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12/17/2007 Findings: Implementation of these measures is feasible and would reduce this potential impact to a less-than-significant level. c. Ground Shakina I Liauefaction Potential Impact 11-3: Development of the proposed project would place new residences and businesses in a subregion that is expected to experience severe earthquake- induced ground shaking during the useful life of the project improvements. This ground movement could also cause differential settlement of poorly consolidated soils (including Bay mud) and induce ground failure within alluvial soils that are prone to liquefaction (including some layers below Bay mud). These possible responses to anticipated seismic activity represent a potentially significant impact. Mitigation 11-3: Require that the detailed, design-level geotechnical investigations recommended under Mitigations 11-1 and 11-2 include analysis of project site seismic stability, evaluation of liquefaction potential, and soil response characteristics with respect to ground acceleration. The detailed, design-level geotechnical investigations should include the following: 1. Seismic stability analysis of the existing on-site soil, including fill, Bay mud, and underlying alluvial deposits; 2. Evaluation of liquefaction potential through the performance of additional borings, cone penetration tests, and/or equivalent methods; and 3. Determination of parcel-specific soil response characteristics and maximum credible ground acceleration for an earthquake recurrence interval specified by the City of Redwood City. Recommendations from the investigations, including appropriate soil stabilization and foundation construction techniques, minimum setbacks around potentially unstable areas, and criteria for the compaction and treatment of on-site fills, shall be incorporated into the project grading and foundation plans. In general, these recommendations are expected to include, but not be limited to, the following provisions: 1. Require all construction to comply with the Uniform Building Code (UBC, 2001) for Seismic Zone Factor 4 and Soil Profile Type SE. Base all project designs on estimates of peak and maximum repeatable earthquake-induced ground surface accelerations expected to occur on the project site, as calculated by the project geotechnical investigations. 2. Slope or shore excavations in order to minimize ground movements. Typically, when excavation extends into Bay mud, 4:1 or flatter slopes are required to reduce movements. Findings: Implementation of these measures--combined with conformance with standard Uniform Building Code, City of Redwood City, and other applicable regulations--would reduce the potential effects of ground shaking to a less-than-significant level. Atty/Reso/Reso.1772 121707 35 14829 Muff# 613