PSD vs. Nonattainment NSR vs. minor NSR

One program, three parts

New Source Review (NSR) is the Clean Air Act's preconstruction permitting program. It has three parts: Prevention of Significant Deterioration (PSD) for major sources in areas that meet the national ambient air quality standards, Nonattainment NSR for major sources in areas that do not, and minor NSR for everything else.

Most states run all three through their own approved programs. Where a state does not have an approved PSD program, the federal rule at 40 CFR 52.21 applies.

Area designations decide PSD or Nonattainment NSR

Designations are made pollutant by pollutant. The same county can be in attainment for one pollutant and nonattainment for another, so a single project can trigger PSD for some pollutants and Nonattainment NSR for others. EPA's Green Book lists current nonattainment areas.

What PSD requires

A PSD permit generally requires:

• Best Available Control Technology (BACT), determined case by case
• An air quality analysis showing the project will not cause or contribute to a violation of the standards or allowable increments
• Additional impacts analysis (for example soils, vegetation, and visibility), including review for nearby Class I areas
• Public notice and comment

What Nonattainment NSR requires

A Nonattainment NSR permit generally requires:

• Lowest Achievable Emission Rate (LAER)
• Emission offsets from other sources in the area
• Certification that the owner's other major sources in the state comply with applicable requirements
• An alternatives analysis showing benefits outweigh costs

Minor NSR

Federal rules at 40 CFR 51.160 through 51.164 require states to review new and modified sources that are not major, but leave the design to each state. That is why minor NSR looks so different from state to state: exemptions, permits by rule, general and standard permits, registrations, and case-by-case permits are all forms of minor NSR.

Major modifications

For existing major sources, the question is whether a change is a major modification. That turns on the emissions increase from the project and, in some cases, the net change at the source, using the calculation tests in the rule. Read the definitions and the applicability procedures in the program that applies before calculating.