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three years in well GE-1 after a peak near 400 mg/I but increased in 2003. Figure 8-12 also <br />preserts sulfate concentrations for QR wells. This figure shows that sulfate concentrations <br />in backfill well GFil, which is upgredient of QR well GF-6, had been fairly steady the last <br />two years after an increasing trend since 1996 but declined in 2003. Future monitoring is <br />needed to define the ma~mum sulfate concentration in this badfill aquifer which may have <br />been defined in 2001 and 2002. The sulfate concentrations have been steady over the last <br />several years in well GF-6, downgradient of well GFli. Sulfate concentrations for the last <br />few years have gradually increased in QR well GP-5 while steady levels have been observed <br />in well GP-6. As expected, the sulfate wncentrations are greater in downgradient well GP- <br />5. <br />Figure B-13 presents the sulfate concentrations for IaM aquifer wells GF-3, GP-2, <br />GP-4 and GP-8. Avery gradual increase in sulfate wnoyntrations for the last few years had <br />existed in well GF-3 followed by a slight decline in 2003. Sulfate concentrations in eastern • <br />well GP-2 have varied significantly but recent values are gradually increased but within the <br />natural historic range defined at this well prior to mining in this area. A gradual overall <br />increase in sulfate concentrations in well GPI has been observed but is within natural <br />variations observed in this aquifer. Sulfate concentrations in well GP-8 have stayed steady <br />as mining approaches this area. <br />Sulfate concentrations for the HI aquifer wells are presented in Figures B-14 and B- <br />15. The sulfate concentration in wells in the HI aquifer wells in Figure B-14 are fairly similar <br />except for the values in backfill well GF-7, which are substantially greater than those in <br />downgradient well GF-4. Steady sulfate concentrations had been observed in well GF4 <br />after a very gradual increase the previous few years. The 2003 data indicates a gradual . <br />3-6 <br />