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-~- <br />• drilled to obtain high quality Pitcher samples for laboratory shear <br />tests. In addition to the borings specifically requested by our <br />firm, rotary borings were drilled for coal quality sampling and data <br />from these borings including electric logs were provided by Kerr <br />Coal Company. Locations of the exploratory borings are shown on <br />Fig. 3. Detailed logs of the borings are presented in Appendix I. <br />At the time of drilling, the core was logged and measured in the <br />field. The core was then returned to our laboratory for detailed log- <br />ging and selection of samples for testing. During both the field and <br />laboratory logging the Rock Quality Designation (RQD), and joint and <br />fracture orientation and spacing was measured. The RQD is a measure <br />of the length of core which is at least two tunes the diameter of the <br />core in length. As an example, sound rock which is retrieved as a <br />single piece of core will have an RQD of 100 percent. An RQD of 100 <br />• percent is also possible if the core is in pieces each two times the <br />diameter in length. If there are no pieces longer than two times the <br />diameter of the core the RQD is 0 percent. The RQD provide an impor- <br />tant qualitative means of evaluating the soundness of the rock and <br />joint and fracture spacing of the rock. <br />Bedding Sequence <br />The formations occurring at the site do not have a regular <br />sequence throughout the site with depth due to the dip of the forma- <br />tions. Three general subsurface conditions occur across the pit <br />area. Starting at the west side of the pit very hard Cretaceous <br />sandstone and shale forms the west wall of the pit. The coal, <br />r~ <br />