A ballot measure to bring cars back to JFK Drive in Golden Gate Park and the Great Highway along Ocean Beach has a hidden $80 million price tag, as a city report revealed recently. But the plan would also work against San Francisco’s goals of fighting climate change, not just encouraging car use but also intensifying erosion from higher seas already threatening one corner of the city.
With water on three sides, San Francisco is already seeing the effects of sea level rise. Twice a year, around the solstices, extra-high “king tides” flood the waterfront. Scientists say such flooding will become more common with sea level rise due to climate change, and the city knows it must spend billions of dollars to prepare.
A city proposal on the table would address one flashpoint: the eroding beach and bluffs on SF’s southwestern edge. The proposal, still under review, calls for permanent removal of the Great Highway extension south of Sloat Boulevard. This short stretch of road has already been reduced to two lanes by a series of El Niño storms more than a decade ago.
Construction is supposed to start in early 2024 to replace the deteriorating road with land, sand, vegetation, and a bike and pedestrian trail that can better protect the Oceanside wastewater plant and the San Francisco Zoo, both situated just on the other side of the road.
But “Access for All,” which will appear on the ballot as Prop I, would force the city to keep the Great Highway extension, as well as return cars to JFK Drive in Golden Gate Park and to the rest of the Great Highway, which is currently closed to cars on weekends.
In an August 18 report, City Controller Ben Rosenfield wrote that the cost to keep and bolster the extension would be approximately $80 million more than what’s currently planned because “more significant investments would likely be required in the future as erosion occurs.”
Seawalls ‘kill beaches’
What Prop I doesn’t spell out, but is almost certain to be necessary, is construction of a conventional seawall to protect both a refurbished Great Highway extension and the critical infrastructure of the Oceanside wastewater plant, which handles 20 percent of the city’s sewage. The cost would be tallied with more than dollars, according to a geologist who knows this stretch of coast intimately.
Conventional seawalls “kill beaches,” according to Patrick Barnard, a research geologist with the U.S. Geological Survey in Santa Cruz. Barnard was a technical consultant on the 2012 Ocean Beach Master Plan, a long-term strategy from multiple agencies to deal with coastal erosion.
“This will accelerate the erosion of the beach and reduce access,” says Barnard. In other words, keeping the road is shortsighted and flies in the face of the attempt to shore up this corner of the city against inevitable higher waters.
The Ocean Beach Master Plan has led to an environmental review, which spells out the preferred option — permanent removal of the road — and four others, one of which is to do nothing.
Prop I says nothing about how the city should keep the road open. When asked about the likely need for a conventional seawall, campaign spokesperson Joe Arellano says “the city has multiple viable options.”
“At the end of the day, residents shouldn’t have to continue dealing with gridlock awaiting a project that is years away and may never come to fruition,” Arellano says. Until recently, Prop I was entirely funded by people and entities associated with the de Young Museum, which has consistently fought the JFK Drive closure, calling it bad for business.
Closing the Great Highway extension would divert traffic to Sloat Boulevard and in particular the intersection with Skyline Boulevard, which SFMTA has already targeted for an upgrade.
Pushing boundaries
When San Francisco developed its western edge more than a century ago, it pushed the shoreline 200 feet seaward to add an extra sliver of land, which would become the Great Highway.
The shoreline naturally wants to be across the road, where the treatment plant is.
Patrick Barnard, U.S. Geological Survey
The city stabilized the Ocean Beach sand dunes with fencing, and over time the fences gave way to hardened barriers such as the O’Shaughnessy Seawall that starts near the Beach Chalet. Today, there is more than 10,000 feet of seawall along Ocean Beach to combat erosion, but the city has had to haul in sand periodically to curtail beach loss.
Beach “nourishment,” as it’s known, has become an annual ritual as storms and tides grow more intense. Between 1997 and 2019, the city carted a total of 307,000 cubic yards of sand to cover the beach and bluffs south of Sloat. The 2009–10 storms chewed away 40 feet of beach and bluffs, destroying a parking lot and part of the Great Highway extension. The city countered with sandbags and huge chunks of rock, but these were all stopgap measures.
In 2011, the city asked for a permit to continue beach nourishment south of Sloat, but the California Coastal Commission rejected the request, forcing SF to look at longer term solutions to deal with rising seas.
Ocean Beach is part of a coastal system called the San Francisco Littoral Cell that stretches from Fort Point at the Golden Gate down to Point San Pedro off Pacifica. Within this system, tides and currents naturally deposit sand on some beaches while eroding others.
The pressure from erosion is most acute on Ocean Beach from Sloat Boulevard to parts south, which saw as much as 4.3 feet of annual loss between 2004 and 2020, according to USGS studies. “The shoreline naturally wants to be across the road where the treatment plant is,” Barnard points out.
Seawall debate
The erosion threatens to expose a wastewater tunnel that runs under the Great Highway extension. Before the plant’s completion in 1993 to comply with the Clean Water Act, SF’s wastewater was prone to overflows during storms. As part of the construction, the Great Highway was redesigned and narrowed.
Even if Prop I fails and the extension is permanently removed, the preferred plan calls for a seawall to protect the wastewater tunnel. It would be low profile, however, and buried by sand that would need regular replenishment.
Some environmentalists believe that any seawall is a bad idea. Earlier this year, Surfider Foundation’s Laura Walsh told The Frisc that she would prefer more true sand dunes, not a “highly engineered” buried wall that she expects will require frequent maintenance.
Still, the permanent road closure would make room for a softer bluff to absorb wave energy while providing habitat for threatened species such as the bank swallow.
Bay Area communities like Tiburon are removing seawalls and other hard barriers in favor of natural topology like sloped shorelines, vegetation, or marshland to lessen the threats of flooding and erosion. The Ocean Beach plan is also a type of managed retreat.
If Prop I prevails and requires preservation of the Great Highway extension, there will be hurdles. The Board of Supervisors and mayor would have to approve the extra spending. The California Coastal Commission also has jurisdiction, and it’s aware of the engineering and environmental implications of a conventional seawall. “The commission has approved seawalls in the past only under specific circumstances, but has not made any decisions about this particular project,” Noaki Schwartz, deputy director of public affairs, environmental justice and tribal affairs, tells The Frisc.
Barnard of the USGS acknowledges the difficult struggle to decide what infrastructure, or even homes, to move in the face of sea-level rise. But for San Francisco, one option will almost certainly not be on the table. Moving the $220 million sewage treatment plant and the 14-foot pipes is “almost cost-prohibitive,” Barnard says.
Under the shortest timeline, the extension will be gone and a radically new stretch of coast will be ready in 2028. But a Prop I victory will change all that. Even if its aims are thwarted by the Coastal Commission or other challenges, a solution could be delayed years. And the sea will keep rising.
