2011-06-29_PERMIT FILE - C1981019A (31)

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RULE 4 PERFORMANCE STANDARDS 4.25 OPERATIONS ON PRIME FARMLANDS Since a negative determination of prime farmland was arrived at using the eligibility requirements established for prime farmland under Section 2.04.12, these performance standards do not apply to the present permit application. 4.26 MOUNTAINTOP REMOVAL The South Taylor Mine, although removing the entirety of the X and A seams from the top of the unnamed mountain separating the drainages of Taylor, Wilson, and Good Springs Creeks, Colowyo will be mining deeper coal seams. Based on this information, the CDRMS determined that the South Taylor pit does not meet the criteria for mountaintop removal. 4.27 OPERATIONS ON STEEP SLOPES Prior to the approval of Technical Revision 81 (TR -81), over 18% of the South Taylor pit area was greater than 20 degree slopes, and over 30% of the pit area was greater than 15 degree slopes (Figure 2.06.4 -1). Those areas were identified around most of the perimeter, and scattered isolated locations within the pit. Therefore, an application for a variance from approximate original contour for steep slope mining was appropriate for the South Taylor pit. Colowyo requested this variance in the cover letter to Permit Revision 2 (PR -02). This variance is no longer needed, as a result of the changes to the mine plan in TR -81. Norwest Corporation originally prepared the Post Mine Topography (PMT) for the South Taylor mining area in 2006 based on the Operations on Steep Slopes section of the regulations. The design was based on the mine plan prepared by Marston Mining Engineers & Consultants and the following methodologies were followed: 1. Ridgelines from the original topography would be used to maintain each drainage area. 2. Drainage channels from the original topography would tie into the undisturbed area surrounding the mine. 3. Waste materials would not be placed back into the pit under Approximate Original Contour (AOC); alternatively, the pit would be backfilled and the external waste dumps would be re- contoured. 4. The final PMT was designed with SurvCADD Natural Regrade software to create a more stable land form and drainage system. The configuration of the mining plan will not allow the pit to be backfilled until the end of the mine life. An initial PMT design was based upon conventional methods to generate a PMT surface to maintain the drainage basins using ridgelines from the original topographic map. The final PMT was developed using SurvCADD Natural Regrade. The area was subdivided into eight areas, different drainages, and sub - drainages. The geofluvial design of the channels and drainage basins was established to control the surface water to minimize the effects of erosion and assist in reestablishing vegetation. Cut and fill volumes were modified to reduce the material by lowering the fills and raising the cuts. The final material movement for the South Taylor mining area according to this plan was approximately 114.3 million cubic yards of cut and 115.4 million cubic yards of fill. It included two valley fills near the headwaters of Taylor Creek, one referred to as the East Taylor Fill and the other West Taylor Fill, and a large temporary spoil stockpile needed to develop the mine pit. South Taylor /Lower Wilson — Rule 4, Page 30 Revision Date: 5/31/10 Revision No.: TR -81