The fire, which started at 12:15 a.m. Thursday in the chemical plant at the southeast section of the refinery, was doused shortly after 7 a.m., Golden Eagle spokesman Jon Ballesteros said. No workers were injured.
Ballesteros did not say how large the tank was, but said refinery firefighters had to let most of the fire burn out because chemicals in the tank were flammable. Gasoline burned out of the tank that also held sulfuric acid, Ballesteros said.
"An investigation will begin once we make sure the tank is structurally sound," Ballesteros said.
He said the refinery continued to operate during the fire and was at full production during the day Thursday.
The Bay Area Air Quality Management District also will conduct an investigation to assess the fire's effects on air quality.
Preliminary results are expected as soon as today, but a full investigation will take weeks to complete, said district spokeswoman Luna Salaver.
She said two air quality inspectors were sent to investigate the fire. Air samples taken by Contra Costa County health officials will be used to measure ambient air.
Most of the smoke traveled straight into the sky and didn't stay close to the ground. Because of that, Salaver said, the smoke will have a minimal effect on people who live nearby.
Until the investigation is complete, she declined to speculate on what the burning materials would do to the environment.
"Smoke at any level is dangerous; whether it is cigarette smoke or anything else, you don't want to inhale it," she said. "When it is not close to the ground and not close to breathing space, it is less likely to harm people."
Although county health workers don't expect residents to suffer from the smoke, nearby communities were warned because slight winds caused smoke to shift eastward momentarily.
County health officials issued an advisory to North Concord, Avon, Clyde and Vine Hill, especially to people who might have respiratory problems, said Contra Costa Health Services spokesman Randy Sawyer.
"I don't expect people who live by the refinery to have any problems," he said.
Sawyer said the advisory asked residents to wash any irritated areas and to shut the doors and windows of their homes so they don't breathe smoke. Health Services issued an "all clear" to residents at 8:20 a.m.
The Golden Eagle Refinery has had a history of incidents.
In the 1990s, when the company was owned by Tosco Corp., fires killed five people and injured dozens more. The company had a reputation of having some of the oldest equipment in the region.
Last year, Tesoro Refinery and Marketing Co. bought the refinery from Tosco for $1.1 billion. The company also bought new equipment to improve operations.
