2007-03-16_REPORT - C1981010 (9)

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Flume Gulch has two alluvial monitoring wells, GC -3 and COY. TDS concentrations have been fairly steady in well GC -3 with a small overall decrease during 2006. The 2006 TDS concentrations in the COY well were similar to the 2005 values. The TDS concentrations in the COY well and historical variations in well P -1 show that the Johnson alluvial TDS concentrations are within natural alluvial concentrations in the alluvial aquifers in this area. 3.2 SULFATE Figure B -9 presents the sulfate concentrations for QR wells GD -2, GD -3 and GE -1. Sulfate in backfill well GD-3 decreased significantly in 1996 and then increased to a similar peak level by 2000. Sulfate concentrations in well GD -3 have been fairly steady at this peak concentration for the last seven years. This indicates that the sulfate fluctuations in the backfill aquifer may be larger than the native QR aquifer. Future monitoring of this well will define whether sulfate concentrations will decrease in the backfill aquifer during wet cycles and increase to a maximum during a dry cycle. Concentrations in well GD-2 had overall gradually increased the last few years but declined in 2006. The sulfate concentrations in well GD -2 show that the QR aquifer near well GD -2 has not been significantly affected by the upgradient backfill aquifer water quality. Figure B- 10 also presents sulfate concentrations for QR wells. This figure shows that sulfate concentrations in backfill well GF -11, which is upgradient of QR well GF-6, were lower in 2006 showing a decline from the historic peak in 2001. Future monitoring is needed to define the maximum sulfate concentration in this backfill aquifer which may have been defined in 2001 and 2002. The sulfate concentrations gradually increased in well GF -6, downgradient of well GF -11. Sulfate concentrations for the last few years had gradually increased in QR well GP -5 while a decline was Trapper Mining Company 3 - 2006 Annual Report