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SAN LEANDRO SHORELINE DEVELOPMENT DRAFT EIR <br />CITY OF SAN LEANDRO <br />GEOLOGY, SOILS, AND SEISMICITY <br />control erosion. Typically, erosion impacts are greatest in the first two years after construction, the time <br />generally required to reestablish a good vegetation cover on areas of disturbed soil. <br />Coastal Erosion <br />The San Leandro shoreline is exposed to wave attack. The coastline within the vicinity of the Project site is <br />armored with rip -rap to control erosion. No areas of significant coastal erosion were observed within the <br />Project site. The existing erosion protection may require periodic maintenance to maintain effective <br />erosion control. <br />Impact GEO-2: The Project could result in substantial soil erosion or the loss of topsoil. <br />Mitigation Measure GEO-2A: The Project civil engineer shall prepare an erosion control plan. The <br />erosion control plan shall be submitted to the City as a part of building and/or grading plan submittal. <br />The erosion control plan shall conform to the guidelines of the Clean Water Program and Utilize BMP's <br />detailed under section "C6 CASQA - BMPs Erosion Control" of the Program Resources. <br />Mitigation Measure GEO-2B: The existing rip -rap providing coastal erosion protection shall be <br />periodically refurbished to maintain effective erosion control. This may include local replacement of <br />rip -rap boulders as well as periodic re -building of rip -rap armament sections degraded by wave attack <br />and/or long-term erosion. <br />Significance After Mitigation: Less than significant. <br />GEO-3 The Project could result in a significant impact related to development <br />on unstable geologic units and soils or result in lateral spreading, <br />subsidence, liquefaction, or collapse. <br />Liquefaction <br />Given the Project site is located in a seismically active region, future earthquakes are likely during the life <br />of the Project and the risk of liquefaction could be significant. <br />Potential liquefaction at the Project site would likely be settlement of the ground surface and the localized <br />expulsion of sand and water onto the ground surface (i.e., sand boils). Liquefaction could also result in <br />excessive settlement of improperly designed foundations and possibly lateral spreading (the lateral <br />spreading hazard to be discussed in subsequent section). Depending on the amount of ground or <br />foundation settlement, damage to the planned buildings could be moderate. Other areas such as parking <br />lots and landscape areas could also undergo settlement and ground deformation as a result of <br />liquefaction. This is considered to be a significant impact. <br />Impact GEO-3A: The Project could result in a significant impact related to development on unstable <br />geologic units and soils or result in lateral spreading, subsidence, liquefaction, or collapse. <br />Mitigation Measure GEO-3A: Project -specific geotechnical reports shall be prepared in accordance <br />with the City's grading permit regulations. The recommendations for both special foundations anc <br />4.5-12 DECEMBER 2014 <br />