The Michigan Public Service Commission has approved a site permit to relocate a segment of Enbridge's Line 5 oil and natural gas pipeline from the lake bed of the Straits of Mackinac to a service tunnel that would be constructed beneath it. The commission voted 2-0 Dec. 1 for the Great Lakes Tunnel project, which is intended to mitigate vulnerability to rupture of the line sitting on the lake bed. 

“We are ready to begin work on this project," Ryan Duffy, a spokesperson for Canada-based Enbridge Energy, said in a statement following the vote. "The only thing standing in the way of locating a replacement section of Line 5 into the tunnel is a decision on our permit application by the U.S. Army Corps of Engineers.” 

A contractor has yet to be selected for the project that will likely start in 2026, pending the environmental impact review by the Corps, Duffy said.

Commission Chair Dan Scripps, who voted for the tunnel, said it is currently the most prudent option for replacing a portion of the dual pipeline that carries 540,000 barrels per day of crude oil from Sarnia, Ontario, Canada, to Superior, Wis., with part of its route running across the straits linking Michigan's upper and lower peninsulas. Enbridge has not yet selected a route for the service tunnel which will run three-and-a-half to five miles between the two peninsulas.

“We find that a concrete-lined tunnel housed deep below, in the bedrock of the lake bed, represents the best option to mitigate the current dangers" the pipeline presents, he said. 

The commission studied other modes of transporting Line 5’s products, such as by truck, rail, oil tanker or barges, and found those methods likely would increase environmental impairment and increase the risk of spills. 

Scripps said an anchor strike, similar to one in 2018 that dented the protective coating outside the pipeline, but did not cause a leak, is the most likely cause of potential damage to the 70-year-old pipeline. 

“Fortunately, the pipeline didn’t rupture in that case, Scripps said. "But there’s no guarantee we’d be so lucky the next time.” 

Nichole Keway Biber, a tribal citizen of the Little Traverse Bay Bands of Odawa, was one of several environmentalists and Native American tribal representatives who attended the meeting. Biber and others want to see the pipeline shut down entirely. 

Echoing Scripps’ concerns, she noted that a transition to a tunnel will take time and that the current pipeline could suffer damage at any moment. 

“It could happen overnight or it could happen a minute from now—the 70-year-old pipeline could rupture or take an anchor strike," she said. 

The pipeline, particularly following the 2018 anchor strike, has had controversy follow it across two Michigan gubernatorial administrations. In 2018, Enbridge agreed to a deal with then-Gov. Rick Snyder (R) to build a straits tunnel to house a new segment of the pipeline. At that point, the tunnel was estimated to cost between $300 million and $650 million.

Current Michigan Go. Gretchen Whitmer (D) attempted to shut the pipeline down via executive order in 2020 but a federal judge, in 2023, denied her order. It was backed by the Native American tribes, mainly from Michigan's upper peninsula, whose neighboring waters are used for fishing by the Ojibwe tribe. The Ojibwe have fishing rights between the straits that are recognized by the federal governments of both the U.S. and Canada. 

U.S. District Judge William Conley said in his ruling that the Bad River Band of Lake Superior Chippewa didn’t prove that an emergency exists along a stretch of the Enbridge Line 5 pipeline and urged the tribes and Gov. Whitmer to work with Enbridge to come to another resolution. A similar effort by Michigan Attorney General Dana Nessel (D) to shut down the pipeline was denied in state court in last year. 

Duffy says Enbridge doesn't have an updated cost estimate for the service tunnel, which would be large enough to allow trucks to pass through for pipeline maintenance, according to the 2018 plan. Enbridge agreed to pay for construction, in the 2018 agreement.

"We  may have an update next year when we hire the construction company," he said.