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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.

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 Dallas-Fort Worth (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).

2008 Eight-Hour Ozone Standard (2008 to Present)

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

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 memo dated September 22, 2011 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 October 31, 2011, the governor sent a revised recommendation to the 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) Exit the TCEQ. The 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) Exit the TCEQ. In that letter, the 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, the EPA published in the Federal Register final designations for the 2008 eight-hour ozone standard (77 FR 30088Exit the TCEQ. A ten-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 is December 31, 2018.

1997 Eight-Hour Ozone Standard (1997 to Present)

In July 1997, the EPA announced a revised NAAQS for ground-level ozone. The 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), Exit the TCEQ the TCEQ adopted the DFW Eight-Hour Ozone Five Percent Increment of Progress SIP Revision on April 27, 2005 and submitted it to the 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 the EPA, and was the first DFW SIP revision submitted under the 1997 eight-hour ozone standard.

In May 2007, the TCEQ submitted attainment demonstration and reasonable further progress (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 volatile organic compound (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, the EPA found the on-road motor vehicle emissions budget (MVEB) contained in the DFW attainment demonstration adequate for transportation conformity purposes (73 FR 15152) Exit the TCEQ.

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

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

On January 14, 2009, the EPA published final conditional approval (74 FR 1903) Exit the TCEQ of components of the attainment demonstration, including the orignal 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 the EPA. The DERC Program SIP revision component submitted in December 2008 was not included in the EPA’s conditional approval, and remains under review. The EPA approval 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 the EPA.

On March 10, 2010, the TCEQ adopted the DFW RACT, Chapter 117 Rule, and Contingency Plan SIP Revision to: (1) address several CTGs issued by the 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, the 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, the 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) Exit the TCEQ. The 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 Federal Clean Air Act.

On December 7, 2011, the 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 the 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 the 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 the EPA’s MOVES model to develop the base year and milestone year on-road mobile emissions inventories and the milestone year MVEBs.

One-Hour Ozone Standard (1990 to 2008)

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).

The 1990 Federal Clean Air Act Amendments authorized the EPA to designate areas failing to meet the NAAQS for ozone as nonattainment and to classify them according to severity. The 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, the TCEQ submitted to the 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, the EPA reclassified the four-county area to serious nonattainment, with a new attainment deadline of November 15, 1999. The TCEQ submitted a 9% rate-of-progress SIP revision to the EPA, but there was not enough time to implement rules to achieve necessary reductions by the attainment deadline. In April 2000, the 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 Houston-Galveston-Brazoria (HGB) area. Based on photochemical modeling demonstrating that ozone and precursors transported from HGB were impacting DFW area ozone concentrations, the TCEQ requested an extension of the DFW area's attainment date to November 15, 2007.

In July 1997, the EPA announced a revised NAAQS for ground-level ozone. The 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) Exit the TCEQ 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.

The EPA no longer redesignates areas under the one-hour 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, the 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). Exit the TCEQ 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.

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.