2024-053 - Final Supplemental for The Related Bristol Specific Plan Project

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MM GEC)-2 Implementation of Geotechnical Recommendations for Groundwater and Expansive Soils. Project plans, grading specifications, and construction permitting shall incorporate site specific earthwork and ground improvement requirements related to groundwater saturated soils and expansive soils consistent with the California Building Code and City of Santa Ana requirements applicable at the time of grading/construction as stated in a design level geotechnical report and approved by the City's Building and Safety Division. This shall include recommendations related to discovery of groundwater, wet soils, or unstable soils during grading, stabilization, dewatering, fill materials, and foundations. Impact Finding: The Project would be located on expansive soils, as defined in table 1 B-1 B of the Uniform Building Code (1994) but would not create substantial risks to life or property (Draft Supplemental EIR at p. 5-4-12). Changes or alterations have been required in, or incorporated into, the Project that avoid or substantially lessen the significant environmental effect identified in the Draft Supplemental EIR. Facts in Support of Findings: The Project site contains lean and fat clays, and silty sand and poorly - graded sands with interbeds of clays, which have been tested and determined to have a medium to high potential for expansion due to the clay content (included as Appendix G to the Draft Supplemental EIR). The clayey soils are present onsite from the ground surface to approximately 25 to 30 feet bgs. Prior to approval of construction, an engineering level design geotechnical report is required to be prepared and submitted to the City that details the project designs that have been included to address potential geotechnical and soil conditions pursuant to the CBC requirements that are included in the City's Municipal Code Chapter 8, Article 2, Division 1, and implemented by Mitigation Measures GEO-1 and GEO-2. Therefore, due to the need for mitigation to ensure implementation of existing CBC measures, impacts related to Project buildout of the site would be slightly greater than the impact conclusions set forth in the GPU FEIR, which determined that impacts related to expansive soil would be less than significant with implementation of existing regulations (Draft Supplemental EIR at p. 5-4-1 2). Mitigation Measures: MM GEC)-1 Incorporation of and Compliance with a Design Level Geotechnical Report. As listed previously. MM GEC?-2 Implementation of Geotechnical Recommendations for Groundwater and Expansive Soils. As listed previously. Impact Finding: The Project would not directly or indirectly destroy a unique paleontological resource or site or unique geologic feature (Draft Supplemental EIR at p. 5.4-1 3). Changes or alterations have been required in, or incorporated into, the Project that avoid or substantially lessen the significant environmental effect identified in the Draft Supplemental EIR. Facts in Support of Findings: As described in Appendix H to the Draft Supplemental EIR, the Project site is underlain by Holocene -aged axial channel deposits, and due to the young age of the onsite soils, it is unlikely that excavation at the surface would impact fossil resources. However, Pleistocene age alluvium may exist below the younger axial channel deposits which could yield fossils. Thus,