$425 million bond for seawall repairs heading to S.F. ballot

San Francisco voters are all but certain to be asked in November whether to authorize nearly a half billion dollars in city borrowing to pay for upgrades to the aging Embarcadero seawall.

The Board of Supervisors on Tuesday unanimously approved a $425 million bond measure for the Nov. 6 ballot that city leaders say is vital to securing 3 miles of shoreline from the threat of earthquakes and sea-level rise. A second vote by the board is required before the measure becomes official.

The century-old seawall, which engineers fear will slip 5 feet into the bay in a major earthquake, wraps the city’s northeastern waterfront from Fisherman’s Wharf to Mission Creek and supports an estimated $100 billion worth of property, including the Ferry Building, BART tunnels and part of the Financial District.

“Ultimately, this is a small piece of the overall need that we’re going to have over the next several decades,” said Supervisor Aaron Peskin, noting the city’s increasing demand for infrastructure improvement, particularly in an era of climate change.

Peskin pledged that the bond money for the seawall would be spent judiciously and with plenty of oversight.

The improvement plan hasn’t been fully fleshed out, but city leaders are looking to rebuild parts of the giant wall and perhaps raise it, retrofit the many wharves and piers on the bay, relocate shoreline utilities, and possibly redesign some of the public areas.

The bond measure would cover 85 percent of the $500 million needed for the first of three repair and construction phases for the seawall. The entire project could cost as much as $5 billion. City officials hope that state and federal money will augment the bond funding.

Also this week, the U.S. Army Corps of Engineers announced that its tentative work plan for the year includes studying San Francisco’s seawall and helping look for ways to reduce the local flood risk.

House Minority Leader Nancy Pelosi called the Army Corps’ announcement “a crucial first step” that could lead to “significant federal funding to repair and upgrade the seawall to withstand the next major earthquake and provide vital flood protection from sea level rise.”

The November bond measure would require two-thirds approval from voters to pass.

A survey by the Port of San Francisco in January found that 73 percent of San Francisco residents would back a measure paying for seawall upgrades. Support came in spite of just one in three residents being aware that the wall is a crucial backbone of the city’s waterfront, according to the survey.

In recent decades, the Embarcadero has become an increasingly popular visitor attraction, particularly after construction of AT&T Park, development of the Exploratorium at Pier 15 and renovation of the Ferry Building.

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