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ALTERNATE DRAINAGE AREAS <br />RUNOFF CALCULATIONS <br /> <br />REFERENCE: Trihydro, Ver. 2.2, Western Water Consultants, Sheridan, WY <br />West Area Disturbed Drainage, North Decline Final Reclamation <br />Powderhorn Coal Company <br />BASIN CHARACTERISTICS <br />_.~ • <br />DRAINAGE AREA (SQ. MI.) = 0.008 <br />STREAM LENGTH (MI.) = 0.120 <br />ELEVATION DIFFERENCE (FT.) 27.000 <br />RUNOFF CURVE NUMBER, CN 87.000 <br />MINIMUM INFILTRATION LOSS (IN./FIR.) = 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 (PEAX FLOW•IN CFS FOR UNIT•HYDROGRAPH) _ <br />RESULTANT HYDROGRAPH VALUES <br />PEAK DISCHARGE (CFS) ? <br />RUNOFF VOLUME (ACR£-FEET) - <br />TIME TO PEAK DISCHARGE (HR) _ <br />USED SCS TYPE II 24-HOUR GENERAL STORM <br />CN Calculation - Roads (dirt), C Soil Group 87 <br />Sediment Volume - It is assumed that the reduced storage requirements . <br />associated with seeding and mulching this area in the fall of 1992 will <br />a]low adequate sediment storage capacity. <br />1.80 <br />0.06 <br />0.06 <br />0.01 <br />0.04 <br />O.lI <br />92.1 <br />5.59 <br />0.32 <br />12.01 <br />~, • <br />4.:. <br />13-3-3 (Revised IO-7-92) <br />