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AAGAPITO ASSOCIATES, INC. <br />Mining & Civil Engineers & Geologists <br />715 HORIZON DR., STE 340 <br />GRAND JUNCTION, CO 81506 <br />USA <br />VOICE 970.242.4220 <br />www.agapito.com <br />May 31, 2012 <br />Daniel I. Hernandez <br />Senior Environmental Protection Specialist <br />Colorado Division of Reclamation, Mining and Safety <br />1313 Sherman St., Room 215 <br />Denver, CO 80203 <br />GOLDEN OFFICE <br />303.271.3750 <br />723 -01 T3 <br />Re: New Elk Mine (Permit No C- 1981 -012) <br />Addendum to Exhibit 43 of Technical Revision Application No. 65 (TR 65) <br />DWDA 0— Historical Mine Facility Structure Mitigation <br />Dear Mr. Hernandez, <br />The proposed West Portal development waste storage area (DWDA) referred to as <br />DWDA #3 is located over a historical mine facility structure identified as a rope or rail slope. <br />Agapito Associates, Inc. (AAI) has reviewed the location of the rail slope in relation to the <br />proposed DWDA embankment and has prepared a recommended mitigation strategy. This letter <br />summarizes recommended mitigation procedures and DWDA foundation preparation methods. <br />This letter should be considered an addendum to Exhibit 421 that is included with the Technical <br />Revision No. 65. <br />BACKGROUND <br />The historical mine facility structure (structure) refered to as a rope / rail slope (slope) <br />consists of a three -sided structure (side walls and roof) constructed of reinforced concrete. The <br />structure measures approximately 8 feet (ft) by 12 ft by 200 ft in length and declines from the <br />ground surface at approximately 17 degrees. The structure opening is oriented approximately <br />north 90 degrees east. Based on the proposed DWDA configuration, approximately 150 ft of the <br />western portion of the structure would be overlain by waste rock. The portal of the slope is at an <br />elevation of approximately 7,648 ft. The proposed waste rock embankment will be at an <br />elevation of approximately of 7,692 ft; therefore, approximately 44 ft of waste rock will overly <br />the facility structure. <br />The structure was built to prevent caving and provide safe access into and out of the <br />historical mine area near the ground surface. Inby of the eastern extent of the concrete structure, <br />the historical mine opening is caved and has been ever since the New Elk Coal Company <br />Agapito Associates, Inc., (2012), "Design Recommendations for the Proposed West Portal Development Waste <br />Rock Disposal Area (DWDA)," New Elk Mine, Weston, Colorado, April 16. <br />GEOENGINEERING • MINING ENGINEERING • CIVIL ENGINEERING <br />