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12 also presents sulfate concentrations for QR wells. This figure shows that sulfate • <br />concentrations in backfill well GF-11, which is upgradient of QR well GF-6, increased after <br />the large decline in 1996. The values for the last three years are above the earlier peak <br />values. Future monitoring is needed to define the maximum sulfate concentration in this <br />backfill aquifer. The sulfate concentrations have been steady over the last three years in <br />well GF-6, downgradient of well GF-11. Sulfate concentrations for 2000 have also been <br />steady in QR wells GP-5 and GP-6 after a very gradual increasing trend in well GP-5. A5 <br />expected, the sulfate concentrations are greater in downgradient well GP-5. The sulfate <br />values for eastern QR well GP-1 have remained tow and steady through 2000. <br />Figure 8-13 presents the sulfate concentrations for KLM aquifer wells GF-3, GP-2, <br />GP1} and GP-8. Steady sulfate concentrations for the last few years have existed in well <br />GF-3. Sulfate concentrations in eastern wells GP-2 and GP-8 vary significantly but should • <br />be natural due to their location in the eastern portion of the Trapper permit area. A <br />gradual increase in sulfate concentrations in well GP-4 for the last few years is well within <br />natural variations observed in this aquifer. <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 />those in downgradient well GF-4. Avery gradual increase in sulfate concentration in <br />downgradient well GF-4 has been observed over the last few years. This small increase is <br />well within the natural variation of sulfate concentrations in the HI aquifer but could be due <br />to the effects of the backfill aquifer upgradient. Sulfate concentrations in backfiil well GF-7 <br />significantly decreased during the period of 1995 through 1997 and, overall, have • <br />3-6 <br />