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1 <br />MINE 3 <br />SEDIMENTATION POND E DESIGN CALCULATIONS <br />' VOLUME: <br />-35 ac watershed area <br />-24 ac disturbance <br />-AMC II Curve No. 82 <br />' -10-yr, 24-hr design event of 1.8" rainfall <br />' SEDIMENT VOLUME: <br />24 <br />1 <br />8 i <br />R <br />l0 <br />h <br />i <br />i <br />i <br />( <br />) <br /> - <br />on event = <br />. <br />n. <br />r prec <br />p <br />tat <br />Total <br />unoff <br />Q <br />: <br />-yr, <br /> 1.8 in. rainfall @ curve number (82) = 0.52 in. runoff <br />' 0.52 (in) / 12 (in/ft) x 35 ac. = 1.52 ac-ft <br /> Peak Flow (gp): Type II storm, western Colorado, moderate slope, curve number <br /> (82) .= 32 cfs/in. runoff 32; cfs/in. runoff x 0.52 in. runoff = 16.6 cfs <br /> uncorrected <br />' Basin Slope Factor (actual slope 6%) = 1.1 l <br /> Basin Shape Factor (hydraulic length = 1,750 ft., equivalent area = 36.5 ac) 35/36.5 = <br /> 0.96 <br /> Corrected Peak Flow = 16.6 cfs x l.ll x 0.96 = 17.7 cfs <br /> Soil Erodibility Factor (K): Winnevada-splitro series = 0.2 (SCS) <br />t Length-Slope Factor(LS): <br /> LS = (L/72.6) m((430 x 2 + 30 x + 0.43) / 6.613) <br /> _ (1,750/72.6) 0.5 ((430(.06) 2 + 30 (.06) + 0.43)/6.613) <br /> = 2.80 <br />' Crop Management Factor (c): 1.0 <br /> Support Practice factor (P): 1.0 <br />Modified Universal Soil Loss Equation: <br />Y = 95 (Q gp) 0.56 K LS CP <br />= 95 ((1.52)(17.7)) 0.56 (0.2)(2.80)(1.0)(1.0) <br />= 336 tons x 2000 (lbs/ton) / 60 (lbs/cu.ft.)/43,560 (sq. ft/ac.) <br />= 0.26 ac-ft. <br />' 3 <br />f1 <br />