BY STEPHEN L. HERMANN
Interstate 40 was closed for more than 16 hours last year by a burning trailer loaded with 55-gallon drums of the toxic flammable liquid acetonitrile. A colorless liquid with an aromatic odor, acetonitrile forms cyanide in the body if ingested or inhaled. It has a permissible exposure level (PEL) of 40 parts per million (ppm) and an immediately dangerous to life and health (IDLH) level of 500 ppm.
The incident occurred several miles west of the small northern Arizona town of Two Guns, in a county area that has no fire departments. Firefighters from the nearby volunteer Doney Park Fire District responded, along with a hazardous materials captain from the Flagstaff Fire Department.
Around 5 p.m., the driver of the truck with a mixed load of freight noticed in his rearview mirror that smoke was streaming from the trailer. He was unable to put out the flames with his fire extinguisher. The highway patrolman who arrived at the scene blocked the highway in both directions, in anticipation of a potential explosion.
The Arizona Department of Public Safety (DPS) Highway Patrol hazardous materials specialists were dispatched from Phoenix, several hours away, as was a hazardous materials technician from the Arizona Department of Environmental Quality (DEQ). Under the state of Arizona hazardous materials emergency response plan, DPS provides state on-scene coordinators during the “fires and explosions” phase of an incident. When the incident has stabilized, DEQ becomes the coordinating agency if there are environmental consequences.
 (1) An Arizona Department of Public Safety helicopter made a reconnaissance of the scene to determine if any fires were still burning and personnel could enter safely. (Photos by author.) |
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 (2) Entry could not be made until the fire was out because of the burning and exploding 55-gallon drums of the toxic flammable acetonitrile in the trailer. |
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THE MITIGATION
Responding firefighters realized that the burning trailer was too dangerous to approach. They observed from half a mile away that the drums were exploding and rocketing into the air. For more than an hour, drums were landing as far as 150 feet from the trailer, in some instances trailing burning flammable liquid and spreading the fire to the grass on the freeway median and in bar ditches. Because of the potential danger from the exploding drums, it was decided not to enter the scene until the fire was out. The trucking company had contacted a cleanup contractor, who dispatched crews to the scene.
The fire burned throughout the night; the flames finally appeared to subside just before sunrise. Unsure of the fire’s exact status, the hazardous materials team had requested that a DPS helicopter conduct an aerial reconnaissance of the scene.
The helicopter carefully circled the area. It was determined that the fire was out. The cleanup contractor made an initial entry into the scene to determine the extent of potential contamination from the toxic liquid.
 (3) The exploding drums had rocketed across the freeway; detection instruments sensitive to 1 ppm found no residual chemical contamination. |
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 (4) The fire burned for about 12 hours. After that time, four drums still contained a small amount of the acetonitrile. |
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The entry team, using a photoionization instrument and a combustible gas indicator, determined that chemical residue was detectible only at the rupture point of four drums. Since the scene was now stable, the DEQ hazardous materials technician assumed the duties of state on-scene coordinator.
Once it was established that the eastbound lanes of I-40 were not contaminated, a highway department street sweeper was brought in to remove the drum residue from the opposite side of the freeway. After the debris was removed, the freeway was reopened, using the eastbound lanes for two-way traffic in the immediate area.
The cleanup contractor brought in two roll-off containers to hold the debris from the fire and began to clear the scene. The four drums, which still contained residue, were placed to one side; the balance of the empty drums and fire-damaged freight were loaded into the roll-offs.
Another commercial truck loaded with about 40,000 pounds of frozen chickens had been abandoned by its driver during the initial emergency. Its refrigeration unit was still functioning. An insurance adjuster representing the trucking company arrived on the scene and wanted to know if the vehicle was safe. The photoionization detection instrument was used to survey the vehicle. No contamination was detected, and the vehicle was released.
The cleanup contractor finished removing the fire debris from the highway. The small amount of acetonitrile residue was poured into a smaller container, which was disposed of as hazardous waste.
LESSONS LEARNED
- If there are no life safety exposures, it may not be necessary to enter a potentially hazardous scene to make an assessment until the incident is stabilized.
- Even though containers of flammable liquids may be involved in a heavy fire for more than 16 hours, some flammable liquid residue may remain in some of the containers.
- Expensive and not always available sensitive detection instruments may be needed to determine if a scene has been contaminated with a toxic chemical.
- A helicopter may be able to conduct a safe reconnaissance of an unstable hazardous materials incident scene.
STEPHEN L. HERMANN is hazardous materials coordinator and specialist for the Arizona Department of Public Safety and Arizona’s senior state on-scene coordinator for hazardous materials emergency response. He is past national chairman of COHMED, the national organization of state and local hazardous materials enforcement officers, and past chairman of the Commercial Vehicle Safety Alliance Hazardous Materials Committee. He has a bachelor of science degree in explosives technology and is a graduate of the U.S. Naval School Explosive Ordnance Disposal, United States Army Command and General Staff College, U.S. Army War College, and state Division of Emergency Services Hazardous Materials Technician course.
