Enbridge Energy will issue requests for proposals in the coming weeks for contractors to construct a $500-million Great Lakes tunnel to carry crude oil and natural gas liquids through the Straits of Mackinac between Michigan and Ontario. Ryan Duffy, spokesman for the Calgary, Alberta-based energy company, said the RFP process will take about six months.

The announcement comes after the Mackinac Straits Corridor Authority on Feb. 16 concurred with a staff recommendation that Enbridge meets all requirements specified in a 2018 agreement between the firm and the State of Michigan.

Enbridge “is prepared to issue the RFP to select a construction contractor,” Duffy said. The agreement between the state and Enbridge calls for the company to start construction within 180 days of receiving a construction permit from the U.S. Army Corps of Engineers, which is still performing an environmental review.
Construction of the approximately four-mile tunnel is expected to begin no earlier than the first quarter of 2024, with work expected to take at least four years. Arup is the design engineer.

Line 5 ships 540,000 barrels per day of crude oil and refined products from Superior, Wis., to Sarnia, Ontario, via the straits.

The agreement, reached in late 2018 under previous Michigan Gov. Rick Snyder (R), requires the company to build the tunnel beneath the straits to contain a new segment of Line 5. The current 68-year-old twin pipelines stretch along the lake bottom with no protection other than their own coatings. Enbridge concedes that the current pipelines need to be replaced. The deal for the replacement tunnel was passed by the Michigan legislature and signed by Snyder in his last days in office.

Current Gov. Gretchen Whitmer (D) cited safety and environmental concerns as reasons behind her attempt in November 2020 to revoke a permit that allows Enbridge to operate the pipeline.

A federal lawsuit filed in 2020 by Michigan Attorney General Dana Nessel seeking to shut down Line 5 still awaits a hearing.

Lynsey Mukomel, press secretary for Nessel, declined to comment on the lawsuit or on Enbridge moving forward with the RFP process.