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Ozone Data Exceptional Event Flag Demonstrations

This page provides background information on exceptional events, the approach taken by TCEQ to document an exceptional event in El Paso that occurred in 2015, as well as a proposed exceptional event in Houston that occurred in 2011.

Exceptional events are unusual or naturally occurring events that affect air quality and are not reasonably controllable or preventable. Under Section 319 of the Federal Clean Air Act, states are responsible for identifying air quality monitoring data affected by an exceptional event and requesting that the United States Environmental Protection Agency (EPA) exclude the data from consideration when determining whether an area is in attainment or nonattainment of a National Ambient Air Quality Standard (NAAQS). The EPA has promulgated an exceptional event rule, codified at 40 CFR 50.1, 50.14 and 51.930), and guidance to implement the requirements of the Federal Clean Air Act regarding exceptional events.

More information on exceptional events and the applicable regulations can be found at EPA’s website: Treatment of Air Quality Data Influenced by Exceptional Events Exit the TCEQ

The Texas Commission on Environmental Quality (TCEQ) has identified natural (wildfire) events that led to high concentrations of ozone in El Paso on one day in 2015. The proposed flag is for wildfire events that are described in more detail in the demonstration document for El Paso provided below.

The TCEQ complied with federal regulations regarding public notice and comment, and the demonstration documents supporting the TCEQ proposed exceptional event flags for El Paso ozone data for 2015 were posted for 30-day public review and comment periods. The public review and comment period for the 2015 El Paso Exceptional Events Document closed on September 26, 2016.
The public comments received by the TCEQ on the proposed flags were forwarded to the EPA for consideration. The EPA considered information provided in the demonstration documents and public comments when deciding whether to accept or reject the proposed flag.

On December 15, 2017, EPA Region 6 notified the TCEQ of its concurrence. The EPA concurrence flag in the EPA Air Quality System database will remove the data from consideration for determinations of compliance with the 8-hour ozone National Ambient Air Quality Standard (NAAQS).

Approved Exceptional Events

El Paso Ozone Exceptional Event: June 21, 2015

Proposed Exceptional Events

Houston Exceptional Event: August 26, 2011

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