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groundwater gradient in the Middle Sandstone in the vicinity of the mining operation <br />generally decreases from the southeast to the northwest as reflected on Figure 11. The <br />piezometric contour map of the Twentymile Sandstone is presented as Figure 12. This <br />gradient remains generally consistent with previous years, according to 1998 <br />measurements. <br />WATER QUALITY <br />The 1998 field parameter data for the Trout Creek Sandstone well (No. 5 Mine) do not <br />suggeest any significant water quality impacts related to mining. The water quality data <br />for the Trout Creek Sandstone well (5 Mine Well) is summarized on Tables 5 and 6. A <br />plot of field conductivity measurements is presented in Figure 13. <br />• <br />The field parameter data for the three Middle Sandstone wells (TRH, TR-7a, 81-01), <br />again, suggest no adverse impact or trend. Water quality data are summarized in <br />Tables 7 through 12. Plots of field conductivity for these Middle Sandstone Wells are <br />presented in Figure 14. The conductivity measurements recorded at well 81-01 <br />continue to stabilize at values near those typically observed for the other Middle <br />Sandstone wells (TRH AND TR-7A). Wells TR-7A and TRH indicate slight reduction <br />in concentrations of major ions over time. Historically, all three wells show reduction in <br />concentrations of iron which shows considerable variation in concentrations. The <br />general reduction in iron concentrations may be the result of better purging of well bore <br />volumes prior to sampling plus a switch to dissolved concentration analysis. <br />• ca,-0ea ,~a,nHR Page 5 <br />