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MS9238GE <br />• placing a protective -cover of aeotextiles or rip rap. The protec- <br />tive cover should extend beyond the limits of water level fluctua- <br />tion plus some additional margin. The interior embankment slope <br />configuration concept is shown on Figure 9. <br />4.6 Interior Excavation Cut Slopes <br />Our analysis of the interior excavation cut slope was based on <br />the soil strength c'raracteristics of the soil materials likely to <br />be encour_tered in the excavation cut slope, a maximum depth of <br />water of ten (10) feet, and a maximum excavation cut slope height <br />of about thirty (30) feet. Our analysis indicted an interior <br />excavation cut slope of two and one quarter (2-1/4) to (1) (horiz- <br />ontal to vertical) may be used considering steady state conditions <br />and rapid draw-down conditions. A minimum calculated factor of <br />safety of 1.5 was used as the steady state criteria and a minimum <br />calculated factor of safety of 1.2 was used as the rapid draw-down <br />criteria. The interior embankment slope configuration concept is <br />shown on Figure 10. <br />4.7 Embankment Crest Width <br />The embankment should be constructed with a crest width of at <br />least ten (10) feet. The crest may be widened if needed for <br />vehicular or equipment traffic. <br />• 4.8 Earth Work <br />It is our opinion that the embankment materials should be placed <br />wet of optimum moisture content for compaction and compacted using <br />a kneading type compactor such as a sheepsfoot roller. The soil <br />moisture content for compacting the embankment material should <br />range from optimum to four (4) percent greater than the optimum <br />moisture content and the material should be compacted to at least <br />ninety (90) percent of the maximum dry density as defined by ASTM <br />D698, standard moisture density relationship (Proctor) test. No <br />embankment material should be placed when the moisture content is <br />greater than four (4) percent above the optimum moisture content. <br />The purpose of this technique is to encourage a dispersed rather <br />than a flocculated clay particle structure within the compacted <br />fill material. The dispersed clay structure is less permeable and <br />more flexible which will help reduce the influence of slight <br />differential settlements of the embankment foundation. <br />If it is desired to begin construction on the embankment during <br />late fall, winter or early spring, it should be noted that freezing <br />of the last lift of the previous day's work is likely. If this is <br />8 <br />U <br />~l.ambert ana q,s,~oriatE,s <br />CONSULTING OEOTEON NIGL ENGINEERS AND <br />MATERIAL TESTING <br />