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Observed Ground Water Impacts Mine Inflows and Discharges Water is pumped from the underground mine workings to the ground surface at the No. 5 Mine well and the 7 North Angle well. Annual hydrology reports show the total discharge for the 5 and 6 Mines was a fairly constant 600 gpm during active mining in the eazly 1990s. After mining ceased in 1995, Bumped water was pumped down. In 1997 and 1998 pumping became intermittent, averaging less than 1 gpm. By late 2002, pumping was approaching an average annual rate of 600 gpm. The pumped mine water is discharged to the Williams Fork River at NPDES outfalls 003 (5 Mine well) and 024 (7 North Angle well). Monitoring data through 2002 collected at the outfalls indicate the mine water is consistently alkaline, with total dissolved solids less than 1800 mg/1, and low concentrations of iron and manganese. Trout Creek Sandstone Annual hydrology reports as recent as 2002 indicate no continuing mining- caused change in the Trout Creek Sandstone potentiometric surface or water quality. The water level in the Trout Creek Sandstone monitoring well (No. 5 Mine well) dropped 200 ft. during 1989 and 1990. The drop probably was caused by pumping of the three mine water supply wells completed in the Trout Creek, rather than by mining in the overlying E and F coal seams. The water level fully recovered in 1991 and then fluctuated 200 ft. in 1998. The fluctuation is probably not related to dewatering in the overlying E and F seams because the base of the E coal seam is above the current water level in the No. 5 Mine well. The water level in the No. 5 well stabilized in 1999 through 2000. Monitoring of the well was suspended in 2001 through 2003 as part of the temporary cessation monitoring plan. Historical field conductivity data for the Trout Creek Sandstone wells indicate no adverse water quality impacts related to mining. Middle Sandstone -Outlying Wells The most significant hydrologic impact caused by Mines 5 and 6 may be an approximate 60-foot drawdown of ground water in the Middle Sandstone as observed in well TR-4. This drawdown persisted as recently as 2001 when monitoring of the well was suspended as part of the temporary cessation monitoring plan. This drawdown was not predicted in the PHC of the permit, but is compazable to the worst-case drawdown projected for the overlying Twentymile Sandstone at a one-mile radius. The water level in the Middle Sandstone well farthest from the mine workings, 83-03, dropped 50 ft. from 1985 to 1997 and then began a gradual recovery that continued as recently as 2001 when monitoring was suspended under the temporary cessation monitoring plan. Water quality had shown no impact from mining. The trends in water levels and the stable water quality indicate mining has not adversely impacted the Middle Sandstone aquifer outside the permit boundary. 23