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<br />I <br />I. <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />SUMMARY <br /> <br />This report presents results of field exploration and engineering <br />analyses performed to define alternative water storage projects on Rock <br />Creek and Muddy Creek. The selected alternative is to be constructed <br />to provide a water supply for Western Slope users. The work included <br />an earthquake hazard evaluation, determining site characteristics in- <br />cluding flood hydrology studies and dam location studies, site geologic <br />and construction materials evaluation, and formulating definitive <br />project plans and preparing feasibility level cost estimates for both <br />alternative projects. <br /> <br />The results of the earthquake hazard evaluation conservatively esti- <br />mated the potential earthquake magnitude to be of Richter magnitude <br />5.5, occurring within 10 km of each site. <br /> <br />Studies were made of alternative dam axis locations at the Rock Creek <br />site and the relative costs of different dam types and dam heights were <br />developed for both sites. Geotechnical investigations, including geo- <br />logic mapping, seismic refraction lines and borehole drilling, showed <br />that the foundations at the selected axis locations at both sites are <br />suitable for either a rockfi11 or a concrete gravity dam. Samples were <br />obtained from potential construction material borrow areas in the vici- <br />nity of both sites and the material was evaluated for use in dam con- <br />struction by laboratory testing and trial mix design programs. Flood <br />hydrology studies were made to determine spillway design requirements <br />and sedimentation studies were made to determine sediment reserve space <br />requirements. <br /> <br />Upon evaluation of results of the above studies and based on prelimi- <br />nary cost estimates, the following dam projects were selected for <br />further evaluation: <br /> <br />S - 1 <br /> <br />7043W/5020W <br />