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the HI aquifer at this location are possible. A gradual decline in sulfate concentrations has <br />been observed over the last few years in well GP-3, which is further downgradient. Sulfate <br />concentrations in eastern HI aquifer well GC-1 have been greater than those in well GMP-1 <br />and are natural. Therefore, a sulfate concentration of at least greater than 600 mg/l is <br />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 <br />wells. A gradual declining trend in 3rd White Sandstone well GB-2 has been occurring over <br />the last few years. The latest value in well 81-03A is also lower but needs additional <br />analysis to confirm this level. The latest value in well P-8 shows a significant increase in <br />sulfate concentration in 1996 and is probably correct because a similar increase was <br />observed in the TDS concentration on this sample. Sulfate concentrations in well P-8 are <br />presently similar to those that have been observed for numerous years in 2nd White <br />Sandstone well P-5. The higher natural concentrations in well P-5 makes it difficult to <br />determine whether the present increases in well P-8 are due to the effects of mining. <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. <br />Figure B-18 presents the sulfate concentrations for wells GC-3, P-1, P-3, J-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 sulfate concentrations in 1996 in well P-3 show an increase that <br />is well within natural observed levels defined in the past for the well. Sulfate concentrations <br />for Johnson Gulch well J-1 significantly increased in 1996. This sulfate concentration must <br />3-7 <br />