AgdaPkt 2017-09-11 Closed and Joint SA PFA

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7.A. - Page 66 LSA ASSOCIATES, INC. ROCKETSHIP REDWOOD CITY ELEMENTARY SCHOOL PROJECT SEPTEMBER 2016 INITIAL STUDY/MITIGATED NEGATIVE DECLARATION percent along the Calaveras Fault.35 Therefore,the redevelopment of the project site would expose people and structures to risk from ground shaking. The risk of ground shaking impacts is reduced through adherence to the design and materials standards set forth in building codes. Both the City of Redwood City36 and County of San Mateo37 require projects to comply with the 2013 California Building Code(Title 24,California Code of Regulations),which provides for stringent construction requirements on projects in areas of high seismic risk based on numerous inter-related factors. It is acknowledged that seismic hazards cannot be completely eliminated,even with implementation of advanced building practices. However,the seismic design standards of the California Building Code are intended to prevent catastrophic building failure in the most severe earthquakes currently anticipated. Therefore,compliance with the 2013 (or the most recent)California Building Code,which is required by both the City and the County,would ensure that the potential impacts associated with ground shaking would be less than significant. Seismic-Related Ground Failure and Liquefaction.The potential for different types of ground failure to occur during a seismic event is discussed below. Liquefaction and Lateral Spreading. Soil liquefaction is a phenomenon primarily associated with saturated soil layers located close to the ground surface. These soils lose strength during ground shaking. Due to the loss of strength,the soil may move both horizontally and vertically. In areas where sloping ground or open slope faces are present,this mobility can result in lateral spreading. Soils that are most susceptible to liquefaction are clean,loose,uniformly graded, saturated, fine- grained sands that are relatively close to the ground surface.However,loose sands that contain a significant amount of fines (silt and clay)may also liquefy. The project site is located in an area that has been identified as being susceptible to seismically- induced liquefaction.3s,39 Both the City of Redwood City40 and County of San Mateo41 require projects to complete a geotechnical investigation in areas with potential geological hazards. The site- specific Geotechnical Investigation prepared for the proposed project confirms that there is a potential for liquefaction to occur at the project site during a seismic event. However,the potential for lateral spreading to occur at the site is considered low because the project site and surrounding areas are level or gently sloped,and there are no open slope faces at or near the project site. It is estimated that, during a seismic event,liquefaction-induced ground settlement would be about 1 inch,resulting in differential settlement of up to 2/3-inch over a horizontal distance of 20 feet. The Geotechnical 35 United States Geological Survey,2008.Forecasting California's Earthquakes—What Can We Expect in the Next 30 Years, USGS Fact Sheet 2008-3027.Website:p1bs.uses.eov/fs/2008/3027. 36 Redwood City,City of,Code of Ordinances,Chapter 9,Article N. 37 San Mateo,County of,Building Regulations,Chapter 3,Article 1. 38 Redwood City,City of,2010.Redwood City General Plan-Public Safety Element,Figure PS-3. 39 California Department of Conservation,2006.Seismic Hazard Zones,Palo Alto Quadrangle.Website: www.quake.ca.eov/giumaps/WH/re atong aps.htm. 40 Redwood City,City of,2010.Redwood City General Plan-Public Safety Element,Program PS-24. 41 San Mateo,County of, 1986.San Mateo County General Plan—Geotechnical Hazard Policies,Policy 15.21. P:1RWC1401B Rocketship Sch-I\PRODUCrSUS-MNDTublic\Ra ketship Public Review 09-29-16.docx(09/29/16)PUBLIC REVIEW DRAFT 42 ATTY/RESO.0084/CC RESO ADOPTING CEQA-ROCKETSHIP CHARTER SCHOOL APPEAL REV:09-05-17 VR Page 50 of 124