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SECTION 3 WMU FU-03 Slope Stability In accordance with Title 27 regulations, both static and seismic stability analyses were performed for WMU FU-03. The seismic stability analysis is based on a seismic hazard analysis performed in 2001 (GeoSyntec, 2001). WMU FU-03 will be filled with designated wastes(Class II). Refuse placed on the northern portions of WMU FU-03 will overlay existing municipal solid waste fill (Class III). An interface liner will be placed on the northern slopes to separate the designated and municipal solid wastes. Refuse placed on the western and southern sides of WMU FU-03 will eventually form the final landfill slope and will be constructed at a 3:1 (horizontal:vertical) slope with 20-ft wide benches every 50 vertical feet. The eastern refuse fill slope is temporary and will be constructed at a 3:1 grade. Refuse will be placed against the 3:1 eastern slope once future WMUs to the east of WMU FU-03 are constructed. The following slope stability conditions were considered for the WMU FU-03 design: • WMU FU-03 Final Build Out. This condition represents the maximum fill configuration of WMU FU-03. Due to geometric constraints, the maximum fill elevation in WMU FU-03 prior to the construction of adjacent WMUs is approximately 80 feet. The critical section is through the eastern slope. • Forward Landfill Final Build Out. This condition represents the maximum fill configuration for the landfill once adjacent WMUs have been constructed and the entire landfill is at its maximum fill configuration. The maximum elevation in WMU FU-03 at the final build-out conditions is at an approximately 170-foot elevation. The critical section is through the southern slope. The critical stability configurations were selected based on the Construction Drawings and WMU FU- 03 refuse grading plans in Appendix A and B, respectively. Stability analyses were only performed on the Forward Landfill Final Build Out configuration because this configuration was assessed to be more critical. This assessment was based on the following considerations: • The refuse fill depth for the WMU FU-03 final build out condition (approximately 60 ft) is less than the Forward Landfill final build out condition (approximately 155 ft) • The steepest overall final grades for both the WMU FU-03 and Forward Landfill final build out configurations are approximately the same (3:1). Because benches are incorporated in the final build out configuration, the overall slope is slightly flatter than 3:1, however the much greater depth of refuse fill in the final build-out condition still makes it more critical than the WMU FU-03 condition. • The critical section in the final buildout condition runs north-south through the southern slope. The base grade in this direction is approximately I percent. The critical section in the WMU FU-03 condition runs east-west through the eastern slope. The net grade in this direction is approximately zero due to the chevron pattern of the base. The base grade in the north-south direction (final build-out condition) is steeper than in the east- west direction (WMU FU-03 condition)and,therefore, more critical. FORWARD LANDFILL WMU F-03 AND F-WEST DESIGN REPORT 3-1