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are determined, horizontal displacements at each layer are calculated using the closed-form wave equation. The SHAKE computer program uses these displacements to calculate the accelerations at the top of each layer. The ground accelerations at the top of the refuse-soil columns were then equated to umax in the Makdisi and Seed (1977) procedure. Deformations are estimated using the "Newmark" chart developed by Makdisi and Seed(1977). SHAKE requires unit weight, shear-wave velocity, and shear modulus and damping characteristics to be input for each soil layer. Design earthquake motion is input as an acceleration-versus-time record. When evaluating the results of a seismic deformation analysis, the effect of the net slope movement should be considered. The most severe consequence of slope movement would be damage to the composite base lining or LCRS of the landfill. While it is difficult to assess what deformation would damage a composite base lining system, the current practice is to limit deformations to 30 cm(1 foot) or less(Sharma and Lewis, 1994). 3.3 Stability Analysis The stability analyses are based on several measured and assumed material properties. The material properties used in the analyses and the results of the analyses are presented below. Calculations are included in Appendix B. 3.3.1 Material Properties The single-composite lining system for the central portion of the WMU FU-04 base will consist of a 2-foot thick clay liner overlain by an HDPE geomembrane, cushion geotextile, and granular blanket LCRS. The lining system on the excavated southern slope will consist of a geosynthetic clay liner (GCL) overlain by an HDPE geomembrane and a geocomposite drainage net (GDN). The HDPE geomembrane will be double sided textured on the base and single-sided textured on the slope, with the textured side placed against the GCL. The GDN will have a nonwoven geotextile bonded to one side of the geonet. The geonet side will be placed against the smooth side of the HDPE geomembrane. This same lining system will be used as an interface liner on the northern slope in the central portion and in the northwestern portion of WMU FU-04. Material properties for use in the stability analyses were based on actual test data from previous WMUs constructed at the site and a review of published values in the literature. Table 3-1 presents the assumed material properties used in the stability analysis. The interface shear strength for the base lining system in the central portion of WMU FU-04 was estimated using laboratory testing performed for the construction of the WMUs D-95, D-97, D-98, D- 99, D-00, D-01, D-02, and FU-03 lining systems (CH2M HILL 1995b and 1997c, Vector 1999a and 1999b, EMCON/OWT 2000, Holdredge and Kull 2001, Vector 2002, Vector 2003). These interface shear strength results were assumed to be representative of those in WMU FU-04 because WMU FU- 04 will be constructed using onsite soils and geosynthetic materials very similar to those used in these previously constructed WMUs. The interface shear strength properties used for the side slope liners were estimated using laboratory testing performed for the construction of WMUs D-97, D-98, D-00, D-01, D-02, and FU-03 (CH2M HILL 1997c, Vector 1999a, EMCON/OWT 2000, Holdredge and Kull 2001, Vector 2002, Vector 2003).These interface shear strength results were assumed to be representative of those in WMU FU- 04 because the same combination of materials was used in these previously constructed WMUs. FU-04 REPORT.DOC 3-4