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• • • Movnlain Coal Company Groundwater Impacts 1998 Anuual Hydrology Report Wes16(k Mine The groundwater monitoring system at the West Elk Mine is shown on Map 2 and summarized in Table 4. Table 5 shows the completion information for the thirty-two wells that aze currently monitored at the West Elk Mine by the formation in which they were completed. These formations include: the alluvium and colluvium (unconsolidated materials), the Barren Member of the Mesa Verde, the F-Seam, the E-Seam, the B-Seam and the Rollins Sandstone. Graphical representations of the historic water levels observed at these monitoring wells are shown in Appendix F. Water level and quality data obtained in WY98 for each of the monitoring wells can be found in tabulaz form in Appendix G. Of the thirty-two wells that aze currently part of the groundwater monitoring program, valid data could not be collected from seven wells during WY98. Five of these wells were blocked or had pinched casings (SOM-38-H-1, SOM C-72-H, JMB-12, So.W-3, LP-1) and the other two had interference of water from sources outside the formation of interest (SOM-23-H-1 and SOM-23- H-2), The majority these wells (SOM-38-H-1, JMB-12, SOM-23-H-1, SOM-23-H-2, and LP-1) were removed from the monitoring program per TR85 in July 1998. Mining in longwall panel 10 during WY98 appeazs to have had a minor effect on well SOM-80, completed in the Barren Member. The well is located a few hundred feet north of panel 10, where the overbwden thickness is azound 600 feet. Over the past 10 years, water levels have shown seasonal fluctuations but have consistently been about 85 feet below the swface. In WY98, the water levels were approximately 4 feet lower. The timing of the decrease and the location of the well indicate that mining most likely affected the well. However, there is no practical significance to the impact since the Barren Member is not used as a water source and the extent of the impact is confined to the vicinity of the panels. The water level in well SOM-2-H, completed in the F-Seam, began to level out after declining roughly 100 feet over the past fow yeazs. This may indicate that there was an increase in available storage caused by fractwed rock, which has now been filled with a fixed volume of water. Continued water level observations may confirm this hypothesis. None of the other wells in the monitoring program showed indications of impacts that could be related to mining during WY98. In addition, the water quality data collected dwing WY98 did not show any anomalous values that would indicate mining impacts. 83 - Page rig i crier Engineers