A truck with 4,000 gallons of sulfuric acid pulled up about 7:35 a.m. and began to unload into a tank at the MGP Ingredients plant in Atchison, Kan.
Unfortunately, it was not the sulfuric acid tank but one that was 90 percent full of sodium hypochlorite, or bleach, which is an incompatible chemical. Soon, the lid of the tank blew off — causing a dense green cloud to rise from the plant and drift nearly 6 miles over the town of 11,000 people.
“The two materials combined to produce chlorine gas that sent over 140 individuals, both workers and members of the public, to area hospitals and resulted in shelter-in-place and evacuation orders for thousands of local residents,” according to a preliminary report released Wednesday by the U.S. Chemical Safety Board.
No one died in the Oct. 21 accident, but the cloud caused widespread respiratory distress. At least two people, including an MGP employee, were hospitalized.
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The safety board called the accident preventable.
The intake line for the sodium hypochlorite tank was only 18 inches away from the intake line for the sulfuric acid tank, and they looked alike, the safety board said. The labeling was poor.
Further, “emergency shutdown mechanisms were not in place,” the report said.
It took until 10:50 a.m. for the chlorine gas to dissipate sufficiently for authorities to call the all clear.
MGP Ingredients makes alcoholic beverages and food additives and has operated in Atchison since 1941.
The Chemical Safety Board found “a number of design deficiencies that increased the likelihood of an incorrect connection.”
It also found that neither MGP Ingredients nor Harcros Chemicals, which delivered the sulfuric acid, followed proper procedures.
The investigators made several recommendations, including better labeling and a shut-off mechanism that can be remotely activated.
At a news conference Wednesday, a Chemical Safety Board investigator said MGP Ingredients had modified its labeling and other procedures since the accident and was considering valve shut-off improvements.
The company issued a statement Wednesday saying it is “making every effort to enhance our operations so this type of situation does not happen again. As part of this effort, we have hired Burns & McDonnell to provide a comprehensive review of our loading, unloading and chemical storage methods to strengthen the safety of our systems.”
The company also said it had paid the medical bills of 134 people affected by the chlorine gas release.
The Chemical Safety Board is not a regulatory agency and does not have authority to impose fines. But the chairwoman of the board, Vanessa Allen Sutherland, said the Occupational Safety and Health Administration and the Environmental Protection Agency, both of which are regulatory, are also investigating the incident.