Union Pacific has hauled two types of oil through the gorge -- a thick, waxy crude from Utah and Bakken crude from North Dakota. In late 2015, the company began moving one mile-long train of Bakken oil each week on the Oregon side of the gorge to Tacoma. It is unclear which type of oil is involved.
"We don't know whether there's any environmental damage including whether there's spillage to the Columbia," said Jennifer Flynt, a Department of Environmental Quality spokeswoman.
Oil spill response crews from the U.S. Environmental Protection Agency, Department of Environmental Quality and National Response Corp., a contractor that works with Union Pacific, are all en route, she said.
The Washington Department of Energy is flying over the spill site to determine whether oil reached the river, Flynt said.
