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West Elk Mine • Pre-mining and post-mining water samples were collected from Wells 1 and 2 at Site 1 to evaluate any changes in groundwater quality as a result of mining. The data showed that there were no major changes. Site 2 revealed little appreciable change in groundwater quality due to undermining, although it appeazs that hardness and calcium decreased and sodium increased after mining. At Site 3, there were no major changes in water quality although there were increases in hazdness and sulfate after mining. At Site 4, water quality was not altered appreciably" (Johnson 1992). Five observation wells, which were drilled above two adjacent longwall panels on Cambria, Pennsylvania, were monitored. Samples of wellwater were collected before and after mining progressed through the azea. "This study shows that (a) the observed changes in groundwater chemistry did not affect the potability of the water..." (Matetic and Trevits 1992). Water Stored in Sumns A summary of events leading up to the decision to store large volumes of water in large capacity sumps within the mine can be found in the previous section entitled Groundwater Quantity Effects. The following section describes how, due to the unexpected inflows from the BEM and 14HG Faults, previously mined NW longwall panels are used to store water volumes which exceed the hydraulic capacity of the current treatment facilities. These panels will be used for storage to optimize the mine water treatment system. also plans to use the NE and Box Canyon Panels sealed sumps for storage of water in the same manner, A distinct difference in the fault inflows and other "typical" mine inflows is water temperature. Typical mine inflows are about 68°F to 72°F, and the fault inflows were approximately 84°F and 88°F, for the BEM and 14HG Fault inflows, respectively. A comparison of the BEM Fault water with both "typical" groundwater quality in the B Seam is provided in Table 54. These Tables demonstrate the similarity in water quality and show that the fault water can meet MCC's NPDES discharge requirements without treatment, including the applicable temperature requirements. A description of the difficulties treating water containing a previously un-encountered colloid and the treatment processes attempted aze discussed in the previous section entitled Basis for Large Capacity Sump Use. While the source of this unusual colloid is not definitively known, MCC believes that the clay particles may be inherent in the coal seam in the eastern part of the mine. In recent years, mine dischazges through the existing treatment ponds have demonstrated an increase in alkalinity and conductivity (TDS). At the present time it is unclear what is causing the increase in TDS but it appears to be associated with mining rather than any change in groundwater chemistry. Ongoing investigations are under way to further assess the potential cause for these chemical changes. 1.05-250 Revised November 2004 PRIO