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Federal pipeline regulators have authorized Enbridge Energy to restore maximum pressure to segments of Line 5 beneath the Straits of Mackinac.

The fuel pipeline had been under a pressure restriction since an anchor strike April 1 severed two underwater transmission lines and dented the east and west spans of Line 5.  

The federal Pipeline and Hazardous Materials Safety Administration allowed Enbridge to restore the pipelines’ max pressure of 600 pounds per square inch last week after the company fitted composite sleeves over the dented sections, the Michigan Department of Environmental Quality reported Monday to the state’s Pipeline Safety Advisory Board.

“The max pressure limit is back to where it was, but we don’t operate at that pressure anyway,” Enbridge Spokesman Ryan Duffy said. “We still are at 150 to 200 psi day-to-day in the straits.”

Line 5 includes twin 20-inch structures and carries about 23 million gallons of oil and liquid natural gas a day from western Canada to eastern Canada. Environmental activists have long called for a Line 5 shutdown, warning an accident like the 2010 oil spill in the Kalamazoo River could devastate the Great Lakes.

The April 1 anchor strike released roughly 600 gallons of dielectric fluid, a type of mineral oil, from utility lines owned by Pewaukee, Wisconsin-based American Transmission Company.

Michigan Attorney General Bill Schuette filed suit against Escanaba-based VanEnkevort Tug and Barge Inc. in April, claiming its tug was responsible for the alleged anchor strike that ruptured the ATC lines.

The U.S. Coast Guard has not yet released a report regarding its investigation into the cause of the rupture.

Joseph Haas, Gaylord district supervisor with the DEQ, told board members Monday that some ships, while navigating narrow channels, will lower their anchor slightly to ensure it can be deployed quickly if necessary.

“From what I heard this ship did that and at some point in time the anchor must have been dropped down and not retracted,” Haas said.

eleblanc@detroitnews.com

(517) 371-3661

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