Laserfiche WebLink
• those in downgradient well GF-4. A very gradual increase in sulfate concentration in <br /> downgradient well GF-4 had 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 backfill well GF-7 <br /> significantly decreased during the period of 1995 through 1997 but increased in 1998. The <br /> water level in 1998 was fairly similar to the previous few years level in well GF-7, indicating <br /> that the increase was not due to new backfill being saturated. Sulfate concentrations in <br /> well GMP-1 have been gradually increasing with time, with a few much higher values every <br /> year or so, including the two 1998 values. The water level in well GMP-1 has been steadily <br /> increasing for seven years, which is likely due to increase in water levels in the bacldhll <br /> aquifer to the south of this well. The increase in sulfates may be due to new saturation of <br /> • back ill material. The sulfate concentrations in wells GP-3 and GP-7 show some variation <br /> over the last few years but do not show a significant trend. Sulfate concentrations in <br /> eastern HI aquifer well GC-1 have been similar to the higher values in well GMP-1 and are <br /> natural. Therefore, a sulfate concentration of at least greater than 600 mg/I is needed to <br /> be confident that the increases are due to the mining operation. <br /> Figure B-16 presents the sulfate concentrations for five 3rd White Sandstone wells. <br /> A gradual declining trend in 3rd White Sandstone well GB-2 had been occurring over the <br /> last few years but the 1998 value indicates an increasing trend. The sulfate concentrations <br /> in well 81-03A are similar to sulfate concentrations in other 3rd White Sandstone wells. <br /> The last three years of well P-8 sulfate values have significantly increased. The magnitude <br /> and timing of the sulfate concentrations in well P-8 indicate that this increase is due to <br /> mining. Figure B-17 presents the sulfate concentrations for wells GE-3, GLUX-1 and P-5. <br /> 3-7 <br />