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Energy & Environment

Design Flaws Led To Poison Gas Leak At DuPont Plant in La Porte

The November 15 accident led to the deaths of four chemical plant workers.


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Four plant workers died from exposure to poisonous gas at the La Porte DuPont chemical plant, November 15, 2014. Image credit: U.S. Chemical Safety Board.

The U.S. Chemical Safety Board provided these photos from its investigation of the DuPont La Porte plant.

Federal regulators say design flaws with a network of pipes and valves at a Houston-area DuPont chemical plant contributed to a leak of poisonous gas in November. Four plant workers died from exposure to the gas.

The events leading to the deaths of the workers November 15 in La Porte began days before. A unit shutdown led to water leaking into a holding tank for methyl mercaptan, a chemical used in the manufacture of insecticides. The mixture resulted in a gel forming on pipes leading from the tank. Efforts to remove the gel, which was causing pressure to build, resulted in the opening of interconnected valves.

“It’s somewhat frequent, getting high pressure in the vent system,” says Dan Tillema, an investigator for the U.S. Chemical Safety Board. “Usually it’s from a water condensate, and they drain it on third floor inside the building. In this case, it was the toxic methyl mercaptan liquid in the vent system, but the response was the same. They didn’t have anything to tell them it was different than normal, and they drained the methyl mercaptan into the building where they were standing.”

The ventilation fans in the building were down at the time, leaving no way to expel the gas before it killed the four workers.

DuPont representatives declined to be interviewed for this story. The company released a statement, saying it is cooperating with federal regulators in the investigation.


Complete DuPont statement (emailed): 

“Yesterday, U.S. Chemical Safety Board (CSB) Chairman Moure-Eraso, Board Member Erlich and other CSB officials toured the DuPont La Porte methomyl process unit to get a first-hand review of the agency’s ongoing investigation. We appreciated the opportunity to engage in constructive discussions with the agency.

Safety has been a core value and constant priority at DuPont since our founding. We first implemented safety rules in 1811 and we have been engaged in a continuous process to improve ever since. We are responding to this tragedy in a way that reinforces our absolute focus on safety and enables us to learn from it so that we can find ways to be an even better company.

We have an expert team leading an intensive effort to understand exactly what happened — and how we can ensure that it never happens again.

We remain committed to working with the CSB and other governmental agencies who are also conducting their own investigations. Investigating incidents such as these takes time and the issues often are technically complex. The results from these reviews will guide actions we take going forward.

We are also committed to maintaining the integrity of the ongoing investigations. To that end, it is premature for us to comment or provide additional information outside of these processes.”

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Andrew Schneider

Andrew Schneider

Politics and Government Reporter

Andrew Schneider is the senior reporter for politics and government at Houston Public Media, NPR's affiliate station in Houston, Texas. In this capacity, he heads the station's coverage of national, state, and local elections. He also reports on major policy issues before the Texas Legislature and county and city governments...

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