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concentrations in the late 1980's. Sulfate concentrations have been fairly stable in the last • <br /> flew years after a gradual rising trend for several years. Figure 8-12 also presents sulfate <br /> concentrations for QR wells. This figure shows that sulfate concentrations in backfill well <br /> GF-11, which is upgradient of QR well GF-6, increased after the large decline in 1996. The <br /> 1998 value is above the earlier peak values, showing increased sulfate concentration as the <br /> water level rises to a new high and the field pH slightly declines in this backfill aquifer. The <br /> sulfate concentrations have been fairly steady in the last three years in well GF-6, <br /> downgradient of well GF-11. Sulfate concentrations for the last several years have also <br /> been relatively steady in QR wells GP-5 and GP-6. As expected, the sulfate concentrations <br /> are greater in downgradient well GP-5. The 1997 and 1998 values show that the <br /> significant increase in sulfate concentration that occurred in eastern QR well GP-1 in 1996 <br /> was an outlier. • <br /> Figure B-13 presents the sulfate concentrations for KLM aquifer wells GF-3, GP-2, <br /> GP-4 and GP-8. A gradually dedining trend in sulfate concentrations for the last few years <br /> had occurred in well GF-3 with the 1998 values showing a small increase. Sulfate <br /> concentrations in eastern wells GP-2 and GP-8 vary significantly but should be natural due <br /> to their location in the eastern portion of the Trapper permit area. An overall increasing <br /> trend is being observed in well GP-2 over the last several years. A significant decline in <br /> sulfate concentration had occurred in 1995 and 1996 in well GP-4 with the last two years <br /> showing a gradual increase. <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 <br /> similar except for the values in backfill well GF-7, which are substantially greater than • <br /> 3-6 <br />