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RULE 4 PERFORMANCE STANDARDS <br />approximate original premining slope grade as shown on the Postmining Topography Map (Map 19). <br />Postmining surface drainage channels will be located to minimize erosion and to minimize slippage. <br />The final pit highwalls will be eliminated in Section 16 by backfilling X seam overburden materials from <br />the West Pit mining area to achieve the final topography. Rehandle of the X seam overburden will be <br />occur concurrently with the advance of the multiple-seam advance during the 2003-2010 period. Also, as <br />mining advances into the final pit, the working area on the pit spoil side will decrease to a point where <br />insufficient spoil room below the proposed postmining contours is available. When that point is reached, <br />material will be temporarily placed above the proposed postmining topography. When the final pass of <br />the West Pit is mined out, this temporarily-placed spoil will be rehandled concurrently with Section 16 <br />virgin and rehandle material to fill and slope the pit to the configuration shown on Map 19 (Postmining <br />Topography). Because the area will be redisturbed by the rehandle activities, that portion of the north end <br />of Section 16 that is above final grade will not be topsoiled or otherwise reclaimed until final reclamation. <br />In addition, Colowyo controls additional coal reserves west and south of Section 9 and 16, outside of <br />Permit C-81-019, that may be considered for future mine expansion. It is possible that the final plans for <br />Section 16 and Section 9 could change to provide for such expansion, with any plan changes being <br />addressed through an appropriate permit revision. <br />4.14.2 General Grading Requirements <br />The final graded slopes at the mining operation will not exceed the approximate original premining slope <br />grade as shown on the Postmining Topography Map (Map 19). Colowyo will retain all overburden and <br />spoil material on solid portions of existing or new benches. The final highwall at the operation will be <br />eliminated by backfilling overburden into the final pit area. <br />Small depressions of a holding capacity slightly greater than one cubic yard of water may be used to <br />create a moist micro climate to aid in shrub establishment. See Section 2.05.4, Planting and Seedings <br />Methods for further information regarding these small depressions. Also, several stock watering ponds <br />will be constructed to compliment the postmining land use. Providing a supply of water is an integral part <br />of the grazing postmining land use. Colowyo will not be mining on any slopes above 20° as shown on the <br />Premining Topography Map (Map 18). <br />Final grading before topsoil placement will be conducted in a manner that minimizes erosion and <br />provides a surface for the topsoil that minimizes slippage. Final grading will be accomplished so that <br />overall grades will not exceed lv:3h. The plan for backfilling and grading is shown graphically on the <br />Spoil Grading Map (Map 29). <br />4.14.3 Covering Coal and Acid and Toxic Forming Materials <br />Colowyo will not have any exposed coal seams remaining at the end of mining and reclamation. Colowyo <br />does not have any acid forming materials at the mine. For discussion on acid- and toxic-forming <br />materials, refer to Section 2.04.6. For disposal of noncoal wastes or materials constituting a fire hazard, <br />refer to Section 4.11.4. <br />4.14.4 Thin Overburden <br />Colowyo does not have a thin overburden situation as explained in Section 4.14.1. <br />Rule 4 Performance Standards 4.14-3 Revision Date: 6/23/08 <br />Revision No.: MR-91