Laserfiche WebLink
• those in downgradient well GF-4. A very 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 backfill well GF-7 <br /> significantly decreased during the period of 1995 through 1997 and gradually declined in <br /> 1999 after an increase in 1998. The water levels for the last few years have been fairly <br /> similar in well GF-7, indicating that these changes are not due to new backfill being <br /> saturated. Sulfate concentrations in well GMP-1 have been gradually increasing with time, <br /> with a few much higher values every year or so. The water level in well GMP-1 has been <br /> steadily increasing for seven years, which is likely due to increase in water levels in the <br /> backfill aquifer to the south of this well. The increase in sulfates may be due to new <br /> • saturation of backfill material. The sulfate concentrations in wells GP-3 and GP-7 show <br /> some variation but do not show a significant trend over several years. Sulfate <br /> concentrations in eastern HI aquifer well GC-1 have been similar to the higher values in <br /> well GMP-1 and are natural. Therefore, a sulfate concentration of at least greater than 600 <br /> mg/I is needed to 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 but the <br /> 1998 and 1999 values are similar to the historical values. Mining has not significantly <br /> affected the sulfate concentrations in the 3rd White Sandstone near well GB-2. The sulfate <br /> concentrations in well 81-03A are similar to sulfate concentrations in other 3rd White <br /> Sandstone wells. The last four years of well P-8 sulfate values have significantly increased. <br /> • The magnitude and timing of the sulfate concentrations in well P-8 indicate that this <br /> 3-7 <br />