An inspection contractor found a chemical tank at a Washington state paper mill "not fit for continued service" 10 months before it failed in May.
The refinery tells the fire department that the flare stacks will be operating intermittently for several hours.
Air monitoring is underway as crews contain a fire at the Valero refinery in Benicia Monday morning that sent large plumes of smoke into the air and caused shelter-in-place orders for several hours.
Experts say Valero's possible closure of the Benicia refinery, which produces about 9% of California's gas, is "quite disturbing," and the state would need to import more gas to keep prices from rising too drastically.
More than 400 people are employed there, and it's one of Solano County's largest employers.
The plume from the chemical reaction that followed the outbreak of the fire could be seen for miles