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<br />00186? <br /> <br />IV. GEOLOGIC AND MAPPING <br /> <br />The Study Area is characterized by the rugged mountain peaks and deep glaciated valleys <br />of the Gore Range on the east and the more gently sloping sedimentary rock to the west. The <br />formation of the mountain ranges, and the subsequent effects of erosion and deposition by <br />glaciers and other natural elements that occurred countless years ago, played an important role <br />in the planning of this water resources project. <br /> <br />The geologic and mapping programs were undertaken to define the land features in the <br />Study Area that will affect the cost and operation of the four configurations. The program was <br />accomplished in two stages, The first stage defined the topography and geology of the storage <br />and conveyance system associated with the Eagle-Piney configuration, and was initiated in the <br />summer of 1971. A second, supplementary geologic and mapping program was undertaken in <br />the summer of 1972 to develop data and information for other operational configurations which <br />were identified during the first year's work as possessing distinct merits. <br /> <br />The results of the geologic program showed that an impoundment site contemplated for <br />the Eagle-Piney configuration near Camp Hale on the Eagle River was unsuitable because of a deep <br />pervious foundation. Consequently, for the purposes of this study, the site was eliminated from <br />further consideration, Otherwise, the geologic and mapping programs indicated that the geology <br />of the area should not involve excessive costs in the construction of the structural elements of <br />the four configurations, However, the programs identified potential construction problems, <br />especially in the shear and other difficult zones through which the conveyance tunnels must pass, <br />Since it is expected that these zones represent a fairly small percentage of the total length <br />traversed by the tunnels, the overall increase in construction costs due to these areas of <br />unfavorable rock conditions should be slight. <br /> <br />The location and alignment of the structures and the determination of suggested <br />construction procedures to help minimize costs were based on the information gained from the <br />geologic and mapping programs, For example, where the geology suggests the presence of softer <br />sedimentary rocks, significant economies may be realized during project implementation by the <br />use of tunnel boring machines, <br /> <br />The dam type selected was also guided by the geology at the dam site and the availability <br />of material to economically construct the facility, Therefore, the cost estimates of the four <br />configurations were based largely on the geology and topography of the area and application of <br />construction practices that can be effectively and economically utilized, <br /> <br />8 <br />