2009-05-26_PERMIT FILE - C1980007A

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West Elk Mine Locations of culverts are shown on Map 54, Map 54A, and Map 54B. Details and the culvert specifications are found in Exhibit 66. Details and culvert specifications for the ditches and culverts at the RPE area are found in Exhibit 70 and Exhibit 66. MCC may install "internal" culverts (i.e., located within the mine site drainage systems) to provide access. If added, the culverts would be sized equivalent to or greater than the next downstream ditch or culvert. Sedimentation Ponds Prior to the disturbance of the area for surface construction at West Elk Mine, four sedimentation ponds and associated collection structures were constructed to effectively retain runoff from the area to be disturbed. The other ponds were developed prior to the use of the old Bear Mine area; construction of the Lower Refuse Pile, formerly referred to as the U.S. Steel laydown area; construction of the Sylvester Gulch Facilities area; and construction of the RPE area. Prior to construction, topsoil was salvaged from all construction areas, stockpiled, and/or applied to slopes and cuts as necessary for reclamation. Exterior slopes of sedimentation ponds at the main mine facilities were reclaimed with a fast growing vegetative cover after they were constructed in order to prevent excessive erosion of the embankments. The crosssection of each sedimentation pond is given in Exhibit 66. Sedimentation pond designs are provided in Exhibit 42, Exhibit 43, Exhibit 44, Exhibit 46, Exhibit 47 and Exhibit 66. An emergency spillway has been provided for each pond, which will safely pass the peak runoff from a precipitation event with a 25-year recurrence interval or larger (100-year for MB-1 and MB- 2R). The RPE pond has been designed to completely contain the runoff from a 100-year, 24- hour storm event. Designs for the RPE pond are located in Exhibit 70. Small Area Exemptions Small area exemption (SAE) demonstrations for the areas shown on Map 54, Map 54A, and Map 54B are provided in Exhibit 66. Discharges will meet State and Federal water quality requirements. No mixing with underground mine water occurs in these areas. Based on professional judgement, MCC believes that applicable effluent limitations will not be exceeded. Periodically, MCC will review the conditions of best management practices recommended by the small area exemption demonstrations and assure they are functioning. Design The specific size and capacity of any particular sedimentation pond are presented on Map 54 and Map 54B and are summarized in Exhibit 66. Stability analyses are presented in Exhibit 44. Exhibit 45 shows the approval by the Chief of Dam Safety, Division of Water Resources, of Ponds MB-1 and FW-1. Pond MB-2 has been redesigned and replaced by pond MB-2R. 2.05-40 Revised November 2004 PRIG; Rev. March 2006; Rev. April 2006 PRIO; Rev. May 2006 PR10; Rev. January 2009 MR-350