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some TDS measurements were made. Recent samples have indicated an <br />increase in TDS for the Third White Sandstone water in this area <br />although the 1988 value shows a slight decrease from the 1987 <br />value. The changes are thought to be natural due to the large <br />distance from mining to this area. The third well, GC3, at this <br />site monitors the alluvial aquifer and TDS values from this well <br />have typically varied over a larger range because this aquifer is <br />influenced more by changes in recharge conditions (see Figure B- <br />7). <br />Well GD1 is the water supply well for the mine and is <br />completed in the Twenty Mile Sandstone. The TDS plot (Figure B- <br />8) for water from this well shows that the values have been <br />similar for the last four years. Well GD1 was reactivated into <br />use in 1985 as the water supply well for the Trapper Mine and <br />Craig Station power plant. Prior to 1985, its use was sporadic. <br />Well GD2 is completed in the OR aquifer downgradient of recent <br />mining of these seams in the D Pit. The TDS measurements (see <br />Figure B-9) for this well show a fairly steady concentration <br />since 1982 indicating that mining in the QR aquifer has not <br />affected water quality downgradient in this area. Well GD3 was <br />completed in the backfill aquifer during 1988 and upgradient of <br />well GD2. The OR coal seam was previously mined in this area. <br />Only two samples have been collected from well GD3, but the TDS <br />in the backfill aquifer is only slightly higher than downgradient <br />at well GD2. Figure B-10 presents the TDS data for well GD3. <br />The GE cluster of wells are used to monitor the OR, HI and <br />Third and Second White Sandstone aquifers (see Figures B-11, B-12 <br />3-3 <br />