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L` 3 STATIC SLOPE STABILITY ANALYSIS The subgrade under the landfill consists of cemented sandy silt and clay soils with layers of gravel. The soils are very hard and extend to significant depths (> 100 feet). Because of the presence of geosynthetic materials within the landfill liner system, the shear strength (internal and interface) of the liner system would be significantly lower than that of the landfill subgrade. Therefore, slope failure surfaces passing through the landfill subgrade will be less critical than those passing through the landfill liner system. Accordingly, the slope stability analyses presented in this report focused on failure surfaces that pass through the liner system and the waste. The proposed base liner system consists of the following components, from top to bottom: • 24 -inch -thick operations soil layer • 8 -ounce per square yard (oz/sy) nonwoven geotextile separator • 9 -inch -thick drainage gravel primary leachate collection and removal system • 60 -mil HDPE primary geomembrane (textured on both sides) • Geosynthetic clay liner (GCL) barrier (in lieu of a 24 -inch -thick low -permeability soil -layer) [Note: Under the leachate sumps, a secondary liner system consisting of a geocomposite drain material and a 60 -mil HDPE geomembrane will also be installed] The proposed sideslope liner system consists of the following components, from top to bottom: • 24 -inch -thick operations soil layer • Primary geocomposite drain material, if the operations layer permeability is insufficient to maintain <1 -foot head • 60 -mil HDPE primary geomembrane (textured on both sides) • GCL barrier (in lieu of a 24 -inch -thick low -permeability soil layer) \\.SACRFPI\COMMON\sacDP\2002\PRJ\PJ8\83\835608.2bz.doc EMCOWOWT, Inc. Rev. 0, 07/31/02 3-1