Environmental Declaration WPCP 20240409

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3. Environmental Checklist Site -specific evaluations, detailed in Appendix G, found chemical concentrations in stockpiled soil and sludge found within the existing retention basin at levels above applicable screening levels, which warranted further review. Evaluations included identifying chemicals of concern and evaluating exposure pathways to people and wildlife through groundwater and soil, as described below. During the construction phase, workers could be exposed to chemicals of concern during construction. Potential routes of exposure include incidental ingestion and dermal contact or inhalation of volatiles and airborne particulates. Appendix G shows that conservatively estimated cumulative cancer risk and noncancer hazards indicate construction worker exposure to chemicals of potential concern during the construction of the proposed treatment wetland does not pose an unacceptable risk to human health, based on criteria established by the CalEPA Department of Toxic Substances Control and the U.S. Environmental Protection Agency. All construction workers must be HAZWOPER trained and certified to mitigate residual risk to workers and reduce the potential for impacts associated with the accidental release of hazardous materials that are routinely used during construction activities. During the operations phase, people and wildlife will have no exposure to chemicals of concern in the soil due to the combined consequences of cement stabilization, covering this stabilized soil with about one foot of clean fill and covering the entire basin with a thick impermeable liner. Leaching tests were performed on the stockpile -soil and recently collected sludge samples to inform the risk to ecological receptors from metals leaching to groundwater. These tests showed that the leachability of metals in stockpiled soil and sludge is extremely low, with extracted concentrations below or slightly above applicable screening levels for fresh -water and salt -water habitats. The leachability of chemicals of concern is determined to be highly unlikely, given the test results combined with the Project components listed above. Consistent with regulatory guidance and consultation with the RWQCB, based upon reasonably anticipated future use of the Project site, there will be no complete human or ecological exposure pathways to chemicals of concern following the Proposed Project's construction. Fuel Pipeline Presence Three pipelines owned by Shell and Kinder Morgan run parallel below the service road atop the perimeter dike to the south of the existing retention basin. One line is Shell's inactive 8-inch fuel pipeline, while Kinder Morgan owns a 10-inch pipeline used for multi -product fuel and a 12-inch pipeline supplying jet fuel. These pipelines extend beyond the Proposed Project's eastern limit and run below the service road before turning southward into San Francisco Bay. As part of the design process, these pipelines were precisely mapped in coordination with the pipeline owners and will be depicted in all design drawings for the Proposed Project. Trenching for the pipeline connecting the nitrification units will occur within the existing service road, approximately 10 feet from the pipelines. This activity carries the risk of inadvertent damage to the pipelines. The City has already engaged with Kinder Morgan to identify appropriate measures to relocate the locations of all pipelines and establish notification procedures and actions in the event of pipeline damage. Mitigation Measure HZ-1 will be implemented to address potential hazards during construction, necessitating pipeline location determination, avoidance, and shutdown protocols in case of potential ruptures. By implementing this mitigation measure, the Project aims to minimize the risk associated with operating near active pipelines and ensure the initiation of appropriate emergency actions if pipeline damage occurs. San Leandro Treatment Wetland IS/MND February 2024