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Mr. Clapper and Mr. Romig <br /> September 24, 1996 <br /> Page 3 <br /> The return pipeline consists of a combination of 4-inch diameter PVC pipe and HOPE <br /> pipe. This pipeline runs from the pump station up the downstream face of the dam, and <br /> discharges into the Dam 4 water pool. A backup diesel generator capable of running one <br /> of the 15 horsepower pumps is located In the pump station. The small amount of seepage <br /> flow that collects at the base of the secondary containment wall can be pumped either to <br /> the wet well or the primary pond by two small dewatering pumps. <br /> Historic and Future Seepage.Flog <br /> Climax personnel have maintained a detailed record of the pump hours for the two <br /> 15 HP pumps at the pump station. Review of these records Indicate that the historic <br /> seepage rate varies between 10 and 20 gpm throughout most of the year. However, the <br /> records also Indicate that the total flow that is tributary to the seepwater collection system <br /> increases to over 300 gpm during the peak of the snowmelt period. The vast majority of <br /> this water Is surface runoff and not seepage through the dam. The 30 HP pump has been <br /> used in the past when the inflow exceeds the capacity of the two 15 HP pumps operating <br /> in parallel (approximately 250 gpm). <br /> In the future, the inflow to the seepwater collection system that results from <br /> precipitation and snowmelt runoff will be similar to the historic flows. The seepage flow, <br /> however, is expected to increase as the water level in Eagle Park Reservoir will be <br /> significantly higher than the historic water levels. Another factor that will result in <br /> increased seepage is the removal of the 60-80 feet thick layer of tailing from within the <br /> Impoundment. The silt and clay size tailing particles could have created a fairly <br /> impermeable barrier within the impoundment in the past. Removal of this material will <br /> most likely result in an increase in the effective permeability through the embankment and <br /> foundation. Using a conservative embankment permeability of 1 foot/day and conventional <br /> flownet methods, the future embankment seepage was estimated to be as much as 210 <br /> b0' d ZOO' ON Zb: TT 96 bZ daS Z'OK-T9Z-202-T : 131 JosSd '8 .gal aaym ' m' m <br />