A combination of technical failures and unsafe operational practices at the Marathon Martinez Renewables facility in Martinez, California, led to a November 19, 2023, fire, according to a final report issued March 13 by the U.S. Chemical Safety and Hazard Investigation Board (CSB).
During the facility’s initial start-up of a renewable diesel hydroprocessing unit, a metal tube in a fired heater ruptured, releasing renewable diesel and hydrogen, which sparked the fire.
The resulting fire caused approximately $350 million in property damage to the facility, and an employee suffered third-degree burns over most of his face and body. The processing unit was shut down for nearly a year before restarting operations in November 2024.
The board identified the following six safety issues in the incident:
- Safe operating limits: The facility lacked effective alarms to warn personnel when tube metal temperatures exceeded safe limits, leading to unsafe troubleshooting practices, such as not shutting down the fired heater remotely.
- Worker proximity to fired heater: The field operator was exposed to danger when he was sent to the fired heater despite their being safer options, such as remote shutdown.
- Low flow through fired heater: The safety system failed to detect low-flow conditions due to diverted process material, which Marathon hadn’t identified in its hazard analysis.
- Burner operation: A blocked air supply to burners led to improper air-fuel mixing, causing afterburning that contributed to the overheating and tube rupture.
- Valve misalignment: A misaligned valve caused process material to bypass the heater, contributing to the overheating and tube rupture.
- Corporate oversight: Marathon didn’t ensure the facility met the company’s standards before restarting operations as a renewable diesel facility, resulting in safety deficiencies.
“This tragic event underscores the importance of having proper safeguards in place for fired heater operation, which can be particularly hazardous,” CSB Chairperson Steve Owens said in a statement.
“A series of safety failures contributed to the severity of this incident, including the lack of appropriate guidance for when to shut down the heater remotely instead of putting a worker at risk of harm.”
The CSB is an independent federal government board that investigates industrial chemical incidents and makes safety recommendations to companies, industry groups, labor unions, and regulatory agencies, including the Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA). However, it doesn’t issue citations for regulatory violations or impose any fines. The president appoints board members, who are subject to Senate confirmation.
On March 12, the CSB released a second volume of incident reports covering 25 serious chemical incidents in 14 states: Arkansas, Alabama, California, Colorado, Connecticut, Illinois, Louisiana, Mississippi, Nebraska, Nevada, New Mexico, Ohio, Oklahoma, and Texas. The 25 incidents resulted in 7 fatalities, 23 serious injuries, and approximately $1 billion in property damage, according to the CSB.
The board released the first volume of incident reports on January 14.
“This second volume of reports is another step that the CSB is taking to keep the American people informed about the serious chemical incidents that occur nearly every day across this country,” Owens said. “Since the CSB’s reporting rule went into effect five years ago, the CSB has received reports of nearly 500 serious chemical incidents in 43 states.”