2023-04-19_PERMIT FILE - C1981010 (103)

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I AND J PITS Initial boxcuts running west to east will be opened just north of the croplines for the F and G seams in I and J Pits, respectively. Pit water is expected to be encountered during the initial period of opening each pit. Once the initial sections of the boxcuts are opened, pit dewatering should be minimal while continuing highwall mining operations on the pit floor. The pit will be backfilled with material removed from the advancement of the pit and placed behind the highwall miner as it advances in sections along the highwall. The capture of surface runoff will be minimal as the pit progresses. Due to the nature of the permeability of the spoils materials and the location of the pits near the croplines of the 1st, 2nd and 3rd White sandstones, water drawdown should be minimal in both pits during and after mining operations in the area. During active mining, localized drawdowns in the 2 nd and 3rd White sandstones may be large near the HWM entries due to the good connection with the F and G coal seams and may also be significant in the 1st White sandstone. COLT PIT An initial boxcut running west to east will be opened in order to access the L and Q seams. Pit water is expected during the initial period of opening the pit. The need for pit dewatering should decline substantially as highwall mining operations get underway. Drawdowns are not expected to be any more substantial than the minimal drawdowns experienced with historic Colt Pit mining. DRAWDOWNS Prediction of drawdown, which should occur based on the above estimates, would be several tens of feet near the down dip edge of HWM but should not extend out to one mile from the permit boundary due to the small transmissivities of these aquifers. Observed drawdowns have been less than these predictions. Actual observations of drawdowns are much more indicative of impacts. These low permeability aquifers have exhibited limited drawdowns in the immediate vicinity of the active pits. Further, drawdowns downgradient of the active mining areas typically recover much faster than expected because the increased permeability in the HWM area will readily transmit water to the downgradient end of the HWM entries. Drawdowns at KLM well GP-2, roughly 2200 feet distant from the G Strike pit boxcut, had developed on the order of twenty feet, well within the approximate range of predicted behavior for aquifers in the area, however, water levels had risen to pre-mine maximums by 2001. They have slowly declined since, perhaps in response to drought or mining in the K Pit area, but not as low as the period when the G Strike pit area was mined. Drawdown recorded at QR well GP-1, some 1200 feet away from the boxcut, was observed at approximately 40 feet before GP-1 was disturbed by mining in early 2003. Wells GC-1 and GC-2, completed in the HI and 3rd White Sandstone aquifers respectively, showed slight declines in water level when A Pit mining occurred within 1,000 feet directly upgradient from the wells during the early 2000’s. Water levels in these wells have since recovered to premining levels. 4-226e