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Figure 11-4.2.20 Sediment Pond Riser Detail <br />Polyethylene cap <br />Perforated <br />polyethylene drainage <br />tubing, diameter min. <br />2" larger than <br />dewatering orifice. <br />Tubing shall comply <br />with ASTM F667 and <br />AASHTO M294. <br />r� <br />DEPARTMENT OF <br />ECOLOGY <br />State of Washington <br />Provide adequate <br />strapping <br />Corrugated <br />metal riser <br />3.5' min. <br />Watertight <br />coupling / <br />Tack weld <br />6" min. r------- <br />18" min. <br />Concrete base <br />2X riser dia. min. <br />Dewatering orifice, <br />schedule 40 steel <br />stub min. diameter <br />per calculations <br />Alternatively, metal <br />stakes and wire may be <br />used to prevent flotation <br />NOT TO SCALE <br />Figure II-4.2.20 <br />Sediment Pond Riser Detail <br />Revised November 2015 <br />Please see http.'#www.ecy.wa.gov/copyright.html for copyright notice including permissions, <br />limitation of liability, and disclaimer. <br />2014 Stormwater Management Manual for Westem Washington <br />Volume Il - Chapter 4 - Page 393 <br />