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What is the condition of the oil pipeline in the Straits of Mackinac? Answers can be hard to find.

Mark Brush
Michigan Radio
Tom Prew, a region engineer for Enbridge, on the deck of the work barge on the Straits of Mackinac. Brackets for the pipeline sit on the deck.

A lot of us are curious about the oil pipeline running through the Straits of Mackinac.

Michigan Radio's M I Curious is a news experiment where we investigate questions submitted by the public about our state and its people.

As part of our M I Curious project, Justin Cross asked Michigan Radio this question:

What is the status of the aged Enbridge oil pipeline running through Lake Michigan at the Straits of Mackinac?  

Cross says he found out about the Enbridge pipeline in the Straits the same way other people did.

“I had no idea it existed until I saw the National Wildlife Federation video last fall. And I’m like ‘Holy Smokes. How did this happen?”


“Think about what would happen if one of those sprung a leak," warns one of the speakers in the video.

The video also shows footage of an underwater dive on part of the pipeline. The words “broken supports” and “unsupported pipeline covered in debris” are shown in sections of the video, which  labels the 60 year-old pipeline as a “Sunken Hazard.”

Oil company's connection to Kalamazoo River spill a big worry

Enbridge is the same company that had a pipeline split open and dump more than 800,000 gallons of thick tar sands oil into the Kalamazoo River.

So naturally — a lot of people — want to know whether the pipeline under the Straits is in good shape or not.

We went to the Straits of Mackinac to ask Enbridge some questions ourselves and that’s where I met Tom Prew.

“I’m a region engineer for Enbridge." he said. "Today we’re out in the Straits of Mackinac working on the pipeline supports for our crossing.”

Line 5
Credit Mark Brush / Michigan Radio
Michigan Radio
A diver finishes anchoring the support in place on the Line 5 pipeline.

This barge is anchored out in the middle of Straits. There’s a video screen that shows a diver 200 feet below installing a new anchor support on the pipeline.

The State of Michigan has an old easementthat says the pipeline has to be supported at least every 75 feet.

But the strong currents in the Straits of Mackinac can sweep sediment away. The lake bed can shift. So that means the length of unsupported pipeline can  change over time.

Prew says that’s what keeps them busy.

"The biggest challenge is just making sure the support is adequate. Other pipelines have issues with third party damage and corrosion. We don't really have that out here. The main issue is just making sure it's well supported and the coating is in place." -Tom Prew, Enbridge engineer

This section of pipeline is just small part of Enbridge’s Line 5 system. It’s 645 miles long over all. The company says it transports light crude oil and natural gas liquids or propane.

Line 5 had a significant spill in 1999 in the Upper Peninsula, but the company says this section of line under the Straits has never had a leak. Prew says it’s because of the way this section of pipeline was built back in 1953. He says the steel is strong. And their inspection tools don’t show any major problems.

So that’s what Enbridge tells us.

But this is the same company that knew about cracks and corrosion on the pipeline that split open near the Kalamazoo River.

Watchdog group says good maintenance is more important than age

Carl Weimeris with the National Pipeline Safety Trust, a pipeline watchdog group. I asked him what seems like the obvious question about this pipeline: “How can a 60-year-old line be in excellent condition?”

“We’ve see older pipelines that have been operated and maintained well that look almost like new pipelines," he said. "... and on the other hand we’ve seen new pipelines that look like they’re 80-years-old, or are in bad shape. So it really depends on how the company has been operating and maintaining it. And that’s a really hard thing to find out.”

It’s hard to find out because the company itself is the keeper of the information.

The Department of Transportation's (DOT) Pipeline and Hazardous Material Safety Administration is the federal agency that oversees pipeline companies. It audits a company’s management and maintenance records and if they look good—then that’s it.

The next step of our investigation

So back to Justin Cross’ question: “What is the status of the old Enbridge pipeline under the Straits?” Well, to truly know the answer, we would need to see the records that back up Enbridge’s claim.

This Thursday, we’ll hear about the records that are available, and what those records tell us about the pipeline’s condition.

Correction: An earlier version of this story reported Enbridge Line 5 transports liquid natural gas. That is not correct. It transports light crude and natural gas liquids.

Mark Brush was the station's Digital Media Director. He succumbed to a year-long battle with glioblastoma, an aggressive brain cancer, in March 2018. He was 49 years old.
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