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occur at the outlet. Provide energy dissipation measures as necessary. Sediment -laden runoff <br />must be released through a sediment trapping facility. <br />Minimize construction traffic over temporary dikes. Use temporary cross culverts for channel <br />crossing. <br />See Table II-3.8: Horizontal Spacing of Interceptor Dikes Along Ground Slope for recom- <br />mended horizontal spacing between dikes. <br />Table II-3.8: Horizontal Spacing of <br />Interceptor Dikes Along Ground <br />Slope <br />Average Slope <br />Slope Percent <br />Flowpath Length <br />20H :1 V or less <br />3-5% <br />300 feet <br />(10 to 20)H:1V <br />5-10% <br />200 feet <br />(4 to 10)H :1 V <br />10-25% <br />100 feet <br />(2 to 4)H :1 V <br />25-50% <br />50 feet <br />Interceptor Swales <br />Interceptor swales shall meet the following criteria: <br />. Bottom Width: 2 feet minimum; the cross-section bottom shall be level. <br />. Depth: 1-foot minimum. <br />. Side Slope: 2H:1 V or flatter. <br />Grade: Maximum 5 percent, with positive drainage to a suitable outlet (such as BMP C241: <br />Sediment Pond (Temporary)). <br />. Stabilization: Seed as per BMP C 120: Temporary and Permanent Seeding, or BMP C202: <br />Riprap Channel Lining, 12 inches thick riprap pressed into the bank and extending at least 8 <br />inches vertical from the bottom. <br />Maintenance Standards <br />. Inspect diversion dikes and interceptor swales once a week and after every rainfall. Imme- <br />diately remove sediment from the flow area. <br />Damage caused by construction traffic or other activity must be repaired before the end of <br />each working day. <br />• Check outlets and make timely repairs as needed to avoid gully formation. When the area <br />below the temporary diversion dike is permanently stabilized, remove the dike and fill and sta- <br />bilize the channel to blend with the natural surface. <br />2019 Stormwater Management Manual for Western Washington <br />Volume 11 - Chapter 3 - Page 331 <br />