California: BART completes $1.5 billion earthquake-resistant upgrade of Transbay Tube and system

While the Bay Area Rapid Transit system is still struggling financially as a result of the COVID-19 pandemic, it announced Monday that two decades of earthquake-resistant reinforcement of the Transbay Tube and the rest of the system has been completed.

The transit system’s $1.5 billion earthquake-proofing project began in 2004 and included 74 miles of track and 34 stations and structures in addition to the Transbay Tube, which runs along the bottom of San Francisco Bay between Oakland and San Francisco.

Work on the tube began in 2017, and the announcement of its completion came Monday on the 50th anniversary of the first BART train traveling through the 3.6-mile-long tube – a pair of segmented concrete tunnels with an access and maintenance tunnel in the middle, sunk deep in the bay’s mud and connected to each other.

Over the past five years, steel plates and a more powerful pumping system have been installed on the inside of the tube to fix any leaks that might occur during a major earthquake.

The retrofitted subway is not designed to withstand earthquakes of a specific magnitude – those standards are no longer used, BART spokesman Jim Allison said – but is designed to protect passengers’ lives and remain operational in the event of the strongest earthquake expected in 1,000 years.

BART General Manager Bob Powers made the announcement at the agency’s media center.

“The Transbay Tube is BART’s most important asset and one of the most important assets in the Bay Area,” he said.

When the subway was built, it was considered a marvel of engineering and an attraction that attracted not only commuters but also wide-eyed children who wanted to take a ride 41 meters beneath the bay.

Until 2010, it was the longest diving tube in the world, according to BART.

“We take it for granted today, but in the ’70s it was mind-blowing,” said Bevan Dufty, chairman of BART’s board of directors, standing in front of a green screen as a nearby video screen showed background video of a subway ride. “The Transbay Tube isn’t just a cool stretch of submerged railroad tracks, it’s the backbone of public transit in the Bay Area.”

The reconstruction of the tunnel required partial closures, with night and weekend trains sharing a track for a certain period of time.

According to Allison, the interior walls of most of the tube are encased in steel plates. Although leaks rarely occur in the tube and the interior is dry and even dusty, in the event of an extremely strong earthquake, cracks could form and leaks could occur, Allison said.

To fix possible leaks, new, “more robust” pumps have been installed, he said.

Dufty said it was important to celebrate the completion of the reconstruction and the subway’s 50th anniversary “to remind our passengers of the importance of a strong, dynamic system.”

And with ridership and fare revenues having declined sharply since the pandemic, BART must look for other sources of funding, including local taxes.

“We will have to ask voters for a funding measure, probably in 2026,” he said.

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