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' • <br />Drawdown <br />The dewatering of the undisturbed overburden aquifer during development of <br />the underground mine will cause an incremental decline of piezometric water <br />levels in the area immediately adjacent to the mine. The drawdown of water <br />levels in the overburden aquifer will be measured in the monitor wells <br />surrounding the underground mine. No lowering of water levels in private <br />wells is predicted. The private wells shown on the Foidel Creek Mine Baseline <br />Hydrology Map (Map 9a) are too distant to be affected by mine dewatering. <br />The GRWATER was used to predict drawdown levels resulting from the <br />dewatering of the overburden aquifer. The analysis was incremented in time <br />steps of 360 days, with a mining advance rate of 13.5 feet per day, and utilized <br />the same aquifer parameters and assumptions mentioned earlier. A plot of the <br />water level decline is shown on Figure llb, Predicted Drawdown Map After <br />Five Years of Mining. <br />Values of maximum drawdown, calculated for distances of 10, 500, 1000, and <br />10,000 feet from the underground mine, are 900 feet, S00 feet, 400 feet and <br />100 feet, respectively. The water level decline will be measureable by the <br />monitor wells adjacent to the proposed underground mine. Water level decline <br />is not expected to be measureable more than 16,000 feet away from the <br />underground mine. The zone of influence was found not to extend to the <br />discharge area where the overburden aquifer is tributary to Fish Creek, at the <br />eastern edge of the groundwater basin. It was not necessary to account for a <br />constant head boundary at Fish Creek in the inflow calculations. Since no. <br />drawdown will occur beneath Fish Creek at a location where there is a <br />hydraulic connection between the aquifer and the stream system, there will be <br />no depletion of water from Fish Creek or the alluvium associated with the <br />stream. As stated previously, there is no hydraulic connection between the <br />confined overburden aquifer and Foidel Creek. Therfore, all of the water <br />which will be encountered during mining will be derived from aquifer storage. <br />2.05-49c <br />