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appear to have increased slightly over the period 1986 through <br />• 1989, perhaps reflecting the increase in specific conductance in <br />Foidel Creek over the same time period (see Figure 19). Ion <br />composition data for this well does suggest a slight increase in <br />the concentrations of sodium and sulfate during this same period <br />1986 through 1989. Sodium concentrations in this well exceed <br />levels at all other monitoring locations as a result of cation <br />exchange as ground water migrates to the greater depths represented <br />by well 008-79-06. <br />In general, the dissolved solids concentration in both wells appear <br />to have stabilized or decreased slightly since 1989. Also, the TDS <br />concentrations in both wells have remained within the normal range <br />for the Wadge Overburden. The data does not indicate any <br />significant changes in the trace metals concentrations. <br />Alluvium <br />The alluvial aquifer within the mine area is monitored at two <br />alluvial wells completed in the Foidel Creek just above the Foidel <br />and Middle Creek confluence. Both wells are completed to the base <br />of the alluvium about 14 feet below the land surface. <br />Water Levels - The plot of the historic water levels in the two <br />Foidel Creek Alluvial wells and Foidel Creek is presented on Figure <br />7. The waters levels in the wells and stream show the typical <br />• seasonal pattern, of relatively rapid increase and decline due to <br />spring runoff. In addition to the seasonal trend, water levels <br />have generally increased in the wetter period from 1982 through <br />1986 and have declined slightly since 1986. The seasonal variation <br />is much greater than in other wells as would be expected because of <br />the wells shallow depths and location near the stream. The longer <br />term trends in water levels is similar to that observed in <br />overburden wells and average streamflow. <br />Water quality - The water quality data is summarized in Tables 8 <br />through 11 for the Foidel Creek alluvial wells. The historic <br />dissolved solids concentrations and field conductivity for these <br />wells are plotted on Figures 8 and 9. Seasonal variation is <br />evident in the wells. This is apparently due to flushing effect of <br />the relatively low dissolved solids surface water which recharges <br />the alluvial aquifers during spring runoff. The dissolved solids <br />in the Foidel Creek alluvial aquifer appears to have increased <br />after 1986 as suggested by the trends in Figures 8 and 9. TDS <br />concentrations have also appeared to be fairly stable since the <br />initial rise between 1986 and 1990. <br />Ion composition and concentrations in the alluvial wells is very <br />similar to the ion composition and concentrations of the Middle <br />Creek water below the mine (Station 29) but significantly lower in <br />TDS, 804 and cations than Foidel Creek above the mine. These <br />results indicate that the water quality of the alluvium at the mine <br />Page 3 <br />