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• In summary, the water quality of all three sandstone aquifers do <br />not indicate any significant trends or adverse impacts related to <br />mining at Mines 5 and 6. <br />COAL <br />FLOWS <br />Plots of the measured discharges for the two #5 Mine discharge <br />points are presented in Figures 19 and 20. The flows are measured <br />at the discharges by totalizing flow meters on the dewatering sump <br />pumps. The mean flow rate did not exceed the mine inflow <br />predictions from the Probable Hydrologic Consequences (PHC) <br />evaluation. Year 4 of the PHC prediction which corresponds most <br />closely with the 1992 mining year indicated combined inflows of 850 <br />to 1050 gpm for the #5 and #6 Mine operations. The 1992 average <br />discharge was 310 gpm from the #5 Mine sump, and 177 gpm from the <br />7 North Angle. The combined average discharge was 487 gpm. The <br />water produced in the #6 Mine is pumped underground to the #5 Mine <br />sump and is accounted for at the discharge from that point. <br />The low discharge from the 7 North Angle Sump during the first half <br />of the year was due to the failure of the pump. The discharge from <br />the sump generally ranges from 250 to 450 gpm when the pump is <br />working. <br />• WATER QUALITY <br />Summaries of the water quality data for the mine discharge are <br />presented in Tables 19 through 22. The #5 Mine sump discharge is <br />NPDEs discharge point #003. The 7 North Angle Discharge is NPDES <br />discharge point #024. The #5 Mine discharge water quality <br />indicates a slight increase in dissolved solids concentrations over <br />time. The plot of dissolved solids presented in Figure 21 shows <br />that the average dissolved solids in the #5 Mine discharge water <br />have increased from about 800 mg/1 in 1982 and 1983 to <br />approximately 904 mg/1 in 1992. This increase in dissolved solids <br />appear to have leveled off since 1986. <br />The average dissolved solids concentration for the 7 North Angle <br />discharge increased considerably in 1991 from about 875 mg/1 in <br />prior years to 1285 in year 1991 and 1992. This trend is related <br />to the accumulation of water in the North Angle Sump location while <br />the pump was out of order. This water was allowed to equilibrate <br />within old workings and rubbelized subsidence panels. The maximum <br />• 4 <br />