2010-08-02_REVISION - M1977300 (28)

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Environmental Protection Plan, Schwartzwalder Mine 14-9 • Table 147. Controlling Mineral Phases in Flooded Mine Water Mineral Composition Saturation Index May 21, 2001 Saturation Index Aril 18, 2002 Saturation Index May 20, 2003 Saturation Index June 27, 2007 Calcite CaC03 0.16 0.52 0.46 0.77 C02 as C02 -1.47 -1.75 -1.67 -1.99 Al(OH)3 (am) Al(OH)3 -0.80 -0.53 -0.52 -0.94 Ferrih drite Fe(OH)3 1.16 -0.22 -0.33 -1.01 Gypsum CaSO4.2H2O -0.02 0.00 0.07 -0.18 Magnesite M C03 -0.26 0.04 -0.03 -0.06 Rhodochrosite MnC03 -0.37 0.14 0.22 0.85 Positive values are oversaturated; negative values are undersaturated (iii). 1.4 Modified Reflooded Mine Water Speciation Eh appears to show a recent decreasing trend in the flooded mine water, based on a limited depth profile conducted in the #2 Shaft on November 12, 2007. Eh values were only one-half to one-quarter the value of previous (2003) measurements. The pH was near neutral (6.85), but slightly lower than in June 2007 (7.53). To analyze the effect that decreased Eh or pH might have on future mine water chemistry, mine water concentrations from the June 2007 laboratory analysis were modeled with lower pH and Eh values. Of particular interest in these speciation models was the increase of the saturation index of the potential uranium concentration-limiting species uraninite (UO2) from undersaturated to oversaturated. June 2007 water quality data was initially speciated using a pH value of 7.53, as measured on the sample date. The same data was speciated again, changing only the pH. A value of 6.85 was selected because it reflects the • most recently measured pH in November 2007. With this slightly acidic pH, uraninite showed slight oversaturation (SI = 0.26). It was also found that uraninite moves from undersaturation to oversaturation as Eh decreases from 23 to -25. A decrease of this magnitude in the mine water seems possible given the reduction in measured Eh from near 300 at the most oxidizing to the current measurement of 23. It is possible that the decrease in Eh has occurred because the groundwater inflow from bedrock is no longer exposed to oxygen in the mine voids. While the observed decrease in pH in the upper 40 ft of the shaft could result from the increasing relative contribution of acidic, oxidized water from the upper mine workings and the slowing influx of deep mine groundwater, the flooded mine water is well buffered (394 mg/L alkalinity) and pH is likely to remain circum-neutral in the flooded mine. Saturation indices for uraninite and other phases of interest are presented in Table 14-8. • 4109C.100731 Whetstone Associates