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1 1 1 1 lJ MINE INFIAW MONITORING The inflow to the underground mine is monitored in two ways. The flow rate and water quality of the discharge from the mine (Sites 109 and 115) are monitored before they enter Sediment Pond D and Fish Creek, respectively, and an annual inflow study is performed. In the inflow study the flow rate and water quality of major inflows to the mine are measured. The 1990 inflow study is presented in Appendix A. FIA W Plots of flow rate verses time are presented on Figures 41, 42 and 44. The data indicates that flow rate was fairly constant at approximately 0.2 cfs (90 gpm) from 1984 through the first half of 1986. In the second half of 1986 the average discharge rate increased to approximately 0.3 cfs (140 gpm) and averaged 0.33 cfs (149 gpm) to 0.37 cfs (166 gpm) in 1987 to 1989. In 1990 the total discharge from the underground mine was 0.27 cfs. This decrease could be due to a decrease in mine inflows or it could be due to water being stored in the new underground sump for the Fish Creek Borehole. The discharge rate is within the spectrum of the rates predicted for this period of mine development. The mine inflow study, performed in December, 1990, indicated that no single type of activity or location in the mine accounted for a majority of the discharge. No large inflow could be attributed to a fault zone. Other than during spring runoff and storm water runoff events most of the discharge from Pond D is from the underground mine. Water Quality Summaries of the water quality for Station 109 aze presented on Tables 52 and 53 and for Station 115 is presented on Table 58. The plots of field conductivity of the Pond D and Site 109 discharges are presented on Figures 46 and 47. Prior to the second half of 1986 the average conductivity level was approximately 2000 umhos/cm. In the second half of 1986 the level increased to approximately 3300 umhos/cm. No significant increases have been noted since -10-