Reso PC15-01 PC Reso (3051 ) to Adopt Initial Study-Mitigated Negative Declaration - La Palma

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3.0 Environmental Impact Checklist b) Result in substantial soil erosion or the loss of topsoil? Less-than-Significant Impact. Project construction would involve ground disturbing activities that would expose soils and increase the potential for soils erosion from wind or stormwater runoff.The project applicant would prepare a Stormwater Pollution Prevention Plan(SWPPP) as required by the State Water Resources Control Board's (SWRCB) Construction General Permit to prevent erosion and control sedimentation during project construction. Refer to Section 3.9, Hydrology and Water Quality, for a discussion regarding compliance with the SWRCB Construction General Permit. Once constructed,structures and associated landscaping would be installed on-site and the project would not include areas of exposed topsoil.As the project would comply with a SWPPP and would restore all disturbed area so that no topsoil is exposed,impacts related to soil erosion or the loss of topsoil are less than significant. No mitigation is required. c) Be located on a geologic unit or soil that is unstable, or that would become unstable as a result of the project,and potentially result in on-or off-site landslide,lateral spreading, subsidence,liquefaction, or collapse? Less-than-Significant Impact.As discussed under section a),implementation of the project would not pose potential risks from seismically-induced liquefaction and would not pose potential risks from landslides on-or off-site. As discussed below in section d), impacts from the near surface expansive soils underlying the project site would be reduced to a Iess-than- significant level with implementation of mitigation to reinforce structure foundations.Thus, impacts related to geological and soil stability as a result of the project would be less than significant. d) Be located on expansive soil,or collapsible soil,creating substantial risks to life or property? Less-than-Significant Impact with Mitigation Incorporated. The Geotechnical Investigation and Pavement Design Report(Appendix C) prepared for the project identified that that native surface soils at the project site have a high expansion potential when subjected to fluctuations in moisture.Expansive (shrink-swell) soils generally consist of clay materials that are capable of absorbing water. A change in the moisture content of an expansive soil can cause clay minerals to swell like a sponge or lose cohesion and collapse.The associated change in soil volume(expansion)has the potential to result in structural damage to buildings or other structures,including cracks in building foundations. Given the soils at the surface of the project site possess the properties of expansive soil, Mitigation Measure GEO-1 requires adherence to the recommendations for building foundations identified in the Geotechnical Investigation and Pavement Design Report to reduce potential risks to structures from being located on expansive soil. Implementation of Mitigation Measure GEO-1 would reduce potential project impacts from expansive soils on project structures to a less-than-significant level. Mitigation Measure GEO-1:Prior to the issuance of project Building Permits,the applicant shall submit plans and specifications complying with all of the La Palma Subdivision Project Final Initial Study/Mitigated Negative Declaration 34