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increase is due to mining. The 1999 value indicates that this increase may have peaked. • <br /> Figure B-17 presents the sulfate concentrations for wells GE-3, GLUX-1 and P-5. The <br /> sulfate concentrations for both GE-3 and GLUX-1 have remained low, while the sulfate <br /> concentrations in well P-5 have stayed high. The sulfate concentrations in well P-5 are <br /> natural and show that relatively high values naturally exist in this sandstone. <br /> Figure B-18 presents the sulfate concentrations for wells GC-3, P-1, P-3, 3-1 and <br /> COY. The sulfate concentrations in alluvial well P-1 have stayed in the 600 to 1200 mg/I <br /> range, while the sulfate concentration in the Lewis Shale near this well has been <br /> consistently higher. The recent sulfate concentrations for Johnson Gulch well J-1 are <br /> essentially equal to the natural level in the Flume Gulch alluvium at well COY. Sulfate <br /> concentrations in the Flume Gulch wells (GC-3 and COY) have fluctuated from <br /> approximately 400 to 1100 mg/l. • <br /> 3.3 pH <br /> Field pH is an important parameter to monitor because some coal spoils have the <br /> potential to increase acidity of the ground water, which increases the mobility of most <br /> heavy metals. A pH of less than 5 would generally be needed to greatly increase the <br /> mobility of most heavy metals. <br /> Available pH data is tabulated in Table B-1 of Appendix B. The pH of water from <br /> well GB-2 was near neutral in 1999. The pH value from well GB-5 in 1999 was near 8.3, <br /> which seems reasonable. <br /> The field pH of water from the GC wells has generally been slightly above 7.0 and is <br /> at natural values with the initiation of disturbance in this area. • <br /> 3-8 <br />