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<br />Woodward.CIyde Consultants <br /> <br />, "/ <br />t ". "" <br /> <br />I <br /> <br />of the Pierre shale generally weathers to a depth of 3 to 10 <br /> <br />feet below the ground surface or below the overlying sediments. <br /> <br />The weathered shale may be soft and easily erodible. <br /> <br />The overburden Tertiary and Quaternary soils were <br /> <br />deposited over the top of the pierre shale by eastward flowing <br /> <br />braided streams and strong wind. The material consists of <br /> <br />lightly consolidated to unconsolidated sands, gravels and silts <br /> <br />with layers of fine, wind blown sands and loessial silts. <br /> <br />These sediments tend to be quite pervious and the loess and <br /> <br />less dense stream sediments could be subject to considerable <br /> <br />consolidation under conditions of loading and wetting. They <br /> <br />are also highly erodible. <br /> <br />3. Geologic Structure <br />Both field examination and preliminary mapping indicate <br /> <br />that the Pierre shale in the site area is structurally <br /> <br />. <br /> <br />favorable. No evidence of faulting, shearing or excessive <br /> <br />jointing has been found, nor has there been any other evidence <br /> <br />of adverse tectonic deformation. The alluvial and wind <br /> <br />I <br /> <br />deposited cover is essentially structureless as would be <br /> <br />expected of young stream and wind-laid deposits. <br /> <br />4. Other Considerations <br /> <br />. There is evidence that montmorillonite minerals are <br />present in the Pierre shale formation and at some locations the <br /> <br />formation may contain weak layers. The shale and weathered <br /> <br />. <br /> <br />shale may also have swelling tendencies that could adversely <br /> <br />- 8 - <br /> <br />. <br /> <br />ft <br />