1622 E MARINE VIEW DR WHOLE SITE 2022-02-01

BMP C200: Interceptor Dike and Swale Purpose Provide a ridge of compacted soil, or a ridge with an upslope Swale, at the top or base of a disturbed slope or along the perimeter of a disturbed construction area to convey stormwater. Use the dike and/or swale to intercept the runoff from unprotected areas and direct it to areas where erosion can be controlled. This can prevent storm runoff from entering the work area or sediment -laden runoff from leaving the construction site. Conditions of Use Where the runoff from an exposed site or disturbed slope must be conveyed to an erosion control facility which can safely convey the stormwater. Locate upslope of a construction site to prevent runoff from entering disturbed area. When placed horizontally across a disturbed slope, it reduces the amount and velocity of runoff flowing down the slope. • Locate downslope to collect runoff from a disturbed area and direct water to a sediment basin. Design and • Dike and/or swale and channel must be stabilized with temporary or Installation permanent vegetation or other channel protection during construction. Specifications • Channel requires a positive grade for drainage; steeper grades require channel protection and check dams. • Review construction for areas where overtopping may occur. i • Can be used at top of new fill before vegetation is established. • May be used as a permanent diversion channel to carry the runoff. • Sub -basin tributary area should be one acre or less. • Design capacity for the peak flow from a 10-year, 24-hour storm, assuming a Type IA rainfall distribution, for temporary facilities. Alternatively, use 1.6 times the 10-year, 1-hour flow indicated by an approved continuous runoff model. For facilities that will also serve on a permanent basis, consult the local government's drainage requirements. Interceptor dikes shall meet the following criteria: Top Width 2 feet minimum. Height 1.5 feet minimum on berm. Side Slope 2H:1V or flatter. Grade Depends on topography, however, dike system minimum is 0.5%, and maximum is 1%. Compaction Minimum of 90 percent ASTM D698 standard proctor. Volume II — Construction Stormwater Pollution Prevention - August 2012 4-57