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Permit C-81-071 1994 Annual Hydrology Report • general decline in water levels due to the relatively low runoff since 1987. No explanation has been found for the sharp rise and fall in the water levels in we11009-S-10 during 1994. While the seasonal variation in the water levels in the Foidel Creek alluvium is readily apparent, no impact from the mining is evident. The average water level in the 001-S-5, AV-1 and 008- AV-2 wells, adjusted for differences in spring runoff, has not changed since monitoring began in 1979. The water level data for the Fish Creek alluvial wells do not show any impact from the reclaimed Mine 2 Area. Water Quality The water quality data area summarized in Tables 10 through 15 for the Foidel Creek alluvial wells and Tables 16 through 21 for the Fish Creek alluvial wells. The historic field conductivities for the Foidel Creek wells are plotted on Figure 14, and for the Fish Creek wells on Figure 15. Seasonal variation in conductivity is apparent in the wells, This is probably due to the flushing effect of relatively tow dissolved solids surface water that recharges the alluvial aquifers during spring runoff. There was a small increase in the average salt content of the Foidel Creek alluvial groundwater starting in the 1987 water year and continuing through the 1994 water year. This is probably due to the relatively low runoff that has persisted since 1987. The water quality in the Foidel Creek alluvial wells show a downstream increase in total dissolved solids and conductivity and change from asodium-bicarbonate type to a mixed calcium-sodium-bicarbonate sulfate type. • The change is apparent in the reach between the 009S-10 well and the 001-5-5 well. This is primarily attributable to recharge of alluvium by Foidel Creek water. Foidel Creek receives sediment pond discharges, containing elevated concentrations of dissolved solids, calcium and sulfate, in the reach of Foidel Creek above the 001-S-5 well. The sediment pond water is largely derived from spoil runoff and spoil springs. The spoil springs, in particular, are characterized by high sulfate, calcium and dissolved solids concentrations. There is no indication of any significant increase in alluvial groundwater trace metals during 1994. The water quality data for the Fish Creek alluvial wells upstream and downstream of Mine 2 do not indicate any impacts (Figure 15). The 006-AW-2 well, downgradient from the discharge point, does show a higher conductivity during the baseflow period than in previous years related to underground mine discharge. The data does not indicate any significant changes in the trace metals concentrations. The iron and manganese levels in the wells, including the upstream well, are often relatively high. SPOILS Five wells in the spoils are monitored. They are all located at Mine 1 and were installed in 1985 and 1986. Two of these are only monitored for water level. • EP4TE%T.DOC 03/17/97 Page 3