Report finds series of errors caused deadly DuPont plant accident in La Porte

String of errors and missed warnings contributed to deaths of La Porte plant employees

HOUSTON – Board members of the U.S. Chemical Safety Board voted unanimously to approve safety recommendations identified by investigators after the deadly November 2014 incident at the DuPont plant in La Porte.

Families of the victims told Channel 2 they hoped DuPont would adopt the recommendations as quickly as possible.

"What happened to my brothers shouldn't have have happened. I don't want anyone to lose their dad, brother or grandpa over careless neglect. That's what i call it. It shouldn't have happened," said Lanette Soto, Robert and Gibby Tisnado's sister.

The U.S. Chemical Safety Board has released findings of an interim investigation into the leak of a toxic chemical at the DuPont manufacturing facility in La Porte. Four employees were killed in the incident on Nov. 15, 2014. 

The board's investigation found a series of mistakes that began five days earlier, eventually lead to the release of nearly 24,000 pounds of methyl mercaptan, a toxic chemical. Crystal Wise, Wade Baker, Robert Tisnado and his brother Gilbert Tisnado all died of asphyxia and exposure while dealing with the leak.

"Our investigation has uncovered lapses, weaknesses or failures in the company's safety planning and procedures -- safety management systems that could have and should have prevented the accident and this loss of life," Vanessa Allen Sutherland, the safety board's chairperson, said. "We believe these recommendations lay out what DuPont should do to protect its workers and the public.  We hope these improvements at La Porte will serve as a first step to fully restore DuPont's global reputation for safety."

SERIES OF EVENTS

The CSB investigation found a chain of events, beginning on Nov. 10, 2014 triggered the toxic leak that happened the following Saturday morning.  On Monday, Nov. 10, a water dilution system was accidentally activated and that caused a storage tank to overload. Crews were forced to shut down the system used to manufacture an insecticide produced at the plant. They tried to restart the system two days later, but discovered a clog. 

As they tried to clear that clog, the investigation revealed, about 2,000 pounds of water accidentally ended up in a storage tank containing methyl mercaptan.

The report states that normally, a mixture of methyl mercaptan and water would not create a problem. However, temperatures were unusually cold that day (around 40 degrees) and had been consistently below 55 degrees in the days preceding. 

The low temperature caused the mixture to form a separate blockage in the system's methyl mercaptan feed.  Crews came up with a plan to clear the clog and get the chemical flowing again.

On Friday morning, a new group of workers began their shift. The CSB report states these workers didn't know about the earlier system shutdown and the clogs that remained. The new team met and took over the plan to clear the clogs. The plan was to use hot water on the outside piping to dissolve the clog. The investigation shows the crew realized methyl mercaptan would expand when heated and they needed to figure out how to remove dangerous vapors from the building. So valves were opened along the feed line and a system was set up to vent the methyl mercaptan. The report states this plan was never evaluated for potential hazards and no safety analysis was performed. There was also no written procedure created to track the progress of the plan.

THE FATAL LEAK

Around 1:30 a.m. on Nov. 15, the CSB investigation states, the team working to clear the clog in the methyl mercaptan feed line realized the plan was not working. They regrouped in the control room to figure out how to go forward. But they left two valves open that were part of their plan to clear the clog and remove the vapors. An hour later, at around 2:45 a.m., the report states, the flow of methyl mercaptan in the feed line suddenly resumed, but no one noticed.