Walnut Creek-area BART riders faced three days of delays after a fire at a 40-year-old substation near Daly City knocked out service across multiple lines.

BART Assistant General Manager Sylvia Lamb told the agency's Board of Directors on Thursday, Sept. 10, that a faulty cable on an aerial structure caused a main breaker to short, sparking the fire in electrical equipment at the substation. Lamb called it a clear failure caused by aging equipment, KQED reported.

BART Chief Communications Officer Alicia Trost told KQED the substation is at least 40 years old and the cable at least 30. Both are original to when BART's "W Line" was built.

The fire broke out about 7:45 p.m. Tuesday, Sept. 8, according to the Mercury News. North County Fire and San Francisco Fire crews extinguished the blaze. No one was injured. BART temporarily closed the Transbay Tube that night.

The damage cascaded through the week. On Wednesday, Sept. 9, the Blue Line had limited service between Dublin/Pleasanton and 24th Street/Mission in San Francisco. The Green Line also ran limited service. By Thursday, BART suspended all Green Line service between Berryessa and Daly City to reduce congestion while crews repaired train control equipment, according to CBS News Bay Area.

A separate train-control issue near South San Francisco also shut down service between San Bruno and Colma for about 90 minutes Thursday morning, stranding riders headed to San Francisco International Airport.

Four of BART's five lines converge at Daly City station.

Lamb told board members the Daly City substation had already been flagged as one of the "top five" needing replacement out of BART's 74 total substations. Seventy percent of those substations are original equipment. Repairing one costs $3 million to $5 million. Replacing one costs $60 million. BART has funding to replace only one.

Lamb said her team has now moved the Daly City substation to the top of the replacement list. BART Board Vice President Edward Wright pressed on the trade-offs.

"What will not be done in response to us putting this at the top of the list?" Wright said. "What other risks are we now creating that we were previously able to address?"

BART also faces a $375 million structural operating deficit beginning in fiscal year 2027, according to a Contra Costa County Civil Grand Jury report. Senate Bill 63, the Connect Bay Area Act, authorized a regional sales tax measure for the November 2026 ballot that BART has identified as its primary mechanism to address that deficit.

An HVAC failure in a train control room, likely caused by the regional heat wave, also caused delays in the Daly City area earlier on Tuesday. Lamb said the HVAC failure and the substation fire did not appear to be related. BART placed a 2-ton portable air conditioning unit in the control room while it waited for repairs.

As of Thursday, trains were still running at reduced speeds between Daly City and Colma. BART had not announced a timeline for complete repairs or the return to full five-line service.

Riders can check real-time service alerts at bart.gov or through the BART app.