Determination of Attainment by the Attainment Date; 1997 Ozone Standards; California; Coachella Valley

Determination of Attainment by the Attainment Date; 1997 Ozone Standards; California; Coachella Valley

SUPPLEMENTARY INFORMATION:

Throughout this document, "we," "us," and "our" refer to the EPA.

Table of Contents

I. Proposed Action

II. Public Comments and EPA Responses

III. EPA Action

IV. Statutory and Executive Order Reviews

I. Proposed Action

On January 15, 2026, the EPA proposed to determine that the Coachella Valley attained the revoked 1997 ozone national ambient air quality standards (NAAQS) of 0.08 parts per million (ppm) by its June 15, 2025 Extreme area attainment date. ⁽¹⁾ The EPA proposed these findings to fulfill our statutory obligation under Clean Air Act (CAA) section 181(b)(2) to determine whether an area has attained the relevant standards by the applicable attainment date. Previously, the EPA granted the nonattainment area a 1-year extension of the attainment date from June 15, 2024, to June 15, 2025. ⁽²⁾

II. Public Comments and EPA Responses

The EPA's proposed action provided a 30-day public comment period. During this period, we received comments from the Cabazon Band of Cahuilla Indians (CBCI). In their comment letter, the CBCI requested government-to-government consultation with the EPA on our proposed action prior to taking final action.

The EPA held a pre-consultation meeting with the CBCI after the close of the comment period and discussed the potential impacts of the proposed action. ⁽³⁾ Following this meeting, the CBCI notified the EPA they were no longer seeking formal consultation with the EPA. ⁽⁴⁾

Comment 1: The CBCI expressed concern that the EPA's determination would allow non-Tribal areas to increase allowable emissions thresholds for stationary sources. The CBCI were specifically concerned about less stringent permitting requirements for non-Tribal land due to the higher classification of the Tribal land. The CBCI also questioned the EPA's evaluation of this indirect impact on the Tribes of the Coachella Valley and asked the EPA to account for this regulatory asymmetry.

Response to Comment 1: The EPA's determination of attainment by the attainment date does not change the nonattainment classification for any Tribal or non-Tribal areas of the Coachella Valley for the 1997 ozone NAAQS.

If the EPA were to finalize approval of a future maintenance plan and redesignation to attainment for the Coachella Valley for the 1997 ozone NAAQS, the area would be redesignated from nonattainment to attainment, which would change the area's major source thresholds for permitting for the 1997 ozone standard. The EPA has not received a redesignation request and maintenance plan for the Coachella Valley 1997 ozone nonattainment area and is not taking such redesignation action at this time. We further note that any future redesignation to attainment for the 1997 ozone NAAQS would have little practical consequence on permitting thresholds in the Coachella Valley because the Coachella Valley would remain Extreme for the 2008 ozone NAAQS. Thus, applicable higher permitting thresholds would continue to apply.

As we stated in our proposal, the attainment finding would relieve the area's CAA section 182(c)(9) and 172(c)(9) requirements for contingency measures for the 1997 ozone NAAQS, which requires contingent emission control measures in the event a nonattainment area fails to attain the NAAQS by an applicable attainment date. In addition, the area is not required to implement CAA section 185, which calls for the collection of penalty fees in nonattainment areas that fail to attain a specific ozone NAAQS by the applicable attainment date.

Comment 2: The CBCI noted that they operate an air monitor along with the Twenty-Nine Palms Band of Mission Indians, and the CBCI adheres to Federal Reference Methods and Federal Equivalent Methods in operation of the ozone monitor. They asserted that the EPA should consider formally incorporating or validating Tribally-affiliated monitoring data to improve representativeness and confidence in future determinations.

Response to Comment 2: While 40 CFR part 58, appendix D establishes multiple monitoring objectives, one of these objectives is for the establishment of required ambient air quality monitoring stations that are used to determine compliance with the NAAQS. For this action, the EPA relies only on complete, quality-assured, and certified ambient monitoring data from approved regulatory State/Local Air Monitoring Stations (SLAMS) within the boundaries of Coachella Valley, in accordance with 40 CFR part 58 (see table 1 of this document). The CBCI monitor referenced by the Tribe is not an approved regulatory SLAMS site; therefore, data from the Tribe's monitor were not used for this attainment determination. Though not applicable for comparison to the NAAQS, the CBCI monitor measured ozone concentrations below the 1997 ozone NAAQS from 2022-2024. ⁽⁵⁾ Although the EPA only considers data from regulatory monitors for regulatory purposes, we acknowledge and appreciate the value of the non-regulatory monitors in providing timely information for AirNow.gov and public information purposes.

Comment 3: The CBCI asserted that the proposed rule relied on deficient monitors with a constrained timeframe, that the Indio-Armistad High School monitor did not collect data from 2022 or 2023, and that two more years of monitoring are required to create a valid three-year design value.

Response to Comment 3: Attainment determinations are based on complete, quality-assured, and certified ambient ozone data collected under 40 CFR part 58. For ozone, a design value is determined from the 3-year average ( i.e., 2022-2024) of the annual fourth-highest daily maximum 8-hour concentrations, calculated in accordance with 40 CFR part 50, appendix H, and using quality-assured and certified data that meet the requirements of that appendix.

Within the bounds of the Coachella Valley there are two active ozone SLAMS monitors, Indio-Amistad (Air Quality System (AQS) ID: 06-065-2007) and Palm Springs (AQS ID: 06-065-5001). In this case, the Indio-Amistad monitoring site did not produce a valid design value for the 2024 design value period (data years 2022-2024) because the monitor was relocated in 2022-2023 and did not collect valid data during the relocation. However, the Palm Springs monitor, historically the highest concentration site in the nonattainment area, had complete, quality-assured, and certified data and an attaining design value. As we stated in our proposal, the Indio-Amistad monitor has historically recorded lower concentrations than Palm Springs, ⁽⁶⁾ thus a valid attaining design value at the Palm Springs monitor is sufficient to support this attainment determination despite the absence of a valid design value at Indio-Amistad.

Comment 4: The CBCI suggested that the South Coast Air Quality Management District could not provide regulatory data to the EPA because the District is not on the list of regulators that correlate emissions data with applicable emissions limitations per 40 CFR 52.224.

Response to Comment 4: The EPA does not agree that 40 CFR 52.224 precludes our reliance on emissions data from the South Coast Air Quality Management District for this action. The EPA promulgated 40 CFR 52.224 in response to certain state implementation plans (SIPs)  ⁽⁷⁾ that contained confidentiality clauses that may have caused emission data to be withheld from the public, in violation of CAA 110(a)(2)(F)(iii). ⁽⁸⁾ All of California, including the South Coast Air Quality Management District, have since addressed the requirements of CAA 110(a)(2)(F)(iii) for many NAAQS, and the EPA has approved the California SIP as addressing both requirements of CAA 110(a)(2)(F)(iii) for the 1997 ozone NAAQS. ⁽⁹⁾

III. EPA Action

For the reasons discussed in the proposed rule and this document, we are finalizing our determination that the Coachella Valley has attained the revoked 1997 ozone NAAQS by its June 15, 2025 attainment date, based on quality-assured and certified ambient air quality monitoring data from 2022 through 2024.

IV. Statutory and Executive Order Reviews

This action:

• Is not a significant regulatory action subject to review by the Office of Management and Budget under Executive Order 12866 (58 FR 51735, October 4, 1993);
• Is not an Executive Order 14192 (90 FR 9065, February 6, 2025) regulatory action because this action is not significant under Executive Order 12866;

• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq. );

• Is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act (5 U.S.C. 601 et seq. );

• Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4);
• Does not have federalism implications as specified in Executive Order 13132 (64 FR 43255, August 10, 1999);
• Is not subject to Executive Order 13045 (62 FR 19885, April 23, 1997) because it approves a state program;
• Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355, May 22, 2001); and
• Is not subject to requirements of section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the CAA.

This action is subject to the Congressional Review Act (CRA), and the EPA will submit a rule report to each House of the Congress and to the Comptroller General of the United States. This action is not a "major rule" as defined by 5 U.S.C. 804(2).

Under section 307(b)(1) of the CAA, petitions for judicial review of this action must be filed in the United States Court of Appeals for the appropriate circuit by October 13, 2026. Filing a petition for reconsideration by the Administrator of this final rule does not affect the finality of this action for the purposes of judicial review, nor does it extend the time within which a petition for judicial review may be filed and shall not postpone the effectiveness of such rule or action. This action may not be challenged later in proceedings to enforce its requirements (see section 307(b)(2)).

For the reasons stated in the preamble, the EPA amends 40 CFR part 52 as follows:

PART 52-APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

Subpart F-California

⁽¹⁾  91 FR 1732 (Jan. 15, 2026).

⁽²⁾  90 FR 42844 (Sept. 5, 2025). This action relied upon excluded wildfire-driven exceedances of the 1997 ozone NAAQS at the Palms Springs-Fire Station monitoring site on July 14-15, 2023, under the Exceptional Events Rule.

⁽³⁾  See a summary of the discussion in the docket for this action (Docket No. EPA-R09-OAR-2025-3127-0050).

⁽⁴⁾  Email dated April 15, 2026, from Daniel Lopez-Tirado (CBCI) to Kathryn Harper (EPA), Subject "Re: Pre-Consultation Meeting."

⁽⁵⁾  Ambient ozone concentrations at the CBCI monitor were reported January 2022 to November 2023.

⁽⁶⁾  91 FR 1732, 1736.

⁽⁷⁾  SIPs are collections of regulations and documents used by a state, Tribe, or local air district to implement, maintain, and enforce the NAAQS and fulfill other CAA requirements.

⁽⁸⁾  See 40 FR 55326 (Nov. 28, 1975). CAA 110(a)(2)(F)(iii) contains two conditions: (1) that periodic reports on the nature and amounts of emissions and emissions-related data be correlated with the relevant emission limitations, and (2) that these reports be made available at reasonable times for public inspection.

⁽⁹⁾  See 81 FR 18766 (Apr. 1, 2016). See also 79 FR 63350 (Oct. 23, 2014).