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CITY OF EVERETT STORMWATER MANAGEMENT MANUAL <br />f. Level spreaders <br />g. Berms. <br />Design and Installation Specifications <br />1. Made of urethane foam sewn into a woven geosynthetic fabric. <br />2. It is triangular, 10 inches to 14 inches high in the center, with a 20-inch to 28-inch base. A 2—foot <br />apron extends beyond both sides of the triangle along its standard section of 7 feet. A sleeve at <br />one end allows attachment of additional sections as needed. <br />3. Install with ends curved up to prevent water from flowing around the ends. <br />4. The fabric flaps and check dam units are attached to the ground with wire staples. Wire staples <br />should be No. 11 gauge wire and should be 200 millimeters to 300 millimeters in length. <br />5. When multiple units are installed, the sleeve of fabric at the end of the unit shall overlap the <br />abutting unit and be stapled. <br />6. Check dams should be located and installed as soon as construction will allow. <br />7. Check dams should be placed perpendicular to the flow of water. <br />8. When used as check dams, the leading edge must be secured with rocks, sandbags, or a small key <br />slot and staples. <br />9. In the case of grass -lined ditches and swales, check dams and accumulated sediment shall be <br />removed when the grass has matured sufficiently to protect the ditch or swale unless the slope of <br />the swale is greater than 4 percent. The area beneath the check dams shall be seeded and <br />mulched immediately after dam removal. <br />Maintenance Standards <br />1. Triangular silt dams shall be monitored for performance and sediment accumulation during and <br />after each runoff producing rainfall. Sediment shall be removed when it reaches one half the <br />height of the dam. <br />2. Anticipate submergence and deposition above the triangular silt dam and erosion from high flows <br />around the edges of the dam. Immediately repair any damage or any undercutting of the dam. <br />3.3.10 BMP C209: Outlet Protection <br />Purpose <br />Outlet protection prevents scour at conveyance outlets and minimizes the potential for downstream <br />erosion by reducing the velocity of concentrated stormwater flows. <br />Conditions of Use <br />Outlet protection is required at the outlets of all ponds, pipes, ditches, or other conveyances, and where <br />runoff is conveyed to a natural or manmade drainage feature such as a stream, wetland, lake, or ditch. <br />Design and Installation Specifications <br />See Volume I, Chapter 6.6. <br />Maintenance Standards <br />1. Inspect and repair as needed <br />2. Add rock as needed to maintain the intended function <br />Volume ll — Construction Stormwater Pollution Prevention <br />3-48 <br />