The URL can be used to link to this page

Home My WebLink AboutMOR2024-00002 Drainage Report, Stormwater Plan - FPA Storm Water Plan - 10/17/2013 Drainage Report Colina Logging & Single Family Residence 420 E Greenview Ln, Shelton Parcel No. 32134-41-00020 Mason County, Washington October 17, 2023 Project#23238 Prepared For: Alex Covina 2442 Gravelly Beach Loop NW #16 Olympia, Washington 98502 Prepared By: Envirotech Engineering PO Box 984 Belfair, Washington 98528 Phone: 360-275-9374 APL CLYDE ST pE T� 43045 �,cf A<QSTERF� \`� 10/17/23 TABLE OF CONTENTS 1.0 PROJECT DESCRIPTION.................................................................................................................. 1 2.0 EXISTING CONDITIONS................................................................................................................... 2 2.1 TOPOGRAPHY.....................................................................................................................................2 2.2 SURFACE DRAINAGE..........................................................................................................................2 2.3 SUBSURFACE CONDITIONS.................................................................................................................2 2.3.1 SUBSURFACE CONDITIONS..............................................................................................................2 2.3.2 GROUNDWATER............................................................................................................................... 3 3.0 HYDROLOGIC/HYDRAULIC INFORMATION............................................................................4 3.1 DEVELOPED SITE DRAINAGE CONDITIONS.......................................................................................4 3.2 DOWNSTREAM ANALYSIS...................................................................................................................4 3.2.1 TRIBUTARY DRAINAGE AREA.........................................................................................................4 3.2.2 DOWNSTREAM DISCHARGE.............................................................................................................4 3.2.3 DOWNSTREAM EROSION AND WATER QUALITY............................................................................4 3.2.4 DOWNSTREAM CONCLUSIONS........................................................................................................4 3.3 HYDROLOGY AND HYDRAULIC ANALYSIS/DESIGN..........................................................................5 3.4 ROOF DOWNSPOUT INFILTRATION....................................................................................................5 3.5 FILTER STRIP...................................................................................................................................... 5 4.0 INSPECTION AND MAINTENANCE............................................................................................... 7 4.1 INSPECTION AND MAINTENANCE SCHEDULE.................................................................................... 7 4.2 INSPECTION AND MAINTENANCE RESPONSIBILITY........................................................................... 7 5.0 CONTROL OF POLLUTANTS OTHER THAN SEDIMENTS......................................................9 6.0 PROJECT ENGINEER'S CERTIFICATION..................................................................................10 Appendices Appendix A—Site Map Appendix B—Pollution Source BMP 1.0 PROJECT DESCRIPTION Envirotech Engineering (Envirotech) has completed this drainage report in conjunction with the stormwater management plan for logging that has already occurred, and a planned single family residence located at 420 E Greenview Ln, identified as parcel number 32134-41-00020, Mason County,Washington. See the Vicinity Map below for a general indication of the Project location. Information pertaining to the development of this project was provided by the proponent of the property. The property has already been logged, and the proposed development includes a Single Family Residence, driveway, on-site septic system, and associated stormwater management facilities. It is anticipated that the access road/ driveways will encompass approximately 1194 sf in size, and structures will encompass 2916 sq. ft. in size, for a total of 4110 sf. ft. of impervious area. The total land area that has been disturbed as a result of past clearing is approximately 0.96 acres. Cut and fill quantities were approximated to be 10 cubic yards (cy) and 10 cy, respectively. See the accompanying stormwater management plans for an illustration of current and proposed site features. N Lake Cranberry Limerick Project i 7 Bay Shore 3 Johns Prairie Oakland 0 4000 Feet Vicinity Map from Mason County Website Envirotech Engineering Drainage Report PO Box 984 page I Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 2.0 EXISTING CONDITIONS The property is accessed from Greenview Lane,an existing dirt/gravel roadway in unincorporated Mason County. Greenview lane bisects the property, and it is assumed that an access easement is located within the area of the roadway. The Project is currently undeveloped, with clearing on- site. Vegetation is typical of the Pacific Northwest. 2.1 "Topography The topographic information provided in this section was extrapolated from a public lidar source, and incorporated observations and field measurements. Where necessary, slope verification included measuring slope lengths and inclinations with a cloth tape and inclinometer. See the Site Plan in Appendix A in this report for an illustration of general topography with respect to the planned development. Critical descending slopes, with grades exceeding 40% appear to be within 300 feet of the planned development. The maximum critical slope is approximately 80% with a vertical relief of about 40 feet. Ascending grades are generally located to the southeast of the planned development. These slopes are relatively minor within 300 feet of the project, with no apparent slope grades of at least 15%. 2.2 Surface Drainage Runoff originating upslope of the development is mostly diverted away from the property by accommodating topography. Excessive scour, erosion or other indications of past drainage problems were not observed within the immediate vicinity of the planned development 2.3 Subsurface Conditions Information on infiltration rates and soil conditions pertaining to the Project was accomplished by Envirotech. Selected information pertaining to the drainage aspect of the project is provided below. The following subsurface conditions are estimated descriptions of the Project subgrade utilizing information from the depth of penetration at all testing, sampling, observed and investigated locations. Soils for this project were described utilizing the Unified Soil Classification System (USCS). Using the USCS in conjunction with estimated relative densities and other anticipated engineering properties of the soil, susceptibility for potential landslides, erosion and seismic hazards may be assessed. 2.3.1 Subsurface Conditions The project is currently composed of native soils without indications of fill. Within test pit locations,soils within the upper 4 feet of natural ground were generally observed to be moist,brown silty sand with gravel(SM). According to the "Soil Survey of Mason County," by the United States Department of Envirotech Engineering Drainage Report PO Box 984 page 2 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 Agriculture, Soil Conservation Service, the site soils are described as Alderwood gravelly sandy loam, Ab, with 8% to 15% slopes, and Lystair sandy loam, Le, with 5% to 15% slopes. Based on the fines content,erodibility of the site soils is considered to be medium. Based on the fines content and fraction of clay within the fines content, settleability of the site soils is expected to be fast. Permeability is expected to be moderate for this site due significance of moderate density, and fine-grained soils. 2.3.2 Groundwater From the water well report(s) and knowledge of the general area, permanent groundwater is at least 50 feet directly below the property at the building pad location. Surface seepage or perched groundwater at shallow depths was not observed on-site, nor indicated on the well reports. Project f x b, 70 140 280 420 Fee , Aerial/Soils Map from USDA NRCS Website Envirotech Engineering Drainage Report PO Box 984 page 3 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 3.0 HYDROLOGIC/HYDRAULIC INFORMATION 3.1 Developed Site Drainage Conditions It is anticipated that the access road/ driveways will encompass approximately 1194 sf in size, and structures will encompass 2916 sq. ft. in size, for a total of 4110 sf. ft. of impervious area. The total land area that is anticipated to be disturbed as a result of past clearing is approximately 0.96 acres. Cut and fill quantities were approximated to be 10 cubic yards (cy) and 10 cy, respectively. Best Management Practices (BMPs)for this project includes infiltration trenches,V- ditches,and vegetated filter strips.Natural drainage patterns are to be maintained to the maximum extents practicable. 3.2 Downstream Analysis This project has been analyzed as a Level 1 Downstream Drainage Analysis in accordance with the prevailing Western Washington Stormwater Drainage Manual. 3.2.1 Tributary Drainage Area The upslope watershed is relatively small,and has low to slightly sloping grades. Stormwater entering the site appears to be negligible. 3.2.2 Downstream Discharge The natural drainage from the property is directed to the north end of the property. The water travels by sheet flow to Cranberry Creek, located approximately 450 feet to the north. Cranberry creek eventually drains into Oakland bay. 3.2.3 Downstream Erosion and Water Quality FEMA mapping, and other documentation do not reveal flooding or erosion hazards on the property. Water quality within the project watershed is not known to have major issues. Ordinary pollution caused by residences and roadways are pollution contributors in the area. Off-site mitigation is not deemed necessary for this Project. This is based on the scale of the proposed Project, and on-site mitigation design. 3.2.4 Downstream Conclusions The project will increase pollution generating surfaces by 4110 sf. Existing mild sloping green areas appear to have sufficient vegetation and pollution removal qualities for the pollution generating surfaces. The proposed drainage design encourages sheet flow dispersal for the runoff. It is our opinion that with proper maintenance and care of the proposed drainage facility, the proposed development will not constitute measurable runoff to offsite properties. Envirotech Engineering Drainage Report PO Box 984 page 4 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 3.3 Hydrology and Hydraulic Analysis/Design The Stormwater Management Manual for Western Washington (SMMWW) was used to calculate all stormwater management facilities. 3.4 Roof Downspout Infiltration Based on the governing storm water manual, the runoff from 2916 sf of impervious area shall be directed to a standard 8 feet wide infiltration trench at 52 feet in length. 3.5 Filter Strip It has been determined that a narrow area vegetative filter strip is the proposed BMP for this site. A Narrow Area Vegetative Filter Strip (VFS) is a BMP's that uses areas of dense planted vegetation(typically grass)and a flat cross slope to maintain sheet flow and remove sediment and other pollutants from runoff coming directly off pavements or other pollution generating surface. VFS is designed to treat an area of 1194 sf. Flow will enter as sheet flow and will not exceed a depth of I". The proposed narrow area VFS has a contributing flow path of 10 feet to the east of the driveway, and 10 feet to the south of the driveway. The longitudinal slope of the driveway contributing drainage area will be graded at no more than 5%. The lateral slope of the contributing drainage area perpendicular to the driveway edge will be graded at 2%or less. According to LID Design Guidance the design procedure is based on the Narrow Area Filter Strips presented in the 2012 Western Washington Stowmwater Design Manual. The filter strip is sized using the width of the flow-path and the longitudinal slope of the filter strip itself(parallel to the flow-path). Since filter strips only provide basic treatment, they should be used where the roadway ADT is less than 30,000 sf(in our project 1194 sf of total driveway area). Envirotech Engineering Drainage Report PO Box 984 page 5 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 20.0 15.0 How path �- 30 fat Y ` I U.U - a 20 feet f :l -- 10 feet :L (I i 5� 10% Filter Strip Slope Ficrure RT.II1.1 \arrosv area ve-uetated filter strip design agraph Envirotech Engineering Drainage Report PO Box 984 page 6 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 4.0 INSPECTION AND MAINTENANCE Erosion and sediment control measures that may be necessary for this project includes: • Temporary stabilized construction entrance; • Temporary silt fence; and, • Permanent vegetation. The following subsections provide details regarding inspection and maintenance schedule, inspection and maintenance responsibility, and an engineer's inspection report. Stabilized Construction Entrance The stabilized construction entrance shall be inspected at reasonable increments. Increased usage of the construction entrance warrants more frequent inspections. Additional rock shall be added periodically to maintain proper function of the pad. Silt Fence All silt fencing shall be inspected immediately after each rainfall and at least daily during prolonged rainfall. Any required repairs shall be made immediately. Permanent Vegetation Permanent vegetation shall initially be inspected regularly to insure establishment and healthy growth. Once established, vegetation may need to be periodically fertilized for continuous growth. Vegetation shall be re-established in areas, if necessary. 4.1 Inspection and Maintenance Schedule While active construction is in process, all temporary erosion and sediment control facilities shall be inspected and immediately maintained if necessary per the requirements provided above. In the event that construction activities are discontinued for at least 4 consecutive days, the owner shall be responsible for the inspection, and immediate maintenance if necessary, of all temporary erosion and sediment control facilities immediately after storm events, and at least once every 7 days. In addition to the aforementioned inspection and maintenance schedule, the owner shall install additional erosion and sediment control facilities if proposed erosion and sediment control measures prove to be inadequate. For permanent facilities, an Operation and Maintenance Manual should be required for this project. 4.2 Inspection and Maintenance Responsibility Inspection, maintenance, and financial liability of all temporary/ permanent erosion and sedimentation control facilities shall ultimately be the responsibility of the property owner. Envirotech Engineering Drainage Report PO Box 984 page 7 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 Currently, the property owner is: Alex Covina 2442 Gravelly Beach Loop NW#16 Olympia,Washington 98502 (360)627-1540 An operation and maintenance covenant will be required to cover all stormwater facilities. Performance bonding, or other appropriate instrument, shall be required for this project to ensure compliance with the standards presented in this report. Furthermore, the owner may need to retain an Erosion and Spill Control (ESC) Lead for construction observation and oversight of the project if required by the County to ensure compliance with the ESC components of the approved Drainage and Erosion/ Sediment Control Plans. Envirotech Engineering Drainage Report PO Box 984 page 8 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 5.0 CONTROL OF POLLUTANTS OTHER THAN SEDIMENTS Upon completion of this project and future development of the lot, this project is expected to render no more than 10 trips per day of traffic. Potential source of pollutants may occur from spills, leaks, excessive usage, ordinary usage, or vandalism of several pollutants including the following: • Fuel • Oil • Solvent • Degreaser • Dust • Pesticide • Herbacide • Fertilizer • Other Chemicals The aforementioned pollutants are not expected to be currently on-site.The potential sources may be released into the stormwater due to development of the facilities, and/or future use of the facilities. Control of pollutants other than sediments include the following: • All pollutants other than sediments shall be handled and disposed of in a manner that does not cause contamination of stormwater. • Cover, containment and protection from vandalism shall be provided for all chemicals, liquid products, petroleum products, and non-inert wastes present on the project site. • Maintenance and repair of heavy equipment and vehicles involving oil changes, hydraulic system drain down, solvent and de-greasing cleaning operations, fuel tank drain down and removal, and other activities which may result in discharge or spillage of pollutants to the ground or into stormwater runoff must be conducted using spill prevention measures, such as drip pans. Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. Emergency repairs may be performed on-site using temporary plastic placed beneath and,if raining,over the vehicle. • Wheel wash or tire bath wastewater shall be discharged to a separate on-site treatment system or to the sanitary sewer, if available. • Application of agricultural chemicals including fertilizers and pesticides shall be conducted in a manner,and at application rates that will not result in loss of chemical to stormwater runoff. Manufacturers' recommendations for application rates and procedures shall be followed. See the Best Management Practices for this development that should be adhered to after construction is complete. Envirotech Engineering Drainage Report PO Box 984 page 9 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 6.0 PROJECT ENGINEER'S CERTIFICATION I hereby state that this drainage plan has been prepared by me or under my supervision and meets the standard of care and expertise which is usual and customary in this community for professional engineers. Please contact,Michael Staten at 360-275-9374 if you have any questions, comments, or require additional information. Sincerely, Envirotech Engineering CLYDF ST WAS lJ� Z Z %L 43045 RFClSTI, %AL� 10/17/23 Michael Staten,P.E. Project Director Envirotech Engineering Drainage Report PO Box 984 page 10 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County, Washington Ph. 360-275-9374 October 17,2023 APPENDIX A SITE MAP ASWYt3ktA nw ruoarscnoe 11 s'r" R � K V CiLARInI AIit g j S i LTA6A1910 •"" f am.rnw �r 1 vvlil �M s vxrtAno rzm m�rr � rmlrrn.vu.ir(a.(aOGt ~TPL y� 11V9apoK !1'tMkilT1A.10{ 1Rl!GAI TT'rSApby MIfi.YfDlIiLYT:l4 i .•saln ne ns. wwasa•:w rne�rn Y 6•1vAA xrn YO.t v1M ]Y ............................0............._.._................................... ............Y.............................................. Olgm or L tlht.�.t.1 �..i. wiweaept DIY!Q!t MID W AIN mm WP NAM DEVELOPMENT Au:%17dtltU �nswvuonnlmwsua� CPWINACE AND EROSION-SEDIMENT 'nw+acrenc+saorwnl evA0.rw�lmwwa \Y CONTROL PLAN aiiwttitn sac rwn...m..n wsa rn waw.e.wrewv fH Y.iTAyI xL x . a. wm 'i=...o}sea.,.:I. ,II.. ., .dl+�uAmlupnlingAmrsls APPENDIX B POLLUTION SOURCE BMP BMPs for Description of Pollutant Sources: Landscaping can include grading, soil Landscaping transfer, vegetation removal, pesticide and fertilizer applications, and and Lawn( watering. Stormwater contaminants include toxic organic compounds, Vegetation heavy metals,oils, total suspended solids,coliform bacteria, fertilizers, and Management pesticides. Lawn and vegetation management can include control of objectionable weeds, insects, mold, bacteria and other pests with chemical pesticides and is conducted commercially at commercial, industrial, and residential sites. Examples include weed control on golf course lawns,access roads, and utility corridors and during landscaping. sap stain and insect control on lumber and logs, rooftop moss removal, killing nuisance rodents; fungicide application to patio decks,and residential lawn,'plant care. Toxic pesticides such as pentachlorophenol,carbamates, and organometallics can be released to the environment by leaching and dripping from treated parts,container leaks, product misuse, and outside storage of pesticide contaminated materials and equipment. Poor management of the vegetation and poor application of pesticides or fertilizers can cause appreciable stormwater contamination. Pollutant Control Approach: Control of fertilizer and pesticide applications, soil erosion, and site debris to prevent contamination of stormwater. Develop and implement an Integrated Pest Management Plan (IPM)and use pesticides only as a last resort. If pesticides/herbicides are used they must be carefully applied in accordance with label instructions on U.S. Environmental Protection Agency (EPA)registered materials. Maintain appropriate vegetation,with proper fertilizer application where practicable,to control erosion and the discharge of stormwater pollutants. Where practicable grow plant species appropriate for the site, or adjust the soil properties of the subject site to grow desired plant species. Applicable Operational BMPs for Landscaping: • Install engineered soil/landscape systems to improve the infiltration and regulation of stormwater in landscaped areas. • Do not dispose of collected vegetation into waterways or storm drainage systems. Recommended Additional Operational BMPs for Landscaping: • Conduct mulch-mowing whenever practicable • Dispose of grass clippings, leaves, sticks,or other collected vegetation, by composting, if feasible. • Use mulch or other erosion control measures when soils are exposed for more than one week during the dry season or two days during the rainy season. • If oil or other chemicals are handled, store and maintain appropriate oil and chemical spill cleanup materials in readily accessible locations. Ensure that employees are familiar with proper spill cleanup procedures. • Till fertilizers into the soil rather than dumping or broadcasting onto the surface. Determine the proper fertilizer application for the types of soil and vegetation encountered. • Till a topsoil mix or composted organic material into the soil to create a well-mixed transition layer that encourages deeper root systems and drought-resistant plants. • Use manual and,,or mechanical methods of vegetation removal rather than applying herbicides, where practical. Applicable Operational BMPs for the Use of Pesticides: • Develop and implement an IPM(See section on IPM at end of BMP) and use pesticides only as a last resort. • Implement a pesticide-use plan and include at a minimum: a list of selected pesticides and their specific uses, brands, formulations, application methods and quantities to be used, equipment use and maintenance procedures; safety,storage, and disposal methods, and monitoring,record keeping, and public notice procedures. All procedures shall conform to the requirements of Chapter 17.21 RCW and Chapter 16-228 WAC(Appendix IV-D R.7). • Choose the least toxic pesticide available that is capable of reducing the infestation to acceptable levels. The pesticide should readily degrade in the environment and/or have properties that strongly bind it to the soil. Any pest control used should be conducted at the life stage when the pest is most vulnerable. For example, if it is necessary to use a Bacillus thuringiens is application to control tent caterpillars, it must be applied before the caterpillars cocoon or it will be ineffective. Any method used should be site-specific and not used.wholesale over a wide area. • Apply the pesticide according to label directions. Under no conditions shall pesticides be applied in quantities that exceed manufacturer's instructions. • Mix the pesticides and clean the application equipment in an area where accidental spills will not enter surface or ground waters,and will not contaminate the soil. • Store pesticides in enclosed areas or in covered impervious containment. Ensure that pesticide contaminated stormwater or spills'leaks of pesticides are not discharged to storm drains. Do not hose down the paved areas to a storm drain or conveyance ditch. Store and maintain appropriate spill cleanup materials in a location known to all near the storage area. • Clean up any spilled pesticides and ensure that the pesticide contaminated waste materials are kept in designated covered and contained areas. • The pesticide application equipment must be capable of immediate shutoff in the event of an emergency. • Do not spray pesticides within 100 feet of open waters including wetlands, ponds, and streams, sloughs and any drainage ditch or channel that leads to open water except when approved by Ecology or the local jurisdiction. All sensitive areas including wells,creeks and wetlands must be flagged prior to spraying. • As required by the local government or by Ecology, complete public posting of the area to be sprayed prior to the application. • Spray applications should only be conducted during weather conditions as specified in the label direction and applicable local and state regulations. Do not apply during rain or immediately before expected rain. Recommended additional Operational BMPs for the use of pesticides: • Consider alternatives to the use of pesticides such as covering or harvesting weeds, substitute vegetative growth,and manual weed controUmoss removal. • Consider the use of soil amendments,such as compost, that are known to control some common diseases in plants, such as Pythium root rot, ashy stem blight, and parasitic nematodes. The following are three possible mechanisms for disease control by compost addition(USEPA Publication 530-F-9-044): 1. Successful competition for nutrients by antibiotic production; 2. Successful predation against pathogens by beneficial microorganism. and 3. Activation of disease-resistant genes in plants by composts. Installing an amended soililandscape system can preserve both the plant system and the soil system more effectively. This npe of approach provides a soil/landscape system with adequate depth. permeability. and organic matter to sustain itself and continue working as an effective stormwater infiltration system and a sustainable nutrient cycle. • Once a pesticide is applied, its effectiveness should be evaluated for possible improvement. Records should be kept showing the applicability and inapplicability of the pesticides considered. • An annual evaluation procedure should be developed including a review of the effectiveness of pesticide applications, impact on buffers and sensitive areas(including potable wells), public concerns, and recent toxicological information on pesticides used/proposed for use. If individual or public potable wells are located in the proximity of commercial pesticide applications contact the regional Ecology hydrogeologist to determine if additional pesticide application control measures are necessary. • Rinseate from equipment cleaning and/or triple-rinsing of pesticide containers should be used as product or recycled into product. • The application equipment used should be capable of immediate shutoff in the event of an emergency. For more information. contact the W SU Extension Nome-Assist Program. (253) 445-4556, or Bio-Integral Resource Center(BIRC). P.O. Box 7414, Berkelev, CA.94 70 7. or the Washington Department of Ec•olok,to obtain "Hazardous Waste Pesticides"(Publication 489-41):and/or EP.9 to obtain a publication entitled "Suspended, Canceled and Restricted Pesticides-irhich lists all restricted pesticides and the specific uses that are allowed. Valuable information from these sources may also be available on the internet. Applicable Operational BMPs for Vegetation Management: • Use at least an eight-inch "topsoil" layer with at least 8 percent organic matter to provide a sufficient vegetation-growing medium. Amending existing landscapes and turf systems by increasing the percent organic matter and depth of topsoil can substantially improve the permeability of the soil, the disease and drought resistance of the vegetation, and reduce fertilizer demand. This reduces the demand for fertilizers, herbicides, and pesticides. Organic matter is the least water-soluble form of nutrients that can be added to the soil. Composted organic matter generally releases only between 2 and 10 percent of its total nitrogen annually,and this release corresponds closely to the plant growth cycle. If natural plant debris and mulch are returned to the soil,this system can continue recycling nutrients indefinitely. • Select the appropriate turfgrass mixture for your climate and soil type. Certain tall fescues and rye grasses resist insect attack because the symbiotic endophytic fungi found naturally in their tissues repel or kill common leaf and stem-eating lawn insects. They do not, however, repel root-feeding lawn pests such as Crane Fly larvae, and are toxic to ruminants such as cattle and sheep. The fungus causes no known adverse effects to the host plant or to humans. Endophytic grasses are commercially available and can be used in areas such as parks or golf courses where grazing does not occur. The local Cooperative Extension office can offer advice on which types of grass are best suited to the area and soil type. • Use the following seeding and planting BMPs, or equivalent BMPs to obtain information on grass mixtures,temporary and permanent seeding procedures, maintenance of a recently planted area, and fertilizer application rates: Temporary Seeding, Mulching and Matting, Clear Plastic Covering, Permanent Seeding and Planting, and Sodding as described in Volume 11). • Selection of desired plant species can be made by adjusting the soil properties of the subject site. For example, a constructed wetland can be designed to resist the invasion of reed canary grass by layering specific strata of organic matters(e.g., compost forest product residuals)and creating a mildly acidic pH and carbon-rich soil medium. Consult a soil restoration specialist for site-specific conditions. • Aerate lawns regularly in areas of heavy use where the soil tends to become compacted. Aeration should be conducted while the grasses in the lawn are growing most vigorously. Remove layers of thatch greater than 1/4-inch deep. • Mowing is a stress-creating activity for turfgrass. When grass is mowed too short its productivity is decreased and there is less growth of roots and rhizomes. The turf becomes less tolerant of environmental stresses, more disease prone and more reliant on outside means such as pesticides, fertilizers and irrigation to remain healthy. Set the mowing height at the highest acceptable level and mow at times and intervals designed to minimize stress on the turf. Generally mowing only 1/3 of the grass blade height will prevent stressing the turf. Irrigation: The depth from which a plant normally extracts water depends on the rooting depth of the plant. Appropriately irrigated lawn grasses normally root in the top 6 to 12 inches of soil; lawns irrigated on a daily basis often root only in the top I inch of soil. Improper irrigation can encourage pest problems, leach nutrients,and make a lawn completely dependent on artificial watering. The amount of water applied depends on the normal rooting depth of the turfgrass species used, the available water holding capacity of the soil,and the efficiency of the irrigation system. Consult with the local water utility, Conservation District,or Cooperative Extension office to help determine optimum irrigation practices. Fertilizer:Nanagentent: • Turlgrass is most responsive to nitrogen fertilization, followed by potassium and phosphorus. Fertilization needs vary by site depending on plant, soil and climatic conditions. Evaluation of soil nutrient levels through regular testing ensures the best possible efficiency and economy of fertilization. For details on soils testing, contact the local Conservation District or Cooperative Extension Service. • Fertilizers should be applied in amounts appropriate for the target vegetation and at the time of year that minimizes losses to surface and ground waters. Do not fertilize during a drought or when the soil is dry. Alternatively,do not apply fertilizers within three days prior to predicted rainfall. The longer the period between fertilizer application and either rainfall or irrigation, the less fertilizer runoff occurs. • Use slow release fertilizers such as methylene urea, IDBU, or resin coated fertilizers when appropriate, generally in the spring. Use of slow release fertilizers is especially important in areas with sandy or gravelly soils. • Time the fertilizer application to periods of maximum plant uptake. Generally fall and spring applications are recommended, although WSU turf specialists recommend four fertilizer applications per year. • Properly trained persons should apply all fertilizers. At commercial and industrial facilities fertilizers should not be applied to grass swales, filter strips, or buffer areas that drain to sensitive water bodies unless approved by the local jurisdiction. Integrated Pest Management An IPM program might consist of the following steps: Step I: Correctly identify problem pests and understand their life cycle Step 2: Establish tolerance thresholds for pests. Step 3: Monitor to detect and prevent pest problems. Step 4: Modify the maintenance program to promote healthy plants and discourage pests. Step 5: Use cultural, physical, mechanical, or biological controls first if pests exceed the tolerance thresholds. Step 6: Evaluate and record the effectiveness of the control and modify maintenance practices to support lawn or landscape recovery and prevent recurrence. Construction Stormwater Pollution Prevention Plan Colina Logging & Single Family Residence 420 E Greenview Ln, Shelton Parcel No. 32134-41-00020 Mason County, Washington October 17, 2023 Project#23238 Prepared For: Alex Colina 2442 Gravelly Beach Loop NW#16 Olympia, Washington 98502 Prepared By: Envirotech Engineering PO Box 984 Belfair, Washington 98528 Phone: 360-275-9374 AFL CLYb,�ST WAS/, I ? 43045 R'EClSTCREO ♦`ice �SONALF��• 10/17/23 TABLE OF CONTENTS 1.0 INTRODUCTION................................................................................................................................. I PROJECTDESCRIPTION............................................................................................................................... I EXISTING SITE CONDITIONS....................................................................................................................... 1 OFFSITE DRAINAGE TO THE PROPERTY PRIMARILY ORIGINATES FROM THE NORTH,EAST,AND WEST. EROSION WAS NOT OBSERVED ON THE PROPERTY................................ERROR!BOOKMARK NOT DEFINED. ADJACENTAREAS......................................................................................................................................2 CRITICALAREAS........................................................................................................................................2 SOILS..........................................................................................................................................................2 EROSION PROBLEM AREAS.........................................................................................................................3 CONSTRUCTIONPHASING...........................................................................................................................3 CONSTRUCTIONSCHEDULE........................................................................................................................3 ENGINEERING CALCULATIONS...................................................................................................................3 2.0 SPECIFIC CONSTRUCTION SWPPP ITEMS.................................................................................4 2.1 ELEMENT 1-PRESERVE VEGETATION/MARK CLEARING LIMITS........................................................4 2.2 ELEMENT 2-ESTABLISH CONSTRUCTION ACCESS...............................................................................4 2.3 ELEMENT 3-CONTROL FLOW RATES..................................................................................................4 2.4 ELEMENT 4-INSTALL SEDIMENT CONTROLS.......................................................................................4 2.5 ELEMENT 5-STABII IZE SOILS.............................................................................................................5 2.6 ELEMENT 6-PROTECT SLOPES............................................................................................................5 2.7 ELEMENT 7-PROTECT DRAIN INLETS..................................................................................................5 2.8 ELEMENT 8-STABIIJZE CHANNELS AND OUTLETS..............................................................................5 2.9 ELEMENT 9-CONTROL POLLUTANTS.................................................................................................. 5 2.10 ELEMENT 10-CONTROL DEWATERING.............................................................................................. 6 2.11 ELEMENT 11 -MAINTAIN BMP'S....................................................................................................... 6 2.12 ELEMENT 12-MANAGE THE PROJECT............................................................................................... 7 2.13 ELEMENT 13-PROTECT LOW IMPACT DEVELOPMENT BMP'5.......................................................... 7 1.0 Introduction Envirotech Engineering (Envirotech) has completed this construction stormwater pollution prevention plan (SWPPP) in conjunction with the stormwater management plan for logging that has already occurred, and a planned single family residence located at 420 E Greenview Ln, identified as parcel number 32134-41-00020,Mason County,Washington. Best Management Practices (BMP's) selected for this project includes a stabilized construction entrance and silt fencing. It is our opinion that these selected BMP's adequate for preventing significant construction stormwater pollution from leaving the project site,and meets the intent of the Stormwater Manual. The following 13 items have been addressed per the prevailing Stormwater Manual. Project Description Information pertaining to the development of this project was provided by the proponent of the property. The proposed development includes a Single Family Residence, driveway, on-site septic system,and associated stormwater management facilities. It is anticipated that the access road/ driveways will encompass approximately 1194 sf in size, and structures will encompass 2916 sq. ft. in size, for a total of 4110 sf. ft. of impervious area. The total land area that is anticipated to be disturbed as a result of past clearing is approximately 0.96 acres. Cut and fill quantities were approximated to be 10 cubic yards (cy) and 10 cy, respectively. See the accompanying stormwater management plans for an illustration of current and proposed site features. Existing Site Conditions The property is accessed from Greenview Lane, an existing dirt/gravel roadway,in unincorporated Mason County. Greenview lane bisects the property, and it is assumed that an access easement is located within the area of the roadway. The Project is currently undeveloped, with clearing on- site.Vegetation is typical of the Pacific Northwest. Critical descending slopes, with grades exceeding 40% appear to be within 300 feet of the planned development. The maximum critical slope is approximately 80% with a vertical relief of about 40 feet. Ascending grades are generally located to the southeast of the planned development.These slopes are relatively minor within 300 feet of the project,with no apparent slope grades of at least 15%. Runoff originating upslope of the development is mostly diverted away from the property by accommodating topography. Excessive scour, erosion or other indications of past drainage problems were not observed within the immediate vicinity of the planned development Envirotech Engineering SWPPP PO Box 984 page 1 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 Adjacent Areas The area of land that contributes stormwater runoff to the proposed development areas of the property is generally located to the south. The upland drainage basin is primarily vacant land and rural residential development. The upslope watershed for this property is estimated to be small, with little water entering the property The natural drainage from the property is directed to the north end of the property. The water travels by sheet flow to Cranberry Creek, located approximately 450 feet to the north. Cranberry creek eventually drains into Oakland bay. r Critical Areas Other than the aforementioned slopes located on the property, critical areas were not observed within the vicinity of the project.This project is not anticipated to disturb any critical area. soils Information on infiltration rates and soil conditions pertaining to the Project was accomplished by Envirotech. Selected information pertaining to the drainage aspect of the project is provided below. The following subsurface conditions are estimated descriptions of the Project subgrade utilizing information from the depth of penetration at all testing, sampling, observed and investigated locations. Soils for this project were described utilizing the Unified Soil Classification System (USCS). Using the USCS in conjunction with estimated relative densities and other anticipated engineering properties of the soil, susceptibility for potential landslides, erosion and seismic hazards may be assessed. The project is currently composed of native soils without indications of fill. Within test pit locations, soils within the upper 4 feet of natural ground were generally observed to be moist, brown silty sand with gravel(SM). According to the "Soil Survey of Mason County," by the United States Department of Agriculture, Soil Conservation Service, the site soils are described as Alderwood gravelly sandy loam,Ab,with 8%to 15% slopes,and Lystair sandy loam,Le,with 5%to 15% slopes. Based on the fines content, erodibility of the site soils is considered to be medium. Based on the fines content and fraction of clay within the fines content, settleability of the site soils is expected to be fast. Permeability is expected to be moderate for this site due significance of moderate density,and fine-grained soils. From the water well report(s) and knowledge of the general area, permanent groundwater is at least 50 feet directly below the property at the building pad location. Envirotech Engineering SWPPP PO Box 984 page 2 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 According to the Critical Aquifer recharge Areas Map for Mason County, the site is not within a Category II Aquifer Recharge Area. Erosion Problem Areas There are no identified or mapped erosion hazard areas for this property. The soil characteristics provide a low to moderate erodibility factor. Construction Phasing Construction phasing for this project is not expected.Upon finishing the access roads,developing single family residences will be considered future projects. Construction Schedule Construction of the project may occur as early as January 2024.Wet season erosion control is not likely required for this project. However, wet season construction constraints are not necessary for critical areas. Engineering Calculations Standard sediment ponds and traps were not utilized for this project. However, sedimentation due to construction runoff is anticipated to be retained on site. Significant diversions and waterways were not utilized for this project.Silt fencing is deemed adequate for this project,and calculations are not required for this erosion control. r Envirotech Engineering SWPPP PO Box 984 page 3 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 2.0 Specific Construction SWPPP Items The following 13 items have been addressed per the prevailing Stormwater Manual. 2.1 Element 1 -Preserve Vegetation/Mark Clearing Limits Before beginning land disturbing activities, including clearing and grading, clearing limits, sensitive areas and their buffers shall be clearly delineated on-site. This includes delineating trees that are to be preserved within the construction area. Construction activities are not permitted beyond the designated clearing limits without prior approval. Retain the duff layer, native top soil, and natural vegetation in an undisturbed state to the maximum degree practicable. 2.2 Element 2-Establish Construction Access Construction access is designated as the ingress/ egress connecting to E Greenview Lane. One construction access is allowed for this project. Stabilize the construction access with rock per the stormwater plans in order to minimize tracking of sediments off-site. If the stabilized construction entrance proves ineffective,locate wheel wash or tire baths on-site.If sediment is tracked off-site, clean the affected roadway thoroughly at the end of each day, and more frequent as necessary. Remove sediments by any means necessary, and transport the sediment to a controlled sediment disposal area. After sediment removal, conduct street washing, and control wash water by pumping back on-site, or otherwise prevent it from discharging into systems tributary to waters of the State. 2.3 Element 3- Control Flow Rates At all times, flow rates shall be controlled for this project. Natural drainage patterns shall be protected as much as possible during construction, and concentrated flow should not be permitted, unless directed to an engineered drainage facility. Protect downstream waterways and properties from associated discharge of turbid waters. 2.4 Element 4 -Install Sediment Controls Sediment discharges from the project site must be minimized. Sediment controls deemed adequate for this project is temporary silt fencing, and shall be located downslope from all disturbed areas. If sediment control is not working as intended, additional controls such as sediment traps, hay bales,filters,or other standard controls will be necessary. Envirotech Engineering SWPPP PO Box 984 page 4 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 2.5 Element 5-Stabilize Soils Soil stabilization is not necessary for this project. Temporary seeding and permanent soil stabilization requirements are provided in the erosion control section of the design drawings. Always minimize the area of exposed soils during construction, including disturbance on steep slopes. In addition, soil compaction should be minimized, and topsoil preserved as much as possible. Soils shall not remain exposed and unworked for more than 7 days during the dry season (May 1 —September 30),and more than 2 days during the wet season(October 1 —April 30). 2.6 Element 6-Protect Slopes Slopes are not expected to be protected for this project 2.7 Element 7-Protect Drain Inlets There are no existing drain inlets close to the project that would be influenced by the construction.Newly installed catch basins and other inlets, shall be protected from runoff siltation via silt fence inlet barriers, inserts, or other appropriate means. Clean or remove and replace inlet protection devices when sediment has filled one-third of the available storage (unless a different standard is specified by the product manufacturer). 2.8 Element 8-Stabilize Channels and Outlets There are no Channels of Outlets planned for this project. 2.9 Element 9-Control Pollutants Pollution generated from construction must be controlled at all times. Control of pollutants other than sediments includes the following: • All pollutants other than sediments shall be handled and disposed of in a manner that does not cause contamination of stormwater. • Cover, containment and protection from vandalism shall be provided for all chemicals, liquid products,petroleum products,and non-inert wastes present on the project site. • Maintenance and repair of heavy equipment and vehicles involving oil changes, hydraulic system drain down, solvent and de-greasing cleaning operations, fuel tank drain down and removal, and other activities which may result in discharge or spillage of pollutants to the ground or into stormwater runoff must be conducted using spill prevention measures,such as drip pans. Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. Emergency repairs may be performed on-site using temporary plastic placed beneath and,if raining,over the vehicle. Envirotech Engineering SWPPP PO Box 984 page 5 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 • Wheel wash or tire bath wastewater shall be discharged to a separate on-site treatment system or to the sanitary sewer,if available. • Application of agricultural chemicals including fertilizers and pesticides shall be conducted in a manner, and at application rates that will not result in loss of chemical to stormwater runoff. Manufacturers' recommendations for application rates and procedures shall be followed. 2.10 Element 10- Control Dewatering Although dewatering will not be likely for this project, special provisions are required to be followed when dewatering. The outlet for dewatering shall be located in a position as to prevent sediments and pollution from leaving the site.This may be accomplished by pumping water into a sedimentation pond, or other standard control. 2.11 Element 11 -Maintain BMP's All BMP's must be inspected and maintained in order to assure continued performance of their intended function. Remove all temporary erosion and sediment control BMP's within 30 days after achieving final site stabilization or after the temporary BMP's are no longer needed. Inspection and maintenance for this project includes the following: Stabilized Construction Entrance The stabilized construction entrance shall be inspected at reasonable increments. Increased usage of the construction entrance warrants more frequent inspections. Additional rock shall be added periodically to maintain proper function of the pad. Silt Fence All silt fencing,if used,shall be inspected immediately after each rainfall and at least daily during prolonged rainfall.Any required repairs shall be made immediately. Permanent Vegetation Permanent vegetation shall initially be inspected regularly to insure establishment and healthy growth. Once established, vegetation may need to be periodically fertilized for continuous growth.Vegetation shall be re-established in areas,if necessary. While active construction is in process,all temporary erosion and sediment control facilities shall be inspected and immediately maintained if necessary per the requirements provided above. In the event that construction activities are discontinued for at least 4 consecutive days, the owner shall be responsible for the inspection, and immediate maintenance if necessary, of all temporary erosion and sediment control facilities immediately after storm events, and at least once every 7 days. Envirotech Engineering SWPPP PO Box 984 page 6 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023 In addition to the aforementioned inspection and maintenance schedule, the owner shall install additional erosion and sediment control facilities if proposed erosion and sediment control measures prove to be inadequate. 2.12 Element 12-Manage the Project Inspection, maintenance, and financial liability of all temporary/ permanent erosion and sedimentation control facilities shall ultimately be the responsibility of the current property owner. All construction facilities and BMP's shall be assured continued performance of their intended function. Since less than 1 acre is planned to be disturbed, a Certified Erosion and Sediment Control Lead (CESCL) is not required. Currently, the designated manager for this project is: Alex Covina 2442 Gravelly Beach Loop NW#16 Olympia,Washington 98502 (360)627-1540 2.13 Element 13—Protect Low Impact Development BMP's Prevent compaction of vegetated flow paths delineated for this project,and other low impact development BMP's that may be associated with this project.This should be done by excluding construction equipment and foot traffic. Envirotech Engineering SWPPP PO Box 984 page 7 Parcel 32134-41-00020 Belfair,Washington 98528 Mason County,Washington Ph. 360-275-9374 October 17,2023