BACT Determinations and Guidelines
When air district permit engineers write or update permit conditions for a source that triggers best available control technology (BACT), they must first determine the types of technologies that have been achieved in practice (AIP) for that class and category of emission source. To do this, air districts generally use two types of documents to assist in the identification of BACT - determinations and guidelines. It is important to note, that not all air districts have BACT determinations or guidelines. Unless a district has a unique source, many smaller districts rely upon the BACT limits determined by larger districts to permit equipment.
BACT determinations contain limits that a specific piece of equipment (or process) has been required to meet within the district. This information allows permit engineers to confirm that an emissions limit has been achieved in practice, which is a critical step for ensuring that the most stringent emissions controls are required. For this reason, CARB's BACT database only contains determinations that have been verified by Permit to Operate (PTO) or an Authority to Construct (ATC).
BACT guidelines provide an overview of the limits that may be required when a source type is permitted. Guidelines are helpful for assisting permit engineers and source engineers initially determine the limits and associated technologies that may constitute BACT. The information contained in guidelines may come from multiple sources including permits from within and outside of the district or state, regulations, or as a result of a literary review. Guidelines also contain information on conventional and alternative equipment that has been determined to be technologically feasible and cost-effective, but is not yet required as BACT.