North America's existential debate about the virtues and dangers of oil and gas pipelines faces a critical test today in Wisconsin.

That's where a district court judge will hear arguments about whether or not to shut down Line 5, a critical cross-border energy conduit between Canada and the U.S.

The Bad River Band of the Lake Superior Chippewa says spring flooding has rendered the risk of a breach on its northern Wisconsin territory too great to ignore.

Alberta-based Enbridge Inc., the pipeline's owner, says the band is overstating the risk and preventing the company from taking protective measures.

Today's hearing will include lawyers from the state of Michigan, which has been trying in its own courts to shut down Line 5 since 2019.

It's unclear how long the hearings will last or how quickly district court Judge William Conley will rule on the band's request for an order to shut the pipeline down.

The band, which argues that Enbridge's right to operate on its territory has long since expired, fears an imminent disaster after spring floods along the Bad River it says have undermined the terrain around the line.

For its part, Enbridge insists those claims of an emergency are overblown — and that shutting down the pipeline would be too drastic a remedy.

"Despite having to prove both liability and grounds for an injunction, the band has done neither. The motion must therefore be denied," Enbridge argues in a brief filed in advance of the hearing.

Both sides in Canada-U.S. pipeline debate clash today over cross-border Line 5. #Line5 #cdnpoli #USpoli #Enbridge

"No release of oil is 'ready to take place,' 'happening soon,' or 'real and immediate.'"

Even if the risk was high, a shutdown would be inappropriate, Enbridge argues, pointing to a court-ordered contingency plan that spells out the steps it would take if the threat were indeed urgent.

"Enbridge will pre-emptively purge and shut down the line well in advance of any potential rupture," the brief says, adding that the area remains under constant 24-hour video surveillance.

"Any flooding and erosion has not, and would not, catch Enbridge by surprise."

Heavy flooding that began in early April washed away significant portions of the riverbank where Line 5 intersects the Bad River, a meandering, 120-kilometre course that feeds Lake Superior and a complex network of ecologically delicate wetlands.

The band has been in court with Enbridge since 2019 in an effort to compel the pipeline's owner and operator to reroute Line 5 around its traditional territory — something the company has already agreed to do.

But the flooding has turned a theoretical risk into a very real one, the band argues, and it wants the pipeline closed off immediately to prevent catastrophe.

Line 5 meets the river just past a location the court has come to know as the "meander," where the riverbed snakes back and forth multiple times, separated from itself only by several metres of forest and the pipeline itself.

At four locations, the river was less than 4.6 metres from the pipeline — just 3.4 metres in one particular spot — and the erosion has only continued.

Michigan, led by Attorney General Dana Nessel, has been arguing since 2019 that it's only a matter of time before Line 5 leaks into the Straits of Mackinac, the ecologically delicate waterway where it crosses the Great Lakes.

"The alarming erosion at the Bad River meander poses an imminent threat of irreparable harm to Lake Superior which far outweighs the risk of impacts associated with a shutdown of the Line 5 pipeline," Nessel argues in her brief.

"Without judicial intervention, it is likely that this irreparable harm will be inflicted not only on the band, but also on Michigan, its residents, and its natural resources."

The economic arguments against shutting down the pipeline — which carries 540,000 barrels of oil and natural gas liquids daily across Wisconsin and Michigan to refineries in Sarnia, Ont. — are by now well-known.

Line 5's defenders, which include the federal government, say a shutdown would cause major economic disruption across the Prairies and the U.S. Midwest, where it provides feedstock to refineries in Michigan, Ohio and Pennsylvania.

It also supplies key refining facilities in Ontario and Quebec, and is vital to the production of jet fuel for major airports on both sides of the Canada-U.S. border, including Detroit Metropolitan and Pearson International in Toronto.

A lengthy statement issued Tuesday by the Canadian Embassy warned of severe economic consequences of shutting down the line, as well as the potential ramifications for bilateral relations.

"The energy security of both Canada and the United States would be directly impacted by a Line 5 closure," the statement said. Some 33,000 U.S. jobs and US$20 billion in economic activity would be at stake, it added.

"At a time of heightened concern over energy security and supply, including during the energy transition, maintaining and protecting existing infrastructure should be a top priority."

Talks have been ongoing for months under the terms of a 1977 pipelines treaty between the two countries that effectively prohibits either country from unilaterally closing off the flow of hydrocarbons.

Nonetheless, the embassy's statement and the Enbridge brief tacitly acknowledge that the prospect of a shutdown order is very real.

In Enbridge's case, the brief pre-emptively asks the judge to grant a stay of 30 days, should an injunction be ordered, to give lawyers time to mount an appeal.

And if "this specific, temporary flood situation" results in a shutdown, the embassy says, Canada expects the U.S. to comply with the treaty, "including the expeditious restoration of normal pipeline operations."

This report by The Canadian Press was first published May 18, 2023.

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