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City of San Leandro <br />2824 Halcyon Drive Residential Project <br /> <br />52 <br />a.3. Would the project expose people or structures to potential substantial adverse effects, <br />including the risk of loss, injury, or death involving seismic-related ground failure, including <br />liquefaction? <br />c. Would the project be located on a geologic unit or soil that is made unstable as a result of the <br />project, and potentially result in on or offsite landslide, lateral spreading, subsidence, <br />liquefaction, or collapse? <br />Liquefaction of soil can occur during seismic ground-shaking. Loose, saturated, uniformly graded <br />sand below the groundwater table is the soil type most susceptible to liquefaction. Silt and clay with <br />low plasticity are also potentially liquefiable. As shown in Figure 7-2 of the City General Plan, the <br />project site is within a moderate liquefaction susceptibility zone (City of San Leandro 2016a). The <br />geotechnical investigation concluded that a liquefaction induced settlement of up to approximately <br />2.5 inches may occur and a differential settlement of 1.25 inches over 50 feet is estimated. Due to <br />the presence of a thick predominantly non-liquefiable cover overlaying potentially liquefiable layers, <br />surface manifestations of liquefaction to differential settlements would be limited (Appendix GEO). <br />Project design that complies with the CBC as well as recommendations listed in the Geotechnical <br />report (Appendix GEO) would result in a building that resists adverse effects from seismic-related <br />liquefaction. Therefore, hazards associated with seismic ground failure, including liquefaction, <br />would have less than significant impacts. <br />a.4. Would the project expose people or structures to potential substantial adverse effects, <br />including the risk of loss, injury, or death involving landslides? <br />Due to the prevailing gentle topography of the city, the probability of earthquake-induced landslides <br />in most parts of San Leandro is low except for the hills in the northeast part of the city (City of San <br />Leandro 2016a). The risk for landslides in the area is so low the California Geological Survey Seismic <br />Hazard Zones Map for the San Leandro 7.5-Minute Quadrangle excludes the site from areas mapped <br />for landslide hazards (Appendix GEO). In addition, the project would be required to comply with <br />recommendations listed in the Geotechnical report (Appendix GEO) which would reduce impacts <br />from landslides. Therefore, risks associated with earthquake-induced landslides at the project site <br />would be less than significant. <br />b. Would the project result in substantial soil erosion or the loss of topsoil? <br />Site preparation and grading would expose soils, which would result in the potential for erosion; <br />however, the generally level conditions of the project site would limit the potential for substantial <br />soil erosion and adherence with C.3 requirements would minimize erosion of soils and pollutants <br />into stormwater runoff (Refer to Section 10, Hydrology and Water Quality, for more detail about <br />stormwater runoff). Ground-disturbing activities would include site-specific grading for foundations, <br />building pads, access driveways and parking, and utility trenches. Although temporary erosion could <br />occur, the project would be required to comply with SLMC Section 7.12.230 as well as <br />recommendations listed in the Geotechnical report (Appendix GEO) which would ensure <br />stormwater, erosion, and sedimentation control measures would be taken to prevent excess <br />stormwater runoff and minimize erosion and sedimentation. Compliance with SLMC Section <br />7.12.230 and recommendations in the Geotechnical report would reduce impacts to a less than <br />significant level.