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in concentrations of major ions over time. All three wells show reduction in concentrations of iron which <br />• shows considerable variation in concentrations. The general reduction in iron concentrations may be the <br />result of better purging of well bore volumes prior to sampling plus a switch to dissolved concentration <br />analysis. <br />The water quality data for the two Twentymile Sandstone Wells, No. 9 Mine Well and Well 259 show no <br />adverse impact or trend. Water quality data are summarized in Tables 16 through 18. Plots of field <br />conductivity over time are presented in Figure 18. The only apparent trend is a reduction in the variability <br />of sampje analysis. This may be the result of improvements in sampling procedures and analyzing for <br />dissolved metals. <br />In summary, the water quality of all three sandstone aquifers do not indicate any significant trends or <br />adverse impacts related to mining at Mines 5 and 6. <br />• COAL <br />FLOWS <br />Plots of the measured discharges for the two #5 Mine discharge points are presented in Figures 19 and 20. <br />The flows are measured at the discharges by totalizing flow meters on the dewatering sump pumps. The <br />mean flow rate did not exceed the mine inflow predictions from the Probable Hydrologic Consequences <br />(PHC) evaluation. Year 4 of the PHC prediction which corresponds most closely with the 1991 mining year <br />indicated combined Inflows of 850 to 1050 gpm for the #5 and #6 Mine operations. The 1991 average <br />discharge was 454 gpm from the #5 Mine sump, and 219 gpm from the 7 North Angle. The combined <br />average discharge was 673 gpm. The water produced in the #6 Mine is pumped underground to the #5 <br />Mine sump and Is accounted for at the discharge from that point. <br />The low discharge from the 7 North Angle Sump during the first quarter and the decline at the end of 1991 <br />• 5 <br />