Air Quality Management - Prevention of Significant Deterioration (PSD) and New Source Review (NSR)

Major new stationary sources of air pollution and major modifications to major stationary sources are required by the Clean Air Act to obtain an air pollution permit before beginning construction. The process is called New Source Review (NSR) and is required whether the major source or modification is planned for an area where the national ambient air quality standards (NAAQS) are exceeded (nonattainment areas) or an area where air quality is acceptable (attainment and unclassifiable areas). Permits for sources in attainment areas are referred to as prevention of significant air quality deterioration (PSD) permits while permits for sources located in nonattainment areas are referred to as NAA permits. The entire program, including both PSD and NAA permit reviews, is referred to as the NSR program.

No source or modification subject to PSD review may be constructed without a permit. PSD permits mandate the installation of pollution controls that represent the best available control technology (BACT). BACT is defined as an emission limit based on the maximum degree of reduction of each pollutant subjected to regulation under the Clean Air Act. BACT is done on a case-by-case basis, and considers energy, environmental, and economic impacts.

Permits in nonattainment areas (NAAs) must meet the lowest achievable emission rate (LAER). In all cases, the BACT and LAER must be at least as strict as any existing NSPS for the source. The important difference between the New Source Review permits and the NSPS program is that NSR is source specific, whereas the NSPS program applies to all sources nationwide. This gives states the authority to require more stringent controls to meet the ambient air quality standards in specific geographic areas.