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issued a permit for the Mine in 1979. AR:00423. The Mine ceased operation in May 2000. <br />AR:00337; 00423. <br />During operations, the Mine was kept dry by pumping water from the lower levels of the <br />Mine to the surface, where the water was treated in a water treatment plant and discharged to <br />Ralston Creek under a Colorado discharge permit. AR:00032. Groundwater inflow rates into <br />the Mine were low, indicating that the bedrock had low permeability, and there were no high <br />permeability faults or conduits that could convey water to (or from) the underground workings.] <br />AR:00272; 00043; 00942:21-24; 00514. Ralston Creek was never drained during mining, <br />despite the Mine's being excavated to nearly 2,200 feet below the creek level.2 AR:00272. The <br />bedrock which surrounds the Mine has low permeability, based on testing, records, and historical <br />information. The low permeability inhibits migration of mine pool water from the Mine. <br />AR:00272; 00940:19-00941:11; 00512. <br />During mining, the water treatment plant also treated water from four sumps in the <br />alluvial fill. AR:00032; see AR:00036 for a diagram of the historic sumps. <br />Dewatering pumps were shut off in 2000, treatment of dewatering effluent ceased, and <br />the water treatment plant was shut down in June 2002 in accordance with the Colorado discharge <br />permit issued by the Water Quality Control Division ("WQCD") of the Colorado Department of <br />Public Health and Environment ("CDPHE"), and a letter from CDPHE. AR:00337; 00424; <br />' At its total maximum depth of 2,200 feet when the Mine was fully dewatered, the <br />average inflow to the Mine was only 189 to 190 gallons per minute ("gpm"). AR:00272; <br />00941:23-00942:20; 00515. <br />2 If a strong hydraulic connection existed between the Mine and Ralston Creek, the <br />Ralston Creek flow would have dried up as a result of mine dewatering during operations. <br />AR:00272; 00943:2-11. Instead, no effect on the creek was discernible. AR:00272.