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West Elk Mine <br />inside dimensions of 24 feet in length, 10 feet in width, and 5 feet in depth, and can contain 600 <br />ft.3 of sediment. <br />A system of ditches and culverts has been designed to collect runoff from the 10-year, 24-hour or <br />larger storm event and direct it to the runoff ponds. Although not required by CDMG <br />regulations, most of the haul and access roads located within the main mine facilities area are <br />drained to sedimentation ponds. An exception is the Sylvester Gulch haul/access road; however, <br />best management practices for stormwater treatment will be utilized. Modifications to the <br />original mine pond and ditch system can be found in Exhibit 48 and Exhibit 66. Ditches and <br />culverts associated with the RPE area are contained in Exhibit 70. Ditches and culverts are <br />shown on Maps 54, 54A and 54B. <br />Combined ditch flows are summarized for the system as they progress toward the runoff ponds. <br />Ditch and culvert specifications are listed on Table 44, Exhibit 66. A summary table of inflows <br />and volumes for each pond is presented in Table 42 and in Exhibit 66. <br />The hydrologic parameters for watershed and sub-watershed basins are summarized on Table 43 <br />in Exhibit 66. Documentation of specific parameters such as curve number, rainfall and time of <br />concentration are also found in Exhibit 66. This information for the RPE pond is located in <br />Exhibit 70. <br />Miscellaneous Sediment Control Facilities <br />The railroad loadout facility has been treated independently of the other surface facilities. The <br />loadout is located across the river from the other surface facilities and, therefore, must have its <br />own sediment control. The sediment control is a pond designed (sized) fora 25-year, 24-hour <br />storm event and to accommodate wash-down water from the train load-out facility. Pond MB-4 <br />was relocated in 1998 from the east side of the train load-out to an area west of the load-out <br />between the two sets of tracks. The relocated sediment pond is constructed with concrete and is <br />preceded by an oil skimmer and a sediment trap. The current design detail for this pond can be <br />found in Exhibit 66. <br />The RPE area has also been treated independently of the other surface facilities. The RPE area is <br />located to the east of the lower refuse disposal area and east of Sylvester Gulch. The sediment <br />pond has been designed to completely contain the runoff from a 100-year, 24-hour storm event. <br />The design detail for this pond, the clean water diversion ditches, and sediment ditches can be <br />found in Exhibit 70. <br />DCW-2, the ditch immediately south of the haul road above the Lower Refuse Pile, serves as the <br />clean water diversion ditch for the Lower Refuse Pile. It diverts undisturbed runoff from the <br />Lower Refuse disposal area and is discharged into sediment pond MB-2R. Runoff from the <br />Lower Refuse Pile is conveyed to sediment pond MB-2R via perimeter ditches D2R-1, D2R-1 a, <br />and D2R-3, which are all sized for the 100-year, 24-hour storm event. <br />During construction of the West Elk Mine, a spring was located on the site where the substation <br />was to be built. In order to stabilize the substation pad, a french drain system and collection pipe <br />2.05-31 Revised June 2005 PR10; Rev. January 2006; Rev. March 2006; Rev. Apri12006 PRIG, May 2006 PR70; Rev. January 2009 MR-350 <br />