Army Corps clears major federal hurdle just 12 days after Michigan’s high court threw out key state approval
MACKINAW CITY — Just 12 days after the Michigan Supreme Court threw out a key state permit for Enbridge’s controversial Line 5 tunnel, the project has received a major green light from the federal government.
The U.S. Army Corps of Engineers on Aug. 12 issued Enbridge a federal permit authorizing regulated construction activities associated with the proposed Great Lakes Tunnel beneath the Straits of Mackinac.
The decision removes one of the biggest federal regulatory obstacles facing the nearly decade-old project, which would move a section of the existing Line 5 petroleum pipeline from the bottom of the Straits into a concrete-lined tunnel bored through bedrock beneath the lakebed.
But it does not mean construction is about to begin.
On July 31, the Michigan Supreme Court voted 6-1 to vacate a critical 2023 Michigan Public Service Commission approval for the project and ordered state regulators to reconsider the tunnel’s environmental consequences.
That leaves Line 5 in an unusual position:
The federal government has cleared a major hurdle for the tunnel while Michigan’s highest court has ordered state regulators to take another look.
Army Corps Gives Line 5 Federal Approval
The Army Corps’ Detroit District issued an individual permit authorizing federally regulated activities associated with construction of the approximately four-mile tunnel.
The project calls for boring a roughly 21-foot-diameter tunnel beneath the Straits that would contain a new 30-inch Line 5 pipeline segment, replacing the two existing pipelines that currently sit on the lakebed.
The Army Corps said its review complied with federal requirements including the National Environmental Policy Act, Clean Water Act, Rivers and Harbors Act, Endangered Species Act and National Historic Preservation Act, as well as federal Tribal trust responsibilities.
The agency concluded that issuing the permit was not contrary to the public interest.
The Corps’ authority, however, is limited.
Its permit authorizes Enbridge to perform work in federally regulated waters. The Army Corps does not regulate the design or operation of the pipeline itself or the petroleum products transported through it.
Enbridge called the federal approval a significant milestone following more than six years of review.
Trump Administration Calls Line 5 Critical Infrastructure
The approval also reflects the Trump administration’s push to accelerate major energy and infrastructure projects.
Assistant Secretary of the Army for Civil Works Adam Telle linked the decision to President Donald Trump’s energy policies, saying the administration is attempting to reduce regulatory delays surrounding critical infrastructure.
That puts the Michigan Line 5 fight into a much larger national debate over energy security, infrastructure permitting and continued reliance on petroleum.
The federal government’s decision, however, arrives less than two weeks after Michigan’s highest court moved in the opposite direction.
Michigan Supreme Court Ordered New Review
On July 31, the Michigan Supreme Court vacated the Michigan Public Service Commission’s December 2023 approval of the tunnel project.
In its 6-1 decision, the court concluded the commission’s review was too narrow and ordered regulators to more fully assess potential environmental harms associated with the project.
The ruling sends the case back to the MPSC.
That means the Army Corps’ approval represents a major federal victory for Enbridge, but it does not resolve the project’s state regulatory problems.
Other litigation also remains pending.
Why Line 5 Matters To Michigan
Line 5 has operated since 1953 and runs approximately 645 miles from Superior, Wisconsin, across Michigan’s Upper and Lower Peninsulas before reaching Sarnia, Ontario.
The pipeline can transport about 540,000 barrels — roughly 22.7 million gallons — of crude oil and natural-gas liquids per day.
Those products feed regional refineries and help supply propane to Michigan.
Enbridge says Line 5 supplies approximately 65% of the propane used in Michigan’s Upper Peninsula and 55% of statewide propane demand.
Those company estimates have been disputed by pipeline opponents, but there is little disagreement that Line 5 is a significant component of the regional petroleum transportation system.
Supporters argue shutting it down without sufficient replacement capacity could increase transportation costs, disrupt energy supplies and potentially raise prices for consumers.
Opponents argue those economic benefits don’t justify continuing to transport petroleum through one of the world’s most important freshwater systems.
Tribal Nations Remain Strongly Opposed
Native American opposition also remains a significant obstacle.
Several Michigan Tribal Nations have challenged the tunnel project, arguing that Line 5 threatens the Great Lakes environment, culturally significant areas and treaty-protected fishing rights.
Four Tribal Nations participated in the legal challenge that resulted in the Michigan Supreme Court vacating the MPSC permit.
The Army Corps said its federal review included consideration of Tribal concerns and federal Tribal trust responsibilities.
The Corps ultimately concluded that issuing the permit would not impermissibly impair Tribal treaty rights.
Tribal opponents strongly disagree and have indicated the federal decision could face another legal challenge.
Why Enbridge Wants The Tunnel
The controversy is complicated by the condition and location of the existing Line 5 crossing.
Two sections of the 73-year-old pipeline currently sit on the bottom of the Straits of Mackinac.
Enbridge argues putting a replacement pipeline inside a tunnel beneath the lakebed would dramatically reduce the possibility of damage from anchors, vessels and other external forces.
An anchor strike in 2018 damaged Line 5 and nearby underwater infrastructure, highlighting the vulnerability of infrastructure exposed on the lakebed.
Opponents contend the better solution is shutting down the Straits crossing entirely rather than building infrastructure that could keep Line 5 operating for decades.
What Happens Next?
The Aug. 12 Army Corps permit removes one of the largest federal regulatory obstacles facing the project.
But significant uncertainty remains.
The Michigan Public Service Commission must reconsider its approval following the July 31 Supreme Court decision.
State and federal litigation remains unresolved.
And environmental organizations and Tribal opponents are expected to continue fighting the federal approval.
That means Enbridge has won an important federal victory — but Michigan’s long-running Line 5 battle is far from finished.
Meanwhile, the existing Line 5 pipelines continue operating on the bottom of the Straits while the legal battle over their proposed replacement continues.
