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These probable groundwater hydrologic consequences and their relative <br />significance are discussed in the following sections. <br />Development of underground mine openings and related necessary dewatering <br />activities will result in groundwater drainage from the sequence disturbed by <br />mining, however with transfer of drainage flows to mined-out areas, this drainage <br />mechanism will not reduce the quantity and availability of groundwater resources <br />downgradient of mine disturbance areas. In addition, any temporary effects -on <br />downgradient flows are not expected to be significant or to adversely impact <br />groundwater users since primary groundwater use within the basin involves <br />stratigraphic units which are effectively hydrologically isolated from the sequence <br />which may be impacted. <br />Monitored pumping rates from the Southfield dewatering system averaged <br />approximately 60 cfm which translates into approximately 70 acre-feet per year. <br />With a current underground mine disturbance area of approximately 300 acres, <br />the average pumping rate is equivalent to approximately 0.02 cfm per acre of <br />disturbance. Information on groundwater inflows to other underground mines <br />within the groundwater basin indicate an approximate flow rate of 0.13 cfm per <br />acre of disturbance. Comparison of these inflow figures indicates that inflows to <br />the Southfield mine are in the same range as other recorded mine inflows, <br />although at the low end of the range. <br />In order to assess the significance of mine inflows, evaluation of relative acreages <br />and potential flows provides a reasonable basis for comparison. The ultimate area <br />of underground disturbance at the Southfield Mine will be approximately 1,370 <br />acres. This compares with an overall groundwater basin area of approximately <br />45.1 square miles or 28,900 acres. Assuming that normal groundwater Flows <br />through the strata to be disturbed by mining are equivalent to the mine inflow <br />rate and average approximately 0.02 cfm per acre, results in calculated mine <br />inflows of 330 acre-feet per year. This annual inflow rate can be compared with <br />potential flow rates through the same strata within the groundwater basin of <br />approximately 7,000 acre-feet <br />MR-50 2.05.6-41 Revised -June 2003 <br />