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4 Environmental Analysis <br /> 4.7 Geology, Soils, and Paleontological Resources <br /> Although regional subsidence has been noted in California due to the withdrawal of groundwater <br /> and hydrocarbons from the subsurface, the Project site is not in an area of subsidence that has <br /> been noted as "historical and current" (USGS 2022). Therefore, potential impacts related to <br /> regional subsidence would be a less than significant hazard to the Project during operation and <br /> mitigation measures would not be required. <br /> Mitigation: None required. <br /> IMPACT 4.7-4: Would the project be located on expansive soil, as defined in Table 18-1-B of the <br /> Uniform Building Code (1994), creating substantial direct or indirect risks to life or property?(Less <br /> than Significant Impact) <br /> Construction and Operations <br /> Expansive soils are clay rich soils that swell and shrink with wetting and drying. The shrink-swell <br /> capacity of expansive soils can result in differential movement below or adjacent to a structure, <br /> resulting in distress. As noted earlier, clay rich soils are present in the Project area (primarily the <br /> Carbona soils). In addition, bedrock units also can exhibit expansive properties due to their clay <br /> content; this includes the Neroly Formation claystone beds present at the site. Therefore, <br /> operation of the Project could potentially subject people and structures to the effects of expansive <br /> soils, which could result in damage to structures. <br /> However, all structures and facilities erected as part of the Project must be designed and <br /> constructed in accordance with either the San Joaquin County Building Code or the Alameda <br /> County Building Code, which are based on CBC standards (the Uniform Building Code is no <br /> longer applicable) specific to expansive soils. Following these design standards would yield <br /> structures that could tolerate the effects of expansive soil or, if necessary, the expansive soils <br /> would be remediated. Expansive soil remediation could include soil removal and replacement, <br /> chemical treatment, or structural enhancements. Therefore, operational impacts related to <br /> expansive soils would be less than significant and mitigation measures would not be required. <br /> Mitigation: None required. <br /> IMPACT 4.7-5: Would the project have soils incapable of adequately supporting the use of septic <br /> tanks or alternative wastewater disposal systems where sewers are not available for the disposal <br /> of wastewater? (Less than Significant Impact) <br /> Construction <br /> The Project would use portable toilets on-site during construction, as well as during the operations <br /> period. Sanitary waste is expected to average up to 30 gallons per day. Waste disposal would <br /> occur at a permitted off-site facility equipped to handle sanitary waste. Thus, a septic tank system <br /> would not be required on the Project site. <br /> Operations <br /> The Project will be unmanned and will not include domestic sanitation facilities; thus, no <br /> wastewater will be produced or discharged. Therefore, the use of septic tanks or alternative <br /> wastewater systems is not anticipated for the Project.As a result,there are no operational impacts <br /> involving the adequacy of soils to support septic tanks or alternative waste disposal systems. <br /> Mitigation: None required. <br /> Griffith Energy Storage Project 4.7-20 Tetra Tech/SCH 2022120675 <br /> Draft Environmental Impact Report August 2023 <br />