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show that the 1996 value was an outlier. This sulfate concentration must be in error <br />because it is greater than the increase in TDS concentration. Sulfate concentrations in the <br />Flume Gulch wells have fluctuated from approximately 400 to 1100 mg/l. <br />3.3 pH <br />Field pH is an important parameter to monitor because some coaf spoils have the <br />potential to increase acidity of the ground water which increases the mobility of most heavy <br />metals. A pH of less than 5 would generally be needed to greatly increase the mobility of <br />most heavy metals. <br />Available pH data is tabulated in Table B-1 of Appendix 8. the pH of water from <br />well GB-2 was near 7 in 1997. The pH value from well GB-5 was high in 1997. A pumped <br />sample is needed from this well to obtain a representative pH of the aquifer water. • <br />The field pH of water from the GC wells have generally been near 7.0 and are <br />within expected limits for 1997. <br />Well GD-1 (2) had a similar pH in 1997 to previous data. Field pH from well GD-2 <br />does not demonstrate a trend. The upgradient mining in the QR seams has not significantly <br />affected the pH in this area of the aquifer. The pH values from backfill well GD-3 are near <br />neutral for 1997, which is near the values in the native aquifer at well GD-2. The QR <br />aquifer at GE-1 has values above neutral for 1997. The pH of water from well GE-2 has <br />been similar in 1997 to values observed during previous years for this well. The pH values <br />for well GE-3 showed variations from 7 to 8.1 in 1997. <br /> <br />3-8 <br />