2025-06-30_PERMIT FILE - C1981019A (2)

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RULE 4 PERFORMANCE STANDARDS Collom – Rule 4, Page 17 Revision Date: 4/28/22 Revision No.: TR-154 resulting from settling of fill and topsoil have occurred in a few areas within a year or two after reclamation, but soon stabilize and begin to fill in. The final surface as shown on the Post-mining Topography Map (Map 19C) will approximate the overall pre-mining grades. Appropriate cross sections that show the anticipated final surface configuration of the Collom mining area, in conjunction with the existing pre-mining topography, are shown on the Pre- mining and Post-mining Cross Section (Map 20C). The regrading plan reestablishes escape cover, south facing slopes for wintering big game populations and small drainages suitable as future location of stockponds necessary to achieve the post-mining land use. Revegetation will commence as soon as the topsoil has been redistributed and prepared for seeding as described in Section 2.05.4. The area will be seeded with the seed mixture described in Section 2.05.4 as quickly as possible, typically in the fall of each year following topsoil placement activities. 4.14 BACKFILLING AND GRADING 4.14.1 General Requirements The mining operations of Colowyo will not employ the use of contour mining methods. The original permit demonstrates that Colowyo does not have thin or thick overburden as defined in Subsection 4.14.4 or Subsection 4.14.5. The mining plan, as described in Section 2.05.3, maximizes coal conservation and recovery while minimizing adverse environmental impacts. Because of the mining configuration planned by Colowyo, an exemption from the 180 day or four spoil ridge limitations has been formally requested. The mining plan has been designed as a continuously-moving open pit operation with the mine advancing in the up dip (north to south) direction. The mining operation will progress in a southward direction with shovels/trucks proceeding along the entire length of the mining area (Map 23B). With the numerous benches used in an open pit operation, the mine area will be opened for some time until the equipment comes back to initiate another pass on a designated bench. As the mining operations remove coal seams, the mining area must be left open until such time as the lower-most coal seam can be recovered. With the mining configuration, the time differences between mining the upper-most seam versus the lower-most seam may be greater than 180 days. As the operation advances, backfilling will be as contemporaneous as practical but not so as to interfere with removal of the lower-most coal seam. Colowyo will rough backfill and grade as shown on the Map 29B – Spoil Grading. All disturbed areas may be returned to the appropriate final contour by grading and backfilling with the use of a dragline, trucks, dozers, and scrapers. Additional detail of the backfilling and grading for the mining operation is set forth in the discussion under Sections 2.05.3 and 2.05.4. The area to be mined will be restored to a topography approximating pre-mining grades. The slopes of backfilled areas, as necessary, will utilize contour furrows, surface roughening, and cross ripping for erosion control and stability. Where applicable, Colowyo will retain all overburden and spoil on the solid portion of existing benches. The final graded slopes will not exceed the approximate original pre-mining slope grade as shown on the Map 19C – Post Mining Topography. Post-mining surface drainage channels will be located to minimize erosion and to minimize slippage.