Michigan regulator approves Great Lakes tunnel plan for Enbridge Line 5

The Michigan Public Service Commission has approved an application by Enbridge Inc. to replace its Line 5 dual pipeline segments on the lakebed of the Straits of Mackinac with a single line that would be built in a tunnel beneath the straits.

The Public Service Commission added some conditions for additional safety but generally agreed with the company that there was a public need for the pipeline and its crude oil and propane despite the opposition of environmental activists, some Indian tribal groups, and the state’s governor.

The commission issued a statement saying it “determined there is a public need for the replacement section of Line 5 and the products it carries, finding that without the pipeline’s operation, suppliers would need to use higher-risk and costlier alternative fuel supply sources and transportation for Michigan customers.”

The commission found that “other modes of transporting Line 5’s products, such as by truck, rail, oil tanker, or barges, likely would increase environmental impairment and increase the risk of spills that could significantly harm the Great Lakes and its environment,” which meant “there are no feasible and prudent alternatives to the replacement project.”

The tunnel plan will virtually eliminate the risk of anchor strikes, the commission noted. The existing lakebed dual lines have been hit by an anchor, though they did not rupture. The tunnel also can serve as a secondary containment vessel if a leak develops, the commission said.

The three-person commission approved the tunnel plan on a 2-0 vote with one commissioner abstaining because she had only recently joined the commission.

Line 5 is a 30-in. OD pipeline that has operated for about 70 years. It carries about 540,000 b/d of crude oil and propane from Superior, Wisc., through the Upper Peninsula of Michigan then south through the state to a crossing into Ontario. It serves refineries in Michigan, Ohio, Pennsylvania, Ontario, and Quebec, and its propane is used for home heating in Michigan.

The project still needs an environmental impact statement (EIS) from the US Army Corps of Engineers before it can proceed. The corps has said the EIS will not be completed until early 2025 (OGJ Online, Mar. 24, 2023). The Public Service Commission also said the plan needs an approval by the Mackinac Straits Corridor Authority. There also are pending lawsuits against the plan.

The tunnel would be drilled through bedrock 60-370 ft beneath the lakebed. It would be lined with concrete and would have an inside diameter of 21 ft, with space for the 30-in. Line 5 replacement segment in addition to ventilation systems, leak detectors, dewatering equipment, and equipment needed for inspections and maintenance.