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NORTH DECLINE RECLAMATION <br />POND N0. 7 <br />Sediment Pond No. 7 Runoff Calculations, 25-Year, <br />Powderhorn Coal Company <br />CC2~tP+u~~N ~*~- <br />PAfGS 4.W -22 ~/,A~a INW zs <br />2-2C-92 <br />... <br />~- <br />C °. 5, <br />sc i <br />i <br />1f 4 x: <br />24 r on¢: <br />~V.'d~oiir i ~'r <br />BASIN CHARACTERISTICS <br />DRAINAGE AREA (SQ. MI.) = 0.015 <br />STREAM LENGTH (MI.) = 0.232 <br />ELEVATION DIFFERENCE (FT.) = 52.000 <br />RUNOFF CURVE NUMBER, CN = 82.000 <br />MINIMUM INFILTRATION LOSS (TN./HR.) = 0.000 <br />PRECIPITATION FOR SPECIFIED STORM <br />ADJUSTED PRECIPITATION FOR SELECTED STORM (IN.) _ <br />UNIT HYDROGRAPH PARAMETERS <br />• UNADJUSTED TIME OF CONCENTRATION (HR.). <br />ADJUSTED TIME OF CONCENTRATION (HR.) <br />DURATION OF EXCESS RAINFALL, D {HR.) _ <br />TIME TO PEAK (HR. ) _ <br />BASE TIME (HR. ) _ <br />QPEAK (PEAK FLOW IN CFS FOR UNIT HYDROGRAPH) _ <br />RESULTANT HYDROGRAPH VALUES <br />-- PEAK DISCHARGE (CFS) _ <br />RUNOFF VOLUME (ACRE-FEET) _ <br />TIME TO PEAK DISCHARGE (HR) _ <br />1.80 <br />0.10 <br />0.10 <br />0.01 <br />0.07 <br />0.19 <br />103.8 <br />7.00 <br />0.42 <br />12.02 <br />USED SCS TYPE II 24-HOUR GENERAL STORM <br />Emergency Spillway Design <br />Reference: Figure 4-18, Inlet Control Monogram for CMP, Page 161 <br />Handbood of Steel Drainage & Highway Construction Products <br />American Iron and Steel Institute, 1971. <br />18" CMP with end section protruding from fill requires a HW/D of 1.18 <br />to carry 7.0 CFS. <br />• (Revised 10-7-92) <br />NDEC - 2 <br />