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Mato and Assoclales, LC <br />• The TDS and solute composition data indicate that surface and groundwaters belong to <br />chemically distinct groups, which are discussed below. <br />4.2.2.1 Streams <br />Approximately 17% of the monitored sites are streams. Stream waters are low TDS (mean <br />258 mg I'; Table 3), no dominant cation-HCO; type waters (Figure 7a). All of the stream <br />waters have Na' contents appreciably greater than their Cl- contents, indicating ion exchange <br />(Eqs 9 and 10). The major anion in the Mancos Shale stream waters is SO;- indicating the <br />presence of either gypsum or anhydrite (Eq. 5). The TDS contents of the stream waters can <br />not be statistically distinguished from each other on the basis of their underlying lithology <br />(Table 4). <br />• <br />4.2.2.2 Springs from Quaternary Sediments and Landslide Deposits <br />Approximately 30% of the monitored sites are springs, which issue from either Quatemary- <br />age sediments or landslide deposits. Most of the springs issue from either landslide deposits <br />located on either Barren Member or Upper Coal Member bedrock (Plate 2). The <br />groundwaters have a mean TDS of 585 mg l' (Table 3) which is statistically greater than <br />both creek waters and groundwaters issuing from Barren Member bedrock springs (Table 4). <br />There are not sufficient springs issuing from the Upper Coal Member to perform statistical <br />analyses. We suspect that the elevated solute contents of these groundwaters relative to <br />groundwaters issuing from Barren Member springs are the result of increased opportunity for <br />contact with soluble minerals, which is the result of the mixing of sediments during landslide <br />• movement. The groundwaters are generally of the Na`-HCO; type with lesser amounts of <br />Characterization of Groundwater Systems in the Vicinity of the West Elk Mine, Somerset, Colorado <br />29 January 1999 <br />Page 41 <br />