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-6- <br />• <br />• <br />U <br />medium hard to hard clays tone bedrock. Some lenses and layers <br />of relatively clayey sandstone were encountered in the bedrock. <br />Borings 1 through 5 were drilled along and near the proposed <br />axis of the structure. The depth to bedrock varied from a minimum of <br />7 feet in Boring No. 2 located high on the west abutment to approximately <br />18 feet on the east abutment with a maximum depth of about 18 feet along <br />the centerline of the structure near the existing valley bottom. Near <br />the ground surface the clays were stiff and generally became softer <br />with depth, however, the clays were stiff the full depth of the boring <br />at both abutments. In the central portion of the valley the soils became <br />soft to medium stiff at depths on the order of 8 feet. The stiffer <br />clays were at natural moisture contents near the plastic limit. The <br />lower clays near the water table exist at moisture contents slightly below <br />the liquid limit. The clays have liquid limits which range from 29 to <br />45 and plasticity indices ranging from a low of 10 up to 29. These soils <br />are relatively impervious in their natural state and will be very imper- <br />vious when compacted to high density near optimum moisture content. The <br />underlying claystones and sandstones are relatively incompressible ma- <br />terials when compared to the anticipated loads of the embankment. These <br />sedimentary rock formations are capable of sustaining very high loads <br />with only slight settlement. The clay layers between the underlying bed- <br />rock and the bottom of the embankment will consolidate under the loads <br />of the embankment. To evaluate the potential for consolidation, several <br />one-dimensional consolidation tests were performed. The results of these <br />