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As indicated in Appendix B, a minimum factor of safety of 1.8 is obtained for a sliding block shear surface along the base liner and through the refuse in the north-south direction for the effective 3.25:1 final slope. A surface extending along the base liner and side slope interface liner was also analyzed but found to be less critical. A factory of safety of 1.8 is acceptable for permanent slopes. The maximum refuse fill height and slope for WMU FU-04 should be re-evaluated based on actual CQA direct shear tests results on the base and slope liner interfaces. Because the south slope of WMU FU-04 is a permanent slope, a seismic deformation analysis was performed. The SHAKE computer program was used to predict the response of the landfill to the input base rock motions. To model the dynamic response of the critical cross section, the following columns were used: • 80-feet of soil overlying stiff soils/bedrock. This column was used to calibrate the shear wave velocities assumed for the soil. After the results at ground surface were considered to be reasonable,the refuse was modeled above the soils for the remaining analysis. • 70 and 140 feet of refuse overlying 80 feet of soil overlying stiff soils/bedrock. The accelerations at the ground surface for the soil-only column varied between 0.14g(for Mw 7.9 time history)and 0.21 g(for Mw 6.7 time histories). The accelerations at the ground surface for the refuse-soil column varied between 0.14g and 0.15g(for Mw 7.9 time history)and between 0.20g and 0.308(for Mw 6.7 time histories). The ground accelerations at the top of the soil-refuse columns were equated to ii a,in the Makdisi and Seed (1977) procedure to estimate deformations. The yield acceleration for the critical section is 0.17g. Based on the results of this analysis (see Appendix B), the magnitude of permanent deformation of the slope was estimated to be less than 1-foot during a MCE seismic loading event. As discussed in Section 3.2, while it is difficult to assess what deformation would damage a composite base lining system,the current practice is to limit deformations to less than 12 inches(Sharma and Lewis, 1994).The estimated magnitude of permanent deformation can therefore be considered acceptable.The estimated seismic deformation should be reevaluated following WMU FU-04 construction using actual material properties. FU-04 REPORT.DOC 3-8