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n <br />2.1 General <br />As noted in Section 1, slope stability of both existing modules (1 through 4) and future <br />modules (5 - through 11) has been addressed in this study. Slope stability has been <br />analyzed for both static and seismic conditions. Also, slope stability of both permanent <br />waste slopes (i.e., global slope stability) and that of interim waste slopes (interim slope <br />stability) have been addressed. However, since significant amounts of waste are already <br />present within the existing modules, their interim slope stability is not considered critical. <br />Therefore, only global slope stability of the existing modules has been analyzed. In the <br />case of the future modules, slope stability of both interim and global slope stability have <br />been analyzed. <br />0 2.2 Design Criteria <br />2.2.1 Static Design Criterion <br />Title 27 California Code of Regulations (CCR) does not specify a minimum factor of <br />safety requirement for slope stability under static conditions. However, it should be <br />noted that traditional geotechnical practice typically requires a static factor of safety of <br />1.5 for slope stability of permanent slopes. Accordingly, a minimum factor of safety of <br />1.5 is used as the static design criterion for global slope stability. <br />Traditional geotechnical practice requires a lower factor of safety (1.25 to 1.3) for interim <br />slopes. However, since the interim waste slopes within the future modules may remain <br />for a relatively long time (a few years), a minimum factor of safety of 1.5 has also been <br />used as the design criterion for interim slopes. <br />2.2.2 Seismic Design Criterion <br />Title 27 CCR requires that Class III landfills be designed to resist peak ground <br />acceleration (PGA) anticipated at the site during the Maximum Probable Earthquake <br />(MPE). The MPE is defined by the California Division of Mines and Geology (1975) as <br />"the earthquake that is likely to occur in 100 years, but it is not to be smaller than the <br />largest historical earthquake." As noted previously, the seismic slope stability analysis <br />presented in this report has been performed based on an updated MPE hazard report <br />prepared by Dr. Norman Abrahamson (2007). <br />Geotechnical Analyses for NCRCSL Department of Public Works/Solid Waste <br />Shaw Environmental, Inc. County of San Joaquin, December 12, 2007 <br />2-1 <br />