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SAN LEANDRO SHORELINE DEVELOPMENT DRAFT EIR <br />CITY OF SAN LEANDRO <br />GEOLOGY, SOILS, AND SEISMICITY <br />Mitigation Measure GEO-3C: Settlement of the existing fill and Bay Mud could have adverse effects on <br />shallow foundations, underground utilities, pavements, and other improvements. Options to mitigate <br />these effects include use of shallow ridged foundations for smaller structures, supporting larger <br />structures with deep foundations such as driven piles, and installing flexible connections for utilities. <br />Pre -loading consolidation (surcharging) prior to construction of new improvements could also be <br />considered. The recommendations for both special foundations and other geotechnical engineering <br />measures specified in project specific geotechnical reports shall be implemented during design and <br />construction. <br />Significance After Mitigation: Less than significant. <br />GEO-4 The Project could create substantial risks to property as a result of its <br />location on expansive soil, as defined by Section 1803.5.3 of the <br />California Building Code. <br />Expansive Soils <br />The fill and native soils that cover the Project site east of the historic shoreline are moderately to highly <br />expansive. Expansive soils undergo a significant volume change as a result of wetting or drying. This <br />volume change could cause damage to improperly designed foundations and pavements. Where buildings <br />are constructed in areas containing expansive soils this impact can be effectively mitigated through use of <br />appropriate foundations, by capping expansive soils with a layer of non -expansive fill, or by lime <br />treatment. Typical mitigation measures for pavements include special pavement design, lime treatment of <br />subgrade soils and/or sub -excavation of expansive soils and replacement with non -expansive fill. This is <br />considered to be a significant impact. <br />Impact GEO-4: The Project could create substantial risks to property as a result of its location on <br />expansive soil, as defined by Section 1803.5.3 of the California Building Code. <br />Mitigation Measure GEO-4: The Project geotechnical engineer shall make specific recommendations <br />for mitigation of expansive soils under pavements and structures, including techniques such as <br />capping expansive soils with a layer of non -expansive fill, or by lime treatment. Typical mitigation <br />measures for pavements could include special pavement design, lime treatment of subgrade soils <br />and/or sub -excavation of expansive soils and replacement with non -expansive fill. These <br />recommendations shall be based on testing of the in -site fill materials. The recommendations shall be <br />submitted to the City as a part of building and/or paving plan submittal. <br />Significance After Mitigation: Less than significant. <br />GEO-5 <br />The Project would not have soils incapable of adequately supporting the <br />use of septic tanks or alternative wastewater disposal systems where <br />sewers are not available for the disposal of wastewater. <br />Development at the Project site would not require the use of septic tanks or alternative wastewater <br />disposal systems. Wastewater will be discharged into the existing public sanitary sewer system, which is <br />4.5-14 DECEMBER 2014 <br />