2007-06-29_PERMIT FILE - C1981019A

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The pit in Sections 15 and 16 is a single seam dragline operation, similar to the current operation located in Section 11. To develop the dragline operation, an initial cut was opened near outcrop. A permanent excess spoil fill of approximately 2 million yd3 of excess spoil has been constructed to accommodate the initial cuts. The West Pit is a multiple seam operation utilizing truck/shovel and dragline methods, similar to the current East pit operation. Approximately 45 million yd3 of box cut material will be placed in an external fill (approximately 22 million yd3) north of the box cut excavation or as backfill (approximately 23 million yd3) in the initial pit area. Over 3 million yd3 will be moved from the external fill and backfilled within the pit limits of the East and West Pits. Approximately 19 million yd3 of excess spoil will remain in place as a permanent excess spoil fill, consistent with applicable provisions of Rule 4.09(3). The following describes the mining of the Section 16 Pit Extension which is permitted under TR-65. This area is shown in Figure 2.05-0 "Section 16 Pit Extension." The pit boundaries for the Section 16 Pit Extension were dictated by three features. The first feature that defines the eastern boundary is the cropping of the X seam. The second limiting feature is the current southern mine permit boundary, which is in the process of being modified by the South Taylor permit under Revision PR-02. The third and final feature that defines the area of mining is the 169 KV power line on the west side of the pit as shown on Map 22. Map 23 shows the limits of the Section 16 Pit Extension relative to other activities at the mine. The overall dimensions of the Section 16 Pit Extension are approximately 1,500 feet by 1,200 feet. The Section 16 Pit Extension occurs in a number of cuts. The typical width of the cut • will be around 240 feet wide. This pit is excavated using either a shovel or excavator. Mining dimensions will follow the established ground control plan and will be generally similar to operations in the west pit. The depth of the pit varies, with the highest cut depths in the south west side of the pit averaging about 100 feet. Proceeding eastward, the cover decreases until it intersects with the X seam outcrop. The X Seam is the only seam in the Section 16 Pit Extension that Colowyo will be mining. The X Seam coal is approximately 11 feet thick, tapering in thickness to the east were the X coal is outcropped. The X coal is dipping down gradient from the northwest to the southeast. The northern portion of the proposed Section 16 Pit Extension was stripped of topsoil prior to and during 2001. Additional topsoil stripping of an estimated 108,000 cubic yards is needed. This estimate is based on the soil units presented on Map SB and the average estimated soil salvage depths presented on Table 2.04.9-6 (Volume 12). Stripped topsoil is hauled to Topsoil Stockpile 16D as shown on Map 28. Haulage is along the top of the regraded spoil immediately west of the western boundary of Section 16 reclamation. The Section 16 Pond Ditch is extended westward along the contour to collect the disturbed area runoff from the pit and direct flows the Section 16 Pond as shown on Map 12. Exhibit 7, Item 140 contains SEDCAD modeling demonstrating the adequacy of the pond to handle these flows. Eventually, the Section 16 Pit Extension limits may be expanded westward to the cropline and southward beyond the permit boundary following appropriate permitting activities. Mining in the area is expected to take approximately two to three years and may be dictated by blending and coal quality considerations. The existing pit limits are centrally located within the South Taylor mine plan permitted under PR-02. The underlying coal seams beneath the X seam will subsequently be mined during the 2011 to 2013 time frame as 2.05-36 Revision Date: 5/25/07 Revision No.: TR-65