While the Bay Area Rapid Transit system is still struggling financially in the wake of the COVID-19 pandemic, it announced Monday that it has completed its two-decade seismic strengthening of the Transbay Tube and the rest of the system.
The transit system's $1.5 billion seismic retrofit project started 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 started in 2017, and the announcement Monday of its completion came on the 50th anniversary of the first BART train to travel through the 3.6-mile tube — a pair of segmented concrete tunnels with an an access and maintenance gallery in the middle that were submerged deep into the bay muck and connected.
Over the past five years, crews installed steel plates on the interior of the tube along with a more powerful pumping system to handle any leaks that could occur during a major earthquake.
The retrofitted tube isn't designed to withstand any specific magnitude of earthquake — those standards are no longer used, BART spokesperson Jim Allison said — but to protect the lives of passengers and remain operable in the event of the strongest temblor expected in 1,000 years.
BART General Manager Bob Powers made the announcement in the agency's media center.
"The Transbay Tube is BART's No. 1 asset and one of the most important assets in the Bay Area," he said.
When it was built, the tube was considered a miracle of engineering and an attraction that lured not only commuters but wide-eyed kids who wanted to take a ride 135 feet beneath the bay.
Until 2010, it was the longest immersed tube in the world, according to BART.
"We take it for granted now, but it was mind-blowing back in the '70s," BART Board of Directors President Bevan Dufty said, standing in front of a green screen while a nearby video screen substituted background video of a trip into the tube. "The Transbay Tube is not just a cool stretch of submerged train tracks, it's the backbone of Bay Area public transit."
The retrofit of the tube required partial shutdowns, during which nighttime and weekend trains shared a single track during a period of the work.
Allison said the interior of most of the tube has had its walls wrapped with steel plates. Although leaks in the tube are rare and its interior is dry and even dusty, cracking is possible in the event of an extremely large earthquake and leaks are possible, Allison said.
New, "more robust" pumps were installed to handle potential leaks, he said.
Dufty said it was important to mark the completion of the retrofit work and the tube's 50th anniversary "to remind our riders of the importance of a strong, vibrant system."
And with ridership and fare revenue down sharply since the pandemic, he said BART will have to seek other sources of funding — including local taxes.
"We will have to go to voters for a funding measure, likely in 2026," he said.
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