MINNEAPOLIS (AP) -- Environmental groups have gone to court to challenge the state's decision to grant key permits for the proposed PolyMet copper-nickel mine in northeastern Minnesota.

The Minnesota Center for Environmental Advocacy and its allies say the permits would allow PolyMet to threaten water quality downstream for centuries, that they fail to address safety concerns about the mine's proposed waste dam and that they fail to protect taxpayers from cleanup costs.

The groups are also asking the Minnesota Court of Appeals to overturn the state's rules governing non-ferrous mining, saying the rules are too vague for courts and regulatory agencies to enforce.

The appeals are separate from requests that the groups made in November to the DNR and Minnesota Pollution Control Agency to suspend PolyMet's permits pending further court action.