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4 Environmental Analysis 4.7 Geology, Soils, and Paleontological Resources the Alameda County and San Joaquin County Building Codes and following the recommendations from the site-specific geotechnical report, will be incorporated into the Project design plans. Having site-specific geotechnical information on the Project site and using normal and common construction techniques would minimize potential impacts from landslides on-site or to adjacent properties. As such, impacts associated with on- or off-site ground failure during construction would be less than significant and mitigation would not be required. Operations Expansive soils are clay rich soils that swell and shrink with wetting and drying. The shrink-swell capacity of expansive soils can result in differential movement below or adjacent to a structure, causing distress to the structure. The clay rich Carbona soils present in the Project area, which account for about two-thirds of the Project site, and the Clear Lake clay and Rincon clay loam found in the gen-tie corridor, have been characterized with high shrink-swell potential. The Calla soil of the Calla-Carbona Complex and the Linne clay loam are considered to have only moderate shrink-swell potential. Bedrock units also can exhibit expansive properties due to their clay content; this includes the Neroly Formation claystone beds present at the site. Therefore, operation of the Project would potentially subject people and structures to the effects of expansive soils, which could result in damage to structures. However, structures to be installed as part of the Project should be designed and constructed in accordance with the County Building Codes, which are based on CBC standards (the Uniform Building Code is no longer applicable) specific to expansive soils. These required design standards would provide site preparation techniques to remediate expansive soil and require structures that could tolerate the effects of expansive soil. Addressing expansive soil conditions could include soil removal and replacement, chemical treatment, or structural enhancements. Therefore, operational impacts related to expansive soils are expected to be less than significant and additional mitigation measures would not be required. The soils in the Project area may be prone to collapse or settlement, which can result in differential movement beneath foundations, potentially causing distress to above-grade and at-grade structures. As such, operation of the above- and at-grade structures associated with the Project would potentially subject people and structures to the effects of ground settlement, which could result in damage to structures. Detrimental ground settlement from new structures or earth loads is typically alleviated by removal and replacement of the settlement/collapse-prone soils. Also, implementation of ground improvement methods and structural support systems would minimize the potential for impacts related to collapse or settlement. The Project would be designed in accordance with the Alameda County and San Joaquin County Building Codes, which mandate that design reports be developed based on site-specific geotechnical investigation. The recommendations provided with such an investigation will be addressed during the design stage of the Project. The final design will specifically address any detrimental ground conditions that could be impacted by the new structures and loads. Therefore, impacts related to settlement or collapsible soil would be less than significant and mitigation measures would not be required. Griffith Energy Storage Project 4.7-19 Tetra Tech/SCH 2022120675 Draft Environmental Impact Report August 2023