(Pascagoula, Mississippi, October 15, 2003) Investigators from the U.S. Chemical Safety Board (CSB) have concluded that the October 2002 plant explosion here occurred because First Chemical Corporation had not effectively evaluated the hazards of a chemical process that ran out of control. The blast blew the top off a distillation tower that was approximately 145 feet tall and propelled tons of fiery debris in the air, raining down onto adjacent industrial facilities and narrowly missing nearby hazardous chemical tanks.
The investigators report, which will be presented and voted on at a public meeting of the five-member Board today, said that plant operators were unaware that a dangerous chemical reaction was taking place inside the tower.
The process involved mononitrotoluene or MNT, a chemical related to TNT that can be explosive when exposed to high temperatures. Operators thought the process had been shut down weeks earlier, with all sources of heat removed. Unrecognized by plant personnel, the valves used to shut off steam to the tower had deteriorated. Steam was leaking through the shut-off valves, heating the 1,200 gallons of MNT in the column to a critical temperature of over 450°F, initiating a violent reaction as the material decomposed.
The tower exploded at 5:25 a.m. on Sunday, October 13, 2002. Three plant employees were injured when glass windows shattered into the control room where they were working. The CSB report said the room was located too close to the MNT tower and was not reinforced to withstand blast pressure. A projectile from the explosion pierced an MNT storage tank some distance away, igniting a fire that burned for almost three hours. Other debris landed a few feet from a large cylinder of anhydrous ammonia without doing serious damage. Area residents were directed to seek shelter in their homes, though the CSB learned at a public meeting later that this direction was not effectively communicated to them. Additionally, residents were not aware of the appropriate action to take while they sought shelter.
Board member Dr. Gerald Poje, chair of today's meeting, said, "We are very fortunate that shrapnel from the tower did not cause a greater chemical release or a more damaging fire. This accident underscores once again the vital importance of properly managing dangerous reactive chemicals and the processes that use them. When the Board voted last September to recommend that EPA and OSHA strengthen their regulations to reduce such dangers, we hardly imagined such a dramatic demonstration of the need would occur just three weeks later."
In a report presented in September 2002 the CSB noted significant gaps in regulatory coverage of reactive chemicals. The CSB Board called on the U.S. Occupational Safety and Health Administration (OSHA) and the U.S. Environmental Protection Agency (EPA) to expand the regulatory coverage of reactive chemicals and mixtures under their process safety rules. Those rules specify various safety measures for chemical processes such as performing hazard analyses, safety audits, and preventive maintenance. However, at present only a limited number of chemicals trigger such coverage. OSHA and EPA have yet to act on the Board's 2002 rulemaking recommendation, and existing regulations do not cover MNT.
Stephen J. Wallace, CSB lead investigator, said, "The plant did not have adequate systems for evaluating the hazards of processing MNT. He added that "First Chemical had learned of the instability of MNT during a safety analysis of a similar unit in 1996 but had not applied those safety lessons to the process that exploded a root cause of the blast." Mr. Wallace also noted that the facility did not have an effective program for maintaining critical process equipment like the steam shut-off valves.
The report further found that the plant did not have adequate systems to warn operations personnel of unexpected temperature increases, one sign of a runaway chemical reaction. Nor were there systems to automatically bring the process back to a safe state. Column C 501 the tower used to distill MNT had no temperature alarms, no automatic shutoff of the heating source, and no adequate system to relieve pressure build-up and mitigate the effects of an explosion.
The report proposes several recommendations be directed to the Pascagoula facility and the DuPont Corporation, which purchased First Chemical after the accident: that the facility improve its hazard analyses, conduct process safety audits, and install appropriate warning devices, and that DuPont Corporation track the facility's progress. In addition, the report recommends Jackson County improve its community notification system for such emergencies.
The CSB also recommended that the American Chemistry Council (ACC) and the Synthetic Organic Chemical Manufacturers Association (SOCMA) improve their industry management code, known as Responsible Care, under which member companies agree to comply with various safety policies.
The report found that First Chemical Corporation, a SOCMA member at the time of the accident, had earlier asserted to SOCMA that it was following those agreed-upon safety policies including performing hazard analyses even though no evaluation had been done for the MNT unit.
The CSB is an independent federal agency charged with investigating industrial chemical accidents. CSB investigations look into all aspects of such events, including physical causes like equipment failure, as well as inadequacies in safety management systems. Typically, the investigations involve extensive witness interviews, examination of physical evidence, and chemical and forensic testing.
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. Further information about the CSB is available from www.csb.gov.
For more information, contact Daniel Horowitz, 202-261-7613 / 202-441-6074 (cell) or Sandy Gilmour Communications, 202-261-7614 / 202-251-5496 (cell).