Nearly 5,000 residents have already filed claims against the oil giant after the Aug. 6 fire, which sent 15,000 people to local hospitals.
Attorneys John Burris of Oakland and Tony Buzbee of Houston revealed the numbers as they filed an amended lawsuit Nov. 27 in Contra Costa County Superior Court in Richmond.
The claims filed Tuesday claim Chevron, the world's third largest oil company, failed to ensure the refinery was operating safely before the fire broke out when an already corroded oil pipe ruptured, according to the San Francisco Chronicle newspaper.
The lawsuits also claim that Chevron failed to alert residents that the pipe that eventually ruptured had been leaking for hours before the fire.
Chevron voluntarily set up a claims procedure for residents of Richmond, San Pablo and other nearby cities, and pledged to pay for fire-related medical bills and property damage.
"We do not believe any lawsuits are necessary, and we will defend them vigorously," the company said.
Smoke from the fire was visible in Solano County and many Vallejo and Benicia residents complained of ill effects.
The lawsuit claims an Oct. 2011 fire at the San Francisco Bay refinery put Chevron on notice that pipes needed replacing after a worker complained about corrosion.
Chevron's Richmond refinery refines 240,000 barrels of crude oil daily and is the largest oil refinery in the San Francisco Bay Area.