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A target acceleration response spectral envelope was developed for each of the MCE/MPE candidate events using the median and 84'" percentile acceleration response spectra evaluated using the Abrahamson and Silva [1997] attenuation model. Based upon the target significant duration of strong ground shaking and acceleration response spectral envelope for each candidate event, the following four time histories were selected to represent ground motions at hypothetical bedrock outcrop at the site: The 270-degree component of the Saratoga-Aloha Avenue record from the Mme.6.9 Loma Prieta earthquake, scaled to either 0.19 g to represent the NICE or to 0.13 g to represent the MPE; The 315-degree component of the Santa Teresa Hills record from the M,6.9 Loma Prieta earthquake, scaled to either 0.19 g to represent the NICE or to 0.13 g to represent the MPE; The 360-degree component of the Corrahtos-Eureka Canyon Road record from the Mw. 6.9 Loma Prieta earthquake,scaled to either 0.19 g to represent the NICE or to 0.13 g to represent the MPE; and The Magnitude 8+synthetic accelerogram generated by Seed and Idriss [1969] to simulate distant large-magnitude event on the San Andreas fault, scaled to 0.10 g to represent both the MCE and MPE. 3.2 Analytical Method The slope stability analysis was performed using the computer program SLOPEW. SLOPEW calculates slope stability using a limit equilibrium analysis based on the method of slices. The method of slices estimates slope stability by assuming a shear surface and calculating the forces that would cause slope movement, and the forces resisting slope movement for the selected shear surface. The ratio of available shear strength (resisting forces) to mobilized shear strength (driving forces) is known as the factor of safety. SLOPEW employs a searching routine to determine the critical shear surface with the minimum factor of safety. A factor of safety equal to 1.0 under static loading conditions represents a condition of imminent failure. For temporary slopes, a minimum factor of safety of 13 under static loading conditions is generally considered adequate. Permanent slopes are typically designed to achieve a minimum static factor of safety of 1.5. During a seismic event, the propagation of bedrock motions induces a sequence of cyclic shear stresses on the soil and refuse. These cyclic shear stresses result in cyclic strains. When the stresses are above yield, a certain amount of strain remains, which produces permanent seismic deformations in the soil or refuse. To estimate these seismic deformations, a procedure based on the concept proposed by Newmark(1965)for calculating seismic permanent deformations and refined by Makdisi and Seed(1978)was used. The method assumes that failure occurs on a well-defined slip surface and that the material behaves elastically at stress levels below failure, but develops a plastic behavior above yield. When the maximum, average acceleration in the potential sliding mass (k,,,a,) exceeds the calculated yield acceleration for each sliding surface (ky), movements are assumed to occur along the direction of the failure plane. The ky is the seismic coefficient that results in a factor of safety of 1.0. The overall deformation is obtained by summing the strains over the failure surface. The strains are estimated based on a time-step finite-element analysis using the equivalent linear method (Seed et al., 1973). FORWARD LANDFILL WMU F-03 AND F-WEST DESIGN REPORT 3-3