A formal demand to shut off oil flows immediately has been added to the Michigan lawsuit seeking to cancel the state’s 1953 right-of-way easement for Enbridge Inc.’s 540,000 b/d Line 5 across the Straits of Mackinac.

Michigan Attorney General Dana Nessel injected urgency into the case by filing motions requesting an injunction and restraining order against restarting deliveries that Enbridge temporarily suspended last week.

The motions claim the Canadian pipeline poses “grave risk of irreparable damage to the Great Lakes.” Enbridge said the added courtroom maneuver “is legally unsupportable, unnecessary and will be vigorously opposed.”

The new duel erupted after Enbridge restarted oil flows over the weekend through one of two Line 5 pipes that were both shut down last week as a precaution. An inspection found damage to an anchor support for one of the pipes.

The operation has proceeded “working very closely” with the U.S. watchdog for interstate oil deliveries, the Pipeline and Hazardous Materials Safety Administration (PHMSA), Enbridge noted.

“The east leg pipeline remains shut down, while the west leg was restarted after a thorough review and consultation with our safety regulator,” management said of the Line 5 right-of-way. 

Nessel’s motions seek court orders for Enbridge to turn over all information on the incident and halt all flows through both Line 5 pipe legs while Michigan and independent experts conduct a review.

In a letter to Michigan Gov. Gretchen Whitmer, Enbridge President Al Monaco pledged to keep state authorities fully informed.

“Enbridge will not resume operation on the east leg without any discussion with the State of Michigan and approval from PHMSA,” wrote Monaco. “I have directed the responsible individuals at Enbridge to ensure we provide regular and fulsome briefings to state officials and discuss current plans with your administration and with you personally, if desired.”

The new safety dispute broke out after Enbridge won a verdict earlier this month from the Michigan Court of Appeals that upheld a mid-2018 agreement completed with the previous Republican-led administration to allow Line 5 stay by burying it in a new $500 million utility tunnel.

Whitmer and Nessel, both Democrats, won office in late 2018 on platforms that committed to discard the pipeline strait crossing. The easement case, including the new motions to halt all flows, is one of three protest lawsuits currently underway.

In a second pending Michigan case, northern native tribes and landowners are challenging the safety of Line 5 hardware. In Wisconsin, Enbridge faces a lawsuit against Line 5 by the Red River Band of the Lake Superior Chippewa.