Laserfiche WebLink
PONDS <br />There were no discharges from the sediment ponds in 1998. <br />HYDROLOGIC IMPACTS <br />No significant unpredicted adverse impacts were detected during 1998. The continued <br />drawdown in the Middle Sandstone unit is determined to be the most significant impact <br />related to mining operations associated with Mines 5 and 6. Drawdown effects in the <br />Twentymile Sandstone unit were evident in the 1998 data as well. The Probable <br />Hydrologic Consequences section of the Permit predicted drawdown in the Middle <br />Sandstone unit associated with mining the F and E coal seams at Mines 5 and 6, <br />although the extent and magnitude of the drawdown were not quantified. A worst case <br />evaluation was, however, prepared for the overlying Twentymile Sandstone. The <br />drawdown in Middle Sandstone Well TRH attributable to the longwall mining in the E <br />and F seams at a distance of approximately one mile has historically been determined <br />to be between 50 and 60 feet. This is comparable to the 60 foot drawdowns projected <br />in the PHC for the overlying Twentymile Sandstone at a distance of one mile from the <br />location of mine subsidence. The impacts observed in the Middle Sandstone are <br />comparable to the worst case projections developed for the Twentymile Sandstone. A <br />small increase in the dissolved solids in Williams Fork Alluvium Well AVF-3 appears to <br />be fluctuating around 2100 mg/L. The cause of this recent relative increase is <br />unknown; however, the data indicates that it is not from the mine discharge or from the <br />waste water lagoon. In addition, these levels are consistent with measurements <br />recorded earlier in the well's data set. The increased TDS in the 7 North Angle <br />• Discharge seen in 1991 has decreased to approximately 850 mg/L. The increase in <br />c-e,-an ,ssea,R Page 12 <br />