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EXHIBIT 2 <br /> Santa Ana Boulevard Grade Separation <br /> September 13,2011 <br /> Page 3 <br /> Liquefaction Potential and Seismic Settlement Evaluation <br /> The subject site is anticipated to have a low liquefaction potential due to the absence of <br /> groundwater. Since the liquefaction potential at the bridge site is anticipated to be low, seismic <br /> settlement of onsite soils is also anticipated to be low. A more detailed liquefaction assessment <br /> will be conducted during the PS&E phase using site-specific soil boring data. <br /> Scour Evaluation <br /> The proposed structure does not cross a channel that conveys water; therefore, scour potential is <br /> not anticipated to be a design issue. <br /> Corrosion Evaluation <br /> There is no corrosion test result included with the as-built plans. Site-specific soil coarrosivity <br /> will be investigated during the PS&E phase in accordance with Caltrans requirements. <br /> Foundation Data of Nearby Bridges <br /> The proposed GS is a new structure and therefore, no as-built foundation data specific to this <br /> structure is available. However, the as-built plans for the nearby three structures (Bridge <br /> Numbers 55-671L, 55-672, and 55-675) that are located less than 0.3 mile from the proposed <br /> railroad bridge were reviewed as part of this project. All of these structures are supported on <br /> driven concrete piles with a service demand of 45, 70, or 100 tons. <br /> Preliminary Bridge Foundation Recommendations <br /> Bridge Configuration: The preliminary plan provided by the structural engineers indicates that <br /> the Santa Ana Boulevard GS is a four-span steel plate girder bridge with a total bridge length of <br /> about 247 feet and a total bridge width of about 40 feet. <br /> Foundation Type: Due to the presence of weak near-surface site soils, deep foundation is <br /> recommended for the proposed structure. The preliminary plans provided by the structural <br /> engineers show that large-diameter Cast-In-Drilled-Hole (CIDH) pile extensions will be used at <br /> the bents and driven steel HP piles will be used at the abutments. <br /> Based on the information provided by the structural designers, the abutments are supported by <br /> 100-ton steel HP piles (HP 14x89). For each 6-foot diameter CIDH pile, a service load of 960 <br /> kips is provided by the structural designers. Based on these axial demands, the preliminary pile <br /> lengths are 70 feet and 55 feet at the abutments and the bents, respectively, for cost estimating <br /> purposes. <br /> As mentioned earlier, as-built foundation type for the three nearby Caltrans bridges is driven <br /> precast-prestressed concrete (PCC) piles. We will evaluate the feasibility of using driven PCC <br /> piles instead of the HP-piles during the PS&E phase when site-specific soil boring data become <br /> available. <br /> a Earth Mechanics,Inc. <br /> Geatechnical&Earthquake Engineering <br />