South Coast Air Basin Redesignation Requests and Maintenance Plans for PM2.5 and PM10 NAAQS

The South Coast AQMD is required to attain the federal National Ambient Air Quality Standards (NAAQS) for particulate matter with an aerodynamic diameter less than 2.5 microns (PM2.5) and particulate matter with an aerodynamic diameter less than 10 microns (PM10) as expeditiously as possible. The Basin is currently designated as a moderate nonattainment area for the 1997 annual and 24-hour average PM2.5 NAAQS. Effective August 24, 2016, the United State Environmental Protection Agency (U.S. EPA) formally determined that the Basin is in attainment with the 1997 annual and 24-hour average PM2.5 NAAQS based on monitoring data from 2011 to 2013. Therefore, the South Coast AQMD is formally requesting the U.S. EPA to redesignate the Basin from moderate nonattainment to attainment for the 1997 annual and 24-hour average PM2.5 NAAQS. Pursuant to federal Clean Air Act (CAA) Section 107(d)(3)(E), South Coast AQMD has developed the South Coast Air Basin Redesignation Requests and Maintenance Plans for PM2.5 and PM10 National Ambient Air Quality Standards (proposed project), which include demonstrations that the Basin is expected to maintain its attainment status for the 1997 annual and 24-hour average PM2.5 NAAQS through 2039 and other required elements such as contingency provision. Relative to the 1987 24-hour average PM10 NAAQS, the Basin was originally designated as moderate nonattainment in 1990 and later reclassified as serious nonattainment in 1993. In 2010, South Coast AQMD submitted a request to U.S. EPA seeking a redesignation of attainment along with a first maintenance plan, which were effective on July 26, 2013. The Basin has since remained in attainment with this standard, provided that potential exceptional events like wind-blown dust and wildfires are excluded. Pursuant to federal CAA Section 175A(b), South Coast AQMD is required to submit a subsequent maintenance plan to ensure continued attainment of the standard for at least a 20-year period from the redesignation date. To satisfy this requirement, South Coast AQMD developed a second maintenance plan for the 1987 PM10 NAAQS, demonstrating that the Basin is expected to continue attaining the 1987 24-hour average PM10 NAAQS through 2033. The proposed project is an administrative exercise to fulfill U.S. EPA requirements and will benefit stakeholders by having improved clarity when implementing the applicable requirements for demonstrating and maintaining attainment with the applicable NAAQS.