PSD permits issued to major emitting facilities must include BACT standards for each pollutant subject to regulation under the CAA. These standards must be determined by permitting authorities on a case-by-case basis, subject to EPA review and approval. Steps 2 through 5 of EPA’s preferred “top-down” procedure for making these determinations involve the elimination of technically infeasible options, the ranking of remaining technologies by control effectiveness, the evaluation of energy,  environmental, and economic impacts, the selection of BACT technology, and the specification of BACT emission limitations. As old pollution control technologies are continually replaced by newer ones, these steps present daunting burdens for permit applicants and fertile opportunities for their opponents. [This Article continues from the December 2011 issue of News & Analysis.]