2008-04-15_REVISION - M1980244 (309)

Home Browse Search

i reached. It is estimated to take approximately 50 years for ECOSA to reach field capacity and begin flow of infiltrated water. The expected rate of flow from ECOSA after that time is expected to be approximately 23 gpm. Based on the expected flow rate, existing neutralizing capabilities of the ECOSA rock, and the oxygen limiting capabilities of the low permeability cover, flow from the ECOSA is expected to be of similar water quality as the regional ground water table exiting the Carlton Tunnel. Appendix 6, Volume IV provides a complete discussion of the expected performance of the ECOSA low permeability construction design. Surface Water Management CC&V, through their consultant Steffens and Associates, has evaluated the final configuration for the ECOSA and designed a surface water management system to route flows and control sediment transport and erosion during construction through completion of reclamation. This system is discussed in Section 9 of this Project Description and Appendix 10, Volume VII. The surface water management system for final configuration of the ECOSA uses • the same criteria as outlined above in subsection 5.7.1 for the SGOSA Extension. Diversion and conveyance structures are designed to route flows from the 100- year, 24-hour precipitation event. These flows are directed to detention basins, with the most downgradient structures designed to contain twice the 10-year, 24- hour precipitation event. Stability The geotechnical stability analysis of the ECOSA was conducted in a manner consistent with that of previously approved documents and with the SGOSA Extension discussed above. In summary, this analysis used a peak ground acceleration of 0.08 g for the pseudo-static analysis. Other input parameters remain the same as those used in other analyses and were derived from field examinations, laboratory tests, use of accepted numerical assumptions for certain rock types, and the proposed dimensions of the overburden fill during placement and upon regrading. FOS for the ECOSA were derived for both static and pseudo- static conditions. The stability was analyzed for post-reclamation conditions and the results indicate that the minimum static FOS was equal to or exceeded 1.8 and the minimum pseudo-static FOS exceeded 1.5. For additional details on the • stability analysis for the ECOSA please refer to Appendix 7, Volume IV. Cripple Creek & Victor Gold Mining Company Cresson Project Mine Life Extension 5-19