There was a smaller fire just put out shortly before the massive blaze at a Chevron Corp. refinery in Northern California last month.
The report given to Contra Costa County officials by Chevron on Wednesday said there was a small fire at the refinery about 10 minutes before the larger blaze.
The blaze knocked an important refinery unit offline, reducing the facility’s production and sending thousands of people to hospitals with breathing and eye irritation complaints.
The cause of the massive fire was from a leaking 8-inch pipe but investigators also were looking into the composition of a white cloud that formed minutes before the blaze. The report casts doubt on whether the cloud consisted of flammable hydrocarbon vapor, suggesting it was mostly steam from firefighters knocking down the smaller blaze.
The fire broke out in the No. 4 crude unit of the 240,000-barrel-per-day refinery after 600-degree hydrocarbon liquid leaked from the 8-inch pipe. Four workers suffered minor injuries, and more than 14,000 residents visited area hospitals in the subsequent weeks, complaining of respiratory problems and other discomforts.
An investigation and report into the incident may take more than a year to complete but investigators said it will be a comprehensive safety and maintenance evaluation.