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• permit for the sedimentation ponds are contained in Illustration 13. If not already required by the <br />NPDES permit, suspended solids, total iron, total dissolved solids, pH, and flow rate have been <br />added to the list of parameters to be sampled to meet the requirements of OSM and DMG. The pH <br />of the water is greater than 6.0. However, if the pH falls below 6.0, a neutralizing process will be <br />installed, operated and maintained. Because of infrequent flows, the method used, if required, will <br />be manually operated unless otherwise directed. <br />Sedimentation and drainage control facilities for an area will be maintained and operated until the <br />area has been restored and revegetated and reclamation has been determined successful by the <br />appropriate agency. <br />An exemption was requested from the requirement to maintain and operate Sediment Pond DP-1 <br />until final reclamation and revegetation has been determined successful. It is not possible to leave <br />this pond in place after reclamation of the Scullion Gulch diversion pipe since the pond was <br />constructed on top of the diversion pipe and will be destroyed when the diversion is removed. <br />Sediment control during reclamation of this area is discussed Turther in Section V.B.6. <br />The mine operator will monitor the natural drainage system over and in the immediate vicinity of the <br />underground mine. <br />• Should subsidence occur which affects this natural drainage pattern, the operator will advise the <br />appropriate regulatory agencies who will decide whether or not the disturbance is significant enough <br />to require that a sedimentation and drainage control system be installed. In such a case, the <br />system will adhere to all regulatory requirements. <br />IV.J.4 Life of Mine Diversions Disturbance to natural drainage channels has been avoided <br />wherever possible. However, to provide enough level space without undue terrain disturbance, the <br />grading plan for the "D" Portal Area required rerouting of the main Scullion Gulch drainage channel <br />through a large diameter pipe culvert and of a tributary to Scullion Gulch northwest of the raw coal <br />silo pad through a pipe culvert. The main Scullion Gulch diversion is approximately 2,750 feet long <br />and the tributary diversion is approximately 312 feet long. The Scullion Gulch diversion was <br />designed in accordance with Rule 4.05.4 requirements for permanent diversion of intermittent <br />streams as the stream has watersheds in excess of one square mile. The requirements for <br />permanent diversions were adhered to due to the expected long life of the mine. The diversion of <br />Scullion Gulch at the "D" Portal Area was constructed at the start of grading operations. It will be <br />regularly inspected and maintained during mine operation. Details of the diversion design are <br />presented in the Reclamation Plan. The layout and profile of the diversion is presented in Maps 29, <br />30 and 31. Calculations are included in Illustration 9. Maps 21 and 23 show the drainage areas for <br />this diversion. The existing channel, plan, profile and cross-sections are shown on Maps 36, 37, 38 <br />and 39. The stream diversions at the "D" Portal Area will be removed or buried on site at the end of <br />• Permit Rev. 4 (11/2002) IV-41 <br />