U-M hydrodynamics expert David Schwab ran 840 simulations of a release from the Enbridge Line 5 pipeline under the Straits of Mackinac. The study, which was supported by the National Wildlife Federation, was released Thursday by the U-M Water Center and pinpoints areas of highest risk along the shores of lakes Huron and Michigan, and on their islands.

Up to 152 miles (245 km) of coastline in lakes Huron and Michigan could be fouled by a single oil spill at the straits, according to the simulations. When all 840 simulated spills are plotted on a map, a total of 720 miles (1,162 km) of shoreline in the U.S. and Canada are considered potentially vulnerable to spills that would require cleanup. Seven hundred twenty miles is roughly the distance from Detroit to Atlanta.

Areas at highest risk include Mackinac and Bois Blanc islands, as well as locations directly east and west of Mackinaw City. Communities also at risk include Beaver Island, Cross Village, Harbor Springs, Cheboygan and other places along the lakes Huron-Michigan shoreline.

…”Until now, no one knew exactly how much shoreline was vulnerable to spills in the Straits of Mackinac,” said Schwab, a research scientist at the U-M Water Center. “These findings show that under the right conditions, a spill in the Straits of Mackinac could affect a significant amount of shoreline and open-water areas in either Lake Michigan or Lake Huron, or both, very quickly.

Other key findings

• Nearly 60 percent of Lake Huron’s open water and more than 15 percent of Lake Michigan’s open water showed visible oil in at least one of the 840 spill simulations. The total area of those vulnerable open waters—17,318 square miles (44,405 square km)—is roughly equivalent to the combined surface areas of lakes Erie and Ontario.
• The maximum open-water area covered by a single hypothetical spill is 624 square miles (1,600 square km), an area larger than Lake St. Clair.
• The shortest arrival times for visible surface oil—2.5 hours—occur on the south shore of the straits, near Mackinaw City. Mackinac Island could be impacted in nine hours, Bois Blanc Island in 10 hours. Oil could reach Cheboygan in 30 hours.
• The 63-year-old Enbridge Line 5 pipeline moves up to 20 million gallons of light crude oil, light synthetic crude oil and natural gas liquids across the straits each day. Line 5 splits into two 20-inch-diameter pipes to cross the Straits of Mackinac, just west of the Mackinac Bridge. The area around the straits is considered ecologically sensitive and is a major tourist draw.

Read on for more at the University of Michigan.