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<br /> <br />Several large beds of very clean sand were encountered in the alluvial materials. These beds were <br />used to construct the main embankment upstream Type 2 filter zone and for Type 2 drain blanket <br />fill on the main embattlartent liner. <br />' The Sante Fe formation gravels which were encountered in the higher excavations were used as <br />Type 1 material or Type 4 materials in the main embankment and sputter embankments. Due to <br />' the more angular nature of these materials they were not used in zones adjacent to the synthetic <br />liner surface. <br />Silt beds were encountered on the eastern side of the ridges within the impoundment area. The <br />eastern slopes of the ridges are on the leeward side of the prevailing winds, which indicates the silt <br />beds were deposited by the prevailing winds. This material was a very dry, very fine, non-cohesive <br />silt. The extent of this material was limited, therefore it was used mainly for shaping the more <br />gravelly silts as discussed in further detail in this report. <br />2.1 Main Embanl®ent Foundation <br />The main embankment excavation was performed between July 9 and July 21, 1490. The north <br />slope of the foundation had a relatively steep ridge located in the center of the abutment. Once <br />' the north abutment was completely stripped this ridge was excavated and shaped leaving a relatively <br />blunt knob. The excavated materials were used to fill in the toe of the steep slopes on the north <br />abutment, thus reducing the overall gradient of the north abutment. In additiout, some of the <br />material was used to fill in localized areas of the abutment foundation which had slopes which were <br />not conducive to liner placement. The exposed north abutment foundation materials were Sante <br />' Fe formation gravels. <br />The south abutment had relatively gentle slopes throughout the entire abutment. Several small <br />arroyos traversed the slope. These arroyos were cleaned of loose debris and backfilled with <br />compacted material to form a gently sloping grades throughout the abutment. The exposed material <br />on the north abutment was a silty sand with some gravels. <br />t A drain blanket channel was excavated in the lowest reaches of the embankment footprint from the <br />upstream tce of the main embattlrntent to the downstream toe. The channel alignrtrent followed the <br />alluvium deposit in the valley floor. This alluvial material was stockpiled and used for Type 1 <br />' material in the main embanlmtent fill The invert of the channel ran from elevation 8485-ft at the <br />upstream toe to 8,465-ft at the downstream tce of the main embankment. The average width of <br />' the channel was 100-ft wide. The side slopes of the channel were tapered up from the channel <br />bottom at 3:1 slopes. <br />4 <br /> <br />