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<br />' On the south abutment sandy silt material was encountered in the upper reaches, which tapered into <br />' the coarser alluvial materials near the edge of the channel cut. <br />23 Upper Impoundmeat Fouadatioo <br />The upper impoundment foundation excavation material was used primarily to construct the main <br />t embankment, however selected zones of Type 2 and 3 materials were used for the liner foundation <br />or drain blanket cover. Stocl~iling of the Type 2 and 3 materials were performed when direct <br />placement of the materials were not feasible. Approximately 35,000 CY of Type 3 material was <br />' stockpiled on the north abutment of the upper impoundment, and approximately 60.000 CY of Type <br />2 material was stockpiled on the south abutment of the upper impoundment. <br />' The majority of the materials encountered in the upper impoundment excavation were alluvial sands <br />and gravels. The majority of the upper impoundment excavation was used as Type 1 and Type 4 <br />' fill in the main embankment, however, several relatively large banks of Type 1 and 2 material were <br />encountered in the excavation. <br />' A large silt deposit was enwuntered on the northwest slope of the splittec embankment which <br />extended from the sputter embankment to the northeast corner of the upper impoundment. This <br />material was either stocl~iled directly upslope from the excavation out of the phase 1 construction <br />limits, or hauled directly to the Type 1 fills which were in progress at the time of the excavation. <br />Avery large deposit of very clean, fine sand was encountered in the center of the upper <br />impoundment excavation. This material was used for the Type 2 filter zone in the lower reaches <br />' of the main embattlrntent fill <br />' Several localized zones of sandy clay were encountered in the floor of the upper impoundment. The <br />materials in these zones were saturated. These saturated zones were relatively small and localized: <br />the largest one encountered being 75-ft long and 30-ft wide. When these zones were encountered <br />' they were over-atcavated and backfilled with clean sands and gravels prior to placing the Type 3 <br />material on the foundation. <br />' A condemnation drilling hole was encountered on the south side of upper impoundment. The <br />casing was grouted shut prior to the construction operations. The steel casing was enwuntered to <br />' the full depth of the excavation, but water was seeping from the outside perimeter of the casing at <br />a rate estimated at less than 1 gpm. Once the excavation was at depth the casing was cut off. A <br />' small underdrain trench was extended from the casing to the sputter embankment underdrain. A <br />t 6 <br /> <br />