Per a BART staff report, the 1974-constructed Transbay Tube that runs for more than 3 miles beneath the San Francisco Bay is in need of an update “in anticipation of a future major earthquake in the San Francisco Bay Area.” The transit agency voted on the major retrofit today that was to cost between $229 million and $440 million, varying based on several bids. That was approved according to CBS 5, but work that would begin in July of 2018 could take more than two years to complete, creating cuts to early morning and late night service at that time.

As a BART spokesperson tells the Examiner, there's nothing to worry about right away: “Although the tube is structurally sound, in a very large, very rare earthquake event (greater than every 500 years), the outer shell and concrete liner are predicted to crack, causing leakage.” The retrofit would add an inner lining of steel to "prevent or slow leakage" in the case of that (very) "Big One."

According to the Ex, the base bid for the project was $229 million, and the top three bids selected by BART district staff were for $267 million, $293 million, and $440 million. The lowest of those three won out, a joint venture of Oakland-based Shimmick Construction and Pleasanton-based California Engineering Contractors. Funding for the update will come from general obligation bonds issued by BART approved by Bay Area voters in 2004, the Ex indicates.

While changes to transit schedules aren't set in stone, according to CBS5, more than 2,600 peopl take BART between 4 and 5 a.m., hours that would likely be disrupted. Many of them are low-income and minority riders. Per the news channel, "during the first hour of service, 66 percent of riders are minorities, compared to 56 percent over the entire day, and 37 percent make less than $50,000 a year, compared to 26 percent during the rest of the day, according to BART."

“These are not the stock brokers coming from central Contra Costa County,” said one BART Director, Joel Keller. “These are working people going into the Bay Area to provide service.”

Meanwhile, more immediate changes are on the way to the aging transit system. Those come thanks to the passage of District Measure RR. Among the largest chunks of that $3.5 billion bond is $625 million that will go toward renewing 90 mies of BART track. In total, there are 107 miles of track throughout the system.

Related: BART Hopes To Use Clay To Seal Leaky Tunnels Known As 'The Rainforest'