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Wesf EIk Mine <br />Table 52 Summary of F-Seam Mine Discharge Water Quality Data <br />• <br /> <br />Location Total dissolved Solids' pH <br /> Min. Max. Mean Min. Max. Mean <br />Sylvester Gulch Fan Site 264 2,220 511 6.8 8.0 7.7 <br />East PortalZ 354 724 547 7.2 8.2 7.6 <br />West Portal 328 2,088 1,029 8.0 8.2 8.1 <br />1 Total dissolved solids measured in 19811 and 1987. Total dissolved solids trot measured before 1986, bu[ calculated from measured <br />conductivity. <br />Z Reported for years 1984 and 1985. <br />It is beyond the scope of this permit application to predict the combination of discharge rates <br />and river flow conditions that would occur during subsequent years; however, a "worst case" <br />analysis was conducted. The 7-day, 10-year low flow of approximately 30 cfs was used for <br />the North Fork streamflow. Estimates of pond water discharges were based on the maximum <br />capacity of the underdrain systems. <br />The use of water for its designated uses will not be impaired by pond discharges. <br />Seepage From Waste Rock or Coal Refuse Piles <br />Infiltration and percolation of precipitation and runoff through waste rock piles can be a <br />potential source of dissolved solids and pollutants. Effects of seepage from waste rock piles on <br />the North Fork were evaluated for the upper North fork watershed in the CHIA (1992). <br />According to this study, the chemistry of any leachate would likely be sodium sulfate water <br />with low metals concentrations and neutral pH. <br />A CDMG study determined that "the contribution of salts to leachate from existing and <br />proposed waste piles along the North Fork of the Gunnison River would be insignificant..." <br />Furthermore, the study found that impacts from seepage were probably over-estimated since <br />most seepage would result from snowmelt and occur during times of higher than average <br />streamflows. <br />Discharge of Mine Water <br />• <br />Mine water can be discharged at several locations: Sylvester Gulch Fan site (NPDES outfall <br />011), Lone Pine Gulch (NPDES outfall 013), direct discharge to the MB-1 emergency spillway <br />or into pond MB-1 (NPDES outfall 016), the Sylvester Gulch pumping facility (NPDES outfall <br />017), and pond MB-2R (NPDES outfall 004). Discharged mine water ultimately ends up in <br />the North Fork. Table 52 shows a summary of F-Seam mine water quality for discharges from <br />the Sylvester Gulch fan site and water sent to MB-1 from the east (Portal No. 2) and west <br />2.05-195 RevisedJw. 1995 PROd: Revised Nov. /998 TR80; (/98 PR08 <br />