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Exceptional Event Mitigation Plans Request for Comments

High Wind PM10 Exceptional Events Mitigation Plan for the South Coast Air Basin and the Coachella Valley Portion of the Salton Sea Air Basin

What are exceptional events?

Every year, some air quality events occur that are not feasible to control or prevent. The Federal Clean Air Act allows for special treatment of events that are naturally caused, or events that are the result of human activity and are unlikely to occur again at a particular location. These events may be designated as “exceptional events” if the resulting emissions clearly cause high air pollutant concentrations. 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. If an air quality event meets the exceptional event criteria, 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 for determining attainment of the National Ambient Air Quality Standards.

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 must describe public notification and education programs; illustrate how we identify, study, and implement mitigation measures; and set up provisions for the review and evaluation of the plan. Based on the number of possible high wind events that caused high PM10­­­ concentrations between the years of 2013 and 2015, 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 is required. The South Coast AQMD 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 every exceptional events demonstration. The exceptional events mitigation plan is a common 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 our High Wind PM10 Exceptional Events Mitigation Plan by addressing:

Dr. Scott Epstein, Program Supervisor, Air Quality Assessment
Planning, Rule Development & Area Sources
South Coast AQMD
21865 Copley Drive
Diamond Bar, CA 91765
sepstein@aqmd.gov


Comments received before the end of the 30-day review period, September 17th, 2018 will be reviewed and addressed in the mitigation plan. Comments received after September 17th, 2018 will be reviewed, but will be addressed in future revisions of the mitigation plan.

Draft High Wind PM10 Mitigation Plan For Public Comment (PDF, 1.1MB)

Final High Wind PM10 Mitigation Plan Submitted to CARB on Sept 18 2018 (PDF, 1MB)

Where can I find more information?

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South Coast Air Quality Management District

21865 Copley Dr, Diamond Bar, CA 91765

909-396-2000

 

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