Oil from a 61-year-old Enbridge pipeline beneath the Straits of Mackinac, at the junction between Lakes Huron and Michigan, could contaminate shorelines 35 to 50 miles away in 20 days if the pipeline ruptured, according to a hydrodynamics study for the U.S. National Wildlife Federation. Enbridge said the pipeline, which carries nearly 23 million gallons of crude oil per day through two 20-inch pipes, is in good shape. “If you were to pick the worst possible place for an oil spill in the Great Lakes, this would be it,” said report author David Schwab of the University of Michigan Water Center.