Ozone Data Exceptional Event Flag Demonstrations
Demonstration documents supporting the proposed exceptional event flags for ozone data.
(Esta página en español. / This page in Spanish.)
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.
Current Exceptional Event Proposals
Houston Ozone Exceptional Events: June 20, September 13, September 21, and October 8, 2022
How to Submit a Comment
TCEQ posted this demonstration for written public comment on May 24, 2023. All comments received or postmarked by 5:00 PM Central Standard Time on June 24, 2023 will be submitted to the Environmental Protection Agency along with the final demonstration. No public hearing will be held for this action.
Comments on the demonstration should be emailed to amda@tceq.texas.gov, with a subject line containing “Houston area ozone Exceptional Event Demonstration 2022.”
Or mail comments to:
TCEQ Air Modeling and Data Analysis Section (Attn: Erik Gribbin)
MC164
P.O. Box 13087
Austin, TX 78711-3087
Approved Exceptional Events
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
- EPA Concurrence Letter to TCEQ
Previously Proposed Exceptional Events
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