825 N BROADWAY 2017-01-13 - Laserfiche WebLink

Horizontal Spacing of Interceptor Dikes: Average Slope Slope Percent 20H:1 V or less 3-5% (10 to 20)H:1V 5-10% (4 to l 0)H:1 V 10-25% (2 to 4)H:1 V 25-50% Stabilization depends on velocity and reach Flowpath Length 300 feet 200 feet 100 feet 50 feet Slopes <5% Seed and mulch applied within 5 days of dike construction (see BMP C121, Mulching). Slopes 5- 40% Dependent on runoff velocities and dike materials. Stabilization should be done immediately using either sod or riprap or other measures to avoid erosion. • The upslope side of the dike shall provide positive drainage to the dike outlet. No erosion shall occur at the outlet. Provide energy dissipation measures as necessary. Sediment-laden runoff must be released through a sediment trapping facility. • Minimize construction traffic over temporary dikes. Use temporary cross culverts for channel crossing. Interceptor swales shall meet the following criteria: Bottom Width 2 feet minimum; the bottom shall be level. Depth l -foot minimum. Side Slope 2:1 or flatter. Grade Maximum 5 percent, with positive drainage to a suitable outlet (such as a sediment pond). Stabilization Seed as per BMP CI20, Temporary and Permanent Seedin.g, or BMP C202, Channel LifZifzg, l 2 inches thick of riprap pressed into the bank and extending at least 8 inches vertical from the bottom. • Inspect diversion dikes and interceptor swales once a week and after eveiy rainfall. Immediately remove sediment from the flow area. • Damage caused by construction traffic or other activity must be repaired before the end of each working day. Check outlets and make timely repairs as needed to avoid gully formation. When the area below the temporary diversion dike is permanently stabilized, remove the dike and fill and stabilize the channel to blend with the natural surface. 4-58 Volume ll — Construction Stormwater Pollution Prevention February 2005