1-Hour Nitrogen Dioxide NAAQS & how it can put brakes on your expansion plans!

National Ambient Air Quality Standards, or NAAQS, are “ceiling limit” of a pollutant in the atmosphere. A NAAQS limit is not-to-exceed concentration. If exceeded, the area becomes non-attainment for that pollutant and EPA mandates a State Implementation Plan (SIP) to correct this issue. Therefore, a modeling analysis is done when a new source is permitted.

For a major source, an applicant must submit a dispersion modeling report demonstrating that the limit will be met once the source is operating. This modeling report is reviewed by the state agency as well as the EPA regional office. For the minor sources, each state has its own policy and can be described as “case-by-case basis.”

Until recently, the modeling analysis was usually something only power plants, refineries, and huge manufacturing operations used to worry about. It all changed when EPA implemented the 1-hour not-to-exceed standard for nitrogen dioxide. Nitrogen Dioxide is a pollutant emitted from all the combustion sources and a 1-hr standard is something that impacts all permitted sources.

A very brief history…until April 2010, Nitrogen dioxide only had an annual standard (53 ppb).  Since then, all dispersion modeling reports were required to address the 1-hr nitrogen dioxide NAAQS limit (100 ppb). Also, it has become a well-documented fact that the emergency generators at major sources are challenging the permitting process due to their short stacks and high hourly nitrogen oxide emissions rate. Many emergency generators with short stacks have difficult time meeting the 1-hr NO2 standard.

Remember that NAAQS are “ceiling limit” never to be exceeded! So, if your facility has an emergency generator, or a “vintage” boiler, it is quite possible that you may be violating the nitrogen dioxide national standard without knowing about it. Each permitted facility can be required to demonstrate that they are not violating the NAAQS.  Next time you submit an application to permit a combustion source, the state agency can ask for a dispersion modeling report to demonstrate that the NAAQS for nitrogen dioxide, along with other pollutants, are being met.

It pays to be prepared. It is recommended that you discuss the issue with your environmental consultant. You may also owe an answer to the Responsible Official of your corporation. If you have any questions please contact Sam Joshi at (215) 389-2811.