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RULE 4 PERFORMANCE STANDARDS <br />Exceptions include such areas as topsoil stockpiles located outside of the Section 11 ditch (MR-15), <br />topsoil stockpiles located along the paved haul road (MR-18), East Taylor holding pond and pump station <br />(TR approved on November 1984), raw and potable water lines, and railroad loop. Erosion and sediment <br />control is achieved by protection with vegetation or rock. The demonstration presented in MR-18 <br />provides a representative example of how vegetative cover can provide for sediment control. <br />The Administration and Security buildings have associated paved parking areas which generate no <br />sediment. <br />Colowyo employs various methods to manage water which periodically collects internal to the mining <br />operation and does not reach sedimentation ponds. various sumps, ditches, pumps, hoses and pipes, etc. <br />will be employed to control water within pits and/or route water between pits. The ultimate destination of <br />such water will be for operation's use (dust control, etc.), evaporation or seepage into the backfilled spoil <br />areas. <br />In addition to the mining, reclamation and treatment methods described and referenced in this Section, <br />further protection of the hydrologic balance will be established by an on-going plan for monitoring <br />potential changes in surface water quality and quantity and groundwater quality. This monitoring plan is <br />described under Section 4.0-5.13 and the monitoring locations are graphically shown on Water <br />Monitoring Sites for Permit No. CO-019-81 (Map 37). Excess spoil valley fill areas are located downdip <br />of mining and reclamation areas and periodic monitoring for seeps and springs and periodic monitoring of <br />piezometer wells will detect the formation of spoil springs. <br />4.05.2 Water Quality Standards and Effluent Limitations <br />The plan for protection and control of drainage and sediment described in 2.05.6 provides that surface <br />drainage from the disturbed area within the permit area will be passed through sedimentation control <br />structures. All ponds will be constructed and maintained to contain or treat the volume design for a 10- <br />year, 24-hour precipitation event. The accumulation of sediment in the ponds will be monitored quarterly. <br />In addition, grab samples of water, as required, will be collected from pond discharges to measure the <br />effectiveness in meeting the applicable Colorado and Federal water quality standards. <br />The proposed sedimentation ponds have been designed and will be constructed and maintained to <br />effectively trap sediment from runoff resulting from precipitation events up to and including the 10-year, <br />24-hour precipitation event. <br />Drainage from the mining area, after treatment in sedimentation ponds, is not anticipated to exceed the <br />effluent limitations of any federal or Colorado agency requirements. Baseline groundwater quality is <br />discussed in Section 2.04.7. No acid mine drainage of pH equal to or less than 6.0 is expected. For further <br />details relating to the sediment pond discharges, refer to the NPDES reports found in the 1983- through <br />1990 Annual Reports. <br />Historically, Colowyo has experienced no pH problems with water. discharges sampled in the vicinity of <br />the Colowyo operations. As reported in Section 2.04.7, all pH values of water samples taken in the <br />vicinity of the Colowyo Operations have ranged between 7.2 and 8.5; therefore, it is anticipated that no <br />acid mine drainage will occur as the operations move southward. <br />Rule 4 Performance Standards 4.05-2 Revision Date: 6/23/08 <br />Revision No.: MR-91