2009-08-13_PERMIT FILE - C1981019A (4)

Home Browse Search

RULE 2 PERMITS 2.04.6 Geology Description The coal to be mined in the permit area is located in the northern extent of the Danforth Hills coalfield of the Uinta Region. The Danforth Hills coal field comprises the coal deposits on the northeast flank of the Piceance Creek basin and is bordered on the northeast by the Axial Basin Anticline. The general stratigraphy within the permit revision area is shown on figures 2.04.6-3A and 2.04.6-3B, and is graphically shown on figures 2.04.6-4A through 2.04.6-4F. The locations of the geologic cross sections are shown on Map 7. Coal seams X and A through G~gy will be mined in the South Taylor area. The proposed coal seams to be mined in the bower Wilson pit are anticipated to be the G, H, I, and J seams and splits of these seams. The thicknesses of these seams are shown on figures 2.04.6-3A and -3B. The coal to be mined has a high BTU value of 10,000 to 11,000 BTU per pound, low sulfur, and low ash content. It is in generally discreet seams of mineable thickness. There exists a market for [his coal, in part because of its ideal qualities. The analyses of the coal seams to be mined are considered confidential and are provided in the original permit application and will be provided to the CDMG under separate cover. stratigraphy The permit azea is underlain by as much as 13,500 feet of sedimentary rock consisting of approximately 4,500 feet of Paleozoic quartzite, limestone, shale, sandstone, and gypsum; and 9,000 feet of Mesozoic limestone, shale, mudstone, sandstone, and conglomerate (Hallgarth, 1959). The coal seams mined at the • Colowyo operation are of Upper Cretaceous Age. The generalized geological setting is shown on Map 7. The stratigraphic positions of the coals mined by Colowyo are illustrated in Figure 2.04.6-3A and Figure 2.04.6-3B. The slirficial geologic formations within the area are the Upper Cretaceous Mancos Shale, which is overlain by the upper Cretaceous Mesaverde Group. The Mesaverde Group is comprised of the Iles Formation and Williams Fork Formation. Details of each formation aze described below. Mancos Shale -This thick marine formation is the oldest exposed unit in the area and is located north of the active Colowyo mine area in the Axial Basin. The formation is approximately 5,000 feet thick, consisting predominantly of a calcareous lower phase and an upper phase that contains a few thin bedded, tan, silty fine-grained sandstone layers within massive sandy shale. The deposition of the Mancos Shale occurred in quiet offshore conditions when the western interior of the North American continent was inundated by an epeiric seaway during the late Cretaceous. The Mancos Shale is generally more than 3,000 feet below ground surface in the permit area and is about 1,700 feet below the base of projected mining. South Taylorn-ower Wilson -Rule 2, Page 28 Revision Date: 11/30/06 Revision No.: PR-02