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As mine drainage encounters oxidized and weathered roof, floor, coal, and gob <br />materials, there is a potential for changes in groundwater chemistry and <br />increases in TDS and the concentrations of specific chemical constituents. <br />Dorchester, in response to permit adequacy questions submitted in 1982. <br />compared water quality data for a monitoring well in the Pine Gulch unit of <br />the Vermejo formation with similar data far dewatering flows from the north <br />dewatering well. This comparison which is included in Exhibit T, Hydrologic <br />Information, indicated increases in pH, iron, manganese, sulfate, sodium and <br />dissolved solids for mine drainage flows. These results are consistent with <br />analyses of roof and floor materials as discussed in Section 2.04.b, Geology <br />Description. <br />As described in Section 2.04.7, Hydrology Information, groundwater in both <br />the mine and loadout areas is of a sodium sulfate type. Increases in both <br />sodium and sulfate constituents will not change groundwater chemistry <br />although they could result in a shift toward a more dominant groundwater <br />type. While various chemical constituents of the groundwater may increase as <br />a result of mine drainage. these increases will not effect groundwater use. <br />Due to the limited volume of groundwater drainage with respect total flows <br />within the groundwater basin as previously discussed, minor changes in <br />groundwater chemistry and levels of certain constituents are not expected to <br />significantly effect overall groundwater quality. <br />It should be noted that potential impacts on groundwater chemistry and <br />individual chemical constituents are not unique to the Southfield operation <br />and can be considered as representative of other abandoned underground mining <br />operations in this same area. It is significant that much of the groundwater <br />use in this area involves recovery of groundwater <br /> <br />C :\TMlB60l V OL.2iREC.P LN <br />""^"°^a~iaam WP51/cmc 2.05.b•45 Revised - 9!30!94 <br />