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. 7C <br /> Page 56 <br /> Findings: Implementation of these measures is feasibfe and wauld reduce this <br /> poten#ial impact to a less-than-signi�canf leve►. <br /> C. Ground ShakinQ /Liauefaction <br /> Patential lmpact 11-3: Development of the proposed project would ptace new. <br /> residences and businesses in a subregion that is expected to experience severe earthquake- <br /> induced ground shaking during the useful life of the project improvements. This graund <br /> movement cauld also cause differential settlement of poorly consolidated soils (including Bay <br /> mud)and induce ground failure within alluvial soiis that are prone to liquefiaction (including some <br /> layers below Bay mud). These possible responses to anticipated seismic activity represent a <br /> potenfially sign�cant impacf. <br /> Mitigation 11-3: Require that the detailed, design-level geotechnical <br /> investigations recommended under Mrfigafions 11-1 and 17-2 include analysis of project site <br /> seismic stability, ev�ivatic�rr n#fiquefactifln pofeniiai, and soil response characteristics wit� <br /> respect to ground acceleration. <br /> The detailed, design-level geotechnical investigations should include the <br /> fol{owing: <br /> 1. Seismic stability analysis of the existing on-site soil, including fill, Bay mud, <br /> and underlying alluvial deposits; <br /> 2. Evaluation of liquefaction potential through the performance of additional <br /> borings, cone penetration tests, and/or equivalent methads; and <br /> 3. Determina#ion of parcel-specific soil response characteristics and maximum <br /> credible ground acceleration for an earthquake recurrence interval specified <br /> by the City of Redwood City. <br /> Recommendations from the investigations, including appropriate soil s#abilization <br /> and faundation construction techniques, minimum setbacks araund potentially unstabfe areas, <br /> and criteria for the compaction and treatment of on-site flls, shall be incorparated into the <br /> project grading and foundatian plans. In general, these recommendations are expected to <br /> include, but nat be limited to, the foilowing provisions: <br /> 1. Require all construction to compfy with the Uniforrn Buiiding Code (UBC, <br /> 20Q1)for Seismic Zone Factor 4 and Soil Profile Type S�. Base afi project <br /> designs on estimates of peak and maximum repeatable earthquake-induced <br /> ground surface accelerations expected to occur on the project site, as <br /> calcu(ated by the project geotechnical investigations. <br /> 2. Slope or share excavations in order to minimize ground movements. <br /> Typicakly, when excavation extends into Bay mud, 4:1 or flaiter siopes are <br /> � required fa reduce movemen#s. <br /> Findings: Irnplementatian of these measures--combined with conformance with <br /> standarci Uniform Building Code, City of Redwood City, and other appiicabie regulatians--would <br /> reduce the potential effects of ground shaking to a /ess-than-signiticantlevel. <br /> AttylResolReso.1772 3� <br /> 121307 <br />