1502 WALL ST IMAGINE CHILDRENS MUSEUM 2022-08-25

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. • See Table 11-3.8: Horizontal Spacing of Interceptor Dikes Along Ground Slope for recom- mended horizontal spacing between dikes. Table 11-3.8: Horizontal Spacing of Interceptor Dikes Along Ground Slope Average Slope Slope Percent Flowpath Length 20H:1 V or less 3-5% 300 feet (10 to 20)H:1 V 5-10% 200 feet (4 to 10)H:1 V 10-25% 100 feet (2 to 4)H:1 V 25-50% 50 feet Interceptor Swales Interceptor swales shall meet the following criteria: . Bottom Width:2 feet minimum;the cross-section bottom shall be level. . Depth: 1-foot minimum. . Side Slope: 2H:1 V or flatter. . Grade: Maximum 5 percent,with positive drainage to a suitable outlet(such as BMP C241: Sediment Pond (Temporary)). . Stabilization: Seed as per BMP C120: Temporary and Permanent Seeding, or BMP C202: Riprap Channel Lining, 12 inches thick riprap pressed into the bank and extending at least 8 inches vertical from the bottom. Maintenance Standards . Inspect diversion dikes and interceptor swales once a week and after every rainfall. Imme- diately 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 sta- bilize the channel to blend with the natural surface. 2019 Stormwater Management Manual for Western Washington Volume II-Chapter 3-Page 331