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1 <br />1 <br /> <br />' GROUND WATER MONITORING <br />BEDROCK <br />SANDSTONE AQUIFERS <br />t Three sandstone aquifers are monitored at the site. There are, in <br />ascending order: Trout Creek Sandstone (2 wells), Middle Sandstone <br />' (6 wells), and Twentymile Sandstone (3 wells). The #5 and #6 Mines <br />are between the Trout Creek Sandstone and the Middle Sandstone. <br />WATER LEVELS <br />The water levels in the Trout Creek Sandstone recovered to the <br />' levels measured in 1986 through 1988. However, the levels in the <br />Okie Plaza Well, while recovered from the short term decline <br />measured in 1989, still appear to be declining slightly. The water <br />levels in the middle sandstone are still declining, probably in <br />' response to the dewatering of the underground mine. The steep <br />declines in the levels in Wells TR-4, 01-01, 83-01 and 83-02 appear <br />to have leveled off in the last half of 1990. Well 83-02 is <br /> located 700 feet horizontally from a long well panel and was <br />' probably significantly affected by thi s mining activity. The water <br /> levels in the Twentymile Sandstone still do not appear to be <br /> affected by mining activities and did not change significantly in <br />' 1990. <br />Based upon the 1990 piezometric map (Figure 14), the ground water <br /> gradient in the Middle Sandstone ranges from 110 feet per mile to <br />' the southwest to 70 feet per mile to the southwest. The <br /> piezometric surface in 1990 was greatly affected by the large <br />' decline in water level <br />reversed the gradient. in Well 83-02 which appears to have locally <br />A piezometric contour map of the Twentymile <br /> Sandstone is presented in Figure 15. The indicated gradient is 220 <br /> feet per mile to the northwest. <br /> <br /> WATER QUALITY <br /> The water quality data for the sandstone aquifers are summarized <br /> in Tables 5 through 18. Plots of field conductivity are presented <br /> in Figures 16 through 18. The data indicates that the water <br />' quality of all three sandstone aquifers is fairly constant over <br /> the whole period of measurement. The tables include all data <br /> collected through 1990. The data does not indicate any significant <br /> trends. <br />' -1- <br />