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<br />Sediment Pond Principal Spillway Size Calculation <br />Principal Spillway is CMP of 12" Diameter <br />Maximum head on principal spillway opening - 7.0 feet <br />Average flaw through orifice - 2.23 Ac-Ft * 30 hours ~ 0.9 cfs <br />Where: Q ~ Ca 2 gh <br /> <br />Q 0.9 cfs <br />C ~ 0.6 from page 4-34, Civil Engineering Handbook, <br />McGraw-Hill <br />a orifice area <br />hex ~ 7.0 <br />haverage 3.5 <br />g ~ 32.2 <br />~_ a , 0.9 <br />a C 2 gh 0.6 2(32.2) (3.5) <br />a 0.071 ft2 3.2 inch square opening <br />Peerless Resources, Inc. plans to cut a square opening 3.2 inches on <br />each side in the gate of the principal spillway to allow controlled <br />dewatering of any surface water runoff. <br /> <br />