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Finding: Less than significant impact. (DEIR, p. 2-6; Initial Study, pp. 30-31)
<br />Facts in Support of Finding: Soil liquefaction is a phenomenon in which saturated, cohesionless soil
<br />layers, located within approximately 50 feet of the ground surface, lose strength due to cyclic pore water
<br />pressure generation from seismic shaking or other large cyclic loading. During the loss of stress, the soil
<br />acquires "mobility" sufficient to permit both horizontal and vertical movements. Soil properties and soil
<br />conditions such as type, age, texture, color, and consistency, along with historical depths to ground water
<br />are used to identify, characterize, and correlate liquefaction susceptible soils. Soils that are most
<br />susceptible to liquefaction are clean, loose, saturated, and uniformly graded fine-grained sands that lie
<br />below the groundwater table within approximately 50 feet below ground surface. Lateral spreading is a
<br />form of seismic ground failure due to liquefaction in a subsurface layer. The California Geological Survey
<br />Seismic Hazard Zones Orange Quadrangle map shows the Project site is within a liquefaction zone.
<br />However, exploratory borings at the Project site identified groundwater at approximately 110 feet below
<br />the ground surface, and borings on the Project site did not encounter groundwater to the maximum depth
<br />of 85 feet that was explored. Likewise, the groundwater wells that are located near the Project site identify
<br />groundwater levels at 110 feet below the ground surface and 143 feet below the ground surface. In
<br />addition, borings on the Project site in 2017 identified that soils consist of silty fine to medium sands with
<br />local layers of fine to coarse sands with gravel size rock and some larger rock fragments, which are not
<br />the uniform fine-grained sand that typically liquefies. In addition, the Geotechnical Engineering
<br />Investigation (Geo 2017) prepared for the Project site conducted liquefaction analysis and determined that
<br />thin layers of onsite soils have the potential for liquefaction; however, these soils are confined by less
<br />permeable soils that would prevent the manifestation of liquefaction. Thus, because the groundwater level
<br />is far below 50 feet below the ground surface and soils are not uniformly graded fine-grained, the potential
<br />for liquefaction and related lateral spreading or ground failure to occur on the Project site is low. In
<br />addition, as described above, the proposed Project would be required to be constructed in compliance with
<br />the CBC and the City's Municipal Code, as detailed in the Geotechnical Engineering Investigation (Geo
<br />2017) prepared for the Project site, which would be verified through the City's permitting process. (Initial
<br />Study, pp. 30-31)
<br />For the aforementioned reasons, the Project would result in a less than significant impact related to
<br />liquefaction, lateral spreading, and ground failure. (Initial Study, pp. 30-31) This conclusion also applies,
<br />for the same reasons, to the Modified Project.
<br />9.6.1.4 Exposure to Potential Risk of Loss, Injury, or Death — Landslides
<br />Threshold: Would the Project expose people or structures to potential substantial adverse effects,
<br />including the risk of loss, injury or death involving landslides?
<br />Finding: No impact. (DEIR, p. 2-6; Initial Study, p. 31)
<br />Facts in Support of Finding: Landslides and other slope failures are secondary seismic effects that are
<br />common during or soon after earthquakes. Areas that are most susceptible to earthquake induced
<br />landslides are steep slopes underlain by loose, weak soils, and areas on or adjacent to existing landslide
<br />deposits. As described above, the Project site is located in a seismically active region subject to strong
<br />ground shaking. However, the Project site is not located within or adjacent to an earthquake -induced
<br />landslide area. (Initial Study, p. 31.) In addition, the Project site is located in a flat developed urban area
<br />Resolution No. Page 32 of 76
<br />Certification of the Magnolia at the Park EIR
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