Rising tides and earthquake risk spur bond proposal to fix San Francisco's 'invisible' wall
Just beyond San Francisco’s picturesque waterfront lies a 20-foot-deep seawall, unseen by visitors, that for a century has protected the city from floods.
With sea levels rising due to climate change and a recent report finding increased earthquake risk to the structure, city officials say it’s in need of repair. They’re hoping voters will support a $500 million plan to strengthen and repair the wall that traverses three miles from Fisherman’s Wharf to Mission Creek near the San Francisco Giants' bayfront stadium, AT&T Park.
The seawall protects $102.1 billion in property value in an area that represents $24.6 billion in economic activity, according to a city report.
The proposed project was spurred by a 2016 analysis of the seawall’s seismic and flood risk that found that the wall was standing on weak soil and could face significant damage in the event of an earthquake.
According to the report, the fill used for the wall – built before modern seismic standards were instituted – is susceptible to liquefaction, in which the soil acts like quicksand during an earthquake. In a major quake, it could slide up to five feet into the bay and cause immediate damage to the Embarcadero Promenade and roadway, the report found.
The 2016 survey also assessed the increased flood risk due to rising sea levels from climate change. If the wall were breached by rising tides, flooding could reach downtown San Francisco and the city’s Financial District.
Waters would pour into tunnels used by the Bay Area Rapid Transit District and Muni train lines – crippling the region’s transportation network and stranding hundreds of thousands of passengers, according to the report.
“If this critical piece of infrastructure were to fail, everyone in the Bay Area would be at risk,” the report warns.
The survey highlighted the urgency of the need to make improvements, said Elaine Forbes, director of the Port of San Francisco, which maintains the seawall and would oversee its modernization. Other than some minor improvements, the structure is essentially the same as it was built in the 1910s, she said.
The Embarcadero Seawall was built by the state government, transforming three miles of shallow tidelands into a deep water port, according to the report.
It was created by dredging a trench through the mud and filling it with rock and rubble capped with a timber pile and wharf.
The project ended up adding 500 acres of new land to the waterfront and creating a thriving tourist and business center that is an essential part of the city’s identity.
“The seawall has done a beautiful job of protecting the city over the last 100 years despite the soil conditions,” Forbes said.
But the analysis shows that the soils will not remain stable and storms in other parts of the country are indicative of the increased flood risks posed by climate change, she said.
The city’s Capital Planning Committee on April 16 endorsed a plan for a $425 million bond measure to shore up the structure. The San Francisco Board of Supervisors is scheduled to consider the proposal in May. If approved by the board, the bond would go before voters in November.
The bond measure would require a two-thirds supermajority to pass. A poll commissioned by the port in February found that 73% of city voters would support a measure to improve the seawall.
If the plan is approved by voters, port officials will commission a more detailed engineering report of the earthquake and flood risks. Based on those findings, the port could go forward with a series of fixes. They could include strengthening the ground below the seawall, replacing or retrofitting wharves, piers and bulkheads or even building a new seawall.
Under its schedule, construction could begin in 2026.
In addition to the $425 million of bond proceeds, the state is expected to contribute $55 million, the U.S. Army Corps of Engineers $10 million, the port $8 million and the city Planning and Municipal Transportation Agency $2 million.
The project would only be the first phase of anticipated improvements. Ultimately, the report estimates $5 billion in needs over 30 years to provide for greater long-term reliability. Port officials hope to leverage federal, state, local and private dollars for future projects.
Forbes said many residents may not know about the seawall but the concept is an easy one to grasp once they learn about it.
“It’s invisible infrastructure so we think most people are not aware of it,” Forbes said. “That’s a big part of our job to introduce the wall to residents and explain what it does for the city.”
The port has already begun giving tours of the waterfront and talking to community groups about the seawall, she said.
Jim Lazarus, senior vice president of public policy for the San Francisco Chamber of Commerce, said about two-thirds of the city’s major office buildings are in an area created by the construction of the seawall. He called it “vitally important” to the city and its economy.
While the general public may not know of the seawall, Lazarus said many property owners realize its importance. The chamber has not made a formal endorsement yet but Lazarus expects many in the business community will be helping the campaign to win passage of the bond measure.
“We need to fix this to preserve the Port’s property and the economic engine of San Francisco – from the ballpark in the south and Fisherman’s Wharf north and the downtown in between,” Lazarus said.
“The seawall is vital to our way of life in San Francisco—it protects our city from sea-level rise and is crucial to our seismic stability,” said Mayor Mark Farrell in a news release after the committee made its recommendation.
“With a strong seawall, we have a strong San Francisco. We need to do everything that we can to make sure it’s safe now and for future generations.”