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• 2.7.5.2 Ground Water Quality <br />The U.S. Geological Survey, (Brogden and Giles, 1977) describes ground water from the Mesa Verde Group <br />as predominantly calcium and sodium bicarbonate types. Water which has contacted coals may be a calcium <br />sulfate type. Coal-contact waters may contain relatively high levels of fluoride, iron, manganese, selenium, <br />and sulfate. <br />As a result of previous environmental investigations and a continguing water quality monitoring program at <br />the Trapper Mine stte, a relatively good base of data exists on the quality of ground water. Water quality has <br />been monitored at five different locations at the mine site; Sites GA, GB, GC, GD and GE are shown on Map <br />M52. At some of these sites, water samples have been collected and analyzed at two or more wells. <br />The water quality characteristics for wells at each of the ground-water monitor sttes are given in Table 2.7-22. <br />Wells GA-1, GA-3, GA-4 and GE-1 are completed in the Q and R coal seams. Wells GB-3, GB-5, GC-1 and <br />GE-2 are completed in the H and I coal seams, while wells GB-2 and GG2 monitor the sandstone above the <br />H seam. The sandstone above the Q seam, the sandstone below the I seam and an alluvial system are <br />pertoreted in wells GA-2, GB-1 and GG3, respectively. Well GD-1 is completed in the Twentymile <br />Sandstone. The wells which have been monitored several times were selected as monitoring wells at the A, <br />B, C, D and E ground-water sites at the Trapper Mine. <br />• The general quality of ground water in the Trapper Mine vicinity appears to be good. Total dissolved solids <br />for most wells is between 500 and 1000 mgll, which means that the water is Gassed as Yresh" in the U.S. <br />Geological Survey classification. The dominant cation in all wells, except GE-1, is calcium. In Well GE-1, <br />sodium is the dominant cation, and the calcium content is quite low. The dominant anion in all wells Is <br />bicarbonate. The dominance of the calcium and bicarbonate species indicates that the water is relatively <br />hard. <br />• 2-483 <br />-- - P~'`~ - - - <br />~: <br />~ is~--- <br />~H__ - <br />