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at least 18 (Bray and Sancio, 2006) are generally not considered to be susceptible to liquefaction, nor are those soils which are above the historic static groundwater table. The liquefaction analysis was conducted in accordance with the requirements of Special Publication 117A (CDMG, 2008), and currently accepted practice (SCEC, 1997). The liquefaction potential of the subject site was evaluated using the empirical method developed by Boulanger and Idriss (Boulanoer and Idriss, 2008). This method predicts the earthquake-induced liquefaction potential of the site based on a given design earthquake magnitude and peak ground acceleration at the subject site. This procedure essentially compares the cyclic resistance ratio (CRR) [the cyclic stress ratio required to induce liquefaction for a cohesionless soil stratum at a given depth] with the earthquake-induced cyclic stress ratio (CSR) at that depth from a specified design earthquake (defined by a peak ground surface acceleration and an associated earthquake moment magnitude). CRR is determined as a function of the corrected SPT N-value (Ni)60-cs, adjusted for fines content. The factor of safety against liquefaction is defined as CRR/CSR. Based on Special Publication 117A, a factor of safety of at least 1.3 is required in order to demonstrate that a given soil stratum is non-liquefiable. Additionally, in accordance with Special Publication 117A, clayey soils which do not meet the criteria for liquefiable soils defined by Bray and Sancio (2006), loose soils with a plasticity index (PI) less than 12 and moisture content greater than 85% of the liquid limit, are considered to be insusceptible to liquefaction. Non-sensitive soils with a PI greater than 18 are also considered non-liquefiable. As part of the liquefaction evaluation, Boring No. B-1 was extended to a depth of 503= feet. This boring encountered free water at a depth of 223: feet during drilling. The historic high groundwater depth was obtained from CGS Open File Report 97-20, the Seismic Hazard Evaluation of the Tustin Quadrangle, which indicates a historic high groundwater depth at the subject site of approximately 15* feet. Therefore, the historic high groundwater table was considered to be 15 feet for the liquefaction evaluation. The liquefaction analysis procedure is tabulated on the spreadsheet forms included in Appendix F of this report. The liquefaction analysis was performed for Boring No. B-1. The liquefaction potential of the site was analyzed utilizing a PGAM of 0.553g for a magnitude 6.65 seismic event. If liquefiable soils are identified, the potential settlements that could occur as a result of liquefaction are determined using the equation for volumetric strain due to post-cyclic reconsolidation (Yoshimine et. al, 2006). This procedure uses an empirical relationship between the induced cyclic shear strain and the corrected N-value to determine the expected volumetric strain of saturated sands subjected to earthquake shaking. This analysis is also documented on the spreadsheets included in Appendix F. Conclusions and Recommendations The results of the liquefaction analysis have identified potentially liquefiable soils at Boring No. B-1. The liquefiable materials are present in several layers between depths of 15 and 50* feet. Soils which are located above the historic high groundwater table (15 feet), or possess factors of safety in excess of 1.3, are considered non-liquefiable. Several encountered layers of silty clays are considered non-liquefiable due to their cohesive characteristics and the results of the Atterberg limits testing with respect to the criteria of Bray and Sancio (2006). Settlement analyses were conducted for each of the potentially liquefiable strata. > SOUTHERN G&M Convenience Store # 72 - Santa Ana, CA CALIFORNIA Project No. 16G1 23-1R GEOTECHNICAL Page 12