3214 BROADWAY BROADWAY KINECT APARTMENTS 2021-08-11

CITY OF EVERETT STORMWATER MANAGEMENT MANUAL • • 8. Keep the center of the check dam at least 12 inches lower than the outer edges at natural ground elevation. 9. Keep the side slopes of the check dam at 2:1 or flatter. • 10. Key the stone into the ditch banks and extend it beyond the abutments a minimum of 18 inches to • avoid washouts from overflow around the dam. w 11. Use filter fabric foundation under a rock or sand bag check dam. If a blanket ditch liner is used, • this is not necessary. A piece of organic or synthetic blanket cut to fit will also work for this - purpose. 12. Rock check dams shall be constructed of appropriately sized rock. The rock must be placed by • hand or by mechanical means (no dumping of rock to form dam) to achieve complete coverage of the ditch or swale and to ensure that the center of the dam is lower than the edges. The rock used • must be large enough to stay in place given the expected design flow through the channel. 40 13. In the case of grass-lined ditches and swales,all check dams and accumulated sediment shall be 411 removed when the grass has matured sufficiently to protect the ditch or swale—unless the slope of the swale is greater than 4 percent. The area beneath the check dams shall be seeded and 41 mulched immediately after dam removal. • 14. Ensure that channel appurtenances, such as culvert entrances below check dams, are not subject 40 to damage or blockage from displaced stones. DCSS Drawing#206 depicts a typical rock check dam. • • Maintenance Standards • 1. Check dams shall be monitored for performance and sediment accumulation during and after each runoff producing rainfall. Sediment shall be removed when it reaches one half the sump depth. • 2. Anticipate submergence and deposition above the check dam and erosion from high flows around • the edges of the dam. • 3. If significant erosion occurs between dams, install a protective riprap liner in that portion of the • channel. 3.3.9 BMP C208: Triangular Silt Dike (Geotextile-Encased Check Dam) fib Purpose 40 Triangular silt dikes may be used as check dams, for perimeter protection,for temporary soil stockpile • protection,for drop inlet protection, or as a temporary interceptor dike. See DCSS Drawing#207. • Conditions of Use el 1. May be used for temporary check dams in ditches of any dimension • 2. May be used on soil or pavement with adhesive or staples • 3. Triangular silt dikes have been used to build temporary: • a. Sediment ponds • b. Diversion ditches 411 c. Concrete wash out facilities d. Curbing • • e. Water bars • Volume II a Construction Stormwater Pollution Prevention 3-47 •