CSB Issues Latest Reports Highlighting Safety Issues

The U.S. Chemical Safety and Hazard Investigation Board (CSB) has released new reports summarizing chemical incidents and provided updates on key investigations, including the Pemex Deer Park hydrogen sulfide release and the Marathon Martinez refinery fire. Below are the latest updates from the CSB. 

Investigation Update on Fatal Pemex Release

CSB shared March 17 a second update on its ongoing investigation into the fatal hydrogen sulfide release Oct. 10 at the Pemex Deer Park Refinery in Deer Park, Texas. Two contract workers died during the incident, which resulted in the release of over 27,000 pounds of toxic hydrogen sulfide gas. Local authorities issued shelter-in-place orders lasting several hours for the neighboring cities of Deer Park and Pasadena.

The Pemex Deer Park Refinery is an indirect subsidiary of Pemex, a petroleum company wholly owned by Mexico's federal government. The site employs approximately 1,000 personnel and 1,200 contractors. The refinery’s byproduct, hydrogen sulfide, can cause serious health hazards if released into the environment.

On the day of the incident, maintenance contractors were working to remove piping isolation devices from one of the refinery's amine regeneration units. During the task, workers inadvertently opened a flange on a piping segment of another unit, which was still pressurized, releasing a toxic concentration of hydrogen sulfide gas into the air. The release fatally poisoned one contract worker at the scene and another downwind of the release.

CSB said its ongoing investigation will focus on safe work factors, maintenance policies and procedures and emergency preparedness. The final report will include comprehensive findings, analyses and, if applicable, recommendations for improved safety practices to prevent future incidents.

2023 Marathon Renewables Fire Final Report

CSB released its final investigation report March 15 into the Nov. 19, 2023, fire at the Marathon Martinez Renewables facility in Martinez, California. The incident caused one employee to suffer third-degree burns over most of his face and body and resulted in approximately $350 million in facility damages. 
 
During the startup of a renewable diesel hydroprocessing unit at the plant, a metal tube in a fired heater ruptured and released renewable diesel and hydrogen, sparking the fire. After the incident, the company shut down the process unit for nearly a year before restarting operations in November 2024.

CSB’s final report outlined six critical safety issues and offered recommendations to prevent similar incidents in the future. The investigation found that the rupture occurred due to a combination of factors, including a misaligned valve left open, which caused the process flow to bypass the heater, and combustion issues resulting from blocked air supply to burners. The combination of these conditions led to dangerously high temperatures in the fired heater, ultimately causing the tube to overheat and rupture.

Read more about the incident, the investigation and safety recommendations here. 

Volume 2 of Chemical Incident Reports Released

After launching Volume 1 reports in early January, CSB announced March 12 the release of Volume 2 of its Incident Reports as part of an initiative to compile summaries of reported incidents and make them regularly available to the public. 

Volume 2 covers 25 serious chemical incidents in 14 states: Arkansas, Alabama, California, Colorado, Connecticut, Illinois, Louisiana, Mississippi, Nebraska, Nevada, New Mexico, Ohio, Oklahoma and Texas. These incidents resulted in 7 fatalities, 23 serious injuries, and approximately $1 billion in property damage.

The reports give the public important information about serious chemical incidents that have been reported to CSB under the agency’s Accidental Release Reporting Rule (ARRR). The 25 incidents covered in Volume 2 occurred between May 2020 and August 2024. 

Since July 2022, the agency has been posting overall data on its website about the incidents reported under the ARRR, including the name and location of the chemical facility involved in the incident, the date of the incident, and whether the incident involved a fatality, serious injury or substantial property damage.

Like Volume 1, each incident report includes a summary of the event and its probable cause — information that has not previously been released to the public.