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RULE 4 PERFORMANCE STANDARDS <br />• 4.25 OPERATIONS ON PRIME FARMLANDS <br />Since a negative determination of prime farmland was amved at using the eligibility requirements <br />established for prime farmland under Section 2.04.12, these performance standards do not apply to the <br />present permit application. <br />4.26 MOUNTAINTOP REMOVAL <br />The South Taylor Mine, although removing the entirety of the X and A seams from the top of the <br />unnamed mountain sepazating the drainages of Taylor, Wilson, and Good Springs Creeks, Colowyo will <br />be mining deeper coal seams. Based on this information, the CDMG determined that the South Taylor pit <br />does not meet the criteria for mountaintop removal. <br />4.27 OPERATIONS ON STEEP SLOPES <br />Over 18% of the South Taylor pit area is greater than 20 degree slopes, and over 30% of the pit area is <br />greater than 15 degree slopes (Figure 2.06.4-I ). These azeas aze azound most of the perimeter and <br />scattered isolated locations within the pit. Therefore, the application for a variance from approximate <br />original contour for steep slope mining is appropriate for the South Taylor pit. Colowyo has requested <br />this variance in the cover letter to this permit revision. <br />Norwest Corporation prepared the Post Mine Topography (PMT) for the South Taylor mining area based <br />on the Operations on Steep Slopes section of the regulations. The design was based on the mine plan <br />prepared by Marston Mining Engineers & Consultants and the following methodologies were followed: <br />• 1. Ridgelines from the original topography will be used to maintain each drainage area. <br />2. Drainage channels from the original topography will be used to tie into the undisturbed area <br />surrounding the mine. <br />3. Waste materials will not be placed back into the pit under Approximate Original Contour <br />(AOC); alternatively, the pit will be backfilled and the external waste dumps will be re- <br />contoured. <br />4. The final PMT was designed with SurvCADD Natural Regrade software to create a more <br />stable land form and drainage system. <br />The configuration of the mining plan will not allow the pit to be backfilled until the end of the mine life. <br />An initial PMT design was based upon conventional methods to generate a PMT surface to maintain the <br />drainage basins using ridgelines from the original topographic map. The final PMT was developed using <br />SurvCADD Natural Regrade. The area was subdivided into eight areas, different drainages, and sub- <br />drainages. The geofluvial design of the channels and drainage basins will control the surface water to <br />minimize the effects of erosion and assist in reestablishing vegetation. Cut and fill volumes were <br />modified to reduce the material by lowering the fills and raising the cuts. The final material movement <br />for the South Taylor mining area is approximately 114.3 million cubic yards of cut and 115.4 million <br />cubic yards of fill. <br />n <br />U <br />South Taylor/Lower Wilson- Rule 4, Page 30 Revision Date: 3/30/07 <br />Revision No.: PR-02 <br />