San Leandro Treatment Wetland for Pollution Reduction, Habitat Enhancement and Shoreline Resiliency

2024 UPDATE: In June 2024, the Governing Board of the Restoration Authority authorized disbursement of up to $3,734,489 dollars to the City of San Leandro to convert a 6.9-acre wastewater storage basin adjacent to San Leandro’s Water Pollution Control Plant to a multi-benefit freshwater treatment wetland that will remove wastewaterborne nitrogen, phosphorus, and contaminants of emerging concern, including completing final permitting for the conversion and develop a shared vision for community-based shoreline resilience planning efforts and scope a Shoreline Master Plan for the shoreline of San Leandro, which is a disadvantaged area.  The first component of this project will convert a marginal storage pond to a treatment wetland, ensuring this pond serves not just a single-use flood storage function but meets multiple goals of water quality improvement, habitat enhancement, public access, and sea level rise adaptation. The second component of this project consists of coordinating with surrounding landowners to develop a shared vision for shoreline resiliency for sea level rise adaptation. This project component includes scoping a Shoreline Master Plan for the City of San Leandro to protect critical infrastructure and enhance ecological resources. 

This implementation project is based upon the work done under the 2018 Authority planning grant. Work under that grant involved holding two public workshops to prioritize community-based outcomes, solicit feedback on conceptual designs, and enhance general community engagement. Participants overwhelmingly supported the conversion of degraded Baylands to beneficial multi-benefit uses. They helped shape priorities of the project to strengthen ecosystem benefits and services over traditional wastewater plant operations or allow redevelopment of lands for economic benefits.

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2023 UPDATE: The project timeline has been amended to extend into January 2024. The City is in the final process of determining whether on-site soil can be utilized to fill the treatment wetland to a design elevation or if other alternatives must be pursued. The City initiated the Initial Study and Mitigated Negative Declaration for the Project, which is about 30% complete.

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The project will prepare detailed designs, permit applications, and environmental documentation for the restoration of a 4.3- acre wastewater storage basin to create a multi-benefit treatment wetland at the City of San Leandro’s Water Pollution Control Plant (WPCP), and develop a community-based shoreline resiliency and tidal marsh restoration vision for the surrounding area. It will advance the reduction of wastewater-borne contamination and eutrophication via development of new forms of green infrastructure.

For decades, San Francisco Bay has been recognized as a nutrient-enriched estuary, largely due to heavy inputs of nitrogen and phosphorus from 40+ wastewater treatment plants that discharge to its subembayments. Until recently, the Bay has resisted nutrient over-enrichment due to high turbidity, strong tidal mixing, and grazing by bivalves. However, ongoing observations by USGS and the San Francisco Estuary Institute (SFEI) suggest additional water quality limits and management actions are needed to protect SF Bay from the potential effects of nutrient over-enrichment, such as harmful algae blooms and low dissolved oxygen. Implementation of this project will significantly improve habitat conditions at a contaminated shoreline site and is anticipated to reduce nitrogen waste from San Leandro’s WPCP by at least 15-20%, equivalent to about 40,000 kg of nitrogen per year.

In addition to design of the treatment wetland, the project will include coordination with surrounding landowners to enhance shoreline resiliency for sea level rise (SLR) adaptation. San Leandro’s WPCP, built in 1939, is the oldest among those examined and 82% of the City’s wastewater infrastructure is exposed to potential flooding at just 16 inches of SLR. Phase 1 of this Project involves the conversion of a marginal storage pond to a treatment wetland, ensuring this pond serves not just a single-use flood storage function but meets multiple goals of water quality improvement, habitat enhancement, public access, and SLR adaptation.