Major New Source Review

Some NSR authorizations trigger major NSR permitting--either Nonattainment NSR permitting or Prevention of Significant Deterioration (PSD) permitting. These types of permits have additional requirements.


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Significant emission rates, significant increases, significant threshold levels, threshold quantities, and trigger levels are one in the same. Here's an example of how this may be stated:
Nitrogen oxides (NOx) are a precursor for the criteria pollutant ozone. The trigger level for a NOx source to be considered major in a serious ozone nonattainment area is 50 tons per year. In addition, for a modification in a serious ozone nonattainment area to be major for NOx, the significant threshold level is 25 tons per year.

Major sources, major modifications, and significant emission rates will be discussed in more detail in Module 3.

Nonattainment New Source Review

New major sources and major modifications in a designated nonattainment area are required to go through Nonattainment NSR. Nonattainment reviews apply in areas which are not in compliance with the National Ambient Air Quality Standards (NAAQS). For additional information regarding nonattainment areas, see the "Learn More" sidebar on this page.

If Nonattainment NSR is triggered, the new emissions must be offset by actual emission reductions achieved by other sources anywhere in the nonattainment area. The emission reductions must be certified by the TCEQ Emissions Banking and Trading staff. The amount of air contaminants that must be offset depends on the classification of the nonattainment area. For example, in a marginal nonattainment area, the offset ratio is 1.10 tons of the air contaminant reduced per ton of new emissions.

In addition to the offset requirement, nonattainment permits must include the lowest achievable emission rate (LAER), as opposed to BACT. LAER is usually more stringent than BACT.

Prevention of Significant Deterioration

Major sources and major modifications in an attainment area are subject to PSD. A source that emits or has the potential to emit a federally regulated NSR pollutant at or above a significant emission rate is considered major for all PSD pollutants. Fugitive emissions are not included in the PSD determination unless it is a type of source that is specifically listed in the Federal Clean Air Act (also known as a named source). PSD permits must include BACT.

In addition, the PSD review requires additional air dispersion modeling to determine if the new emissions will have a negative impact on the NAAQS of the surrounding air quality.

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Value: 5
Nonattainment and Prevention of Significant Deterioration reviews are associated with federally regulated pollutants (i.e., criteria pollutants with National Ambient Air Quality Standards).

When you're ready, please proceed to Part IV of this module by moving on to the next page.

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