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Penetration depths at 1,200 feet or less are common. All highwall mining must comply with Rule <br /> 4.23.2. Changes to highwall mining methods is proposed with PR12 for the 2023-2027 permit term. <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 of <br /> the pit. Overburden is then stripped by draglines, scrapers,truck/loader or bulldozers. Finally, front- <br /> end loaders load coal into 90-ton haul trucks,which deliver the raw coal to the Craig Power Plant. <br /> Trapper removed 24.6 million 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 also <br /> placed north of the pit and elsewhere on the site to meet the requirements of the post-mine <br /> topography. The Horse Gulch fill is completed. The only portion of Trapper's operation located <br /> downslope from the Horse Gulch Fill is Trapper's Horse Gulch 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 removes <br /> overburden and interburden, spoil ridges are created by dumping the material from a recently open <br /> pit into a recently mined out pit. Dozers and graders then smooth the spoil ridges and blend the <br /> ridges into the existing topography. <br /> Timing of Backfilling and Grading <br /> The Operator committed to the regulatory requirements of contemporaneous reclamation: that there <br /> will never be more than four ungraded spoil rows(including the active one)at any one time. <br /> Topsoiling and Seeding <br /> After final grading of the spoil ridges,topsoil is placed on the spoil to a depth of 18 inches on <br /> cropland and 12 inches on rangeland. A variation of+/- 2 inches is allowed due to compaction and <br /> operational considerations. Areas are then seeded with one of three main seed mixes, depending on <br /> the elevation. Seed mixes contain various native grasses, forbs and shrubs,while the lowest <br /> elevation site seed mix contains only grasses and forbs. Shrub clumps of approximately 1.6 acres are <br /> also located throughout the reclaimed areas. Seeding occurs by both drill and broadcasting methods. <br /> Long-Term Ash Disposal Plan <br /> The applicant continues to backfill Ashmore pit with ash from the Craig Power Plant. Ash will not be <br /> disposed in Enfield/Derringer pits,as the power plant has reduced its coal consumption, shutting <br /> down one tower,with the closure of the power plant slated for 2028. The ash is approximately 60% <br /> fly ash, 20%bottom ash,and 20% scrubber sludge. A maximum of 5,250 tons per day of the waste <br /> will be disposed of at the Trapper Mine with an average of 1,222 tons per day expected. This is <br /> equivalent to an average annual volume of waste of about 231 acre-feet,after compaction. The <br /> applicant expects this waste burial process will continue for the life of the mine. Down-gradient <br /> ground water monitoring wells are in place to detect any potential degradation of the ground water <br /> due to leachate through the ash waste pile. <br /> 9 <br />