The $5 billion plan to save San Francisco from flooding in a major earthquake

Oct. 18--SAN FRANCISCO -- But few might realize that none of those attractions would be possible without a low-profile workhorse that holds everything together: the Embarcadero Seawall, an aging, 3-mile-long, rock-and-concrete structure that rebuffs pounding tides and enabled the city to rise atop the tidal mudflats of San Francisco Bay.

Now, crumbling and threatened by rising seas and potential collapse in a major earthquake, the seawall can be found atop the city's ballot in the Nov. 6 election. San Francisco voters will consider Proposition A, a $425 million bond measure to begin work on an enormous, 30-year, $5 billion project to bring the 19th century structure into the 21st century.

"It is a massive investment into something that nobody can see. But it is vitally important," said San Francisco Supervisor Aaron Peskin. "The seawall took a generation to build. It is going to take that long to raise and strengthen it."

Under the plan, if approved by voters by a two-thirds margin, the city and the Port of San Francisco would shore up the most vulnerable sections, with construction starting in 2021, and begin a plan for the renovation of the entire waterfront structure, which stretches from AT&T Park to Fisherman's Wharf.

"Basically it's a retaining wall. It's holding the city in place," said Lindy Lowe, resilience program director for the Port of San Francisco. "It has done an amazing job for 100 years, but we can't expect that for much longer."

The wall was built between 1878 and 1915, before modern engineering standards. Crews dug a 100-foot wide trench in the bay mud, 30 feet deep, then filled it with rocks. They built a concrete wall on top and drove in wooden pilings to construct piers still used by cruise ships, ferry boats, shops and restaurants.

Much of San Francisco's waterfront, along with the Embarcadero roadway and its Financial District -- including the Transamerica Pyramid, the Ferry Building, the new Salesforce Tower, and the world headquarters of the Gap, Levi's and PG&E -- were built on top of reclaimed land. Before the wall, it was a muddy marsh that over time was filled in with brick, rock and sand as settlers looked to expand the city.

That filling began in the Gold Rush. Until then, ships would sail to the sleepy Mexican town of Yerba Buena, drop anchor, and move their goods and people ashore in shallow barges and rowboats.

But after James Marshall discovered gold at Sutter's Mill in the Sierra Nevada foothills in 1848, tens of thousands of fortune-seekers rushed in from around the world.

Ships of varying degrees of seaworthiness were abandoned in the mudflats. Some became saloons or boarding houses.

"Sailors came here and the crews basically jumped ship to try their hand in the gold fields," said David Pelfrey, a supervisory ranger and historian at the San Francisco Maritime National Historic Park.

Many of the ships burned. Others rotted. By the early 1850s, land speculators regularly hauled wagons full of rock, bricks, sand and garbage to cover them and create waterfront lots. The city spread seaward. The first six blocks of Market Street, for example, were once underwater. At least 35 old wooden ships lie under downtown San Francisco's streets. They are regularly discovered when construction crews dig foundations for new buildings.

After an early seawall was built in the 1860s, the state Board of Harbor Commissioners began work on the present-day structure in 1878, giving rise to a flourishing modern waterfront. That allowed San Francisco to expand trade with the Far East, the East Coast and everywhere in between. Today, Oakland dominates commercial shipping, which has shifted to massive container ships.

"California was like a land of Oz in the 19th century," Pelfrey said. "There was the Gold Rush, and agriculture and timber. You needed the seawall to create an efficient network to get all of these goods transported and distributed around the world. It was crucial to San Francisco's growth."

But now the bill is coming due. A seismic study commissioned by the Port of San Francisco in 2016 concluded the seawall "sits atop weak native soils," and has a "greater than expected risk" of collapse in a big earthquake. A major quake could liquefy soil and push the wall forward by five feet or more, it found. That could collapse the Embarcadero roadway, destroy buildings, cause piers to fail and wreck sewer, water, gas and electric lines underground.

The other major problem is sea level rise. San Francisco Bay already has risen 8 inches since 1900. In recent years, during high tides in storms, waves have crashed over the seawall, flooding roads.

As the climate continues to warm, scientists project the bay will rise up to two feet more by 2050 and five feet by 2100.

Planners are concerned that during a major winter storm, waves could flood the Financial District, sending water pouring into the BART Embarcadero station and the Muni light rail tunnels nearby, similar to Superstorm Sandy, which flooded parts of the New York City subway system in 2012.

"This is the shape of things to come," said David Lewis, executive director of Save the Bay, an Oakland environmental group that supports Prop A. "It should be a wake-up call for other cities. There is an urgency to getting out ahead of this threat."

Detailed studies have not yet been done, but the wall will need to be raised several feet in many areas. In others, it also could be shored up with "jet grouting," a process in which holes are drilled down to the foundation and filled with cement. Other parts would have concrete added, and piers and shorefront buildings would be retrofitted to handle seismic shaking.

City and port officials are hoping the rest of the money for the job will come from state and federal sources, along with local property taxes or other San Francisco funds. Proposition A, which was put on the ballot by the San Francisco Board of Supervisors, has been endorsed by both the San Francisco Democratic Party and Republican Party, along with the San Francisco Chamber of Commerce, the Sierra Club, Save the Bay and the San Francisco Labor Council.

The "no" argument on the ballot is signed by "Starchild," who is described as the "Libertarian Party of San Francisco outreach director."

"If businesses leasing waterfront property from the Port Commission want those properties to be better protected against bay water spillover," Starchild wrote, "they can pay for it themselves."

The measure would increase San Francisco property taxes by $130 a year per $1 million of assessed value, but because other taxes are sunsetting, it would not increase residents' bills if it passes.

For Peskin, whose district includes Fisherman's Wharf, repairing the seawall is a job that affects public and private property, and has to be done. The U.S. Geological Survey says there is a 72 percent chance of one or more 6.7 magnitude or stronger earthquakes striking the Bay Area in the next 25 years.

"This is literally an investment in San Francisco surviving in the next 100 years," he said.

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