Workers on the night shift at the E.I. du Pont de Nemours insecticide plant in La Porte acted as they were instructed when high-pressure alarms flashed on their computer screen: They drained valves inside an insecticide production building without breathing protection. They thought they were dealing with a routine problem in a waste-gas pipeline, when highly toxic methyl mercaptan vapor filled the room.
Nearly 24,000 pounds of methyl mercaptan escaped on Nov. 15, 2014. One worker, who went in with emergency air bottles, saved a co-worker's life, but died beside his brother near the leaking valves. By the end of the night, four workers were fatally exposed to methyl mercaptan.
Tonight, I and my fellow members of the U.S. Chemical Safety Board (CSB) will vote on interim recommendations from the CSB's investigation of the tragedy. Our investigative team spent the past 10 months examining what went wrong and what must be done so that accidents like this one do not occur.
Our team uncovered flawed safety procedures, equipment design and inadequate planning that left operators and the public at risk. Two rooftop ventilation fans hadn't worked for weeks, despite an "urgent" repair order. Because the toxic release was so large, even working fans probably couldn't have kept air inside that four-story building safe to breathe.
DuPont must go back to process safety basics and perform robust process hazard analyses on every part of the insecticide operation, starting with the riskiest. The company, wherever feasible, should evaluate inherently safer design options at every step of the manufacturing process and conduct a comprehensive engineering analysis of the building and its air ventilation system. DuPont should consider chemical or thermal destruction of toxic leaks and discharges instead of directing them to the open air. And finally, the company must ensure the building is safe for workers before resuming production, and should allow workers through their local union to more fully participate in drawing up and carrying out the new safety actions.
This incident is the third time in five years that the CSB has investigated preventable fatal accidents at DuPont facilities. One worker was killed in 2010 when a hose carrying toxic phosgene liquid burst at a Belle, W.Va., plant, and a contract welder perished in an explosion at a Buffalo, N.Y., facility later that year.
After the 1984 release of methyl isocyanate at a Union Carbide insecticide plant that killed thousands in Bhopal, India, DuPont made proactive changes on how it handled methyl isocyanate at La Porte, moving production to an open building and installing equipment to destroy toxic chemical leaks. DuPont didn't broadly adopt those measures, for methyl mercaptan and chlorine, however, even though they are also toxic chemicals in the building used to make the insecticide.
Our investigators found that a 2011 change to boost insecticide production while reducing emissions actually created a problem: liquid accumulation and frequent high-pressure events in equipment connected to the waste-gas pipeline. Rather than fix this problem, it became normal for operators to simply drain the accumulated liquid.
By Vanessa Allen Sutherland: Published 4:53 pm, Tuesday, September 29, 2015