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3. Environmental Checklist San Leandro Treatment Wetland IS/MND 3-32 February 2024 Fault Zone, it's important to note that fault rupture is not confined exclusively to these mapped zones. 25 The closest active faults to the Project site are the Hayward Fault, approximately 3.5 miles east, and the San Andreas Fault, around 15 miles southwest. Although fault rupture can occur beyond designated hazard zones, the risk is generally lower outside these mapped areas. Given the nature and design of the Proposed Project, which does not involve residential or human-occupied facilities, the risk of property damage or injury/loss of life due to fault rupture or strong seismic shaking is considered less than significant. The Project does not entail the construction of structures, and while liquefaction is possible at the site, the Project's purpose is to stabilize soils and sludge within the basin, thereby not enhancing liquefaction risk. Additionally, the construction and operation of the Project are not expected to exacerbate existing seismic or landslide hazards in the area, as there will be no alteration to groundwater levels or drainage patterns of groundwater and surface water. Moreover, there will be no excavation near landslide-prone areas or any activities that could increase the susceptibility of the site to liquefaction or ground shaking. Given these factors and the absence of residential or human-occupied facilities, the likelihood of the Project exacerbating risks of property damage or personal injury due to seismic events is minimal. Impact Designation: Less than Significant Impact b) Increase erosion: The construction of the Proposed Project, which entails ground-disturbing activities like grading and other earthworks, would temporarily increase the site's vulnerability to erosion. Despite these activities being planned for the dry season, the Project will develop and implement a construction-phase SWPPP, as detailed in the Hydrology and Water Quality section below. This SWPPP will incorporate specific BMPs such as silt fences, fiber rolls, and dust suppression techniques to effectively control or reduce erosion during construction. Moreover, as further described in Section 3.11, Hydrology and Water Quality, the Project is designed not to modify the current drainage patterns in a way that could lead to new erosion or sedimentation issues. Impact Designation: Less than Significant Impact c) Unstable geology or soils: The soil composition at the Proposed Project Site is characterized by artificial fill layered over Young Bay Mud, with older alluvial deposits beneath. The depth to bedrock is estimated to be around 1,000 feet deep, although not precisely determined. Subsurface investigations revealed that the dike surrounding the pond primarily consists of moderate- to high- plasticity clay fill with variable silt content.26 Organic materials from Young Bay Mud deposits were found in parts of the southern dike. The Proposed Project's objective is to establish a durable subgrade in the existing pond by improving soil conditions to support the placement of fill material for the planned treatment wetland. These 25 California Department of Conservation. California Earthquake Hazards Zone Application. Updated September 32, 2021. Accessed on December 11, 2023. Available at https://www.conservation.ca.gov/cgs/geohazards/eq-zapp 26 Fugro Consultants, Inc. 2014. Geotechnical Feasibility Study: WPCP Former Polishing Ponds Equipment Pad Project, San Leandro, California. Prepared on behalf of the San Leandro Water Pollution Control Plant.