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Auger/Higwall Mining <br /> Auger or"highwall mining"is conducted in the end walls of the I, J, L and N pits. The pits are <br /> developed in sections from west to east with contemporaneous backfilling minimizing the out-of-pit <br /> spoil placement. An HW N800 Addcar System is utilized. A launch vehicle platform, sitting on the <br /> boxcut floor controls the systems functions, rigid conveyor cars each fitted with a belt conveyor are <br /> fed by a remote controlled underground continuous miner. Real Time feedback to the outside <br /> operator from video cameras and a HORTS guidance system provides three dimensional locations. <br /> Gamma sensors in the cutting head provide the ability to sense roof and floor rock to maintain the <br /> miner in the coal seam. Auger depth of penetration and coal recovery vary depending on coal seam <br /> splitting, thinning or pinching, coal quality, roof and floor integrity, and machine limitations. <br /> Penetration depths at 1,200 feet or less were common. All highwall mining complies with Rule <br /> 4.23.2. <br /> Removal of Topsoil and Overburden <br /> Prior to disturbance, and in advance of pit construction, vegetation is cleared and topsoil is removed <br /> and salvaged. Stockpiled soils are shaped and seeded to establish vegetation for protection from <br /> wind and water erosion. After topsoil removal, the overburden is drilled and blasted in advance <br /> of the pit. Overburden is then stripped by draglines, scrapers, truck/loader or bulldozers. Finally, <br /> front-end loaders load coal into 90-ton haul trucks, which deliver the raw coal to the Craig Power <br /> Plant. <br /> Trapper removed 24.6 billion cubic yards (BCY), of spoil material in the K-Pit and placed the <br /> material in a permanent fill that is known as Horse Gulch Fill. Additional spoil from the K-Pit is <br /> also placed north of the pit and elsewhere on the site to meet the requirements of the post-mine <br /> topography. As of this permit renewal RN7, the Horse Gulch fill is completed. The only portion of <br /> Trapper's operation located downslope from the Horse Gulch Fill is Trapper's Horse Gulch <br /> sediment control pond. <br /> Backfilling of Pits <br /> After removing coal from economically recoverable coal seams, associated pits are backfilled with <br /> spoil (overburden and interburden) and then graded by dragline and dozers. As a dragline <br /> removes overburden and interburden, spoil ridges are created by dumping the material from a <br /> recently open pit into a recently mined out pit. Dozers and graders then smooth the spoil ridges <br /> and blend the ridges into the existing topography. <br /> Timing of Backfilling and Grading <br /> The Operator committed to the regulatory requirements of contemporaneous reclamation: that <br /> there will never be more than four ungraded spoil rows (including the active one) at any one <br /> time. <br /> Topsoiling and Seeding <br /> After final grading of spoil ridges, topsoil is placed to an 18 inch depth for lands reclaimed to <br /> cropland and 12 inches on rangeland and wildlife habitat. A variation of plus or minus 2 inches is <br /> allowed for compaction and operational considerations. Areas are then seeded with one of three <br /> primary seed mixes, depending on site elevation. Seed mixes comprise various native grasses, forbs <br /> and shrubs, while grasses and forbs make up the seed mixes for the lower elevations of the site. <br /> Shrub clumps of approximately 1.6 acres have been placed throughout the reclaimed areas in the <br /> 10 <br />