The US Chemical Safety Board (CSB) has concluded that a 2015 explosion at a Torrance, California, refinery then owned by ExxonMobil could have been prevented, the agency concluded in a report issued on 3 May.
“This explosion and near miss should not have happened,” said CSB Chair Vanessa Allen Sutherland in a statement. “The CSB’s report concludes the unit was operating without proper procedures.”
The federal watchdog found that weaknesses in the Torrance refinery’s safety program led to the blast.
The blast blew a large piece of debris 80 ft to nearby alkylation unit settler tanks containing toxic hydrofluoric acid, which the board called a “near-miss event.”
Four workers suffered minor injuries, and part of the refinery underwent a lengthy shutdown, contributing to a spike in the state’s gasoline prices.
The Torrance refinery supplies 20% of the gasoline in Southern California and 10% statewide.
The explosion occurred when volatile hydrocarbons flowed backward through an idled gasoline-producing fluidic catalytic cracking unit (FCCU) to a pollution control device called an electrostatic precipitator (ESP), the CSB found.
The generation of sparks by the ESP ignited the hydrocarbons setting off the explosion.
The board, which has no regulatory authority and does not assess fines, found that the FCCU was operating without pre-established limits for a shutdown.
The agency also said Exxon relied on safeguards that it could not be sure were working and that a critical safeguard failed.
Exxon said in a statement: “We are confident we understand the cause of the blast and have worked cooperatively with the Chemical Safety Board and staff to fully understand their findings and recommendations.”