Three environmental groups and two Ojibwe bands on Wednesday filed lawsuits challenging the state's approval of Enbridge's controversial new $2.6 billion oil pipeline planned for northern Minnesota.

The lawsuits, filed with the Minnesota Court of Appeals, seek to overturn a June decision by the Minnesota Public Utilities Commission (PUC). By a unanimous vote, the PUC granted a "certificate of need" for Enbridge's new pipeline, which would ferry Canadian oil across Minnesota to the company's terminal in Superior, Wis.

A joint appeal was filed by Honor the Earth, a Minnesota-based indigenous environmental activist group, the Sierra Club and the White Earth and Red Lake bands of Ojibwe. Friends of the Headwaters, a Minnesota environmental group, filed a separate lawsuit. The appeals were expected.

"Honor the Earth is appealing this decision because it is a rogue decision," Winona LaDuke, the group's executive director, said in a statement. "The certificate of need was issued based on bad math and puts Minnesotans into a very dangerous situation in terms of liability."

Enbridge said in a statement it believes the court will reaffirm the PUC's decision, which was based on a "thorough review spanning four years." The pipeline, which would replace the company's current Line 3, "is the most studied pipeline project in the history of Minnesota," the company said.

Before it begins construction, Enbridge must still get several other state and federal permits.

Calgary-based Enbridge's current Line 3 is aging, corroding and operating at only 51 percent capacity due to safety concerns. The PUC, in approving a new Line 3, cited the current pipeline's deterioration along with concerns about the reliability of future oil supply in Minnesota.

The new 330-mile pipeline would follow the route of current Line 3 and five other Enbridge pipelines to Clearbrook. From there, it would jut south to Park Rapids before heading east to Superior, Wis.

Pipeline opponents say the approved route opens a new region of Minnesota's lakes and rivers to environmental degradation due to possible oil leaks. They also believe the project would exacerbate climate change. Some Ojibwe tribes also have opposed the pipeline because it traverses land upon which they claim treaty rights to hunt and fish.

A key factor in the Line 3 appeal is a "long-range energy demand forecast" that's required under Minnesota law for pipeline projects. The appeal alleges Enbridge did not provide an adequate forecast, instead assuming that future global oil demand would be sufficient to cover oil production in western Canada — as projected by Canadian oil producers.

Enbridge has defended the integrity of its forecasts. The PUC found that it had approved Enbridge pipelines in the past based on forecasts with a similar methodology. The panel also found there was insufficient evidence to conclude long-term oil demand would be dampened by the rise of electric vehicles and carbon-reduction efforts to counter climate change.

Any appeals of the PUC's approval of the new Line 3 must be filed by the end of Friday.

Honor the Earth, Friends of the Headwaters and three Ojibwe bands also have appealed the PUC's March approval of the state environmental impact statement conducted for the Enbridge project.