The Minnesota Supreme Court will decide whether state regulators erred in issuing permits for PolyMet Mining Corp.'s copper-nickel mine without a special hearing, and could impose further review of the $1 billion project.
The state's highest court became involved Tuesday in the landmark mine project near Hoyt Lakes — a new type of mine for the state — after an appellate court struck down three permits and sent them back to the state Department of Natural Resources (DNR) for a contested case hearing.
The lower court reversed PolyMet's permit to mine and two dam safety permits in January, partly on the grounds that the DNR did not hold the contested-case hearing to vet significant objections from environmentalists and the Fond du Lac Band of Lake Superior Chippewa, who live downstream from the planned mine.
The groups oppose the copper-nickel mine, saying it will pollute nearby waters such as the St. Louis River, with toxic metals and sulfuric acid, often called acid mine drainage, that develops when sulfide-bearing ore is exposed to air and water.

PolyMet, now majority owned by Swiss mining conglomerate Glencore, had been moving close to actually breaking ground on the fully-permitted mine in northeast Minnesota when the lower court suspended the permits last fall.
A decision requiring the DNR to hold the contested-case hearing would further delay the project because such hearings — trial-like hearings before an administrative law judge — can take about a year.
The hearing would also open the decisionmaking process on a historic project, the state's first hard-rock mine, to public scrutiny. The state has a history of iron ore and taconite mining, but not nonferrous mining. The DNR would then make new decisions on the three permits.
In Tuesday's oral arguments, Jonathan Katchen, a lawyer for the DNR, said the agency carefully considered the request for a hearing and has the authority to deny them.