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-10- <br />• <br />approximately 18 inches of the near-surface soils to be certain that <br />any organic materials and roots, or other undesirable near-surface <br />soils are removed prior to beginning construction of the embankment. <br />Soils which underlie the site include some relatively thick layers <br />of soft to medium stiff clays. These soils will consolidate under the <br />weight of the embankment. Because of the drainage conditions, we an- <br />ticipate this consolidation to occur over a long period of time. Based <br />on the results of our analysis, it appears that it will take approxi- <br />mately 8 years to reach 90 percent consolidation. The estimated settle- <br />ment ranges from 8 to 12 inches, depending on the assumptions regarding <br />layer thickness and amount of load. As the soils consolidate the shear <br />strength will increase. In our opinion, a critical period will occur at <br />• the end of construction when the embankment reaches maximum height and <br />there will have been very little time for consolidation to occur. We <br />analyze the strength of the foundation materials using the lower strengths <br />observed in our investigation. For the end of construction condition <br />we estimate the factor of safety against shear failure to be approximately <br />3.0. <br />UNDERSEEPAGE <br />The entire area is generally underlain at a relatively shallow depth <br />by clays tone bedrock. The embankment and a cutoff constructed of the <br />on-site or similar clays will be very impervious. The maximum head under <br />normal operating conditions will be approximately 10 feet. Considering <br />the intended use of the embankment, we believe a relatively safe structure <br />• <br />