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' potentiometric levels in the Middle Sandstone in the vicinity of Mines 5 and 6. Monitoring <br />results through year 1994 still show no apparent change in the water levels in the <br />Twentymile Sandstone that could be attributable to mining activities. Water level plots <br />indicate essentially no change. Based upon the 1994 piezometric map (Figure 14), the <br />groundwater gradient in the Middle Sandstone ranges from 130 feet per mile to the <br />southwest to 50 feet per mile to the southwest. The drop in potentiometric levels in the <br />Middle Sandstone unit above the subsided longwall mine panels in the F and E coal <br />seams has created a potentiometric gradient to the south in the vicinity of the longwall <br />panels. A piezometric contour map of the Twentymile Sandstone is presented in Figure <br />15. The map indicates that the gradient is approximately 220 feet per mile to the northwest <br />and shows essentially no change from 1991. <br />• WATER QUALITY <br />The water quality data for the two Trout Creek Sandstone Wells do not indicate any water <br />quality impacts related to mining. The water quality data for the two Trout Creek <br />Sandstone Wells are summarized on Table 5 through 8. A plot of field conductivity <br />measurements is presented in Figure 16. The data for the three Middle Sandstone Wells <br />which are monitored for water quality show no adverse impact or trend. Water quality data <br />are summarized in Tables 9 through 14. Plots of field conductivity for these Middle <br />Sandstone Wells are presented in Figure 17. Wells TR-7A and TR-4 indicate slight <br />reduction in concentrations of major ions over time. All three wells show reduction in <br />concentrations of iron which shows considerable variation in concentrations. The general <br /> <br />4 <br />