ENV-11-19 Proliferation of CMAQ Model Applications in the Era of Rapidly Changing NAAQS Landscape

Description:

The Community Multi-scale Air Quality (CMAQ) modeling system is a complex model for large scale simulations of atmospheric processes and air quality, including ozone, PM2.5, air toxics, acid deposition, and visibility degradation. It is a state-of-the-science model that is being more and more frequently used for regulatory applications. Its initial regulatory application was in the development of State Implementation Plans (SIP) for ozone non-attainment areas. A recent trend with regulatory agencies has been to expand its applications into more regulatory arenas such as PM2.5 attainment and air toxics modeling. EPA even considered having CMAQ essentially embedded in the NOx/SOx Secondary National Ambient Air Quality Standards (NAAQS). With the increasing role of the CMAQ, it is advisable for environmental managers to become knowledgeable on the nature of CMAQ, its capabilities, and its limitations. Understanding these characteristics of CMAQ may help the refining and petrochemical industries provide more rigorous comments during rulemaking processes, SIP development, and future permitting efforts. This paper provides a high level review of CMAQ, the recent trend of its applications, and reported model validation results. Based on these characteristics, discussions are offered to address appropriateness of expanding this model‘s application into some important regulatory processes and implications of such expansion from the perspective of facility environmental managers.