Enbridge agrees not to ship heavy crude oil through Great Lakes pipeline in Michigan

A company that ships oil through the Great Lakes pledged Thursday to keep heavy crude out of a pipeline in northern Michigan.

Enbridge Energy already doesn't transport heavy crude in the Straits of Mackinac. The deal signed with state officials preserves the status quo and requires a 180-day notice if changes are proposed.

"Although Enbridge does not and has not used Line 5 for heavy crude, I am pleased with the additional layer of protection this agreement provides to prevent an environmental and economic catastrophe in the Straits," said Dan Wyant, director of the Michigan Department of Environmental Quality.

The Straits separate Michigan's two peninsulas where lakes Huron and Michigan converge.

In July, a state pipeline task force warned that a rupture of heavy crude would be difficult to clean up because it's heavier than lighter oil.

"The state has concluded that transporting heavy crude oil through the Straits pipelines would present an unreasonable risk of ecological and economic harm. ... Enbridge does not agree with the state that transporting heavy crude oil through the Straits pipelines could present an unacceptable risk," the seven-page agreement between the company and Michigan states.

Separately, Gov. Rick Snyder announced creation of a 15-member pipeline safety advisory board in Wyant's department.

Enbridge, based in Calgary, Alberta, was responsible for one of the largest inland oil spills in U.S. history. In 2010, more than 800,000 gallons of oil poured out of a ruptured line in southwestern Michigan, spoiling the Kalamazoo River and tributaries.