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increasing trend but concentrations have been steady the last fifteen years. Overall steady sulfate <br />concentrations have been observed in well GP -7. Sulfate concentrations in eastern HI aquifer well <br />GC -1 have been similar to the previous higher values in well GMP -1 and had to be natural until the <br />last few years. The sulfate concentration in well GLEV-3 are similar to those in well GMP -1 but <br />have to be natural due to the ground -water flow direction at this well. Therefore, an upper limit for <br />sulfate concentration that is greater than 600 mg/l may be needed to indicate that the increases may <br />be due to the mining operation. The 2017 value from well GC -1 was similar to past values but <br />significantly less than the value to the east from well GLEV-3. <br />Figure B-13 presents the sulfate concentrations for three 3rd White Sandstone wells. The <br />sulfate values from well P-8 have overall very gradually decreased the last three years while they <br />have been elevated for more than twenty years. The magnitude and timing of the prior increase in <br />sulfate concentrations in well P-8 indicate that this is due to mining. The sulfate changes in wells <br />GC -2 and GP -9 are within the natural range of concentrations for this aquifer. Figure B-13 presents <br />the sulfate concentrations for well P-5. Well P-5 contained only a small amount of water for a <br />sample in 2017. The prior sulfate concentrations in well P-5 were natural and show that the 2017 <br />relatively high value could be natural for this sandstone. <br />Figure B-14 presents the sulfate concentrations for alluvial wells GC -3, P-1, J-1 and COY. <br />The sulfate concentrations in alluvial well P-1 have been variable with recent values slightly higher <br />than historical natural values for this well. The sulfate concentrations for Johnson Gulch well, J-1, <br />gradually increased the last few years with these recent values being slightly higher than the natural <br />levels in the Flume Gulch alluvium at well COY. Sulfate concentrations in the Flume Gulch wells <br />(GC -3 and COY) have fluctuated from approximately 300 to 1200 mg/l. The natural variability in <br />Trapper Mining Company 3-7 <br />2017 Annual Report <br />