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• TABLE 7-6e-5 <br />Weighted "k" Factor <br /> <br />Soil Type or Area <br />"k" Factor Area <br />(Acres) <br />"k" x Area <br />2VF, 2VE, 2UD 0.30 4.05 1.21 <br />XBF, X8E, X8D, XSC 0.17 17.29 2.94 <br />Topsoil Removed 0.27 88.73 23.96 <br />Active Pit and Spoil 0.16 29.0 4.64 <br />Non Topsoiled Regraded From 0.18 45.07 8.11 <br />Reclaimed 0.20 63.4 12.68 <br />247.54 53.54 <br />wt. "k" Factor = 53.54 = 0.22 <br />247.54 <br />Precipitation and Storm Type <br />The precipitation amounts for the Seneca II Mine for the storm durations <br />• used in the design are listed below: <br />10-year, 24-hour - 1.60 inches <br />25-year, 24-hour - 2.09 inches <br />100-year, 24-hour - 2.40 inches <br />These rainfall amounts were obtained from the NOAA Precipitation Frequency <br />Atlas Precipitation-Frequency Atlas of the Western States Volume II - <br />Coiorado, 1973. A standard SCS Type II storm was utilized for each <br />analysis. <br />Unit Hydrograph and Surface Condition <br />The SEDIMOT II computer program provides three unit hydrograph shapes to <br />choose from in determining the runoff characteristics of a watershed. The <br />disturbed hydrograph (No. 1) was used for the disturbed and reclaimed <br />areas. <br />Time of Concentration <br />• The time of concentration, tc, is defined as the time required for water <br />to flow from the hydraulically most remote point in the watershed to the <br />watershed outlet. The runoff time of concentration was calculated using <br />the following equations (Barfield, 1983): <br />7-6e-6 <br />