2008-04-15_REVISION - M1980244 (309)

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• same as those from naturally vegetated surfaces. Because of this conclusion the study shows that, despite the changes in disturbed area caused by surface mining no net change to basin yield rates has occurred or is expected to change. The study evaluated the acid-generating potential and acid-neutralizing potential of sulfur oxidation within the MLE area. Acid base accounting was conducted for the entire rockmass that will be mined from now until the completion of the proposed MLE. The methodology used was to identify for each 50' x 50' x35' block of material that will be mined the expected total sulfur and total carbon concentrations, based on a total of 30,758 LECO furnace analyses. The environmental effects of weathering of the overburden were evaluated in detail, by the performance of a total of 42 long-term accelerated weathering tests of samples of the rockmass in and adjacent to the diatreme. The study determined, based on the amount of mined ore and stored overburden, the net neutralizing requirement of the overburden will be 2.6 million tons of calcium carbonate; for the ore 0 tons of calcium carbonate; and for the exposed mine walls 207,000 tons of calcium carbonate. The available carbonate in the diatreme was evaluated and the study determined the calcium carbonate available within the diatreme is approximately 500 • times the mass required to neutralize sulfide oxidation in the ore, overburden, and exposed rock walls. Based on this, and the adequacy of the neutralization capacity, the study concluded that acid generated from the proposed MLE will have no impact on the water quality in the regional ground water system. The information derived from the ground water hydrology and geochemistry investigations conducted by Adrian Brown Consultants were considered during development of the mining and reclamation plans for the MLE areas. 4.6 Hydrology The following discussion of surface and ground water hydrology is a summary of the more detailed information contained in Appendix 2, Hydrologic Evaluation, Cresson Project Mine Life Extension. Figure 3-1 in Appendix 2, Volume II provides existing surface and ground water monitoring locations. 4.6.1. Surface Water Regionally, surface water flows from the Cresson Project area are tributary to the Upper Arkansas River Basin. On the south side, surface water would flow into Theresa Gulch and Bateman Creek which are tributaries to Wilson Creek, that • Cripple Creek & Victor Gold Mining Company Cresson Project Mine Life Extension 4-7