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Port of Everett—South Terminal Wharf& Electrical Upgrades— Phase 2 17 <br /> hazard levels were obtained from the United States Geologic Survey(USGS 2008)for the site location,for a <br /> V530of 2,500 feet/second, representing an equivalent bedrock site.These response spectra, presented in <br /> Appendix D were used as input to our ground response analyses and two-dimensional analyses, and <br /> should not be used as a ground surface response spectrum for structural design. <br /> Table 3 — Summary of Considered Hazard Levels <br /> Return Percent Probability Time <br /> Period Interval <br /> of Exceedance <br /> (years) (years) <br /> 72 50 50 <br /> 94 40 50 <br /> 144 30 50 <br /> 224 20 50 <br /> 475 10 50 <br /> 2,475a 2 50 <br /> a. The 2,475-year hazard level was used as a basis for the Design Earthquake(DE)evaluation. <br /> Site-Specific Response Spectra <br /> Because of the existence of potentially liquefiable soils at the Port of Everett site, a site-specific ground <br /> response analysis is required for the wharf structure.The site response analyses were performed on two <br /> representative profiles. Profile 1 was developed to represent a profile extending from the top of the <br /> construction dike to below ESU 7, and featured no potentially liquefied soils. Profile 1 was analyzed using a <br /> total stress analysis, in which excess pore pressures are assumed not to develop in the soil. Profile 2 <br /> represents an offshore profile underlain by relatively thick deposits of liquefiable native sands and silts. In <br /> addition to a total stress analysis, Profile 2 was analyzed using the effective stress framework, in which the <br /> effects of cyclic pore pressure generation on the stiffness and damping properties of the soil are accounted <br /> for.Two platforms, DEEPSOIL(Hashash et al. 2016) and FLAC(Cundall, 1986),were used to perform the <br /> non-linear response analyses in the time domain.The procedures used to develop a site-specific response <br /> spectrum for the site is described in Appendix D. <br /> Analysis Results and Recommended Site-Specific Spectra <br /> The results of the site-response analyses and recommended spectra are shown on Figure 10 and <br /> summarized in Tables 4 through 9. For the 72-year, 94-year, 144-year, and 224-year hazard levels,the <br /> results are below the 80%code-based spectrum, and thus the recommended spectra are controlled by <br /> their corresponding 80%code-based spectra entirely. For the DE 475-year hazard level,the total stress <br /> analysis results for Profile 1 and the effective stress analysis results in FLAC for Profile 2 exceed the 80% <br /> code-based spectrum between approximately 0.10 and 0.50 seconds, which is reflected in the <br /> recommended spectrum. <br /> mf <br /> 4, 19232-01 <br /> HARTCROWSLR December 6,2017 <br />