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_P7_ <br />The Regulations contain specific design criteria that must be followed by <br />the operator when designing the system. The criteria ensures that the <br />system, as built, will be capable of treating the runoff to meet EPA <br />effluent limitations. The Division has reviewed the operator's drainage <br />and sediment control plans for compliance with these design criteria. <br />The drainage plans include roadside ditches to collect runoff from haul <br />and access roads and to slope all mine benches so runoff flows to a <br />specific area of the bench. Some of the undisturbed drainage from above <br />the mine will be diverted away from the pit and facilities to prevent <br />mixing with disturbed drainage. This practice greatly reduces the volume <br />of runoff that will be affected by the mine. <br />The sediment control system utilizes both sedimentation ponds and <br />impoundments. Disturbed drainage that collects in these structures will <br />be detained for a length of time sufficient to allow a majority of the <br />solids to settle out. When sufficient settling has occurred the water is <br />released from the structure and returned to the natural receiving stream. <br />Sediment control using ponds and impoundments is utilized for all <br />required areas, except for topsoil piles #1 and #3. These stockpiles <br />were granted an exemption from this requirement in accordance with Rule <br />4.05.2(3). The exemption was granted since the areas are small <br />(approximately 1 acre), and because normal sediment control practices <br />were not considered practical for the site. In lieu of sedimentation <br />ponds the operator proposes to use straw bale filters to trap any <br />sediment before it leaves the site. The stockpiles will also be <br />stabilized with a vegetative cover to reduce erosion from them. <br />The drainage and sediment control system will be maintained on a regular <br />basis. All sedimentation ponds and impoundments will be examined and a <br />report submitted quarterly, in accordance with Rules 4.05.6(11)(c) and <br />4.05.9(10)(b>. <br />Construction of the excess overburden stockpile makes it necessary to realign <br />the ephemeral drainage in Carbon Junction Canyon across the reclaimed mine pit <br />and around much of the permanent overburden stockpile. This permanent <br />diversion would be designed to pass runoff from the 10-year, 24-hour <br />precipitation event as required for ephemeral watersheds draining less than 1 <br />square mine. <br />The applicant has submitted both general and detailed design information as <br />part of the permit application. However, portions of the plan are found in <br />several locations (Appendix D, submitted February 14, 1983; Map 5-4, Final <br />Reclamation Topography, revised May 2, 1983; and Response to Channel <br />Reconstruction Memorandum, received May 24, 1983). Because portions of the <br />plan were submitted at different times during the review process, the plan <br />contains numerous inconsistencies and superseded information. Inconsistencies <br />concerning the use of riprap, channel sizing calculations, and the final <br />