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Potentially Potentially Significant unless Less than Significant Mitigation Significant No Impact Incorporated Impact Impact iii) Seismic-related ground failure, including 0 0 ~ 0 liquefaction? iv) Landslides? 0 0 0 ~ b) Result in substantial soil erosion or the loss of 0 ~ 0 0 topsoil? c) Be located on a geologic unit or soil that is unstable, 0 0 [gJ 0 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? . d) Be located on expansive soil, as defmed in Table 18- 0 0 0 [gJ loB of the Uniform Building Code (1994), creating substantial risks to life or property? e) Have soils incapable of adequately supporting the use 0 0 0 ~ of septic tanks or alternative waste water disposal systems where sewers are not available for the disposal of waste water? DISCUSSION: Based on U.S. Geological Survey mapping, the site is underlain by estuarine bay mud deposits, consisting of unconsolidated water-saturated dark plastic carbonaceous clay and silty clay (Helley and Lajoie, 1979). Site-specific investigation indicates that, in areas where fill is present, the fill ranges in thickness from 12 to 25 feet (3.7 to 7.2 meters) and consists of sand and gravel with pieces of concrete. The fill layer is underlain by a 6- to lO-foot (1.8- to 3.1-meter) thick layer of soft, high plasticity silty clay (Younger Bay Mud). The Younger Bay Mud is underlain by interbedded layers of medium stiff to very stiff silty clay and loose to medium dense clayey and silty sand to the maximum depth explored (about 80 feet or 24.4 meters) (Parikh, 2004). The entire San Francisco Bay Area is located in a region of active seismicity. The seismicity of the region is primarily related to the San Andreas Fault Zone (SAFZ). The SAFZ is a complex of active faults forming the boundary between the North American and the Pacific lithospheric plates. Historically, numerous moderate to strong earthquakes have been generated in northern California by several major faults and fault zones in the SAFZ system. The Hayward Fault, which is located about three miles to the east, is the nearest major seismic source for the project site. The site-specific geotechnical report indicates that the fault is capable of generating a moment magnitude 7.5 earthquake with a peak bedrock acceleration of 0.57 g (Parikh, 2004). Ground shaking at the site during a magnitude (M) 6.9 earthquake on the Hayward Fault would be expected to be "violent" (Modified Merca1li Intensity IX) (ABAG, 2004). No known active faults cross the site and therefore fault rupture is not expected to occur at the site. The project will likely experience moderate to strong ground shaking sometime during its design life. It is considered unlikely that a moderate to large earthquake would occur during construc.tion. Y 4204IS.00693.doc - 4/5107 -21-