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the cover liner system over the impermeable geomembrane. The GDN is the drainage layer, which is designed to allow water to rapidly migrate out of the cover section and thereby reduce the presence of pore water and its detrimental effects. According to Othman et al. (1995), if an effective drainage layer is incorporated into the cover system, the effects of water flow above the geomembrane can be considered negligible, and a stability analysis only considering the drained condition of the slope is adequate. 3.3 Seismic Screening Analysis ' 3.3.1 Seismic Hazard Evaluation As noted previously, Shaw performed a site-specific seismic hazard evaluation (Attachment 1). This report provides the magnitude of the MPEs and their corresponding PGA values for faults that may impact this site. The following MPE event is more critical than others for this site: ' 1. An MPE of moment magnitude 6.9 along the Coast Range Central Valley fault, segment 7 (GV7) located at a distance of 1.2 kilometers producing a peak ground acceleration(PGA) in rock of 0.56g at the site. The MPE on the GV7 fault is expected to influence the landfill stability more than any of the other faults noted in the seismic characterization report. Therefore, a PGA in rock equal to 0.56g has been used for the seismic slope stability analysis. As noted in the seismic characterization report, the PGA used for this stability analysis is assumed to be very conservative. The conservative nature of the PGA is a result of its development using what the USGS has defined as the maximum magnitude event from the seismogenic source. 3.3.2 Seismic Screening Analysis The same area analyzed for the static condition was also analyzed in the seismic ' screening analysis. Seismic screening, or pseudo-static, analyses apply a constant horizontal acceleration of 0.75 x PGA (Bray et al., 1998)which represents a conservative approach for simplified seismic slope stability. The acceleration for these analyses is 0.75 x 0.56g = 0.42g. Per Title 27 CCR, if the pseudo-static factor of safety is less than 1.5, rigorous analyses must be performed to estimate the potential for permanent ' displacement. The results of the seismic screening analysis is presented in Calculation 2. 3.3.3 Yield Acceleration The yield acceleration is the average horizontal acceleration value within the critical failure surface that results in a pseudo-static factor of safety of 1. Based on Newmark (1965), if the maximum value of the averaged accelerations induced within the critical slopes (often referred to as the seismic coefficient or kora,) exceeds the yield acceleration value, the potential exists for permanent displacement along the critical failure surface. The yield acceleration for the area analyzed does not exceed the estimated PGA for the Landfill. This indicates that permanent seismic displacement during a MW = 6.9 event Slope Stability Analysis Corral Hollow Landfill—Rev 2 512012012 5