2025-07-30_PERMIT FILE - C1981019 (7)

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RULE 4 PERFORMANCE STANDARDS South Taylor – Rule 4, Page 9 Revision Date: 7/21/25 Revision No.: MR-267 After construction, the South Taylor fills will be monitored quarterly for the following items and reports will be submitted quarterly. Monitoring will continue until such time that Division allows relinquish of quarterly monitoring. 1. The groundwater piezometer well will be established in the West Taylor valley fill (please see Map 10B) and will be monitored quarterly for water level and the other parameters consistent with the present Colowyo groundwater monitor plan. 2. On a quarterly basis, a certified report by a registered engineer will be completed taking into consideration any changes and will note any evidence of surficial slope failure or the formation of springs or seeps on the face of the fill. 4.10 – 4.12 DISPOSAL OF EXCESS SPOIL These sections are addressed in Volume 1. 4.13 CONTEMPORANEOUS RECLAMATION All reclamation efforts, including backfilling, grading, topsoil replacement and revegetation, of land disturbed by the mining activities in the South Taylor pit shall occur as contemporaneously as practicable with mining operations. Colowyo has formally requested a variance for a delay in contemporaneous reclamation in the South Taylor mining area due to the unachievable requirements listed in Rule 4.14.1(1)(d), which the Division has approved. 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 23). 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.