Michigan’s Department of Natural Resources and its Department of Environment, Great Lakes and Energy approved permits on July 15 for the Great Lakes Tunnel Project, a 4-mile-long structure that would enclose twin oil and gas pipelines that Canadian energy company Enbridge wants to build at the bottom of the Straits of Mackinac.
The latter department had issued a permit in 2021 for the project planned by the energy giant that aims to replace the existing 73-year-old Line 5 dual gas pipeline that crosses the lake bed. The previous permit expired earlier this year as the project has been tied up in complicated legal battles for years at the state and federal level.
The cost of the pipeline was initially estimated at $500 million in 2018, but rose to at least $750 to $800 million by 2022, according to a report by the Canadian Institute for Energy Economics and Financial Analysis. Enbridge spokesman Ryan Duffy declined to provide an updated project cost.
The Department of Environment, Great Lakes and Energy says in a press release that it conducted a 16-month review covering Enbridge’s lowland and wetlands permit applications 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 enhanced wetlands 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-threatened. The agency says Enbridge must maintain topsoil and collect seeds that will be used to restore some of the Houghton Golden Lake and dwarf iris plant populations after construction, clear trees only during the winter months to avoid disturbing bats, and establish construction zones to avoid damaging sensitive plant areas.
Duffy said the Department of Environment, Great Lakes and Energy’s permit renewal is “an important step 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 license conditions issued today to assess any impact on the construction of the tunnel.”
The Michigan League of Conservation Voters says on its website that it condemns the decision by Gov. Gretchen Whitmer (D) and her administration approve tunnel permits.
“Instead of doing everything she can to safeguard the Great Lakes, Governor Whitmer is allowing a Canadian oil company to saddle Michigan taxpayers with billions of dollars in financial responsibility if something goes wrong,” said Lisa Wozniak, CEO and President of the League.
this claims that the proposed tunnel threatens the rights of tribal nations that are protected andafter the Washington Treaty of 1836. “Tribal governments have consistently opposed the project, warning that an oil spill or construction-related damage could irreparably damage sacred waters, fisheries and culturally significant sites,” the league states.
As ENR previously reported, pre-construction of the tunnel began in 2019 when sediment and rock samples were studied to learn about the geology of the straits and inform the design of the tunnel. Arup is the lead design engineer.
Enbridge named a joint venture partnership between two tunneling companies, Barnard Construction Co. i North America civil and construction in 2024 to lead the construction of the tunnel, but it has not yet started
The project will involve the construction of a 500-foot-long TBM entry point on the south side of the strait 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 project’s TBM, with thousands of components, will take three to four months to assemble.
The machine will have to dig through limestone, rock and shale as it lifts 1-foot segments of reinforced concrete lining into place and seals them. The machine will have to move up to 40 feet per day, five days a week. It is planned to build a vertical shaft on the north side of the strait to recover and dismantle the machine.
During construction, saturation divers will be required to perform periodic inspections and maintenance. They will be required to live in pressure chambers on the surface of the water for weeks at a time and the plan is to transport them in a pressurized habitat at the head of the TBM to do their work.
The project still requires other permits and requirements, including a federal permit from the US Army Corps of Engineers.
