Enbridge pipeline damaged in Michigan

Electric cabling company American Transmission Co. said in early April that two of its submarine cables that send power between both Michigan peninsulas were apparently damaged by a passing vessel. Around 600 gallons of a coolant fluid leaked from the cables into the narrow strait between Lake Huron and Lake Michigan as a result.

Enbridge operates a broad network of pipelines that send Canadian oil through the region and Line 5 of that system runs through the same narrow strait. The company said it took "immediate" action after learning of the damage to the submarine power lines and later confirmed three dents on Line 5.

"A review of all leak detection systems and available data indicates that the structural integrity of the pipelines has not been compromised," the company stated late Wednesday.

Line 5 is part of a broader network of pipelines and can carry as much as 540,000 barrels of oil per day. Under agreements with the state, the company needs to conduct a study on the feasibility of building a new system in the Straits of Mackinac and ways to mitigate risk.

Michigan agencies last year expressed concerned with gaps in the protective coating on parts of Line 5 in the straits, at least one of which was caused when Enbridge installed new supportive anchors. Recent inspections revealed dozens of gaps across the span of the pipeline.

In December, waves as high as 9 feet were recorded in the Straits of Mackinac and an agreement with the state meant Enbridge had to shut the line down. Line 6b, part of the same regional network, ruptured in southern Michigan in 2010, leading to one of the worst inland oil spills in the history of the industry.

The U.S. Coast Guard and the federal Pipeline and Hazardous Material Safety Administration are investigating the incident in the straits.