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Cresson Project Hvdrogeochemistry AdrianBrown <br />3. The tonnage of material that may be exposed to additional pyrite oxidation due to mining is <br />computed from the affected area, the depth of additional weathering, and the specific weight of <br />the in -place material (14 cu.ft. /ton). <br />The tonnage of material computed to be available in the mine walls is less than 1% of the total rock <br />mined Accordingly, the contribution is ignored. <br />3.2.6 Pit Lakes <br />As the bases of all mines in MLE2 are above the regional ground water table, no pit lakes will form. <br />3.3 Neutralization <br />3.3.1 Effects of neutralization <br />The ground water that seeps through the overburden storage facilities and the mine backfill has the <br />potential to dissolve acid and metallic constituents of sulfide oxidation in the overburden. An analog of <br />the quality of the resulting water was obtained from the HCT. The chemical analysis of this water is <br />presented in Table 6. <br />The effect of neutralization on this water was determined by neutralization using four alkaline materials: <br />• Natural calcite blend from the Main Cresson mine and the Globe Hill mine <br />• Reagent grade calcium carbonate <br />• Reagent grade calcium oxide <br />• Reagent grade sodium hydroxide <br />The results are presented in Cresson Project Mine Life Extension (Amendment 9) permit application <br />(CC &V, 2008), and the results are summarized in Table 6. <br />Contact and neutralization with natural and reagent calcite causes the following: <br />• Increases the pH from —3 units to —8 units <br />• Increases alkalinity from essentially zero to >100 mg/L <br />• Eliminates acidity <br />• Increases total dissolved solids concentration to —3000 mg/L <br />• Decreases Al, As, Cd, Cr, Fe, Mn, Ni, and Zn to close to detection concentrations <br />• Leaves Cu, Pb, Hg, and Se essentially unchanged, but generally at low levels <br />• Increases Mo, Sb, Sr and U, generally to low levels, due to the presence of these constituents in <br />the natural calcite <br />The water quality resulting from neutralization of the products of oxidation of overburden material is <br />compared with the concentration of water emerging from the Carlton Tunnel in Table 6. The quality of <br />the neutralized water is substantially indistinguishable from that of the neutralized HCT water, <br />indicating that the genesis of both is the same: neutralized sulfide oxidation products. <br />1385L.20120125 17 <br />