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Once the overburden is sufficiently fragmented to allow for efficient removal and loading, <br />overburden removal will commence. The location of the area to be mined is shown on the Mine <br />Plan Map 23. <br />Colowyo utilizes two distinct methods of overburden removal in the mining operation: (1) <br />truck/shovel techniques and (2) dragline technique. By combining the use of both shovel and <br />trucks, and draglines, Colowyo can both efficiently and economically handle. the logistics <br />involved in a multiseam, open pit coal mine. <br />The truck/shovel operation was used to open up the initial boxcut, and now is generally utilized <br />in removing overburden over the upper coal seams, Y3, Y2, X, A2, and portions of B and 82. <br />From time to time, based on production requirements, truck/shovel or loader/truck methods <br />may be utilized to assist the dragline operation in the lower seams. <br />The initial mining operatioris at Colowyo began along the southern face of Streeter Draw. The <br />box cut extended into the upper reaches of the draw. Mining has proceeded south from the <br />initial excavation. Box cut overburden material was placed into the Streeter Fill as shown on the <br />Existing Structures -South Map 228 and the 2001 Annual Report Map, and as discussed in <br />Section 2.06.2. <br />The overburden material is removed in a series of lifts or benches; the height of these benches <br />will be influenced by the distance between the coal seams to be mined (see Mining Range <br />Diagrams Map 24), and the equipment mining those benches. <br />Overburden removal by the, truck/shovel method progresses on approximately 170-240 foot <br />wide benches with a maximum highwall height of about 60 feet. Electric shovels or front-end <br />loaders load this overburden into 50, 170, 190 or 240-ton trucks. The trucks then haul the <br />overburden around the active coal pit and dump this material into the mined-out area. The <br />truck/shovel operation will always precede the dragline operation in the multiple seam pits. <br />2.05-6 <br />June 18, 2002 <br />MR-57 <br />CF 4.1.1.3. <br />