Laserfiche WebLink
• 4.06.2 Water Ouality Standards and Effluent Limitations <br />The plan for protection and control of drainage and sediment described in 2.05.6 provides <br />that surface drainage from the disturbed area within the permit area will be passed through <br />sedimentation control structures. All ponds will be constructed and maintained to contain or <br />treat the volume design for a l0-year, 24-hour precipitation event. The accumulation of <br />sediment in the ponds will be monitored quarterly. [n addition, grab samples of water, as <br />required, will be collected from pond discharges to measure the effectiveness in meeting the <br />applicable Colorado and Federal water quality standards, <br />The proposed sedimentation ponds have been designed and will be constructed and <br />maintained to effectively trap sediment from runoff resulting from precipitation events up to <br />and including the ] 0-year, 24-hour precipitation event. <br />Drainage from the mining area, after treatment in sedimentation ponds, is not anticipated to <br />exceed the effluent limitations of any federal or Colorado agency requirements. Baseline <br />groundwater quality is discussed in Section 2.04.7. No acid mine drainage of pH equal to or <br />less than 6.0 is expected. For further details relating to the sediment pond discharges, refer to <br />the NPDES reports found in the 1983- through 1990 Annual Reports. <br />Historically, Colowyo has experienced no pH problems with water. discharges sampled in the <br />vicinity of the Colowyo operations. As reported in Section 2.04.7, all pH values of water <br />samples taken in the vicinity of the Colowyo Operations have ranged between 7.2 and 8.5; <br />• therefore, it is anticipated that no acid mine drainage will occur as the operations move <br />southward. <br />4.05.3 Diversions and Conveyance of Overland Flow and Shallow Groundwater Flow and <br />Ephemeral Streams Draining a Watershed Less than One Square Mile <br />The drainage and sediment control plan described under Section 2.05.6 provides for <br />temporary diversion of surface drainages within the permit area. A system of temporary <br />ditches, as shown on the Hydrology -South Map (Map 12) and the Hydrology -North Map <br />(Map <br /> <br />4.05-3 Revision Date: 1/96 <br />Revision No.: MR-36 <br />