Ozone Data Exceptional Event Flag Demonstrations
Exceptional events are unusual or naturally occurring events that affect air quality and are not reasonably controllable or preventable. States can request that the United States Environmental Protection Agency (EPA) exclude air quality monitoring data affected by an exceptional event from consideration in determining the attainment or nonattainment status of a National Ambient Air Quality Standard (NAAQS). The demonstration documents below were developed in support of the Texas Commission on Environmental Quality’s (TCEQ) proposed exceptional event flags.
Exceptional event regulations and guidance are provided on EPA's Treatment of Air Quality Data Influenced by Exceptional Events website.
El Paso Ozone Exceptional Event: June 21, 2015
Exceptional Events Demonstration Document
for the University of Texas El Paso (CAMS 12) Monitoring Site
Addendum 1 – Memorandum: CAMx Modeling of June 21, 2015
- Addendum 2 – Wildfire Impacts on Ozone at the El Paso UTEP CAMS 12 Monitor on June 21, 2015: PowerPoint with Animations
Addendum 3 – Additional Information
Addendum 4 – Update - Trajectories and CAMx Modeling
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EPA Concurrence Letter to TCEQ
Dallas-Fort Worth Exceptional Event: August 16, 17, and 21, 2020
The TCEQ identified natural and human-caused wildfire events in Colorado and California that led to high concentrations of ozone at the Grapevine Fairway monitor in the Dallas-Fort Worth area on August 16, 17, and 21, 2020. The exceptional event demonstration package below describes the technical analyses that support the TCEQ’s conclusion and EPA's response.
Demonstration Documents
Exceptional Event Demonstration Document for the Grapevine Fairway (CAMS 70) Monitoring Site
(13 MB)
EPA response letter to TCEQ
Houston Exceptional Event: August 26, 2011
Related Topics
- TCEQ
Mitigation Plans for Exceptional Events in Texas
- TCEQ information on particulate matter exceptional event demonstrations
- TCEQ demonstrations on international transport to Texas nonattainment areas
- The NOAA Hazard Mapping System
shows the locations of fires and smoke plumes
- EPA’s AirNow website
provides information on smoke and fires throughout the country
- University of Maryland's US Air Quality Smog Blog
discusses air quality transport in different regions of the country
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NASA’s Worldview
web application shows interactive global satellite imagery
- TCEQ Index of Air Topics lists a wide range of programs and how the agency is working to improve air quality in Texas