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• Overburden, Interburden, and Underburden Characteristics <br />Survey information, including date drilled, elevation, location, and coordinates, for the three Phase <br />I and three Phase II drill hole locations is included with the lithologic descriptions in Attachment <br />2.04.6-1 (previously Peabody Appendix 6-1 ). The locations of these holes are shown on Map <br />2.04.6-1. The analytical results for the six locations are presented in Attachment 2.04.6-2 <br />(previously Peabody Appendix 6-4). Based upon these descriptions and the chemical and physical <br />analyses, the following overburden, Interburden, and underburden lithologic units were developed: <br />Unit 1: All overburden material from the topsoil recovery depth to about 4.0 + 2.0 and 16.0 + 2.5 <br />feet (mean and standard deviation values) above the top of the upper and lower Dakota <br />coal seams, respectively. The mean thickness of Unit 1 across the Nucla East study area <br />is 55.9 feet. The material consists predominantly of brown to light brownish gray sandstone <br />and light brownish gray to gray sandy shale. <br />Unit 2: The upper Dakota coal seam (includes areas where coal is oxidized and weathered) and <br />• encapsulating predominantly dark gray to black carbonaceous shale. The thickness of this <br />unit ranges from 3.1 to 12.3 feet with a mean and standard deviation of 6.5 + 3.5 feet, <br />respectively. The mean thickness of the upper Dakota coal seam within the Nucla East <br />study area is about 1.1 feet. <br />Unit 3: The middle three to ten feet (mean and standard deviation equal 7.1 + 2.3 feet, <br />respectively) of Interburden consisting predominantly of hard to extremely hard light gray <br />sandstone and gray shaley sandstone. <br />Unit 4: The lower two to four feet (mean and standard deviation equal 2.7 + 0.6 feet, respectively) <br />of Interburden directly above the lower Dakota coal seam. This unit consists of gray to dark <br />gray shale and very dark gray to black carbonaceous shale. <br />Unit 5: The lower Dakota coal seam. The lower Dakota coal seam generally ranges from 4.0 to <br />7.0 feet (partings omitted) in thickness with an average of about 5.8 feet. <br />• <br />REVISED August 2006 <br />2.04.6-28 <br />