1996-06-04_REVISION - M1977493 (9)

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2) West Gravity Line Flow As stated above, it was assumed that the runoff flow that has historically been decanted from Robinson Tailing Pond to Robinson Reservoir would not be allowed to flow to the Eagle basin in the future. However, we did assume that approximately 300 gpm of seepage flow would continue to enter Robinson Reservoir from the West Gravity Line. This flow rate was assumed to vary throughout the year, with 300 gpm being the maximum rate. 3) Natural Precipitation Runoff Calibrated runoff factors based on historical measured data was used in the computer model to synthesize the inflow from precipitation runoff within the area tributary to Robinson Reservoir. Added to this inflow was the runoff from the area that is tributary to Eagle Park Reservoir below the interceptor system. Until the clean-up of Eagle Park Reservoir is complete, this flow will have to be pumped up into Robinson Reservoir. 4) Seepage Flow from the Chalk Mountain Interceptor Previous hydrologic studies that have been conducted at the Climax Mine by Wheeler have indicated that the seepage loss rate from the interceptor system averages about 17 percent of the total intercepted flow throughout the year. Therefore, inflow to Robinson Reservoir from the Chalk Mountain Interceptor was assumed to be 17 percent of the flow intercepted from the areas naturally tributary to the reservoir. Chalk Mountain Dam seepage inflow was estimated to be fairly insignificant in comparison to the other inflow sources and was therefore neglected in this analysis. It should-be noted that the period of historic record used in the model includes 1984 which was an unusually wet year in terms of annual precipitation and snowmelt runoff. The May through August runoff volume in 1984 has been statistically estimated to be in excess of the 100-year runoff event. 6