Modeling Clarification Memorandum for Secondary Pollutants and Nitrogen Dioxide
EPA has clarified that air quality “modeling,” referring to the use of air quality modeling techniques, databases, or computer models to assess impacts to the National Ambient Air Quality Standards, is sufficient and appropriate for a demonstration of General Conformity when following the EPA 2017 Guideline on Air Quality Models (the Guideline). Federal agencies may rely upon the recommendations in the Guideline for demonstrating conformity of secondarily formed criteria pollutants when their actions are proposed to occur within nitrogen dioxide (NO2), ozone (O3), or fine particulate matter (PM2.5) nonattainment or maintenance areas.
Historically, EPA has recommended that federal agencies not use air quality modeling to demonstrate General Conformity for these areas because the science and technology of the models, and their capabilities, were not sufficient to handle the complexities of photochemical reactions in the atmosphere from a relatively small source. Recent advances in modeling, and EPA’s innovative, alternative modeling techniques, can now support the use of air quality modeling to demonstrate General Conformity of these pollutants using the recommendations of the Guideline.
Read the Modeling Clarification Memorandum below.
