1986-12-11_PERMIT FILE - C1981017

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-13- Above the Rollins formation and the "B" bed or Coal Basin seam is a thick layer of mudstones, sandstones and shales of 370 feet to 425 feet in thickness, known as the Lower Bowie Shale Submember. Bowie shale occurs in the Williams Fork Formation. The Middle sandstone submember overlies the Lower Bowie shale and is similar in many respects to the Rollins sandstone. It ranges in thickness from 30 feet to 130 feet and is fine-to-medium grained, quartzitic to feldspathic, poorly to moderately sorted, with a clay matrix at the top. Directly above the Middle sandstone is a coaly, black to gray, sandy siltstone which merges into the overlying coal seam, known as "M" Creek or Middle Bed Seam. The coal seam ranges from 5 feet to 20 feet thick, and is mined from the No. 2 mine entry. The overlying sequence is the Upper Bowie shale submember. It consists of mudstones, sandstones, and shales and is around 200 feet thick. The upper sandstone submember, which overlies the Upper Bowie shale, is up to 100 feet thick. It is similar to the Rollins and Middle sandstone, except that grain size is somewhat more coarse. Above the Upper sandstone, is the Paonia shale member of the Williams Fork Formation. It consists of and includes the Placita and Sunshine Coal Intervals. The coal seams mined at Coal Basin are the "B" bed and the "middle" bed. The two other seams in Coal Basin are considered uneconomic to mine using current mining methods. Further information on the geology of the permit area can be found in Volume 4, Chapter III-D of the application. The analyses of roof rock and coal (the floor material is coal) in Section III-D, Volume 4, indicate that the materials are generally high in iron and have a high sodium adsorption ratio (SAR). A sample of roof rock from Mine No. 3 had a high nickel value. The high iron levels and the high nickel value should not pose a significant problem because both iron and nickel are relatively insoluble ,at the pH values characteristically found in the roof and coal materials and water associated with these materials. In addition, the sodic nature of the materials is not a significant problem. High sodium levels would not affect the plant growth characteristics of the materials since these sodium quantities are not toxic to plants, but rather would 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 coal processing waste (a combination of coal and roof rock), which may be subject to revegetation activities is coarse textured, thus there should be no problems. The proposed operation is in compliance with the requirements of this section.