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.~ <br />influences upon calculations of mine groundwater inflow. Perhaps the <br />lease applicable assumptions are that the mine will receive its water <br />from the full saturated thickness of the aquifer and that the aquifer is <br />of infinite horizontal extent. The proposed mine will not fully penetrate <br />the aquifer, and the aquifer's extent is not finite since it is known to <br />crop out approximately 2000 feet south of the proposed mine. <br />• <br />4.1.4 Mine Water Inflow <br />Calculations of inflow to the proposed mine are based upon data from the <br />aquifer test at the G 1 site (at the north end of the pit) conducted in <br />May, 1977. Although this test was conducted fora sufficient length of <br />time to provide reasonable values of transmissivity (T), (the aquifers <br />ability to transmit water) the storage coefficient (S) (the volume of <br />water released across a unit area by a unit decrease in head) is indeter- <br />minate. The pump test was probably not conducted long enough for equilibrium <br />to be established; however, the transmissivity is sufficiently low that <br />to assume stabilization will not introduce appreciable error into the <br />calculations. The effect of gradually opening the mine pit, dewatering, <br />leaving the pit open, progressing from cut to cut, and back-filling will <br />create extremely dynamic groundwater conditions in the pit area. <br />To simplify the arithmetic, the artesian conditions at monitoring well <br />G 1 were taken as the worst possible case for computing inflow and resultant <br />water level declines. <br />~~ <br />Exhibit 26 illustrates the distance/drawdown plots of the aquifer test <br />conducted at the G 1 site. Curves A and B are drawdown versus distance <br />plots. Mining is intended to have as its limit the base of coal seam 5, <br />which corresponds to a depth of about 134 feet at the G 1 site. Water <br />levels would then be drawn down to the 134-foot level at the pit walls. <br />Curve (B) was projected parallel to (A) to estimate the radius of the <br />cone produced from dewatering at the 134-foot level. The radius of <br />influence was thus estimated to be about 420 feet. <br />20 <br />~Y.e .._.. _. -. -~ <br />