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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 <br />by mining, and transfer of drainage flows to the surface water system. <br />This drainage mechanism will reduce the quantity and availability of <br />groundwater resources down-gradient of mine disturbance areas. However, <br />reductions in quantity and availability of down-gradient groundwater due <br />to the Southfield operations are expected to be minor relative to total <br />groundwater flows within the basin, limited in areal extent, and temporary <br />in nature. In addition, reductions in down-gradient flows are not <br />expected to adversely impact groundwater users since primary groundwater <br />use within the basin involves stratigraphic units which are effectively <br />hydrologically isolated from the sequence which may be impacted. <br />• Monitored pumping rates from the Southfield dewatering well average <br />approximately 60 cfm which translates into approximately 70 acre feet per <br />year. With a current underground mine disturbance area of approximately <br />300 acres, the average pumping rate is equivalent to approximately 0.02 <br />cfm per acre of disturbance. Information on groundwater inflows to other <br />underground mines within the groundwater basin indicate an approximate <br />flow rate of 0.13 cfm per acre of disturbance. Comparison of these inflow <br />figures indicates that inflows to the Southfield mine are in the same <br />range as other recorded mine inflows, although significantly lower. <br />In order to assess the significance of probable reductions in down- <br />gradient groundwater flows, evaluation of relative acreages and potential <br />flows provides a reasonable basis for comparison. The ultimate area of <br />underground disturbance at the Southfield Mine will be approximately 1,370 <br />acres. This compares with an overall groundwater basin area of <br />approximately 45.1 square miles or 28,900 acres. Assuming that normal <br />groundwater flows through the strata to be disturbed by mining are <br />• equivalent to the mine inflow rate and average approximately 0.02 cfm per <br />acre, results in calculated mine inflows of 330 acre feet per year. This <br />annual inflow rate can be compared with potential flow rates through the <br />same strata within the groundwater basin of approximately 7,000 acre feet <br />2.05.6-41 <br />