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LSA ASSOCIATES, INC. CEQA INITIAL STUDY /MITIGATED NEGATIVE DECLARATION <br /> MARCH 7011 PREDA STREET PIPE BRIDGES UPGRADE <br /> SAN LEANDRO. CALIFORNIA <br /> longitudinal expansion/contraction of the pipeline during a seismic event (Creegan and <br /> D'Angelo Infrastructure Engineers 2009). Therefore, the risk of substantial adverse affects <br /> related to groundshaking would be reduced on the project site after project completion. <br /> iii) Ground Failure and Liquefaction. <br /> Less Than Significant Impact. Soil liquefaction results from loss of strength during cyclic <br /> loading, such as imposed by earthquakes. Soils most susceptible to liquefaction are loose to <br /> medium dense, saturated sands, silty sands, sandy silts, non - plastic silts and gravels with poor <br /> drainage, or those capped by or containing seams of impermeable sediment. The potential for <br /> liquefaction along the banks of San Leandro Creek is very high (ABAG 2009). However, the <br /> risk of substantial adverse affects to the proposed project related to liquefaction would be <br /> reduced after project implementation due to seismic retrofitting of the existing sewer pipes <br /> and pipe bridges (See response VI(a.ii)) above). Therefore, this impact is considered less than <br /> significant. <br /> iv) Landslides. <br /> Less Than Significant Impact. The project site is not in an identified landslide hazard area <br /> (ABAG 2009). Landside hazards in the City of San Leandro occur primarily in the East Bay <br /> hills, approximately 2.5 miles east of the project site (City of San Leandro 2002). Therefore, <br /> implementation of the proposed project would not adversely impact persons or structures due <br /> to landslides. <br /> b) Result in substantial soil erosion or the loss of topsoil? <br /> Less Than Significant with Mitigation Incorporated. Construction activities such as grading <br /> and vegetation removal have the potential to disrupt soil and cause erosion. However, all <br /> construction activities would be conducted when San Leandro Creek is dry between June 1 and <br /> October 15 (Mitigation Measure B1O -1). In addition, erosion and loss of topsoil would be <br /> avoided through the implementation of BMPs, including a wire- reinforced silt fence, installation <br /> of construction fencing, and suspending a drop cloth below the bridges to prevent debris from <br /> falling into the channel. Native trees removed during construction would be replaced after project <br /> completion (Mitigation Measure B10 -4). The implementation of BMPs and Mitigation Measures <br /> B10-I and B10 -4 would reduce construction period erosion impacts to a less than significant <br /> level. <br /> c) Be located on a geologic unit or soil that is unstable, or that would become unstable as a result of <br /> the project, and potentially result in on- or off -site landslide, lateral spreading, subsidence, <br /> liquefaction or collapse? <br /> Less Than Significant Impact. As described above, the potential for hazard from landslide is <br /> low and the potential for liquefaction is high. Therefore, the potential for liquefaction induced <br /> lateral spreading is also high. However, the purpose of the proposed project is to maintain flow <br /> capacity and improve pipe performance during future seismic and/or flood events. The proposed <br /> project would replace two existing sewer pipes and rehabilitate two existing pipe bridges. <br /> Therefore, the proposed project would not cause a geologic unit or soil to become unstable, but <br /> P. NEGI080I NCEQA\Predn__FINAL_IS•MND.doc (0328/I I) 29 <br />