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L = (1600)'8(1890 _ 10 + 1).7 <br />• 1900 y'S <br />= 366 (1.76) <br />1900 (7.42) CN = 89 <br />_ .046 hours Y = slope <br />= 3 minutes from blowup of <br />U.S.G.S. quad sheet <br />The the purpose of this calculation it is presumed that the 25 yr. 24 hr. <br />storm over tops the Diversion Ditches. The flow will split 50-50 and <br />the runoff will report to each pond equally, therefore the contributing <br />area for the 25 yr. 24 hr. storm is: <br />12 acres total diversion area = 9 acres <br />Substation Sediment Pond <br />9.0 acres <br />+ 1.0 acres <br />10.08 acres <br />• <br />East Mine Pond <br />9.0 acres <br />+ 7.38 acres <br />16.38 acres <br />Peak Runoff Substation Pond <br />A= 10.08 acres <br />640 acres/sq.mile = .016 sq. mile <br />Note: Q over topping the diversion structure will be the difference <br />between 1.7" and the design Q .75". 1.7 <br />- .75 <br />.95 <br />16.7 Peak Runoff qp = 484 A <br />qp = peak runoff <br />D + L Q = rainfall in inches <br />A = area in inches <br />qp = 484(.016)(.95) <br />6 + .046 D D = duration of rain <br />• 2 <br />= 2.42 second feet L = lag time in hours <br />