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• <br />Section 7 <br />Groundwater Information <br />perturbations in the regional groundwater gradient. Mine dewatering ceased in June <br />2008; the mines are currently in temporary cessation status. is currently conducted at <br />The most recent phase of mine dewatering at the West Sunday Mine started in early <br />2008. The rate of dewatering is estimated to be 400 gallons per day (approximately 0.3 <br />gallons per minute) (S. Davies, West Sunday Mine Foreman, personnel <br />communication 2008). Prior to the most recent phase of mine dewatering, the water <br />level in the West Sunday mine was approximately 5,438.1 ft. above mean sea level <br />(amsl). Dewatering at a rate of approximately 0.3 gallons per minute for a period <br />extending from early 2008 to the present has resulted in lowering of the water table by <br />approximately 14 feet to the current level of approximately 5,424.2 ft. amsl. <br />Water within the Sunday Mine has not been pumped since approximately 1991 (J. <br />Fisher personal communication 2009). During the period of 1991 to the present, the <br />volume of water that has flowed into the mine is approximately 55.4 million gallons. <br />This equates to an average inflow rate of approximately 5.8 gallons per minute over <br />the past 18 years. The rate of inflow into an underground mine after cessation of <br />pumping is fastest immediately after pumping stops and slows as the mine water <br />table approaches the elevation of the surrounding water table (Wolkersdorfer 2006). It <br />is currently unknown if groundwater is continuing to flow into the Sunday mine. <br />Although water has not been pumped from the Sunday mine since 1991, it is likely <br />that evaporative losses of water from the Sunday mine have continued to occur <br />during intermittent periods of active mining and associated ventilation during the <br />period of 1991 to the present. <br />A small zone of groundwater inflow is also present in the lower portion of the <br />Carnation Mine, and water is not reported in the St. Jude mine. Groundwater is <br />reported to be flowing into the Carnation mine in this area, but the rate of inflow is <br />currently unknown. <br />Observed groundwater elevations in the base of the Topaz mine are approximately <br />140 feet higher than groundwater elevations in the area of the interconnected West <br />Sunday /St. Jude /Carnation /Sunday underground workings. The Topaz mine is not <br />interconnected with the West Sunday /St. Jude /Carnation /Sunday underground <br />workings. Dewatering and ventilation of the Topaz mine has occurred on an <br />intermittent basis since development of the mine. It is currently unknown if <br />groundwater in the area of the Topaz mine is contiguous with groundwater in the <br />area of the interconnected West Sunday /St. Jude /Carnation /Sunday underground <br />workings. It is possible that the 140 ft. difference in the water table is a result of <br />dewatering and consumptive groundwater use resulting from mining in the <br />interconnected West Sunday- Carnation -St. Jude- Sunday mine workings. It is also <br />possible that the water observed in the Topaz mine is associated with a local perched <br />zone of groundwater within the Salt Wash Member. <br />C: \Documents al Settings \ cwoodward.DMC\Desktop \Environmental Protection Plan Sundav Mines Revised November 2011 revl (2) 11 10 11.docx <br />7 -7 <br />