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State Req. <br />the mine area on the historic average flow and quality of the <br />receiving streams and associated alluvial ground water system <br />can be estimated. Upon recommendation from the CMLRU, file <br />period of the year during which this analysis is directed is <br />the growing season, from June through September, when the <br />streams are or could be utilized for irrigation. With respect <br />to flow, this period of the year reflects the June recession of <br />the spring runoff hydrograph and the transition during July, <br />August and September to base flow conditions when overland, <br />surface water flow is minimal and subsurface, ground water flow <br />is maximal. With respect to TDS concentrations in surface <br />water fo'r this period of the year, June data reflect relatively <br />low, concentrations when flow is relatively high, while July <br />through August data reflect the transition from relatively low <br />to relatively high TDS concentrations when base flow (low flow) <br />conditions characterize the stream flow regime. <br />• <br /> <br />1. Surface Water <br />a. Quantity <br />Pre and postmining surface water flow at the Seneca II Mine was <br />determined in 1980 using HYMO (Williams and Haan, 1973). Tlie <br />results of this analysis indicated that postmine discliaryes <br />will not vary significantly from premine discharges. <br />As stated in Section III, changing the ground water system from <br />a structurally-controlled artesian aquifer to a topographically <br />-controlled unconfined system increases the amount of ground <br />water available for discharge into the surface water system. <br />Water infiltrates through the spoil to the impermeable shale <br />7-174 Revised 10/30/87 <br />