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STABILITY ANALYSIS WMU FU -14 FORWARD LANDFILL PROBLEM: Assess the static stability of the refuse over the base and side slope lining system for WMU FU -14 at the Forward Landfill. Because WMU FU -14 is an interior module, there are no slopes on this module that will coincide with the final landfill grades. Seismic analyses are, therefore, not required. GIVEN: These calculations have been previously performed for the prior WMUs at the site and they have been found to have a satisfactory factor of safety and seismic deformation. The analysis for WMU FU -14 is similar to WMUs FU -03, ART -03, FU -04, FU -05, FU -06, FU -08, FU -10, FU -13 and various other WMUs at the site. 1. The planned maximum elevation of refuse in WMU FU -14, prior to the development of adjacent waste management units, is 150 ft MSL. This elevation is based on 3:1 slopes on the south and east. The west slope will be filled against the existing WMU FU -10 refuse slope. The north slope will be filled against the existing WMU FU -13 refuse slope. 2. Development is planned to the east and south of WMU FU -14. These slopes are, therefore, temporary and will eventually be buttressed by adjacent slopes. STABILITY ANALYSIS SECTIONS AND CRITERIA: 1. The critical cross section for the stability analysis under the maximum interim filling configuration 0 (refuse fill elevation 150 ft) is in the E -W direction along the base liner. 2. For interim slopes, a static factor of safety of 1.3 is typically considered acceptable. SUMMARY OF STABILITY ANALYSIS RESULTS 1. The minimum factor of safety for WMU FU -14 under the planned interim fill configuration (refuse elev. 150 ft) is 1.57. The critical failure surface extends from approximately the crest of refuse, through the refuse mass, and then along a portion of the base liner, daylighting at the toe of slope. Both the base liner interfaces (clay/HDPE and cushion geotextile/HDPE) were analyzed but the cushion geotextile/HDPE condition was found to be more critical. 2. The stability analysis assumes the base liner interface shear strengths between the clay and textured HDPE are a friction angle of 18 degrees and an apparent cohesion of 0 psf and a friction angle of 10 degrees and an apparent cohesion of 1,000 psf for normal load ranges from 0 to 6,500 psf and from 6,500 to 17,000 psf, respectively. The base liner interface strength between the cushion geotextile and the textured HDPE geomembrane is as follows: Normal Stress (psf) Minimum Shear Stress (psf) 2,000 700 4,000 1,110 8,000 1,950 12,000 2,780 The interface shear strength envelopes for the critical surfaces are included with the calculations.