2008-01-16_APPLICATION CORRESPONDENCE - C2008086 (3)

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DRAFT Within the Coal Lease Application area the Cameo Seam outcrop crosses the intermittent stream course in Buniger Canyon approximately 4,500 feet upstream from where it meets the permanent stream in Big Salt Wash. In order to mitigate potential subsidence impacts in the Coal Lease Application area and the immediately adjacent north, east and south parts of the Project Area, it was necessary to have a conceptual mining plan. The goals of the conceptual plan were to maximize safety, then mitigate to the extent possible subsidence impacts and finally to maximize resource recovery. The proposed portal is the anchor for the concept. The conceptual plan that follows involves at least two sets of east-west mains driven off the Big Salt Wash mains. A bleeder entry may well be necessary along the south boundary of the Project Area. Either a bleeder entry or a third set of mains would probably be required along the northern boundary of the Project Area. It will be necessary to drive the main access entries approximately 5,000 feet N 45° E from the planned Red Cliff Mine portal to where it will cross under the overlying intermittent stream course in Stove Canyon at a depth of less than 200 feet., The main entries will probably continue to a distance of approximately 9,000 feet where it will cross beneath the intermittent stream course in Buniger Canyon at a depth of slightly less than 500 feet, still within the Existing Coal Lease area. The N 45° E direction of the Red Cliff Mine main entries indicates that the Main entries will probably turn half-right after passing under Buniger Canyon to drive east just south of the boundary between T. 7 S. and T. 8 S. Driving the .mains in this direction would reach Big Salt Wash in approximately 8,200 feet at a depth of approximately 200 feet. It is anticipated that the main entries will split at Big Salt Wash with one branch continuing to the east, the 1st East Mains, and the other driven to the northeast under Big Salt Wash, the Northeast Mains. The East Mains would be the base for developing longwall panels as much as 14,000 feet to the south. If no longwall panels are driven to the north it could be possible to rob the barrier and main entry pillars on the retreat provided the retreat mining was protected by unmined coal on the north side of the 1st East Mains. This assumes that the individual longwall panels driven south off the 2nd East Mains are mined after the 2nd West Mains and that the 2nd East Mains longwall panels are sequenced from east to west and retreated from south to north following the retreat of the 1st East Mains pillars. Retreat mining the 2nd West Mains and the 2nd East Mains would probably require a third set of main entries driven from the East Salt Creek or Munger Creek and across the north end of the Project Area. Mining beneath the permanent and intermittent stream courses will necessitate preventing water loss to the underlying workings. As discussed previously in section 6.1.2 Fractured Zone, water loss to the fracture zone is probable through 100 feet or less of overburden when longwall mining in the Red Cliff Mine Project Area. Big Salt Wash is particularly at risk because it also contains a road and is has agricultural uses. Because there is no available depth of alluvium below any of the deeply incised canyons and the absence of any data on the potential fault control of the nearly trellis drainage pattern in the Project Area, conservatism must be used and a minimum of 200 feet of overburden required to positively prevent water loss from longwall mining under even intermittent stream courses. If ranch animals are pastured at higher elevations in the Project Area, open fractures of more than 2 inches in width could potentially cause injury to range animals, which means 1500 feet of cover potentially could be required in areas with little or no alluvial cover for the planned 11-foot longwall mining height. Table 10. Predicted Surface Fracture Widths Based on York Canyon Mine provides conservative estimates of fracture widths with respect to depth of overburden and panel width. Page 43 of 57