Line 5 in the Straits of Mackinac

What is Line 5?

Built in 1953 and designed to last 50 years, the Line 5 pipeline runs from Superior, Wisconsin, across the Upper Peninsula of Michigan, through the open waters of Straits of Mackinac, and across the Lower Peninsula, before crossing under the St. Clair River to refineries in Sarnia, Ontario. The 30-inch-diameter steel pipeline splits into two 20-inch-diameter pipes when crossing the Straits, carrying nearly 23 million gallons of oil and natural gas liquids daily through the turbulent waters where Lake Michigan meets Lake Huron. Line 5 has failed at least 33 times since 1968, spilling at least 1.13 million gallons of oil on land and in wetlands. These 67-year-old Line 5 runs at depths between 100 and 270 feet in the Straits of Mackinac, where it is stressed by strong currents and prone to anchor strikes. Built and operated by Canadian company, Enbridge, Inc., Line 5's products mostly serve Canada, with less than 10 percent of the oil used in Michigan. Line 5 threatens the drinking water supply for 5 million Michigan residents, the Pure Michigan tourist economy, and a way of life. It is time for the state of Michigan to evict Enbridge from the Straits of Mackinac and shut down Line 5 because of the oil spill danger to the Great Lakes.


Map courtesy of Sierra Club

Quick Facts

  • University of Michigan studies call the Mackinac Straits the "worst possible place" for a Great Lakes oil spill, which could pollute up to 720 miles of shoreline along Lake Michigan and Lake Huron.
  • Enbridge's data reveal that sections of Line 5 in the Mackinac Straits are cracked and dented, and a segment on land near the Straits has lost 26% of its original wall thickness.
  • Under the best conditions, only 30% of an oil spill would be recovered.
  • 1.5 million jobs are directly tied in some way to the Great Lakes, generating more than $62 billion in wages. 

Line 5 Webinars

FLOW held two summer 2020 webinars that examined the path forward to shut down Line 5: “Exploring Legal Pathways to Shut Down Line 5 and Stop Oil Tunnel to Protect the Great Lakes” on July 22 and “Securing a Brighter Future Without Line 5 or an Oil Tunnel” on August 5. Watch them below:

FLOW has produced a dynamic and engaging multimedia story map to provide the most current information on the threat from, and solutions to, the decaying Line 5 oil pipelines in the Straits of Mackinac and the proposed oil tunnel under the Great Lakes. Our Line 5 digital story map (see directly below or click here to open in a new tab) includes interactive maps and links to new videos, fact sheets, and more, as well as sections about the history and route of the oil pipelines; the threats they pose; the Public Trust and your rights; tribal concerns; the latest news on shutting down Line 5; alternatives that ought to be pursued; and how you can take action today. The maps are interactive, so click and zoom for more details. Links to videos, photos, websites, and other pop-up images will be highlighted. Click on any tab in the Line 5 story map to learn more about that topic.

Line 5 Storymap: The Legal Fight for Our Public Waters

What's the plan?

Advocates of shutting down dangerous Line 5 at the Straits of Mackinac have presented a detailed plan for its decommissioning.  The plan gives the state officials who are accountable, Attorney General Bill Schuette and Governor Rick Snyder, a detailed, realistic plan for protecting the Great Lakes from a catastrophic oil spill while assuring energy to meet Michigan’s needs.

Enbridge has been using publicly-owned lakebed at the Straits as a conduit for its shipments of oil and gas underneath the Straits under a 65-year-old easement granted by the state on the condition that the company operates prudently.  But repeated disclosures of shoddy maintenance, structural flaws in the pipelines and concealment of critical information from state officials demonstrated Enbridge is not acting prudently.

It’s time to move forward with legal action to compel strict enforcement of the current easement and to set a timetable for ending the easement.

What's the deal?

On November 27, 2017, following the long Thanksgiving holiday, Governor Snyder announced a sweetheart deal with Enbridge to fast track a tunnel alternative under our Great Lakes. Some elements like shutting down Line 5 in adverse weather sound like strong protections on paper. But upon closer reading, it is clear that Line 5 will never be shut down under the agreement’s 8-foot wave standard for a full 60 minutes. It’s not a final deal until September 30, 2018 when the state makes a final decision to replace the pipelines or to shut it down (just in time before our next Governor takes office).

This news came in the wake of Enbridge acting in bad faith and misleading both Michigan and federal officials on the condition of Line 5 for over three years.  We now know that there are at least 48 bare metal spots and/or coating gaps near the 128 total anchor locations on Line 5 in the Straits of Mackinac.

For more information, please visit:

A looming threat to Michigan's economy

A spill from Line 5 at the Straits of Mackinac could deliver a blow of over $6 billion in impacts and natural resource damages to Michigan’s economy, according to a study commissioned by FLOW. Conducted by nationally respected ecological economist Robert Richardson of Michigan State University, the study for the first time adds up potential costs of a Line 5 spill into the Straits of Mackinac and adjoining waters under a realistic – but not worst-case – scenario.  The study estimates $697.5 million in costs for natural resource damages and restoration and more than $5.6 billion in total economic impacts, including:

  • $4.8 billion in economic impacts to the tourism economy; 
  • $61 million in economic impacts to commercial fishing;
  • $233 million in economic impacts to municipal water systems;
  • Over $485 million in economic impacts to coastal property values. 

Enbridge Energy is using the Straits of Mackinac as a convenient shortcut for transporting oil from the Canadian prairies to a Canadian refinery in Sarnia, with precious little of its product benefiting Michigan.  Yet Michigan would absorb the lion’s share of the economic disaster resulting from a spill.

Nancy May

An imminent threat to the Great Lakes

In early April, we dodged a bullet as we watched a hazardous liquid spill from two neighboring transmission cables unfold.  A release of at least 600 gallons of toxic coolant and insulating fluid from electric cables owned by American Transmission Company (ATC) occurred sometime Sunday, April 1 in the Straits of Mackinac.  ATC, however, did not report the release to the Coast Guard for 24 hours. By Monday, ATC officials were blaming “extraordinary circumstances” like ice in the water and near the shore that hindered the emergency response. 

On April 3, Enbridge – owner and operator of Line 5 – temporarily shut down the flow of oil in the pipelines to evaluate leak detection systems. Ten days after the ATC accident, on April 10, Enbridge notified state and federal officials that their pipelines had suffered three dents due to the same vessel that damaged the ATC lines.

A vessel anchor strike to Line 5 was the number one threat that consultant Dynamic Risk identified in its November 2017 alternative report to the Governor Snyder’s Michigan Pipeline Safety Advisory Board.  Ironically, the original Bechtel engineers believed that a vessel anchor strike was only “one chance in a million.”

Well, that one chance in a million became real. 

A Collection of Line 5 Films

Great Lakes, Bad Lines from Colin McCarthy on Vimeo.

FLOW partnered with Patagonia to create the short film Great Lakes, Bad Lines, which takes a first-hand look at the insurmountable threat that Line 5 poses to our waters. Click here to watch at home, or plan a screening.

Straight Talk about Line 5 Through the Straits from rivetentertainment on Vimeo.

This video was produced to point out the failings of the Enbridge Line 5 oil pipeline that runs through 21% of the world's fresh surface water in the middle of the Great Lakes. Produced by Rivet Entertainment

Want to see what Line 5 looks like up close? Watch this three-minute underwater tour courtesy of Dr. Ed Timm.

Immiscible: The Fight Over Line 5 from Immiscible: The Fight Over Line on Vimeo.

Immiscible: The Fight Over Line 5 explores the growing tension between water activists and big oil companies. The film features interviews from leading organizations in the fight to decommission Enbridge Line 5 in the Straits of Mackinac, members of indigenous communities at risk, concerned residents, as well as Enbridge Energy’s public response to this conflict. This film was created by four Michigan State University students (Olivia Dimmer, Daniel Stephens, Austin Torres, & Annette Kim) in the College of Communication Arts & Sciences, Department of Media & Information.


Additional Information

Agreement Undermines Public Involvement and Independent Risk & Alternatives Analysis

For over three years, the Governor has relied on a Task Force and then an Advisory Board he formed to study the risks of and alternatives to operating this pair of 64-year-old oil pipelines in the Straits. Now, just as the studies are nearing completion — and just as new disclosures about Enbridge’s failures were multiplying — the Governor did an end run around that public process and announced the deal.

It is imprudent and arbitrary for the Governor to unilaterally sign a backroom deal with Enbridge before the legal processes and evidence, including the opinion of experts on all sides, has been thoroughly reviewed and completed. Governor Snyder appears to have prematurely ignored and violated his own executive order, law, rules and once more ignored his public trust duties toward the Great Lakes, water, public health and safety, and the protection of citizens.  Moreover, the public and the Governor’s office still do not have a comprehensive study analyzing the risk of Line 5 and its alternatives.

Risks Associated with Building a Tunnel Under the Great Lakes

The deal is biased toward allowing Enbridge to construct a tunnel (via horizontal directional drilling or trenched in secondary containment) to transport petroleum under the Straits, threatening the protection of the Great Lakes and their tributaries for decades to come. Such an agreement undermines the law and our way of life.

Building a tunnel under the Straits cannot be approved under Michigan’s governing law — the Great Lakes Submerged Lands Act — unless Enbridge can demonstrate that there is no likely harm to public waters with an oil spill and that there are no feasible and prudent alternatives. This is a high bar given the alternative to using existing pipeline infrastructure to transport crude oil around the Great Lakes.

Allowing Enbridge to tunnel under the Great Lakes also could unleash a gusher of interest by other oil and gas pipeline companies that could assert — under the North American Free Trade Agreement — their right to bore underneath the Great Lakes too.

A tunnel is no gift to Michiganders. All oil pipelines — even in tunnels — have an inherent risk of spills in their operations due to corrosion, defects in materials, and human error.  Fundamentally, a tunnel does not eliminate the risk to the public trust waters of the Great Lakes because the inland portions of the Line 5 pipeline will still be in operation.  A particularly sensitive location is the 90-mile U.S. 2 corridor, where Line 5 traverses across tributaries that directly feed into Lake Michigan. And the remaining 641 miles of Line 5 remain vulnerable due to their weaker construction (0.281 thick, 30” pipeline), operation, and maintenance.

No Trusting Enbridge

It makes no sense to trust Enbridge to abide by a new agreement when it has been flagrantly violating its existing commitments and attempting to conceal those violations.

This is the same company that brought Michigan the worst inland oil spill in U.S. history and that misled both state and federal authorities for three years about its screw anchors causing bare metal spots on 48 locations along Line 5.

The Governor cannot preordain the tunnel option without Enbridge submitting an application under state law -- the Great Lakes Submerged Lands Act -- and demonstrating that there is no feasible and prudent alternative.

The presumed tunnel option bypasses and prematurely dictates the future of Line 5 and sidelines the three-year process that the Governor set into motion with the creation of the Task Force and the Advisory Board under his executive order.

Enbridge's Easement Violations

FLOW has revealed that Enbridge is operating illegally and has broken its easement agreement with the state and people of Michigan in the following ways:

  1. Standard of Care as a Reasonably Prudent Person (Section A)
  2. Indemnity Provision (Section J)
  3. Pipeline Wall Thickness Provision (Section A (11))
  4. Pipeline Exterior Slats and Coating Requirements (Section A (9))
  5. Pipeline Minimum Curvature Requirement (Section A (4))
  6. Maximum Unsupported Span Provision (Section A (10))
  7. Federal Violation of Emergency Oil Spill Response Plan (Section A)
  8. State Violation under the Michigan Environmental Protection Action (Section A)


Read the Full Report here.

Alternatives Exist

FLOW's December 2015 expert report demonstrates that decommissioning the Line 5 oil pipeline would not disrupt Michigan's or the Midwest's crude oil and propane supply, as only 5-10% of the oil in Line 5 is used in Michigan. Available capacity to meet energy demand in the Great Lakes region already exists in the North American pipeline system. Check out our Alternatives Fact Sheet below for more information.

FLOW and our partners are working together to ensure that the State of Michigan is held accountable as public trustee of our waters to take immediate action to prevent a catastrophic oil spill in the Great Lakes.

Printable Line 5 Fact Sheets

Related Links

Line 5 Fact Sheet

Line 5 Alternatives Fact Sheet

Line 5 Propane Fact Sheet

FLOW Anchor Permit Comments

Appendices for FLOW Comment