Michigan approved permits for Enbridge's $750M+ Great Lakes Tunnel Project to replace the aging Line 5 pipeline. Environmental groups and tribal nations oppose the project.
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The Michigan Department of Natural Resources and the Department of Environment, Great Lakes, and Energy each approved permits July 15 for the Great Lakes Tunnel Project, a 4-mile structure that would enclose twin oil and gas pipelines Enbridge plans to build along the bottom of the Straits of Mackinac.
The latter department had issued a permit in 2021 for the project, which is intended to replace the existing 73-year-old Line 5 dual pipeline that crosses the lakebed. That previous permit expired earlier this year as the project has been tied up in years-long legal battles at the state and federal levels.
The pipeline cost was originally estimated at $500 million in 2018 but ballooned to at least $750 million to $800 million by 2022, according to a report by the Canada-based Institute for Energy Economics and Financial Analysis. Enbridge spokesperson Ryan Duffy declined to provide an updated project cost.
The Department of Environment, Great Lakes, and Energy said in a press release that it conducted a 16-month review covering Enbridge's bottomlands and wetlands permit application and concluded that "the public and private need for the proposed activity outweighed other public interest criteria."
The permit comes with conditions. Enbridge must submit an improved wetland mitigation plan to address wetland impacts, with new conditions designed to mitigate impacts to cultural resources in the area.
The Department of Natural Resources permit requires Enbridge to reduce impacts on rare plants and animals that are federally and state-listed as threatened. The agency said Enbridge must maintain topsoil and collect seeds to restore part of Houghton's goldenrod and dwarf lake iris plant populations after construction, clear trees only during winter months to avoid disturbing bats, and set construction zones to avoid damaging sensitive plant areas.
Duffy called the Department of Environment, Great Lakes, and Energy renewal of permits "an important step forward for a project designed to further protect the Great Lakes while helping ensure the uninterrupted flow of energy that supports Michigan and the region." He added: "We are reviewing the new permit conditions issued today to assess any impacts on tunnel construction."
The Michigan League of Conservation Vessels said on its website that it condemns the decision by Gov. Gretchen Whitmer and her administration to approve permits for the tunnel.
"Rather than doing everything she can to safeguard the Great Lakes, Gov. Whitmer is enabling a Canadian oil company to saddle Michigan taxpayers with billions of dollars in financial liability if something goes wrong," said League CEO and President Lisa Wozniak.
The group asserted that the proposed tunnel threatens the rights of tribal nations protected under the 1836 Treaty of Washington. "Tribal governments have consistently opposed the project, warning that an oil spill or construction-related damage could irreparably harm sacred waters, fisheries, and culturally significant sites," the league stated.
Preconstruction on the tunnel started in 2019 when samples of sediment and rock were studied to learn about the geology of the straits and to inform the tunnel's design. Arup is lead design engineer.
In 2024, Enbridge named a joint venture between two tunneling companies, Barnard Construction Co. and Civil and Building North America, to lead construction of the tunnel. Work has not started.
The project will entail construction of an entry point for the 500-foot-long tunnel boring machine on the south side of the straits, where there will also be a slurry plant to separate rock, clay, pebbles, and water that will be pumped out of the tunnel. Once separated, the water will be reused in the tunneling process.
The tunnel boring machine, with thousands of components, will take three to four months to assemble. It will excavate through limestone, rock, and shale as it lifts 1-foot segments of reinforced concrete liner into place and seals them. The machine will move up to 40 feet per day, five days a week. A vertical shaft is planned on the north side of the straits for retrieving and dismantling the machine.
During construction, saturation divers will need to perform regular inspections and maintenance. They will live in pressure chambers on the water's surface for weeks at a time and be transported down in a pressurized habitat at the head of the tunnel boring machine.
The project still requires several other permits and requirements, including a federal permit from the U.S. Army Corps of Engineers.
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