New stationary sources, sources that undergo significant modification and relocated sources which result in an emissions increase are subject to additional emissions control requirements. Prior to construction, operators must contact their local air district to apply for a permit to construct for any new, modified, or relocated source. Sources with criteria emissions over defined thresholds,may trigger New Source Review (NSR). The new source review permitting program protects air quality by ensuring that sources are as clean as possible and any new emissions are offset, while still allowing for economic growth. The level of control required to limit criteria pollutant emissions from new, modified or relocated sources is determined by best available control technology (BACT) requirements. For sources that emit toxic air contaminants, best available control technology for toxics (T-BACT), may also be triggered. In California, the control level required for new, modified, or relocated sources varies based on the source size (major or minor), the region’s attainment status, and the criteria defined in air district BACT policies.
There are three levels of control that may apply to new and modified sources in California:
- Federal BACT: Required on major new or modified sources in areas that are meeting national ambient air quality standards (i.e. attainment areas).
- Federal lowest achievable emissions rate (LAER): Required on major new or modified sources in areas that are not meeting national ambient air quality standards (i.e. non-attainment areas).
- CA BACT: Allows air districts to require more stringent controls beyond LAER on sources if technologically feasible and cost effective (CE).
Further information on how each level of control is defined and determined in California can be found on the BACT definitions page.
Similar in concept to BACT, T-BACT requirements ensure that new or modified sources that emit toxic air contaminants are well controlled. The major difference between BACT and T-BACT is that T-BACT is not part of NSR, and instead the program requirements are defined in district rules based on a local health risk assessment thresholds.
BACT Program Resources
Basics on how BACT is defined by federal and state law.
Links to BACT policies that further define individual district programs.
BACT Guidelines and Determinations
Description of how districts use guidelines and determinations to determine BACT.
Tools to assist with the identification of the best technologies for reducing emissions.