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fluctuations in the backfill aquifer may be larger than the native QR aquifer. Future monitoring of <br />this well will define whether sulfate concentrations will increase in the backfill aquifer when water <br />levels rise to a higher level in the backfill material. Concentrations in well GD -2 had overall <br />gradually increased the last few years but declined in 2006 and 2007 prior to an overall larger <br />increase in 2008 through 2015. The recent sulfate concentrations in well GD -2 indicate the QR <br />aquifer near well GD -2 may have started to be affected by the upgradient backfill aquifer water <br />quality. <br />Figure B-9 also presents sulfate concentrations for additional QR wells. This figure shows <br />that sulfate concentrations in backfill well GF -11, which is upgradient of QR well GF -6, were <br />decreasing in 2006 and 2007, and overall steady in 2008 through 2015 showing a decline from the <br />historic peak in 2001. Future monitoring is needed to define the maximum sulfate concentration in <br />this backfill aquifer which may have been defined in 2001 and 2002. The sulfate concentrations <br />gradually increased in well GF -6, downgradient of well GF -11. Sulfate concentrations for the last <br />few years had also overall gradually increased in QR well GP -5 until becoming fairly steady the last <br />few years. The sulfate in well GLEV-1 is very small. <br />Figure B-10 presents the sulfate concentrations for KLM aquifer wells GP -2, GP -4 and GP - <br />8. Sulfate concentrations in eastern well GP -2 have varied significantly but were similar in 2012 and <br />2015 to historic values. These changes are within the natural historic range defined at this well prior <br />to mining in this area. Overall steady sulfate concentrations in well GP -4 have existed the last few <br />years with the 2007, 2008 and 2015 concentrations at lower levels and the 2009 through 2014 values <br />at a higher concentration. Sulfate concentrations in well GP -8 have stayed steady and small as <br />mining approaches this area. <br />Trapper Mining Company 3-5 <br />2015 Annual Report <br />