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Mountain Coal Compom• 2000 Annual Hydrology Report West Elk A4ine As pumping continued in WY00, the quality of the water from the Lone Pine pipeline has been • good. There were no exceedances of the CDPS dischazge limits or failures of the biomonitoring tests during WY00. Discharge via the Lone Pine pipeline ceased on June 8, 2000, when the water began draining to the NE Panels sealed sump. NE Panels Sealed Sump During WY00, MCC completed a borehole connecting the northeast comer of the NW Panels sealed sump with the northwest comer of the NE Panels sealed sump. The borehole allowed the majority of the water stored in the NW Panels sealed sump to be gravity drained to the NE Panels sealed sump. A vertical shaft was constructed extending down from Sylvester Gulch into the NE Panels sealed sump. Water was then pump out of the sump via the mine water pumping facility (MWPF) and discharged to Sylvester Gulch. Since the pumps were sized to handle potential flows from another large fault, the water in the sump is evacuated within a few days. Samples of Mine Water Inflows During WY00, sampling of mine water inflows was hampered by the location of the inflows. The fault inflows occurred at low places in the mine floor, which allowed mixing of belt line water, process, water, road maintenance (magnesium chloride application), and rock dusting operations to mix with the inflow water. Representative samples of the inflows were obtained during WY00. • Mine WaterBalarce Figure 6 shows the mine water balance components for WY00. The major factor affecting the water management at the mine during WY00 was the thermal event. North Fork diversions of 705 acre-feet were significantly higher than in previous years due to the efforts to flood the azea of the mine affected by the combustion. The total volume of water entering the mine from pond FW-l, inflows from the 14SEHG fault and the B East Mains fault, and other minor inflows was approximately 657 acre-feet. The majority of mine water was pumped to the NW Panels sealed sump and ultimately discharged via the Lone Pine pipeline until June 8, 2000. The volume discharged from the NW Panels sealed sump was approximately 216 acre-feet. When the borehole was opened on June 8, 2000, water was allowed to drain into the NE Panels sealed sump. The water was then pumped out of the mine through a vertical shaft to the mine water pumping facility (MWPF), where it was discharged to Sylvester Gulch. Discharge via the MWPF commenced on July 17, 2000 and continued through the end of the water yeaz, during which time 325 acre-feet of water were discharged. During WY00, pond MB-1 discharged approximately 1.6 Mgal to the North Fork on April 13, 2000. The remainder of the water from the surface operations was sent to pond MB-2R for treatment and discharge to the North Fork. The discharge volume for pond MB-2R was approximately 112 acre-feet during WY00. This volume includes about 4 acre-feet of treated effluent from the W WTP and stormwater and snowmelt runoff. 83l -03?.550 Page 20 Wright Warer Engineers