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-8- <br />• <br />including coal shale is encountered east of the Cretaceous sandstone. <br />The east side of the pit will be excavated in soft to hard inter- <br />layered sandstone and claystone of the Tertiary Middle Park Formation. <br />The characteristics of each major bedding series are discussed in the <br />following paragraphs. <br />Cretaceous Sandstone and Shale: Upper Sandy Member, Pierre <br />Shale Formation <br />The sandstone and shale which will be encountered on the <br />• <br />west side of the pit are a part of the Upper Sandy Member of <br />the Cretaceous Pierre Shale Formation. The sandstone and very <br />hard claystone (shale) has formed a massive, relatively competent <br />rock. The Logs of Exploratory Borings, 77-11C and 77-13C, <br />indicate high recovery with the NX wireline core and a Rack <br />quality Designation (RQD) of 95 percent within the sandstone. <br />The results of RQD determinations are shown on Table I, and on the <br />Logs in Appendix I. Where exposed in the existing pit, the sand- <br />stone is massive, indurated, rings when struck with a rock hammer, <br />and resistant to erosion. Existing slopes in this sandstone stand <br />on angles as steep as 50 degrees to a n~ximum height of 200 feet. <br />The Cretaceous sandstone is the strongest material encountered . <br />in the borings. <br />Coal <br />The coal encountered in the exploratory borings varied from <br />high quality coal to carbonaceous claystone (coal shale). The <br />coal was massive at some locations but included random claystone <br />• <br />