PolyMet hopes to build a copper-nickel-platinum mine near Babbitt and process the minerals at the old LTV iron ore processing site in Hoyt Lakes.

A coalition of environmental groups had alleged that PolyMet plans on building a bigger mine than they had applied for in their air permit, and said the Minnesota Pollution Control Agency had failed to conduct an adequate investigation during the application process. The groups cited documents that PolyMet provided to investors that included preliminary economic analysis of higher outputs than the company was seeking in its air permit application.

Eleven months ago, the Minnesota Court of Appeals remanded the air permit back to the MPCA to provide more information. The MPCA and PolyMet then petitioned the state Supreme Court to review the case.

Wednesday's ruling by Justice Margaret Chutich finds that the federal Clean Air Act does not require the MPCA to scrutinize whether PolyMet intends to expand mining operations in the near future. 

"Nowhere in the [Environmental Protection Agency] Guidance does it dictate that a permitting agency must investigate sham permitting at the synthetic minor source permit application stage," the ruling says, noting that the EPA does have several enforcement options if a permittee does not comply with the operational restrictions set out in a permit.

The ruling also notes the MPCA "could, if it so desired, investigate sham permitting during the synthetic minor source permit application process, but it is not required to do so."

The case was reversed and remanded back to the appeals court to consider other issues, including an allegation that PolyMet had submitted false or misleading information to the agency.

To see the original article and read related stories, follow this link to the WDIO-TV website.  https://www.wdio.com/mining-news/minnesota-supreme-court-polymet-air-emissions-permit/6022071/