ARCHIVED REPORTS LEC APPLICATION FOR CERTIFICATION

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5.4 GEOLOGIC HAZARDS AND RESOURCES 5.4.1.5.2 Seismic Shaking The project area has experienced seismic activity with strong ground motion during past earthquakes, and it is likely that strong earthquakes causing seismic shaking will occur in the future. The significant geologic hazard at the LEC site is strong ground shaking due to an earthquake. Ground shaking from a magnitude 7.3 earthquake could occur within approximately 50 mile radius of the site (Blake,2004). The controlling fault for the LEC site is Segment 5 of the Great Valley Fault,located approximately 20 miles west of the site. This is a reverse-type fault dipping approximately 15 degrees west with a slip rate of approximately 1.5 millimeters per year (CGS,2002) and is capable of generating a peak bedrock acceleration(PBA) at the site of 0.118 (Blake,2004) based on the MCE event. Other faults within a 50-mile radius of the LEC site are capable of generating a PBA range of 0.04g to 0.10g (Blake,2004). These PBA estimates are based on assuming an attenuation relationship by Boore et al (1997) for a rock outcrop. 5.4.1.5.3 Liquefaction During strong ground earthquake,loose, saturated,cohesionless soils can experience a temporary loss of shear strength and act as a fluid. This phenomenon is known as liquefaction. Liquefaction is dependent on the depth to groundwater, grain size distribution, relative density of the soils, degree of saturation, and intensity and duration of the earthquake. The potential hazard associated with liquefaction is seismically induced settlement. The static groundwater depth at the time of a recent geotechnical feasibility study conducted by Carlton Engineering, Inc. (Carlton,2008)was approximately 10 feet below ground surface at the project site. A copy of the geotechnical report is provided in Appendix 2C. The soil units below groundwater consist of isolated pockets of loose,near- surface, sandy soils. Therefore,the likelihood that liquefaction will occur is considered moderate. 5.4.1.5.4 Mass Wasting Mass wasting depends on steepness of the slope,underlying geology, surface soil strength, and moisture in the soil. Significant excavating, grading, or fill work during construction might introduce mass wasting hazards at the project site. Because the site is relatively flat and no significant excavation is planned during site construction,the potential for direct impact from mass wasting at the site is considered low to negligible. 5.4.1.5.5 Subsidence Subsidence can be a natural or man-made phenomenon resulting from tectonic movement, consolidation,fluid removal (oil, gas,or water), or rapid sedimentation or oxidation of organic-rich soil. The Delta has had a history of subsidence,but the majority of the Delta's subsidence has been on the west end where subsidence greater than 15 feet has been noted (USGS,2000). On the eastern end of the Delta, subsidence is typically less (0 to 10 feet range) (USGS,2000). At the LEC site, organic soils with significant collapse potential were not encountered during the geotechnical feasibility study of the site (Carlton,2008). Also, subsidence has not been identified as a geologic hazard at the site according to the seismic and geological hazards section of the San Joaquin County General Plan. (San Joaquin, 1992). The potential for subsidence as a hazard that could affect the project site is considered low. SAC/371322/082330011(LEC-5.4-GEOLOGIC HAZARDS AND RESOURCES.DOC) 5.4-7