2010-08-02_REVISION - M1977300 (28)

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Environmental Protection Plan, Schwartzwalder Mine 14-7 • Table 145. Weighted Average Water Quality for the Upper Mine Workings Weighted PARAMETER Unit ILLRS Wash 146 CO Average General Parameters pH Su 2.7 3.8 8.2 7.9 Alkalinity (dis) mg CaC03/1 <10 < 10 300 170 Alkalinity (tot) mg CaC03/1 < 1 < 1 300 170 E.C. us/cm 7,190 3,740 4,120 1,430 4004 TSS mg/L 10.3 30.4 < 2.5 37.4 18.9 TDS mg/L 11,000 4,200 4,650 1,230 5119 Maior Ions SO4 mg/L 7,200 2,900 2,900 790 3,321 Ca mg/L 360 390 380 110 293 Cl mg/L 130 19 9 5 39 Mg mg/L 270 240 280 140 229 K mg/L < 0.3 14 21 7.4 11 Na mg/L 8 28 29 7 16.8 Nutrients NO3 mg N/1 8.3 2.9 28 4.2 12.4 NH4 mg N/1 < 0.5 < 0.5 < 0.5 < 0.5 0.25 Dissolved Metals • Cu mg/L 19 0.67 0.61 0.04 5.04 Mn mg/L 27 25 0.92 0.57 10.46 U mg/L 150 52 130 29 94 Estimated % Contribution to Upper Level Flows 25% 13% 31% 31% 100% * Weighted averages for pH and alkalinity are not considered to be meaningful for this data set (iii)Evaluation of Precipitation and Dissolution Reactions Controlling Mine Water Chemistry The equilibrium-based modeling approach included speciation of the average water quality from the upper and lower mine workings to evaluate the mineralogical controls on solute concentrations during the initial flooding, and speciation of the mine water from 2007 to evaluate the processes that will control the long- term chemistry of the flooded mine. Speciation was also modeled using the most pH and Eh measurements from 2007. Eh is expected to continue to decrease in mine water as inflow from deep bedrock is no longer exposed to oxygen in the mine voids. In contrast, pH is likely to remain circum-neutral in the flooded mine because the water is well buffered (394 mg/L alkalinity) and the flow from low-pH seeps in the upper workings is small (Table 9-9). (iii).1.1 Upper Mine Water Speciation The speciation run for the average water quality of the upper mine workings indicated a charge imbalance of - 46.77 %. The calculations were performed for oxidizing conditions (Eh = 592 mV) and all solid phases (minerals) for copper, uranium and molybdenum were strongly undersaturated in solution (the input concentrations for molybdenum were estimated from the observed ratio of U to Mo in samples from the flooded mine as data for the upper mine water were not available). Gypsum was the only oversaturated mineral that was likely to precipitate with a saturation index of 0.12. (Appendix Q. (iii). 1.2 Deep Mine Water Speciation The speciation run for the average deep groundwater quality had a charge balance error of -0.65 %. The • calculations were performed for oxidizing conditions at an Eh of 178 mV which is similar to values observed in the flooded mine. As expected, the results indicated near equilibrium conditions for many minerals in solution including calcite and gypsum (Table 14-6). This suggests that the major ion 4109C.100731 Whetstone Associates