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i Table 11-4.2.1 Runoff Conveyance and Treatment BMPs by SWPPP Element (continued) Ele- Element . Element Ele- i ment #4 Ele Ele #8 Stab ment Element meat Element #3 Install m+ent ilize #10 #13 Pr+ofiect EMP or Ele- #7 Pro #9 Gon111 - Gon- -Chan Control Low Impact meet Name tect trot Pol- trot anent tect nets Ce Le�rel- Drain lutants Flow Con Slopes and Out Water- opment Inlet;a Rates trots lets rn for Hiigh pH Water i (p.412) , BMP C200: Interceptor Dike and Swale I Purpose i 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. • I Conditions of Use Where the runoff from an exposed site or disturbed slope must be conveyed to an I .. erosion control facility which can safely convey the stormwater. . Locate upslope of a construction site to prevent runoff from entering disturbed area. i . When placed horizontally across a disturbed slope, it reduces the amount and velo- city of runoff flowing down the slope. i . Locate downslope to collect runoff from a disturbed area and direct water to a sed- iment basin. • i Design and Installation Specifications • Dike and/or swale and channel must be stabilized with temporary or permanent i vegetation or other channel protection during construction. . Channel requires a positive grade for drainage; steeper grades require channel i 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. i 2014 Stormwater Management Manual for Western Washington Volume 11- Chapter 4 -. Page 331