2008-04-15_REVISION - M1980244 (309)

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• inch diameter HDPE pipes and four-inch diameter yellowmine pipes. The piping system is used to distribute solution to agricultural drip irrigation tubes on approximately 32-inch centers. Where the headers approach the edge of the liner in a manner that indicates a leak under pressure might escape the lined portion, the header may be covered with a piece of liner, with ore, or with other crushed rock. Solution typically is applied using drip irrigation; however, there may be periods when sprinkler-type wobblers will be used to apply solution to the ore. There will be a range of application rates as are suited to the pressure capabilities of the system. The application rates could range from 0.002 to 0.007 gpm under present designs. The average application is anticipated to be 0.003 gpm/ft2/min. 6.6 Valley Leach Facility Water Balance The water balance analysis for the entire VLF has been updated by Smith Williams Consultants to quantify the probable volume of water gained by precipitation, lost to evaporation, and retained within the ore matrix. The results are contained in Appendix 8, Volumes V and VI of this document, and summarized below. • The inputs to the water balance include barren solution applied to the VLF, precipitation falling on the VLF, and moisture contained in the ore as it is loaded on the VLF. The outputs included evaporative losses and differences between as-delivered ore moisture content and the ore field capacity. The input parameters are conservative and the water balance itself represents a convergence of maximum conditions to develop a conservative estimate for sizing of ponds under simultaneous operating flows and extreme contingency flows. As a result of the increase in ore height and the added solution from areas of Phase 5 which will report to the existing Phases I and II PSSAs, the capacity of the existing PSSAs was reevaluated. The results indicate that the existing Phases I, II, and IV PSSAs will contain all operation and contingency flows. The water balance results also establish the design criteria of the Phase 5 PSSA. This internal pond has been designed to contain the expected operating volume; an additional 10 million gallons of solution; 12-hour draindown volume that would occur if there was no pumping of solution from the PSSA; monthly mean precipitation levels using historic data at a 95 percent confidence level; precipitation from the 100-year, 24-hour storm event; and solution retained in the field capacity of the ore contained within the PSSA, plus five feet of freeboard. Water balance modeling predicts that the Phase 5 PSSA will fully contain all solutions, including • Cripple Creek & Victor Gold Mining Company Cresson Project Mine Life Extension 6-11