2012-02-28_REVISION - M1980244 (104)

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result in the highest potential for runoff, and the ponds can be built and rebuilt to the volume reflecting current conditions according to the sequence presented on Sheet 5. EMP ponds have been configured to be less than 10 feet in height when measured from the existing grade at the downstream toe to the spillway and excavated an additional five feet below grade to provide the optimum depth of 15 feet. Embankments of less than 10 feet in height are not regulated by the Division of Water Resources, Office of the State Engineer under the Dam Safety Regulations. 10.3 East Cresson WHEX and ECOSA Diversion and Sediment Control The proposed MLE2 development includes the extension of the WHEX within the East Cresson Mine area in approximately 2013. The removal of ore from that area will be followed, in close order, by backfilling the WHEX to approximate original contours. After the backfill of WHEX has been completed, the area (shown on Details 1 and 7 in the Storm Water Plan, Appendix 12, Volume VI) will be reclaimed by (1) placement of growth media, (2) reseeding, and (3) reestablishment of drainage channels. CR 82 was recently relocated along the north boundary of the Cresson Project. The storm water runoff from the north side of CR 82 currently flows through a drainage culvert into Grassy Valley, but could flow into the extended WHEX Mine area when it is developed unless other provisions are made to bypass the runoff around that portion of the Cresson Project. Accordingly, EMP -18 will be constructed on the north (upgradient) side of the extended WHEX Mine area to intercept the storm water runoff and road drainage. The accumulated storm water runoff will then be pumped around WHEX and directed into EMP -16 on the west side of Grassy Valley. The storm water runoff will then flow to terminal EMP -17. There is no electrical power grid in that immediate area, so storm water accumulations will be pumped through a 6 -inch pipeline to EMP -18 using solar powered equipment. If, or when, a more intense storm occurs the storm water may require to be transferred using mobile diesel - powered equipment. Since both EMP -18 and EMP -19 will be in close proximity to the high -walls of the extended WHEX Mine area, and are located in more permeable Quander - Bushpark soils, it will be important to construct the basins and embankment as impermeable as possible to avoid possible infiltration of the storm water into the mine area. This MLE2 storm water plan for Grassy Valley includes three new methods to avoid the need for regenerative releases. a. All but the most downgradient EMP ponds in Grassy Valley will be fitted, or retrofitted, with 6 -inch diameter perforated pipe outlets in addition to an emergency spillway. With implementation of that process, the storm water accumulations down Cripple Creek & Victor Gold Mining Company Cresson Project Mine Life Extension 2 10 -4