CSB: ConAgra Explosion Likely Caused by Natural Gas

June 18, 2009
Based upon its ongoing investigation of the fatal June 9 ConAgra Foods explosion, the U.S. Chemical Safety Board (CSB) said the blast likely was caused by natural gas that may have been purged into the building during a water heater installation.

The blast occurred in the pump room in the south side of the Garner, N.C.-based ConAgra plant, killing three and injuring dozens of workers. CSB Chairman John Bresland toured the outside of the plant June 17 with the rest of the CSB investigation team.

“I was very much struck by the scale of the explosion,” he said. “As others have noted, it’s easy to imagine how even more people could be impacted by an accident of this magnitude. Around 100,000 square feet of the facility were damaged in this explosion.”

A Risky Operation

Donald Holmstrom, CSB investigations supervisor, explained that ConAgra was in the process of installing and commissioning a new, industrial-scale, gas-fired water heater in the pump room. A new gas line, measuring several inches in diameter, was installed between the gas main on the roof and the pump room to supply gas to the heater, Holmstrom explained. This installation was completed a week before the accident. ConAgra hired various contractors to perform aspects of this work.

On the morning of June 9, Holmstrom said one of the contract firms was working with ConAgra personnel to put the new gas line and heater into service. As part of this activity, the line was purged to remove air.

“The CSB is examining the possibility that gases inside the line were likely purged and vented directly into the pump room in the interior of the building, leading to a flammable gas cloud and an explosion,” Holmstrom said. He also confirmed that some witnesses did reveal that they smelled gas within the facility prior to the explosion.

When asked if purging a gas line into a building was a standard procedure, Bresland said, “In my mind, that would seem to be a risky operation. I have never heard of such a thing taking place. It would seem more appropriate, if you are going to purge a gas line that contains natural gas, that you would purge it outside the building.”

Ammonia, which was stored in quantities in the facility, was released during and following the incident. CSB learned that the refrigeration system was discharged into local surface waters following the explosion, and harmful levels of ammonia were later detected in a nearby creek.

Holmstrom and Bresland both stressed that the ignition source for the explosion has not been determined and may be difficult to identify.

Preserving the Evidence

Holmstrom said the investigation will focus on determining why flammable gas was released in the midst of an occupied building with about 100 people in the vicinity, and if this type of procedure was routine at ConAgra. In addition, CSB will exam the appropriateness of locating a heater in the center of a building that is susceptible to explosion damage.

At this time, Bresland explained, the pump room and certain interior parts of the facility still are too dangerous to enter, and CSB is unsure when it will be safe to do so. “We want to be sure evidence is preserved so the damage hasn’t been destroyed or moved in such a way to affect the investigation,” he said.

The CSB investigation team will continue to interview witnesses, review documents and examine relevant standards governing these activities, including fire codes, insurance guidance and others industry standards, Holmstrom said. CSB also will examine ConAgra’s practice of selection and safe management of contractors.

The ConAgra plant may reopen the north side of the building for manufacturing operations if it is considered safe after cleanup. CSB construction engineers are examining this area to determine if it is safe.

Bresland stressed that CSB is conducting a “thorough, rigorous investigation” that will last for months.

“The public and work force of ConAgra are entitled to a clear explanation of exactly why this tragedy occurred,” he said.

Related Article

Three Workers Dead, Dozens Injured After Blast at N.C. ConAgra Foods Facility

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