Minnesota regulators approved Thursday the replacement of an oil pipeline through the Fond du Lac Reservation.

The Minnesota Public Utilities Commission gave Enbridge the OK to take 10 miles of its existing Line 4 , which currently sits above grade but under a mound of soil, and completely move it below grade.

The existing 48-inch diameter above-ground pipe is set be removed and replaced with a 36-inch underground pipe. Work on the $100 million project would take place as Enbridge replaces its Line 3 oil pipeline, which runs parallel to Line 4.

The Fond du Lac Band of Lake Superior Chippewa supports the Line 4 replacement.

Sara Van Norman, a Band attorney, told the PUC in March that the project was "remedial and very much in the interest of my client."

The Band had opposed the Line 3 project. However, shortly after Line 3 was approved by the PUC, the Band agreed to allow Enbridge to build the pipeline through its reservation where five other pipelines, including Line 4, already run.

Built in the early 1970s, Enbridge's Line 4 oil pipeline carries 796,000 barrels of oil per day from Alberta to the Enbridge terminal in Superior.

While Enbridge maintains it will build the new Line 3 in 2020, the project has sat in regulatory limbo since the Minnesota Court of Appeals in June said an environmental review of Enbridge's controversial Line 3 oil pipeline was "inadequate" because it did not consider the effects of an oil spill in Lake Superior's watershed.

The PUC still needs to correct the environmental review but must wait until the Minnesota Supreme Court decides whether to take the case after several environmental groups appealed the Court of Appeal's decision.