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June 25, 2010 3 of 15 <br />600 <br />500 <br />400 <br />y <br />'S <br />300 <br />00 <br />v <br />200 <br />Y! <br />100 <br />10.00 <br />9.50 <br />9.00 <br />8.50 <br />8.00 a <br />7.50 <br />7.00 <br />6.50 <br />0 6.00 <br />9000 8000 7000 6000 5000 4000 3000 2000 1000 0 <br />DistanCe ft) <br />Figure 1. Electrical Conductivity and pH Profile of Ralston Creek, November 13, 2008 <br />Subsequent water quality monitoring and gamma surveys conducted in and along Ralston Creek near the <br />Schwartz Trend crossing in 2009 indicated no evidence of chemical loading from the mine pool via the <br />Schwartz Trend. The sampling was conducted during low flow (base flow) conditions in early December, <br />2009. The results showed no detectable changes in molybdenum and radium 226 concentrations across the <br />trend (Table 2, Figure 2). Uranium concentrations decreased downstream across the trend. These results <br />indicate that the mine pool was not contributing loading to Ralston Creek at this location. DRMS (May 19, <br />2010) states that "further analysis is required to more thoroughly assess any connection between the mine <br />pool [and Ralston Creek] ...along the Schwartz Trend" and that "a lack of geochemical evidence for a <br />connection at present should not be taken as irrefutable evidence that a connection does not or will not exist <br />in the future under conditions of hydraulic equilibrium." Cotter recognizes that the mine pool may not be <br />at hydraulic equilibrium, and in fact, "equilibrium" may include normal seasonal fluctuations in water <br />levels in the mine pool. However, it is speculation to assume that water in the mine pool will migrate to <br />Ralston Creek along the Schwartz Trend based only on the difference in elevation. <br />The hydrogeologic conceptual model developed by Cotter's consultants is based on available <br />hydrogeologic data and does not indicate that groundwater will migrate from the mine pool to Ralston <br />Creek via the Schwartz Trend. A cone of depression still exists around the mine pool, relative to the pre- <br />mining water table (or potentiometric surface). Prior to mine dewatering beginning in the 1950's, the water <br />table was within about 100 feet of ground surface beneath the entire hillside'. During dewatering, the water <br />level near the mine was drawn down to 2,200 feet below the Steve Level. However, because the <br />Upstream Downstream <br /> T T?' <br /> <br /> EE <br />m <br /> Ty? T <br /> 3a N <br /> <br /> <br /> <br /> <br />-Electri..Monductivity -pH <br />Although groundwater occurred within 100 feet of ground surface, mine dewatering was not necessary until the shaft was <br />advanced to 250 feet below ground surface (Soule, 1960) due t6 the low permeability of the rocks. Small quantities of <br />groundwater can be managed without pumping, including the fraction that is evaporated by a mine ventilation system.