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The propane explosion that occurred in Waverly, TN, on Feb. 24, 1978, was the high-water mark of hazardous materials incidents in the United States. In terms of loss of life to emergency responders and civilians resulting from train derailments, this incident was the last in which so many people were to die. The Waverly incident also resulted in many changes in tactics for dealing with similar fires in containers and in safety equipment on railroads.
A similar derailment occurred in Weyuwega, WI, in 1996, and the incident commander there used his knowledge of the Waverly incident to formulate tactics. That might have had a direct impact on the Weyuwega incident in terms of safety to emergency personnel and residents. There was not a single serious injury or death as a direct result of the derailment in Weyuwega. We can all learn from lessons from past incidents such as Waverly and be able to protect personnel and the public from harm. Unfortunately, sometimes our memories are very short.
Waverly is 56 miles west of Nashville and 142 miles east-northeast of Memphis. It is the Humphries County seat and had a population of 5,000 in 1978. Feb. 22, 1978, was a Monday, a typical winter day in northwestern Tennessee. Temperatures hovered in the mid-20s with about a half-inch of snow on the ground.
Photo courtesy of Waverly Fire Department
Tank car 83013 being moved from the right of way to open up the rail line. The second propane tank can be seen in the background.
At approximately 10:30 P.M., a Louisville and Northern (L&N) Railroad train heading from Nashville to Memphis derailed in the small community. Investigators determined that a wheel on a gondola car, overheated from a handbrake left in the applied position, broke apart east of Waverly. A wheel truck damaged by the breaking wheel remained with the train for seven miles before it coming loose from the car and causing the derailment. Twenty-four of the train's 92 cars left the tracks in the center of downtown Waverly.
Two derailed tank cars that contained liquefied propane played a major role in the incident that unfolded over several days. Propane should not be confused with another product called liquefied petroleum gas (LPG), which is a mixture of butane, isobutene, propane, propylene and butylenes.
Properties Of Propane
Propane is a colorless gas with an odor of natural gas (methane). Natural gas and propane do not have an odor naturally, so an odorant is added for leak-detection purposes. Propane vapor is heavier than air. It has a boiling point of -43.67 degrees Fahrenheit and a flash point of -156F. It is extremely flammable with an ignition temperature of 874F and a flammable range of 2.4% to 9.5% in air. Propane is an alkane hydrocarbon compound with a molecular formula of C3H8, which means it is saturated (all single bonds), so polymerization is unlikely. It is non-toxic by inhalation, but can cause asphyxiation by displacing the air in confined spaces.
Photo courtesy of Waverly Fire Department
Aerial photo shows the master hose streams placed in service to cool the tanks.
The primary hazard to be concerned about with propane and liquefied petroleum gases is flammability. When liquefied petroleum gases are in a container, a boiling-liquid/expanding-vapor explosion (BLEVE) can occur under certain conditions. Those include direct flame impingement on the vapor space of the container, over pressurization of the container, or physical damage to the container shell or a combination of factors. Incident commanders should be well aware of these potential effects on the integrity of liquefied petroleum gas pressure containers.
The explosion in Waverly was unusual because it did not involve flame impingement on the tank. When the derailment occurred, there were no leaks, no fires, no explosions; nothing overly exciting resulted beyond the derailment of the cars themselves. This may have been one of the primary factors that led response personnel and others to let down their guard, leading to disaster two days later.