Bart Jansen

USA TODAY

WASHINGTON – Federal investigators ruled Tuesday that the fiery collision of two BNSF Railway trains in North Dakota, which spilled nearly 500,000 gallons of crude oil, resulted from an axle breaking beneath the car of one train because of a manufacturing defect.

The accident, which was the NTSB's first investigation of a major crude-oil spill, helped build concerns about tank-car safety. The North Dakota collision followed a fiery July 2013 derailment in the Canadian town of Lac-Megantic, which killed dozens of people.

“I look at this as being a wake-up call in the United States when it comes to the transport of crude by rail," said Robert Sumwalt, the board member who worked the scene of the accident.

A westbound grain train derailed first on Dec. 30, 2013, near Casselton, N.D. Then an eastbound oil train collided with one of the grain cars, punctured 18 of its oil cars and exploded, according to the National Transportation Safety Board.

Nobody was killed in the crash, but it caused an estimated $7.2 million in damage. About 1,560 people were evacuated from Casselton about a mile from the crash because of a thick plume of smoke from the fire; they returned a day later.

Congress and the Pipeline and Hazardous Materials Safety Administration (PHMSA) have demanded higher safety standards for tank cars as freight trains link more cars carrying flammable liquids.

Tank cars called DOT-111 cars that have been in service since the 1950s are easily punctured, which can allow spilled fuel to pool and explode. PHMSA required railroads to adopt safer tank cars called DOT-117, which have thicker shells and other safety features, with deadlines ranging from 2018 through 2029.

NTSB Chairman Christopher Hart said the long timeline and lack of progress reports would leave “Americans at heightened risk for many years to come.” Few 111 cars remain in service carrying oil, but “a vast fleet” still roll through U.S. cities transporting ethanol or other flammable liquids, Hart said. In April, BNSF will begin offering incentives for shippers to switch to 117 cars, he said.

“Progress has been slow,” Hart said. “It is our hope that despite the progress to date, no future catastrophic tank car failure will give us reason to reiterate the importance of milestones and transparency in another board meeting between now and 2029.”

The board voted 4-0 to recommend to PHMSA that all trains transporting hazardous materials should have at least five buffer cars between occupied cars and hazmat cars, rather than the minimum of one car that is now possible, as was the case with the Casselton accident. The goal is to have a larger buffer between the train crew and spilled hazardous materials or fire.

In the Casselton derailment, a broken axle from the grain train was found with a manufacturing defect at the scene that was part of a 2002 production lot from Standard Steel of 48 axles, which had two other failures. The NTSB issued a safety recommendation in April 2014 for railroads to test second-hand axles for flaws.

The Association of American Railroads worked collaboratively with Standard Steel to identify and remove the axles from service, Hart said.

The investigation found that as the collision unfolded, a railroad worker on the ground noticed on his portable computer that the grain train was tearing up parts of the track with what was later found to be the broken axle on the 45th of 112 cars. But as the worker tried to radio the train’s crew, he heard them report “they were on fire” after derailing, investigators found.

The crew abandoned the grain train. But almost immediately, the crew of the oil train passing in the other direction on the neighboring track couldn’t brake fast enough at 42 mph to avoid a collision, the investigation found. The train spilled an estimated.476,437 gallons of oil.