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Air Quality Permit Modeling

National Information

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New Source Review Permits

A New Source Review (NSR) permit is a construction permit given to a source that is either building a new facility or significantly modifying an existing facility and emitting large amounts of regulated air pollutants. There are two types of NSR permits: nonattainment area (NAA) permits and Prevention of Significant Deterioration (PSD) permits. Which type of permit a source needs depends on its location and the pollutants it will emit. It is possible for a source to need both a PSD and an NAA permit. In either case, an ambient air quality modeling assessment of the impact of the new or modified source is required to ensure compliance with the Prevention of Significant Deterioration (PSD) increment levels and the National Ambient Air Quality Standards (NAAQS), and to ensure acceptable impacts to other air quality related attributes.


Permit Issuing Agency

In most cases a state, tribal, or local government agency has the authority to issue NSR permits. EPA only issues NSR permits if the state, tribal, or local agency has no approved NSR permitting authority. All NSR permits in Region 4 are currently issued by state or local agencies.


EPA's role in the NSR permitting

Region 4 receives copies of NSR permit applications from our regional permitting agencies. Based on the type of sources, expected ambient impacts, and resources available, Region 4 will review the NSR permit application and provide our comment to the permitting agency as early in the permitting process as feasible - either in the agency's application review phase or subsequent to the agency issuing a draft permit for public comment. It should be noted that if our review only occurs after the draft permit is issued for public comment, EPA always has the same 30-day comment period as the rest of the public. Region 4's main role in the NSR permitting process is to oversee the issuance of NSR permits by regional permitting agencies. This ensures that the NSR permits are based on complete and technically sound permit applications, they adhere to currently accepted national and regional guidance, and they adhere to the requirements of Clean Air Act.

Role of Air Quality Modeling

Required components of a PSD permit application include an Air Quality Analysis (i.e., demonstration of compliance with NAAQS and PSD increments), Additional Impact Analysis (i.e., assessment of impacts from project-caused growth to soils, vegetation, and visibility), and a Class I Area Impact Analysis (i.e., PSD increment compliance and impacts to visibility and air quality related values). An NAA permit application must also contain a Class I Area Impact Assessment similar to that required for PSD, as well as a demonstration that the project will provide a net air quality benefit in the area affected by the project. All of these components of NSR permit applications are based on ambient air quality modeling.


For information on the contents of this page contact Amanetta Somerville .

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