Enbridge has picked contractors to build a 4-mile tunnel to house a new segment of the Line 5 oil pipeline under the Straits of Mackinac that connect Lakes Michigan and Huron, according to a press release from the Canadian pipeline giant.
A joint venture made of Bozeman, Montana-headquartered Barnard and Miami-based Civil & Building North America called Mackinac Straits Partners was selected for the project.
The Straits of Mackinac are the short waterways between Michigan’s Upper and Lower peninsulas. The project entails replacing dual oil pipelines that run underwater between the peninsulas with a new, tunnel-encased pipeline.
An Enbridge spokesperson told Michigan NPR affiliate WGVU that the company will not be disclosing the cost of the contract at this time. The overall project cost was originally pegged at $500 million, but that number is likely to rise due to inflation as delays continue.
Enbridge’s 645-mile Line 5 pipeline is part of its Lakehead System, which begins in Superior, Wisconsin, and ends in Sarnia, Canada. Federal approval for the Michigan tunnel, which would be bored into bedrock underwater through the Mackinac Straits, is necessary because the project involves building in and discharging materials into U.S. navigable waters.
The tunnel project came about after an accident in 2010, per Belt Magazine, when 843,000 gallons of heavy crude oil spilled from Enbridge-owned Line 6B into a tributary of the Kalamazoo River. It remains the second-largest inland oil spill in U.S. history, according to the Line 5 environmental impact statement prepared for the U.S. Army Corps of Engineers. The spill sparked more focus on the potential ecological and economic damage that could occur if the Line 5 pipeline running under the Mackinac Straits failed.
Looking ahead
The Line 5 project has seen numerous lawsuits and delays, and construction is still not ready to start.
Enbridge has permits from the state of Michigan but must wait for final approvals from the U.S. Army Corps of Engineers, which indicated it will decide whether to grant the remaining environmental permits by early 2026, according to the company. Both Enbridge and environmental activists opposing the project expressed frustration at the delay.
Another barrier to the project is a lawsuit brought in June 2019 by Michigan Attorney General Dana Nessel, which seeks to void Enbridge’s use of the 1953 Line 5 easement and end its use of the existing pipelines in the Straits. That case is awaiting a decision in the U.S. Sixth Circuit Court of Appeals.
Once the final approvals are in place, the tunnel would take three to four years to build, according to the University of Michigan publication Michigan Engineering News.
