(Adds comments from Exxon, CSB conference call)
By Erwin Seba and Liz Hampton
HOUSTON May 3 The U.S. Chemical Safety Board
(CSB) has concluded that a 2015 explosion at a Torrance,
California, refinery then owned by Exxon Mobil Corp
could have been prevented, the agency concluded in a report
issued on Wednesday.
"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
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 feet (24.38 m) 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 percent of the gasoline in
Southern California and 10 percent 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
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."
Regarding the hydrofluoric acid, Exxon said, "There was no
evidence the Feb. 18 incident posed any risk to the modified
hydrofluoric acid alkylation unit or risk of harm to the
Residents near the refinery want local and state officials
to ban the use of hydrofluoric acid in making octane-boosting
Hydrofluoric acid is a highly toxic chemical that can kill
or seriously injure at a concentration of 30 parts per million.
As a gas it forms a ground-hugging cloud.
The board said it has asked a federal court to enforce
subpoenas requiring Exxon to provide information about
safeguards to prevent or mitigate a release of hydrofluoric
Exxon said it "strongly disagrees" with any statement
questioning its responsiveness or cooperation with the
"We offered to make additional documents available if the
CSB could provide a sufficient basis for the documents and
agreed to respect commercial confidentiality, which they have
not done," a spokesman said Wednesday.
PBF Energy Inc, which acquired the refinery last
year, "has already implemented a number of measures that address
the CSB's recommendations," PBF spokesman Michael Karlovich said
in a statement. "We plan to complete two studies later this year
that will address the remaining recommendations."
The CSB determines root causes of chemical plant accidents
and provides recommendations to companies, industry
organizations and regulatory agencies.
(Reporting by Erwin Seba and Liz Hampton in Houston; editing by
Gary McWilliams and Matthew Lewis)