A damaged, 36-year-old piece of rail caused the 2013 derailment and explosion of a Canadian National Railway Co. train hauling propane and oil near Edmonton, investigators say.
Track defects picked up in tests were disregarded two months before the 13-car derailment that caused the evacuation of more than 100 homes in Gainford, Alta., the Transportation Safety Board says in a report.
The report comes one day after the head of the TSB issued a new call for the government to implement tougher standards for tank cars that carry crude oil.
The 2.6-kilometre train was hauling 134 cars to Vancouver from Edmonton in October, 2013, when it entered a siding at 39 kilometres an hour to make way for an oncoming train. One rail on the siding, which was found to have cracks not visible to the eye, gave way and the cars derailed, setting off a chain of events that led to the propane exploding in a fireball that reached the adjacent highway.
"When a derailment happens, there are tremendous forces that are generated. It's highly unlikely that any tank car built today could have survived this," said George Fowler, the TSB's lead investigator for the incident and a former CN engineer who spent 30 years operating trains.
Railways test track using ultrasonic equipment designed to pick up flaws that cannot be seen. Two months before the Gainford explosion, test machinery detected a defect in the rail, but the person operating the equipment blamed surface rust or flaking.
"Rail testing is not an exact science. Skill, training, and experience are required to properly interpret the test data and identify rail defects," the TSB report said.
Since 2005, the TSB said, rail defects missed in tests have caused several derailments involving dangerous goods, including a 2011 incident near Alix Junction, Alta., in which 900 litres of phosphoric acid was spilled. In 2005, a derailment of 43 cars hauled by CN spilled 700,000 litres of bunker oil and 88,000 litres of pole-treating oil in Wabamun, Alta.
CN spokesman Jim Feeny said the Gainford incident prompted it to retest and grind the rails in all its high-speed sidings to find and eliminate problems.
The derailed tank cars containing crude oil were DOT-111 models that had been upgraded and did not spill any crude because they rolled on their sides and were not struck by other cars, the TSB said. No one was injured.
The federal government last week introduced legislation that would require shippers of crude oil to pay $1.65 a tonne into a fund that would be used to cover costs of cleanup and compensation to victims after existing railway liability insurance levels were exceeded. Shippers of propane, butane and other dangerous goods were excluded because oil is consider a bigger concern.
The explosion of a train in Lac Megantic, Que., in July, 2013, that killed 47 people spurred regulators to enact new rules intended to improve safety. But despite lower speed limits, beefed-up tank cars and more inspections, derailments and fires continue.