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• SEDIMENT CONTROL COt~L~1ENTS AND CALCULATIONS <br />Drainage from the areas 2, 4, 5, and 7 as shown on Pfap H in <br />the permit application will be diverted into Pond Ill. As noted, <br />Pond 1/2 will be covered in the establishment of the new toe. The <br />sediment capacity of Pond Ill is estimated to be 4.5 a.f. (1.5 acres <br />three feet deep). The primary spillway drains the volume of water <br />in the 2.06' from the primary spillway to the 3' emergency spill- <br />way culvert, 3.1 a.f. <br />The volume required is the total Q from the contributing area: <br />Area 2, 5, & 7 - Page 4 of 10, Appendix C 0.06 a.f. <br />Area 4 - Page 6 of 10, Appendix C 0.05 a.f. <br />Mine drain - Approximately 100 gpm for <br /> 24 hours 0.44 a.f. <br />• Mine bench drains - possibly 5 gpm for 24 <br />hours 0.02 a.f. <br />TOTAL <br />0.57 a.f. <br />The primary discharge pipe in Pond Ill, an 8" CMP with a slope of 2.5% <br />and an n of 0.012, has a capacity of 2.08 CFS, using Mannings Equation. <br />This 8" primary spillway could dewater the pond of 0.57 a.f. in 3.3 <br />hours. <br />Peak flow off the bench areas 2 and 7 was calculated to be 0.92 <br />CFS (page 4 of 10, Appendix C). A 6" ADS plastic corrugated pipe will <br />be routed along the edge of the bench fill on the surface. Using a <br />slope of 50% and an n of 0.025, each pipe has a capacity of 2.1 CFS. <br />These drains may be tapped to discharge the bench subdrains. The <br />bench will be graded to the drains at each end with a slope of 2%. <br />• <br />-4- <br />