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• Basin A3 —A3 is the area west of the impoundment that includes the sewage <br /> treatment plant and fuel storage facilities. This area is 3.04 acres. The total <br /> acreage of the three sub-basins is approximately 8 acres. <br /> 2.3.2.2 Snowmelt Runoff <br /> Figures 1a and 1b in Appendix A illustrate the results of the snowmelt depth <br /> evaluation using the Berthoud Pass SNOTEL data. Figure 1a summarizes the <br /> data in histogram format. There was one day during the 12 year period when <br /> precipitation exceeded 3 inches in a 24 hour period. This event was set aside, <br /> as it was a rain event that was not accompanied by significant snowmelt. <br /> Otherwise, the maximum 24 hour combined rain and snowmelt depth was about <br /> 2.4 inches. <br /> Figure 1b shows a synthesized hydrograph that reduces the 24 hour data to a <br /> • daytime depth-duration event. Snowmelt during the spring thaw is not expected <br /> to last more that a few daytime hours at the mine site. A thaw period of 5 hours <br /> is believed to be a reasonable minimum period. The intensity time for a 5 hour <br /> thaw period is illustrated on the top graph in Figure 1b. This graph also shows <br /> the effect of infiltration. A constant infiltration rate of 0.09 inch/hour was used. <br /> This figure is slightly lower than a rate that was calculated using known data at <br /> the Climax Mine. <br /> 2.3.2.3 Rainfall Runoff <br /> The results of rainfall runoff evaluation are presented in Figures 23 through 2e in <br /> Appendix E. As previously stated, the rainfall depths are based on values <br /> published by NOAA. The Rational Method was used to calculate the runoff <br /> rates. <br /> s <br /> 23.1999 <br /> TR.d <br /> TR.tlx <br />