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NORTH DECLINE RECLAMATION <br />POND N0. 7 <br />CC2~tP+u~~N ~*~- <br />PAfGS 4.W -22 ~/,A~a INW zs <br />~A 9 <br />Sediment Pond No. 7 Runoff Calculations, 25-Year, 2 <br />Powderhorn Coal Company <br />BASIN CHARACTERISTICS <br />2-2C-92 <br />... <br />~~..,~F-wwz7 <br />~-~-~a <br />~. ',, <br />s: , <br />gig s <br />~r~8toz ¢~ <br />'~f~0/1P~ "~ <br />~., . <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.) = 1.80 <br />UNIT HYDROGRAPH PARAMETERS <br />• UNADJUSTED TIME OF CONCENTRATION (HR.). 0.10 <br />ADJUSTED TIME OF CONCENTRATION (HR.) 0.10 <br />DURATION OF EXCESS RAINFALL, D {HR.) = 0.01 <br />TIME TO PEAK (HR. ) = 0.07 <br />BASE TIME (HR. ) = 0.19 <br />QPEAK (PEAK FLOW IN CFS FOR UNIT HYDROGRAPH) = 103.8 <br />RESULTANT HYDROGRAPH VALUES <br />-- PEAK DISCHARGE (CFS) = 7.00 <br />RUNOFF VOLUME (ACRE-FEET) = 0.42 <br />TIME TO PEAK DISCHARGE (HR) = 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 />