The Minnesota State Court of Appeals upheld the scope of PolyMet Mining Corp. unit Poly Met Mining Inc.'s environmental review for its NorthMet copper project following a challenge from several environmental groups that wanted a supplemental review.

The three-judge panel made a unanimous decision to not prepare a supplemental environmental impact study based on claims by the Minnesota Center for Environmental Advocacy, Friends of the Boundary Waters Wilderness and Water Legacy that PolyMet had changed its project.

The court's ruling, which explained that the changes did not have significant potential environmental effects, covered three consolidated appeals filed in 2018, according to a May 28 release.

PolyMet completed the permitting process for the NorthMet mine and processing plant in March.