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both wells appear to have stabilized at around 1000 mg/1 in 1991, • with a slight decline in 1992. TDS concentrations in Well 008-79-6 appear to have increased slightly over the period 1986 through 1989, with an increase during the 1993 water year data being noted, perhaps reflecting the increase in specific conductance in Foidel Creek over the same time period (see Figure 19). Ion composition data for this well does suggest a slight increase in the concentrations of sodium and sulfate during this same period 1986 through 1989. Sodium concentrations in this well exceed levels at all other monitoring locations as a result of cation exchange as ground water migrates to the greater depths represented by well 008-79-06. This is reflected by the increases in sodium, bicarbonate, and SAR during the 1993 reporting period. Future monitoring will determine whether this is a continuing trend. In general, the dissolved solids concentration in both wells appear to have stabilized or decreased slightly since 1989. Also, the TDS concentrations in both wells have remained within the normal range for the Wadqe Overburden. The data does not indicate any significant changes in the trace metals concentrations. Alluvium The alluvial aquifer within the mine area is monitored at two alluvial wells completed in the Foidel Creek alluvium just above the Foidel and Middle Creek confluence. Both wells are completed to the base of the alluvium, about 14 feet below the land surface. Water Levels - The plot of the historic water levels in the two Foidel Creek Alluvial wells and Foidel Creek is presented on Figure 7. The waters levels in the wells and stream show the typical seasonal pattern, of relatively rapid increase and decline due to spring runoff. In addition to the seasonal trend, water levels have generally increased in the wetter period from 1982 through 1986 and have declined slightly since 1986. The seasonal variation is much greater than in other wells as would be expected because of the wells shallow depths and location near the stream. The longer term trends in water levels are similar to that observed in overburden wells and average streamflow. Water quality - The water quality data are summarized in Tables 8 through 11 for the Foidel Creek alluvial wells. The historic dissolved solids concentrations and field conductivity for these wells are plotted on Figures 8 and 9. Seasonal variation is evident in the wells. This is apparently due to flushing effect of the relatively low dissolved solids surface water which recharges the alluvial aquifers during spring runoff. The dissolved solids in the Foidel Creek alluvial aquifer appears to have increased after 1986 as suggested by the trends in Figures 8 and 9. TDS concentrations have also appeared to be fairly stable since the initial rise between 1986 and 1990. Page 3 •