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City of Pleasanton—Hidden Canyon Residences and Preserve Draft EIR Geology, Soils, and Seismicity FirstCarbon Solutions 3.6-23 https://adecinnovations.sharepoint.com/sites/PublicationsSite/Shared Documents/Publications/Client (PN-JN)/2148/21480016/EIR/3 - Draft EIR/21480016 Sec03-06 Geology.docx 3.6.4 - Methodology Impacts related to geology and soils were determined by reviewing a variety of databases, web maps, the Updated Geotechnical and Geologic Report by Cornerstone Earth Group and Update Geotechnical Review provided by Ninyo and Moore which is provided in Appendix E. Information on existing soils on the project site was provided by the Updated Geotechnical and Geologic Report, the Update Geotechnical Review, and the Web Soil Survey from the United States Department of Agriculture (USDA) Natural Resource Conservation Service (NRCS). Information on subsurface conditions including groundwater, subsidence, expansive, and collapsible soil were obtained by the Updated Geotechnical and Geologic Report and other supplemental resources from the California Department of Water Resources (CDWR), USGS, and the California Department of Transportation (Caltrans). Information on seismic-related hazards was provided by the Updated Geotechnical and Geologic Report and Geotechnical Review. Further analysis was performed by evaluating web maps from the California Department of Conservation and CGS-provided web maps to determine whether the project site was delineated within a Special Study Zone under the Alquist-Priolo Fault Zoning Act, or other zones of required investigation for liquefaction or landslides. Details on the major fault lines in the region were evaluated through reviewing reports on fault segments from the Quaternary Fault and Fold Database of the United States. The Assessment of the Paleontological Potential of Rock Units within the SVP Standard Guidelines was compared to the rock units underlaying the project site to determine the potential for uncovering significant paleontological resources during the construction phase of the proposed project. The UCMP Locality Search was utilized to identify vertebrate, invertebrate, plant, and microfossil localities uncovered in Alameda County that either were discovered in the same rock units situated on the project site or that were designated a locality name that matches the geography of the project area. In addition, a records search request was submitted to the UCMP on March 6, 2025, and completed on March 25, 2025, to obtain complete information on vertebrate and invertebrate localities uncovered in the Miocene-age rock units in the project region. The objective of the UCMP Locality Search and records search requests was to determine the potential of ground-disturbing activities during construction of the proposed project to uncover any significant paleontological resources. 3.6.5 - Thresholds of Significance The lead agency utilizes the criteria in the California Environmental Quality Act (CEQA) Guidelines Appendix G Environmental Checklist to establish thresholds of significance to determine whether impacts to geology, soils, seismicity and paleontological resources are significant environmental effects. As such, the City has determined that the proposed project would have a potential impact if it would: a) Directly or indirectly cause potential substantial adverse effects, including the risk of loss, injury or death involving: i. Rupture of a known earthquake fault, as delineated on the most recent Alquist-Priolo Earthquake Fault Zoning Map issued by the State Geologist for the area or based on