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Foothill Sanitary Landfill Page 19 of 52 San Joaquin County DPW - Solid Waste Joint Technical Document Revised 12/04/2025 earthquake (MPE) without experiencing damage to the structures that control leachate, storm water, erosion, or gas, in accordance with applicable regulations. In 2002 EMCON/OWT investigated the stability of the landfill design of Module 1 and concluded that the 3.5 to 1 (H:V) global slopes were stable when minimum shear strength parameters were used (Appendix F). CBI, Inc. performed an updated slope stability analysis for the Foothill Sanitary Landfill (reference Appendix L). In the stability analysis one critical global section based on the Landfill’s final grading plan was investigated under dynamic conditions using the peak ground acceleration in rock based on the site specific MPE . Interim waste slopes were not analyzed for stability under dynamic conditions due to their temporary nature. The updated stability report concludes that the global dynamic stability for the final landfill configuration, which has 3 to 1 slopes and 15-foot-wide benches every 50 feet, meets the requirements set forth in Title 27 CCR. The landfill’s slopes can be seen on the final grading plan presented in Figure 6. Because the calculated factor of safety under dynamic conditions (seismic loading) is greater than 1.5, we have concluded that there should not be any movement of the refuse mass during an MPE event. 5.3.5. Maximum Height The maximum height of the refuse fill is 432 feet MSL. The County may seek to raise the permitted height limit, subject to regulatory approval. A height increase will require revision of the Preliminary Closure/Post Closure Maintenance Plan. 5.3.6. Minimum Refuse Elevation The lowest elevation of refuse at the landfill is anticipated to be 180 feet MSL (Table 2), approximately three feet above the base of excavation (Figure 5). 5.3.7. Minimum Five-Foot Separation to Groundwater The minimum separation between groundwater and refuse is approximately 140 ft, which exceeds the minimum regulatory requirement of five feet (Table 3).