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West Elk Mine <br />main mine facilities were reclaimed with a fast growing vegetative cover afrer they were <br />constructed in order to prevent excessive erosion of the embankments. <br />The crosssection of each sedimentation pond is given in Exhibit 66. Sedimentation pond designs <br />aze 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 a <br />precipitation event with a 25-year recurrence interval or larger (100-year for MB-1 and MB-2R). <br />The RPE pond has been designed to completely contain the runoff from a 100-year, 24-hour storm <br />event. Designs for the RPE pond are located in Exhibit 70. <br />Small Area Ezemntions <br />Small area exemption (SAE) demonstrations for the areas shown on Map 54, Map 54A, and Map <br />54B aze 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 judgement, MCC believes that applicable effluent limitations will not be exceeded. <br />Periodically, MCC will review the conditions of best management practices recommended by the <br />small area exemption demonstrations and assure they aze functioning. <br />Design <br />The specific size and capacity of any particular sedimentation pond are presented on Map 54 and <br />. Map 54B and are summarized in Exhibit 66. Stability analyses are presented in Exhibit 44. <br />Exhibit 45 shows the approval by the Chief of Dam Safety, Division of Water Resources, of <br />Ponds MB-1 and FW-1. Pond MB-2 has been redesigned and replaced by pond MB-2R. <br />Fresh Water Ponds <br />The design for the fresh water pond FW-lis shown in Exhibit 43 and in Exhibit 44, Design <br />Report. The fresh water pond FW-1 at West Elk Mine is approximately 10 acre-feet in capacity. <br />The proposed fresh water pond FW-2 is also about 10 acre-feet in capacity. <br />FW-1 stores water that is pumped from the North Fork of the Gunnison River. FW-1 supplies <br />raw water for potable use, dust suppression, and the fire suppression system. FW-1 was <br />constructed from suitable site materials and is an engineered earth-fill embankment with 3H to <br />1 V sideslopes. The pond is lined with asemi-impermeable clay liner, Pond FW-1 specifications <br />are contained in Exhibit 49. Exhibit 44 contains design considerations and data. <br />FW-2 has not been constructed at this time, and is not planned for this five-year permit term. <br />FW-2 is similar in construction to FW-1. The location of FW-2 is shown in Exhibit 43. The <br />design of FW-2 is contained in Exhibit 44. <br />5 To soil <br />Whenever technically feasible, topsoil and subsoil on sites of proposed surface facilities will be <br />stripped and placed in appropriate stockpiles before any construction occurs. Map 53, Map 53A, <br />and Map 53B show the location of West Elk Mine's topsoil and subsoil stockpiles. These <br />2.05.39 Revised November 2004 PRIG; Rev. March 2006; Rev. Apri11006 PRIO; Rev. May 2006 PRIO <br />