Line 6B of the Lakehead oil pipeline ruptured near Marshall, Mich., last July, spilling oil into the Talmadge Creek and Kalamazoo River. The U.S. Environmental Protection Agency said it estimated more than 23,000 barrels of so-called heavy oil spill into regional waters.
Ralph Dollhopf, the EPA's incident commander for the spill, told the Kalamazoo Gazette the Marshall spill was new ground for his agency.
"At minimum, we're writing a chapter in the oil spill cleanup book on how to identify submerged oil," he said. "We're writing chapters on how it behaves once it does spill (and) how to recover it."
The nature of oil from tar sand deposits causes some of it to sink to the bottom of the river, where it has soaked about 6 inches of sediment along the river bottom.
The EPA recovered about 18,000 barrels of oil that was originally on the surface. EPA officials said it was unclear how the remaining oil would affect the environment because there is no other spill with which to compare the Enbridge leak.
"We don't have any other frame of reference," Dollhopf said. "I can't tell you this is characteristic of tar sands. We don't know anything about tar sands. We only know about this oil."