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SECTION 3 Slope Stability In accordance with Title 27 regulations, static stability analyses were performed for WMU FU-14. Seismic stability analyses were not performed because WNW FU-14 is an interior module and the interim refuse fill slopes will not coincide with the final landfill grades. Seismic stability analyses are typically only performed for slopes that will become part of the final cover of the landfill. Refuse placed on the northern and western sides WMU FU-14 will be placed against waste in WMU FU-10 and WMU FU-13, forming a contiguous mass. Stability analyses for WMU FU-10 and WMU FU-13 are documented in the Design and Construction Documents, WMU FU-10, Forward Landfill (Lewis Engineering 20 10) and Design and Construction Documents, WMUFU--13, Forward Landfill (Lewis Engineering 2013), respectively. The eastern and southern refuse fill slopes of WMU FU-14 are temporary and will be constructed at a 3:1 grade. Refuse will be placed against the 3:1 eastern and southern slopes once future WMUs to the east and south of WMU FU-14 are constructed. Based on the geometry, construction against adjacent WMUs, and site development plans, the planned refuse fill elevation in WMU FU-14 is approximately 150-feet. The critical stability configuration was selected based on the Construction Drawings and WMU FU- 14 refuse grading plans.The critical section was determined to be the east-west section. 3.1 Analytical Method The slope stability analyses were performed using the computer program XSTABL. The program calculates slope stability using a limit equilibrium analysis based on the method of slices.The method of slices estimates slope stability by assuming a shear surface and calculating the forces that would cause slope movement, and the forces resisting slope movement for the selected shear surface. The ratio of available shear strength (resisting forces) to mobilized shear strength (driving forces) is known as the factor of safety. The computer programs employ a searching routine to determine the critical shear surface with the minimum factor of safety. A factor of safety equal to 1.0 under static loading conditions represents a condition of imminent failure. For temporary slopes, such as those in WMU FU-14, a minimum factor of safety of 1.3 under static loading conditions is considered acceptable. 3.2 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. 3.2.1 Material Properties The single-composite lining system for the WMU FU-14 base will consist of a 2-foot thick clay liner overlain by a double-sided textured HDPE geomembrane, cushion geotextile, and granular blanket LCRS. Material properties used 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. WMU FU-14 REPORT.DOC 3-1