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s <br />~ i ~ <br />CCMC TEST PIT HYDROLOGY CALCULATIONS <br />J. Cornik <br />2/11/82 <br />108.7`'Ac Treatment Area <br />283.0 Ac Diversion Area <br />1 <br />2 <br />Sediment Storage & 10 yr 24 hr runoff storage pond <br />Runoff = 108.7 Ac (0.099 Acft/Ac)(1)(43560 ftz/Ac) 468,762 ,f/t3', <br />~- ~/ <br />Sediment = A = (K)(R)(LS)(C)(P) <br />where k = 75 LS = .21(1) <br />K = 0.24 C8P = 1.0 <br />A = 3.78T/Ac/Yr <br />3 yrs over 108.7Ac = 3(108.7)3.78 = 1,232.7 Tons <br />Assume 80 lbs/fta <br />1232.7 (2000) = 30,816 fta <br />( 80 ) <br />Capacity = 468,762 + 30,816 = 499,578 fta = 18,503 BCY <br />Retainment Ditch Sizing (See map for Configuration) <br />q = ACi = 108.7 (.40)(1.5) = 65.2 where 0.40 = Runoff coef. (1) <br />1.50 = Rainfall Intens. (1) <br />For a "V" ditch with 2:1 slopes~:- <br />Q = 1.486 (2D2) (D/~)~/3 V ~'n,s <br />.03 <br />(1) where .03 = n(1) (roughness) <br />2Dz = Area <br />D~~ = Hydraulic radii <br />S = 10 = .0049 S = Slope (north or <br />N 2050 °'s south) <br />D = Ditch Depth in ft. <br />S = ?0 = .0095 <br />s 2100 <br />Q = 65.2 = 1.486 (2D~)(D/~)2/a Y ~ s <br />.03 <br />1.125 = D 8/3 <br />S <br />n,s <br />D = 2.8 ar 11.2 ft wide and 2.8 ft Deep <br />DS = 2.5 or 10.0 ft wide and 2.5 ft Deep <br />(1) Reference calculations provided as an attachment to the PAR <br />response letter dated December 8, 1981. <br />