2019-040 - Mainplace Mall Transformation

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City of Santa Ana Addendum to the MainPlace Mall Transformation Proiect Fashion Square Commercial Center Final EIR 5.2 SOILS AND GEOLOGY Summary of Impacts Identified in the 1983 EIR The 1983 EIR described that onsite soils consist of artificial fill that overlies alluvial deposits that consist of compact to dense, fine to course sands and gravels. The 1983 EIR determined that no soils or geologic constraints were anticipated and that proper engineering techniques through the City's standard permitting process would reduce any potential impacts to a less than significant level. The 1983 EIR did not include any mitigation related to soils and geology and determined that no cumulative effects related to soils and geology would occur. Summary of Impacts Identified in the 1996 Addendum The 1996 Addendum determined that no soils or geologic constraints have been identified and that the development of new structures on the Project site would not result in any adverse soils or geologic impacts. No mitigation was required. Impacts Associated with the Proposed a Project No New Impact: A geotechnical exploration and seismic hazards review study was completed for the proposed Project, as prepared by Leighton and Associates in 2019 (Geo 2019) and included as Appendix B. Fault Rupture and Seismic Shaking The seismic hazards review study states that there are no known active faults within or adjacent to the Project site and that the site is not mapped within an Alquist-Priolo Earthquake Fault Zone (Geo 2019). The closest active fault to the site is the San Joaquin Hills blind thrust fault, which is 5.8 miles away. Thus, fault rupture would not occur on the Project site. However, the site could experience moderate to strong ground shaking from earthquakes along the major active and potentially active faults in the region. As a result, new structures in the City are required to be built in compliance with the California Building Code (CBC [California Code of Regulations, Title 24, Part 2]), as included in the City's Municipal Code as Chapter 8, Article 2, Division 1, which regulates all building and construction projects within the City and implements a minimum standard for building design and construction. The CBC includes specific requirements for seismic safety, excavation, foundations, retaining walls and site demolition. The Main Place Project's seismic hazards review study (Geo 2019) provides CBC seismic structural design criteria that are specific to the onsite soils and potential for seismic ground shaking and that apply specifically to excavation, recompaction, and foundation systems to occur on or be built on the Project site. Because the proposed Project would be required to be constructed in compliance with the CBC and the City's Municipal Code, verified through the City's plan check and permitting process, the proposed 53