2012-02-28_REVISION - M1980244 (104)

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10.0 SURFACE WATER MANAGEMENT 10.1 General The surface storm water management for MLE2 was designed by Ellis Engineering, Inc. ( "Ellis ") and Steffens and Associates ( "Steffens "), except for the SGVLF and AGVLF surface storm water management systems which were designed by AMEC in association with the design of the VLFs. The hydrologic design parameters used to design the storm water run -off management system for MLE2 activities are the same as those used for previous submittals including Amendments Nos. 7, 8, and 9. The design storms for the Cresson Project previously approved by the OMLR are as follows (from the NOAA iso- pluvial charts): • 10 -year, 24 -hour = 2.4 inches • 100 -year, 24 -hour = 3.5 inches One change was implemented for MLE2. A 2.7 inch design storm event was used for the 10- year, 24 -hour storm for all areas, except the areas covered by SGVLF and AGVLF downgradient detention ponds that were designed by AMEC to contain the 25 -year, 24 -hour storm event. The mining areas, SGOSA, ECOSA, SGVLF, AGVLF, and support facilities for the Cresson Project incorporate designs to protect the quality and quantity of the Cresson Project area ground and surface waters. The VLFs including ADR facilities are designed as zero discharge systems with upgradient storm water runoff to be diverted around the facilities. The VLFs are designed and constructed to contain precipitation from a 100 -year, 24 -hour storm event within the lined area. Integration of the ADR facilities into the VLF liner systems provides for further containment of solutions. Storm water runoff from undisturbed areas is diverted around areas of disturbance to the extent possible. Storm water runoff from disturbed areas will be controlled with BMPs to minimize erosion and to retain excessive sediments. CC &V operates in accordance with the Colorado General Storm Water Permit for the facility. Storm water runoff resulting from intense, but infrequent, storm events will be controlled and routed around the new disturbance areas associated with the SGVLF and SGADR, extension of the North Cresson Mine area, extension of the WHEX portion of the East Cresson Mine area, and the redesigned ECOSA in the same manner as the existing disturbance areas. This will be accomplished with a series of diversion ditches constructed at various stages in the operations. The size and geometry of the diversions will be based on the anticipated location and longevity Cripple Creek & Victor Gold Mining Company Cresson Project Mine Life Extension 2 10 -1