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EXHIBIT 2 <br /> Santa Ana Boulevard Grade Separation <br /> September 13,2011 <br /> Page 5 <br /> Deep Foundation Design: To facilitate fabrication and cost estimate, we recommend using the <br /> same pile type as the bridge abutment. However, the axial pile demand should be 45 tons for <br /> retaining wall and the corresponding HP pile section is HP 1Ox42. Using a 45-ton service <br /> demand, a preliminary pile length of 50 feet is recommended. <br /> Construction Considerations <br /> Groundwater was not encountered in any of the as-built borings down to about elevation +50 <br /> feet. Therefore, groundwater is not anticipated to be encountered during pile construction and <br /> footing construction at the supports and walls. However, groundwater level can fluctuate due to <br /> seasonal rainfall amount, local irrigation and groundwater recharge program, and other man- <br /> made conditions. If groundwater is encountered during footing construction, it should be <br /> controlled in accordance with Section 19-3.031) of the Caltrans Standard Specifications <br /> (Caltrans, 2010). If groundwater is encountered during CIDH pile construction, contractor should <br /> be prepared to use a "wet" method of construction for the CIDH piles. As a standard Caltrans <br /> practice for "wet" construction, PVC tubings should be installed within the reinforcement cage <br /> for gamma-ray testing. <br /> Based on the As-Built LOTB sheets of the nearby structures, the onsite soils are generally loose <br /> to very dense coarse grained materials and these materials are susceptible to caving. If caving <br /> occurs, a temporary casing can be used. The casing should have an inside diameter larger than or <br /> equal to the pile diameter and should be placed tight in the hole. Vibratory hammers or oversized <br /> drilling are not allowed for casing installation. In the event that any boring becomes bell-shaped <br /> and cannot be advanced due to severe caving, all loose material should be removed from the <br /> bottom of the boring and the caved region filled with a low strength sand-cement slurry. Drilling <br /> may continue when the slurry has reached its initial set. <br /> Based on the As-Built LOTB sheets of the nearby structures, gravel and cobbles were recovered <br /> during drilling operations in multiple borings and are expected to be encountered during CIDH <br /> pile construction. While there could be a trace amount of cobbles between 6 inches and 1 foot <br /> diameter, the largest rocks of significance that will be encountered would likely be small <br /> cobbles, in the 3- to 6-inch diameter range. While the oversized material will likely create <br /> difficult drilling conditions, large-diameter augers typically have flights with wide spacing and a <br /> shallow pitch allowing rock pieces, cobbles and boulders to be extracted from the drilled hole. <br /> Rock augers and clean-out buckets can also be used to extract oversized material where a high <br /> concentration of gravel and cobbles are encountered. <br /> References <br /> Abrahamson, N. A., and Silva, W., 1997, "Empirical Response Spectral Attenuation Relations <br /> for Shallow Crustal Earthquakes," Seismological Research Letters, Vol. 68, No. 1, <br /> January/February. <br /> AREMA, 2009, "Manual for Railway Engineering," American Railway Engineering <br /> Association, Chapters 8, 9, 15. <br /> a Earth Mechanics,Inc. <br /> Geatechnical&Earthquake Engineering <br />