Line 5 tunnel would reduce leak risk, create some construction headaches, Army Corps says

Lansing — Federal regulators on Friday released a long-awaited draft study that found that most of the environmental effects resulting from constructing a tunnel to house Line 5 beneath the Straits of Mackinac would be temporary and tied almost exclusively to construction activities.

The tunnel, the study found, would have a “beneficial cumulative effect” on reducing the risk of a crude oil leak from the pipeline.

The draft Environmental Impact Statement released Friday, a report the U.S. Army Corps of Engineers has been working on for nearly five years, analyzed Enbridge’s proposed 3.6-mile tunnel to house a new segment of Line 5 and two other alternatives to the tunnel: Doing nothing and keeping the current dual pipeline in place on the lakebed, or covering exposed portions of the current dual pipeline with gravel and rock.

“The applicant’s preferred alternative,” the report said, referring to the tunnel construction proposal, “would have a beneficial cumulative effect on reduced risks of a petroleum leak in the Straits and, when combined with one of the decommissioning sub-alternatives, improvements to water-based recreation.”

The release of the draft statement launches a 30-day public comment period, the preparation of a final statement, and the expected release of a final record of decision this fall. The decision timeline has been somewhat shortened by President Donald Trump’s declaration of a national energy emergency in January, which speeds up the deliberation process. The approval is one of the last Enbridge needs before it moves forward with tunnel construction; it is also awaiting one other state permit.

Enbridge, in a statement Friday, said the report is an important “milestone” in the project and incorporates extensive survey work generated from more than 40,000 data points.

“Our goal is to have the smallest possible environmental footprint,” said Ryan Duffy, a spokesman for Enbridge. “The tunnel design already reflects that intent, and we will use the USACE’s findings from the DEIS (draft Environmental Impact Statement) to further refine the project.”

The Sierra Club Michigan Chapter in a statement Friday argued Gov. Gretchen Whitmer should “step in” and block the tunnel from moving forward. Whitmer’s legal efforts to close the pipeline have so far been unsuccessful, but her Department of Environment, Great Lakes and Energy currently is assessing a permit request from Enbridge for the tunnel.

“We’ll be digging in the Army Corps’ DEIS (Draft Environmental Impact Statement); however, our position on the tunnel and Line 5 has not changed,” the Sierra Club’s Anne Woiwode said in a statement. “Line 5 remains an existential threat. Chances of an oil spill in the Great Lakes — our most valuable freshwater resource — skyrockets if this tunnel is built in the Straits.”

The U.S. Army Corps of Engineers prepared the environmental impact statement released Thursday as part of its consideration of a permit for the project under the Rivers and Harbors Act of 1899 and the Clean Water Act.

The corps also is analyzing, separate from the EIS, the tunnel construction’s impact to historic properties and its potential impingement on the treaty rights of federally recognized tribes. The corps’ analysis of those factors will be included in the final record of decision expected this fall.

“Public participation is an important part of the National Environmental Policy Act (NEPA) process to ensure a thorough environmental analysis, and an effective, consistent and well-informed decision,” Detroit District Commander Lt. Col. Wallace Bandeff said in a statement Friday.

Overall, the study found construction of the tunnel would have temporary effects on noise, vibration, aesthetics, recreation, some wildlife and geology in the area while the structure is being built. The lasting negative effects, the statement found, were confined to a loss of several acres of vegetation and wetlands due to the buildings that would be constructed at the entrance and exit of the tunnel in Mackinaw City and St. Ignace.

The tunnel, the corps found, would serve as a secondary containment in the event of a leak from the pipeline and would reduce the maintenance and surveillance activities currently required to ensure the safety of the dual pipelines that have been located on the lakebed since the 1960s.

The analysis found there would be a steady or slightly increased need through 2050 for the products transported through the pipeline. Analysts noted that determination was made before the current president lifted restrictions and encouraged domestic energy exploration.

“The USACE determined the current needs for transport of the pipeline products are supported by their existing use, and the need for the pipeline products in the foreseeable future is supported,” the report said.

Failure of the tunnel via a collapse or explosion — concerns raised by some opponents to the plan — “is not reasonably foreseeable,” the report said.

The corps’ analysis of an alternative to the tunnel — that of covering exposed portions of the current pipeline with gravel or rock — found doing so would result in a permanent change in the lakebed. However, the study found, overall, the cumulative detrimental effects would be less under the gravel protective cover alternative than under the proposed tunnel.

But both the gravel protective cover or the continued current placement of the dual pipelines on the lakebed fail to provide a secondary containment method in the event of a leak, the report found.

The report also noted there are drawbacks to keeping the dual pipeline in place as is.

“Maintenance activities would continue to occur,” the report indicated. “As the pipelines age, it is anticipated that additional deterioration could result in some release of metals into the surface water. In addition, the potential for vessel anchor strikes would remain.”

While the likelihood of anchor strikes under both the gravel cover and current arrangement are unlikely, the tunnel plan eliminates the probability completely, the report found.

Under the report issued by the corps, the risk of an anchor strike with the current placement of the dual pipelines is about once every 1,300 years; the potential failure rate of a gravel cover due to an anchor strike is once every 128,000 years.

The pipeline was struck by an anchor in 2018 and, in 2020, was ordered shut down temporarily after an inspection uncovered damage to one of the pipeline’s anchor supports that appeared to indicate something had been dragged across it.

The 2018 anchor strike advanced discussions between then Republican Gov. Rick Snyder and Enbridge, both of whom had been debating extra security measures for the pipeline after a 2010 spill from Enbridge’s Line 6B in Marshall raised concerns about a similar catastrophe involving Line 5’s Straits of Mackinac segment at the intersection of Lakes Michigan and Huron.

Shortly before leaving office in 2018, Snyder entered an agreement with Enbridge in which the company agreed to spend more than $500 million building a tunnel and replacement segment of Line 5 in the Straits of Mackinac.

The agreement and Line 5’s continued operation in the Straits were challenged by Democratic Attorney General Dana Nessel and Whitmer in several different lawsuits. The suits in state and federal court have so far been unsuccessful in closing the line or eliminating the agreement. However, cases still are pending in Ingham County Circuit Court and U.S. District Court regarding the pipeline’s continued operation.

Additionally, a regulatory approval for the tunnel project awarded by the Michigan Public Service Commission has been appealed and is currently awaiting a decision from the Michigan Supreme Court. And the U.S. continues treaty negotiations with Canada after the neighbor to the north in 2021 invoked a never-before-used treaty to protect the pipeline from Michigan’s efforts to close it.

eleblanc@detroitnews.com