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Table 11-4.2.1 Runoff Conveyance and Treatment BMPs by SWPPP Element (continued) Ele- Element Element Ele- Ele- ment #4 Ele- #8 Stab- ment Element #3 Install ment ment ilize Element #10 #13 Protect BMP or Ele- 7 Pro #9 Con - ment Name Con- Sed- #6 Pro- tact Chan- _Control COI POI Low Impact trot iment tact nets De- - Devel- Drain lutants Flow Con- Slopes and Out Water- opment Rates I trols Inletslets ing for High pH Water tp 412) BMP C2OO: 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 storm - water. 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 velo- city of runoff flowing down the slope. Locate downslope to collect runoff from a disturbed area and direct water to a sed- iment basin. Design and Installation Specifications . Dike and/or swale and channel must be stabilized with temporary or permanent vegetation or other channel protection during construction. . Channel requires a positive grade for drainage; steeper grades require channel protection and check dams. . Review construction for areas where overtopping may occur. . Can be used at top of new fill before vegetation is established. 2014 Stormwater Management Manual for Western Washington Volume 11 - Chapter 4 - Page 331