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West Elk Mine <br />MCC may install "internal" culverts (i.e., located within the mine site drainage systems) to <br />provide access. If added, the culverts would be sized equivalent to or greater than the next <br />downstream ditch or culvert. <br />Sedimentation Ponds <br />Prior to the disturbance of the area for surface construction at West Elk Mine, four <br />sedimentation ponds and associated collection structures were constructed to effectively retain <br />runoff from the area to be disturbed. The other ponds were developed prior to the use of the <br />old Bear Mine area; construction of the Lower Refuse Pile, formerly referred to as the U.S. <br />Steel laydown area; construction of the Sylvester Gulch Facilities area; and construction of the <br />RPE area. <br />Prior to construction, topsoil was salvaged from all construction areas, stockpiled, and/or <br />applied to slopes and cuts as necessary for reclamation. Exterior slopes of sedimentation <br />ponds at the main mine facilities were reclaimed with a fast growing vegetative cover after <br />they were constructed in order to prevent excessive erosion of the embankments. <br />The cross-section of each sedimentation pond is given in Exhibit 66. Sedimentation pond designs <br />are provided in Exhibit 42, Exhibit 43, Exhibit 44, Exhibit 46, Exhibit 47 and Exhibit 66. An <br />emergency spillway has been provided for each pond, which will safely pass the peak runoff from <br />a precipitation event with a 25-year recurrence interval or larger (100-year for FW-2 (formerly) <br />MB-1 and former pond MB-2R). The RPE pond has been designed to completely contain the <br />runoff from a 100-year, 24-hour storm event. See designs for the RPE pond in Exhibit 70. <br />Small Area Exemptions <br />Small area exemption (SAE) demonstrations for the areas shown on Map 54, Map 54A, and <br />Map 54B are provided in Exhibit 66. Discharges will meet State and Federal water quality <br />requirements. No mixing with underground mine water occurs in these areas. Based on <br />professional judgment, MCC believes that applicable effluent limitations will not be exceeded. <br />Periodically, MCC will review the conditions of best management practices. recommended by <br />the small area exemption demonstrations and assure they are functioning. <br />Design <br />The specific size and capacity of any particular sedimentation pond are presented on Map 54 <br />and Map 54B and are summarized in Exhibit 66. Stability analyses are presented in Exhibit <br />44. Exhibit 45 shows the approval by the Chief of Dam Safety, Division of Water Resources, <br />of Ponds FW-l and FW-2 (formerly pond MB-1). <br />Fresh Water Ponds <br />The design for the fresh water pond FW-1 is shown in Exhibit 43 and in Exhibit 44, Design <br />Report. The fresh water pond FW-I at West Elk Mine is approximately 10 acre-feet in <br />2.45-40 lie t. f(104, 03100,041()6& 05106- PRIO,, 081()9- TV 18, 08104-TR f 19 <br />0