Enbridge Energy is working to fix another aquifer rupture caused by construction of the Line 3 replacement oil pipeline across northern Minnesota.

The Canadian oil company and the state Department of Natural Resources (DNR) confirmed the breach in Aitkin County on Thursday, after it was first announced by Healing Minnesota Stories and a water activist group tracking Line 3's environmental impacts called Waadookawaad Amikwag, or Those Who Help Beaver.

The new breach is the fourth confirmed along the route of the pipeline, which started operating in the fall of 2021. The project generated fierce opposition in the state from environmental activists and tribes.

The rupture happened near Moose Lake in Aitkin County, a wild rice lake in an area of wetlands and peat bogs considered to have outstanding biodiversity. It's near an unincorporated community called Swatara in Macville Township, according to the DNR.

In a statement, the DNR said it's investigating the construction impacts at Moose Lake and described it as a "remote and hydraulically complex" place.

Groundwater at the new break is flowing to the surface at about 10 to 15 gallons per minute, the DNR said. That's "considerably lower" than the rate at which groundwater initially flowed from the other three breaks, it said.

The other three breaches, reported in 2021, occurred near the town of Clearbrook in Clearwater County; at LaSalle Creek in Hubbard County; and near the Fond Du Lac Band of Chippewa's reservation in St. Louis County. An estimated 280 million gallons of groundwater spilled from those ruptures. The flows have been stopped, but the DNR said it's still monitoring.

Enbridge has paid more than $11 million to address environmental damage from building Line 3. Last October it was charged with a misdemeanor in Clearwater County District Court related to the Clearbrook rupture, for taking state waters without a permit. The company admitted that it delayed notifying the state about the damage and reached an agreement with prosecutors that the charge will be dismissed after one year if the company remains law-abiding.

State lawmakers have allowed the DNR to impose steeper fines for water violations, so Enbridge could potentially face a penalty of up to $40,000 for the latest rupture. Lawmakers also removed the requirement that the DNR forgive penalties for serious or repeat violations if the party fixes the problem within 30 days. The DNR would not discuss penalties and said it was still investigating and gathering facts.

Enbridge spokeswoman Juli Kellner said in a statement that the company will submit a plan to correct the Moose Lake area damage and will implement it when it's approved. She noted that the aquifer breaches don't involve the pipe itself but involve the sheet-metal piling driven into the ground used to reinforce the trenches that crews work in.

Kellner defended the company's record, saying Line 3 required more than 60 federal, state, local and tribal approvals involving "the strictest environmental requirements in state history." Enbridge has worked with regulators and fixed problems according to approved plans, she said.

Jeff Broberg, a geologist for Waadookawaad Amikwag, provided a letter he sent to the DNR. In it he said he thinks the artesian groundwater has been flowing from the Moose Lake rupture since construction in late 2021 and that regulators have failed to adequately protect the state's groundwater — a public resource — and the broader ecosystems.

Broberg and Waadookawaad Amikwag have been involved with the thermal imaging flyover of the pipeline route in 2021 led by the White Earth Band of Ojibwe. The footage revealed as many as 45 spots along the 355-mile pipeline where groundwater appeared to be flowing to the surface.