June 30, 2025
Traverse City, Mich. – Today, Flow Water Advocates, a Great Lakes water protection organization, with sign-on from the Sierra Club Environmental Law Program and Surfrider Foundation, submitted written comments on the U.S. Army Corps of Engineers’ Draft Environmental Impact Statement (DEIS) for Enbridge’s proposed Line 5 tunnel project.
The Canadian pipeline company Enbridge proposes building a tunnel under the Straits of Mackinac to house a replacement segment of the Line 5 pipeline, with the stated intention of continuing to transport fossil fuels under the Great Lakes bottomlands for another 99 years.
Enbridge’s application for federal Clean Water Act and Rivers and Harbors Act permits for the project is currently under review by the Army Corps. Project proposals that involve a major federal action that could significantly affect the quality of the human environment must be reviewed by the permitting agency and the public through a process outlined under the National Environmental Protection Act (NEPA). This review includes the preparation of both a Draft and Final Environmental Impact Statement, which must assess the purpose and need for the proposed project, alternatives to the proposal, and an assessment of the environmental consequences of the project.
Flow’s comments highlight a number of serious gaps in the scope and substance of the Corps’ review, including failure to consider alternatives that do not involve pumping oil through the Straits of Mackinac, and a failure to require a more in-depth study of the geology, despite several red flags raised in earlier investigations.
Underground tunnel projects present unique and significant engineering challenges. Risks associated with underwater tunnel construction – such as blowouts and sinkholes – are compounded by the fact that the proposed tunnel would be constructed through fractured rock formations that have been described by studies as “very poor,” with voids that must be filled, anticipated water infiltration in the tunnel, and high methane levels – a potential source of explosions. The tunnel would be constructed as the 72-year-old dual pipelines continue to move 540,000 barrels of oil per day across the lake bottom above. This oil pipeline will run through the heart of the Great Lakes system that supplies over 40 million people with drinking water and contains approximately 84% of North America’s surface freshwater. It is imperative that permitting agencies rigorously review the hydrogeology and engineering plan.
The project is unprecedented and ill-advised. It is hard to imagine a project that would present greater risks of adverse environmental impacts than the proposed tunnel, and the two other alternatives considered in the Corps’ review both involve continued operation of the pipelines. Yet, not only has the Corps failed to properly assess and consider the risks associated with the reviewed alternatives, the Agency has unlawfully excluded from its consideration alternatives that do not involve a pipeline through the Straits. As a result, any final decision short of a permit denial will be unlawful.
The Corps has stated that it anticipates finalizing the EIS for the project in the fall of this year When the Final EIS is published, the public will have the opportunity to provide further comment before the Agency issues its Record of Decision on the project. Flow will continue to participate in the permit review process and express its opposition to this dangerous project, which presents unacceptable and unnecessary risks to our shared public trust resources.
