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C~ <br />8. CONCLUSIONS <br />• <br />Based on results of our probabilistic seismic hazazd analysis, we <br />conclude peak horizontal bedrock accelerations at the Trout Creek dam <br />site will be 0.355 g at a 90% probability of non-exceedance in 5268 <br />years or an annual exceedance probability of 2 x 10-5, corresponding to <br />a return period of 50,000 years. This value for peak ground accelera- <br />tion corresponds to the U.S. Bureau of Reclamation's Design Standard <br />13 for seismic design. The effective peak horizontal acceleration, <br />0.302 g, at the Trout Creek site is calculated as 85% of the peak <br />horizontal acceleration (0.355 g). Values of peak and effective <br />horizontal bedrock accelerations for 90% values of non-exceedance for <br />various time periods of interest can be derived from the seismic hazard <br />ctrrves shown on Figure 8. Response spectra for maximum earthquake <br />ground motions and 5%, 7%, and 10% of critical damping at the 50th <br />and 84th percentiles are illustrated on Figures 9, 10 and 11, respec- <br />tively. <br />9. GENERAL INFORMATION <br />The information in this report is intended to provide an assessment of <br />earthquake hazards and ground motions for dynamic analysis of the <br />proposed Trout Creek dam. It is based on review of available geologi- <br />cal and seismological literature, earthquake catalogs compiled from <br />various sources, our general experience with the proposed <br />construction, and past experience with similaz conditions. The conclu- <br />sions and recommendations presented in this report are subject to the <br />limitations and explanations contained herein. The economic and <br />technical performance of the project cannot be guazanteed in any <br />respect. <br />MICHAEL W. WE: <br />By: Michael W. We <br />President <br />37 <br />