What Enbridge Really Knows About the Risk of a Line 5 Rupture in the Straits of Mackinac

“Safety. It’s a core value that makes us Enbridge. It’s our way of life.”
Enbridge, Our Commitment


Universally considered among the most vulnerable, at-risk pipelines in the world, the 4-mile segment of Line 5 crossing the Straits of Mackinac, where Lake Michigan and Lake Huron meet, is quite literally, an accident waiting to happen.

Line 5: America’s Most Dangerous Pipeline

Owned and operated by Canadian corporation Enbridge, the 71-year-old dual pipelines known as Line 5 no longer rest on the lakebed floor as the original engineers in the early 1950s had planned. Due to massive erosion and lakebed scouring from the strong lake currents, Line 5 is now haphazardly tethered and suspended above the bottom of the Straits of Mackinac by more than 200 supports added over time.

And yet every day, this high-wire act moves 23 million gallons of oil and natural gas liquids through the water. Given the extraordinary currents in the Straits, the structural integrity of the now-elevated pipelines is a continuing concern, second only to the ever-present risk of an anchor strike from a passing ship rupturing one or both of the pipelines.

The chasm between Enbridge’s public statements regarding its pipeline safety measures and Enbridge’s internal understanding of the actual risk of Line 5 failing catastrophically should alarm everyone in the Great Lakes region.

Like the oil industry concealing its long-held understanding of the climate effects of fossil fuel combustion, or the denials of the tobacco companies regarding the cancer risks from smoking, Enbridge has deceived the public by underplaying its internal findings that Line 5 could rupture at any time.

In its public statements, Enbridge assures the public that everything is fine. But Enbridge’s internal assessment of the risk of a catastrophic oil spill from a Line 5 failure is at odds with its PR statements. And its commitment to safety appears as porous as its pipelines.

The Anchor Strike Threat: Immediate, Incontrovertible, and Fully Acknowledged by Enbridge

Shipping on the Great Lakes accounts for nearly 40% of total cross-border trade between the US and Canada, and the Straits of Mackinac are one of the busiest shipping lanes in the region. Each year, hundreds of cargo vessels – some measuring 1,000 feet and carrying as much as 70,000 tons of cargo – pass through the turbulent 5-mile wide strait, and directly over Line 5.

In 2015, Dynamic Risk Assessment Systems, Inc. conducted a comprehensive risk analysis of the Straits pipelines. The analysis found that the risk of a pipeline-anchor incident depends largely on four “vulnerability factors”:

  1. size of the pipeline;
  2. water depth (relative to anchor chain length);
  3. pipeline protection (depth of burial, use of armoring material); and
  4. number and size distribution of ship crossings per unit of time.

The report found that the Line 5 pipelines scored high on all four risk factors:

“[I]t must be noted that with respect to the above vulnerability factors, the Straits Crossing segments cross a busy shipping lane…They are also situated in water that is shallow, relative to the anchor chain lengths of most cargo vessels. Furthermore, a 20-in. diameter pipeline is small enough to fit between the shank and flukes [emphasis added] of a stockless anchor for a large cargo vessel, and thus, is physically capable of being hooked.”

[Illustration of the approximate size of a Great Lakes freighter anchor relative to Line 5. Click to enlarge.]

The Dynamic Risk report concluded that the chance of a pipeline rupture caused by an anchor strike in the Straits within the next 35 years is one in sixty. Those are the same odds that the average person has of being involved in a traffic accident this year.

In a 2018 Enbridge commissioned report, Enbridge acknowledged the threat of an anchor strike in the section titled: Potential Impacts of Anchor Drops and Drags.

“Dragging of an anchor across an unburied pipeline may result in impact, pull-over or, less frequently, a hooking interaction with the pipeline. A large-diameter pipeline could safely resist the pull-over anchor loads of small vessels, but anchor loads of larger vessels could potentially pull the pipeline beyond its bending capacity [emphasis added]. If an anchor is dragging along the lakebed and is not pulled over the pipeline, it could be hooked under the pipeline.” (p. 21)

Predictably, Line 5 has been struck by at least three anchor strikes or cable drags in the last 5 years – even with heightened scrutiny – that have damaged the pipelines or severed nearby transmission cables.

Documented Anchor Strikes on Line 5

In April 2018, the tug Clyde S. Van Enkevort in articulated combination with the barge Erie Trader, dragged an anchor and chain over both Line 5 pipelines. The large anchor, weighing 12,000 pounds, dented the pipelines and easily could have ruptured either the eastern or western pipeline had the anchor’s fluke caught a pipeline. The same incident severed electrical cables in the Straits close to Line 5, releasing approximately 800 gallons of dielectric fluid into the Straits that the Coast Guard never recovered.

Enbridge sued the owner of the tug Van Enkevort. In its complaint, Enbridge’s attorneys asserted that “a reasonable vessel operator would be cognizant of the potential for severe harm to the Great Lakes should any of the pipelines and cables in the Straits of Mackinac be struck by an anchor…” [emphasis added].

In other words, Enbridge is fully aware of the dangers of running fossil fuel pipelines through the open waters of the Straits of Mackinac, and the environmental disaster that could occur.

Later inspections in May and June 2020 revealed extensive new damage to the coatings and surface of both east and west pipelines. Enbridge’s internal investigation revealed that a ship under contract to Enbridge likely dragged a cable that became entangled with a pipeline support, damaging both the support and the pipeline.

In June 2020, following the discovery of the damage and Enbridge’s admitted failure to fully notify the State of Michigan as it is required to do, Michigan Circuit Court Judge James Jamo ordered a temporary shutdown of the pipeline, writing that the risk of harm to the Great Lakes would be “not only substantial but also in some respects irreparable.”

In July 2021, another 15,000-pound anchor lost by an Enbridge-contracted vessel was found on the lakebed between the two Line 5 pipelines. Larger than the Van Enkevort anchor, if the flukes had caught either of the pipelines, disaster would have ensued.

Pipeline breaches by anchor strikes are not uncommon. The Associated Press reviewed more than 10,000 reports submitted to federal regulators and found at least 17 pipeline accidents linked to anchor strikes from 1986-2020. Federal agencies report 22 pipeline accidents in the period 1979 through 2021, all of which resulted in the release of oil.

Anchor strikes are, unfortunately, all too frequent–and the Line 5 pipelines are uniquely vulnerable.

Anchor Deployments in the Great Lakes

The Coast Guard’s realization of the apparent danger of anchor strikes and cable drags in the Straits resulted in the promulgation of a rule establishing a Regulated Navigation Area (RNA) that restricts anchoring in the area proximate to the pipelines. The RNA, however, specifically allows anchoring in the event of an emergency. A ship may deploy an anchor to protect the ship and crew in the event of a loss of power or steerage, or in the event of a collision, grounding, explosions, fires, or heavy weather.

The unfortunate reality is that vessels on the Great Lakes can lose propulsion or steerage within areas designated a “no anchor” zone.

A recent review of U.S. Coast Guard records by the Detroit News revealed that freighters on the Great Lakes lost steerage, propulsion, or electrical power more than 200 times between 2012 and 2022. When such an emergency occurs, a ship captain’s first responsibility is to protect the vessel from damage and ensure the safety of the crew by deploying anchorage.

That is precisely why the dual pipelines in the Straits are uniquely vulnerable to anchor strikes and catastrophic rupture – as affirmed by Enbridge itself. The record of the last five years alone is one of repeated anchor strikes, cable drags, and detached anchors discovered lying near the pipelines.

To justify the continued operation of Line 5 in the Straits, Enbridge touts a “suite of extra safety measures at the Line 5 Straits crossing.” They include the establishment of the Enbridge Straits Maritime Operations Center (ESMOC), the “nerve center” of the marine traffic safety system put in place by Enbridge in the Straits that ostensibly warns ships of the danger of anchoring in the Straits.

But the ESMOC has a loophole you could sail a freighter through: it can only operate as intended 1) in daylight, and 2) if weather conditions permit. But even if it operates as intended, a ship will almost certainly throw an anchor in the event of an emergency loss of power or steerage – which happens on average 20 times per year in the Great Lakes.

Only by sheer luck has the Great Lakes region avoided a multibillion-dollar economic and environmental catastrophe.

Enbridge’s calamitous safety record

Enbridge is responsible for the most destructive pipeline rupture in United States history. The July 2010 failure near Marshall, Michigan released more than 1 million gallons of diluted bitumen (known as “dilbit”) into a direct tributary of the Kalamazoo River. The rupture of Line 6B resulted in devastating impacts to human health and the environment. The Michigan Department of Community Health identified 320 individuals experiencing acute adverse health effects.

The NTSB’s accident report documented how malfeasance and mismanagement exacerbated the pipeline failure, resulting in pervasive contamination and massive ecological damage to the waters and surrounding wetlands from the oil that flowed from Marshall Creek and contaminated a 40-mile stretch of the Kalamazoo River.

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The NTSB concluded that “the rupture and prolonged release were made possible by pervasive organizational failures at Enbridge. [emphasis added]” According to then NTSB Chairman Deborah Hersman, “The investigation identified a complete breakdown of safety at Enbridge.” “Their employees performed like Keystone Kops and failed to recognize their pipeline had ruptured and continued to pump crude into the environment. Despite multiple alarms and a loss of pressure in the pipeline…they failed to follow their own shutdown procedures.”Since the Kalamazoo disaster, Enbridge has claimed a renewed ethic of responsible oversight and commitment, stating that the “safety of the public and the environment, and the operational reliability of our systems will always be our Number One priority.” Sued by the Environmental Protection Agency over the catastrophe, Enbridge entered into a consent decree in 2017 where it agreed to undertake a suite of pipeline monitoring and preventative measures aimed at reducing the likelihood of future pipeline failures. Enbridge paid over $177M in a settlement with the U.S. Department of Justice for the Kalamazoo disaster.

While Enbridge makes much of its new safety-first principles, the record indicates a pattern of systemic noncompliance with the terms and conditions of the 2017 consent decree. Since Enbridge entered the agreement with the federal government, the United States has assessed stipulated penalties for allegedly violating the inspection requirements and other terms of the consent decree, indicating that Enbridge has repeatedly failed to implement required safety measures in a timely manner.

In total, the United States has assessed Enbridge with penalties of $16,462,000 for failing to live up to its commitments and responsibilities under the 2017 consent decree.

Even after the most consequential pipeline disaster in U.S. history that, according to Enbridge, led to sweeping safety reforms throughout the company, Enbridge was penalized six times by the United States for failing to live up to its commitments on safety.

Line 5 must be shut down now

The incident history of the Enbridge pipeline system reveals a pattern and practice of negligence and willful indifference to the strict requirements of federal pipeline safety regulations. Enbridge’s safety record speaks for itself. Data from the Pipeline and Hazardous Materials Safety Administration (PHMSA) indicate that the U.S. segments of Enbridge’s pipeline network experienced 215 hazardous liquids “incidents” from 2002 to August 2018 – an average of one every twenty-eight days. Line 5 alone has experienced at least thirty-three reportable leaks and spills since its installation.

There is overwhelming evidence that the dual underwater pipelines crossing the Straits of Mackinac are particularly vulnerable to catastrophic ruptures and could fail at any time – a possibility acknowledged and affirmed by Enbridge itself. As Enbridge has asserted in its pleadings in the Van Enkevort litigation, the elevated pipelines are clearly vulnerable to anchor strikes and cable drags that could result in the catastrophic failure of the pipelines at the center of the most sensitive and valuable fresh surface water system in the world.

Enbridge knows that anchor drags and strikes have occurred in the Straits of Mackinac.

Enbridge knows that Line 5 is uniquely vulnerable to anchor strikes.

Enbridge knows its warning system is half-baked.

Enbridge knows that an oil spill in the Straits would be catastrophic.

Enbridge knows that today could be the day.

And Enbridge knows it makes a whole lot of money sending fossil fuels through pipes – and through our Great Lakes.

Enbridge continues to violate inspection and monitoring agreements, safety standards, and regulations. It has breached the terms of easement granted by the State of Michigan for the operation of Line 5, defied a lawful Notice of Revocation and Termination of the easement from the Governor of the State of Michigan to cease operation of the pipelines crossing the Straits of Mackinac. And it benefits from a continuing trespass on the sovereign lands of the Bad River Band in northern Wisconsin.

Enbridge’s defiance is a lethal combination of greed, arrogance, and a breach of corporate and civic responsibility. The continued operation of Line 5 must end now.

Take Action:

Email your Michigan representatives in Lansing

4 comments on “What Enbridge Really Knows About the Risk of a Line 5 Rupture in the Straits of Mackinac

  1. Pete Brown on

    The more I learn about both the vulnerability of Line 5 and Enbridge’s lack of safety measures, the more horrified and angry I become! Surely there must be some means, other than protracted legal wangling, of getting the line shut down!! Particularly with respect to the very minimal impact on fuel prices that would be the result, as reported by Enbridge’s own studies!

  2. leonard page on

    In the Bad River Band eviction case in federal court seeking to remove line 5 from its reservation in Wisconsin after Enbridge easements expired in 2013, Enbridge expert Neil Earnest filed a report stating that the price of a gallon of gasoline in Wisconsin and Michigan would go up by half a cent a gallon. In June 2023, Judge Connelly orderd Enbridge to remove line 5 from the tribe’s reservation by June 2026. case is currently pending at 7th circuit court of appeals in Chicago.

  3. Robert Rowley on

    23 million gallons a day amounts to just short of 16 thousand gallons per minute that could spill in the event of a rupture of line 5. Considering the response time it would require to shut the pipeline down the impact of such a spill would be disastrous for the great lakes and surrounding communities. Also considering the Penzance for major oil companies to use dispersants with unknown chemical compounds to break up and sink large oil spills that effectively disperse the oil throughout the water column the environmental consequences would far exceed that of the immediate impact of the spill should such an event occur.


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