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4 Environmental Analysis <br /> 4.7 Geology, Soils, and Paleontological Resources <br /> IMPACT 4.7-6: Would the project directly or indirectly destroy a unique paleontological resource <br /> orsite orunique geologic feature?(Less than Significant Impact with Mitigation Incorporated) <br /> Operations and Decommissioning <br /> The Project area is on the Central Valley geomorphic province border, characterized by young, <br /> unconsolidated sediments with low potential for containing fossils. Nevertheless, a total of 16 sites <br /> where fossils have been found previously were identified in the UCMP database at locations <br /> between 1 and 3 miles from the site. <br /> The bedrock geologic units mapped within the Project site include the Miocene age Neroly <br /> Formation (Tn) and Pliocene age nonmarine sedimentary rocks (Tps), along with Holocene age <br /> unconsolidated alluvium. Both older units have potential for containing fossils, as demonstrated <br /> by the discoveries identified in the UCMP database search. In addition, the significant depths of <br /> excavation (in places over 70 feet) needed to achieve the final grade will increase the opportunity <br /> of encountering the older rock units lying under the younger sediments. Other excavations to <br /> install foundations or underground cables may reach depths of up to 10 feet below the ground <br /> surface after final grade is achieved. However, since both the older geologic units (Tn and Tps) <br /> have similar likelihood of encountering fossils with ground-disturbing activities, a potentially <br /> significant impact could result if paleontological resources are encountered and inadvertently <br /> destroyed during ground-disturbing activities. By implementing Mitigation Measures GEO-2 <br /> (Worker Education) and GEO-3 (Contingency Plan for Unanticipated Finds), such potential <br /> impacts would be reduced to less than significant. <br /> Mitigation: GEO-2 and GEO-3. <br /> 4.7.5 Mitigation Measures <br /> The following mitigation measures are recommended as a precaution to reduce significant <br /> impacts to geological and paleontological resources. <br /> GEO-1: Stormwater Pollution Prevention Plan: The construction contractor shall incorporate <br /> best management practices (BMP) consistent with the NPDES General Construction Permit <br /> Program and shall prepare a Stormwater Pollution Prevention Plan (SWPPP) prior to construction <br /> and decommissioning. The plan shall be prepared by a Qualified SWPPP Developer (QSD) and <br /> submitted for review and approval by San Joaquin County, as the lead agency. The SWPPP <br /> would apply to the entire Project, including portions in Alameda County and San Joaquin County. <br /> The SWPPP BMPs shall include, but not be limited to, the following: <br /> 0o Scheduling to avoid construction during rain events to the maximum extent possible; <br /> 0o Preservation of existing vegetation and topography to the maximum extent practicable; <br /> 0o Stabilized construction entrances and exits; <br /> 0o Erosion control, such as mulching, temporary drains and cullies, sandbag barrier, <br /> geotextiles and mats, silt fences, brush or rock filters, earth dikes, straw bale barriers, <br /> and sediment traps; <br /> oo Sediment control; <br /> Griffith Energy Storage Project 4.7-21 Tetra Tech/SCH 2022120675 <br /> Draft Environmental Impact Report August 2023 <br />