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Surface Water Three probable impacts to the surface water regime have been identified by the applicant. During the active mining phase mine dewatering may have lessened the volume of water discharging to the streams from the alluvium and could potentially have caused a gradient reversal. The discharge of mine inflow water would change the location of groundwater discharge to the surface water system and result in a degradation of water quality. Following sealing of the mine, and the re-establishment of the coal aquifer, discharge of the mine water to the glacial-alluvial aquifer could result in a diminution of water quality of the adjacent streams. Some depletion of the stream/alluvial aquifer system could occur through the coal seams themselves which subcrop beneath the Williams Creek and Ward Creek valleys. Ground water movement in the permit area discharges to the stream/alluvial aquifer system. Mining will dewater adjacent portions of the coal seam aquifer and will intercept some of the ground water currently discharging to the stream/alluvial aquifer system. In addition, the presence of the underground workings beneath the valley could reverse the pre-existing ground water flow direction between the valley and the mine workings, and water from the stream/alluvial aquifer system could enter the mine workings through the coal seams. This reversal of ground water flow direction would occur only in areas where the coal seams are fractured. The applicant has provided a prediction of inflow to the mine for the D and E coal seams on a yearly basis. The maximum predicted inflow, 78.67 gpm (0.17 cfs) in 1983, provides an estimate of worst case streamflow depletion. One-third of the measurable mine inflows in the "E" seam mine were found in the area below Ward Creek. Little inflow was observed below Williams Creek. The effect will be temporary, since once the workings become flooded, discharge will once again be to the surficial aquifer via the subcrop. Since some of the ground water inflow comes from other sources, such as depletion of ground water storage, the actual stream flaw depletion would probably be less than predicted. Actual inflow in Mine No. 1 (E-Seam) never exceeded 25 gpm. The applicant's modeling estimates that two years after ground water removal begins, the total volume of water intercepted by the mine would be taken directly from the stream. The addendum reports that the minimum streamflow observed in Ward Creek by the ditch rider was 2.5 cfs in 1977. Therefore, the total mine inflow (and worst case streamflow depletion) represents only 7 percent of the lowest streamflow observed in Ward Creek. The predicted mine inflow is only about 2 percent of the average flow in Ward Creek. During operations, most of the mine water was returned to the Ward Creek drainage system. Mine water was pumped to a sediment pond, where water not lost to evaporation was discharged to the Ward Creek system via Carbon ditch. Mine water had a degraded water quality with an average conductivity of 3.5 mmhos/cm and was expected to affect water quality in Ward Creek. Average total dissolved solids (TDS) levels in Ward Creek increased from 99 mg/1 to 194 mg/1. -11-