Springfield, Illinois, March 6, 2007 - The U.S. Chemical Safety Board (CSB) today issued its final report on the explosion and fire that destroyed the Formosa Plastics plant in Illiopolis, Illinois, on April 23, 2004, concluding that the accident occurred when an operator overrode a critical valve safety interlock on a pressurized vessel making polyvinyl chloride. Vinyl chloride liquid and vapor discharged into the plant and was ignited, resulting in a massive explosion.
The CSB found that both Formosa and Borden Chemical, the company from whom Formosa purchased the plant in 2002, were aware of the possibility of serious consequences of an inadvertent release of chemicals from an operating PVC reactor. But the investigation determined that the measures both companies took were insufficient to prevent human error or minimize its consequences.
The accident resulted in the deaths of five workers and serious injuries to three others. About 150 persons in the small community of Illiopolis were evacuated to avoid contact with toxic fumes and smoke. The facility was heavily damaged and has been permanently closed.
In addition to the final report, the CSB released a safety video which detailed key findings and recommendations and contained a computerized animation of the likely scenario of events leading to the explosion.
CSB Chairman Carolyn W. Merritt said, "People do make mistakes. And that is why it is all the more important for chemical plants to design systems that take into account the possibility of such errors." Ms. Merritt continued, "This accident occurred because the companies involved did not look closely enough at the potential for catastrophic consequences resulting from human error."
On the day of the accident, an operator on the upper level of the reactor building was washing out a reactor with a water blaster. He then should have gone to the lower level to open two valves on the reactor he was cleaning - a reactor bottom valve and the lower drain valve. From survivors' testimony and physical evidence, the CSB concluded that under the most likely scenario, the worker made an error after descending the stairwell to the lower level. He turned to a different cluster of reactors and went to a vessel he evidently thought was the one he had started cleaning. It was the wrong reactor.
He opened the drain valve. But the reactor bottom valve would not open. To prevent an accidental release, that valve was fitted with a safety interlock which prevented it from opening when the reactor was pressurized. However, instead of seeking further information on why the bottom valve wouldn't open, he attached an air hose that provided the pressure needed for the override - a procedure intended to be used only in an emergency.
When the valve opened, the highly flammable vinyl chloride immediately sprayed onto the floor and vapor filled the area. Vinyl chloride detection alarms sounded in the area. The supervisor and operators attempted to slow the release by relieving the reactor pressure. Just as the supervisor made an attempt to get to the bottom level via an external stairwell, the vinyl chloride vapor exploded.
The CSB concluded that two of the workers who were killed had been working near the top of the reactor, and two others who were killed had been at the bottom level. A fifth operator died two weeks later. The supervisor and two other workers were seriously injured.
The investigation found that operators had time to evacuate the production building after the release began and alarms had sounded. However, operators remained in the area in a vain attempt to mitigate the release.
CSB Lead Investigator Lisa Long said, "The CSB investigation found that systems and procedures put in place by both Borden Chemical and Formosa were insufficient to minimize the potential for human error. In addition, Formosa did not adequately train and drill its employees to immediately evacuate in case of a major release of hazardous chemicals. Such an evacuation would have saved lives."
The CSB report said additional safeguards - such as locks or other devices to secure the interlock system - could have prevented critical valves from being opened when the reactor was pressurized. Investigators also noted the reactors were grouped into similar sets of four, increasing the possibility of human error. Yet there were no gauges, indicators or warning lights to inform operators on the lower level of a reactor's operating status. Operators on the lower level, where the valves were, did not carry radios or have intercoms to communicate with the upper level panel operators.
The CSB found that both Borden Chemical and Formosa were aware of the potential for the severe consequences of opening the bottom valve on a reactor under pressure. A 1992 Borden hazard analysis recommended safeguards which were never adopted. Later, in 1999, another Borden analysis again identified the same potential consequences - a massive release of vinyl chloride - but determined that the existing safety interlock was sufficient to prevent a serious accident.
In 2003, an operator at the Formosa plant in Baton Rouge, Louisiana, opened the bottom valve on the wrong reactor, releasing 8,000 pounds of vinyl chloride into the atmosphere. Some safety improvements were made in Baton Rouge but the company determined changes were not needed in Illiopolis because the valve controls were different.
In February 2004, an operator at the Illiopolis plant bypassed a bottom valve safety interlock, releasing a significant amount of vinyl chloride. After that incident, the company determined that additional controls were needed on the interlock. However, the company did not act quickly enough. The fatal explosion occurred just two months later.
The Board issued recommendations to Formosa Plastics Corporation USA, the Vinyl Institute, the National Fire Protection Association, the Environmental Protection Agency, and the Center for Chemical Process Safety, an organization of the American Institute of Chemical Engineers.
The Board recommended that Formosa review the design and operation of all their U.S. PVC facilities. The CSB urged Formosa to ensure chemical processes are designed to minimize the consequences of human error, improve control of safety interlocks, more thoroughly investigate high-risk hazards, and consider all consequences in near-miss investigations. Formosa was also urged to improve emergency planning and conduct periodic drills, emphasizing prompt evacuations.
The CSB safety video is available on CSB.gov by clicking on "Video Room." It is available in streaming video or for downloading using Windows Media Player. DVD copies of the video may be ordered from the Video Room free of charge.
The CSB is an independent federal agency charged with investigating industrial chemical accidents. The agency's board members are appointed by the president and confirmed by the Senate. CSB investigations look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards, and safety management systems.
The Board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. Visit our website, www.csb.gov.
For more information, contact: Sandy Gilmour 202-261-7614, cell 202-251-5496; Public Affairs Specialist Kate Baumann 202-261-7612, cell 202-725-2204; Director of Public Affairs Dr. Daniel Horowitz, 202-261-7613, cell 202-441-6074.