ENV-08-007 New Permitting Challenges: PM2.5 NAAQS and PSD Increment Modeling

Description:

In 1997, EPA promulgated a National Ambient Air Quality Standard (NAAQS) for PM2.5, but EPA determined at that time that appropriate dispersion modeling procedures, emission inventories, and baseline measurements were not yet developed for PM2.5. Therefore, EPA issued a memorandum1 indicating that modeling for PM10 compliance with the NAAQS was to be used as a surrogate for indicating PM2.5 compliance with its NAAQS until further notice. About 10 years later, EPA finally issued guidance2 for modeling of New Source Review emissions for compliance with the PM2.5 NAAQS. EPA also issued proposed3 PSD increments, Significant Impact Levels, and Significant Monitoring Concentrations for PM2.5. The surrogate policy will end between 2009 and 2011, depending upon the state, after the promulgation of the PM2.5 New Source Review Implementation Rule and the Increment Rule, and then after any required State Implementation Plan changes for SIP-approved states.