Some union representatives arrived early Thursday morning with luggage packed for the long haul. In the meantime, the pressure is building to reach a deal.
On Thursday, California Sens. Dianne Feinstein and Barbara Boxer sent a letter to BART managers and the unions asking them to use the time before Sunday night to reach a contract agreement.
"We urge you to resume negotiations in good faith, end the dispute, and work together to avoid any further disruptions to BART service," the senators wrote. "Any BART service disruption has significant impacts on our region's economy and the hundreds of thousands of commuters who use the system.
BART and its unions headed back to the bargaining table Thursday, for the first time since Gov. Jerry Brown blocked a strike on Sunday and ordered a fact finding board to investigate the heated talks.
"We have the information to hammer out a deal," said Amalgamated Transit Union Local 1555 President Antonette Bryant. "Our team is prepared to stay overnight, around-the-clock."
But that won't be easy. Both sides are still far apart on terms of a new contract. Depending who you ask, they're somewhere between $50 and $100 million.
BART says it's latest offer, a 9 percent raise over four years, is more than fair. They also want employees to pay more for their benefits.
The unions' latest proposal calls for a 5 percent increase over three years, which includes a cost of living increase. The unions are also offering to pay into their pensions and more for health care, but not as much as BART wants.
"We still need an agreement on salaries, we still need an agreement on pensions, we still need an agreement on medical contributions, on overtime work rules, and a plethora of other things," BART spokesperson Alicia Trost said. "But that doesn't mean it can't happen."
Unless there's a breakthrough by Sunday, it seems inevitable that Gov. Brown will order a 60-day cooling off.
In every BART labor dispute between 1988 and 2001, governors have intervened, assigned a board of inquiry for seven days, then issued a 60-day cooling off period which allowed both sides time to reach a deal. In most cases, they have.
"I'm not in agreement with the 60-day cooling off period," Bryant said. "I don't believe we have the right to hold passengers hostage."
A strike could still be called by BART unions.
"We will do our best to give a 72-hour notice," SEIU member Jim Arantes said. "Cause we want the public to be aware and be warned."
We asked riders to deliver their own message to both sides in the BART battle.
"I would say, get it together so we can get to work," one passenger said.
Another added, "I think they have great benefits and they should probably stop complaining about them."
And one commuter pleaded, "Please don't strike, we need you, oh we need BART really bad."
Riders hope someone at the bargaining table is listening.
(The Associated Press contributed to this report)