Heavy rain that pushed the Kalamazoo River over its banks last month is being factored into the next stage in the long-running cleanup of the nation's biggest and most expensive oil pipeline spill—the 2010 accident that dumped more than 1 million gallons of oil into and around the river near Marshall, Mich.
The April flooding created the potential for the marble-sized globs of oil that had settled to the bottom of the river to be picked up by the swift current and swept into parts of the river previously untouched by the spill.
A month before the river crested, the U.S. Environmental Protection Agency ordered the pipeline's owner, Enbridge Inc., to remove large pools of oil that remain at the bottom of three areas of the river. The order was triggered by the findings of a yearlong survey of nearly 6,000 locations along the 40 miles of river contaminated when pipeline 6B ruptured in July 2010.
As part of the survey, a team of 14 federal, state and local organizations coordinated by the U.S. Geological Survey modeled the river to show how it would behave at various flood levels.
If the river rose to certain levels, the model suggested that the submerged oil—diluted bitumen or dilbit from Canada's oil sands region—could be stirred up enough to migrate into different parts of the river. The EPA was so worried about the amount of oil that remains in the river, and the possibility that it could migrate, that it ordered Enbridge to dredge the three areas, a step the agency had tried to avoid because it is so damaging to the river.
The river reached that level of concern in April, said Steve Hamilton, a Michigan State University professor of ecosystem ecology and biogeochemistry who worked on the EPA study.
To gauge the accuracy of the study's model, Hamilton and his wife launched onto the river in kayaks. The swift water quickly carried them nearly a mile downriver near the Fort Custer Recreation Area where the river had overflowed its banks. Using trees to anchor the kayaks against the current, Hamilton compared what he was seeing, and what he was measuring with a flow meter, against the study's predictions.
"What I was seeing said the modeling correctly predicted the behavior of the river at the flood stage we were experiencing," said Hamilton, who was speaking as an independent scientist, not as an EPA representative.
The question now is: Did the submerged oil move into new sections of the Kalamazoo River?
"It certainly says the oil could have become mobile and migrated," Hamilton said. But it's also possible that the flood waters broke up the oil and diluted it so much that it's now less of an ecological threat to the river, he said.
"We just don't know yet," Hamilton said.
Testing to determine whether the flood redistributed the submerged oil is going on now and may not be complete until early summer, Hamilton said. The results will not only tell officials what happened to the oil during the flood but also serve as a roadmap for Enbridge to comply with the EPA's March cleanup order.
Since Line 6B ruptured, the massive cleanup has cost Enbridge more than $820 million. Enbridge says 843,000 gallons of oil spilled from the ruptured pipeline, but documents filed with the EPA show that, so far, 1,149,460 gallons of oil have been removed from the river and its banks.
Removing dilbit from water is more difficult than removing conventional oil because the chemicals used to thin the bitumen gradually evaporate, while the bitumen sinks to the river bottom. Conventional oil usually floats on water where it can be collected and skimmed off. Dilbit is the same type of oil that the Keystone XL pipeline would carry from Alberta, Canada to the U.S. Gulf Coast if the Obama administration approves the project.
Enbridge spokesman Larry Springer said the flooding of the Kalamazoo is a "common occurrence" and that other floods since the spill hadn't caused any negative effects.
"This year, like every year in our response, we continue to monitor the Kalamazoo River downstream of our impacted area," Springer said. "To date, product from Line 6B has not been found beyond this impacted area."
But the EPA study found that the oil has moved over the years. In the fall of 2011, an estimated 189 acres of river bottom near Morrow Lake showed submerged oil. By the spring of 2012, the area affected had grown to 325 acres.
Springer said the company is working on a plan for the next cleanup effort, but no date has been set to begin the work. A statement on Enbridge's website says the company is "focused on cooperation with the EPA and other authorities in doing what is best for the river and the environment based on analysis and sound science."
Beth Wallace, Great Lakes community outreach regional coordinator of the National Wildlife Federation, said any movement of the oil could create new environmental problems.
"It's really important to understand where that oil is and where it may be going," Wallace said. "If it enters certain sensitive habitats then it can cause a great amount of harm."
Jay Wesley, a fisheries expert with Michigan's Department of Natural Resources, said he'll be interested in seeing the results of the latest round of tests. Although this year's flooding wasn't catastrophic, "you never want to see the migration of the oil increase," he said.
Wesley said some of the oil could have been swept into natural collection sites where the oil is already pooling in the river, a result that would be less harmful and make the cleanup easier.
"I'd much rather see the oil gather in those areas than to go throughout the whole river," he said.
Three sections of the river covering 100 acres are scheduled to be dredged. That's four times as much dredging as was done in earlier cleanup efforts. The additional work could take up to a year and push the cost of the cleanup to more than $1 billion.
The study of the contaminated 40-mile section of the Kalamazoo that resulted in the EPA's order began in 2011 and ended last August.