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Foothill LF Stability.docx <br />CB&I <br />180 Promenade Circle, Suite 320 <br />Sacramento, CA 95834 <br />Telephone: 916-565-4316 <br />January 13, 2015 <br /> Project 149259 <br />Taj M. Bahadori, P.E. <br />Senior Civil Engineer <br />San Joaquin Department of Public Works <br />Solid Waste Division <br />1810 E. Hazelton Avenue <br />Stockton, CA 95201 <br />Re: Review of the Stability Analysis at the Foothill Sanitary Landfill <br />Dear Mr. Bahadori: <br />This letter is CB&I’s response to the Central Valley Regional Water Quality Control Board staff <br />request for the review of the stability analysis at the Foothill Sanitary Landfill (FSL). <br />In 2012 CB&I performed a revised global stability and seismic analysis for the FSL. Because the <br />landfill is a Class III facility, the seismic slope stability analysis was been performed using ground <br />motions corresponding to the maximum probable earthquake (MPE). Since the time of the 2012 <br />analysis the faults used in the analysis have not experienced any new seismic activity. An MPE with a <br />magnitude of 8.1 along the San Andreas Fault located approximately 84 miles from the site was <br />considered the strongest earthquake for the FSL. <br />We have also reviewed the previous stability analysis and have concluded that the engineering <br />analysis used in the assessment are still valid. The portion of the State of California that the FSL is <br />located is considered one of the more stable portions of the State from a seismic shaking potential. <br />The global stability analysis took into account the final grades of existing Module I, and future <br />Modules 1 and 2 as a critical section. <br />Therefore, we do not believe that an additional stability or seismic study needs to be conducted at this <br />time. <br />Please call if you have any questions. <br />Sincerely, <br />CB&I Environmental and Infrastructure, Inc. <br />Julian C. Isham, PG, CEG, CHG <br />Geology Manager