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1 1 GROUND WATER MONITORING BEDROCK ' Sandstone Aquifers Four sandstone aquifers are monitored at the site. They are, in ascending ' order: Trout Creek Sandstone (2 wells), Middle Sandstone (6 wells), Twentymile Sandstone (3 wells), and the lowermost sandstone bench of the White Sandstones (3 wells). The No. 5 Mine is between the Trout Creek ' Sandstone and the Middle Sandstone. The No. 9 Mine is between the Twentymile Sandstone and the White Sandstone. Water Levels ' Plots of the water levels in wells in the upper three aquifers are presented in Figure 3 to Figure 14. The water level measured in the Twentymile Sandstone has continued to remain fairly constant. A ' piezometric contour map of the Twentymile sandstone is presented on Figure 16. The indicated gradient is 525 feet per mile to the northwest. The high indicated gradient is probably a result of one of the wells, Well 259, being in a discharge area of the aquifer. ' The plots indicate that the water levels in the Middle Sandstone stopped declining in most areas of the aquifer in 1983 to 1984. Since that time, ' the water levels have been rising in all the wells except 83-03. The changes are probably due to movement in the center of dewatering activity and due to the above normal recharge during 1983 and 1984. Based upon the 1985 piezometric map (Figure 15), the ground water gradient in the Middle ' Sandstone ranges from 150 feet per mile to the southwest to 400 feet per mile to the west. 'i ' The 1983 piezometric levels in the White Sandstone indicate that the No. 9 Pline may not be effecting the 4lhite Sandstone. The rise in water levels in the White Sandstone wells is also probably due to the high recharge in 1983 and 1984. As there was no significant decrease in the discharge from ' the No. 9 Mine until 1985, the water level change in the wells probably can not be attributed to the effects of mining. Based upon the 1985 piezometric map (Figure 17), the ground water gradient in the White ' Sandstone has not changed significantly and is approximately 100 feet per year to the northwest. ' Water Quality The water quality data for the sandstone aquifers are presented on Table 5 to Table 12. The data indicates that the wa±er quality of all four sandstone aquifers is fairly constant over the whole period of measurement. The tables include either all data collected through 1985. Also, carbonate data is included when it is greater than zero (this ' applies for all the water quality data). -2-