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Project No. D-3885-06 <br />Christ Our Savior Catholic Parish <br />a long time for the pore water to drain out, and as a result, positive excess pore water <br />pressure develops. Development of excess pore water pressure leads to reduction in <br />effective stress, which in tum, reduces the shear strength of the material. If the pore water <br />pressure rises to a level such that the soil loses all its shear strength, liquefaction occurs. <br />Factors known to influence liquefaction potential include composition and thickness of <br />soil layers, grain size, relative density, groundwater level, degree of saturation, and both <br />intensity and duration of ground shaking. <br />According to current Seismic Hazard Zones maps published by the California Geological <br />Survey (CGS, Newport Beach Quadrangle, released April 17, 1997, the subject site is <br />located within an area that has been designated by the State Geologist as a "zone of <br />required investigation" due to the potential for liquefaction (see Plate E in Appendix A). <br />This fact, in conjunction with the occurrence of relatively shallow groundwater, the <br />presence of localized zones of medium dense, fine to medium-grained sands, and a nearby <br />fault system capable ofcausing strong ground motion, required a site-specific liquefaction <br />analysis in accordance with CCR Title 14, Section 3724. <br />The liquefaction study was based on the NCEER procedure (NCEER Workshop, 1997) <br />developed from the methods originally recommended by Seed and ldriss (1982). <br />Liquefaction potential and settlement have been calculated based on SPT as well as CPT <br />data using the computer program LIQUEFY5, latest version 5.8n, developed by Civil <br />Tech Software and updated 2012. <br />Groundwater was encountered between 14 feet to 23 feet in depth below the existing <br />ground surface and thus ground water depth of l4 feet was used in the analysis. Also, we <br />have provided liquefaction analysis based on historical high groundwater of 5 feet. <br />CPT-based liquefaction potential has been proposed for predicting liquefaction resistance <br />of sandy soils (NCEER I 997). Robertson and Wride ( 1998) developed an integrated <br />procedure to evaluate the liquefaction resistance of sandy soils based solely on CPT data. <br />16 <br />t <br />I <br />t <br />I <br />t <br />T <br />I <br />I <br />I <br />T <br />u <br />I <br />T <br />T <br />I <br />I <br />t <br />I <br />E