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2 Environment 7.B. - Page 71 <br /> during the CE&G subsurface exploration program consists of interbedded layers of loose poorly <br /> graded sand with silt and silty sand. The report includes measures to prevent settlement of the <br /> path including over-excavation, a woven geotextile mat, 12 inches of crushed rock,and <br /> micropiles extending 10 feet into the Old Bay Mud (CE&G, 2013). CE&G identified the <br /> potential for liquefaction-induced distress including lateral spreading, subsidence, and ground <br /> lurching at the site as moderate,but did not recommend specific measures for liquefaction along <br /> the trail,which it does not consider a lifeline facility. In the event of significant ground shaking, <br /> the City would automatically close the access gates to the joint-use path, so that the risk to the <br /> public would be less than significant. (Less than Significant Impact) <br /> iv)Landslides? <br /> The project area is relatively flat with elevations ranging from 5-15 feet above sea level. The <br /> proposed retaining wall would be constructed on a slanted surface under the US 101. The City <br /> would implement the design-level recommendations contained in the geotechnical report by <br /> constructing the tieback retaining walls with the appropriate tieback design and lengths, using <br /> corrosive protection for the anchors, adding grouting of the tieback anchors for additional <br /> support, and testing the maximum load of the anchors for the tieback retaining walls (CE&G, <br /> 2013). The implementation of these design measures would reduce the potential impacts <br /> associated slope-related issues, such as landslides, to a less than significant level. (Less than <br /> Significant Impact) <br /> b)Result in substantial soil erosion or the loss of topsoil? <br /> The composition of the one soil type within the project area (Urban-land Orthents,reclaimed <br /> complex, 0-2 percent slopes) consists of bay mud,gravel,broken cement and asphalt,and solid waste <br /> materials. Based on the soil structure and hydraulic conductivity, the Urban-land Orthents,reclaimed <br /> complex soil type is considered to have a moderate erosion potential (0.20) (WRECO,2013). The <br /> proposed project includes BMPs for erosion control,including the biodegradable coir rolls, straw <br /> wattles, or silt fences installed along the base of slopes during construction, to capture sediment and <br /> revegetation. See mitigation measures BIO 7, Site Construction Management Practices;BIO 8, <br /> Revegetate Disturbed Areas; and HYD 1, Implement Best Management Practices (BMPs). (Less <br /> than Significant Impact with Mitigation Incorporation) <br /> c)Be located on a geologic unit or soil that is unstable, or that would become unstable as a <br /> result of the project, and potentially result in on- or off-site landslide,lateral spreading, <br /> subsidence,liquefaction or collapse? <br /> The proposed project includes expansive soils and would be subject to uplifting. The CE&G <br /> geotechnical report recommends design criteria for adequate stabilization of the foundation for the <br /> joint-use path for both conditions. Due to the highly expansive and saturated nature of the soils in <br /> the project area (Young Bay Mud), the subgrade soils that would underlay the pavement of the joint- <br /> use path would need to be stabilized prior to the construction of the joint-use path. The City would <br /> 2-31 US 101 Pedestrian Undercrossing and Bair <br /> Island Road Storm Drain Pump Station Project <br />