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• 4.8.22a. GROUND WATER INFLOW, 1998-2002. <br />DERRINGER PIT <br />The OR seams will be mined in Derringer pit during the 1998-2002 permit term. Average mine <br />inflows to Derringer pit, including the D pit well dewatering, have varied from 21.4 to 50.4 gpm from <br />1992 though 1996. The average of these inflows has been 31.6 gpm. Similar mine drainage rates <br />would be expelled for 1998 through 2002 due to similar hydrologic condtions for the O and R seams <br />in Derringer pit. <br />ASHMORE AND HAWKEN PITS <br />Mine drainage from Ashmore and Hawken pits has varied from 0 to 24.8 gpm from 1992 through <br />1996 for an average of 13.1 gpm over this five year period. Similar mine drainage rates would be <br />expected from 1998 though 2002 for Ashmore pit due to similar hydrologic conditions for this period. <br />DRAWDOWNS <br />Prediction of drawdown, which should occur based on the above estimates, would be several tens of <br />• feet at one mile from the permfl boundary. Observed drawdowns have been less than these <br />predictions. Actual observations of drawdowns are much more indicative of impacts. These low <br />permeability aquifers have exhibRed limited drawdowns in the immediate vicinity of the active pits. <br />Further, drawdowns downgradient of the active mining areas typically recover much faster than <br />expected because the increased permeability in the backfill spoil aquifer transmits water to the <br />downgradient end of the pit more readily. <br />IMPACTS TO ADJUDICATED WELLS (see Map M31) <br />The Second White sandstone does not exist in Derringer pit. In Ashmore pit, the Second White <br />Sandstone is probably not saturated in the areas of the pit that will be minetl from 1998 to 2000. <br />The nearest Third White sandstone well to the Ashmore pit during the permfl period is slightly greater <br />than one mile to the northeast. Significant drawdowns in the Third While sandstone to the north of <br />the mine are not expelled because drainage of ground water to the north end of the mine due to <br />increased penneabildy in the backfill aquifer will likely cause water-level rises in the Third White <br />sandstone aquifer north of the mine. No impacts are expected in Third White sandstone wells 80998 <br />r 1 <br />U <br />4-226c <br />A9AY 1 3 1998 <br />