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® STABILITY ANALYSIS WMU FU-13,FORWARD LANDFILL PROBLEM: Assess the static stability of the refuse over the base and side slope lining system for WMU FU-13 at the Forward Landfill. Because WMU FU-13 is an interior module,there are no slope 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-13 is similar to WMUs FU-03,ART-03,FU-04,FU-05,FU-06,FU-08,FU-10 and various other WMUs at the site. SUMMARY: 1. The planned maximum elevation of refuse in WMU FU-13,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 is filled against an existing refuse slope. The north slope is filled against the southern slope of the former Austin Road Landfill. 2. Development is planned to the east and south of WMU FU-13. 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 (refuse fill elevation 150 ft)is in the NW-SE direction along the northern slope and base of the cell. 2. For interim slopes,a static factor of safety of 1.2 to 1.3 is acceptable. SUMMARY OF STABILITY ANALYSIS RESULTS 1. The minimum factor of safety for WMU FU-13 under the planned interim fill configuration(refuse elev. 150 ft)is 1.36. The critical failure surface extends from approximately the crest of refuse, through the refuse mass,and then along a portion of the base and slope liner. 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