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HomeMy WebLinkAboutWetland Restoration Plan - PLN General - 10/19/2004 WETLAND RESTORATION PLAN FOR LOT 3 OF SHORT PLAT 2436 BEAR CREEK DEWATTO ROAD BELFAIR Mason County, Washington ���► Parcel No. 12309-31-90073 Prepared For: Connie Wurm 4294 Siana Place SE Port Orchard, WA 98366 Prepared By: Wiltermood Associates, Inc. 1015 SW Harper Road Port Orchard, WA 98367 (360) 876-2403 October 19 2004 TABLE OF CONTENTS PAGE INTRODUCTION 1 SITE CONDITIONS 2 PROPOSED IMPROVEMENTS AND RESTORATION 3 RESTORATION PLAN OVERVIEW 4 Grading Plan 4 Planting Plan 4 Objectives of the Wetland Restoration Plan 6 Goals of the Wetland Restoration Plan 6 Performance Standards 6 MONITORING PLAN 7 MAINTENANCE PLAN 8 CONTINGENCY PLAN 8 PERFORMANCE BONDS 9 INTRODUCTION This restoration plan has been prepared for the wetland and buffer impacts to a Category III wetland on the 1.25 acre parcel located on Bear Creek-Dewatto Road, Belfair, Mason County, Washington. This parcel is Lot 3 of Short Plat No. 2436. The wetland and buffer were inadvertently cleared and graded during site development preparations on the level portion of the site. The clearing and grading were conducted without a permit from the Mason County Department of Community Development and so it is in violation of the Critical Areas Ordinance. Mason County is requiring a wetland and buffer restoration plan that repairs the impacts while still allowing construction of a single family home on this platted lot. The wetland cannot be restored successfully within the entire impact area so the restoration plan will entail creation of a small area of wetland as well as restoration of a portion of the impact area with planting to re-establish the lost vegetative cover. The wetland lies around the south and east edges of the property beginning at the base of moderately steep slopes to the east. The wetland is slightly higher in elevation than the graded area along the south edge so that when grading was completed, a cut was created and the wetland was exposed along the cut bank. Prior to impact, the wetland was part of a larger system that extends off-site to the south and east and is determined to meet the criteria for a Category III system. Because the entire impacted area of wetland cannot be successfully restored in the area of impact, creation of roughly 1,600 square feet is proposed in the area of the existing curtain drain to compensate for the loss of wetland area. There is 680 square feet of impacted wetland that will be restored just north of the created wetland area. Because the site is composed of steep slopes and wetland with buffer, the cleared building envelope is the only area available for homesite construction and is well within the buffer of the Category III wetland. The buffer will be reduced to 37.5 feet from the wetland east of the building site but will need to be reduced to zero next to the created and restored wetland areas. This buffer reduction must proceed through the variance process of the Mason County Critical Areas Ordinance. Because a buffer cannot be accommodated from the wetland west of the cleared building pad, a wood fence is proposed along the new wetland boundary and will provide additional protection for the created and restored wetland area. The wetland creation and restoration plan will entail excavation of a roughly 1,600 square feet area of upland along the curtain drain to replace wetlands lost by clearing and grading and restoration (through plant installation) of a roughly 680 square foot area of impacted wetland. Both areas will be planted with red osier dogwood, black twinberry and Pacific willow in clumps with western red cedar planted around the wetland shrub clumps and Douglas fir will be planted in the upland portion of the buffer. The fir trees will act as a screen between the future home and the wetland areas. Monitoring will be conducted for a period of three years to track the progress of the installed plants and regular weed removal will be required to ensure that the installed plants are not negatively impacted by the growth of non-natives. Maintenance will also include watering the installed plants on a weekly to bi-weekly basis through the summer months. A performance bond will be set up to ensure that the plants are installed as required and to ensure that monitoring and maintenance activities are conducted over a period of three years. SITE CONDITIONS This 1.25 acre parcel is part of a 4 lot short plat (Short Plat No. 2436) with homes on the three other lots. This parcel remains undeveloped but has been cleared and graded to create a level building site at the south end. It is irregular in shape and consists of a long narrow, 137 foot wide arm that widens out in the southern half to roughly double that width. The arm is too narrow to accommodate a home so it will be used mainly to access the wider area, which is the proposed building site. The building site area was examined by Geotechnical Testing Lab of Olympia in February 2003, which is prior to the clearing and grading. They described the building site as being "...located in the level portion of the upper area, where the slopes are between 0% and 15%. The steeper slope are confined to the northern and eastern portion of the lot where the steep to between 30 and 45 percent. This area is outside the proposed building area." Their general site description includes "The site is vegetated with fir, hemlock, maple and cedar trees. A moderate to dense understory consists of grass, brush, young alder trees, salal and Oregon grape with local areas of blackberry. Evidence of a small surface water flow was observed in the eastern portion of the site at the time of our reconnaissance. The general topography of the site area indicates that the site drains towards the east." They go on to describe the slopes as very stable with no indication of erosion concerns and indicate that there was no need for a building setback from the top of the slope because it is so stable. The building site was cleared and graded following approval of the septic design and entailed removal of material to create a level building pad. The clearing and grading took place in an area roughly 157 feet long by 64 feet wide at the south end with a curtain drain along the base of the cut slope. The road was in place prior to all site activities and was not included in the clearing and grading activities. The remainder of the parcel retains the forested communities on the sloping terrain described by Geotechnical Testing Labs in February 2003. The wetland boundary was delineated on both sides of the cleared building pad for purposes of determining the areas of restoration. The delineation revealed that a narrow strip of wetland crossed the building pad prior to disturbance, which is supported by the observation of evidence of a small surface water flow observed on the eastern portion of the system by Geotechnical Testing Labs during their site examination in February 2003. This is also supported by the post-impact photos showing a narrow flow of water from the cut bank on the west side of the buildingad. After the delineation was completed, Kristen P French and Rick Mraz from Mason County Department of Community Development visited the site with Bob Wiltermood and Vaughn Everitt of Wiltermood Associates and confirmed the boundary delineation. The wetland was originally determined to be a Category I mature 2 forest but during the delineation, Wiltermood Associates determined that the wetland actually meets the Category III criteria. The Category III determination was supported by Rick Mraz of Mason County during the post delineation site visit. PROPOSED IMPROVEMENTS AND RESTORATION Due to site constraints, there is only one building site plan that will allow construction of a single family home on this 1.25 acre parcel. The site plan prepared by the septic system designer specifies installation of a drainfield on the slope just below the access road and the well situated next to the proposed home at the south end so that there is at least 100 feet between the two areas. The design has been approved by the Mason County Health Department. The Geotechnical Testing Labs have determined that the slope is stable enough that a slope setback should not be required for the home so the home is actually proposed at the top of the slope. The home has also been sited to permit a turn around next to the home, which is also constrained by both the slopes up to the north and down to the south. A variance is necessary to achieve the reduced buffer and it should be stressed once again that there is no alternative building envelope available on this site. The proposed mitigation and restoration plan works to preserve a building site on the property while also compensating for the inadvertent impacts to the on-site Category III wetland. The creation of wetland is proposed to compensate for the roughly 800 square feet of wetland that crossed through the building site (as described previously) and cannot be restored without eliminating the only buildable area. Wetland will be created along the west edge of the building site (where the curtain drain is currently installed) and will utilize the curtain drain as a source of hydrology. The area of creation will be long and narrow so that it follows the curtain drain and will roughly encompass an area 1,600 square feet. There is a 680 square foot area of disturbed wetland that remains and this area will be restored as part of the overall plan. A buffer is not possible from the created and restored wetland along the cleared building pad due to other site constraints including slope and the 100 foot well radius, which necessitates using the area along the existing driveway for the drainfield. To indicate the presence of the created/restored wetland, a wood fence that is at least 16 inches off the ground (lowest rail of a horizontal fence is at least 16 inches from the ground) will be installed along the edge of the wetland area. A 37.5 foot buffer is proposed between the off-site wetland to the east and the top of the on-site slope (edge of cleared building pad). A portion of the narrow disturbed wetland (about 400 square feet) lies within this buffer and the area of wetland creation includes compensation for this area of wetland impact. Restoration and mitigation will entail installation of plant species within the respective wetland areas with no buffer restoration to take place except along the north and south edges of the cleared building pad. The entire buffer from the off-site wetland is not being restored because most of it remains well vegetated with a young red alder community. 3 RESTORATION PLAN OVERVIEW The restoration plan proposes to create a -4,600 square foot area and restore -680 square feet of wetland to compensate for -800 square feet of disturbance to the on-site Category III wetland system while allowing for construction of a single family home. The creation of wetland will involve removing the rock and pipe from the existing curtain drain to an appropriate elevation, installation of topsoil and will be followed up by planting native trees and shrubs in the created and restored wetland and portions of the on-site wetland buffers. Grading Plan A formal grading plan showing proposed created wetland elevations has not been prepared because this is a single family project and a topographic survey is not available. There is a topographic map that was prepared by Geotechnical Testing Lab that is used to describe the topography of the mitigation area in general terms but it is not used to determine the created wetland elevations because it is not related to the existing and disturbed areas of wetland. The topographic survey indicates that the building site is essentially level with a very gradual slope up from east to west. The existing wetland areas lie across this slope but is not situated along any one contour line, which is another reason why the final grades cannot be determined as part of this mitigation plan. The grading of the site will be conducted under the close supervision of the project biologist who will determine the final elevation of the created wetland using the water level within the existing curtain drain as a control. To create the wetland, the curtain drain, which is somewhere between 1.5 and 3 feet deep, will be exposed so that the gravel and pipe can be removed and filled with a topsoil to the final wetland grade. The final wetland grade will lie between 6 and 12 inches below the upper curtain drain elevation depending on the depth of water revealed when the curtain drain is removed. The topsoil will be placed in the drain to achieve the final wetland grade. No erosion control measures (straw bales and/or silt fences) will be necessary because the area is situated within a level area that lies below the actual grade of the impacted wetland so there is little chance of imposing additional impacts to the disturbed wetland. Planting Plan The planting plan proposes installation of the 110 plants listed below with the shrubs installed mostly in clumps of 12 with smaller clumps in the narrow created and restored wetland areas with western red cedar trees between the shrub clumps. Douglas fir trees will be planted north and south of the cleared building site where they will supplement the existing vegetation and provide additional screening for the off-site areas of wetland. Herbaceous plants are not being installed because there is a good seed source within the undisturbed wetland areas and we expect them to readily spread into the created and restored wetland. The table below list the plants selected for installation in the created and 4 restored wetland areas with the number of plants to be installed, common and botanical names, and spacing. Plant size and location of the plants are shown on the attached AutoCAD drawing generated for this project. Wetland Plant List Number Common Name Botanical Name Spacing 12 Red osier dogwood Cornus stoloni era 4-6' on center 24 Black twinberry Lonicera involucrata 4-6' on center 24 Pacific willow Salix lasiandra 5-7' on center 18 Western red cedar Thuja plicata As shown on design 32 Douglas fir Pseudotsuga menziesii As shown on design Each of the plants on the lists above were selected because they do well in restoration areas, are native to this area of Mason County and many were observed in un-impacted areas adjacent to the site. The shrub species were selected because they can also be installed as 36 to 48 inch long cuttings that will take root once the growing season begins. Otherwise, the plants will be installed as 1 gallon size potted/bareroot plants and each plant should be between 18 and 24 inches tall. Installation should take place after the start of the dormant season (October 151' to March 151'') while the plants are not actively growing and so that they are in place by the start of the growing season but they can be installed prior to the end (October 15") or after the start (March 15`') of the growing season if they are regularly watered and cared for. In general, the plants will be laid out randomly by hand in their respective clumps as indicated on the planting plan and not measured out by string line. A two to three foot diameter hole should be dug prior to removal of the plant from the pot and the plug should be placed immediately into the ground once the soil around the plug is loosened. The hole will then be backfilled with the dug out soil and loosely packed down around the plug. The project biologist will be on-site to supervise the excavation of the created wetland to ensure the final wetland grade is appropriate to site conditions. The biologist will also supervise installation of the specified plants to ensure the proper placement of the specified plants. Each of the plants will be flagged with brightly colored survey ribbon so they can be seen easily during review of the plant installation and during future monitoring/maintenance activities. An as built report shall be prepared once the plants have been installed to inform Mason County that the restoration plan has been implemented. It will mention whether or plants were substituted for something else (if a specified plant is not available) and will include photos taken immediately after plant installation. The as built report should be submitted to Mason County DCD within 2 to 3 weeks of plant installation. 5 I Objectives of the Wetland Restoration Plan 1. Remove curtain drain to ---1,600 square feet of wetland in order to compensate for the disturbance to and loss of -�800 square feet of wetland across the cleared building pad. 2. Improve vegetation cover by planting cedars and shrubs in the created wetland with Douglas fir in the buffer north and south of the building pad. 3. Facilitate construction of a single family home on the cleared building pad with reductions to the wetland buffers to the north and south. Goals of the Wetland Restoration Plan The main goal of this mitigation and restoration plan is to compensate for the loss of wetland caused by clearing and grading of the only on-site buildable area. Creation is being proposed at 2:1 ratio because restoration of wetland cannot be conducted without eliminating the building site. Additional restoration is proposed in a -680 square foot area of wetland remaining after the impact so the project proposes a final ratio of 2.85:1 as compensation for the inadvertent disturbance to the on-site wetland. The goal of plant installation in the wetland is to establish a trend toward the development of a forested- scrub/shrub community so that the created and restored wetland represents the pre-impact wetland area. The goal of the buffer planting is to provide additional screening of the off- site areas of wetland that supplements the existing vegetation. The success of the restoration goals will be judged using the following performance standards: The area should have at least 50% cover by the native installed and volunteer plants that are at least 5 feet tall; there will be 90% survival of the installed plants over the entire three year monitoring period; and less than 15% cover by non-native (Himalayan blackberry, reed canary grass, English ivy and Scot's broom) during the entire three year monitoring period. The restoration area will be monitored for a period of three years following implementation of the plan to ensure goals and performance standards are met. Performance Standards During each year of the three year monitoring period, the restored wetland and buffer shall meet the following performance standards: • Minimum of 90% survival of planted species within the restored wetland and buffer areas. • Less than 15% cover by non-native exotics, including reed canary grass, blackberry species and Scot's broom. By the end of the three year monitoring period, the restored wetland and buffer shall meet the following performance standards: • Minimum of 90% survival of planted species within the restored wetland and buffer areas. • Minimum of 50% cover within the restored area by native vegetation 4 feet or taller, including native volunteers not installed, such as red alder, salmonberry or trailing blackberry. 6 I • Less than 15% cover by non-native exotics, including reed canary grass, blackberry species and Scot's broom. MONITORING PLAN The monitoring plan has been prepared so that it can be conducted by the current owner or by a biologist. Monitoring will occur for a period of three years following installation of the plants to track the success of the project and to ensure that the performance standards are met. Monitoring should take place at the end of each summer (August or September, which is considered the end of the growing season) so that the plants have had a chance to grow fully. A transect will be established through the narrow restored/created wetland and the enhanced buffer areas that will be used to document the survival rate. The percent cover will be estimated within each planting area because they encompass such a small area. The performance standards and the methods used to analyze the conditions are listed below. Performance Standard #1-Survival Rate-Survival rate will be determined by counting the number of live individuals of the different species and dividing by the number of that species originally installed, which will give a percent survival rate. The survival rate for each species can then be added together to come up with the survival rate for the entire restoration area. Performance Standard #2-Percent Cover-The percent cover standard will be monitored as if looking over the restored area from above and estimating the areas covered by the individual species. To determine the percent cover easily, the restoration area can be divided into quarters and the amount of area covered by each plant species (installed or volunteer plant) estimated within each quarter. The cover within each quarter can then be added together to determine the overall cover within the restored area. The percent cover within an area can total greater than 100% because of the overlap in plant cover provided by the tree, high shrub and low shrub canopy layers. Performance Standard #3-Cover by Non-Natives-The cover by non-native plants, which typically include tall grass, Scot's broom, and blackberry, should be kept below 15%, which is why regular maintenance is required. The cover by these species will be determined through the same process as determining the cover of installed plants. If the percent cover by non-native is too high, more intensive removal must be implemented. Monitoring will also include taking photos from various locations in the restored wetland and buffer areas to visually document the information collected during performance standard monitoring and how the restoration as a whole is progressing. The photos should be taken from the same point and in the same direction during each monitoring year so that a progression of photos of each particular area is available for comparison. The approximate location and direction of the photos should be marked on the as built planting plan and in the field so they can be easily identified during each of the monitoring visits. The photos and performance standard data will be compiled into a short report and submitted to the Environmental Planner of Mason County Department of Community Development (DCD) to ensure compliance with the proposed plan and its performance standards. Submittal and approval of the as built report/letter will initiate the start of the three year monitoring period. The as built will include the planting plan showing the location of the installed plants, whether any plant substitutions were made due to lack of plant availability, and the monitoring and/or photo stations established for the three year monitoring program. MAINTENANCE PLAN Maintenance of the created and restored wetland and enhanced buffer areas shall include removal of non-native invasives to meet the less than 15% cover performance standard and watering of the installed vegetation to meet the 90% survival rate and ensure the plants grow and develop. Removal of non-native plants shall take place at least twice during the growing season (generally March 15`' through October 15`''), once in the spring (May-June) and once in the summer (July-August). Removal of non-natives should be conducted by hand but a weed eater can be used where feasible and care must be taken to avoid injury to the installed plants. Watering of the planted vegetation will be necessary between June and September of each year to ensure the plants survival to meet the 90% survival rate minimum and ensure that they plants develop to meet the 50% cover criteria by the end of the three year monitoring program. Watering should be conducted at least one time per week during the summer when the weather is very warm and dry but is probably not needed as frequently if the summer is cool and wet. Typically, watering is absolutely necessary for at least the first two years after plant installation but may be necessary during the third year if the plants have not become acclimated and die off has been observed during the previous end of growing season monitoring visit. CONTINGENCY PLAN Although the success of the wetland creation and restoration and buffer enhancement plan is not ensured, it is likely to succeed because of the size and scope of the project. If for some reason any of the plant species installed within the planted areas do not survive, they will be replaced with the same native species. The survival rate will be determined during the yearly monitoring visits and replacement of dead or dying plants will occur during the next dormant season. Maintenance activities will be continued for those replaced plants to ensure their survival. If the percent cover or survival rate standards are not met by the end of year three, additional plant installation may be required and the monitoring and maintenance period may be extended for another one to two years. 8 I PERFORMANCE BONDS A performance bond is required for restoration projects to ensure that they are carried out as approved by providing funds for Mason County to facilitate implementation and/or monitoring should the project proponent be unable to implement the approved plan. The following amounts are based on the current plant costs (per plant) including labor to install the plants, hourly rate for plant installation supervision, monitoring by a qualified biologist over the three-year period and the cost estimate to water and weed the site. Two performance bonds can be set aside one for implementation (Performance Bond #1) and one for monitoring/maintenance (Performance Bond #2) phases of the project if acceptable to Mason County Department of Community Development. The performance bond for implementation will be released after submittal and approval (by Mason County) of the as built report and the monitoring/maintenance bond will be released following submittal and approval of the final, Year Three monitoring report. The totals for each performance bond are based on the figures for the services associated with projects of this type and the totals will then be multiplied by an amount (usually 125% to 150%) to be determined by Mason County Department of Community Development. If Mason County requires one bond for both phases, then the figures provided below should be added together for an overall total. PERFORMANCE BOND #1-IMPLEMENTATION 110 1 gallon bareroot and/or containerized plants, labor & tax included (Based on native plant nursery price list as per planting specs) �$88000 Split rail cedar fence (160 lineal feet) 880.00 Cost for supervision by project biologist 340.00 As-Built design and letter 340.00 Total cost for Implementation $2,440.00 PERFORMANCE BOND #2-MONITORING AND MAINTENANCE Three year monitoring ($480.00/year) $1,440.00 Three year maintenance 600.00 Total cost for Monitoring and Maintenance $2,040.00 9 NOTES: DRAWNG IS DIAGRAMMATIC AND SNOWS INTENT, ACTUAL ON THE GROUND PLANTING LOCATIONS WLL BE DETERMINED BY THE PROJECT BIOLOGIST.. DISTURBED WETLAND NORTH SEE RESTORATION/MITIGATION REPORT FAR DETAILS NOT COVERED ON THIS ORA KING. (-800 SO FT) WELL 9 DIRAMINC BASED ON 577E DRONING FRONDED BY CLIENT NETLANDS DELINEATED BY NILTERMOOO ASSOCIATES INC, .ALINE 2004. RESTORED WETLAND \� Q! � NE7LAN0 DFLNEATIOV GROUND MEASURED BY NIL TETaM000 ASSOCIATES, (-680 SO FT) INC, PERSONNEL CREATED TOTAL AREA OF OETLAND DISTURBANCE— —800 SO FT. WETLAND (-1,600 SO FT) GRADED TOTAL AREA d TI NE7LAN0 RESTORADI+— -sao SO FT AREA Toro AREA OF METLAND CREATION — —1,600 SO FT. WETLAND EDGE OVER EXCAVATE CREATED NETLINO AREA AND PLACE 6'ORGANIC TAP SOIL TO FINISHED GRADE. SLOPE (TYPICAL) PLACE SPLIT RAIL FENCE B£TIVEEN BUILDING SITE AND CREATED WMAND. (SEE GEOTECH REPORT) � PLANT SPECIES, QUANTITIES AND SIZE MUST BE FRONDED AS SPECIFIED. ANY SPLIT RAIL FENCE SUBSTITUTIONS MUST BE APPROVED BY THE PROXCT BIOLOGIST. 37.5' BUFFER PLANT LOCA TTONS ARE APPROXIMATE AND MAY NEED Amisrumr ACCORDING TO FIELD CONDITIONS ALL PLANT MATERIALS AND PLANTED LOCATIONS MUST BE APPROVED BY 774E PROJECT BIOLOGIST. ALL PLANTING MATERIALS SHALL BE HEALTHY, SOUND, VIGOROUS OF GROWTH, FREE Or ANY DETECTS DISEASES AMC ANY FORM OF INFESTATIONS THE PROJECT BIOLOGIST WU PROVIDE A UST OF NURSERIES RECOMMENDED ® ® TO SUPPLY QUALITY PLANT MATERIALS SEE DETAIL •A• ® ALL PLANTING HILL BE RANDOM(HAND LAID OUT, NOT BY STRING LINE). TRIANGULAR SPACED 4I7HIN THEIR RESPECTIVE ZONES TO ® EMULATE A NATURAL PATTERN OF GROWTH. OQ SUBSTITUTIONS OF ANY PLANT MATERIALS OR CHANGES IN THE LANDSCAPE PLAN �r MUST BE APPROVED BY THE PROECT BIOLOGIST. MAN ST'II CUNIOI NNE DDEN@Yt NOW sum SPN96 <v� PLANTING BACKFTLL SOIL SHALL BE SOIL INDIGENOUS TO THE PLA9�?O MAY BE USED IN BUFFER AREAS ADMINNG AREAL A NS U n TEREDATTHE AMOUNG NTS RECOMMENDED BY THE 2 CEWT RED-CSIEF B05VCM C—•t k.W v I CA" {'-L'DD CLUMPED ® MANUFACTURER OR A FERTILIZER AS RECCM 04ENDM BY THE PROJECT BIOLOGIST. E4 LUN LIIO(TVV0EMrf L-k—by 1—ft I CAU /'-6'Q CLUMPED 0J\ N SMA PAC3S VDLIV r r, I CAL. 7-r IZ CLLN" is WESTERN WED CEWI T/Vp PDst• I CAL AS SHWN 32 ® DaLiAS EDP P—udolape-,.*A I CX K DOVN • THREE CI1TTDfS My/E 3L4S17TLRFD i1><EK71 l CAL'CANT Carol Dimarco 10701 Scala Beach Dr. SW Seattle, WA 98146 e-zo-oa / hi GRAPHIC SCALECarol Dimarco mD w so ,� sm DETAIL "A" Wetland Restoration/Mitigation Plan PLANTING PLAN (NO SCALE) Wiltermood Associates, Inc. ( � r� )� ) ems sr.Nw.ra,w role adwL w ameT (m)eTr>-z,ru