Environmental advocates are calling for Enbridge to shut down its Line 5 pipeline which runs beneath the Mackinac Straits.
The Traverse City-based environmental group For the Love of Water (FLOW) issued a report today questioning the safety of the 62-year-old line.
The report says structural concerns and possible corrosion put the line at risk for leaks and ruptures.
Liz Kirkwood, FLOW's executive director, said decades of powerful currents and shifting sands at the bottom of the Straits has likely accelerated wear on the pipeline.
"These pipelines rely on 1950s technology," Kirkwood said. "The [pipeline's] protective coating and the weld used to connect each 40-foot segment are outdated."
The report also questioned whether the pipeline's integrity has been impacted by zebra mussels, an invasive species not yet present in the Great Lakes when Line 5 was built.
Gary Street, former director of engineering for Dow Environmental, said zebra mussels' excrement has a corrosive impact on exposed steel. He said the invasive species have also made it difficult to inspect for leaks and are putting weight on the pipeline.
"Zebra mussels are tiny little things," Street said. "But millions and millions of these create all sorts of stress the line was never designed to handle."
Street said the Line 5 is "a disaster waiting to happen."
A state-assembled task force is currently reviewing the safety of Michigan's pipelines and is expected to release their findings next month.
Enbridge officials said the company will review FLOW's report and continues to work on Line 5's safety.