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Sandstone and Vermejo Formations. The USGS well located from the proposed <br />mine is completed only in the Vermejo Formation located stratigraphically <br />above the Trinidad Sandstone. The water quality in the USGS well exhibits <br />over four times the magnitude of total dissolved solids as in well 29-4. The <br />increase in dissolved solids is attributed almost exclusively to sulfate and <br />associated cations of calcium, magnesium and sodium. The mine discharge, also <br />from the Vermejo Formation, exhibits levels of total dissolved solids and <br />sulfate significantly higher than in well 29-4 but lower than found in the <br />USGS well. <br />It is also important to note that ground water from the Ili well, the Montoya <br />dug well, which was completed in the Trinidad Sandstone downgradient of the <br />mine site, was found to be lower in total dissolved solids and sulfate <br />concentrations than was found in the USGS well or the mine discharge, EMD, but <br />higher than was found in the upgradient well 29-4. These results suggest that <br />the water quality in the Trinidad Sandstone is better than in the Vermejo <br />Formation and that recharge (and possibly evapotranspiration) of the water in <br />Trinidad Sandstone as it approaches the subcrop in the vicinity of the <br />proposed mine site may be causing sulfate and total dissolved solids <br />concentrations to increase. The recharge may be through the Vermejo <br />formation, through stream channel sediments and alluvial materials or through <br />soils directly overlying the Trinidad sandstone. Nevertheless, the fact that <br />the water quality in the Trinidad Sandstone is significantly better than in <br />the Vermejo Formation suggests that a significant portion of the recharge of <br />the Trinidad sandstone does not pass through the Vermejo Formation. <br />• <br />• <br />-5- <br />