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Two people walk from Pier 14 visible through deteriorating handrails at the sea wall along the Embarcadero in San Francisco. Components of the wall and railings have begun to deteriorate due to the saltwater and age.

A pedicab passes by a repaired handrail at the sea wall along the Embarcadero in San Francisco.

UPDATE: S.F.’s plan to protect the city from sea-level rise will ‘set the stage for our future shoreline’

There are worlds of difference between a rotting structure at Fisherman’s Wharf, the iconic drama of the Ferry Building and the shadowed concrete underneath the Bay Bridge where two piers meet the aged Embarcadero seawall.

What they share is a vulnerability to earthquakes and sea level rise along an artificial shoreline that’s more than a century old. They also have a common owner — the Port of San Francisco, which has the costly job of preparing that shoreline for a host of 21st century challenges where the learning curve seems to get steeper each year.

Now, nearly four years after voters approved a $425 million bond to prepare the seawall and the structures along it for what the future might bring, the port has selected the first six projects to pursue. Construction on the most straightforward could start in 2024, officials say. But the six are only a start of a much larger effort — one that likely will extend for decades, and at costs exceeding $5 billion.

“It’s a massive undertaking,” Steven Reel, deputy manager of the port’s waterfront resilience program, told the Port Commission in a status report on Tuesday. “There are no easy fixes.”

The six that will be the focus of planning effort in the coming months — out of 23 potential “early projects” released last winter — are the first to be assessed in terms of what options might be available to improve seismic protection and start preparing for sea level rise. More detailed work will follow, but the initial studies showcase the range of difficulties along the 3-mile constructed shoreline between Mission Creek and Fisherman’s Wharf. And because of the haphazard way the seawall was built between 1878 and 1916, coupled with more recent changes, no two stretches are alike.

A cracked hand rail at the sea wall along the Embarcadero in San Francisco. In some areas, chain-link fences are in place until permanent repairs can be made.

In the case of “wharf J9” tucked behind Jefferson Street at the edge of the Fisherman’s Wharf lagoon, the obvious problem is the decrepit state of the now-closed 1919 shed. The larger danger is that a big earthquake could cause the muddy landfill below it to liquefy. The landfill needs to be stabilized, while the wharf can be torn out or rebuilt — and if the latter, improved for new fishing berths.

Things are different along the 900-foot section of seawall that runs below the Bay Bridge and connects to Piers 24 ½ and 28 ½.

Although the soil conditions are good by Embarcadero standards, the tall concrete barrier that caps this section of the seawall is particularly vulnerable to damage from a major temblor. That in turn could undermine the strength of the two piers. The question becomes whether to concentrate on seismic upgrades, or widen the lens to examine ways to also prepare for sea level rise and include more piers to the south.

A seawall stands along San Francisco’s Embarcadero in 2021.

The most ambitious of the six projects will focus on the Ferry Building.

The 659-foot-long, 245-foot-tall landmark was renovated two decades ago, and its vaulted concrete foundation shrugged off major earthquakes in 1906 and 1989. But this portion of the Embarcadero has settled by as much as 2 feet since the seawall was built in the 1890s, with nothing but thick mud below — part of why the staff report that accompanied Tuesday’s presentation calls it “among the most complex areas of the waterfront to improve.”

Five different engineering options will be studied during the next 18 months or so, and any solution is sure to be costly. But the desire to protect an internationally known civic icon, and ensure the stability of the adjacent ferry gates that are essential to civic emergency relief efforts in a major disaster, explain why this spot is a first-round priority.

“It’s such a critical resource,” Elaine Forbes, the executive director of the port, said before the meeting. “The Ferry Building has a very robust foundation, but there are things that can be done to make it even more resilient.”

The San Francisco Ferry Building as seen through a crumbling section of Pier 1 last year.

The other three projects pose their own dilemmas.

One involves reducing the risk of floods between Pier 5, north of the Ferry Building, and Rincon Park to the south. This is the segment of the seawall where extra-high “king tides” in the winter already wash across lanes of the Embarcadero roadway, and such flooding could become a regular feature by 2040 under the state’s sea level rise projections.

The current conditions have accelerated the decay of the concrete railings south of Pier 14 — so much so that chain-link fencing has been added along stretches of the popular promenade with its open bay views. The current aim is to decide on where “the line of flood defense” should be installed, whether at water’s edge or within the path of the present promenade. Short-term protection could also be added, such as solid railings to replace the existing open concrete ones.

The other projects involve Piers 9 and 15: A major earthquake could cause portions of the seawall alongside them to lurch back and forth, damaging the piers and the buildings atop them. This even is true of Pier 15, where the Exploratorium opened in 2013 after a total structural remake.

The engineering analyses and design work in the coming months will determine whether there’s relatively simple work to be done, such as reinforcing the wharves below the pier buildings, or if the seismic joints between piers and seawall should be enlarged — which could disrupt operations at the Exploratorium, a popular visitor destination.

A jogger runs along San Francisco’s Pier 14 in 2021.

Several commissioners listening to the informational presentation on Tuesday asked why major investments like the Exploratorium and the Ferry Building didn’t solve these problems at the time.

“We’re learning much more about seismic risk” and sea level rise-related issues, Forbes said. “There’s a more complex understanding of how the soils will perform.”

John King is The San Francisco Chronicle’s urban design critic. Email: jking@sfchronicle.com Twitter: @johnkingsfchron

John King is The San Francisco Chronicle's urban design critic, taking stock of everything from Salesforce Tower to sea level rise and how the pandemic is redefining public space. A two-time Pulitzer Prize finalist and author of two books on San Francisco architecture, King joined The Chronicle in 1992 and covered City Hall before creating his current post. He is an honorary member of the American Society of Landscape Architects.