If You Build It, They Will Come!

On an overcast and unassuming Thursday morning in July, a small barge sailed into India Basin along San Francisco’s southeastern waterfront. Resting on the barge were 60 concrete structures called Oyster Reef Balls (ORBs) ready to be deployed into the shallow waters off of Heron’s Head Park. The ORBs resemble wiffle balls cut in half, although much larger, each weighing about 1,100 pounds and requiring a crane to lower them into their designated position about a hundred feet from the shore.

Unless you were to look right at the nadir of low tide, you would probably miss this new reef at Heron’s Head. Just like the native Olympia oyster once ubiquitous in the San Francisco Bay, it’s hard to spot. But our hope is that this structure will soon serve as a substrate for a living Olympia oyster reef — a reef that will filter the water, provide food and habitat for other species, and protect the shoreline.

The shoreline at Heron’s Head Park has been eroding over the past 20 years due to wind-waves, tidal flows, and a lack of sediment accumulation. Crucial tidal salt marsh is lost every year.

The effort to spawn an offshore reef is part of the Port of San Francisco Heron’s Head Park Shoreline Resilience Project aimed at curbing the erosion. Funded by the San Francisco Bay Restoration Authority, the Ocean Protection Council, the California Department of Fish & Wildlife, and the California State Coastal Conservancy, it involves constructing shoreline features, such as a coarse sediment beach, and installing rock groynes (solid structures that absorb wave energy) and subtidal oyster reef balls to dampen the erosive force of wind-driven waves and enable wetlands to migrate farther inland as sea levels rise.

Each ORB is made of ECOncrete, a special mix with a lower carbon footprint than traditional concrete whose rough surfaces allows marine life to latch on. Additionally, the ORBs contain, within their hollow domes, a precious cargo of bagged oyster shells. These shell bags and habitat blocks were assembled and installed over the course of two days this summer by the Wild Oyster Project and our volunteers.

Each oyster shell bag is special. The cured shells in each have been collected from local restaurants around the bay over many years by Wild Oyster Project volunteers. The bags are made of a biopolymer created from potato starch that should completely degrade in the next 10 years. Wild Oyster Project, which is striving to rewild the San Francisco Bay by increasing its biodiversity through the restoration of native oyster reefs, is unwavering in its commitment to not add plastic to the marine environment.

The San Francisco Bay is the largest estuary on the Pacific Coast of the US, encompassing approximately 160,000 hectares, and it is widely recognized as one of North America’s most ecologically important estuaries. By using oysters as a living shoreline element, a living, breathing ecosystem is created, rather than a static system like a sea wall or riprap.

Learn more about this Earth Island Project at wildoysters.org

“I can’t tell you how grateful I am for Wild Oysters’ contribution to this project – from donating the cured oyster shells, to the conception, planning, recruitment, execution, and photo documentation of a very fun and productive day,” said Carol Bach, Heron’s Head Resiliency Project lead for the Port of San Francisco. “There would not be oyster shell bag and fish hut enhancements to the oyster reef balls without the Wild Oyster Project.”

The Heron’s Head project, which is part of a regional plan to restore 100,000 acres of tidal wetlands, oyster reefs and other habitat around the bay, serves as an exemplary case study for how nature-based solutions can be designed and implemented and how such solutions can be a piece of a larger puzzle for building resilient and adaptive shorelines in California in the face of climate change and sea level rise.