While BART has brought in engineers to probe a recent rash of smoky mishaps in the Transbay Tube, transit agency officials acknowledge to NBC Bay Area’s Investigative Unit that it gave up five years ago on cleaning dust its own officials blamed in at least two prior “flashover” incidents in the subway.
At the platform at BART’s Rockridge station in Oakland, riders can easily see some of the 100,000 insulators in the transit system. The ceramic devices serve a vital function – they keep power from flowing from the high voltage third rail into the ground.
When clean, they are normally white or gray, but over time, brownish iron dust is inevitably deposited by the action of passing trains.
At Rockridge, that caked-on layer is on full display. When tracks are outdoors, the layer is normally harmless. But when the insulators get dirty and fail inside confined subway areas, it poses a greater risk, according to a retired BART official.
“You’ve got to clean them,” says Barney Smits, who headed fire safety at the agency for two decades before leaving in 2023. He says left unchecked, the caked-on dust can trigger a short circuit, followed by a so-called flashover explosion that can pose a danger inside confined spaces of the subway.
“This is a much more safety risk situation,” he says, “because you’re talking about 1,000 volts DC, and you’re talking about a potential arc and a potential flashover and a potential fire.”
BART says an exploding insulator filled the Transbay Tube with smoke in late August, forcing a train operator to stop inside the subway. As the train ventilation system drew in more smoke, panicked passengers tried to get out. Eventually, the smoke cleared, and the train safely reached the East Bay.
BART officials say they don’t know what triggered that insulator to explode, but Smits says dust is one likely explanation. He points out that BART officials cited the need to clean insulators in the subway after two flashover incidents back in 2015. No one was injured in either event.
Yet despite the those earlier efforts, BART officials recently acknowledged to the Investigative Unit that the agency stopped cleaning subway track insulators regularly five years ago.
The agency had previously used dry ice to clean away the dust, but BART officials stopped that method in 2020, because of concerns of premature wear on the ceramic surface of the insulators. Instead, the agency says, it has opted to inspect and replace at-risk insulators.
After the incident in August, however, BART officials told the agency’s governing board that they’re evaluating whether to go back to cleaning again. That’s a move BART board member Liz Ames says can’t come soon enough – since she has since learned from BART staff that to be effective, insulator cleaning should be performed about every two years.
“At this point, we need to have a preventive program, a maintenance program, to clean all the insulators,” she said, adding that she hopes BART can act in time to prevent another nightmare scenario like what happened Aug. 29th.
“I don’t think anybody wants to see that again — it’s terrifying,” she said.
“I think cleaning them is a far better approach,” adds Smits, who notes that catching up on the cleaning will be a challenge since crews only have about two hours each night to perform critical maintenance due to the time it takes to prepare to work safely on the system.
Meanwhile, BART officials say they expect the expert report on the recent system mishaps – including both the August incident and several in October — to be complete by January.
Source: NBC Bay Area