Laserfiche WebLink
The drawdown in Middle Sandstone Well TR-4 attributable to the longwall mining in the E and F seams at <br />• a distance of approximately one mile is determined to be between 50 and 60 feet. This is comparable to <br />the 60 foot drawdowns projected in the PHC for the overlying Twentymile Sandstone at a distance of one <br />mile from the location of mine subsidence. No measurable drawdown has been observed in the Twentymile <br />Sandstone. The impacts observed in the Middle Sandstone are comparable to the worst case projections <br />developed for the Twentymile Sandstone. <br />A continued Increase in the dissolved solids In Williams Fork Alluvium Well AVF~ was observed. The cause <br />of this increase Is unknown; however, the data indicates that it is not from the mine discharge or from the <br />waste water lagoon. <br />The TDS in the 7 North Angle discharge increased in 1991 averaging about 1280 mg/1. This increase in <br />TDS was due to the accumulation of water in the North Angle Sump location which was able to equilibrate <br />with oxidized rock within old workings and rubbelized rock within subsidence panels. The maximum <br />• concentrations of 1474 mg/1 represents this equilibrium concentration. Concentrations appear to decrease <br />when the pump has been running. <br />Flow from the #1 Strip Pit spring discharge was within the range observed during 1982 through 1986. Flow <br />from this spring is influenced by both snowmelt and ditch seepage associated with the 7 North Angle <br />discharge. The increase in TDS and field conductivity appearing in about June, 1991 is apparently related <br />to the higher TDS In the re-issue of the 7 North Angle discharge in May of 1991. <br />• 11 <br />