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® 70 and 140 feet of refuse overlying 80 feet of soil overlying bedrock/stiff soil. No data are available on site-specific shear-wave velocities for the refuse fill at the Landfill. Because of the heterogeneous nature of refuse, its dynamic material properties have not been clearly defined. GeoSyntec modeled the behavior of refuse based on work by Matasovic and Kavazanjian (1998) at the Operating Industries Inc. (OII) landfill in Southern California. Matasovic and Kavazanjian (1998) developed shear modulus versus strain, and damping versus strain relationships based on analyzing and backcalculating the response of the OU landfill during various earthquakes. The shear wave velocity assumed for the refuse is based on the velocity profile developed at the OH landfill (Idriss et al., 1995) which compares well with the shear wave velocity profile developed by Matasovic and Kavazanjian (1998). For shallow depths, the shear wave velocity compares well with values presented by Sharma et al. (1990). The shear wave velocity used varied between 650 and 970 ft/sec. The unit weight of refuse was assumed to be 75 pcf. The shear wave velocity of the underlying deposits at the site were assumed based on compression wave velocities for soil presented by Spangler and Handy (1982). The shear wave velocities were assumed to vary between 600 and 800 ft/sec. These shear wave velocities were assumed to increase and vary between 800 and 1,200 ft/sec when modeling varying refuse fill heights above the soil. The variations of shear modulus and damping ratios with strain for sand are based on Vucetic and Dobry (1991) for a material having a plasticity index of zero. The depth to bedrock was assumed to be 80 feet below the bottom of the excavation for the cell based on geologic information available for the site. The shear-wave velocity of the bedrock was assumed to be 3,000 ft/sec. The accelerations at the ground surface for the soil-only column varied between 0.148 (for M=7.9 time history) and 0.218 (for M=6.7 time histories) depending on the time history. The accelerations at the ground surface for the refuse-soil column varied between 0.14g and 0.15g (for M=7.9 time history); and between 0.20g and 0.30g (for M=6.7 time histories). The ground accelerations at the top of the refuse-soil columns were then equated to 0", in the Makdisi and Seed (1977) procedure. Using the Makdisi and Seed (1977) procedure, seismic deformations for the MCE were estimated to be less than l foot which is acceptable (Seed and Bonaparte, 1992; Sharma and Lewis, 1994). The complete seismic response analysis, including output from the SHAKE analysis, is attached.