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New Source Review (NSR)


The purpose of the New Source Review (NSR) program is to provide methods to grant Authorities to Construct to new and modified stationary sources without interfering with the attainment or maintenance of ambient air quality standards. When a person applies for a permit for new equipment or to modify existing equipment, the source must go through a NSR review, which is conducted pursuant to Sac Metro Air District Rule 202 when the facility is a minor sources and Rule 214 when the facility is a major sources. Although the nuances of NSR are intricate, there are two key elements; Best Available Control Technology and Emissions Offsets.

​Best Available Control Technology

Best Available Control Technology (BACT) is the requirement that certain air pollution sources install equipment or employ administrative practices that will result in the lowest achievable emission rate. The lowest achievable emission rate is defined by state law as:

  • The most stringent emission limitation contained the State Implementation Plan for the particular class or category of source, unless the owner of the source demonstrates that the limitation is not achievable, or
  • The most stringent emission limitation that is achieved in practice by that class or category or source.

In no case can the lowest achievable emission rate be greater than the emissions allowed under a federal New Source Performance Standard.

The BACT Clearinghouse (PDF) contains a list of the most recent BACT determinations made by the Sac Metro Air District for the most common types of equipment and processes. This list should be used only as guidance.

​Emissions Offsets

An emissions offset is a reduction in pollution from an existing source of air pollution within the Sac Metro Air District. It is an emission reduction credit that compensates for an emission increase of an affected pollutant from a new or modified source subject to the requirements of Rule 202. When emissions are offset, the total allowable emissions from existing sources and the proposed source will be less than the total emissions from existing sources.

​Toxic Pollutants

Each new source is also evaluated to determine whether there is the potential to emit toxic air pollutants. Emission controls, similar to BACT, called T-BACT are required for certain sources.

In addition to T-BACT requirements, permits for equipment that may emit toxic air pollutants may also contain conditions required by the National Emission Standards for Hazardous Air Pollutants (NESHAPs) and Air Toxic Control Measures (ATCMs) promulgated by the California Air Resources Board.

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