Particulate Matter Exceptional Events Mitigation Plan for the South Coast Air Basin and Coachella Valley
What are exceptional events?
Every year, some air quality events occur that are not reasonably controllable or preventable. If these events are naturally caused or are the result of human activity that is unlikely to occur again at a particular location, the federal Clean Air Act allows for special treatment.
The National Ambient Air Quality Standards specify a set of air quality levels that air districts must meet by specific deadlines. Since these standards are designed to guide regulatory decision-making, it may not be appropriate to include monitoring data influenced by exceptional events when determining compliance with these standards. If an air quality event meets the exceptional event criteria established by the U.S. EPA, South Coast AQMD may prepare an exceptional event demonstration and submit it to the U.S. EPA for consideration. If the U.S. EPA approves the demonstration, South Coast AQMD may exclude the air quality monitoring data measured during the event when determining attainment of the National Ambient Air Quality Standards. However, the air monitoring data collected during the event remains available to the public and still may be relevant for other applications and analyses. South Coast AQMD employs a wide-variety of strategies to help reduce exposure to poor air quality during these events with an air quality forecasting program, real-time air quality measurements, and several methods of notification/dissemination; details are presented in the Particulate Matter Exceptional Events Mitigation Plan for the South Coast Air Basin and Coachella Valley.
What is an exceptional events mitigation plan?
As part of a 2016 revision to the U.S. EPA rule addressing exceptional events, a plan is required for areas with known, recurring exceptional events. This exceptional events mitigation plan summarizes how the public health impacts of high concentrations caused by exceptional events are mitigated with specific measures. The mitigation plan describes public notification and education programs; illustrates how we identify, study, and implement mitigation measures; and sets up provisions for the review and evaluation of the plan. An exceptional events mitigation plan addressing high wind PM10 exceptional events in the South Coast Air Basin and the Coachella Valley portion of the Salton Sea Air Basin was required by U.S. EPA in 2018. An additional requirement for an exceptional event mitigation plan addressing wildfire-related and fireworks-related fine particle pollution events is due to U.S. EPA by April of 2024.
The Particulate Matter Exceptional Events Mitigation Plan for the South Coast Air Basin and Coachella Valley addresses exceptional events from wildfire smoke and fireworks and also serves as an update to the High Wind PM10 Exceptional Events Mitigation Plan for the South Coast Air Basin and the Coachella Valley portion of the Salton Sea Air Basin that was submitted to the California Air Resources Board in 2018. This exceptional events mitigation plan does not propose any new policies or measures.
Why publish an exceptional events mitigation plan?
In the past, much of the information required in the exceptional events mitigation plan was included in individual exceptional event demonstration. The exceptional events mitigation plan is a integrated platform to summarize all of our mitigation measures in a single document, satisfying the requirements established in the 2016 revision to the U.S. EPA rule addressing exceptional events.
How can I submit comments and provide feedback on the plan?
Interested persons may submit comments on the Particulate Matter Exceptional Events Mitigation Plan for the South Coast Air Basin and Coachella Valley by addressing:
Program Supervisor, Air Quality Assessment
Planning, Rule Development & Implementation
Diamond Bar, CA 91765
South Coast AQMD