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Sulfate concentrations for the HI aquifer wells are presented in Figures B-11 and B-12. The <br />sulfate concentrations in the HI aquifer wells in Figure B-11 are fairly similar except for the values <br />in backfill well GF -7, which are substantially greater than those in downgradient well GF -4. Steady <br />sulfate concentrations have been observed in well GF -4 after a very gradual increase for several <br />years. These small variations are well within the natural variation of sulfate concentrations in the HI <br />aquifer but could be defining the very small effects of the backfill aquifer upgradient. Sulfate <br />concentrations in backfill well GF -7 overall gradually declined in 2010 through 2014 and gradually <br />increased in 2015. The water levels for the last few years have been fairly similar in well GF -7, <br />indicating that these changes are not due to new backfill being saturated but likely due to variations <br />in recharge. Sulfate concentrations have stayed low and steady in backfill well GF -5 in 2015. These <br />small changes may be defining the very small effects of upgradient mining but the changes are well <br />within natural ranges. This monitoring indicates that if the HI aquifer has been affected in these <br />wells by upgradient mining, it has been very small. <br />Sulfate concentrations in well GMP -1, which are shown on Figure B-12, have been highly <br />variable indicating an increasing trend during 2006 and 2007 and an overall similar increasing trend <br />in 2008 through 2015. The water level in well GMP -1 had been steadily increasing for several years <br />prior to becoming fairly steady in 2002 and then gradually increasing for several years prior to being <br />steady the last four years. Sulfate concentrations may stay higher and variable in this well for <br />several years. Sulfate concentrations in this well should be influenced by the sulfate concentrations <br />in the backfill aquifer upgradient of GMP -1. The sulfate concentrations in well GP -3 had shown a <br />gradual increasing trend but concentrations have been steady the last thirteen years. Overall steady <br />sulfate concentrations have been observed in well GP -7. Sulfate concentrations in eastern HI aquifer <br />well GC -1 have been similar to the previous higher values in well GMP -1 and had to be natural until <br />Trapper Mining Company 3-6 <br />2015 Annual Report <br />