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<br />Section 780.21 ~c) Continued. <br />drawdown of water levels in the overburden aquifer will be measured <br />in some of the monitor wells surrounding the pit, but no lowering <br />of water levels in private wells is predicted because the private <br />wells shown on the Twentymile Park Hydrology (Map 6) are either <br />completed in other isolated aquifers or they are too distant to be <br />affected by mine dewatering. <br />The maximum decllne of water levels in the overburden aquifer was <br />computed using the equation given 3n Lohman (1972), p. 23: <br />s = 2.30 Q log 2.25 Tt <br />41r T(7.48) r2S <br />where: s = drawdown at radius = r and time = t, in <br />feet. <br />r"y- <br />Q = maximum calculated discharge from the pit, <br />in gallons per day. <br />T = transmissivity, in gallons per day, per <br />foot. <br />t = time of maximum calculated discharge, in <br />days since discharge began. <br />r = radius away from the pit, in feet. <br />S = storage coefficient, unitless. <br />Values of maximum drawdown were calculated for distances of 500, <br />1,000, 2,000 and 4,000 feet from the boxcut and plotted on the <br />Twentymile Park Cumulative Hydrologic Effects (Map 53). An oval- <br />shaped zone of water level depression is shown which will be <br /> <br />measurable by the Energy Fue]s monitor wells down-gradient (to the <br />north) from the area to be mined in Eckman Park. Water level <br />decline is not expected to be measurable more than 5,000 feet away <br />from the boxcut areas. There are limitations on these predictions. <br />The contours of drawdown shown do not take into account the gradient <br />of the pie2ometric surface, the effect of faulting, and preferred <br />direction of ground water flow in the overburden aquifer. In <br />780-180 <br />