Some crudes from elsewhere in North America and around the globe share similar volatile properties.
But the Bakken fuel is the first to be moved in North America in modern times in such massive quantities by rail. That's exposed a new set of safety concerns, including a well-known defect in tens of thousands of rail cars that leads them to rupture in accidents.
Mile-long oil trains can carry 3 million gallons of crude per shipment. The number of carloads delivered by major U.S. railroads has surged astronomically: from 9,344 delivered in 2008 to 434,000 carloads last year. The shipments are delivered to refineries across the U.S. and Canada, including in the Pacific Northwest, California, and the East and Gulf Coasts.
Unlike most hazardous materials produced by chemical plants or other manufacturing sources, crude oil is not refined before being loaded onto trains. As a result, its properties can vary greatly among shipments. Three companies were hit with proposed penalties totaling $93,000 in February for misclassifying oil from the Bakken as less dangerous.
Through the petroleum institute, the industry also has pledged to work with the government to come up with new standards for testing the oil to make sure it's being handled properly when loaded onto trains.
That process is expected to take several more months, and will be driven in part by what's learned regarding volatility.
Cynthia Quarterman, head of the Transportation Department's Pipeline and Hazardous Materials Administration, testified before Congress as recently as late February that the industry had been working closely and sharing information with regulators.
But there were signs the government's patience was wearing thin in recent weeks. In a March 10 interview with The Associated Press, Quarterman raised the prospect the government was ready to go it alone if necessary. She said regulators had collected close to 100 samples of oil, primarily from the Bakken, to do their own analyses.
"We're working as hard as we can to get our arms around what the data we have means. It would be helpful to have some industry input as well," Quarterman said.