NTSB: Casselton collision likely caused by defective axle

Although a broken axle was the primary cause of a 2013 collision of two trains near Casselton, N.D., the subsequent oil spill and fire might have been reduced considerably had one of the trains not been carrying crude oil in older DOT-111 tank cars.    A defective axle was the likely cause of a 2013 collision between two freight trains that resulted in the spilling of 476,000 gallons of crude oil and a fire that cause the evacuation of more than 1,500 local residents, according to a preliminary report from the National Transportation Safety Board.
   NTSB said in its report the first train, which was carrying grain, derailed because of a broken axle on one of its cars and the second, a BNSF train carrying crude oil, was unable to stop in time to avoid the collision. Investigators found a void in the middle of the axle, which was used previously on another train car, prompting the American Association of Railroads has moved to require testing of secondhand use axles.
   But although a broken axle was the primary cause the collision, the subsequent oil spill and fire might have been reduced considerably had one of the trains not been carrying volatile crude oil in older, less crash resistant DOT-111 tank cars.
   The report said oil spilled from 18 of the 20 derailed DOT-111 tank cars before pooling and catching fire, at which point “other derailed tank cars eventually ruptured as the heat from the fire weakened the tank steel and increased the internal pressure until oil vapor erupted in violent fireballs.”
   There were no fatalities or serious injuries resulting from the collision, but nearly 1,500 people were evacuated from nearby homes.
   “The fact remains that trains carrying flammable liquids in DOT-111 tank cars continue to roll through America’s towns and cities,” NTSB Chairman Christopher Hart said in a statement. “Progress toward removing or retrofitting DOT-111s has been too slow.”
   As part of the investigation, NTSB also found that while the use of advanced braking systems would not have prevented the incident, it might have “mitigated the damage.”
   “In other scenarios, advanced brake systems have the potential to prevent train accidents altogether,” NTSB added.
   Regulators and industry advocates in the United States have pushed to retrofit or replace older DOT-111 and CPC-1232 tank cars as they are thinner and more likely to puncture than the newer DOT-117 models. Trains carrying flammable liquid in those older tank cars are, as a result, at a higher risk of leaking and/or catching fire in the event of a derailment.
   The DOT-111s have been blamed for a growing number of destructive derailments involving crude oil trains in recent years, the largest of which claimed the lives of 47 people in Lac-Mégantic, Quebec in July 2013.