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Dallas-Fort Worth: Ozone History

Background and history of Dallas-Fort Worth (DFW) area compliance with the National Ambient Air Quality Standards (NAAQS) for ground-level ozone.

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Compliance with the Ozone NAAQS from 1990 to Present

Unlike the Houston-Galveston-Brazoria (HGB) and Beaumont–Port Arthur (BPA) areas, where industrial point sources account for a greater proportion of the total nitrogen oxide (NOX) emissions in the area, point sources account for only about one-tenth of the total NOX emissions in the DFW area. The majority of NOX emissions in the DFW area come from on-road mobile sources (cars and trucks) and non-road mobile sources (such as construction equipment, aircraft, and locomotives).

2015 Eight-Hour Ozone Standard (2015 to Present)

On October 1, 2015, the U.S. 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 ( 80 FR 65291 ). On June 4, 2018, EPA designated a nine-county DFW area including Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Tarrant, and Wise Counites as marginal nonattainment ( 83 FR 25776 ). Rockwall County, which is designated nonattainment for the 2008 eight-hour ozone NAAQS, was not included in the DFW 2015 eight-hour ozone nonattainment area and was designated attainment (for more information, visit the State Ozone Designation Recommendation webpage). Under a marginal classification, the DFW area was required to attain the 2015 eight-hour ozone standard by the end of 2020 to meet an August 3, 2021 attainment date.

On June 10, 2020, the commission adopted the Emissions Inventory (EI) SIP Revision for the 2015 Eight-Hour Ozone NAAQS to satisfy the federal Clean Air Act (FCAA), §172(c)(3) and §182(a)(1) emissions inventory reporting requirements for nonattainment areas under the 2015 eight-hour ozone standard, including the DFW area. On June 29, 2021, EPA published final approval of the EIs for the HGB, DFW, and Bexar County 2015 ozone nonattainment areas ( 86 FR 34139 ). On September 9, 2021, EPA published final approval of the nonattainment new source review and emissions statement portions of this SIP revision ( 86 FR 50456 ).

On October 7, 2022, EPA reclassified the nine-county DFW nonattainment area from marginal to moderate for the 2015 eight-hour ozone NAAQS, effective November 7, 2022 ( 87 FR 60897 ). Under a moderate classification, the DFW area is required to attain the 2015 eight-hour ozone standard by the end of 2023 to meet an August 3, 2024 attainment date.

On June 20, 2024, EPA reclassified the nine-county DFW nonattainment area from moderate to serious for the 2015 eight-hour ozone NAAQS, effective July 22, 2024 ( 89 FR 51829 ). Under the serious classification, the DFW area is required to attain the 2015 eight-hour ozone standard by the end of 2026 to meet an August 2, 2027 attainment date.

2008 Eight-Hour Ozone Standard (2008 to Present)

On March 27, 2008, EPA revised the primary and secondary eight-hour ozone standard to 0.075 ppm ( 73 FR 16436 ). On March 10, 2009, the governor recommended to EPA that Collin, Dallas, Denton, Ellis, Hood, Johnson, Kaufman, Parker, Rockwall, and Tarrant counties be designated nonattainment for the 2008 eight-hour ozone standard (see the governor's letter to EPA region 6 ). All of the counties except Hood were previously designated nonattainment under the 1997 eight-hour ozone standard (0.08 ppm).

In September 2009, 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 EPA withdraw the proposed reconsidered ozone standard.

In a memo dated September 22, 2011 from EPA Assistant Administrator Gina McCarthy, 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 October 31, 2011, the governor sent a revised recommendation to EPA that Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, and Tarrant Counties be designated nonattainment for the 2008 eight-hour ozone standard based on 2008 through 2010 air quality data (see the governor's revised recommendation ). EPA sent a letter to the governor on December 9, 2011, responding to the state’s recommendations for area designations under the 2008 eight-hour ozone standard (see the EPA's letter to the governor ). In that letter, EPA indicated that it intended to modify the state's recommended DFW nonattainment area designation to include Hood and Wise Counties.

On May 21, 2012, EPA published in the Federal Register final designations for the 2008 eight-hour ozone standard ( 77 FR 30088 ). A 10-county DFW area including Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, Tarrant, and Wise Counties was designated nonattainment and classified moderate under the 2008 eight-hour ozone standard, effective July 20, 2012. The DFW area includes the nine counties that were designated nonattainment under the 1997 eight-hour ozone standard in addition to Wise County. Hood County was designated attainment/unclassifiable. The attainment deadline for the DFW moderate nonattainment area was originally established as December 31, 2018.

On July 2, 2014, the commission adopted a SIP revision to satisfy the FCAA, §172(c)(3) and §182(a)(1) emissions inventory reporting requirements for the HGB and DFW nonattainment areas under the 2008 eight-hour ozone standard. EPA published direct final approval of this SIP revision in the February 20, 2015 Federal Register ( 80 FR 9204 ).

On December 10, 2014, the commission approved two proposed revisions to the Texas SIP for the DFW moderate nonattainment area for the 2008 eight-hour ozone standard: the DFW Attainment Demonstration SIP Revision for the 2008 Eight-Hour Ozone Standard (Non-Rule Project No. 2013-015-SIP-NR) and the DFW Reasonable Further Progress (RFP) SIP Revision for the 2008 Eight-Hour Ozone Standard (Non-Rule Project No. 2013-014-SIP-NR). The proposed Attainment Demonstration SIP revision also contained revisions to 30 TAC Chapter 115 and Chapter 117. Following proposal of these SIP revisions, the attainment date for the DFW 2008 eight-hour ozone moderate nonattainment area changed from December 31, 2018 to July 20, 2018, as a result of a December 23, 2014 D.C. Circuit Court ruling and EPA’s final 2008 ozone SIP requirements rule. Because the attainment year ozone season is the ozone season immediately preceding a nonattainment area’s attainment date, the attainment year for the DFW moderate nonattainment area also changed from 2018 to 2017.

Due to the timing of the court’s ruling and EPA’s subsequent rulemaking action, it was not possible to complete all work necessary for the DFW Attainment Demonstration SIP revision to demonstrate attainment in 2017. Therefore, the adopted DFW Attainment Demonstration SIP Revision for the 2008 Eight-Hour Ozone Standard included the work completed to date to demonstrate that the DFW nonattainment area would attain the 2008 eight-hour ozone NAAQS by 2018, as proposed, and also demonstrated progress toward attainment by the revised 2017 attainment year along with a commitment to develop a new Attainment Demonstration SIP revision for the DFW 2008 eight-hour ozone moderate nonattainment area for a 2017 attainment year. The DFW Attainment Demonstration SIP revision for the 2018 attainment year was adopted by the commission on June 3, 2015. The DFW 2008 Eight-Hour Ozone Attainment Demonstration SIP Revision for the 2017 Attainment Year was adopted by the commission on July 6, 2016.

In order to address the change in the attainment year in the DFW RFP SIP revision, the adopted DFW RFP SIP Revision for the 2008 Eight-Hour Ozone Standard  provided a required RFP analysis for the 2017 attainment year, including a contingency plan and a motor vehicle emissions budget (MVEB). The RFP SIP revision also demonstrated an 18% emissions reduction in ozone precursors from the 2011 base year through a 2018 attainment year, a 3% emissions reduction demonstration for contingency for each milestone year, and RFP MVEB for each milestone year, as proposed, in the event that the 2018 attainment year requirement was reinstated. The DFW RFP SIP revision was adopted by the commission on June 3, 2015. The 2017 Wise County RFP demonstration in the adopted DFW RFP SIP revision used a transfer of excess volatile organic compounds (VOC) reductions from the nine-county area previously designated as nonattainment to the newly designated Wise County. Upon notification that the option to transfer creditable VOC reductions between county groups was no longer available per the EPA's final 2008 Ozone Standard SIP Requirements Rule ( 80 FR 12264 ), TCEQ corrected the adopted DFW RFP analyses to remove the VOC reduction transfer and credit emission reductions from drilling rig controls that were available but had not been credited. The corrections were submitted to EPA in an April 22, 2016 technical supplement . EPA approved the DFW RFP SIP revision on December 7, 2016 ( 81 FR 88124 ).

On October 5, 2017, EPA published proposed approval of VOC Reasonably Available Control Technology (RACT) ( 82 FR 46450 ) and published final approval on December 21, 2017 ( 82 FR 60546 ).

On September 22, 2017, EPA published final conditional approval of the NOX RACT for the DFW 2008 Eight-Hour ozone standard nonattainment area with an effective date of October 23, 2017 ( 82 FR 44320 ). On August 8, 2018, the commission adopted the DFW 2008 Eight-Hour Ozone Standard Nonattainment Area RACT Update SIP revision (Non-Rule Project No. 2017-001-SIP-NR) to address EPA’s final conditional approval through a voluntary Agreed Order No. 2017-1648-SIP (Non-Rule Project No. 2018-010-SIP-NR), with TXI Operations, LP. On February 22, 2019 the EPA published a final action to approve the DFW RACT Update SIP revision and to convert the September 22, 2018 conditional approval to full approval ( 84 FR 5601 ).

On February 16, 2018, the U.S. Court of Appeals for the D.C. Circuit issued an opinion in the case South Coast Air Quality Management District vs. EPA, 882 F.3d 1138 (D.C. Cir. 2018) . The court's decision vacated parts of EPA's final 2008 eight-hour ozone standard SIP requirements rule, including the redesignation substitute, removal of anti-backsliding requirements for areas designated nonattainment under the 1997 eight-hour ozone NAAQS, waiving requirements for transportation conformity for maintenance areas under the 1997 eight-hour ozone NAAQS, and elimination of the requirement to submit a second 10-year maintenance plan. In response to the ruling, the commission adopted the DFW Redesignation Request and Maintenance Plan for the One-Hour and 1997 Eight-Hour Ozone Standards SIP Revision on March 27, 2019. See the 1997 Eight-Hour Ozone Standard and the One-Hour Ozone Standard sections below for more information.

On August 23, 2019, EPA reclassified the 10-county DFW nonattainment area from moderate to serious for the 2008 eight-hour ozone NAAQS, effective September 23, 2019 ( 84 FR 44238 ). The attainment date for serious nonattainment areas was July 20, 2021 with a 2020 attainment year. On March 4, 2020, the commission adopted the DFW Serious Classification Attainment Demonstration SIP Revision for the 2008 Eight-Hour Ozone NAAQS and the DFW and HGB Serious Classification RFP SIP Revision for the 2008 Eight-Hour Ozone NAAQS. The SIP revisions were submitted to EPA on May 13, 2020. Serious classification attainment demonstration and RFP SIP revisions were due to the EPA by August 3, 2020. On October 9, 2020, EPA proposed approval of the RFP SIP revision ( 85 FR 64084 ).

On June 20, 2021, the commission adopted the Chapter 115 VOC RACT Rules to address EPA's 2016 Oil and Natural Gas Industry Control Techniques Guidelines (CTG) for the DFW 2008 eight-hour ozone nonattainment area.

On March 25, 2021, TCEQ submitted the 2008 Eight-Hour Ozone NAAQS Milestone Compliance Demonstration for the 2020 Calendar Year for the DFW serious nonattainment area. EPA responded with a letter of adequacy on July 1, 2021.

On October 7, 2022, EPA reclassified the 10-county DFW nonattainment area from serious to severe for the 2008 eight-hour ozone NAAQS, effective November 7, 2022 ( 87 FR 60926 ). Under a severe classification, the DFW area is required to attain the 2008 eight-hour ozone standard by the end of 2026 to meet a July 20, 2027 attainment date.

1997 Eight-Hour Ozone Standard (1997 to 2015)

In July 1997, EPA announced a revised NAAQS for ground-level ozone. EPA phased out and replaced the previous one-hour standard with an eight-hour standard set at 0.08 ppm to protect the public health against longer exposure to this air pollutant. The eight-hour ozone standard became effective on September 16, 1997.

Effective June 15, 2004, Collin, Dallas, Denton, Tarrant, Ellis, Johnson, Kaufman, Parker, and Rockwall Counties were designated nonattainment for the 1997 eight-hour ozone standard. The area was classified moderate nonattainment for the standard, with an attainment deadline of June 15, 2010.

To satisfy the requirements of Phase I of the 1997 eight-hour ozone standard implementation rule ( 69 FR 23951 ), TCEQ adopted the DFW Eight-Hour Ozone Five Percent Increment of Progress SIP Revision on April 27, 2005 and submitted it to EPA. The revision used a 5% increment of progress from the area’s 2002 emissions baseline beyond the reductions from federal and state measures already approved by EPA and was the first DFW SIP revision submitted under the 1997 eight-hour ozone standard.

In May 2007, TCEQ submitted attainment demonstration and RFP SIP revisions for the DFW area to the EPA. The May 2007 DFW Attainment Demonstration SIP included a plan for DFW compliance with the 1997 eight-hour ozone standard by June 15, 2010 (based on 2009 ozone season monitoring). The RFP SIP revision demonstrated 15% total NOX and VOC emissions reductions between 2002 and 2008, as required. The attainment demonstration and RFP SIP revisions relied on photochemical modeling and weight of evidence (WoE) analyses that examined qualitative and other factors that could not be directly included in the models, but that nevertheless supported the projected attainment by 2010. On March 21, 2008, EPA found the on-road motor vehicle emissions budget (MVEB) contained in the DFW attainment demonstration adequate for transportation conformity purposes ( 73 FR 15152 ).

TCEQ provided supplemental information pertaining to the attainment demonstration to EPA on April 23, 2008 ( see TCEQ’s letter ). After the attainment demonstration was supplemented, it was revised in November 2008 (contingency plan revisions), and again revised in December 2008 (Discrete Emissions Reduction Credit (DERC) program revisions).

EPA approved the May 2007 DFW RFP SIP revision (which included an updated MVEB and emissions inventory) on October 7, 2008 ( 73 FR 58475 ).

On January 14, 2009, EPA published final conditional approval ( 74 FR 1903 ) of components of the attainment demonstration, including the original May 2007 DFW 1997 Eight-Hour Ozone Attainment Demonstration SIP Revision, the April 23, 2008 supplement, and the November 2008 DFW Attainment Demonstration Contingency Plan SIP Revision. This was the first attainment demonstration SIP revision in the U.S. for the 1997 eight-hour ozone standard to receive approval from EPA. The DERC Program SIP revision component submitted in December 2008 was not included in EPA’s conditional approval but was later approved on May 11, 2017 ( 82 FR 21919 ). The January 14, 2009 action included:

  • Conditional approval of the 2009 attainment MVEBs, Reasonably Available Control Measures (RACM) demonstration, and failure-to-attain contingency plan.
  • Full approval of local Voluntary Mobile Source Emission Reduction Plan (VMEP) and Transportation Control Measures (TCM).
  • Full approval of the VOC Reasonably Available Control Technology (RACT) demonstrations for the one-hour and 1997 eight-hour ozone standards.
  • A statement that all control measures and reductions relied upon to demonstrate attainment have been approved by EPA.

On March 10, 2010, TCEQ adopted the DFW RACT, Chapter 117 Rule, and Contingency Plan SIP Revision to: (1) address several CTGs issued by EPA between 2006 and 2008, (2) expand a specific exemption from NOX control requirements and demonstrate that the expansion would not interfere with attainment, and (3) revise the contingency measure plan to reflect the two rule changes included with the 2007 DFW attainment demonstration SIP revision. Based on the revised RACT analysis, the offset lithographic rules that had been contingency measures for the area were made full control measures and were removed from the contingency plan. Emissions reductions from fleet turnover that were not already used for the contingency plan were used to replace the reductions removed from the contingency plan from adoption of offset lithographic controls and expansion of the NOX control exemption.

On August 10, 2010, TCEQ adopted the Environmental Speed Limit (ESL) Control Strategy Conversion to a TCM SIP Revision . Conversion of the DFW-area ESL strategy to a TCM was made to allow increased flexibility for local air quality planners to change ESLs in the area. With adoption of this SIP revision, future changes to ESLs may be accomplished through a TCM substitution process, which is the responsibility of local air quality planners, instead of through a formal revision of the DFW SIP. The conversion of the ESL strategy to a TCM is consistent with the MVEB submitted in the 2007 DFW attainment demonstration SIP revision.

Effective January 19, 2011, EPA published a final determination of failure to attain and reclassification of the DFW area from a moderate to a serious nonattainment area for the 1997 eight-hour ozone standard ( 75 FR 79302 ). EPA set January 19, 2012 as the deadline for Texas to submit attainment demonstration and RFP SIP revisions addressing the serious ozone nonattainment area requirements of the FCAA.

On December 7, 2011, TCEQ adopted the 2011 DFW 1997 Eight-Hour Ozone Attainment Demonstration SIP Revision and the 2011 DFW 1997 Eight-Hour Ozone RFP SIP Revision . The 2011 attainment demonstration SIP revision demonstrated that the state’s control strategy would result in the area’s attainment of the 1997 eight-hour ozone standard by 2012, the attainment year for serious nonattainment areas. As required by EPA, the 2011 attainment demonstration SIP revision included an MVEB, a VOC and NOX RACT analysis, a RACM analysis, and a contingency plan. The 2011 attainment demonstration SIP revision also described revisions to 30 TAC Chapter 115, Subchapter E and 30 TAC Chapter 115, Subchapter B, Division 1. The 2011 attainment demonstration SIP revision used EPA’s Motor Vehicle Emissions Simulator (MOVES) model to develop the on-road mobile emissions inventory and attainment year MVEB.

The 2011 RFP SIP revision demonstrated that an emissions reduction of at least 3% per year would occur between milestone years 2011 and 2012. The 2011 RFP SIP revision established baseline emission levels, calculated reduction targets, identified control strategies to meet emission target levels, and tracked actual emission reductions against established emissions growth. The 2011 RFP SIP revision also included an MVEB for each milestone year as well as a contingency plan. As with the 2011 attainment demonstration SIP revision, the 2011 RFP SIP revision used EPA’s MOVES model to develop the base year and milestone year on-road mobile emissions inventories and the milestone year MVEBs. EPA published final approval of the 2011 DFW RFP SIP revision on November 12, 2014 ( 79 FR 67068 ).

On May 20, 2014, the Sierra Club filed a lawsuit against EPA for failure to take final action on certain DFW SIP submittals for the 1997 eight-hour ozone standard, and for failure to reclassify the DFW area for failing to attain the 1997 eight-hour ozone standard by the June 15, 2013 attainment date. On November 7, 2014, notice of a proposed consent decree was published in the Federal Register to address the Sierra Club’s lawsuit ( 79 FR 66368 ) and was entered with the court on January 23, 2015. The consent decree provided that EPA propose a determination of whether the area attained the 1997 eight-hour ozone NAAQS within 15 days after the entry of the consent decree with the court. EPA published a proposal to reclassify the serious DFW nonattainment area to severe for the 1997 eight-hour ozone standard on February 17, 2015 ( 80 FR 8274 ). However, the consent decree provided that if the 1997 eight-hour ozone standard was revoked and effective prior to finalization of the reclassification, the reclassification would not be finalized. The 1997 eight-hour ozone standard was revoked for all purposes in the EPA’s final 2008 ozone standard SIP requirements rule which was published on March 6, 2015 ( 80 FR 12264 ). The effective date of the revocation was April 6, 2015 and the reclassification was not finalized.

The consent decree also provided that EPA take action on the outstanding 2011 DFW 1997 Eight-Hour Ozone Attainment Demonstration SIP Revision by August 31, 2015. On April 28, 2015, EPA published a proposal to disapprove the DFW serious area attainment demonstration SIP revision for the 1997 eight-hour ozone NAAQS ( 80 FR 23487 ). In the same notice, EPA also proposed to determine that the DFW area is currently attaining the 1997 ozone NAAQS based on 2012 through 2014 monitoring data. Upon finalization of this proposed determination, the requirements for the DFW area to submit an attainment demonstration, a reasonable further progress (RFP) plan, contingency measures, and other planning SIPs related to attainment of the 1997 ozone NAAQS would be suspended for so long as the area continues to attain the 1997 eight-hour ozone NAAQS. On September 1, 2015, EPA finalized the determination of attainment for the DFW 1997 eight-hour ozone nonattainment area ( 80 FR 52630 ). A revised serious area attainment demonstration for the 1997 eight-hour ozone standard will not be required due to the EPA’s determination of attainment.

In EPA’s 2008 ozone standard SIP requirements rule, EPA included a mechanism for lifting anti-backsliding obligations under a revoked ozone NAAQS, which are not lifted by a determination of attainment. According to the rule, a state can provide a showing, termed a redesignation substitute, based on FCAA, §107(d)(3)(E) redesignation. TCEQ submitted a DFW Redesignation Substitute demonstration for the one-hour and 1997 eight-hour ozone standards to EPA in the form of a letter and attached report on August 18, 2015. On November 8, 2016, EPA published its final approval of the DFW area redesignation substitute for the one-hour ozone and 1997 eight-hour ozone NAAQS ( 81 FR 78688 ). The effective date of the rule is December 8, 2016.

On March 27, 2019, the commission adopted the DFW Redesignation Request and Maintenance Plan for the One-Hour and 1997 Eight-Hour Ozone Standards SIP Revision in response to the South Coast Air Quality Management District vs. EPA, 882 F.3d 1138 (D.C. Cir. 2018) ruling. The SIP revision was submitted to EPA on April 5, 2019 and includes a request that the DFW area be formally redesignated to attainment for the 1997 eight-hour ozone NAAQS. On April 6, 2020, EPA published final action on the SIP revision ( 85 FR 19096 ). The final rule terminates all anti-backsliding obligations for the DFW area for the 1997 eight-hour ozone NAAQS and approves the maintenance plan. The action did not redesignate the area to attainment, because EPA has taken the position that it lacks the authority to redesignate areas to attainment under revoked standards.

One-Hour Ozone Standard

Note: In 1997, the one-hour ozone standard was replaced by the more protective eight-hour ozone standard. On June 15, 2005, the one-hour standard was revoked for all areas, although some former one-hour ozone nonattainment areas have continuing obligations to comply with the anti-backsliding requirements described in 40 Code of Federal Regulations (CFR) §51.905(a).

The 1990 FCAA Amendments authorized EPA to designate areas failing to meet the NAAQS for ozone as nonattainment and to classify them according to severity. EPA designated four DFW area counties (Dallas, Denton, Collin, and Tarrant) moderate nonattainment of the one-hour standard of 0.12 ppm. In September 1994, TCEQ submitted to EPA an attainment demonstration SIP revision focused on controlling VOC emissions. The DFW area did not attain the one-hour ozone standard by the November 15, 1996 attainment deadline.

On February 18, 1998, EPA reclassified the four-county area to serious nonattainment, with a new attainment deadline of November 15, 1999. TCEQ submitted a 9% rate-of-progress SIP revision to EPA, but there was not enough time to implement rules to achieve necessary reductions by the attainment deadline. In April 2000, TCEQ adopted a full attainment demonstration including rules to attain the one-hour standard. That attainment demonstration SIP revision took into account the importance of local reductions in emissions of NOX and the transport of ozone and its precursors (NOX and VOC) from the HGB area. Based on photochemical modeling demonstrating that ozone and precursors transported from HGB were impacting DFW area ozone concentrations, TCEQ requested an extension of the DFW area's attainment date to November 15, 2007.

In July 1997, EPA announced a revised NAAQS for ground-level ozone. EPA phased out and replaced the previous one-hour standard with an eight-hour standard to protect public health against longer exposure to this air pollutant. EPA rules (Phase I) implementing the new eight-hour standard and revoking the one-hour standard ( 69 FR 23951 ) were issued in April 2004. Designated nonattainment area classifications determined what one-hour ozone requirements remained in effect. Areas not attaining the one-hour standard, including DFW, were required to comply with the one-hour standard until attained. The four DFW area counties remained subject to the one-hour standard.

EPA does not redesignate areas under a revoked standard, but may issue determinations of attainment, which allow areas to suspend requirements for additional SIP-submission requirements under the one-hour standard. On October 16, 2008, EPA issued a determination that the DFW four-county one-hour ozone area had attained the one-hour NAAQS based on verified 2004 through 2006 monitoring data, further supported by data from 2007 and 2008 ( 73 FR 61357 ). Requirements for this area to submit an attainment demonstration or 5% increment-of-progress plan, an RFP plan, contingency measures, and other planning SIP revisions related to one-hour ozone NAAQS attainment are suspended as long as the area continues to meet the standard.

In EPA’s 2008 ozone standard SIP requirements rule, EPA included a mechanism for lifting anti-backsliding obligations under a revoked ozone NAAQS, which are not lifted by a determination of attainment. According to the rule, a state can provide a showing, termed a redesignation substitute, based on FCAA, §107(d)(3)(E) redesignation. TCEQ submitted a DFW redesignation substitute demonstration for the one-hour and 1997 eight-hour ozone standards to EPA in the form of a letter and attached report on August 18, 2015. On November 8, 2016, EPA published its final approval of the DFW area redesignation substitute for the one-hour ozone and 1997 eight-hour ozone NAAQS ( 81 FR 78688 ). The effective date of the rule is December 8, 2016.

On April 5, 2019, TCEQ submitted the DFW Redesignation Request and Maintenance Plan for the One-Hour and 1997 Eight-Hour Ozone Standards SIP Revision to EPA in response to the South Coast Air Quality Management District vs. EPA, 882 F.3d 1138 (D.C. Cir. 2018) ruling. The SIP revision includes a request that the DFW area be formally redesignated to attainment for the one-hour ozone NAAQS. On April 6, 2020, EPA published final action on the SIP revision ( 85 FR 19096 ). The final rule terminates all anti-backsliding obligations for the DFW area for the one-hour ozone NAAQS and approves the maintenance plan. The action did not redesignate the area to attainment, because EPA has taken the position that it lacks the authority to redesignate areas to attainment under revoked standards.

Comprehensive History of the Texas SIP

This SIP History gives a broad overview of the SIP revisions that have been submitted to 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.