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• The drainage area above the reclaimed mine site would be <br />considered; 1) Pasture, grassland, or range-continuous forage for <br />grazing; or 2) Meadow-continuous grass, protected from grazing and <br />generally mowed for hay. Based on a visual inspection performed by <br />J. E. Stover during June 1996, the fields above the mine site have <br />a hydrologic condition which is good, >75~ ground cover. <br />Table 2-2c - Run-off curve numbers for other agricultural <br />lands. Cover type pasture grassland, or range-continuous <br />forage for grazing in good condition, soil type C, yields a <br />curve number of 74. Cover type meadow-continuous grass, <br />protected from grazing and generally mowed for hay in good <br />condition, soil type C, yields a curve number of 71. <br />A curve number of 74 was selected for the upland area. <br />The computer output for the peak discharge calculation of 27.5 cfs, <br />based on the computer program Stordi, follows: <br />Project Title <br />= Peak Flow Calculations <br />Pond Spillway <br />Watershed Data for Watershed # Reclaimed Area and <br /> Upland Area Combined <br />Curve Number = 74.0 <br />Area 75.0 acres <br />• <br />Hydraulic Length 2350 feet <br />Elevation Change = 240 feet <br />Concentration Time = 0.14 hours <br />Concentration Time Type = SCS Upland Curves <br />Unit Hydrograph Type = Agricultural <br />Total Area = 75.0 acres <br />Storm Data <br />Total Precipitation = 2.3 inches <br />Storm Type = SCS Type 2, 25 Yr 24 Hr Storm <br />Peak Discharge = 27.47 cfs <br />Discharge Volume = 3.12 acre-feet <br />As stated above, the capacity of the sediment pond emergency <br />spillway is 49.94 cfs. The sediment pond emergency spillway can <br />easily handle the peak discharge (27.47 cfs) generated by the 25- <br />year 24 hour storm event. <br />• 106a (Rev. 8-21-96) <br />