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~-, <br />2.7.5.2a GROUND WATER QUALITY <br />As a result of previous environmental investigations and a continuing water <br />quality monitoring program at the Trapper Mine site, a relatively good base of data <br />exists on [he quality of ground water. Water quality has been monitored at nine new <br />and eight existing sites in the eastern half of the Trapper permit area. The sites <br />are GP-1 through GP-9, GC-1 through GC-3, COY, P-1, P-3, P-5 and P-8. <br />Table 2.7-22a presents the water-quality results from the wells in the eastern <br />half which are used to define the baseline conditions in this area. Updated ground- <br />water quality for the wells in the western section of the permit area is presented <br />in Section 4.8. <br />The total dissolved solids (TDS) of the ground water in [he eastern half of <br />the permit area varies from concentrations slightly greater than 500 mg/1 to <br />approximately 4000 mg/1 in the Lewis Shale a[ well P-3. The TDS of the water in <br />each aquifer in general would be expected to be the lowest near the outcrop of a <br />particular aquifer and greatest down-dip on the north side of the mine. <br />OR Aquifer <br />The TDS of the QR aquifer in the eastern half of the Trapper Mine has been <br />defined at wells GP-1, GP-5 and GP-6. Wells GP-1 and GP-6 are within a few thousand <br />feet of the zero saturation line in the QR aquifer. The TDS of water at these two <br />sites is similar at approximately 600 mg/1. Figures 2.7-28a and 2.7-28b present the <br />TDS concentrations for the last year of the QR aquifer at wells GP-1 and CP-6, <br />~~ <br />2-520a <br />