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in 2008 through early 2013. A decline - in sulfate- was observed in the last part of 2013: The recent <br />sulfate concentrations in well GD -2 indicate the QR aquifer near well GD -2 may have started to be <br />affected -by the upgradient- backfill aquifer water quality. <br />Figure B-9 also presents sulfate - concentrations for additional -QR wells. This figure shows <br />that sulfate concentrations in- backfill well- GF4 1, which - is upgradient of QR well GF -6, were <br />decreasing in 2006 -and 2007, -and overall steady -in 2008 through 2013 showing a decline from the <br />historic peak in 2001. Future monitoring is needed to define the maximum sulfate concentration in <br />this back -fill- 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. <br />Figure B -10 presents the sulfate concentrations for KLNf aquifer wells GPI-2, GP=4 and GB-8. <br />Sulfate_ concentrations in eastem well GP -2 have varied significantly but were similar in 2012 and <br />2013 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 and 2008 concentrations at lower levels and the 2009 through 2013 values at a <br />higher concentration. Sulfate concentrations in well GP -8 have stayed steady and small as mining <br />approaches this area. <br />Sulfate- concentrations for the HI aquifer wells are presented-in -Figures B -11 and B -12. The <br />sulfate concentration in the HI aquifer wells in Figure B -11 are fairly similar except for the values in <br />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 />Trapper Mining Company 3 -5 <br />2013 Annual Report <br />