Subchapter B Permits - Major Sources (cont'd)
Prevention of Significant Deterioration
PSD permitting applies to major sources and major modifications in attainment areas, and one of the goals of PSD permitting is to preserve, protect, and enhance air quality in Class I areas (wildernesses and national parks).
PSD applies to construction of major sources. For named sources that are listed in the Federal Clean Air Act, the major source significant emission rate is 100 tons per year, and the potential to emit (PTE) calculation must include fugitive sources and any stationary source regulated by a New Source Performance Standard (as contained in 40 Code of Federal Regulations Part 60) or a National Emission Standard for Hazardous Air Pollutants (as contained in 40 CFR Part 61) as of August 7, 1980.
Some named sources are petroleum refineries and chemical process plants.
For unnamed sources, the major source significant emission rate is 250 tons per year, and the PTE calculation does not include fugitive sources.
PSD also applies to major modifications, which would be an increase of emissions equal to or greater than the significant emission rate for that pollutant. This means that a modification is only subject to PSD if the existing source being modified is already major, and the net emissions increase of any pollutant emitted from the source is at or above the significant emission rate for a modification. Minor sources are subject to PSD only when the proposed project increase is major in and of itself (100 tons per year for named sources or 250 tons per year for unnamed sources).
PSD requires a BACT evaluation that also includes a review of the RACT/BACT/LAER Clearinghouse. In addition, PSD review requires an assessment of existing air quality; a demonstration that the new emissions will not cause or contribute to an exceedance of any applicable NAAQS or PSD increment; and the evaluation of effects on visibility, soil and vegetation, and impacts to Class I areas.
Screening or refined air dispersion modeling may be required. If modeling is required, predicted concentrations or existing ambient air concentrations are used to evaluate impacts on air quality.
A PSD permit must:
- identify the emission units to be regulated by PSD;
- establish emission standards or operating limits;
- specify methods for determining compliance; and
- outline procedures to maintain continued compliance.