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• Calculation Sheet 4 of 5 <br />PCI Sediment Pond 111 <br />As Built <br />Convert to acre feet <br />S .876 in, x 308.3 ac. x (1 ft/12 in) <br />= 22.51 ac. ft. <br />Storage of runoff is explained on Page 7 of Sediment Pond 111 <br />calculation sheets (Appendix 5-2). As runoff from the surface facilities <br />drains from Sediment Pond IJ1, the runoff stored in the pit wlll be pumped <br />into the west collection channel. <br />Estimate Maximum Drainage Outlet Slze <br />The drainage outlet will be a small diameter hole cut into a vertical <br />riser pipe of 12 inch diameter. The outlet is positioned at maximum <br />sediment fillup and discharge is governed by the orifice flow equation: <br />Q = C' a 2gH where <br />• Q = Qpo converted to cfs 7.772 cfs <br />c' = orifice coefficient ~ _ .6 <br />a cross-sectional area of outlet in ft2 = n r2 <br />g = gravitational constant = 32.2 ftJsec. <br />H = height of water above stage 0 = 6.5' <br />(sediment level) <br />a (7.772 cfs)/(.6~(2)(32.2 ft/sec)(6.5) <br />_ .633 ft2 <br />Diameter of Orifice = 2r where r = ~a/n <br />= 2 ~ 633 ft2/n <br />_ .898' or 10.776" <br />. Pueblo Coal has Installed a 7 Inch diameter drainage outlet. Tnis <br />orifice gives a Td of 53.8 hours. <br />