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<br /> <br /> <br /> 29 C1981-041 RN7 findings <br />maintenance (4.05.4(2)(a)). <br /> <br />4. In addition to the permanent diversions mentioned above, a permanent diversion of <br />an ephemeral stream draining less than one square mile has been approved for an <br />unnamed ephemeral tributary to the Colorado River located within the 2 West Portal <br />Disturbance Area. The outside bank closest to the North Portal was built up to prevent <br />the diverted stream from entering the portal. Bedrock lies close to the bottom of the <br />diverted channel and the channel does not require armoring. This decision is based on <br />a finding that the proposed diversion meets the requirements of 4.05.l8 and 4.05.4, <br />applicable local, State, and Federal statutes and regulations and that the diversion is <br />designed to safeguard public safety and to minimize adverse impacts to the hydrologic <br />balance (4.05.4(1) and (4)). <br /> <br />D. Sedimentation Ponds <br /> <br />Information on the surface water sediment control system can be found in Volume 3, <br />Tab 13, page 13-5 of the permit application. A list of sediment control structures, <br />along with references to appropriate exhibits for designs and cross sections, are found <br />in Table 13-4 of the application. Calculations used to design these structures are given <br />in appendix 13-2 of the permit application. <br />During operations a total of 12 sediment ponds were designed and built and treated <br />disturbed-area surface water runoff under the existing permit for the Roadside Mines. <br />All of the twelve ponds have been fully reclaimed. References to designs for these <br />ponds and their locations are found in Tables 13-5 and 13-6 of the permit application. <br /> <br />With the exception of approved small area exemptions, all surface runoff from <br />disturbed areas was routed through a sediment pond. All but two sediment ponds <br />were designed to contain the runoff and sediment from a 10-year, 24-hour <br />precipitation event. Sediment Ponds #1 and #2 were combined to contain the 25-year, <br />24-hour storm event. Sediment ponds #1, #2, #7, #8 and #11 required pumps as the <br />principal dewatering mechanism because the surrounding ground elevations were <br />higher than the sediment pond bottom elevations. The emergency spillways were <br />designed to pass the 25-year, 24-hour peak flow. The outflow below the spillway was <br />armored with riprap where necessary to control erosion. <br /> <br />Sediment Pond #3 was never constructed. All ponds have been reclaimed and have <br />received bond release approval. <br /> <br />E. Acid-forming and Toxic-forming Spoil <br /> <br /> The Division has determined that the mine will not produce toxic or acid-forming <br />spoil. <br /> <br />F. Impoundments <br /> <br />The only impoundments utilized within the permit area in addition to sediment ponds