Volunteers were out bright and early Wednesday morning along the Harbor Marsh coastline in the Palo Alto Baylands, joining an effort to build a nature-based buffer designed to absorb storm surges and curb flooding amid climate change and sea-level rise that threaten shoreline communities.
They were helping build what project developers described as the Bay Area’s first horizontal “living levee” directly connected to the Bay and irrigated with treated wastewater. About 35 people joined the initial planting of native species such as black elderberry, ninebark and marsh baccharis. Another volunteer day was scheduled for Saturday morning.
Save the Bay’s Jessie Olsen, whose organization helped lead the planting, said this is the first phase of work, with the plants expected to reach full maturity by the end of 2026.
“We often find that these in-person shoreline experiences that our programs can offer are a good way to introduce concepts like nature-based solutions, such as the horizontal levee,” Olsen told reporters during a recent media tour of the site.
Officials describe the project as a pioneering initiative to combine wastewater reuse with habitat restoration.
“This project is unique on the San Francisco Bay shoreline,” said Karin North, Palo Alto’s assistant director of Public Works, which owns and operates the Regional Water Quality Control Plant. “It uses treated wastewater from the plant to irrigate native plants and restore a transition zone between freshwater and salt marshes.”
Last year, the Palo Alto treatment facility began at least $369 million in upgrades to remove enough nitrogen from its treated water to safely release it into the Bay and help prevent algal blooms that could be harmful to marine life. The facility, which treats 20 million gallons of wastewater each day for more than 230,000 residents and businesses, is also critical infrastructure that the levee is designed to protect.
Unlike traditional concrete levees, a “living levee” uses native plants and vegetation to provide natural protection, absorbing the impact of storm surges and waves while reducing local flood risks.
The almost $7 million project — $2 million for design and $4.8 million for construction — started last September and was developed in partnership with the city of Palo Alto, consulting firm Environmental Science Associates, the San Francisco Estuary Partnership, Save the Bay, and researchers from the U.S. Geological Survey, California State University Channel Islands and UC Davis.
Samantha Engelage, a senior engineer with the city, said the levee provides benefits beyond flood protection.
“The other is to provide habitat for species and to accumulate sediment out here so that we can build up the marsh over time and adapt to sea-level rise,” she said during the tour.
Wildlife in the Palo Alto Baylands includes birds such as clapper rails and black rails, the western pygmy blue butterfly, mud crabs and various fish, among others.
The city’s climate adaptation assessment warns that sea levels could rise 3 feet to 10 feet by 2100, “impacting not only the shoreline but also areas with shallow groundwater.” Several parts of Palo Alto and nearby East Palo Alto frequently grapple with flooding during atmospheric rivers and other storms.
“In Palo Alto, many city services and infrastructure that are essential to public health, safety and the economy are located within areas predicted to be inundated by Bay water if adaptation measures are not implemented,” the assessment states.
Engelage hopes the project can serve as a model as the city and other Bay Area communities plan larger shoreline protection efforts.
“There are levees throughout the Palo Alto Baylands, but they’re relatively low and not FEMA-accredited,” Engelage said. “We know a larger project will be needed to address all the levees in this area. The city is working with other agencies to plan that, but it’s likely 10 to 20 years away. In the meantime, we hope to learn from this project and use it as a model for the larger design.”
Similar projects are underway or planned elsewhere in the Bay Area.
Oro Loma’s horizontal levee in Hayward also irrigates vegetation with treated wastewater, but it is not connected to the Bay. South of Palo Alto in Mountain View, a $20-million marsh restoration project is ongoing and will eventually connect to the Bay, but does not use treated wastewater. Another living levee is planned for North Richmond.
Heidi Nutters of the San Francisco Estuary Partnership said the group hopes the project will also encourage cities to find new uses for wastewater.
“Thinking about a horizontal levee is thinking about this wastewater, which we often see as something to dispose of, instead of thinking about it as a resource,” Nutters said. “When our natural systems are designed in ways that can support resilience for communities, they provide multiple benefits.”