2020-03-24_PERMIT FILE - C1981019A (38)

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RULE 4 PERFORMANCE STANDARDS 461400$01741.0041100ftikReVerWttlf4fP'4$14r 5', k 4,t,,,t ,p1C hL',o, b•• ��'M!.c'aec;mb'�T' fi'a�� :d t+A„'ktdc 040444 4.14 BACKFILLING AND GRADING 4.14.1 General Requirements The mining operations of Colowyo will not employ the use of contour mining methods. 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 multi-seam mining configuration planned by Colowyo, an exemption from the 180 day or four spoil ridge limitations has been formally requested and granted by the Division. The mining plan has been designed as a continuously-moving open pit operation with the mine advancing approximately parallel to the dip of the numerous coal seams. The mining operation is an extension of the existing Section 16 mine operation, and will progress in a southward direction with shovels/trucks/proceeding along the entire length of the mining area(Map 23A). 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 will 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 29. All disturbed areas will 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 terraces and/or contour furrows for erosion control and stability. These terraces and contour furrows will be constructed according to the requirements outlined in Section 2.06.2. 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 19B. Post-mining surface drainage channels will be located to minimize erosion and to minimize slippage. 4.14.2 General Grading Requirements The final graded slopes at the mining operation will not exceed the approximate original pre-mining slope grade as shown on Map 19B. Colowyo will retain all overburden and spoil material on solid portions of existing or new benches. The final highwall at the operation will be eliminated by backfilling overburden into the final pit area. Small depressions of a holding capacity slightly greater than one cubic yard of water may be used to create a moist micro climate to aid in shrub establishment. See Section 2.05.4, Planting and Seeding Methods for further information regarding these small depressions. Also, several stock watering ponds will be constructed to compliment the post-mining land use. Providing a supply of water is an integral part of the grazing post- mining land use. Colowyo will not be mining on any slopes above 20°as shown on Map 18A. Final grading before topsoil placement will be conducted in a manner that minimizes erosion and provides a surface for the topsoil that minimizes slippage. Final grading will be accomplished so that overall grades will not exceed lv:3h. The plan for backfilling and grading is shown graphically on the Map 29. South Taylor/Lower Wilson—Rule 4,Page 10 Revision Date: 12/20/19 Revision No.: TR-135