2008-04-15_REVISION - M1980244 (351)

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• 9.3 East Cresson WHEX and ECOSA Diversion and Sediment Control EMP010 was to be constructed in Grassy Valley to handle runoff from the East Cresson Mine area, but has never been constructed. As part of the MLE, the sediment controls in this area were redesigned to handle storm water flows from the WHEX and ECOSA. The design standards are the same as previously presented (100-year, 24-hour peak flow designs for the diversion structures and twice the 10-year, 24-hour storm runoff for the sediment ponds). Trapezoidal channels will convey flows and these channels will be lined with riprap when velocities exceed 5 feet per second. Western portions of the WHEX will report to EMP010. Eastern portions of the WHEX as well as the ECOSA will report to one of three sediment ponds: EMP015, EMP016, EMP017. During mining, all of the ponds will be used for sediment control. Upon closure EMP010 will not be needed but may remain as a wildlife watering pond. EMP015, EMP016, and EMP017 will be used for mining and post closure. EMP015 and EMP016 will include an engineered spillways which will direct overflows to EMP017. 9.4 VLF Diversion and Sediment Control Storm water will also be routed around the VLF. Temporary diversions may be constructed as necessary to route upgradient runoff around the VLF during the • construction phases. These temporary diversion structures are discussed in Appendix 8, Volumes V and VI. Sediment control during construction activities at the VLF will be the responsibility of the contractors following guidelines established by CC&V. Contractors will be required to install and maintain appropriate storm water runoff and erosion controls during construction of the facilities. BMP's for sediment control include but are not limited to riprap, check dams, hay bales, silt fence, erosion control fabric and other effective methods as appropriate. Operational and permanent diversions for the Phase 5 VLF are discussed in Appendix 8, Volumes V and VI. The operational and permanent diversions are located on the north and south end of the VLF and are trapezoidal in design and sized to convey flows from the 100-year, 24-hour storm event. The north diversion will convey flows to a sediment pond designed to contain twice the 10-year, 24-hour storm event. The south diversion will carry flows from undisturbed areas and will be routed to an existing topographic bench. • Cripple Creek & Victor Gold Mining Company g Y Cresson Project Mine Life Extension 9-3