Please, Don’t Help Us – An Addendum

In a follow up to the stories about the Graniteville, South Carolina hazardous materials incident that left 8 (now 9) dead and scores injured, the New York Times reports how ten months ago, government safety officials reported that more than half of the nation's 60,000 pressurized rail tank cars did not meet industry standards, and that there were concerns about the safety of the remainder of the tank car fleet as well.

Following a bit of detective work, I traced the quote to this source (would it have killed the Times to provide a link in their article?). It is an accident report prepared by the National Transportation Safety Board (NTSB) of a rail tank car derailment in Minot, North Dakota in January 2002. Five tank cars carrying liquefied compressed anhydrous ammonia, a liquefied compressed gas catastrophically ruptured, releasing a vapor plume. About 11,600 people occupied the area affected by the vapor plume. The incident resulted in one fatality, 11 people serious injuries, and over 300 minor injuries.

The NTSB reported that the shells of the five tank cars that catastrophically failed were built before 1989 and were fabricated from “non-normalized” steel, which was more brittle and susceptible to cracking. This was thought to result in an instantaneous release of the 146,700 gallons of anhydrous ammonia within moments of the derailment in Minot, which produced a much larger and more concentrated plume of ammonia gas than would have occurred if the same quantity had been released more slowly, allowing the ammonia to dissipate gradually in the atmosphere.

To address the problem of brittle, more easily fractured steel, the shells of pressure tank cars since 1989 been required to be fabricated from “normalized” steel. Without going into the metallurgy, this increases ductility and fracture toughness in the steel plate. According to the NTSB, the American Association of Railroads (AAR) standard for tank car shells called for using normalized steel in 1988.

During the public hearing on the accident, industry representatives and railroad regulators (including the U.S. Federal Railroad Administration – FRA) all stated that the pressure tank cars constructed before 1989 were safe and possessed a good safety record, that the catastrophic brittle failures seen in the Minot derailment were rare and that the tank cars would also have failed and released their cargoes of anhydrous ammonia anyway even if they had been made with the more crashworthy steel.

I’m quoting the following from the report (with emphasis added), because it needs to be seen to be believed:

During its public hearing on the Minot accident, the Safety Board explored possible options to reduce the risks posed by pre-1989 pressure tank cars. However, representatives from the FRA and tank car manufacturers raised various objections to each of these options based on concerns about the expense, questionable safety benefits, and new risks that might develop if existing operating procedures were changed for the railroads and shippers.

Neither the FRA nor industry representatives have offered a resolution to the issue of pre-1989 cars other than acknowledging the need to better understand the forces acting on tank cars during derailments and ranking the existing pre-1989 tank car fleet to identify the tank cars with the highest risk. Regarding the ranking of the pre-1989 pressure cars, no specific ideas were offered on how to accomplish such a ranking.

Approximately 60 percent of pressure tank cars currently in service were built before 1989 and very likely were constructed from non-normalized steel. Additionally, tank cars may remain in service for up to 50 years, which means that the last pressure tank cars constructed of non-normalized steel could remain in service until 2039. Further, according to AAR statistics, there were more than 1.23 million tank car shipments of hazardous materials in 2000 (the last year for which data are available) in the United States and Canada. Of the top ten hazardous materials transported by tank car, five were class 2 liquefied compressed gases (LPG, anhydrous ammonia, chlorine, propane, and vinyl chloride) that together accounted for more than 246,600 tank car shipments, or about 20 percent of all hazardous materials shipments by tank car.

Consequently, the Safety Board is concerned about the continued transportation of class 2 hazardous materials in pre-1989 tank cars. Because of the high volume of liquefied gases transported in these tank cars and the cars’ lengthy service lives, the Safety Board concludes that using these cars to transport DOT class 2 hazardous materials under current operating practices poses an unquantified but real risk to the public.

In a tank car crash in Texas last summer, the tank car that ruptured and released chlorine gas was made before 1989, though federal investigators have not yet concluded whether brittle steel played a role in that accident. The South Carolina crash involved the rupture of a newer tank car manufactured in 1993, according to its owner, the Olin Corporation.

The federal government’s glacial response to this problem isn’t terribly surprising (the FRA is sponsoring studies that should be completed in the next few years). What does surprise me is that emergency managers and first responders aren’t yelling long and loud about this. Also, wouldn’t better tank car survivability provide a homeland security benefit?