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<br />I!. Water Qaa(irv Impact <br />Groundwater <br />New Elk Mine <br />The Probable Hydrologic Consequences section of the New Elk permit made an estimate of the <br />impact of backfilling a short reach of the Middle Fork of the Purgatoire River channel with mine <br />waste, on adjacent alluvial water quality. This estimate predicted that concentrations of calcium, <br />sodium, sulfate and total dissolved solids would initially increase to 72 mg/I, 158 mg/I, 194 <br />mg/1, and 820 mg/1, respectively, based on a weighted average analysis utilizing column leach <br />test results and existing water quality in ALl-1 and AL2-1. The leach tests of the waste <br />suggested that a highly saline sodium sulfate water would be mixing with a low salinity calcium <br />bicarbonate water. Samples taken at site PAW-2 located downstream from the backfill, shows <br />maximum concentrations of calcium, sodium, magnesium, sulfate and total dissolved solids of <br />139 mg/I, 89 mg/1, 153 mg/1 and 671 mg/1, respectively. PAW-2 is a calcium bicarbonate water <br />which appears to have been effected less by influence from sodium and sulfate than originally <br />projected. This is confirmed by a review of PAW-3 and PAW-4, which are alluvial wells <br />located within the backfill itself. PAW-3 is a sodium bicarbonate water while PAW-4 is a <br />calcium bicarbonate water. <br />• Figure 10 compares the water quality of the upstream alluvial well, PAW-1 with the downstream <br />alluvial well, PAW-2. PAW-2 is considerably more saline, with higher concentrations of all <br />major cations and anions, but comparatively higher concentrations of sodium and bicarbonate. <br />Conclusion <br /> <br />Water quality impacts from the New Elk and Golden Eagle Mines are having a practically <br />imperceptible effect on the Purgatoire River (Figure 10). The predominant source of this impact <br />is the contribution of a saline, sodium bicarbonate mine water discharge to the river. Other <br />sources include a minor amount of drainage from two waste piles at New Elk, backfilling of a <br />short reach of the Middle Fork of the Purgatoire with waste and one waste pile at Golden Eagle. <br />Water quality within the alluvium located on the south side of the river exhibits elevated <br />concentrations of all parameters. Sodium concentrations have increased more than other <br />parameters, but do not appear to have created a limiting situation associated with SAR. <br />33 <br />