Oro Loma Horizontal Levee

This horizontal levee project features a multi-benefit design that protects critical infrastructure against rising sea levels, provides wildlife habitat, and filters wastewater discharged from the district’s wastewater treatment facility plant. This experimental project helped researchers understand the functionality and performance of the horizontal levee design.

In collaboration with Peter Baye and researchers from UC Berkeley, ESA led the design and implementation of the first horizontal levee project on the West Coast. The project evolved from an ESA-led Hayward Shoreline Sea Level Rise Study, through a partnership with the Oro Loma Sanitation District and the San Francisco Estuary Partnership.

A horizontal levee is composed of a broad, flat vegetated transitional slope placed between tidal marshes and coastal levees, similar to where hillslopes meet the historic marsh edge. Treated wastewater passes through the levee through a sub-surface filtration and refining process to reduce nutrient loads. The Oro Loma design also includes a more conventional freshwater treatment wetland which contributes to nutrient removal before effluent is discharged to the horizontal levee.

Construction was completed in 2017 with help from Save the Bay and ongoing monitoring studies have shown successful results. The horizontal levee design has sparked several iterations along the San Francisco Bay shoreline including the First Mile Horizontal Levee, North Richmond Horizontal Levee, and the Palo Alto Horizontal Levee.