Enbridge Resisting Final Clean-Up of Its Michigan Oil Spill

Two and a half years after the costliest oil pipeline spill in U.S. history, the company responsible for the disaster is balking at digging up oil that still remains in Michigan's Kalamazoo River.

The cleanup has been long and difficult because the ruptured pipeline was carrying bitumen, a heavy oil from Canada's tar sands region. Bitumen is so thick that it can't flow through pipelines until it's mixed with liquid chemicals to form diluted bitumen, or dilbit. When more than one million gallons of dilbit poured out of the broken pipeline in July 2010, the chemicals evaporated and the bitumen began sinking to the riverbed.

Today, regulators and oil spill experts are still struggling to deal with the accident, which was the first major spill of dilbit into a U.S. waterway. The cleanup tools and techniques developed for conventional oil spills—which mostly float on water—are ineffective for submerged bitumen, so experts have had to come up with new methods.

In October, the U.S. Environmental Protection Agency asked Enbridge Inc., the pipeline's Canadian owner, to clean up several miles of the river where submerged oil is still accumulating. The proposed order told Enbridge to dredge 80 to 100 acres of the riverbed. The request was based on the results of a yearlong study the EPA conducted with oil cleanup experts, Michigan state regulators and a committee of about 15 scientists.

The dredging is needed, the agency said, because the oil could spread into uncontaminated areas of the river if it isn't removed.

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