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El Paso: Ozone History

Background and history of El Paso (ELP) area compliance with the National Ambient Air Quality Standards (NAAQS) for ground-level ozone.

Many of the SIP files on this page are hosted by the Texas Records and Information Locator (TRAIL) web archiveExit the TCEQ. If you need assistance with a file, please contact

2015 Eight-Hour Ozone Standard (2015 to Present)

On October 1, 2015, the United States Environmental Protection Agency (EPA) revised the primary and secondary eight-hour ozone standards to 0.070 parts per million (ppm). The 2015 eight-hour ozone NAAQS became effective on December 28, 2015 (application/pdf80 FR 65291Exit the TCEQ). On June 4, 2018, the EPA designated El Paso County as attainment/unclassifiable, effective August 3, 2018 (application/pdf83 FR 25776Exit the TCEQ).

In August 2018, the City of Sunland Park, New Mexico and environmental petitioners challenged the EPA’s attainment/unclassifiable designation for El Paso County. On July 10, 2020, the D.C. Circuit Court of Appeals issued its opinion to remand (without vacatur) the El Paso County attainment designation to the EPA and require the EPA to issue a revised El Paso County designation for the 2015 eight-hour ozone NAAQS as expeditiously as practicable. On December 21, 2020, the TCEQ submitted supplemental information to the EPA in support of retaining El Paso County’s original attainment designation. The EPA sent a application/pdf120-day letter to Texas on May 25, 2021 notifying the governor that the EPA intends to modify the designation for El Paso County to nonattainment as part of the existing Doña Ana partial-county (Sunland Park) ozone nonattainment area. On July 26, 2021, the TCEQ submitted a application/pdfresponse requesting that the EPA not modify El Paso County’s existing attainment/unclassifiable designation consistent with all the information submitted by the state.

On November 30, 2021, the EPA published a final nonattainment designation for the 2015 eight-hour ozone NAAQS for El Paso County, effective December 30, 2021 (application/pdf86 FR 67864Exit the TCEQ). The EPA expanded the Sunland Park marginal nonattainment area to include all of El Paso County and renamed the area as the “El Paso-Las Cruces, Texas-New Mexico nonattainment area."

2008 Eight-Hour Ozone Standard (2008 to Present)

On March 27, 2008, the EPA revised the primary and secondary eight-hour ozone standard to 0.075 ppm (application/pdf73 FR 16436Exit the TCEQ). On March 10, 2009, the governor recommended to the EPA that El Paso County be designated nonattainment for the 2008 ozone standard (see application/pdfthe governor's letter to EPA region 6Exit the TCEQ).

In September 2009, the EPA announced it would reconsider the 2008 NAAQS, and on January 19, 2010 proposed to lower the primary ozone standard to a range of 0.060–0.070 ppm, and proposed a separate secondary standard based on cumulative seasonal average ozone concentrations. On September 2, 2011, President Obama announced that he had requested the EPA withdraw the proposed reconsidered ozone standard.

In a application/pdfmemo dated September 22, 2011Exit the TCEQ from EPA Assistant Administrator Gina McCarthy, the EPA announced that it would proceed with initial area designations under the 2008 eight-hour ozone standard, starting with the recommendations states made in 2009 and updating them with the most current, certified air quality data (2008 through 2010).

On May 21, 2012, the EPA published in the Federal Register final designations for the 2008 eight-hour ozone standard (application/pdf77 FR 30088Exit the TCEQ). El Paso County was designated attainment/unclassifiable under the 2008 eight-hour ozone NAAQS, effective July 20, 2012.

On February 16, 2018, the United States Court of Appeals for the District of Columbia Circuit issued an opinion in the case application/pdfSouth Coast Air Quality Management District vs. EPA, 882 F.3d 1138 (D.C. Cir. 2018).Exit the TCEQ The court vacated portions of EPA's final 2008 eight-hour ozone standard SIP requirements rule, which revoked the 1997 eight-hour ozone NAAQS. In response to the ruling, the commission approved adoption of the application/pdfEl Paso Redesignation Request and Maintenance Plan for the One-Hour Ozone NAAQS SIP RevisionExit the TCEQ on April 24, 2019. The SIP revision was submitted to the EPA on May 10, 2019. See the One-Hour Ozone Standard section below for more information. 

1997 Eight-Hour Ozone Standard (1997 to 2015)

Note: Effective April 6, 2015, the 1997 eight-hour ozone standard has been revoked in all areas, although some former 1997 eight-hour ozone nonattainment areas have continuing obligations to comply with the anti-backsliding requirements described in 40 CFR §51.1100(o).

On April 15, 2004, the EPA designated El Paso County attainment (effective June 15, 2004) for the 1997 eight-hour ozone NAAQS of 0.08 ppm. Monitors in El Paso County at that time showed attainment of both the one-hour and eight-hour ozone NAAQS. The EPA’s Phase I Implementation Rule for the eight-hour ozone standard directed that areas designated nonattainment for the one-hour ozone standard but attainment for the eight-hour ozone standard submit a federal Clean Air Act (FCAA), §110(a)(1) maintenance plan for the 1997 eight-hour ozone standard by June 15, 2007. The TCEQ submitted this maintenance plan to the EPA on January 20, 2006. On January 15, 2009, the EPA proposed approval of the El Paso ozone maintenance SIP revision (application/pdf74 FR 2387Exit the TCEQ). The EPA did not receive any adverse comments regarding the maintenance plan approval; the plan became effective on March 16, 2009. 

One-Hour Ozone Standard

Note: In 1997, the one-hour ozone standard was replaced by the more protective eight-hour ozone standard. The one-hour standard has been revoked in all areas, although some former one-hour ozone nonattainment areas have continuing obligations to comply with the anti-backsliding requirements described in 40 CFR 51.905(a).

As a result of the FCAA amendments of 1990, El Paso County was designated nonattainment for the one-hour ozone NAAQS of 0.12 ppm. El Paso County was classified as a serious nonattainment area with an attainment deadline of November 15, 1999.  Plans to reduce emissions of volatile organic compounds by 15% in El Paso County were submitted in 1993 and 1994.

In September 1994, the Texas Natural Resource Conservation Commission (TNRCC), a predecessor to the TCEQ, adopted a application/pdf§818 demonstrationExit the TCEQ for the El Paso area. Section 818 of the 1990 FCAA amendments included a new FCAA, §179B, containing special provisions for nonattainment areas affected by emissions from outside the United States. Under §179B, the EPA could approve a SIP revision for the El Paso area if the plan would achieve timely attainment of the NAAQS but for emissions from Mexico. Modeling showed that El Paso could attain the NAAQS with the planned 15% reduction in emissions from the United States side of the border alone. On July 24, 1996, the TNRCC adopted the one-hour ozone application/pdfSUPER SIP revisionExit the TCEQ which included changes to the 15% rate of progress demonstration for the El Paso nonattainment area as well as changes to the §818 attainment demonstration.

On June 15, 2005, the EPA revoked the one-hour ozone standard. However, certain requirements for the one-hour standard remained in place after revocation to prevent air quality from degrading in former one-hour ozone standard nonattainment areas. On October 20, 2010, the EPA published a final rule clarifying the EPA’s approval of the 1997 eight-hour ozone maintenance plan regarding the lifting of one-hour ozone serious area anti-backsliding requirements for the El Paso area and determined that the approval of the FCAA, §110(a)(1) maintenance plan for the 1997 eight-hour ozone NAAQS removes the requirement for the continued application of one-hour anti-backsliding measures (application/pdf75 FR 64675Exit the TCEQ).

On May 10, 2019, the TCEQ submitted the application/pdfEl Paso One-Hour Ozone Redesignation Request and Maintenance Plan SIP RevisionExit the TCEQ to the EPA that includes a request that the El Paso area be formally redesignated to attainment for the one-hour ozone standard. The EPA has taken the position that it lacks the authority to redesignate areas to attainment under revoked standards. Therefore, on September 25, 2020 the commission approved to withdraw the SIP revision from EPA consideration (application/pdfNon-Rule Project No. 2020-040-SIP-NRExit the TCEQ).

Comprehensive History of the Texas SIP

This SIP History gives a broad overview of the SIP revisions that have been submitted to the EPA by the State of Texas. Some sections may be obsolete or superseded by new revisions but have been retained for the sake of historical completeness.