Montana Sulpher & Chemical Co. v. EPA

The EPA may rely on modeling to predict SO2 violation under the Clean Air Act when existing sampling data is limited or insufficient.

This is an appeal of EPA action under the Clean Air Act (CAA). Montana Sulphur challenges a 1993 Montana State Implementation Plan (SIP) Call, a 2002 partial disapproval of the SIP, and a 2008 Federal Implementation Plan (FIP). In this review of EPA administrative action, Montana Sulphur challenged on a broad array of theories concerning a broad array of issues. Key in the Courts analysis is the deference given to EPA’s statutory interpretation, as well as, the deference given the EPA in evaluation of complex scientific data within its area or expertise. First, EPA did not exceed its authority under the CAA by issuing the SIP Call. The SIP Call was based on predictive modeling that the ambient air quality around the Montana Sulphur facility was below EPA standards. The Court concluded that the EPA could rely on any sound data that was available and it was determined that modeling provided sound data. This was supported by the EPA position that actual air quality samples were of a specific area at a specific time, and were not necessarily a better way to show ambient air quality. Given the public health concern and limited monitoring, the EPA did not act arbitrarily or capriciously in making the SIP Call. Second, Montana Sulphur contends that since EPA did not create the FIP within two years of disapproving the SIP, it cannot take effect. The Court concludes that the passing of the two year period does not remove the EPA of its authority to create a FIP. PETITIONS DENIED.