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SAR values above 20 were reported in both cases (see pages 67a-69 of Volume 10, and Table 2.04.9 ll) ib) -4. The applicant covered all underground development waste material with 4 feet on non-toxic cover and topsoil. Analyses of D seam roof and floor material contained in Volume 10 did not indicate acid-forming, sodic, or otherwise inhibitory strata. Pre-law surface mining activity in and adjacent to the surface facilities area at Red Canyon resulted in a mixing of geologic material, with piles of overburden left adjacent to small mining and exploration pits. The operator filled in the abandoned strip pits with underground development waste, and covered portions of the waste with material from the abandoned overburden piles. b. Groundwater For information regarding the groundwater system at the Red Canyon Mine, refer to the Description of the Environment, Hydrologic Balance section, previously discussed in this document. c. Surface Water For information regarding the surface water system at the Red Canyon Mine, refer to the Description of the Environment, Hydrologic Balance section, previously discussed in this document. Probable Hydrologic Consequences a. Groundwater Effects and Mitigation Potential impacts to the groundwater regime have been identified. During the active mining phase, mine pumping could cause drawdowns in the coal aquifers, extending several miles from the mine. Now that the mine is sealed, three other impacts are likely to occur. Water in the flooded workings is likely to acquire a greater salinity and a more sodic character. This water may ultimately discharge to the glacial-alluvial aquifer at the coal subcrops and result in a degradation in water quality. Lastly, a spoil aquifer will develop in the underground waste disposal area and the backfilled areas of the reclaimed topography. Total projected inflows to each of the two Red Canyon Mines will average about 25 gpm. Actual inflows in the "E" Mine averaged 25 gpm in 1983 and 1984. Distances downdip from the mine from which drawdowns will be noticeable are predicted to be 11.5 and 3.9 miles for the D and E seams, respectively. The results of the modeling suggest that the drawdown will not extend out to the glacial/alluvial aquifer through unfractured coals to the coal subcrops. Distances updip from mine workings from which drawdowns will be noticeable are predicted to be 44.6 feet and 5.8 feet for the D and E seams, respectively. A buffer zone of 200 feet will be maintained between mine workings and the subcrops. However, fractured coals could allow ground water movement from the glacial/alluvial aquifer to the mine workings. The implications of these effects to water users in the area are considered to be insignificant. No wells in the area to be affected by the drawdowns are completed solely in the D or E coal seams. in addition, the dip of the strata beneath the 15