Montana Environmental Information Center v. Department of Environmental Quality

The DEQ renewed a 1999 MPDES Permit on September 14, 2012 that allowed Western Energy Company to discharge pollutants from the Rosebud Mine into streams. Environmental groups MEIC and the Sierra Club sued, arguing this violated both the Montana Water Quality Act and federal Clean Water Act because the DEQ’s interpretation of its own regulations that exempted waters with ephemeral characteristics from water quality standards was arbitrary and capricious. The district court agreed, but the Montana Supreme Court reversed. It held the DEQ’s interpretation was lawful and remanded for further fact finding to assess how the DEQ applied the interpretation and to require the agency to explain how its representative monitoring of precipitation-driven discharges at the mine were representative of the monitored activity in fact.