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<br />0437 <br /> <br />embankment dam can be constructed on it. The simplicity of the question, unfortunately, <br />is such that the inference might be drawn that a simple "yes" or "no" answer should <br />ensue. <br /> <br />On the broadest and most general of bases, we do not hesitate to affirm that, <br />despite the difficult foundation conditions at the site, and the less than high quality em- <br />bankment materials available nearby for construction of a dam of the height and length <br />contemplated, currently available engineering and geologic experience and knowhow is <br />sufficient to develop a safe, reliable design. The challenge is to so apply that knowhow, <br />in a fully integrated fashion to a multiplicity of engineering and geologic details, as to <br />develop a final design that is so modified from mile to mile along the a.'tis of the dam as <br />to be fully defensive against any credible foundation defect of such nature as to threaten <br />the performance of the dam. In our judgment, the Feasibility Design, Figure 2, does <br />not fully achieve that goal. Modifications to that design, which we understand are cur- <br />rently being favored by some USBR designers, such as addition of an internal gravel <br />drain downstream from the core zone, and addition of relief wells along part of the <br />downstream toe of the dam, would greatly improve the safety aspects of the Feasibility <br />Design. Other measures which we believe would merit consideration in the USER's de- <br />sign of the dam will be set forth in the following section of this report. Incidentally, <br />we do not conclude that relief wells are either useful or necessary at this dam. <br />SPECIFIC COMII'!:ENTS <br />Successful design of a dam, especially for one on a very long and complex site <br />and on a very large river, requires a balanced consideration of the inter-relationships <br />of many engineering and geotechnical disciplines. Those that we consider to be partic- <br />ularly important to the question directed to US are discussed under the following head- <br /> <br />ings: <br /> <br />1. Hydrology. <br />2. Reservoir Operation. <br />3. Foundation Conditions. <br />a. Left Abutment and Riverbed. <br />b. Right Abutment - Slurry Trench Reach. <br /> <br />7. <br />