DETROIT, MI — The U.S. Army Corps of Engineers says environmental risks from building an Enbridge oil pipeline tunnel under the Straits of Mackinac are tied largely to its construction after the agency eliminated any consideration of climate impacts posed by building more fossil fuel infrastructure from its long-awaited environmental review.

Climate risks posed by greenhouse emissions from petroleum products delivered via the proposed tunnel were dropped from a draft Environmental Impact Statement the Army Corp released on Friday, May 30 — rescissions that document footnotes cite as based on executive orders from President Donald Trump.

The review, which began in 2020 under the Biden administration, was fast-tracked this year under truncated timetable for “emergency” energy permitting. The draft review will be finalized this fall before a potential construction permit is issued.

Beyond short-term construction risks, the Army Corps said environmental impacts from a 3.6-mile tunnel that Canadian pipeline giant Enbridge wants to bore under Lake Michigan next to the Mackinac Bridge largely relate to the loss of coastal wetlands and unavoidable destruction within an indigenous tribal archeological district.

“Most other environmental consequences would be short-term with the effects resolving once construction is completed,” stated the Army Corps. Those impacts include local noise and vibration disturbances and the release of drilling fluid to the straits.

If built, the $1 billion estimated tunnel would house a rebuilt section of Enbridge’s Line 5 pipeline, which runs from northern Wisconsin to Ontario by way to Michigan.

The chance of an oil spill into the Great Lakes — a major escalating concern over the past 15 years since the 2010 Enbridge Kalamazoo River spill — drops to “virtually zero” if the pipeline is encased within a utility tunnel, the document states.

Additionally, “failure of the tunnel whether via a collapse or explosion during construction is not reasonably foreseeable,” the Army Corps concluded.

The Army Corps evaluated the project against alternatives such as leaving the existing dual pipelines in place or covering them with rock and gravel to reduce vulnerably to anchor strikes.

The Army Corps found that the overall necessity for the tunnel and the products it would move are supported for the “foreseeable future,” based on increased energy demand and a hotly disputed Trump order declaring a domestic energy “emergency.”

Project opponents have argued that state permits and approvals for the tunnel undermine Michigan’s clean energy goals by investing in fossil fuel infrastructure that will contribute to climate-warming emissions.

The agency has scheduled online public meetings for June 18 and 25, and will accept public comments until June 30.

Enbridge called the draft review a “significant milestone.”

“We appreciate the extensive technical work that went into this document and the opportunity to contribute detailed responses to numerous data and information requests — demonstrating our commitment to transparency and environmental, social and cultural responsibility,” said Enbridge spokesperson Ryan Duffy.

“Our goal is to have the smallest possible environmental footprint,” Duffy said.

The Army Corps shortlisted the project this year for expedited permitting under Trump’s directive to boost fossil fuel production through a “national energy emergency“ declaration that’s being litigated by Democratic states, including Michigan.

In April, the Army Corps said it was coordinating the environmental review’s compliance with the National Environmental Policy Act (NEPA) with the White House Council on Environmental Quality (CEQ), which the agency was giving “vast deference.”

Opponents have accused the Trump administration of a “quid-pro-quo” because Enbridge’s pipeline contractor, Barnard Construction, is owned by a Republican donor who gave $1 million to the Trump campaign last year.

In March, six Michigan Indigenous tribes formally withdrew cooperation with the review in objection to the fast-track plans, accusing the Amry Corps of biasing the process in favor of Enbridge going back well into the Biden administration.

Tribes are asking the state Supreme Court to overturn an February appellate ruling which upheld a 2023 state approval for Line 5 to be relocated inside the tunnel.

According to the Army Corps review, tunnel construction and operation would negatively impact a tribal archeological district around the Straits of Mackinac. In 2020, tribal members found possible evidence of Ice Age-era artifacts underwater.

“Activities such as site grading, excavation, fill, and use construction equipment during the duration of construction activities would remove or destroy archaeological resources within the construction footprints,” the Army Corps wrote.

The agency is evaluating cultural impacts under a parallel process and said its findings would be included in a decision.

Enbridge maintains that Line 5 is structurally sound but the company still reached an agreement to build the tunnel during the waning days of former Gov. Rick Snyder’s administration. Republicans passed enabling legislation in 2018 creating the Mackinac Straits Corridor authority to oversee construction and take ownership of the tunnel while they had control of both chambers and the governor’s office.

Business groups, labor unions and other tunnel supporters argue the infrastructure project is needed to alleviate a threat to the Great Lakes from the 71-year-old pipeline, which runs exposed along the lakebed and has been struck by passing ship anchors in recent years. They say Line 5 is needed to maintain energy market stability in the Midwest.

Meanwhile, Michigan Attorney General Dana Nessel remains in litigation with Enbridge over Gov. Gretchen Whitmer’s 2020 order to close the pipeline under the straits.

In January, Nessel’s office argued in court that the 1953 easement authorizing Line 5 to cross the lakebed has been invalid since its inception because it violates the public trust doctrine. Nessel also claims the pipeline’s presence violates the Michigan Environmental Protection Act and constitutes a public nuisance.

An Ingham County judge’s ruling in the case is pending.

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