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aLTERNATE DRAINAGE AREAS <br />RUNOFF CALCULATIONS <br />~•~ <br />.! <br />~EFERENCE: Trihydro, Ver. 2.2, Western Water Consultants, Sheridan, WY <br />East Area Distrubed Draiange, North Decline Final Reclamation <br />Powderhorn Coal Company <br />BASIN CHARACTERISTICS <br />~y. • <br /> <br />DRAINAGE AREA (SQ. MI.j 0.002 <br />STREAM LENGTH (MI.) = 0.079 <br />ELEVATION DIFFERENCE (FT.)• = 3.000 <br />RUNOFF CURVE NUMBER, CN = 87.000 <br />MINIMUM INFILTRATION LOSS (IN./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.) = 0.09 <br />ADJUSTED TIME OF CONCENTRATION {HR.) = 0.09 <br />DURATION OF EXCESS RAINFALL, D (HR.) - = 0.01 <br />TIME TO PEAK (HR. ) = 0.06 <br />BASE TIME {HR.) 0.16 <br />QPEAK (PEAK FLOW•IN CFS FOR UNIT•HYDROGRAPH)• = 16.0 <br />RESULTANT HYDROGRAPH VALUES <br />PEAK DISCHARGE (CFS) 1.36 <br />RUNOFF VOLUME (ACRE-FEET) = 0.08 <br />TIME TO PEAK DISCHARGE (HR} = 12.01 <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 />allow adequate sediment storage capacity. <br />13-3-4 <br />(Revised 10-7-92) <br />