The Mackinac Bridge over the Straits of Mackinac Jimmy Yeh/Flickr

Lakes Michigan and Huron come together and exchange fluids in one place: the Straits of Mackinac. There, their waters mix and mingle, strongly flowing either east or west, depending on the wind and weather. How the water flows hinges on myriad factors, making the currents very unusual and unpredictable, says hydrodynamics expert Dave Schwab, who began modeling their peculiar ways four years ago.

About 300 feet below those churning waters lies Line 5, an oil and gas pipeline owned and operated by the Canadian energy company Enbridge. Line 5 stretches 645 miles from Superior, Wisconsin, to Sarnia, Ontario. Under the straits, it splits into two parallel pipelines that carry about 20 million gallons of oil and natural gas fluids a day. Line 5's been sitting there since 1953, and there is growing concern that the old pipe may rupture.

Until a few years ago, scientists were unable to predict where and how far the crude might go should that occur. Now they can. A new report, based on Schwab's research out of the University of Michigan Water Center, details what sections of Michigan’s shoreline would get slicked. The report’s publication comes at a time when environmental groups are pushing for Enbridge to shut down Line 5 and the state is trying to determine which of the region's resources, such as tourist destinations, protected areas, and fishing grounds, are most at risk from a spill. “It’s the worst place for an oil spill in the Great Lakes,” says Schwab, a statement he’s made before.

Schwab conducted his first simulation of the straits two years ago with funding from the National Wildlife Federation, or NWF. The environmental nonprofit published a report in 2012 warning that a break in Line 5 could cause great damage. Schwab told Mike Shriberg, director of NWF's Great Lakes Regional Center, that his models could help illustrate why. The hydrologist then conducted an even more detailed analysis, one that showed which spots along the shoreline would get hit hardest if the light crude, light synthetic crude, and natural gas liquids flowing through Line 5 escaped.

Schwab did this by simulating spills under 840 different weather conditions and with three hypothetical spill volumes (5,000, 10,000, and 25,000 barrels). According to his results, a worst-case scenario would put more than 700 miles of coastline at risk, including popular destinations like Mackinac Island and Wilderness State Park, which includes islands that provide a third of the remaining habitat in the Great Lakes for endangered piping plovers. A spill there, says Schwab, would be "devastating." And because water in the Straits of Mackinac​ moves at a quick rate of three feet or more per second, containing that crude would be extremely difficult, he says. Imagine holding your thumb over the nozzle of a hose, making the stream to spray. The land pinches the lakes at the straits in much the same fashion.

The piping plover is endangered in the Great Lakes region. U.S. Fish and Wildlife Service

In addition to its perilous location, Line 5 is past its prime. When constructed 63 years ago, its builders estimated the pipeline’s lifespan to be 50 years. This is not an expiration date environmentalists think we should ignore. NWF sent divers down into the straits in 2013 to record video and get a glimpse of what shape the pipelines were in. Line 5 was missing its support structure in places, violating the easement agreement with the the state that requires them every 75 feet. As you can see here, the pipelines float above the lake bed for longer stretches (a problem the company says it has since fixed). In other areas, mussels and debris blanket the steel.

A summary of inspection records released by Enbridge in 2013 also points to nine areas where the pipes' steel is thinner than normal. Blake Olson, the company's regional manager for much of Line 5, says the steel has probably been that way since the pipeline's installation in 1953, and he's not worried. He says technologies today can measure the pressures and amounts of oil traveling from one meter to the next, which allows managers to keep a closer eye on how Line 5 is running. “We’re constantly testing, constantly watching,” says Olson. “All those tests to this point show that Line 5 is in excellent condition.”



Olson's company, however, has its skeptics—and for good reason. Between 1999 and 2010, Enbridge has been responsible for more than 800 spills in the United States and Canada. Enbridge’s 6B pipeline ruptured in 2010, causing the largest inland oil spill in U.S. history (one that oozed 843,000 gallons of crude into the Kalamazoo River). The company didn't shut off the flow for 17 hours and was said to have a "culture of deviance" by investigators at the National Transportation Safety Board. Five years later, crude was still mucking up the Kalamazoo.

In regard to the Great Lakes, Enbridge has refused reporters’ requests to see more inspection records from Line 5, so there’s nothing to compare the company's 2013 numbers to. That has led some journalists to report that the pipelines may not be safe. To get a more accurate assessment, the Michigan Petroleum Pipeline Task Force, a group put in place by Governor Rick Snyder to assess the pipeline in 2014, is now looking into economic and environmental consequences of a Line 5 spill. The contractors will look into how the pipelines might affect the region's drinking water, its wildlife, and its fishing and tourism industries, for instance, in analyses expected later this year.

Both Schwab and Enbridge’s Olson welcome the third-party analysis. Schwab says, along with his simulations, it could help first responders know where to go and what to expect should the pipeline bust; Olson says it could prove what the company’s been saying about the pipeline’s condition. NWF’s Shriberg, meanwhile, hopes the task force will give regulators what they need to shut down Line 5 for good.

In the meantime, Michigan has been preparing for the worst. The state even brought emergency responders together last fall for a mock oil spill (they didn’t publish their results). Some legislators, including U.S. Representative Candice Miller, are calling for the U.S. Department of Transportation's Pipeline and Hazardous Materials Safety Administration to shut the pipeline down if it poses a significant risk.

If Miller's bill moves through Congress, Schwab’s simulated currents could give it a push. His videos illustrate the oil threat in the Straits of Mackinac in a way that would be difficult to visualize otherwise. “If a picture is worth a 1,000 words, an animation is worth 1,000 pictures,” he says. “I love my animations.”

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