Two environmental groups on Wednesday filed an appeal challenging the state’s environmental impact statement for the proposed $2.6 billion Enbridge Line 3 oil pipeline across northern Minnesota.

In a filing with the Minnesota Court of Appeals, Friends of the Headwaters and the indigenous environmental group Honor the Earth asked the court to examine the environmental-review process leading up to a permit granted in June by the state Public Utilities Commission (PUC) for the 340-mile pipeline.

Honor the Earth called the process “contrary to law, not supported by the evidence, and arbitrary and capricious.”

The groups claim that the project’s environmental impact statement (EIS) was flawed, that regulators refused to consider alternatives to the proposed pipeline, and that the review process ignored or minimized the interests of Indian tribes whose land is located along the proposed pipeline route.

The appeal also claims that the commission failed to examine the potential for oil spills in specific areas, such as Lake Superior.

“While the EIS is long, it is shallow and was written to support approval of Line 3,” said Winona LaDuke, executive director and co-founder of Honor the Earth. “The EIS simply failed to take a hard look at the costs of Line 3 to our people, our land, our water and our climate.”

Enbridge’s existing Line 3 pipeline, which transports Canadian oil to the company’s terminal in Superior, Wis., is aging, corroding and operating at just over half of its capacity due to safety concerns. Calgary, Alberta-based Enbridge wants to replace Line 3 with a new pipeline that would run on a new route.

Environmental groups and American Indian bands oppose the pipeline and the new route, saying it would expose a new region of lakes, rivers and wild-rice waters to degradation from possible oil spills.

The proposed pipeline would carry crude oil derived from Canadian tar sands.

Frank Bibeau, an attorney for Honor the Earth, called tar sands “the dirtiest fossil fuel.” Beyond the danger of spills, he said, regulators need to consider the cumulative effects on the environment of using oil derived from tar sand.

“If you think about where we are from a climate-change aspect, the gases and other questionable things that are released in the extraction of the tar sands ... [are] already impacting our waters in Minnesota,” Bibeau said.

A PUC spokesman was not immediately available for comment Wednesday.