Why a Decades-Old Pipeline Has Canada and Michigan at Odds

For 70 years, the Line 5 pipeline has supplied light oil and propane to refineries and homeowners in the U.S. Midwest and the Canadian provinces of Ontario and Quebec without much controversy. Recently, that’s changed. The line’s crossing under a key waterway linking Lake Michigan and Lake Huron has stirred a standoff between Calgary-based Enbridge Inc., the line’s operator, and Michigan Governor Gretchen Whitmer, who wants it shut. The controversy is sparking a political conflagration in the U.S., drawing in the Biden administration and straining relations with longtime ally Canada.

Capable of carrying 540,000 barrels a day, the pipeline originates at an Enbridge oil terminal in Wisconsin. Moving eastward, it traverses the upper Michigan peninsula before crossing under the Straits of Mackinac to the lower peninsula. It crosses the U.S.-Canada border to reach Sarnia, Ontario, where it connects to another pipeline that runs as far as Quebec. The line supplies more than half of Michigan’s propane, according to Enbridge, and is also a key conduit of light crude oil for refineries in Michigan, Ohio, Pennsylvania, Ontario and Quebec.