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The projections are revised to utilize a mean low flow <br /> of 4 cfs for the Purgatoire, and 0.707 cfs of mine water <br /> discharge at build-out for the life-of-mine. The highest <br /> concentrations of parameters observed in the discharge from GE- <br /> 002 oiere added to the mean concentrations of parameters at <br /> Stonewall in a weighted average approach. Predictions of water <br /> quality for existing conditions and the life-of-mine are <br /> compiled on Table 10 within the 1994 report in Exhibit e. <br /> Neither the reported data nor the predicted values exceed <br /> recommended water quality criteria, receiving stream standards <br /> and do not present a threat of material damage from mining. <br /> An estimation was made of the effect of the Golden <br /> Eagle coal development waste pile on the North Fork of the <br /> Purgatoire, based on a hydrologic balance summary prepared by <br /> Waste, Water and Land in 1980 (Exhibit 6) The annual average <br /> precipitation at the Golden Eagle Mine is 16.92 inches, and <br /> approximately 3.77 inches are lost to evaporation and <br /> sublimation during winter months. Deep percolation in most <br /> years will be essentially zero, as all precipitation will <br /> evaporate from the soil. During wet years, as much as 0.72 <br /> inches of water may be attributed to subsurface runoff. As the <br /> total area of the waste pile is 23.44 acres, the estimated <br /> total subsurface runoff during a wet year is approximately 1.41 <br /> acre-feet. In a wet year, the computed deep percolation of <br /> 1.41 acre-feet year converts to a mean discharge of 0.059 cfs <br /> over a 30 day period, and this discharge will enter the stream <br /> during the high flow period of spring runoff. <br /> An estimation of the worst case scenario of deep <br /> percolation through the waste pile from a wet spring being <br /> applied to low flow conditions (4 cfs) along the North Fork of <br /> the Purgatoire River was developed using a weighted average <br /> approach. Baseline water quality was assumed to be represented <br /> by average quality reported at the USGS gage at Stonewall, <br /> Colorado. Waste pile water quality was assumed to match a <br /> sample acquired from a seep at the New Elk Mine in 1980 and <br />• listed in Table 13 of the 1980 WWL Report in Exhibit 6. In the <br /> 2.05-40 (Revised 04/27/94) <br />