LA PORTE, Texas – In November 2014, four workers were killed by toxic vapor at DuPont's La Porte facility.
In the middle of the night, nearly 24,000 pounds of deadly methyl mercaptan "escaped through two valves in a poorly ventilated manufacturing building," according to the U.S. Chemical Safety Board's final report, which was released Tuesday.
“Our investigation revealed a long chain of failures which resulted in this fatal event, including deferring much-needed process improvements; improvements that could have prevented the toxic release," interim executive Dr. Kristen Kulinowski said.
According to the report, for several days leading to the incident, workers attempted to clear blocked piping outside of the manufacturing building. The report says two workers went to drain liquid from piping inside the building in response to what they thought was a "routine, unrelated pressure problem."
The report says the pressure problem was actually related to the clearing activities.
"Liquid methyl mercaptan drained from the piping, filling the manufacturing building with toxic vapor," the report says.
One of the workers made a distress call, but both were unable to escape the building and died.
Four additional operators responded to the distress call and entered the manufacturing building. Two died from the vapor, and the other two survived.
'Flawed engineering design'
“The CSB’s investigation determined that the cause of the toxic chemical release was a flawed engineering design and the lack of adequate safeguards. Contributing to the severity of the incident were numerous safety management shortcomings including deficiencies in formal process safety culture assessments, auditing and corrective actions, and troubleshooting operations,” lead investigator Tamara Qureshi said.
The investigation revealed the facility had "long-standing issues with vent piping."
DuPont La Porte did not "address liquid accumulation in waste gas vent header vapor piping," the report says.
The report said that in order to deal with the problems, daily instructions were given to operations personnel to drain liquid from the pipes to the atmosphere inside the manufacturing building where the incident happened.
The instructions did not specifically address the potential safety hazards the actions could pose to the workers, according to the report.
What happened to the facility?
In spring 2016, DuPont officials announced the facility would not reopen.
Officials with the company determined "significant changes in market conditions during the period of the shutdown would persist over the long term" and that the cost required for the restart was "not a long-term viable and cost-efficient option for the DuPont Crop Protection business."
In 2017, DuPont dismantled and removed the buildings and equipment that had been associated with the unit.
Safety lessons learned from the incident
The CSB's investigation identified weaknesses in the DuPont La Porte safety management system.
The report says several safety lessons for the chemical industry can be learned from the incident.
Here are the lessons the report cites: