Minnesota public utilities regulators Friday denied a request from environmental groups to reopen the public comment process on a controversial and much-delayed oil pipeline proposed to transport crude oil from Canada across northern Minnesota.

The pipeline in question would be built by Enbridge Energy to replace its existing northern Minnesota pipeline, “Line 3.” Plans have called for the $2.6 billion Line 3 replacement to run along a new route adjacent to a brand-new pipeline called Sandpiper.

But Calgary-based Enbridge last month pulled out of the $2.6 billion Sandpiper project, and now plans only to build the Line 3 replacement along the new route, which would pass through pristine waters — including the Mississippi River’s headwaters — on the way from Clearbrook, Minn., to Superior, Wis.

Environmental groups say that by dropping Sandpiper, a material change occurred in the process of approving a new Line 3. They say a material change was also created by Enbridge’s July consent agreement with the federal government over pipeline spills that occurred in 2010,

Both events occurred after the Minnesota Department of Commerce had concluded gathering public input for its Line 3 “scoping” study, which sets the scope of a required environmental impact statement. Thus, the public comment period should be reopened, environmental groups argue.

“Because of the drastic changes since the end of the [public] comment period, it would be unlawful to go ahead with the environmental impact statement,” Kevin Lee, an attorney for the Minnesota Center for Environmental Advocacy, said Friday before the Minnesota Public Utilities Commission (PUC).

Lee’s group argues that because Sandpiper and Line 3 would share the same thruway, the public has long understood the two to be inextricably linked. The main reason to abandon Line 3’s current route — which is north of the proposed new route — was to follow the Sandpiper pipeline, the group contends.

Plus, Enbridge’s July settlement with the U.S. Department of Justice implies that it might continue to run the old Line 3, even after a new Line 3 is built, Lee said. With the settlement, Enbridge agreed to pay $177 million and improve pipeline safety to resolve claims from spills in Michigan and Illinois.

Eric Swanson, an attorney for Enbridge, told the PUC that the Sandpiper withdrawal doesn’t affect the Line 3 replacement, and that the “company has consistently stated that it will deactivate [old] Line 3” when the new one opens. “There are no ifs, ands or buts about it.”

PUC Commissioner John Tuma said the wording of Enbridge’s consent decree does create some confusion. “Let me be clear,” Tuma asked Swanson, “you will pursue abandonment?” Swanson answered “yes.”

The PUC voted 5-0 against reopening the public comment period on Line 3. The environmental impact statement will proceed; a final document is expected by July.

Enbridge proposed the Line 3 replacement two years ago, and Sandpiper a bit before that. Sandpiper would have carried crude from North Dakota to Superior. Enbridge pulled the plug on Sandpiper after it agreed to buy a $1.5 billion stake in a pipeline system that includes the Dakota Access, which runs from North Dakota to Illinois.

The Dakota Access is mostly complete, though large protests have broken out against it in recent months due to opposition by the Standing Rock Sioux Tribe in North Dakota. Among other things, the tribe fears that a leak from the Dakota Access would imperil its drinking water.