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RULE 2 PERMITS <br /> <br />South Taylor – Rule 2, Page 9 Revision Date: 7/21/25 <br /> Revision No.: MR-267 <br />The "general area" with respect to hydrology is defined by Rule 1.04, as that topographic basin that <br />surrounds the area to be mined during the life of the operation. This area includes several watersheds and <br />groundwater systems, which will allow assessment of the probable cumulative impacts of the quantity and <br />quality of the surface and groundwater systems. Specifically, the "general area" includes the drainages of <br />Good Spring Creek and Wilson Creek, perennial streams; and Taylor Creek, an intermittent stream. <br /> <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 /> <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 /> <br />2.04.6 Geology Description <br /> <br />The coal to be mined in the permit area is located in the northern extent of the Danforth Hills coalfield of <br />the Uinta Region. The Danforth Hills coal field comprises the coal deposits on the northeast flank of the <br />Piceance Creek basin and is bordered on the northeast by the Axial Basin Anticline. <br /> <br />The general stratigraphy within the permit revision area is shown on Figure 2.04.6-3B and is graphically <br />shown on figures 2.04.6-4A through 2.04.6-4F. The locations of the geologic cross sections are shown on <br />Map 7A. <br /> <br />Coal seams X and A through G789 will be mined in the South Taylor area. The thicknesses of these seams <br />are shown on figures 2.04.6-3B. <br /> <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. It is in generally discreet seams of mineable thickness. There exists a market for this coal, in <br />part because of its ideal qualities. The analyses of the coal seams to be mined are considered confidential <br />and are provided in the original permit application and will be provided to the Division under separate <br />cover. <br /> <br />Stratigraphy <br /> <br />The permit area is underlain by as much as 13,500 feet of sedimentary rock consisting of approximately <br />4,500 feet of Paleozoic quartzite, limestone, shale, sandstone, and gypsum; and 9,000 feet of Mesozoic <br />limestone, shale, mudstone, sandstone, and conglomerate (Hallgarth, 1959). The coal seams mined at the <br />Colowyo operation are of Upper Cretaceous Age. <br /> <br />The generalized geological setting is shown on Map 7A. The stratigraphic positions of the coals mined <br />by Colowyo are illustrated on Figure 2.04.6-3B. <br /> <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 /> <br />Mancos Shale – This thick marine formation is the oldest exposed unit in the area and is located north of <br />the active Colowyo mine area in the Axial Basin. The formation is approximately 5,000 feet thick, <br />consisting predominantly of a calcareous lower phase and an upper phase that contains a few thin bedded, <br />tan, silty fine-grained sandstone layers within massive sandy shale. The deposition of the Mancos Shale <br />occurred in quiet offshore conditions when the western interior of the North American continent was