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<br />. <br />. <br />'. <br />I <br />. <br />. <br />I <br />I <br />I <br />I <br />. <br />I <br />. <br />. <br />I <br />I <br />I <br />. <br />I <br /> <br />"\)1'09 <br />'J ... <br /> <br />A sufficient quantity of impervious fill is available on the left abutment to <br />provide material for the core of the embankment and for the upstream <br />impervious blanket. <br /> <br />Exposed bedrock was mapped above the waterl ine of the existing Lake Avery for <br />a di stance of 2000 feet upstream of the dam. At that poi nt, it is covered <br />wi th all uvi al terrace materi al from above and cannot be traced further. After <br />treatment, the exposed rock would provide an acceptable surface to tie in the <br />impervious blanket. Future studies, however, should confirm the elevation of <br />the top of bedrock at the upstream contact for the enti re 1 ength of the <br />bl anket. <br /> <br />Sei smi c refracti on on the ri ght abutment showed the terrace deposi t to be up <br />to 50 feet in thickness. Even though it occurs at a higher elevation than the <br />terrace on the left abutment, it would be exposed to reservoir water with the <br />highest dam alternatives. Test pits excavated on top of, and upstream of, the <br />terrace, show it to be covered with five to fifteen feet of impervious clay. <br />This clay covers the entire abutment and extends down the upstream slope into <br />the reservoir. Therefore, it appears that no additional blanketing would be <br />necessary on the right abutment. <br /> <br />Geol ogi c mappi ng along the al i gnment of the proposed pi pel i ne reveal ed that <br />the right-of-way would be almost entirely on side slopes composed of the Eagle <br />Valley-Minturn Formation. The formation is composed of weak sandstone and <br />siltstone, and includes soluble minerals such as gypsum and anhydrite. <br />Therefore, there is a potential along the alignment for development of sink <br />holes below the pipline and for slope failure. At several points upstream of <br />Buford, the alignment would cross landslide debris originating from the edge <br />of the basalt flows occurring at higher elevations. These areas also could <br />offer potential for slope instability. Any future, more detailed study of the <br />Lake Avery Project should include geotechnical work at the diversion damsite <br />and along the pipeline alignment. <br /> <br />Since the reservoir capacities considered at Lake Avery do not coincide with <br />those studied at the other sites, the cost estimates were expressed as units <br />of cost per acre-foot of storage in order to draw economic comparisions. The <br /> <br />E-6 <br />