2020-03-31_PERMIT FILE - C1981019A (6)

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RULE 4 PERFORMANCE STANDARDS With a few exceptions, Colowyo plans to have all surface runoff from the disturbed area pass through sedimentation ponds. Sedimentation ponds are discussed in detail under Section 4.05.6, and their location is shown graphically on the Hydrology - South Map (Map 12) and the Hydrology - North Map (Map 11). Exceptions include such areas as topsoil stockpiles located outside of the Section 11 ditch (MR - 15), topsoil stockpiles located along the paved haul road (MR -18), East Taylor holding pond and pump station (TR approved on November 1984), raw and potable water lines, and railroad loop. Erosion and sediment control is achieved by protection with vegetation or rock. The demonstration presented in MR -18 provides a representative example of how vegetative cover can provide for sediment control. The Administration and Security buildings have associated paved parking areas which generate no sediment. Colowyo employs various methods to manage water which periodically collects internal to the mining operation and does not reach sedimentation ponds. various sumps, ditches, pumps, hoses and pipes, etc. will be employed to control water within pits and/or route water between pits. The ultimate destination of such water will be for operation's use (dust control, etc.), evaporation or seepage into the backfilled spoil areas. In addition to the mining, reclamation and treatment methods described and referenced in this Section, further protection of the hydrologic balance will be established by an on-going plan for monitoring potential changes in surface water quality and quantity and groundwater quality. This monitoring plan is described under Section 4.0-5.13 and the monitoring locations are graphically shown on Water Monitoring Sites for Permit No. CO -019-81 (Map 1013). Excess spoil valley fill areas are located downdip of mining and reclamation areas and periodic monitoring for seeps and springs and periodic monitoring of piezometer wells will detect the formation of spoil springs. 4.05.2 Water Quality Standards and Effluent Limitations The plan for protection and control of drainage and sediment described in 2.05.6 provides that surface drainage from the disturbed area within the permit area will be passed through sedimentation control structures. All ponds will be constructed and maintained to contain or treat the volume design for a 10 -year, 24-hour precipitation event. The accumulation of sediment in the ponds will be monitored quarterly. In addition, grab samples of water, as required, will be collected from pond discharges to measure the effectiveness in meeting the applicable Colorado and Federal water quality standards. The proposed sedimentation ponds have been designed and will be constructed and maintained to effectively trap sediment from runoff resulting from precipitation events up to and including the 10 -year, 24-hour precipitation event. Drainage from the mining area, after treatment in sedimentation ponds, is not anticipated to exceed the effluent limitations of any federal or Colorado agency requirements. Baseline groundwater Rule 4 Performance Standards 4-8 Revision Date: 5/25/18 Revision No.: RN -07