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Draft Environmental P Impact Report Page 12 Forward Landfill Expansion Impacts and Mitigation Measures Standards of Significance Criteria for determining significant impacts are based upon the CEQA Guidelines (Appendix G) and professional judgment. These guidelines state that the project would have a significant impact on geology, soils,or seismicity if it would: • Expose people or structures to potential substantial adverse effects, including the risk of loss,injury, or death involving: - Rupture of a known earthquake fault, as delineated on the most recent Alquist-Priolo Earthquake Fault Zoning Map issued by the State Geologist for the area or based on other substantial evidence of a known fault -Strong seismic ground shaking -.Seismic-related ground failure,including liquefaction - Landslides • Substantially alter a unique geologic feature • Result in substantial soil erosion or the loss of topsoil • Be located on a geologic unit or soil that is unstable, or that would become unstable as a result of the project, and potentially result in on- or off-site landslide, lateral spreading, subsidence,liquefaction or collapse • Be located on expansive soil, as defined in Table 18-1-B of the Uniform Building Code (1994), creating substantial risks to life or property. Impact G.1: Because soil within the project site expansion areas would be inadequate—in quantity and possibly quality---to meet the required soil for demands of the daily,intermediate,and final cover over the duration of the project,soil would need to be imported. Using the 6:1 (horizontal to vertical)refuse to soil ratio sites by the design criteria, approximately 2.2 million cubic yards (mcy) of new soil needed for import or borrow material.The estimated total available on-site sol available in the new expansion areas is approximately 4.5 mcy, while a total of about 6.7 mcy is projected to be needed for on-site cover at the 6:1 refuse to soil ratio referenced in the JTD (2007). The following procedure is proposed as part of the project: • Additional cover material needed for alternative daily covers, approved by the CIWMB, will be imported from approved borrow material locations. Use of approved alternative covers would reduce this impact to a less-than-significant level. Mitigation Measure G_1. None required. Impact G.2: Seismic shaking could impair or otherwise compromise both the existing and proposed (for the new expansion areas) Class II liner and associated leachate collection system integrity, causing slope instability, damage to drainage features, or differential settlement of the landfill over the life of the project,or following closure.