In 1987, seven more grout-bag supports were added. In 1992, six more spots were fortified. An inspection in 1997 revealed no apparent problems, but four years later it was a disturbingly different story.

On a Friday in September 2001, Enbridge officials contacted Michigan environmental regulators and reported they needed to do “emergency preventative” work on the pipeline. The urgent tone of a memo contradicts the company’s insistence today that this has always been a pipeline built for the ages, one that can operate “indefinitely.”

By the following Monday, that application — written in pen — arrived on the desk of state environmental regulators.

“Project is to provide support underneath our pipelines in sections where the pipeline spans un-supported over too great a distance,” Enbridge staff wrote. “In order to maintain the integrity and safety — these maintenance repairs can wait no longer.”

Eight supports were placed that fall, but the job wasn’t done. Sixteen more were added in 2003. These were not sacks of grout, but steel brackets held in place by giant screws drilled into the lakebed.

The work still wasn’t done.

In 2004, 16 more of these brackets were placed. In 2005, 14 were added, along with another 12 in 2006. Another seven were installed in 2010, and another 17 in 2012. Two years later, the company installed an additional 40 supports, and reported that the “average” unsupported span would then be less than 50 feet, well within the easement limit of 75 feet.

Two years later — last summer — the company was back with plans to add the 22 new supports.

Pipeline critics worry that even though the pipes might now be more firmly anchored to the ever-eroding lakebed than they were a decade or two ago, the steel could have incurred invisible structural damage during the periods the pipes were left hanging in the swirling current, much like a prizefighter who has taken too many body blows.

“We don’t know how hard it got bent around in those earlier years, so without that data it’s hard to say what condition it is in,” said Ed Timm, a retired senior engineer and oil refinery expert who has become an outspoken critic of the Mackinac pipeline.

Earlier this year, the company, under pressure from Michigan politicians to be more transparent, released data showing that in places the 7/8-inch pipe is actually only about two-thirds that thick. This is something Enbridge attributes not to corrosion but to how the pipe was constructed. The company said these thin spots in no way compromise the safety of the pipe, and in June it released an analysis from an outside firm (using Enbridge data) that affirmed the company’s position that the pipeline remains in excellent shape.

Yet if something, somehow, someday does go wrong, Enbridge officials insist alarms would go off and that valves could be closed within minutes to stanch a spill.

But even if automatic shut-off valves work as designed, in 2015 Enbridge acknowledged a plume of some 200,000 gallons could be unleashed into the Straits.

Worst possible place

The National Wildlife Federation in 2016 hired the University of Michigan’s Dave Schwab to figure out where the Straits currents would drive the oil if a spill ever happened. Schwab, a renowned authority on hydrodynamics, concluded there is no worse place in all of the Great Lakes for a crude oil spill.

Schwab ran 840 simulations under various current, weather and spill scenarios and concluded that up to 152 miles of shoreline could be fouled by a single oil spill, and more than 700 miles of Great Lakes shorelines were vulnerable to a Straits pipeline spill.

University of Michigan Graham Sustainability Institute | See all scenarios

University of Michigan Graham Sustainability Institute | See all scenarios

Schwab’s models predicted the first oil bursting from the pipes could be washing onto the Straits’ southern shore, near the fudge shop-packed main street of Mackinaw City, in just three hours.

Within nine hours, it could be lapping at the shores of Mackinac Island, home to a colonial fort overlooking the Straits on a 3.8-square-mile patch of rolling forest so scenic it was second only to Yellowstone in being designated a national park. (Yellowstone was established in 1872, and Mackinac three years later, though the park was turned over to the State of Michigan in 1895.)

Schwab evaluated spill scenarios that involved 5,000 barrels, 10,000 barrels and 25,000 barrels. One scenario showed a spill could smother more than 620 square miles of open water and spread so far west it could soon be lapping at the shores of the U.P.’s Garden Peninsula, about 40 miles of open water north of Wisconsin’s Door County.

Timm, the retired engineer, is equally worried about the integrity of the land-based sections of Line 5, which is built of thinner steel.

Those sections have a history of leaking, and also could unleash a massive oil slick upon Lake Michigan were a significant breach to occur. The pipeline crosses some of northern Michigan’s most famous trout streams, all of which flow toward the Great Lakes and all of which, Timm contends, are as ecologically vulnerable as the Straits.

“What’s it worth to not have trout in the Au Sable River for generations?” he asked of the famously trout-rich river. “What I’m saying is every inch of the pipeline needs to be looked at.”

Enbridge has been harshly critical of the Straits study because it did not factor in efforts to contain and clean up a spill in the hours and days after it happened. The company also maintains emergency valves could cap a spill in a matter of minutes so its worst-case spill would be about 5,000 barrels. That’s well under Schwab’s worst-case scenario of 25,000 barrels, or more than 1 million gallons — a figure picked because it is roughly equivalent to Enbridge’s Kalamazoo River spill of 2010.

Steven Keck, the U.S. Coast Guard’s oil spill contingency preparedness specialist in the Upper Peninsula, says the agency has trained for years to respond to an oil break in the Straits.

But he says that the Coast Guard is not the primary party responsible for a cleanup; the agency would coordinate a response but would only augment boats and equipment brought in by Enbridge and its contractors.

Still, if a spill were to happen in winter, the Coast Guard response would be essential, because it owns the ice breakers that could be needed to get recovery equipment to an oil spill.

Keck said no ice breakers are idled near the Straits in case of such a disaster. Rather, they are out doing their job — breaking ice at ports around the Great Lakes or freeing stuck freighters. It could take days for them to respond.

“If they happen to be in the Straits breaking ice, they’re going to be on the scene immediately, obviously. But let’s say they’re down in Chicago. It’s going to take them probably 24 to 48 hours to get up there,” he said. “It really depends on where they’re at, what the ice conditions are and what they are doing."

That doesn’t mean the Coast Guard couldn’t adequately respond to a spill, he said.

“Absolutely we’re confident we can respond. What the ice creates is a challenge, that’s all.”

In some cases, he said, the ice could even help corral the oil, or keep it from drifting on currents and spreading to shorelines.

In fact, Keck said waves at any time of year pose just as big of a problem, if not bigger, because they can keep even the Coast Guard’s biggest ships from responding. Keck wouldn’t put a number on the size of waves it would take for a captain to call off a response, though he said swells of 6 feet could meet that threshold, and waves that size on the lakes are not uncommon.

“You’re going to hope for the best-case circumstance, where you have calm seas, and calm winds and a slow current and open water where you can get at it quickly,” he said.

Anything less than a spill under best-case conditions, particularly if it happens in winter, is going to be rough.

In February 2013, the Coast Guard conducted a four-day spill response exercise in which peat moss and orange peels were used to simulate the crude oil carried by the Mackinac pipes. Here are some highlights of what was learned:

“Operation in cold, low-visibility and high-wind environments are hazardous and require special care and awareness.”

“Ensure onboard heating resources are available to defrost frozen pumps and fittings.”

“Icebreaker may be necessary to ‘break out’ and assist other vessels to make way through ice.”

“Cellphones were not reliable when operating from an open deck while underway due to cold effects on batteries and freezing of electronics. They are also difficult to handle and make calls without removing gloves.”

“More personnel may be required to manage equipment in harsh conditions but may result in increased safety and supervision complexities.”

“Frequent crew rotations are necessary in cold weather.”

Scientists studying previous open water oil disasters at sea have said that a recovery effort is lucky to capture 15% of the oil released in a spill. Crews typically use booms to corral the oil and then skimmers to suck it off the surface and onto barges or other vessels for disposal.

In some cases, if the oil is thick enough, cleanup crews will light it on fire. Usually, the bulk of a spill is left to drift on currents, disperse into the water column and decay. But the Great Lakes are a vastly different environment from the areas of ocean where high-profile spills have historically happened.

“It goes without saying a major spill in the Great Lakes would be a disaster of epic proportions given the fact that we are one of the largest bodies of fresh water in the world and millions of people drink the water,” U.S. Sen. Gary Peters (D-Mich) told the U.S. Coast Guard Commandant Adm. Paul F. Zukunft during a hearing of the Subcommittee on Oceans, Atmosphere, Fisheries and Coast Guard in spring 2015.

Andre J. Jackson / Detroit Free Press Enbridge workers skim oil off the Kalamazoo River in July 2010 after a pipeline ruptured, creating the largest inland oil spill in U.S. history.

“With pipelines usually it’s just a matter of time before they leak and a 60-year-old pipe going across five miles of Great Lakes is a frightening prospect for me, particularly coming from Michigan, where we had the largest oil spill, pipeline spill, in history just a few years ago in the Kalamazoo River.”

The Coast Guard’s Zukunft said nothing that day that indicated he was confident his agency could handle such a disaster, or that the lakes would quickly heal themselves.

Heavy crude remains contentious issue for Enbridge, Michigan In 2015, the State of Michigan pushed Enbridge to go on record that it has no plans to transport heavy sands oil — called bitumen — through its pipelines running under the Straits of Mackinac. The state and Enbridge ended up signing a memorandum to clarify the issue, though the agreement did anything but that. In the memorandum, Michigan stated that it wanted heavy crude banned from the Straits after a state pipeline task force report “found that because heavy crude oil has different properties from light oil, it is more likely to sink if released into open water.” That report also noted that the Coast Guard had gone on record that it had no effective means to capture that sinking heavy crude. Enbridge balked. “Enbridge does not agree with the task force report’s conclusions regarding the properties of heavy crude oil and notes that the issue of whether the transport of heavy crude oil raises any unique safety or environmental concerns is currently being studied by the National Academy of Sciences,” reads the memorandum signed by both sides. “Enbridge does not concur that transporting heavy oil raises any unique safety or environmental concerns.” A National Academies report, released in late 2015 after the memo was signed, concluded that heavy oil is indeed more likely to sink — and that oil on the bottom of an ocean or a Great Lake is harder to clean up than oil floating on the surface. As for shipping heavy crude across the Straits of Mackinac, the memo between Enbridge and Michigan states that Enbridge has never run heavy crude through the Straits. Though the company has no plans at the moment to change that, the memo says Enbridge does reserve the right to pursue pumping heavy crude through the Straits, provided the company appropriately fortifies the lines and meets all relevant laws. If Enbridge does one day decide to pump heavy crude through the Straits, the memo states Enbridge will give the state 180 days’ notice of its intentions, and that it will not start pumping the oil until it gets the state’s approval — or until it gets a “final resolution” if there is a dispute. Show More

“That is a very pristine environment and so you don’t have some of the microbes that you do in the Gulf environment that will normally decay what oil remains,” Zukunft said.

One of the reasons the Kalamazoo River disaster was so costly was it wasn’t just a run-of-the-mill spill; it was heavy crude from the Alberta tar sands called bitumen, a peanut butter-thick product that has to be infused with chemicals so it can flow in a pipe.

In the case of a heavy crude spill into a body of water, much of it sinks to the bottom. The Mackinac pipeline has not been used to carry bitumen like the Kalamazoo line but instead runs a lighter crude, which is more likely to float.

Last June, the State of Michigan, using Enbridge money, commissioned a firm to evaluate what the financial costs would be of a Straits spill. The study isn’t expected to be finished until later this year at the earliest, but it’s already clear the costs could be astronomical, given the $1 billion price tag for the Kalamazoo River spill, which started in Marshall, Mich., near a creek shallow and narrow enough to walk across.

A 2015 pipeline report by a task force overseen by Attorney General Schuette revealed that at one point Enbridge acknowledged a wintertime Straits response could cost up to $900 million, roughly equal to the amount of insurance an Enbridge spokesman said the company holds for its entire pipeline network. Enbridge later said that was an overestimate, and that the actual cost would be about half that. Whatever the actual response price tag is, it is a figure that only covers the cost of trying to recapture the spilled oil.

“Notably, these estimates did not include any damages to persons, property, or natural resources for which Enbridge would be liable,” the pipeline report stated.

Michigan political leaders clearly recognized long ago that the Straits are a distinctly valuable economic and environmental resource; under terms of the 1953 easement with the State of Michigan, the pipeline owners were specifically required to carry an insurance policy just to cover spill costs in the Straits.

The state set the minimum value of that policy at $1 million.

Pipeline pressures

The pressure to remove, replace or change the way the twin pipelines operate is coming from many levels of Michigan politics.

Grass-roots groups in northern Michigan continue their campaign to press local governments to pass resolutions opposing the pipeline. The state-commissioned studies evaluating the pipelines’ risk and alternative routes to carry the Mackinac oil are well underway. The National Wildlife Federation has filed a lawsuit to force a shutdown of the lines based on what it says is the federal government’s improper approval of a spill cleanup plan.

Mark Hoffman / Milwaukee Journal Sentinel A sign opposing Enbridge's pipeline under the Straits of Mackinac in St. Ignace, Mich.

Pipelines are regulated by the federal Pipeline and Hazardous Materials Safety Administration, though the State of Michigan also has authority over the Straits section because the state owns the lake bottom.

Enbridge has responded with its own campaign to convince the public of the safety and value of the line, which beyond moving crude oil also delivers about 65% of the propane used to heat homes in the Upper Peninsula.

Enbridge also notes that not all of the Canadian oil running through the Straits ends up back in Canada; the company reports about 30% of the crude it carries is refined by U.S. workers in the Detroit area. Enbridge also wants people to know that it has 250 employees and contractors in Michigan and that in recent years it has paid more than $22 million in property and sales taxes.

Pipelines vs. railways There is little debate that pumping crude through a steel tube is, gallon for gallon, far more efficient — and often safer — than rolling oil down rails and roads. A 2013 Canadian study determined about 80% of crude oil in the United States between 2000 and 2010 moved through pipelines. Trains accounted for barely a sliver of the oil moved — a volume that has risen in recent years with the increased production of the North Dakota Bakken oil fields. But the report said trains have quadruple the rate of accidents compared with pipelines. While rail spills tend to be smaller in volume than pipeline accidents, they can be more menacing in terms of property damage and human injury because they are more likely to combust. The most notorious oil train accident in recent years occurred in the summer of 2013 in the eastern Canadian hamlet of Lac-Megantic. The engineer, pulling 111 cars of North Dakota crude, stopped for the night about 7 miles from the little town. He applied the brakes after he stopped the train, but those brakes failed later that night and the unmanned train started to lurch toward the sleeping community. It picked up speed along the 1.5% grade and by the time it hit town it was screaming along at 65 miles per hour. Sixty-three cars hopped the track, unleashing some 1.6 million gallons of the highly combustible oil. Subsequent explosions and fires killed 47 people, and another 2,000 were forced from their homes. Other recent high-profile tanker train accidents — dubbed “bomb trains” by safety advocates — include a 42,000-gallon spill in Oregon last summer that ignited a raging blaze in the Columbia River Gorge, and a 13-car derailment in Watertown in late 2015. Though refined petroleum products, including gasoline, are commonly carried by tankers traveling on the Great Lakes, there are no crude oil shipments. Yet. In 2013, the Indiana-based operators of Calumet Superior Refining in the city of Superior announced they were seeking a partner to bring crude oil shipping back to the Great Lakes. The Calumet refinery operators in 2013 saw a potential glut of oil headed to Superior as an opportunity to get into the tanker business on the Great Lakes. Not long after the Wisconsin Department of Natural Resources held up plans for a waterfront tanker-loading facility on Lake Superior, Calumet announced it would not pursue its shipping plan. There are no laws explicitly banning crude shipment on the lakes, though Michigan lawmakers have pushed for such a measure. The idea of shipping oil on the lakes is controversial because, unlike gasoline and other lighter fuel products that float to the surface and can be scooped up, spilled crude can sink, making cleanup difficult if not impossible. Show More

And Enbridge points out that pipelines, regardless of their history of chronic leaks, are still much safer than shipping oil on boats, rolling it on trains or putting it on trucks. The company says it would take some 668 loaded rail cars or more than 2,500 semis to match the daily capacity of the Mackinac lines.

This is a point that resonates with many people who live closest to the Mackinac Bridge — and the pipelines — who are growing weary of what they see as outside opposition based on emotion rather than facts.

“You want them taking it across the bridge in trucks?” asks St. Ignace City Manager Les Therrian, who has been critical of the anti-pipeline resolution campaign. “You want it in boats?”

He is pleased his own city council has so far declined to pass an anti-Mackinac Straits pipeline resolution, unlike Mackinaw City, on the other side of the Straits, and many counties in the northern Lower Peninsula.

Connie Litzner, mayor of St. Ignace, says it is not her job to be in the business of regulating pipelines or any other form of oil transport.

“Obviously we all know how devastating a break or leak would be,” she said. “We are all surrounded by water in one of the most beautiful places in the country. But from a political perspective, the federal government is supposed to be on top of this.

“I think we should let them do their job, and it is their job.”

Others in St. Ignace say it is mostly people in far-away cities who are pushing hard for a pipeline removal, and that these people would have a different opinion of the pipeline and its owner if they were aware how much maintenance and monitoring Enbridge staff do at the Straits.

“We’ve worked for Enbridge, and those people are A-1, as far as doing the job right. They’re right on top of everything,” said 69-year-old Larry Belonga, owner of Belonga Plumbing and Heating Inc. in St. Ignace.

He also wonders why anyone would think it is appropriate to pass the inherent risk of moving all the oil in Line 5 onto someone else.

“They say they could pipe this through Wisconsin,” he said. “Well, if they’re concerned about it leaving Michigan, why pass it onto Wisconsin?”

Chris Shepler, president of a Mackinac Island ferry line that bears his family name, says the difference is that Line 5 runs under the Great Lakes, a natural resource like none other on the planet — and through a place so well known that the bridge and Straits are on state license plates under the slogan Pure Michigan.

Shepler said he always knew the pipelines existed — his family used to sell postcards of their construction in the ferry gift shop — but he never really pondered their significance until the Kalamazoo disaster.

Now the third-generation ferry operator can’t stop thinking about the need to shut down the lines, even though he acknowledges Enbridge is working harder to keep a spill from happening.

“I know they’ve upped their game and I thank them for doing that, but there is going to be a time when that thing is not working anymore,” he said. “So do we wait to see something happen?”

Shepler knows he is in a precarious spot, criticizing a business that supplies a product that his own business cannot survive without.

“Our boats need diesel,” he said on a hot July afternoon, a time of year when his fleet may ferry 3,000 to 4,000 people out to Mackinac Island each day. “I know that, but I also know there are other ways to get that oil to refineries than going under the world’s largest freshwater basin.”

Dennis Mikus, a 58-year-old owner of a hardware store in Mackinaw City, on the other side of the Mackinac Bridge from St. Ignace, is less convinced than both plumber Belonga and ferry operator Shepler.

From W.W. Norton & Co. The Great Lakes hold 20% of the world’s freshwater, and they provide food, work and weekend fun for tens of millions of Americans. Yet they are under threat as never before.

In a work of narrative reporting in the vein of Rachel Carson and Elizabeth Kolbert, prize-winning reporter Dan Egan delivers an eye-opening portrait of our nation’s greatest natural resource as it faces ecological calamity. He tells the story of the St. Lawrence Seaway and the Chicago ship canal — good ideas in their time that have had horrendous consequences. He explains how invasive species such as Asian carp, sea lamprey, and zebra mussels have decimated native species and endanger the entire United States. And he examines new risks, such as unsafe drinking water, the threat of water diversions, and “dead zones” that cover hundreds of square miles of water—while showing how the Great Lakes can be restored and preserved for generations to come.

Learn more about the book | Buy the book on Amazon

From W.W. Norton & Co. The Great Lakes hold 20% of the world’s freshwater, and they provide food, work and weekend fun for tens of millions of Americans. Yet they are under threat as never before.

In a work of narrative reporting in the vein of Rachel Carson and Elizabeth Kolbert, prize-winning reporter Dan Egan delivers an eye-opening portrait of our nation’s greatest natural resource as it faces ecological calamity. He tells the story of the St. Lawrence Seaway and the Chicago ship canal — good ideas in their time that have had horrendous consequences. He explains how invasive species such as Asian carp, sea lamprey, and zebra mussels have decimated native species and endanger the entire United States. And he examines new risks, such as unsafe drinking water, the threat of water diversions, and “dead zones” that cover hundreds of square miles of water—while showing how the Great Lakes can be restored and preserved for generations to come.

Learn more about the book | Buy the book on Amazon

When asked what he thinks about the pipeline, Mikus reached into a garbage can next to his cash register and pulled out a stack of blue pamphlets opposing the pipelines. They were in his store because he took them from a friend as a favor, but after a few weeks of keeping them stashed under his cash register he decided to toss them.

“I don’t have Trump posters and I don’t have Hillary posters,” he said last summer. “I’m not in business to sell political viewpoints. I’m trying to sell hardware, but I do have mixed feelings about this.”

Mikus figures there needs to be an alternative to Line 5. Until he sees that plan, he’s not willing to say plug the pipeline.

“I’d rather see Pipeline 5 go away, “ he said, “but I also realize it can’t go away right now.”

His cashier Don Heukels was even more circumspect.

“I have no opinion,” he said. “As long as it doesn’t break."

Dan Egan is a reporter covering the Great Lakes. His reporting on invasive species and other issues has won numerous awards. He is a two-time Pulitzer Prize finalist for explanatory reporting, in 2010 and 2013.