The U.S. Chemical Safety Board (CSB) has released its final report on the August 28, 2008, Bayer CropScience pesticide manufacturing unit explosion that killed two workers and injured eight others. In a report scheduled for Board consideration at a public meeting this evening in Institute, the CSB found multiple deficiencies during a lengthy startup process that resulted in a runaway chemical reaction inside a residue treater pressure vessel. The vessel ultimately over pressurized and exploded. The vessel careened into the methomyl pesticide manufacturing unit leaving a huge fireball in its wake.
The report found that had the trajectory of the exploding vessel taken it in a different direction, pieces of it could have impinged upon and possibly caused a release from piping at the top of a tank of highly toxic methyl isocyanate (MIC).
The accident occurred during the startup of the methomyl unit, following a lengthy period of maintenance. The CSB found the startup was begun prematurely, a result of pressures to resume production of the pesticides methomyl and Larvin, and took place before valve lineups, equipment checkouts, a pre-startup safety review, and computer calibration were complete. CSB investigators also found the company failed to perform a thorough Process Hazard Analysis, or PHA, as required by regulation.
This resulted in numerous critical omissions, including an overly complex Standard Operating Procedure (SOP) that was not reviewed and approved, incomplete operator training on a new computer control system, and inadequate control of process safeguards. A principal cause of the accident, the report states, was the intentional overriding of an interlock system that was designed to prevent adding methomyl process residue into the residue treater vessel before filling the vessel with clean solvent and heating it to the minimum safe operating temperature.
Furthermore, the investigation found that critical operating equipment and instruments were not installed before the restart, and were discovered to be missing after the startup began. Bayer’s Methomyl-Larvin unit MIC gas monitoring system was not in service as the startup ensued, yet Bayer emergency personnel presumed it was functioning and claimed no MIC was released during the incident.
CSB Chairperson Dr. Rafael Moure-Eraso said, “The deaths of the workers as a result of this accident were all the more tragic because it could have been prevented had Bayer CropScience provided adequate training, and required a comprehensive pre-startup equipment checkout and strict conformance with appropriate startup procedures. This would have revealed multiple dangerous conditions and procedures that were occurring at a time when the company wanted to restart production of a key pesticide product. Startups are always a potentially hazardous operation, but to begin with computer control systems that have not been checked, while bypassing safety interlocks, is unacceptable.”
The investigation report makes recommendations to the company and its Institute plant, to the Occupational Safety and Health Administration (OSHA), the Environmental Protection Agency (EPA), and several West Virginia agencies. Citing a highly successful county program to ensure refinery and chemical plant safety in Contra Costa County, California, the CSB report recommends the West Virginia Department of Health and Human Resources establish a “Hazardous Chemical Release Prevention Program” that would have the authority to inspect and regulate such plants, and make public its ongoing findings.
Dr. Moure-Eraso said, “I believe a state and county-run program like this would go a long way to making chemical operations safer in places like the Kanawha Valley. OSHA and EPA, have limited resources and cannot be everywhere at once. However, local jurisdictions can put together highly effective and targeted inspection and enforcement programs, funded by levies on the plants themselves. The accident rate in Contra Costa County has dropped dramatically, and last year in fact they had no significant accidents, thanks, in my view, to this program.”
CSB Investigations Manager John Vorderbrueggen noted that a major contributing factor to the accident was a series of equipment malfunctions that continually distracted operators. “Human factors played a big part in this accident, and the absence of enforced, workable standard operating procedures and adequate safety systems meant that mistakes could prove fatal. For example, operators were troubleshooting several equipment problems and during the startup, inadvertently failed to prefill the residue treater vessel with solvent. A safety interlock was designed to stop workers from introducing highly-reactive methomyl, but it was bypassed as had been done in previous operations with managers’ knowledge. Once the chemical reaction of the highly concentrated methomyl started, it could not be stopped, and the temperature and pressure inside rose rapidly, finally causing an explosion.”
Board Member John Bresland, who was CSB chairman at the time of the Bayer accident, noted the confusion that resulted in the community’s emergency response following the explosion at 10:33 p.m. “The Bayer fire brigade was at the scene in minutes, but Bayer management withheld information from the county emergency response agencies that were desperate for information about what happened, what chemicals were possibly involved,” Mr. Bresland said. “The Bayer incident commander, inside the plant, recommended a shelter in place; but this was never communicated to 911 operators. After an hour of being refused critical information, local authorities ordered a shelter-in-place, as a precaution.”
“Proper communication between companies and emergency responders during an accident is critical,” said Mr. Bresland, adding, “The community deserved better, especially considering the amounts of hazardous chemicals, in use and being stored at various chemical facilities in the Kanawha River valley.
The CSB report notes that two workers and four volunteer firefighters required examination for possible exposure to toxic chemicals.
The investigation examined the potential consequences of a hypothetical trajectory of the careening residue treater vessel that would result in its hitting the heavy steel mesh ballistic shield surrounding the above-ground MIC tank. The analysis – using blast pressure and impact energy calculations – concluded that the shield would have protected the MIC tank from a residue treater vessel hit. However, the CSB found, had the residue treater struck the shield structure near the top of the frame, the displaced frame could have contacted an MIC pipe, which might have resulted in an MIC release into the atmosphere.
Chairperson Moure-Eraso said, “Any significant MIC release into the atmosphere along the Kanawha valley could have proven deadly, and that concern has been legitimately expressed for decades in the community. This potential was reduced when Bayer announced last year it would no longer store MIC above ground; it will be reduced to zero in approximately 18 months when the company has announced it will end MIC production and use at the Institute facility – the only place in the country still storing large quantities of MIC.”
Dr. Moure-Eraso continued, “Bayer’s decision to end pesticide production using MIC was, I understand, done for its own business reasons. But for whatever reasons, the eventual elimination of this chemical will enhance safety in the Kanawha Valley, for workers and residents alike, and is a positive development in my view.”
The CSB public meeting is scheduled for 6:30 p.m. this evening at the West Virginia State University, Sullivan Hall, Wilson University Union, Multipurpose Room 143, in Institute. The Board will hear a full report on the investigation, and then will invite seven panelists including industry experts, community activists, and county government representatives to testify. Following a public comment period, the Board will vote on the report conclusions and recommendations.
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.