When a major New Source Review (NSR) air permit is sought under the federal Prevention of Significant Deterioration (PSD) program for a large project, the critical path for timely permit issuance is often the successful completion of all the potentially required impacts analyses. The procedures for each of the potentially required impacts analyses will be discussed as well as the circumstances that trigger each analysis.
The first modeling step for most air permitting projects is to model the proposed new and increased emissions of criteria pollutants and compare the predicted impacts to the significant impact levels (SILs). If model-predicted impacts from proposed project increases are less than the SILs, then it is concluded that those emissions have an insignificant air quality impact, and no further analysis is necessary. If model-predicted impacts from proposed project increases are above the SILs, then full PSD National Ambient Air Quality Standard (NAAQS) modeling and PSD increment modeling must be conducted for applicable pollutants and averaging periods. Since these analyses require surrounding sources of criteria pollutants to be included in the model, it is important to determine if these analyses will be required as early in the project as possible.
If a project is near a Class I area, it is important to note that there are separate Class I SILs PSD increment thresholds that are lower than the Class II thresholds. There are additional requirements for projects near Class I areas outlined in the Federal Land Managers’ Air Quality Related Values Work Group (FLAG) Phase I Report (Revised 2010). It is very important to determine as early in the project as possible if the project can screen out of the analyses outlined in this document as they can be very time consuming.
Finally, secondary formation of particulate matter less than 2.5 microns (PM2.5) must now be accounted for in modeling projects. In addition, an ozone analysis must be conducted if a proposed project is in an area designated attainment or unclassifiable. The EPA has established screening procedures that can be used for these analyses, and it is important to determine early if a proposed project can show compliance using these screening procedures. If they cannot, photochemical modeling may be required which can be time consuming and expensive.
