2019-04-16_REVISION - C1981019 (3)

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RULE 4 PERFORMANCE STANDARDS Rule 4 Performance Standards 4-44 Revision Date: 4/16/19 Revision No.: MR-200 May 12, 1987 the MLRD stated that they were prepared to approve the reduction, which was made effective upon permit renewal. In the 1992 Annual Reclamation Report, Colowyo requested that the swell factor monitoring and analysis requirement be terminated. On August 11, 1993, Colowyo submitted a request for a minor revision to C-81-019 to facilitate the termination of this monitoring. The mining plan, as described in Section 2.05.3, is a soundly designed and engineered open pit mining plan, which 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 limitation remains necessary. 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 initial box cut for the operation was made on the south side of Streeter Draw. The mining operation is designed to progress in a southward direction with shovels/trucks/ proceeding along the entire length of the mining area uncovering the upper coal seams and the draglines uncovering the lower coal seams as shown on the mining range diagram (Map 24). 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 (In the southward progression), 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 obviously 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 Spoil Grading Map (Map 29) by methodically and actively dumping and backfilling overburden in the West and East pits very close to final contour so that minimal work will be needed to complete final re-grade of these areas in the future. All disturbed areas will be returned to the approximate original contour by grading and backfilling with the use of a dragline, trucks, dozers, scrapers and dozers assisting a dragline. 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 premining grades. The outslopes of the completed fill in Streeter Draw and areas backfilled, 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 premining slope grade as shown on the Postmining Topography Map (Map 19). Postmining surface drainage channels will be located to minimize erosion and to minimize slippage. The final pit highwalls will be eliminated in Section 16 by backfilling X seam overburden materials from the West Pit mining area to achieve the final topography. Rehandle of the X seam overburden will be occur concurrently with the advance of the multiple-seam advance during the 2003-2010 period. Also, as mining advances into the final pit, the working area on the pit spoil side will