2016-08-08_GENERAL DOCUMENTS - C1981019

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PR-04, Colowyo Coal Mine C1981-019 46 August 2016 Topsoil will be removed during the late spring to fall, ahead of pit advance. Vegetation, with the exception of large trees, will be removed and redistributed with the topsoil. Topsoil will be removed to topsoil stockpiles or, where possible, applied directly to regraded spoil. Within the Collom permit expansion area, most topsoil will be placed in stockpiles, as the nature of the operation will generally not allow for direct replacement. Table 2.04.9-16 in Volume 15 documents the topsoil mass balance for the Collom permit expansion area. C. Topsoil Redistribution Topsoil redistribution for the original permit area (as well as general procedures applicable to the South Taylor expansion) is described in the original PAP (Section 2.05 and 4.06). Topsoil redistribution for the South Taylor expansion area is more specifically addressed in Sections 2.05.3(5), 2.05.4(2)(d), and 4.06 of Volume 12. Topsoil redistribution for the Collom permit expansion area is found in Section 2.05.4(2)(d) of Volume 15. Regraded spoils will be scarified by dozers, where necessary, before replacement of topsoil. Where necessary, a drainage control bench or furrow will be constructed on spoils slopes of 3:1 (horizontal to vertical). Topsoil will then be applied in a rough condition and contour furrowed to minimize erosion. For most of the mine life at Colowyo, the required average, uniform soil replacement thickness was 18 inches, although a 12 inch average, uniform replacement thickness was specified for Section 11. With approval of TR62 (May 29, 2006), the Division approved a topsoil replacement depth of eight inches for lands reclaimed after March 2006. Technical Revision No. 82, approved June 25, 2010, approved variable topsoil replacement depths for areas reclaimed in South Taylor, East Pit, and West pit after June 2010. Post-mining slopes and plant community goals determine the soil replacement depths. The areas approved for variable topsoil replacement are shown on Maps 28, 28B, and 28C. The Collom permit expansion area will utilize variable topsoil replacement depths. Slopes greater than 10 percent will have variable topsoil depths from 6 inches at the top of the slope, increasing to 3 to 4 feet at the bottom of the slope. Armored channels will not have any topsoil applied. Slopes greater than 10 percent will be seeded with the grassland seed mix. Slopes gentler than 10 percent will have 0-6 inches of topsoil replaced. The shallower topsoiled areas will be planted to the Sagebrush steppe seed mix.