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Mountain Coal Company 1997 Annual Hydrology Report {i'es~ Elk hfine roof inflows were reported to have initial inflows of less than 5 gpm which later diminished to • dry or damp areas. Inflows from the roof and rib of [he ] 0 Northeast headgate at Cross-cut #20 were initially observed at 80 gpm later decreasing to the current inflow rate of approximately 35 gpm. The most significant groundwater inflows occurred on January 20, 1997 when MCC intercepted a southwest to northeast-trending fault in the 14 Southeast Headgate, as discussed previously. By the end of January, this inflow had diminished to approximately 1,750 gpm and to 800 gpm by the first week in February. By the end of WY97 inflows had decreased to approximately 200 gpm. MCC worked diligently to control the inflow for the safety of the miners and to minimize the impact on the North Fork and future mining operations. After four days of round-the-clock pumping and pipe installation, anon-advancing "shoreline" was established within the mine (i.e., on January 24, 1997, the outgoing pumping rate was equal to the inflow rate). Initially, the inflow water was pumped to MCC's sedimentation ponds, MB-1 and MB-2R. Because of the magnitude of the inflow, MCC anticipated having to dischazge some of the mine inflow water either via the sedimentation ponds, potentially without sufficient settling time, or directly to the river (after receiving approval by WQCD). As a result, water sampling from above and below the dischazge points was conducted to establish baseline conditions. A biological assessment conducted by W WE before and after the discharges showed that there was no significant impact to the river. Lab analysis showed the fault water to be moderately alkaline, and to contain sodium • bicarbonate, calcium carbonate, high conductivity (>4,000 µmhos/cm) and high total dissolved solids concentrations (2,950 mg/L). These values are higher than the parameters associated with the fault encountered in the B East Mains and the stable isotopic compositions aze also different, leading to the conclusion that the 14 SE Headgate fault was a different system. The 80°F to 84°F temperature of the groundwater in the fault system indicates that it was in contact with an area having a more exaggerated geothermal gradient that might be found near igneous intrusives such as those associated with Mount Gunnison. The water is apparently contained in fractures in the Rollins Sandstone surrounding each fault system, which are hydrodynamica]ly separate. The waters are thousands of years old and are likely recharged at the cliff face near Minnesota Creek. The waters travel extremely slowly and the ultimate destination is unknown, but is likely downdip along each fault system. NW Panels Sealed Sump As discussed in the 1996 AHR, due to the presence of a suspended colloid in the mine water that was exceedingly difficult to flocculate and settle, MCC began to spray alum on the surface of the sedimentation ponds in order to meet TSS discharge limits. While this solution was recognized as impractical as a long-term solution due to the large volumes of floc produced, it was the most effective chemical of many tried to reduce TSS concentrations enough to allow compliance discharges. • ]n November 1996, however, this method was no longer feasible since the surfaces of the sedimentation ponds were frozen. Therefore, in order not to violate its CDPS discharge permit 8 - .9 age rig t ester ngrneers