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<br />' GROUND WATER MONITORING <br /> <br />BEDROCK <br />' Sandstone Aquifers <br />Three sandstone aquifers are monitored at the site. They are, in <br />ascending order: Trout Creek Sandstone (2 wells), Middle Sandstone (6 <br />' wells) and Twentymile Sandstone (3 wells). The No. 5 and No. 6 Mines are <br />' Water Levels <br />Plots of the water levels in wells in the three aquifers are presented in <br />' Figures 3 through 12. The water levels in the Middle and Twentymile <br />Sandstones generally are showing an upward trend. For most wells, this <br />trend began in 1983 or 1984. As discharges from the mines in the area <br />' where constant or increasing during this period, the water level changes <br />appear to be the result of climatic factors. The years 1980 and 1981 were <br />very dry years and the following two years were more normal years. <br /> During this earlier period, water levels generally fell. Years 1984 and <br />' 1985 were very wet years and the spring runoff in 1986 was above normal. <br /> During this period, the water levels in the aquifers rose. The water <br /> levels in the Trout Creek Sandstone do not exhibit any trend. The water <br /> levels in the No. 5 Mine Well show the effects of pumping the well. <br /> Based upon the 1987 piezometric map (Figure 13), the ground water gradient <br /> in the Middle Sandstone ranges from 130 feet per mile to the southwest to <br />' 350 feet per mile to the west. A piezometric contour map of the <br /> Twentymile sandstone is presented on Figure 14. The indicated gradient is <br /> 500 feet per mile to the northwest. The high indicated gradient is <br />' probably a result of one of the wells, Well 259, being in a discharge area <br /> of the aquifer. <br />' r <br />alit <br />W <br />t <br /> Qu <br />a <br />e <br />y <br />' The water quality data for the sandstone aquifers are summarized in Tables <br />5 through 18. Plots of field conductivity are presented in Figures 15 <br /> through 17. The data indicates that the water quality of all four <br /> sandstone aquifers is fairly constant over the whole period of <br />' measurement. The field conductivities seem to show a slight downward <br /> trend; however, the corresponding dissolved solids values do not show the <br /> same downward trend. The tables include all data collected through 1987. <br />1 <br />between the Trout Creek Sandstone and the Middle Sandstone. <br />' 2 <br />