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Moro and Assoelafes, LC <br />• 4.4.1 Isotopic Compositions <br />The S'H and 5180 compositions of surface waters, springs, wells, and in-mine groundwaters <br />are listed in Table 5 and are plotted on Figure 8. All water, except SOM-128-H, G-38 and <br />SOM-2, plot near the M WL, suggesting a meteoric recharge origin (i.e. rain and snow). The <br />samples from well SOM-128-H and spring G-38 plot in the region of evaporative water and <br />are believed [o have undergone evaporation. The cause of the deviation from the MWL of <br />sample SOM-2 is unknown. <br />In many groundwater investigations of coal mining areas in the Wasatch Plateau and the <br />Book Cliffs in Utah, we have found that in-mine groundwaters have isotopic compositions <br />that are distinct from spring and stream waters. A similar pattern is observed in the data from <br />• the West Elk Mine. Isotopic compositions of waters in [he vicinity of the mine cluster in <br />three general clusters with some overlap. The clusters include: <br />1. surface water and alluvial and landslide spring water, <br />2. Barren Member wells and in-mine Rollins Sandstone discharges, and <br />3. F-, E-, and B-Seam wells. <br />The surface water and spring water cluster, which mostly lies below and sub-parallel to the <br />MWL, generally has the most positive plotting location (Figure 8). Excluding the G-38 <br />sample, which underwent evaporation aRer discharge to the surface, the mean S'`H and 5180 <br />compositions of [his cluster are -15.5 and -117.3%0, respectively. The isotopic composition <br />of Barren Member well SOM-80 plots in the surface water and spring water cluster. This <br />• plotting location is consistent with chemical and physical attributes of the well. The top of <br />Characterization ofGroundwater Systems in the Vicinity of the West Elk Mine. Somerset, Colorado <br />29 January 1999 <br />Page 52 <br />