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<br />. <br /> <br />. <br /> <br />from the basin and if there is leakage it must be of sufficient <br /> <br /> <br />volume to impair either the safety or the economics of the project. <br /> <br /> <br />The criteria generally accepted by engineering geologists was <br />stated by Dr. Frank Nickell in discussions with the R. M. A. G. <br />conunittee. <br /> <br />"A satisfactory reservoir is one which is enclosed by material <br /> <br />suitably watertight, or if not, one in which the water table <br /> <br />is in general tributary to the reservoir basin, and secondly, <br /> <br />which may be restrained as to water losses by percolation <br /> <br />distance to point of escape. In other words, we might not <br /> <br />have an entirely watertight reservoir, but we might still <br /> <br />have a suitably economical and engineering-wise project because <br /> <br />the amount of losses measured in terms of distance of travel, <br /> <br />head loss thereby, etc., would still make that a proper re- <br /> <br />servoir.1I <br /> <br />For leakage to occur from the Ruedi basin it would have to <br /> <br />be through the bedrock formations since the alluvium is shallow at <br /> <br />the damsite and will be cut off entirely in construction of the <br /> <br />dam. The Belden shale in the eastern portion of reservoir basin <br /> <br />is predominantly too fine grained and dense to be pervious. The <br /> <br />Maroon formation also contains dense, hard, shale layers and the <br /> <br />sandstone layers are generally fine grained and well cemented. <br /> <br />significant leakage through the Maroon formation is improbable. <br /> <br />Such leakage as might occur in the Maroon would be through joints <br /> <br />or fractures which are subject to grouting. Also these paths would <br /> <br />- 9 - <br />