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<br />Woodward.Clyde Consultants <br /> <br />-. (' I.....'~ <br />\jjO\,) <br /> <br />and right abutment axis. Figure 2 is a geologic cross-section <br /> <br />along the dam axis. <br /> <br />In considering the question of geologic conditions related <br /> <br />to safety, the following matters were considered: <br /> <br />(1) The nature of foundation formations as related to <br />supporting the dam and appurtenant structures. <br /> <br />(2) Adverse geologic formational structures such as <br />faults, shear zones, etc. <br /> <br />(3) Minerals within the foundation formations that would <br />adversely affect the safety of the dam. <br /> <br />(4) Potential for landslides around the reservoir and at <br />or near the dam. <br /> <br />(5) Erosion resistance of critical areas at or near the <br />dam site. <br /> <br />(6) Seismologic conditions that might be adverse to the <br />safety of the dam. <br /> <br />2. Foundation Formations <br /> <br />The left side and central portion of the dam will be <br /> <br />founded upon the Pierre shale formation which consists of firm, <br /> <br />highly consolidated, carbonaceous shale. The right side of the <br /> <br />dam will be on Tertiary and Quaternary alluvial and aeolian <br /> <br />soils. <br /> <br />The Pierre shale is dark gray, thinly laminated to thickly <br /> <br />bedded. It was deposited in shallow marine conditions and, <br /> <br />although primarily composed of clayey and silty shale, it <br /> <br />contains some layers of fine, silty sandstone and can include <br /> <br />some layers of plastic clay. The laminations are nearly flat <br /> <br />lying with a northward dip of only 3 to 5 degrees. The surface <br /> <br />- ") - <br /> <br />u <br />