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RULE 2 PERMITS <br />Collom Gulch, and the West Fork of Jubb Creek may be directly affected by mining operations. The <br />remainder of the Jubb Creek drainage, along with Taylor and Wilson Creeks, may be slightly affected by <br />power line, haul road construction, but will not be mined. Groundwater resources within the "general <br />area" are delineated by these major basins and are a function of the stratigraphy and local climate <br />conditions. <br />Both the "permit area" and the "adjacent area", as defined by Rule 1.04, lie within the "general area" as <br />described above. <br />The geological information for the "permit area" and the "general area" are discussed and described in <br />detail in Section 2.04.6. Groundwater information for the general area, adjacent area, and permit area is <br />set forth in Section 2.04.7. <br />2.04.6 Geology Description <br />The coal to be mined in the Collom permit expansion area is located in the northern extent of the <br />Danforth Hills coal field of the Uinta Region. The Danforth Hills coal field comprises the coal deposits <br />on the northeast flank of the Piceance Creek basin and is bordered on the northeast by the Axial Basin <br />Anticline. Map 7A presents a regional geologic map showing bedrock outcrops and structural features in <br />the general area. <br />The Cretaceous Williams Fork Formation contains the mineable coals in the Collom permit expansion <br />area. The coal deposit is contained within approximately 77 seams or seam splits with up to 27 seams <br />planned for mining. The general stratigraphy within the Collom permit expansion area is shown in <br />Exhibit 6, Item 7 (Collom Area Geology Pre -Feasibility Report), Figure 3.1, and Exhibit 6, Item 8 <br />(Addendum to the Pre -Feasibility Report). The stratigraphy is also represented on five cross sections <br />presented as Figures 2.04.6 Sheets 1 and 2. A key to the location of the geologic cross sections are shown <br />on Map 7A. <br />Coal seams Y25 through Gb will be mined in the Collom Pit. The thicknesses of the seams vary in the <br />Collom permit expansion area with seam thickness of 5 feet to 11 feet common. <br />The coal to be mined has a high BTU value of 10,000 to 11,000 BTU per pound, low sulfur, and low ash <br />content. There exists a market for this coal, in part because of its ideal qualities. The analyses of the coal <br />seams to be mined are considered confidential and are provided in the original permit application and will <br />be provided to the Division under separate cover. <br />Stratigraphy <br />The Collom permit expansion area is underlain by as much as 13,500 feet of sedimentary rock consisting <br />of approximately 4,500 feet of Paleozoic quartzite, limestone, shale, sandstone, and gypsum; and 9,000 <br />feet of Mesozoic limestone, shale, mudstone, sandstone, and conglomerate (Hallgarth, 1959). The coal <br />seams mined at the Colowyo operation are of Upper Cretaceous Age. <br />The generalized geological setting is shown on Map 7A. The stratigraphic positions of the coals mined <br />by Colowyo are illustrated on Figures 2.04.6-5 Sheets 1 through 2. <br />The surficial geologic formations within the area are the Upper Cretaceous Mancos Shale, which is <br />overlain by the upper Cretaceous Mesaverde Group. The Mesaverde Group is comprised of the Iles <br />Formation and Williams Fork Formation. Details of each formation are described below. <br />Collom — Rule 2, Page 12 Revision Date: 4/7/17 <br />Revision No.: RN -07 <br />