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3. Environmental Checklist San Leandro Treatment Wetland IS/MND 3-39 February 2024 sensitive habitats, and limiting all fueling, maintenance, and emergency response activities to within paved portions of the WPCP. Further, the amount of hazardous chemicals present during construction would be limited to what is required to operate construction equipment. The potential for the release of hazardous materials during construction is low, and even if a release were to occur, it would not result in a significant hazard to the public, surrounding land uses, or the environment due to the small quantities of these materials associated with construction vehicles. Similarly, the operation and maintenance of the Proposed Project may involve handling small quantities of hazardous materials, such as lubricants, oils, and solvents, consistent with existing operations. Federal and state laws ensure worker safety by minimizing risks from physical and chemical hazards and mandating Hazardous Waste Operations and Emergency Response (HAZWOPER) training for relevant activities. Businesses using hazardous materials must submit Hazardous Materials Business Plans to local agencies for inspection, ensuring compliance with labeling, training, and storage regulations. Hazardous substances associated with the Proposed Project are typically limited in both amounts and use such that they can be contained without impacting the environment. In addition, compliance with safety regulations and industry standards, including the California fire code and local building codes, minimizes hazards to the public and the environment. As an existing facility, updates to the Hazardous Materials Business Plan would reflect any changes resulting from the Proposed Project. Adherence to existing laws and regulations governing hazardous materials management ensures that the Project's impact remains less than significant. Impact Designation: Less than Significant Impact b) Accidental Spills and Releases to the Environment: This subsection addresses accidental spills and hazardous material conditions with respect to evaluating the exposure of people or the environment to adverse hazardous materials. Due to the industrial nature of the site and the immediate surroundings, as well as the Proposed Project location, with respect to OAK airport, considerations include the presence of pipelines, legacy contamination, and the routine risk of spills during the construction and operational phase of the Proposed Project. Legacy Contamination and Reuse of Stockpiled Material This section addresses concerns regarding historical contamination at the Project site and references Appendix G, which details a risk assessment for reusing stockpiled material in the Proposed Project. The Proposed Project involves mixing stockpiled soil into the existing retention basin, which is known to contain sludge from historical operations at the WPCP. This mixture will be cement-stabilized to create a more stable working surface. Available Information on the subsurface soils reveals that the pond's dike was built predominantly from clay fill of moderate to high plasticity, interspersed with silt. Original construction documents from the 1970s advise covering any exposed sand at the dike's base with a layer of compacted clay one foot thick. These dike-fill materials, spanning 9 to 16 feet in thickness, rest on top of layers of alluvial deposits and dense bay mud. The combined soil and sludge will then be topped with around 11,000 cubic yards of uncontaminated fill to elevate the basin by an additional foot. An impermeable liner will be placed over this clean fill to form the base of the non- vegetated section of the treatment wetland. To ensure a solid foundation and further eliminate exposure pathways to people and the environment, the soil/sludge mix will be solidified with cement.