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RAG, Empire Corporation 2000 AHR .• HYDROLOGIC IMPACTS No significant unpredicted adverse impacts were detected during 2000. The continued drawdown in the Middle Sandstone unit is determined to be the most significant impact related to mining operations associated with Mines 5 and 6. Drawdov`m effects in the Twentymile Sandstone unit were evident in the 2000 data as well. The Probable Hydrologic Consequences section of the Permit predicted drawdown in the Middle Sandstone unit associated with mining the F and E coal seams at Mines 5 and 6, although the extent and magnitude of the drawdown were not quantified. A worst-case evaluation was, however, prepared for the overlying Twentymile Sandstone. The drawdowrl in Middle Sandstone Well TR-4 attributable to the longwall mining in the E and F seams at a distance of approximately one mile has historically been determined to be between 50 and 60 fee[. This is comparable to the 60-foot drawdowns projected in the PHC for the overlying Twentymile Sandstone at a distance of one mile from the location of mine subsidence. The impacts observed in the Middle Sandstone are comparable to the worst case projectiuus developed for the Twengmiile Sandstone. The increased TDS in the 7 North Angle Discharge seen in 1991 has decreased to approximately 1150 mg/L. The increase in TDS was due to the accumulation of water in the North Angle Sump location that was able to equilibrate with oxidized rock within old workings and rubbleized rock within subsidence panels. The maximum concentrations of 1474 mg/I probably represent this equilibrium concentration. Flow from the #] Strip Pit spring discharge was within the range observed during ] 982 through 1986. Flow from this spring is influenced by both snowmelt and ditch seepage associated with the 7 North Angle discharge. Flows from the 5 mine workings were somewhat lower than previous years. • I:\Environmenlal\E~1PIRE\AFIR\2000\Tezl\Empve2000AHR.doc Page 8