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BMP C208: Triangular Silt Dike (Geotextile-Encased Check Dam) <br />Purpose Triangular silt dikes may be used as check dams, for perimeter protection, <br />for temporary soil stockpile protection, for drop inlet protection, or as a <br />temporary interceptor dike. <br />Conditions of use <br />Design and <br />Installation <br />Specifications <br />Maintenance <br />Standards <br />May be used in place of straw bales for temporary check dams in ditches <br />of any dimension. <br />May be used on soil or pavement with adhesive or staples. <br />TSDs have been used to build temporary: <br />1. <br />2. <br />3. <br />4. <br />5. <br />6. <br />7. <br />sediment ponds; <br />diversion ditches; <br />concrete wash out facilities; <br />curbing; <br />water bars; <br />level spreaders; and, <br />berms. <br />Made of urethane foam sewn into a woven geosynthetic fabric. <br />It is triangular, l 0 inches to 14 inches high in the center, with a 20-inch to <br />28-inch base. A 2—foot apron extends beyond both sides of the triangle <br />along its standard section of 7 feet. A sleeve at one end allows attachment <br />of additional sections as needed. <br />• Install with ends curved up to prevent water from flowing around the <br />ends. <br />• The fabric flaps and check dam units are attached to the ground with <br />wire staples. Wire staples should be No. l 1 gauge wire and should be <br />200 mm to 300 mm in length. <br />• When multiple units are installed, the sleeve of fabric at the end of the <br />unit shall overlap the abutting unit and be stapled. <br />• Check dams should be located and installed as soon as construction <br />will allow. <br />• Check dams should be placed perpendicular to the flow of water. <br />• When used as check dams, the leading edge must be secured with <br />rocks, sandbags, or a small key slot and staples. <br />• In the case of grass-lined ditches and swales, check dams and <br />accumulated sediment shall be removed when the grass has matured <br />sufficiently to protect the ditch or swale unless the slope of the swale <br />is greater than 4 percent. The area beneath the check dams shall be <br />seeded and mulched immediately after dam removal. <br />• Triangular silt dams shall be monitored for performance and sediment <br />accumulation during and after each runoff producing rainfall. <br />4-78 Volume ll — Construction Stormwater Pollution Prevention February 2005 <br />