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Mountain Coa! Compam• 1999 Mnual Hydrology Report West E!k Mine • Groundwater Impacts The goundwater 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 twenty-six 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 aze shown in Appendix F. Water level and quality data obtained in WY99 for each of the monitoring wells can be found in tabulaz form in Appendix G. Mining in longwall panel 10 during WY98 appears to have had a minor effect on well SOM-80, completed in the Barren Member. In WY99, water levels appear to have leveled out approximately four feet below the historic elevation. Also, the water level in well SOM-2-H, completed in the F-Seam, continue to drop at the same rate as in WY98. Mining activities in longwall panels 12 and 13 may have increased the fracture volume in the zone of influence for this well. Mining activities in WY99 appear to have affected the water level in well RAV-4b, which is completed in the B-Seam near the Box Canyon Mains. During development of the Box Canyon Mains, the water level in RAV-4b dropped over one hundred feet. The most likely explanation is that during development mining in the Box Canyon Mains, the Oliver No. 2 fault zone was encountered in July 1999 and produced inflows. The projection of the Oliver No. 2 fault zone to • the northeast passes near RAV-4b. Encountering the fault zone inflows in the Box Canyon Mains likely reduced water pressure in the fractures and the water level in RAV-4b is likely equilibrating near the elevation where the fault was encountered. However, there is no practical significance to the impact since the B-Seam is not used as a water source and the extent of the impact is likely confined to the vicinity of the mining. Also, well RAV-4b is completed within one of the planned longwall panels and will likely be destroyed by longwall mining. None of the other wells in the monitoring progam showed indications of impacts that could be related to mining during WY99. In addition, the water quality data collected during WY99 did not show any anomalous values that would indicate mining impacts. 831-091.510 Page25 Wright R'arerEngineers