Laserfiche WebLink
predicted drawdown in the Middle Sandstone unit associated <br />• with mining the F and E coal seams at Mines 5 and 6, although <br />the extent and magnitude of the drawdown were not quantified. <br />A worst case evaluation was, however, prepared for the <br />overlying Twentymile Sandstone. The drawdown in Middle <br />Sandstone Well TR-4 attributable to the longwall mining in the <br />E and F seams at a distance of approximately one mile is <br />determined to be between 50 and 60 feet. This is comparable to <br />the 60 foot drawdowns projected in the PHC for the overlying <br />Twentymile Sandstone at a distance of one mile from the <br />location of mine subsidence. No measurable drawdown has been <br />observed in the Twentymile Sandstone. The impacts observed in <br />the Middle Sandstone are comparable to the worst case <br />projections developed for the Twentymile Sandstone. An <br />• increase in the dissolved solids in Williams Fork Alluvium <br />Well AVF-3 appears to have leveled off. The cause of this <br />increase is unknown; however, the data indicates that it is <br />not from the mine discharge or from the waste water lagoon. <br />The increased TDS in the 7 North Angle Discharge seen in 1991 <br />remained approximately the same in 1992, averaging about 1290 <br />mg/1. This increase in TDS was due to the accumulation of <br />water in the North Angle Sump location which was able to <br />equilibrate with oxidized rock within old workings and <br />rubbelized rock within subsidence panels. The maximum <br />concentrations of 1474 mq/1 represents this equilibrium <br />concentration. Concentrations decreased in 1993 when the pump <br />has been running. Flow from the fl Strip Pit spring discharge <br />~Z <br />