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® Conventional static and pseudo-static stability analyses were performed using typical slope stability equations. Geologic conditions modeled by the cover stability analysis were based on information obtained from site-specific documentation and studies of the landfill and professional publications pertaining to regional geologic conditions, laboratory testing on two samples of the proposed borrow cover materials(Appendix B), and typical waste characteristics(Singh, and Murphy, 1990). Based on our assimilation of this information and our previous experience with landfills, the following materials characteristics were used in the stability analyses: Material Unit Weight(pcf) Friction Angle(degrees) Apparent Cohesion(psf) Cover Soils 120 34 100 Refuse(MSW) 80 30 200 The critical(weakest)interface of the landfill cover system is as follows: • Along the cover soils and the MSW. A friction angle of 30 degrees and cohesion of 100 psf was used in the analysis for this interface. Review of the plans by BAS indicates a final cover thickness of 3 feet overlying a one foot ® interim cover,on refuse(MSW). This condition was analyzed in the cover slope stability calculations(Tables 1 through 3). Groundwater was assumed to be below the base of the landfill. CALCULATION RESULTS The following table summarizes the results of the cover stability analyses: Condition Factor of Safety COVER STATIC STABILITY ANALYSIS Cover System—25 feet high slope at 3.2:1 (Table 1) 1.90 Cover System—30 feet high slope at 3.5:1 (Table 2) 2.07 Cover System—36 feet high slope at 3.6:1 (Table 3) 2.13 Cover Soils at an Inclination of 3.2:1-Unsaturated(Table4) 2.31 Cover Soils at an Inclination of 3.2:1-Saturated(Table 5) 1.35 Cover Bench Soils at an Inclination of 2:1 —Unsaturated(Appendix C) 1.92 To evaluate the static stability of the proposed refuse cover system at various design inclinations and slope heights,the proposed cover configuration was analyzed by typical force equations (Tables l through 3). For this case,the soil cohesion was neglected. Static refuse cover slope stability(assuming a failure at the cover/MSW interface) for all three slope inclinations analyzed ® indicates a factor of safety greater than 1.5 (Tables 1 through 3). -2 - C:Active Projects 2005 2005-082 Fonrard LF Cover Slope Stability Analysis Repon.doc Geologic Associates