2320 RAILWAY AVE INTERWEST CONSTRUCTION INC 2023-06-12

INTER WEST — EVERETT CONTRACTOR'S YARD INTERIM FILL PROJECT Sitts & Hill Engineers, Inc. CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN Job Number 17,733 • For less than 30 days on disturbed areas that require cover. • At all times for seeded areas, especially during the wet season and during the hot summer months. • During the wet season on slopes steeper than 3HA V with more than 10 feet of ver- tical relief. Mulch may be applied at any time of the year and must be refreshed periodically. For seeded areas mulch may be made up of 100 percent: cottonseed meal; fibers made of wood, recycled cellulose, hemp, kenaf, compost; or blends of these. Tack- ifier shall be plant -based, such as guar or alpha plantago, or chemical -based such as polyacrylamide or polymers. Any mulch or tackifier product used shall be installed per manufacturer's instructions. Generally, mulches come in 40-50 pound bags. Seed and fertilizer are added at time of application. Design and Installation Specifications For mulch materials, application rates, and specifications, see Table 11-4.1.8 Mulch Standards and Guidelines (p.286). Always use a 24nch minimum mulch thickness; increase the thickness until the ground is 95% covered (i.e. not visible under the mulch layer). Note: Thickness may be increased for disturbed areas in or near sensitive areas or other areas highly susceptible to erosion. Where the option of "Compost" is selected, it should be a coarse compost that meets the following size gradations when tested in accordance with the U.S. Composting Council 'Test Methods for the Examination of Compost and Composting" (TMECC) Test Method 02.02-B. Coarse Compost Minimum Percent passing 3" sieve openings 100% Minimum Percent passing 1" sieve openings 90% Minimum Percent passing '/4" sieve openings 70% Minimum Percent passing'/4" sieve openings 40% Mulch used within the ordinary high-water mark of surface waters should be selected to minimize potential flotation of organic matter. Composted organic materials have higher specific gravities (densities) than straw, wood, or chipped material. Consult Hydraulic Permit Authority (HPA) for mulch mixes if applicable. Maintenance Standards - The thickness of the cover must be maintained. Any areas that experience erosion shall be remulched and/or protected with a net 2014 Stormwater Management Manual for Western Washington Volume ll - Chapter 4 - Page 285 SITTS & HILL ENGINEERS, INC. 37 TACOMA, WASHINGTON