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• WEST MINE U.S.S. POND <br />Emergency Spillway Calcuations <br />Page No. Basis and reference as before runoff 1.7" CN=89 <br />15.7 Lag Time L = HL'8 S + 1 '7 L = lag - hours <br />1900 y HL= Hydraulic length <br />L = (2200)'8(L1890 - 10)] + 1).7 <br />1900 (59)'5 <br />S = 1000 _ 10 <br />L= 472 1.76 CN <br />1900 7.68 CN = 89 <br />y = slope <br />L= .057 hours = 3.4 minutes from blowup of U.S.G.S. <br />quad sheet <br />For the purpose of this calculation it is presumed that the 25 yrs. <br />• 24 hr. storm over tops the Diversion Ditch, and that the flow reports <br />to the U.S.S. Pond. <br />The area contributing to the U.S.S. Pond will be 34 acres from the <br />Diversion map plus 8.19 acres from the West Mine U.S.S. Pond <br />calculation sheet (page 8). <br />Area = 34 acres <br />8.19 acres <br />42.19 acres <br />42.19 acres <br />640 acres/sq.miles = .066 sq.miles <br />Note: Q over topping the Diversion structure will be the differecne <br />between 1.7" and the design Q .75". <br />16.7 Peak Runoff <br />qp = <br />peak runoff <br />6 hrs. qP = 484 AQ Q = rainfall in inches <br /> dD+L <br /> 2 A = area in sq. miles <br /> qp = 484 (.066)(.95) d D = duration of rain <br /> 6 + .057 <br />3 <br />L = <br />lag time in hours <br />• qp = 9.93 second feet <br />