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SECTION 3 Slope Stability In accordance with Title 27 regulations, both static and seismic stability analyses were performed for WMU FU-04. The seismic stability analysis is based on a seismic hazard analysis performed in 2001 (GeoSyntec,2001). WMU FU-04 will be filled with designated wastes (Class II) in the central and northwestern portions and municipal solid wastes(Class III) in the northeastern portion. Refuse placed in portions of WMU FU-04 will overlie existing municipal solid waste fill (Class III). Interface liners will be placed in these areas to separate the designated and municipal solid wastes. Refuse placed on the southern side of the central portion and on the northern side of the northeastern portion of WMU FU-04 will eventually form the final landfill slopes and will be constructed at a 3:1 (horizontal:vertical) slope with 20-ft wide benches every 50 vertical feet. The eastern refuse fill slopes are 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 western slopes will filled against existing refuse slopes. The following slope stability conditions were considered for the WMU FU-04 design: • WMU FU-04 Central Portion. This condition represents the maximum fill configuration of the central portion of WMU FU-04. Based on the geometry and construction against adjacent WMUs, the maximum fill elevation in the central portion of WMU FU-04, prior to the construction of adjacent WMUs, is approximately 150-feet. The critical section is through the eastern slope. • WMU FU-04 Northeastern Portion. This condition represents the maximum fill configuration of WMU FU-04 in the northeastern portion. Based on the geometry and construction against adjacent WMUs, the maximum fill elevation in northeastern portion of WMU FU-04 is approximately 150-feet. The critical section is through the southern slope. • Forward Landfill Final Grades. 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-04 at the final grade condition 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- 04 refuse grading plans in Appendix A and B,respectively. The internal stability of the interface and side slope lining system was also considered. The GCL, HDPE geomembrane, and GDN will be placed on a maximum 2:1 slope. A protective operations soil layer will be placed against the slope as WMU FU-04 filling operations progress (i.e., the operations layer will not be"hung"on the side slope). To minimize interface liner loads, it was assumed that the operations layer would be placed up to a maximum height of 10 feet above the refuse fill level using a wheel loader2. Minimal equipment loads will, therefore, be applied to the slope. To maintain the 2 Based on information provided by Butch Stefani(Site Manager at the Forward, Inc.Landfill),the protective operations layer will be placed on the WMU D-02 slope using a Caterpillar 966F Series Wheel Loader with a 4.5 cy bucket. FU-04 REPORT.DOC 3-1