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III. Environmental Setting, Impacts,and Mitigations J. Geology,Soils and Seismicity Mitigation Measure J.3. Identified by this EIR Should additional cover material be needed,alternative daily covers should be examined and used. Use of approved alternative covers would reduce this potentially significant impact on soils to a less-than-significant level. Impact J.4. Seismic shaking could disturb slope stability,drainage features,linear integrity,and settlement of the landfill,over the life of the project or after closure. (SIGNIFICANT) Kleinfelder,using the Seed and Idriss method,concludes that there is a potential site maximum peak bedrock acceleration of 0.18 g,based on a Richter Magnitude 7.0 earthquake, 24 miles from the site on the Midland Fault Zone,although the probability of such an event is considered low (see activity status in Table III.J.2) (Kleinfelder, 1988). The seismic stability analyzed for the project design assumed a slope configuration of 3:1 above ground and varied soil properties (five soil units: 2 to 3 foot clay cap;waste material and soil;clay silt and interlayered clayey,silty fine sand; and silty clay). The effect of groundshaking was made by applying a seismic load of 0.2g , and the resultant factor of safety of 1.6. Herzog indicates that the seismicity and faulting MCE and peak ground acceleration should include all active faults within the area as well as groundshaking from earthquakes which occur along the eastern front of the Diablo Range(Coast Range Bounding Fault) (R.W. Beck and Associates, 1992). Given the historical earthquake events that may have had local epicenters,it is possible that the selected design peak acceleration is not representative of the seismic hazard on the site. If so,seismic stability of the proposed liner,fill surfaces and cover may not be ensured and a failure could be induced by seismic activity. If slope failures,damage to the liner,leachate system and/or drainage facilities occurred,significant impacts to erosion and sedimentation, and water quality could occur. Mitigation Measure J.4. Identified by JWs EIR (a) The project sponsor should prepare an estimate of the maximum peak ground acceleration that would be expected from a small magnitude,but local quake(similar to the historic events that may have been centered near Linden). If the potential maximum peak ground III.J.13