BURNING GASOLINE TANKERS: THE BEST ACTION MAY BE NO ACTION
BY PETER M. STUEBE
Often in haz-mat situations, experience dictates that no action is the best course of action. This is true even for the best-trained departments that have adequate manpower and state-of-the-art equipment. Several major incidents in New York City have reinforced the concept of limited offensive operations and showed that this may be the best decision an incident commander can make.
In May 1994, Engine Company 288, located in Queens, New York, received a call to respond to a reported truck fire. Haz Mat 1, housed in the same quarters, does not normally respond to such incidents on the initial alarm unless preliminary information indicates that hazardous materials may be involved or specialized equipment may be needed. The location was the intersection of the Brooklyn-Queens Expressway and the Long Island Expressway, both heavily traveled major highways. Firefighters could see from the fire station a large column of thick, black smoke pushing into the sky from the fire. On seeing this, I, as the officer of Haz Mat 1, ordered the company to respond as well, as it appeared to be more than a routine truck fire.
THE SCENE
As the companies approached the scene, radio transmissions from first-due units confirmed that a gasoline tanker was fully involved in fire, the driver was trapped in the cab, and several civilians were injured. The tanker was an 8,000-gallon-capacity aluminum MC-306, loaded with 7,200 gallons of gasoline. The driver had lost control of the vehicle on a ramp connecting the two expressways. The tanker overturned, opened up, and began losing its fuel. Shortly after, the gasoline vapors found an ignition source, and an explosion occurred. Several civilians not involved in the accident had stopped and were attempting to free the trapped driver. However, when the explosion occurred, they were severely burned and were driven away, their rescue attempts unsuccessful. Due to the heavy fire condition, firefighters were not able to reach the driver, and the body was not recovered until conditions permitted.
When the tanker originally breached, a large amount of unburned gasoline had flowed out and entered the surrounding sewers. The ignition source could have been a passing vehicle or the tanker itself, with its hot engine and muffler. After ignition, the gasoline and the tanker were both burning. Burning gasoline was flowing downhill. When this reached the unburned gasoline already in the sewers, it also ignited, causing an explosion within the sewer system. Fire was roaring out of all nearby openings. This continued for a time, with the unburned gasoline already in the sewers coming in contact with the burning product and ignition occurring. Manholes also erupted, propelling small stones and dirt-like shrapnel and tossing their covers into the air.
First-arriving company officers had to be extremely careful about positioning their apparatus. Gasoline–both burning and not–was flowing in the streets, fire was periodically coming from sewers and manholes, and heavy traffic had not yet been stopped on either of the expressways or the service roads.
(As the officer on duty in Haz Mat 1 and one of the first company officers to arrive on the scene, I witnessed these explosions firsthand. Because the area surrounding the exit ramps and roadways was overgrown with vegetation, not all the manholes could be seen. As we would pass by one, suddenly an explosion would occur, and fire would belch out for several seconds until it subsided. While this made for some anxious moments and called for extra caution, companies still had to respond to the scene and position their apparatus. It was an experience I will not soon forget.)
All FDNY engine companies carry 15 gallons of three percent fluoroprotein foam concentrate, eductors, and foam nozzles. Engine companies were directed to take positions at hydrants and set up their apparatus for a foam operation but were told not to extinguish the fire. After several minutes, all the raw gasoline in the sewers had ignited and burned out. At this point, the IC decided to let the truck continue to burn.
Since the tanker had rolled over on its left side, the right side of the aluminum shell was now facing upward. The whole right side had melted or burned away, and the entire surface area of the liquid was exposed and burning. As the incident began to stabilize, the flow of gasoline stopped, leaving the fully involved tanker as the primary hazard. The tanker took several hours to burn out as the shell melted and burned down.
One consideration was the vehicle`s saddle tanks, which still contained diesel fuel. Hoselines were operated on these tanks to keep them from absorbing heat from the raging fire and presenting a BLEVE (boiling-liquid, expanding-vapor explosion) hazard. When the fire had burned itself out, a rescue company recovered the remains of the driver.
Although it goes against the instincts of all firefighters not to extinguish a fire, when burning gasoline is entering a sewer or storm drain system, the best course of action is usually to let the fire burn. If a significant volume of gasoline enters such a system, particularly in a populated area, it will most likely find an ignition source, and fire will occur wherever vapors are within their flammable range. When gasoline in the system does begin to burn, the results can be catastrophic. This fire can occur far “downstream” of the initial incident, resulting in fire throughout a long segment of tunnels and pipes, which will vent out to the streets above.
LEARNING FROM PREVIOUS INCIDENTS
Several previous experiences with burning gasoline tanks reinforced the IC`s decision to allow the fire to burn at this incident. Two of these incidents had occurred in the Throgs Neck section of the Bronx two years earlier. In one incident, a 4,000-gallon steel tanker hit a car and then crashed into a row of stores. In this instance, though constructed of steel, the tank breached, sending burning gasoline cascading down the street and into the sewer system. The IC initially ordered that foam be used to extinguish the burning tanker. However, because there was no way to stop the flow of product, unignited raw gasoline continued to flow. A short time elapsed before the unburned gasoline contacted the burning gasoline already in the sewer. This led to two successive explosions that rocked the neighborhood. At this point, it was decided that the tanker fire should be allowed to burn while the fires in the stores were extinguished and those exposures around the tanker were hosed down by tower ladders and handlines.
A month later, another steel gasoline tanker was involved in an accident, this time on the Bronx side of the Whitestone Bridge, which connects the Bronx and Queens. The tanker overturned and burst into flames, once again sending burning gasoline into the sewers. Though all the foam carriers in the city`s arsenal responded and several foam-carrying crash trucks from LaGuardia Airport were called as a precaution, the fire was allowed to burn. It took some time, but the fire burned itself out as exposures were protected and nearby cellars were monitored for flammable vapors with combustible gas indicators. Allowing the fire to burn in the sewers prevented an explosion.
Although burning gasoline running into sewers is not an ideal situation, it is certainly more desirable than having unburned gasoline in the sewer. When unburned gasoline is flowing, basic haz-mat procedures call for diking the spill, limiting its spread as much as possible. It is usually prudent to cover the diked product with a blanket of compatible foam to prevent ignition. When unburned gasoline enters a sewer system, foam can be added. Additionally, commercially available emulsifying and encapsulating agents can be dumped into the sewer and agitated with hose streams, breaking up the product and usually preventing ignition. Using these types of products is probably a better course of action than just applying foam, which covers only the surface of whatever is in the system and may not always prevent ignition.
The sewage treatment facility can also be a problem–and not just as an exposure hazard or an ignition source. Hydrocarbons, if in sufficient quantities, can kill the “good” bacteria that break down raw sewage. In New York City, the Department of Environmental Protection is notified of all hydrocarbon spills that enter the sewers so the treatment plants can be warned to divert the flow to a holding area if it is a sizable amount.
Aluminum tankers will melt when the temperature of the aluminum reaches about 1,2007F. The liquid in the tank acts as a heat sink, and the fire will burn at the liquid level. As the liquid (or, more correctly, the vapors of the liquid) is consumed, the exposed aluminum shell will melt down. A rule of thumb in the petroleum industry is that gasoline will burn at a rate of about one foot per hour, regardless of the surface area. Thus, without any spillage, an aluminum tanker can take several hours to burn out. The priorities are protection of life, protection of exposures, and confining any unignited spillage that does take place to protect the environment.
The 1994 incident involving the 8,000-gallon aluminum tanker called into question the safety of the large aluminum tankers. Since 1967, the United States Department of Transportation, in setting safety standards, has mandated specifications for flammable liquid cargo tanks, designated as the MC 306/DOT 406. Although the DOT regulations were standard for most of the county, local municipalities were able to write and enforce their own regulations, as long as they were at least as stringent as those of the DOT. In this regard, New York City for years had its own set of regulations covering gasoline tankers. These regulations had forbidden gasoline and fuel oil tankers to be constructed of anything except steel.
New York City stipulated that gasoline tankers operating in the city be constructed of a minimum 316-inch steel and have a maximum capacity of 4,000 gallons in separate compartments not greater than 800 gallons each. The DOT, with its less-stringent regulations, allows tanks to be constructed of aluminum. Additionally, these aluminum tankers are allowed to have a capacity of up to 14,000 gallons, although 10,000 gallons is more common. (DOT-spec MC-305 trucks, built prior to 1967, were constructed of steel.)
The trucking industry had frequently challenged New York City`s regulations, arguing that the special fleet required here amounted to restraint of trade. New York City and the fire department fought to maintain the more stringent regulations. The fire department staff chiefs lobbied the DOT, citing their fears that a large-scale disaster could occur on the crowded streets of the city. They argued that a 10,000-gallon tanker could overturn much more easily than a 4,000-gallon tanker. The aluminum could rupture, leading to a 10,000-gallon gasoline spill that would cascade down streets into basements, cellars, subway stations, and sewers. Once an ignition source ignited the vapors, an enormous conflagration would occur that would overpower available personnel, water supplies, and sprinkler systems, resulting in a major loss of life.
Despite such arguments, in 1992 the DOT`s Hazardous Materials Transportation Uniform Safety Act effectively preempted the city`s rules. Interestingly, one of the trucking industry`s arguments was a risk/benefit analysis that concluded that the DOT`s rules actually increased safety. With smaller trucks, more trips are required to deliver a given amount of gasoline. The more trips made, the more likely an accident would occur. For example, three trips are necessary to deliver 12,000 gallons in a 4,000-gallon tanker; only one trip is necessary with a 12,000-gallon tanker. What was not said was that any accident occurring, while perhaps only one-third as likely, would probably be three times as disastrous, since it would involve three times as much gasoline.
After the new regulations took effect in 1992, the larger trucks were not widely used initially, because most carriers continued to operate their existing fleets of 4,000-gallon tankers. Still today, due to congested city streets, the largest tankers are not as prevalent as they are in the suburban areas surrounding New York City. The typical trucks seen in the city today are up to 8,000 gallons. Time will tell if in fact the DOT made a wise decision. n
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(Top left) The need to protect possible exposures is a consideration the incident commander must include in devising a strategy to deal with any incident. At this fully involved gasoline tanker fire, firefighters initially attempted to apply water to the underside of the overpass, to prevent the intense heat from weakening the I-beams and causing spalling of the concrete. While protection of an exposure ordinarily would be standard operating procedure, in this instance it was abandoned, because the intense heat overcame the cooling effect from the handlines. As a result, the overpass was closed for several weeks for reconstruction. (Photo by Steve Silverman.) (Top right) A foamline stands stretched, charged, and ready to operate if necessary. In such instances, the IC must determine what is to be gained by extinguishing the fire and then possibly having several thousand gallons of highly flammable and volatile gasoline in a container that is completely useless. The retained heat from the tanker itself also presents a reignition source. Due to the amounts present, some unburned gasoline will almost certainly flow out of the damaged tanker. Note the use of the concrete divider as a point from which to operate behind, shielding the nozzle team from much of the radiated heat. (Photo by Steve Silverman.) (Bottom left) Gasoline escaping from the tanker is allowed to burn harmlessly along the roadway, in a somewhat controlled fire. If extinguished, gasoline will still continue to flow, possibly finding an ignition source with catastrophic consequences. (Photo by Steve Silverman.) (Bottom right) Due to the nature of the exposures at this fire, exposure protection was a necessity. The steel gasoline tanker hit a car and then crashed into a row of stores; overturned; and spilled its load, igniting a major fire. Responding companies were faced with trapped and injured occupants, a large structural fire in addition to the burning tanker, and burning gasoline flowing down the st
FDNY`S FOAM CAPABILITIES
While in some situations it may be the better course of action to allow a fire to burn itself out, this is certainly not always the case. If a fire involving flammable liquids must be extinguished, an unignited contained spill must be protected from ignition, or a toxic material is to be covered for vapor suppression, foam is usually the agent of choice. When foam is necessary, FDNY`s available resources are formidable.
All engine companies carry 15 gallons of three percent fluoroprotein foam concentrate with the necessary appliances to generate and apply foam. In addition, all engine, ladder, rescue, and squad companies carry a 212-gallon extinguisher containing AFFF.
When it is necessary to deliver large amounts of foam quickly, several types of special apparatus are available. Foam Carriers, or Foam Units, are 1,000-gpm pumpers that have been converted to foam usage. They carry 500 gallons of fluoroprotein foam concentrate in their booster tanks. Also stocked on these rigs are 120 gallons of fluoroprotein foam concentrate and 100 gallons of alcohol-resistant foam concentrate, all in five-gallon cans carried in the hosebeds and on the sides of the apparatus. Eight such units are in service, all quartered in engine companies and staffed by the engine company when necessary. Neighboring engines are trained to be backups in the event the primary company is unavailable.
The Foam Tender Unit is a single custom-built tanker with three 1,000-gallon compartments. This rig carries 2,000 gallons of fluoroprotein foam concentrate in two compartments and 1,000 gallons of alcohol-resistant foam concentrate in the third compartment. It can supply foam concentrate via a 200-gpm pump. It is housed with an engine company in Brooklyn; its members staff the rig. Additional engines are trained as backups.
For supplying additional amounts of fluoroprotein foam, 12 engines located around the city have been designated as Bulk Foam Units. These units each maintain a storage tank in their quarters filled with 500 gallons of fluoroprotein concentrate, with a pneumatic transfer system. When needed, these units empty the water from their booster tanks and transfer the foam concentrate into the booster tank prior to responding. Instead of designated backup companies, all FDNY engine companies are capable of responding to one of these quarters and transferring concentrate to their booster tanks.
When high-expansion foam is needed for inaccessible Class A fires or for Class B fires under certain circumstances, the High-Expansion Foam Unit is available. This unit is a converted 1,000-gpm pumper that contains 500 gallons of high-expansion foam concentrate in its booster tank; an additional 100 gallons of concentrate are carried in five-gallon containers. This unit has an apparatus-mounted large-capacity foam generator that can supply high-expansion foam at a rate of 15,000 cfm through its application chute. It also carries a smaller, portable 7,500-cfm high-expansion foam generator. This unit is also quartered in an engine company in Brooklyn and has two companies trained as backups.
Additionally, nine engines throughout the city are designated as Foam Storage Depots. These units maintain a large supply of five-gallon containers of fluoroprotein, high-expansion, and alcohol-resistant foam in their quarters. These containers are put in the hosebeds of the engine when their response is required. n
Reference
Calderone, Battalion Chief John. “Special Apparatus,” WNYF 1/96, p. 22.
PETER M. STUEBE is a 19-year veteran of the City of New York (NY) Fire Department, the captain of Haz Mat Company 1, a member of the West-chester County (NY) Hazardous Materials Response Team, and a former haz-mat instructor at the FDNY Bureau of Training. He has a bachelor`s degree in business from Marist College, a master`s degree in economics from Pace University, and a master of public health degree in environmental science from Columbia University. He is an adjunct instructor at the National Fire Academy.
