelwright. There are four existing culverts crossing SR3 in the proposed future development area within the East Drainage Basin mentioned above. There are three, 24-inch culverts south of Lakeland Dr. and one, 18-inch culvert north of Lakeland Dr Existing culvert capacity was calculated assuming inlet control, and used a Headwater\Diameter ratio of 1.25 during the 25-year design storm The combined capacity of these four culverts is 60 CFS (assuming culverts are clean and operating at design capacity) The development of 120 new houses in this area would generate an increase in runoff of 6.8 CFS during the 25-year design storm. The existing runoff conveyed by the four culverts was not calculated. A new outfall at E Evans St. (east of Lakeland Dr.) is not recommended during the six year planning phase of this report. The culverts may currently have capacity to convey the increase in runoff without increasing the HW\D ratio above 125. In order for the four culverts to convey 66.8 CFS (60+6.8=66.8CFS) the HW\D ratio raises to 1.5. Note. This analysis assumes the existing culverts are operating at a HW\D ratio of 1.25. If the existing culverts are currently operating at a HW\D ratio higher than what is assumed, increasing the runoff may cause stormwater to overtop SR3 Thus, no new pipes are needed within the next six years, assuming 10% of the original design capacity remains in the existing pipes. K:\project\30700\30784\Reports\Allyn S\V'IP Update\Appendices \AppendixG.doc EXISTING CULVERTS CROSSING SR3 IN ALLYN Culvert Capacity (culverts numbered from north to south Culvert # Diameter Type Inlet Capacity (cfs)* Use (cfs)** Location 1 18 CMP Headwall 8 8 N Wade of 2 12 Concrete Projecting 3 3 S of Wade 3 18 Concrete Projecting 10 10 N of Drum 4 18 Concrete Projecting 10 10 N of Lakeland Dr 5 24 Concrete Projecting 18 18 S of Lakeland Dr 6 24 ? Projecting 15 to 18 16 N of Steve 7 24 ? Headwall 16 to 17 16 S of Steve 8 18 ? Projecting 8 to 10 8 Kayak Park 9 12 Concrete Projecting 3 3 Kayak Park 10 18 ? ? 8to10 8 SofKayakPark Sum of Existing Culvert Capacity*** 100 Note: This assumes all culverts are in good condition and clean of debris *Capacity is calculated assuming inlet control with a 25yrHW/D ratio of 1.25 **Used the lower of the two estimates when pipe type or inlet were unclear ***This does not include the culverts crossing E North Bay Rd at the north end of the UGA ANTICIPATED NEW DEVELOPMENT (vic. Lakeland Drive and Wheelwright) Based on conversations with Mason County, 120 new homes are anticipated to be built west of Wheelwright, near Lakeland Drive. The anticipated development density is approximately 4 units per acre. 120 new homes at 4homes/acre develops 30 acres. The following results from MGSFIood analysis are used to estimated the increased runoff from 120 houses. Acres Land Runoff (CFS) Runoff (CFS/10 acre developed) 25-yr 100-yr 25-yr 100-yr 10 TF 1.31 1.58 1.31 1.58 9.16 11.49 3.58 4.49 25.59 37% Imp. Increase in Runoff (per 10 acres Developed) 2.27 2.91 Acres of new development Rate of increase in 25-yr runoff Increase in 25-yr runoff 30 acres 2.27 CFS /10 ac 6.80 CFS Existing local capacity (culverts 4-7) 60.0 CFS Increase in 25-yr runoff / Existing local capacity 0.11 11 % of the existing capacity If the existing culverts are already at capacity, then the HW/D ratio will increase from 1.25 to 1.5. K:\project\30700\30784\Reports\Allyn SWMP Update\Appendices\F_CulvertCapacity\CulvCapacity.xls