2014-069 - Final Environmental Impact Report No. 2014-01

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HARBOR BLVD. MIXED USE TRANSIT CORRIDOR PLAN FINAL FIR CITY OF SANTA ANA 5. Environmental Analysis GEOLOGY AND SOILS Harbor Boulevard Mixed Use Transit Corridor Plan could subject people and structures to hazards from subsidence. Collapsible soils are unlikely on developed land where soils were previously engineered and compacted to support development. Collapsible soils would be more likely on vacant land. The project area is highly urbanized, and the majority of the area is developed. Only a few sparsely scattered vacant lots exist, mostly north of 1st Street. Fine - grained soils, such as silts and clays, may contain variable amounts of expansive clay minerals that can undergo significant volume changes with changes in moisture content. The upward pressures induced by the swelling of expansive soils can have significant harmful effects on structures and other surface improvements. Expansive soils could be present within the project area. However, individual projects developed pursuant to the Harbor Boulevard Mixed Use Transit Corridor Plan would be required to meet the most current requirements of the CBC. For example, Chapter 18 of the CBC has requirements for excavation, grading, and fill; load bearing values of soils; and foundations, footings, and piles. Compliance with these requirements would ensure that there would not be substantial impacts related to ground subsidence, collapsible soils, or expansive soils. Additionally, as standard procedure by the City of Santa Ana, grading and soil compaction requires the preparation of site specific grading plans, soils and geotechnical reports (which must address ground subsidence, collapsible soils, expansive soils, and other potential soil stability hazards), and hydrology studies, which must be submitted to and reviewed and approved by the City before any grading activities. Each geotechnical investigation report would have recommendations for site grading and engineering of fill soils to minimize hazards from ground subsidence, collapsible soils, expansive soils, and other geologic hazards identified in that investigation. Submittal of these technical plans and studies would ensure that hazards arising from these potential geologic hazards would not occur, because they would be prepared in accordance with grading and engineering standards outlined in the most current CBC. Therefore, impacts would be less than significant. 5.4.4 Cumulative Impacts Impacts relating to soils and geologic influences are site specific and generally cannot be considered in cumulative terms. Mitigation of geologic, seismic, and soil impacts of other cumulative development projects in accordance with the City's General Plan (see Section 4.4, Assump ions Begar&ng Cumulatim Imps ir) would also be specific to each site and based on geotechnical studies. Additionally, as with the proposed project, other development projects in the City would be subject to compliance with modern building standards, such as the CBC, that reduce geologic and seismic related risks. Furthermore, as standard procedure by the City of Santa Ana, grading and soil compaction requires the preparation of site - specific grading plans, soils and geotechnical reports (which must address ground subsidence, collapsible soils, expansive soils, and other potential soil stability hazards), and hydrology studies, which must be submitted to and reviewed and approved by the City before any grading activities. Therefore, no adverse cumulative impacts related to soils and geology are anticipated. In consideration of the preceding factors, the project's contribution to Page 5.4 -12 PlaceWorkr