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• In the event that the aquifer discharges into the mine either through existing joint planes or through fractures caused by disturbance of the shale partition during mining, water quantity at the updip mine shaft well ie very likely to be impacted. It is worth noting that the past underground mines in the area are known to have been wet. Potential aquifers overlying the Brookside coal such ae the perched aquifer(s) feeding springs TP-52 and TP-S3 may be impacted ae a result of the proposed underground workings in Twln Pines No. 2 if subsidence was to take place. It ie expected that the sandstone units at various horizons are jointed while the dominant and thicker unite of shale are not. Subsidence could extend the jointing in the sandstones through the shale beds. However, subsidence does not appear to be a problem over areas of past underground mines in the vicinity of Twin Pines No. 2 and thus overlying aquifers are not expected to be impacted. • 2.2 Quality Possible impact to the water quality of the unconfined aquifer in Oak Creek alluvium from surface diehcargee along Lewis Gulch is discussed in 2. 05.6(b)(iv.). The ground-water system in the project area is not interconnected to the unconfined alluvial aquifer. No impact ie expected on the water quality of this aquifer from the proposed underground mining. The eater quality of the Caldirola Mine No. 2 shaft yell (tables 2.04.7(1)-6 and -7 is perhaps the best indication of eater quality impact to be expected from the proposed mining at Twin Pines No. 2. The only area of concern ie the increase in TDS which is already above EPA standards (table 2.04.7(1)-3). The eater quality of the water from the mine shaft well at Caldirola Mine No. 2 would not be impacted as this lies up dip from the proposed Twin Pines No. 2 underground workings. n U JFSA-68