2016-01-07_PERMIT FILE - C2010089A (11)

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Surface Water Protection Section 2.05.3(3), Mine Facilities, contains descriptions, designs, and plans for a sediment ponds, roads, diversions, and culverts that will be constructed and utilized at New Horizon North mining area during mining. All facilities that are discussed in Section 2.05.3(3) have been designed to ensure that the hydrologic balance is protected. The discussion for surface water protection has been separated into three parts: 1) surface water quality; 2) surface water quantity; and 3) surface water monitoring. Surface Water Quality Sediment ponds will be adequately designed and will be constructed during the proposed operations for controlling surface water runoff from disturbed and reclaimed areas. An NPDES permit will be obtained from Water Quality Control Division, Colorado Department of Public Health and Environment to allow the discharge of water from the sediment ponds. The design of the ponds has been developed to prevent additional contributions of sediment to stream flow outside the permit area, to minimize erosion, and incorporates detention times sufficient to ensure that all applicable effluent standards will be met. The pond discharge structures are designed according to standard engineering design procedures for protecting against erosion via emplacement of riprap and/or energy dissipaters. The pond will be removed and reclaimed following the completion of mining and reclamation unless prior approval to retain this impoundment is obtained. The impact of a sediment pond and runoff from reclaimed areas on the quality of receiving streams was found to be of minimal significance (see Probable Hydrologic Consequences at the end of this section). All terms and agreements specified in the approved NPDES permit will be adhered to during the mining operation to ensure that effluent will meet the permit limitations. Based on past water quality monitoring at New Horizon 2 Mine, it is anticipated that no treatment of pond effluent is necessary. However, should the need for treatment of pond effluent be demonstrated, WFC will commit to designing treatment facilities or procedures to handle the equivalent of a 10 -year, 24-hour effluent volume. Plans for sampling overburden and topsoil after backfilling and grading have been developed and are presented in Section 2.05.4(2)(d), Topsoil Redistribution. Based on these plans, surface runoff from disturbed reclaimed areas will not come in contact with materials that would contribute to elevated levels of acid or toxic constituents. Topsoil handling procedures (Section 2.05.4(2)(d), Topsoil Redistribution) and revegetation methods (Section 2.05.4(2)(e), Revegetation) have been developed to stabilize the landscape, prevent erosion, and minimize the additional contributions of sediment to runoff. They include: the seeding of temporary disturbance and topsoil piles; mulching, chisel plowing and deep ripping; cover cropping; and timely reseeding of reclaimed areas (regraded and topsoiled) with seed mixes designed for rapid establishment and development of effective hydrologic cover. Section 2.05.6(3) Page 5 Sept. 2015 (TR -11)