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Mountain Coo! Comparry 1997 Annual H}'drology Report West Elk A4ine • and to protect the water quality of the North Fork during low flows, MCC began to pump mine water into the area created by mining the 1NW through 7NW longwall panels. For a more complete description of the NW Panels sealed sump and associated probable hydrologic consequences, please see Technical itevisron 80. As shown in Figure 6, there was an estimated 375 acre-feet of mine water pumped into the NW Panels sealed sump between November I I, ] 996 and the beginning of March 1997. This storage volume essentially "filled" the sump up to the elevation of the ventilation seals at the northwest end of the 7N W longwall panel, also known as the Lone Pine seals. Mine Water Balance Figure 6 shows the mine water balance components for WY97. The most significant event that occurred in WY97 was the inflows from the 14 SEHG fault and continued inflows from the B East Mains fault, which greatly affected the mine water balance. These inflows effectively doubled the volume of water that the West Elk Mine has historically managed. North Fork diversions of 372 acre-feet were higher than previous years due to increased production and, perhaps some losses due to breaks in pipelines from the mine site landslide. The amounts of the diversions were not affected by the increased mine inflows. The total volume of water entering the mine from pond FW-],inflows from the 14 SEHG fault and the B East Mains fault, and other minor inflows was approximately 1,054 acre-feet. Most of the water discharged from the mine was sent to ponds MB-1 and MB-2R for treatment • and discharge to the North Fork. The combined dischazge volume for ponds MB-1 and MB-2R was approximately 555 acre-feet during WY97. This volume includes about 9 acre-feet of treated effluent from the WWTP and stormwater and snowmelt runoff. During WY97, approximately 36 acre-feet of mine water were discharged via pond FW-1 spillway. This water was "cleaz" 14 SEHG fault inflows and the dischazges were made under authorization of the CWQCD. Water is added during dust suppression spraying for the longwall and for the continuous miner operations. This water is approximately 1.5 percent by weight of the coal produced. With the 6.2 million tons of product and gob that left the mine workings in WY97, there was about 68 acre-feet of water included. Other losses included added moisture to the ventilation air and absorption into gob and floor materials. MCC continues to collect minor colluvial inflows in the F-Seam workings and dischazges the water to Sylvester Gulch per CDPS permitted outfall O1 lA or to ponds MB-1 or MB-2R. During WY97, approximately 7 acre-feet of water were dischazged to Sylvester Gulch. The total volume of water leaving the mine or stored within the NW Panels sealed sump during WY97 was 1,068 acre-feet, which compazes well with the 1,054 acre-feet of water that entered the mine during the same period. It should be noted that the pond discharge volumes also include stormwater and snowmelt runoff: However, considering that the initial high volume 14 SEHG fault inflows could only be based on visual estimates, the neaz-balance of the water • 8 1-0 .~50 Page Wrig 1 ater ngineers