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1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />I <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />PENSKE TRUCK LEASING EVERETT ONSITE IMPROVEMENTS <br />CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN <br />Sitts & Hill Engineers, Inc. <br />Job Number 17,710 <br />• Beware of where the topsoil comes from, and what vegetation was on site before <br />disturbance, invasive plant seeds may be included and could cause problems for <br />establishing native plants, landscaped areas, or grasses. <br />. Topsoil from the site will contain mycorrhizal bacteria that are necessary for <br />healthy root growth and nutrient transfer. These native mycorrhiza are acclimated <br />to the site and will provide optimum conditions for establishing grasses. Use com- <br />mercially available mycorrhiza products when using off -site topsoil. <br />Design and Installation Specifications <br />Meet the following requirements for disturbed areas that will be developed as lawn or <br />landscaped areas at the completed project site: <br />. Maximize the depth of the topsoil wherever possible to provide the maximum pos- <br />sible infiltration capacity and beneficial growth medium. Topsoil shall have: <br />A minimum depth of 8-inches. Scarify subsoils below the topsoil layer at least <br />4-inches with some incorporation of the upper material to avoid stratified lay- <br />ers, where feasible. Ripping or re -structuring the subgrade may also provide <br />additional benefits regarding the overall infiltration and interflow dynamics of <br />the soil system. <br />A minimum organic content of 10% dry weight in planting beds, and 5% <br />organic matter content in turf areas. Incorporate organic amendments to a <br />minimum 8-inch depth except where tree roots or other natural features limit <br />the depth of incorporation. <br />A pH between 6.0 and 8.0 or matching the pH of the undisturbed soil. <br />p If blended topsoil is imported, then fines should be limited to 25 percent <br />passing through a 200 sieve. <br />o Mulch planting beds with 2 inches of organic material <br />Accomplish the required organic content, depth, and pH by returning native topsoil <br />to the site, importing topsoil of sufficient organic content, and/or incorporating <br />organic amendments. When using the option of incorporating amendments to meet <br />the organic content requirement use compost that meets the compost specification <br />for Bioretention (See BMP T7.30: Bioretention Cells, Swales, and Planter Boxes <br />(p 959)), with the exception that the compost may have up to 35% biosolids or <br />manure. <br />. Sections three through seven of the document entitled, Guidelines and Resources <br />for Implementing Soil Quality and Depth BMP T5.13 in WDOE Stomnaater Man- <br />agement Manual for Western Washington, provides useful guidance for imple- <br />menting whichever option is chosen. It includes guidance for pre -approved default <br />strategies and guidance for custom strategies. Check with your local jurisdiction <br />2014 Stormwater Management Manual for Westem Washington <br />Volume 1I - Chapter 4 - Page 298 <br />SITTS & HILL ENGINEERS, INC. 42 <br />TACOMA, WASHINGTON <br />