Editors' Summary: One of Congress' goals in enacting the Clean Air Act was to prevent clean air from becoming dirty. Accordingly, the Clean Air Act established a "prevention of significant deterioration" (PSD) program, requiring that specified new facilities use the "best available control technology" (BACT). However, Congress left the task of defining BACT to EPA.

Over time, EPA has fleshed out the parameters of BACT in guidance documents and administrative appeals of PSD permits. Currently, EPA applies a "top-down" analysis to the BACT determination, placing the burden on a permit application to show substantial or unique technical, environmental, or economic objections why the most stringent control available should not be used. This policy has proven controversial and has been challenged in court. In this Article, the authors explore the history of BACT analysis and the current substantive and procedural issues raised by EPA's current BACT policies.