Shared from the 9/9/2021 San Francisco Chronicle eEdition

Coastline in flux

Giant sand berm to protect Ocean Beach from climate change

Photos by Amy Osborne / Special to The Chronicle

Bulldozers and excavators move sand in an effort to shield San Francisco’s southern coast from rising sea levels.


An offshore dredger pumps sand through a pipe laid by the the city of San Francisco and the Army Corp of Engineers.

Amy Osborne / Special to The Chronicle

Roads, underground infrastructure and a major city wastewater treatment plant are at risk of being swallowed by the sea.

For the past two weeks, a 375-foot dredge ship has been cruising off the coast of San Francisco, ferrying thousands of tons of sand from the seafloor to Ocean Beach and marking the city’s latest effort to confront climate change.

The ambitious $7 million project is designed to anchor the city’s rapidly eroding southern shoreline with a 3,000-foot-long, 30-foot-tall sand berm.

While a series of dunes and seawalls has protected the northern stretch of Ocean Beach from rising seas and increasingly strong storm surges, the coast south of Sloat Boulevard has remained more vulnerable to climate-driven forces. Roads, underground infrastructure and a major city wastewater treatment plant are at risk of being swallowed by the sea.

The giant sand berm, expected to be completed by the end of the month, is the biggest effort yet to stabilize the area, and it’s part of ongoing work that ultimately calls for removing the Great Highway south of Sloat Boulevard. City, state and federal officials involved with the work say they may be able to shore up the coast, but they concede the road is no match for the changing climate.

“It will be a big dune with a coastal trail that ties into the bluffs at Fort Funston,” said Peter Mull, a project manager for the U.S. Army Corps of Engineers, as he stood above the windswept shoreline on Wednesday. “It will be a wider beach and help provide protection.”

This week the work, being managed by the Army Corps at the direction of the San Francisco Public Utilities Commission, was proceeding quickly. Several bulldozers and earth movers pushed sand freshly deposited from the sea into the emerging 100-foot thick fortification. The beach between Sloat Boulevard and Fort Funston, property of the National Park Service, was cordoned off by chain-link fence. An occasional pedestrian ogled the construction from afar.

“I remember there used to be a parking lot out there,” said one passerby, testifying to the decades of erosion that has been hastened by climate change.

Officials with the SFPUC say it’s only a matter of time before the pipes running in and out of the adjacent Oceanside Water Pollution Control Plant, which are buried beneath the sand, are unearthed. The most worrisome is what’s known as the Lake Merced Tunnel, a 14-foot diameter pipe under the Great Highway that carries dirty water from Lake Merced to the treatment plant for processing before releasing it into the sea.

“If that gets exposed, it could crack,” said Anna Roche, a project manager and climate adviser at the SFPUC. “If it ruptures we’re spilling stormwater and sewage onto the beach.”

The main contractor for the project, the Dutra Group, has been running the large hopper dredge, named the Stuyvesant, 24 hours a day since the end of August. The dredge ship uses two long arms to reach to the seafloor about a half mile out and suction sand from the bottom of the shipping channel used by boats sailing in and out of the Golden Gate.

Once the Stuyvesant fills its 10,200-square-yard hold, it carries the sand closer to Ocean Beach, where tugboats secure it to a pipeline that carries the load ashore. About 270,000 cubic yards of sand is to be deposited on the beach.

The sand berm is expected to last four to six years, Mull said, though its useful life is actually much longer. If the sand gets washed away, which it will eventually, it will move to the seafloor, where it will act as a buffer for incoming waves while some sand will make its way back to the beach.

“Even though it may seem lost, it’s not,” Mull said. “It’s nourishing the offshore sandbars and helping the system work.”

The Army Corps generally dredges the shipping channel once a year, so the berm can also be reinforced with new sand annually.

Historically, sand moved naturally on and off the beach, but development along the shoreline has stymied that process, limiting the input of sand and exacerbating erosion. Rising seas and more extreme storms have only increased the wear and tear on the coast.

Because of this, the Great Highway between Sloat and Skyline Boulevard is expected to be removed in late 2023. First, its intersection at Sloat must be reworked, and access to the adjacent San Francisco Zoo must be reconfigured

“What that does is open up space for sea-level rise and create some open space elements,” said Roche of the SFPUC.

Without the road, the area is expected to become more of a park, with recreational trails as well as native landscaping and habitat for nesting birds.

This summer’s work is being funded by the Army Corps, which is footing 65% of the bill since the dredging needs to be done with or without the berm project, and the SFPUC, which is covering the balance. The Golden Gate National Recreation Area, U.S. Fish & Wildlife Service, National Marine Fisheries Service, California Coastal Commission and California Water Quality Control Board have all been involved in the planning.

“San Francisco is committed to improving the resiliency of our environment, community spaces and infrastructure from the ever-increasing impacts of climate change,” San Francisco Mayor London Breed said in a statement. “We must continue implementing sustainable near-term solutions like this Ocean Beach project as we advance our long-term climate solutions for the area.”

Kurtis Alexander is a San Francisco Chronicle staff writer. Email: Twitter: @kurtisalexander

“We must continue implementing sustainable near-term solutions like this Ocean Beach project as we advance our long-term climate solutions for the area.”
S.F. Mayor London Breed

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