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-11- • - IV. Geology (2.09.5, 2.04.6) The area to be affected over the Life of the operation is part of the Bookcliffs coal field which is an outcropping of the Mesaverde Group. The Bookcliffs coal field is situated on the southern rim of the Uinta Basin. The structural rim of the basin falls along the crest line of the Uncompahgre uplift, some 30 miles to the south. The coal seams of the project area occur in the Mount Garfield Formation of the Mesaverde Group. For purposes of description of the Localized structure in the general vicinity of the permit area, the Bookcliffs coal field is characterized by a monoclinical structure with the strata dipping gently to the northeast. The surface geology of the project area is mapped in Exhibit 13 of the application. The general stratigraphy and structure is depicted in the cross-section and geologic column of Exhibit 14 of the application. Four coal zones containing minable seams outcrop along the face of the Baokcliffs in Colorado. The stratigraphically highest zone has been named the "Carbonera coal zone". Two or three seams are usually present in this zone. About 60 feet below the Carbonera coal zone is the Cameo coal zone. One or two seams are comrranly present in this zone. Where there are two coal seams, the interval between them is 30 feet or less. The Cameo zone is thick, laterally extensive, and the most productive coal zone in the Bookcliffs field. The Lower Cameo seam immediately overlies the Rollins Sandstone. The interval between the base of the Cameo coal zone and the base of the Palisade coal zone, the next lower coal zone, ranges from 200 to 450 feet, being greater in the east than in the west. The Sego Sandstone underlines the Palisade zone and is a regional formation correlation marker. The interval between the base of the Palisade coal zone and the base of the Anchor croal zone, the lowest of the four, ranges from 45 to 60 feet. Of the four coal seams present in the Bookcliffs coal field, only the Cameo 'B' and 'C' seams are recognized as being minable in the permit area. The Cameo 'B' seam is presently being mined at the Roadside mine on the east side of the Colorado River and at the Cameo No. 1 mine on the west side. The Cameo 'B' seam varies in thickness from a minimum of four (4) feet to a maximum of eleven (11) feet in the permit area. The minable seam averages about six (6) feet in thickness. The coal has been classified as high volatile bituminous characterized by low sulfur and a anderately high ash content. Further information on the geology of the permit area can be found in Sections 2.04.5 and 2.04.6 of Volumes I and V The analyses of the roof, floor, coal and refuse materials in Appendix O of Volume V indicate that the materials are generally high in iron (Fe), and have a high pH and sodium adsorption ratio (SAR). The high iron level should not pose a significant problem because iron is relatively insoluble at the high pH values characteristically found in the materials. In addition, the sodic nature of the materials is not a significant problem. The sodium levels are similar to those found in the soils of the area and much lower than those found in the .exposed strata, such as Mancos shale, which outcrops in the general vicinity of the mine. The high sodium content would not affect the plant growth characteristics of the materials, since these sodium quantities are not toxic to plants, but rather destroy the structure of soils, particularly in soils of predominantly clay texture. The result of this breakdown is a decrease in the infiltration rate, thus a decrease in water available for plant growth. However, the refuse material, which is the only waste material which may be subject to revegetation activities, is croarse textured (70+~ sand size), thus there should be no problems. The proposed operation is in compliance with the requirements of this section.