# Finding of Failure To Attain the 2006 24-Hour PM
2.5
Standards; California; San Joaquin Valley; Error Correction
**AGENCY:**
Environmental Protection Agency (EPA).
**ACTION:**
Proposed rule.
**SUMMARY:**
In response to a court decision, the Environmental Protection Agency (EPA) is proposing to correct our July 22, 2020 final action erroneously granting a Clean Air Act (CAA or “Act”) section 188(e) attainment date extension for the 2006 24-hour fine particulate matter (PM <sub>2.5</sub> ) national ambient air quality standards (NAAQS or “standards”) in the San Joaquin Valley from December 31, 2019, to December 31, 2024, and is now proposing to deny California's extension request. The EPA is also proposing to determine that the San Joaquin Valley nonattainment area failed to attain the 2006 24-hour PM <sub>2.5</sub> NAAQS by the December 31, 2019 unextended attainment date. This proposed determination is based upon monitored air quality data from 2017 through 2019. If the EPA finalizes this determination as proposed, the State of California will be required to submit a revision to the California state implementation plan (SIP) that, among other elements, provides for expeditious attainment of the 2006 24-hour PM <sub>2.5</sub> NAAQS and for a five percent annual reduction in emissions of direct PM <sub>2.5</sub> or a PM <sub>2.5</sub> plan precursor pollutant.
**DATES:**
Comments must be received on or before May 4, 2026.
**ADDRESSES:**
Submit your comments, identified by Docket ID No. EPA-R09-OAR-2026-1257 at *https://www.regulations.gov.* For comments submitted at *Regulations.gov* , follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from *Regulations.gov* . The EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission ( *i.e.,* on the web, cloud, or other file sharing system). For additional submission methods, please contact the person identified in the *FOR FURTHER INFORMATION CONTACT* section. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit *https://www.epa.gov/dockets/commenting-epa-dockets.* If you need assistance in a language other than English or if you are a person with a disability who needs a reasonable accommodation at no cost to you, please contact the person identified in the *FOR FURTHER INFORMATION CONTACT* section.
**FOR FURTHER INFORMATION CONTACT:**
Ashley Graham, Geographic Strategies and Modeling Section (AIR-2-2), EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105; telephone number: (415) 972-3877; email address: *[email protected].*
**SUPPLEMENTARY INFORMATION:**
Throughout this document, “we,” “us,” and “our” refer to the EPA.
**Table of Contents**
I. Background
A. PM <sub>2.5</sub> NAAQS
B. San Joaquin Valley Designations, Classifications, and Attainment Dates for the 2006 24-Hour PM <sub>2.5</sub> NAAQS
C. The EPA's 2020 Action, Litigation, and 2022 Ninth Circuit Vacatur and Remand
II. Error Correction in Response to the *Medical Advocates for Healthy Air et al. vs. EPA* Decision and Proposed Denial of 188(e) Extension
III. The EPA's Proposed Finding of Failure to Attain
A. Monitoring Network Review, Quality Assurance, and Data Completeness
B. The EPA's Evaluation of Attainment
C. Consequences for a Serious PM <sub>2.5</sub> Nonattainment Area Failing to Attain Standards by the Attainment Date
IV. The EPA's Proposed Action
V. Statutory and Executive Order Reviews
**I. Background**
**A. PM
2.5
NAAQS**
Under section 109 of the CAA, the EPA has established NAAQS for certain pervasive air pollutants (referred to as “criteria pollutants”) and conducts periodic reviews of the NAAQS to determine whether they should be revised or whether new NAAQS should be established.
On October 17, 2006, the EPA strengthened the 24-hour (daily) NAAQS for particles less than or equal to 2.5 micrometers (µm) in diameter (PM <sub>2.5</sub> ) by lowering the level from 65 to 35 micrograms per cubic meter (µg/m <sup>3</sup> ). [^1] The 24-hour standards are based on a three-year average of 98th percentile 24-hour PM <sub>2.5</sub> concentrations. The EPA established these standards after considering substantial evidence from numerous health studies demonstrating that serious health effects are associated with exposures to PM <sub>2.5</sub> concentrations above these levels.
[^1] 71 FR 61144 (October 17, 2006); 40 CFR 50.13. In promulgating the 2006 24-hour PM <sub>2.5</sub> NAAQS, the EPA retained the level of the 1997 annual average PM <sub>2.5</sub> NAAQS of 15.0 µg/m [^3] . 62 FR 36852 (July 18, 1997); 40 CFR 50.7. In this preamble, all references to the PM <sub>2.5</sub> NAAQS, unless otherwise specified, are to the 2006 24-hour standards (35 µg/m [^3] ) as codified in 40 CFR 50.13.
Epidemiological studies have shown statistically significant correlations between elevated PM <sub>2.5</sub> levels and premature mortality. Other important health effects associated with PM <sub>2.5</sub> exposure include aggravation of respiratory and cardiovascular disease (as indicated by increased hospital admissions, emergency room visits, absences from school or work, and restricted activity days), changes in lung function and increased respiratory symptoms, and new evidence for more subtle indicators of cardiovascular health. Individuals particularly sensitive to PM <sub>2.5</sub> exposure include older adults, people with heart and lung disease, and children. [^2]
[^2] EPA, Air Quality Criteria for Particulate Matter, No. EPA/600/P-99/002aF and EPA/600/P-99/002bF, October 2004.
PM <sub>2.5</sub> can be emitted directly into the atmosphere as a solid or liquid particle (primary PM <sub>2.5</sub> or direct PM <sub>2.5</sub> ) or can be formed in the atmosphere as a result of various chemical reactions from precursor emissions of nitrogen oxides, sulfur oxides, volatile organic compounds, and ammonia (secondary PM <sub>2.5</sub> ). [^3]
[^3] 81 FR 58010, 58011 (August 24, 2016).
**B. San Joaquin Valley Designations, Classifications, and Attainment Dates for the 2006 24-Hour PM
2.5
NAAQS**
Following promulgation of a new or revised NAAQS, the EPA is required under CAA section 107(d) to designate areas throughout the nation as attaining or not attaining the NAAQS. Effective December 14, 2009, the EPA finalized initial air quality designations for the 2006 24-hour PM <sub>2.5</sub> NAAQS, using air quality monitoring data for the three-year periods of 2005-2007 and 2006-2008. [^4] The EPA designated the San Joaquin Valley as a nonattainment area for the 2006 24-hour PM <sub>2.5</sub> NAAQS. [^5]
[^4] 74 FR 58688 (November 13, 2009).
[^5] Id. at 58696, codified at 40 CFR 81.305.
The San Joaquin Valley PM <sub>2.5</sub> nonattainment area encompasses over 23,000 square miles and includes all or part of eight counties: San Joaquin, Stanislaus, Merced, Madera, Fresno, Tulare, Kings, and the valley portion of Kern. [^6] The area is home to over four million people and is the nation's leading agricultural region. Stretching over 250 miles from north to south and averaging 80 miles wide, it is partially enclosed by the Coast Mountain range to the west, the Tehachapi Mountains to the south, and the Sierra Nevada range to the east.
[^6] For a precise description of the geographic boundaries of the San Joaquin Valley PM <sub>2.5</sub> nonattainment area, see 40 CFR 81.305.
On June 2, 2014, the EPA classified the San Joaquin Valley as a “Moderate” nonattainment area for these NAAQS, thereby establishing December 31, 2015, as the latest permissible attainment date for the area under section 188(c)(1) of the CAA. [^7] Effective February 19, 2016, the EPA reclassified the San Joaquin Valley as a “Serious” nonattainment area for these NAAQS. [^8] Shortly thereafter, the EPA approved the State's demonstration that it was impracticable to attain the 2006 24-hour PM <sub>2.5</sub> NAAQS by the December 31, 2015 Moderate area attainment date and related plan elements addressing the Moderate area requirements for the 2006 24-hour PM <sub>2.5</sub> NAAQS. [^9]
[^7] 79 FR 31566 (June 2, 2014). The EPA promulgated these PM <sub>2.5</sub> nonattainment area classifications in response to a 2013 decision of the Court of Appeals for the D.C. Circuit remanding the EPA's prior implementation rule for the PM <sub>2.5</sub> NAAQS and directing the EPA to repromulgate implementation rules pursuant to subpart 4 of part D, title I of the Act. *Natural Resources Defense Council* v. *EPA,* 706 F.3d 428 (D.C. Cir. 2013).
[^8] 81 FR 2993 (January 20, 2016).
[^9] 81 FR 59876 (August 31, 2016).
Upon reclassification as a Serious PM <sub>2.5</sub> nonattainment area, the San Joaquin Valley became subject to a new statutory attainment date no later than the end of the tenth calendar year following designation ( *i.e.,* December 31, 2019) and the requirement to submit a Serious area plan satisfying the requirements of CAA Title I, part D, including the requirements of subpart 4, for the 2006 24-hour PM <sub>2.5</sub> NAAQS. [^10] As explained in the EPA's final reclassification action, the Serious area plan for the San Joaquin Valley was required to include, among other things, a demonstration (including air quality modeling) that the plan provides for attainment as expeditiously as practicable and no later than the applicable attainment date. The EPA established an August 21, 2017 deadline for California to adopt and submit a SIP submission addressing the Serious nonattainment area requirements for the 2006 24-hour PM <sub>2.5</sub> NAAQS. [^11] The EPA also noted that California may choose to submit a request for an extension of the December 31, 2019 Serious area attainment date pursuant to CAA section 188(e) simultaneously with its submission of a Serious area plan for the area. [^12]
[^10] 81 FR 2993, 2998 (January 20, 2016).
[^11] Id. at 3000 and 81 FR 42263 (June 29, 2016) (codified at 40 CFR 52.247(f)).
[^12] 81 FR 2993, 2998 (January 20, 2016).
Section 188(e) of the CAA allows the EPA to extend the attainment date for a Serious area by up to five years if attainment by the Serious area attainment date is impracticable. However, before the Agency may grant an extension of the attainment date, the state must first:
1. Apply to the EPA for an extension of the PM <sub>2.5</sub> attainment date beyond the statutory attainment date;
2. Demonstrate that attainment by the Serious area attainment date is impracticable;
3. Have complied with all requirements and commitments applying to the area in its implementation plan;
4. Demonstrate to the Administrator's satisfaction that its Serious area plan includes the most stringent measures that are achieved in practice in any state and are feasible for the area; and
5. Submit SIP revisions containing a demonstration of attainment by the most expeditious alternative date practicable.
Under State law, the California Air Resources Board (CARB) is the Governor's designee for adoption and submittal of SIPs and SIP revisions to the EPA in compliance with CAA requirements. CARB is also generally responsible under State law for the regulation of mobile emission sources. Local air pollution control districts are generally responsible for regulation of stationary emission sources. In the San Joaquin Valley, regional air quality plans are developed by the San Joaquin Valley Unified Air Pollution Control District (SJVUAPCD or “District”) with input from CARB and typically rely on both mobile source control measures for which CARB is responsible and stationary source control measures for which the District is responsible. Once the District adopts a regional air quality plan, the plan is submitted to CARB for adoption and submittal to the EPA for inclusion into the California SIP.
On November 16, 2018, CARB submitted to the EPA substantial portions of the Serious area plan for the 2006 24-hour PM <sub>2.5</sub> NAAQS following CARB's adoption of one component of the plan on October 25, 2018, and the SJVUAPCD's adoption of a second component of it on November 15, 2018. [^13] Because CARB had not yet adopted this submission in its entirety, the EPA determined that it did not meet the EPA's completeness requirements for SIP submissions under 40 CFR part 51, appendix V, section 2.1. [^14] Because the submission was incomplete, the EPA issued a finding of failure to submit, which became effective on January 7, 2019, and triggered clocks for the application of sanctions unless the EPA affirmatively determined that the State has submitted a complete SIP addressing the deficiency that was the basis for these findings, consistent with CAA section 179(b) and the EPA's sanctions sequencing rule in 40 CFR 52.31. [^15] These findings also triggered the obligation under CAA section 110(c) for the EPA to issue a Federal implementation plan no later than two years after the effective date of the findings, unless the State has submitted, and the EPA has approved, the required SIP submittal. [^16]
[^13] Letter dated November 16, 2018, from Kurt Karperos, Deputy Executive Officer, CARB for Richard W. Corey, Executive Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region IX (submitted electronically November 16, 2018).
[^14] 83 FR 62720 (December 6, 2018). The EPA made these findings in response to a court order issued in *Committee for a Better Arvin, et al.,* v. *Andrew Wheeler, et al.* Case No. 18-cv-05700-RS (N.D. Cal., October 24, 2018).
[^15] Id. at 62723.
[^16] Id.
On May 10, 2019, CARB submitted to the EPA two SIP revisions (collectively referred to as the “SJV PM <sub>2.5</sub> Plan” or “Plan”) to meet the Serious nonattainment area requirements for the 2006 24-hour PM <sub>2.5</sub> NAAQS in the San Joaquin Valley, among other requirements for other PM <sub>2.5</sub> NAAQS. [^17] The SJV PM <sub>2.5</sub> Plan included a request under CAA section 188(e) for an extension of the Serious area attainment date for the area for the 2006 24-hour PM <sub>2.5</sub> NAAQS from December 31, 2019, to December 31, 2024.
[^17] Letter dated May 9, 2019, from Richard Corey, Executive Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9, submitting the “2018 Plan for the 1997, 2006, and 2012 PM <sub>2.5</sub> Standards,” adopted by SJVUAPCD on November 15, 2018, and by CARB on January 24, 2019, including a revised Appendix H submitted by CARB as a technical correction on February 11, 2020, and the “San Joaquin Valley Supplement to the 2016 State Strategy for the State Implementation Plan,” adopted by CARB on October 25, 2018 (submitted electronically May 10, 2019).
On November 10, 2019, the SJV PM <sub>2.5</sub> Plan became complete by operation of law. The EPA subsequently made an affirmative completeness finding on June 24, 2020, terminating the sanctions clocks that were triggered by the December 6, 2018 finding that the State had failed to submit a complete SIP submission addressing the statutory requirements that apply to areas designated nonattainment for the PM <sub>2.5</sub> NAAQS. [^18]
[^18] Letter dated June 24, 2020, from Elizabeth J. Adams, Director, Air and Radiation Division, EPA Region IX, to Richard W. Corey, Executive Officer, CARB, Subject: “Completeness Finding for State Implementation Plan (SIP) Submissions for San Joaquin Valley for the 1997, 2006, and 2012 Fine Particulate Matter (PM <sub>2.5</sub> ) National Ambient Air Quality Standards (NAAQS) and Termination of Clean Air Act (CAA) Sanctions Clocks.”
**C. The EPA's 2020 Action, Litigation, and 2022 Ninth Circuit Vacatur and Remand**
On July 22, 2020, the EPA approved portions of the SJV PM <sub>2.5</sub> Plan as they pertain to the Serious area requirements for the 2006 24-hour PM <sub>2.5</sub> NAAQS. [^19] Specifically, the EPA approved the following portions of the SJV PM <sub>2.5</sub> Plan for the 2006 24-hour PM <sub>2.5</sub> NAAQS:
[^19] 85 FR 44192 (July 22, 2020).
• The 2013 base year emissions inventories;
• The demonstration that best available control measures, including best available control technology, for the control of direct PM <sub>2.5</sub> and PM <sub>2.5</sub> plan precursors would be implemented no later than four years after the area was reclassified;
• The demonstration (including air quality modeling) that the Plan provides for attainment as expeditiously as practicable but no later than December 31, 2024;
• Plan provisions that require reasonable further progress toward attainment by the applicable date;
• Quantitative milestones to be achieved every three years until the area is redesignated to attainment and that demonstrate reasonable further progress toward attainment by the applicable attainment date;
• Motor vehicle emissions budgets for 2020, 2023, and 2024 as shown in Table 14 of the EPA's proposed rule; and
• The inter-pollutant trading mechanism provided for use in transportation conformity analyses for the 2006 24-hour PM <sub>2.5</sub> NAAQS. [^20]
[^20] Id. at 44204. The EPA did not act on the contingency measure element of the SJV PM <sub>2.5</sub> Plan as part of our July 22, 2020 (85 FR 44192) action. The EPA finalized approval of the State's contingency measures for the 2006 24-hour PM <sub>2.5</sub> NAAQS via a subsequent action on October 4, 2024 (89 FR 80749, October 4, 2024).
The EPA also granted an extension of the Serious area attainment date for the 2006 24-hour PM <sub>2.5</sub> NAAQS in the San Joaquin Valley from December 31, 2019, to December 31, 2024, based on a determination that the State had satisfied the statutory criteria for such an extension. [^21]
[^21] Id. at 44205. To support our action on the State's extension request, we also approved CARB's “Revision to the California State Implementation Plan for PM <sub>2.5</sub> Standards in the San Joaquin Valley” (“PM <sub>2.5</sub> Prior Commitment Revision”), revising the State's aggregate commitment in the 2012 PM <sub>2.5</sub> Plan to reflect updated inventories in the SJV PM <sub>2.5</sub> Plan and determined that the State had met the 0.86 tons per day (tpd) emission reduction commitment. See also the EPA's proposed approval at 85 FR 27976 (May 12, 2020).
As part of their respective control measure commitments in the SJV PM <sub>2.5</sub> Plan, CARB and the District each identified potential control measures that were expected to achieve the additional emissions reductions needed for attainment of the 2006 24-hour PM <sub>2.5</sub> NAAQS. Given the Plan's reliance on these enforceable commitments, the EPA considered the three factors that the agency uses to determine whether the use of enforceable commitments in lieu of adopted measures satisfy CAA planning requirements: (1) the commitment represents a limited portion of required reductions; (2) the state is capable of fulfilling its commitment; and (3) the commitment is for a reasonable and appropriate timeframe. The EPA determined that the three criteria (“three-factor test”) had been met and therefore approved CARB's and the District's aggregate commitments in the SJV PM <sub>2.5</sub> Plan. [^22]
[^22] Id. at 44204, codified at 40 CFR 52.220(c)(536)(ii)(A)( *2* ) and (537)(ii)(B)( *2* ).
Medical Advocates for Healthy Air, National Parks Conservation Association, Association of Irritated Residents, and Sierra Club (“Petitioners”), represented by Earthjustice, filed a petition for review of the EPA's July 22, 2020 final action [^23] approving the SJV PM <sub>2.5</sub> Plan and extending the attainment deadline under CAA section 188(e). Petitioners objected to our approval of the SJV PM <sub>2.5</sub> Plan on several grounds, including that the EPA's approval of the aggregate commitments contained in the Plan and the EPA's approval of the Plan's “most stringent measures” and “best available control measures” should be vacated.
[^23] 85 FR 44192 (July 22, 2020).
On April 13, 2022, in an unpublished memorandum opinion, the U.S. Court of Appeals for the Ninth Circuit issued its decision in the *Medical Advocates for Healthy Air et al.* vs. *EPA* case, granting the petition in part and denying the petition in part. [^24] The Court held that the EPA's analysis of the second factor of the three-factor test was arbitrary and capricious because, in the Court's view, the Agency had failed to provide evidence or reasoned justification that California would be able to meet its commitment due to a shortfall in funding for the Plan's incentive-based control measures. Thus, the Court granted the petition with respect to the EPA's approval of the aggregate commitments in the Plan, stating, “we vacate the portion of the final rule that determined that the relevant aggregate commitments satisfied the second factor of the three-factor test and remand to the EPA for further consideration of the second factor, and for further proceedings consistent with this decision.” In all other respects, the Ninth Circuit denied the petition.
[^24]*Medical Advocates for Healthy Air et al* . vs. *EPA,* 20-72780 (9th Cir. 2022).
**II. Error Correction in Response to the Medical Advocates for Healthy Air et al. vs. EPA Decision and Proposed Denial of 188(e) Extension**
In response to the *Medical Advocates for Healthy Air et al.* vs. *EPA* decision, the EPA is proposing to correct its erroneous granting of the CAA section 188(e) attainment date extension for the 2006 24-hour PM <sub>2.5</sub> NAAQS for the San Joaquin Valley. Section 110(k)(6) of the CAA provides that if the EPA Administrator determines that the Administrator's action on a SIP revision was in error, the Administrator may revise such action as appropriate without requiring an additional submission from the state. The EPA's stated basis for granting the extension was, in part, that the SJV PM <sub>2.5</sub> Plan demonstrated expeditious attainment by 2024. [^25] The *Medical Advocates for Healthy Air et al.* vs. *EPA* opinion established that the EPA was mistaken in its approval of the aggregate commitment, which it relied upon in concluding that the Plan demonstrated expeditious attainment by 2024. Because the EPA's granting of the extension was expressly premised on the validity of the attainment demonstration, the EPA now proposes to find that its approval of the CAA section 188(e) extension was in error. The EPA is proposing to revise the erroneous granting of the extension of the attainment date and to now deny the extension request.
[^25] 85 FR 17382, 17386-17387, 17404-17419 (March 27, 2020).
The EPA's proposal for its July 2020 action evaluated the State's submitted attainment demonstration, which modeled attainment by 2024. The proposal explained that the EPA was evaluating the attainment demonstration in support of the State's requested CAA section 188(e) attainment date extension from 2019 to 2024. The proposal began by describing the five criteria that a state must meet before the EPA may extend the attainment date for a Serious area under CAA section 188(e) (see also section I.A of this document) and proceeded to evaluate the State's extension request against these criteria. [^26] Turning to its evaluation of the State's extension request, the proposal stated, “given the section 188(e) requirement to demonstrate expeditious attainment of the NAAQS, [we are evaluating] the SJV PM <sub>2.5</sub> Plan's attainment demonstration, including the Plan's air quality modeling approach and results and control strategy. [^27] The proposal then summarized the EPA's evaluation of the attainment demonstration and proposed to approve it as modeling attainment by 2024. [^28] The proposal also explained that a portion of the modeled reductions relied upon to demonstrate attainment in 2024 were based on an aggregate tonnage commitment from the State to achieve additional reductions beyond those attributed to baseline measure and new control strategy measures. [^29] The EPA finalized its granting of the CAA section 188(e) extension based in part on its analysis of the control measures and aggregate commitments relied upon to model attainment in 2024. [^30]
[^26] Id. at 17386-17387, 17404-17419. In its description of the requirement to submit a demonstration of attainment by the most expeditious alternative date practicable, the proposal stated that “[e]valuation of a modeled attainment demonstration consists of two parts: evaluation of the technical adequacy of the modeling itself and evaluation of the control measures that are relied on to demonstrate attainment.” Id. at 17387.
[^27] Id. at 17404.
[^28] Id. at 17409-17419.
[^29] Id. at 17412-17419.
[^30] 85 FR 44192 (July 22, 2020).
In the *Medical Advocates for Healthy Air et al.* vs. *EPA* decision, the Ninth Circuit Court of Appeals found that there was no rational connection between the facts found by the EPA regarding the State's ability to meet its aggregate commitment and the conclusion that the District would nevertheless meet its attainment goals. Accordingly, the Court vacated “the portion of the final rule that determined that the relevant aggregate commitments satisfied the . . . test,” and remanded to the EPA. The EPA will address this remand in a separate action. [^31]
[^31] The portions of the SJV PM <sub>2.5</sub> Plan that were approved into the California SIP on July 22, 2020 (85 FR 44192) (including the motor vehicle emissions budgets) are not being addressed in this proposed action and remain in the SIP.
For the purposes of the present action, the *Medical Advocates for Healthy Air et al.**vs. EPA* order establishes that the EPA's stated basis for extending the attainment date from 2019 to 2024 was insufficiently supported and thus in error. Because the EPA's rationale for extending the attainment date included a statement that CAA section 188(e) requires a demonstration of expeditious attainment of the NAAQS, and the Court has vacated the EPA's approval of a necessary part of that attainment demonstration, the EPA was in error when it granted the CAA section 188(e) extension on that basis. Accordingly, pursuant to section 110(k)(6) of the Act, the EPA is proposing to revise its granting of the CAA section 188(e) extension and instead now proposes to deny the extension. The EPA's approval of a CAA section 188(e) extension is discretionary (“the Administrator *may* extend the attainment date” (emphasis added)); because both the 2019 and the 2024 attainment dates have now passed, the EPA has not identified a compelling reason to re-evaluate and potentially grant the extension request. [^32] Accordingly, the EPA proposes to revise its 2020 action and instead deny the extension request. If finalized as proposed, this would result in the attainment date for the 2006 24-hour PM <sub>2.5</sub> NAAQS reverting to the original Serious area date of December 31, 2019.
[^32] We note that based on the most recent quality-assured and certified data for 2022-2024, the San Joaquin Valley continues to violate the 2006 24-hour PM <sub>2.5</sub> NAAQS with a 2024 design value of 48 µg/m [^3] . EPA, AQS Design Value Report (AMP480), Report Request ID: 2351309, February 5, 2026.
**III. The EPA's Proposed Finding of Failure To Attain**
**A. Monitoring Network Review, Quality Assurance, and Data Completeness**
Section 179(c)(1) of the CAA requires the EPA to determine whether a PM <sub>2.5</sub> nonattainment area attained the PM <sub>2.5</sub> standards by the applicable attainment date, based on the area's air quality as of the attainment date. A determination of whether an area's air quality meets the PM <sub>2.5</sub> standards is generally based upon three years of complete, quality-assured air quality monitoring data gathered at established state and local air monitoring stations (SLAMS) in the area and entered into the EPA's Air Quality System (AQS) database. Data from ambient air monitors operated by state/local agencies in compliance with EPA monitoring requirements must be submitted to AQS. Monitoring agencies annually certify that these data are accurate to the best of their knowledge. Accordingly, the EPA relies primarily on data in AQS when determining compliance with the NAAQS. [^33] The EPA reviews all data to determine the area's air quality status in accordance with 40 CFR part 50, appendix N.
[^33] See 40 CFR 50.13; 40 CFR part 50, appendix L; 40 CFR part 53; 50 CFR part 58; and 40 CFR part 58, appendices A, C, D, and E.
Under EPA regulations in 40 CFR 50.13 and in accordance with appendix N, the 2006 24-hour PM <sub>2.5</sub> NAAQS are met when the average of the three annual 98th percentile 24-hour concentrations, as determined in accordance with the rounding conventions in 40 CFR part 50, appendix N, is less than or equal to 35 µg/m <sup>3</sup> at each eligible monitoring site within the area. This three-year average is referred to as the “design value.” The data completeness requirement for a given year is met when at least 75 percent of the scheduled sampling days for each quarter have valid data.
Section 110(a)(2)(B)(i) of the CAA requires states to establish and operate air monitoring networks to compile data on ambient air quality for all criteria pollutants. The monitoring requirements are specified in 40 CFR part 58. These requirements are applicable to state and, where delegated, local air monitoring agencies that operate criteria pollutant monitors. The regulations in 40 CFR part 58 establish specific requirements for operating air quality surveillance networks to measure ambient concentrations of PM <sub>2.5</sub> , including requirements for measurement methods, network design, quality assurance procedures, and in the case of large urban areas, the minimum number of monitoring sites designated as SLAMS.
In section 4.7 of appendix D to 40 CFR part 58, the EPA specifies minimum monitoring requirements for PM <sub>2.5</sub> to operate at SLAMS. SLAMS produce data that are eligible for comparison with the NAAQS, and the monitor must be an approved Federal Reference Method (FRM) or Federal Equivalence Method (FEM). The minimum number of SLAMS required is described in section 4.7.1 and can be met by either filter-based or continuous FRMs or FEMs. The monitoring regulations also provide that each core-based statistical area must operate a minimum number of PM <sub>2.5</sub> continuous monitors; [^34] however, this requirement can be met by either an FEM or a non-FEM continuous monitor, and the continuous monitors can be located with other SLAMS or at a different location. Consequently, the monitoring requirements for PM <sub>2.5</sub> can be met with filter-based FRMs/FEMs, continuous FEMs, continuous non-FEMs, or a combination of monitors at each required SLAMS.
[^34] 40 CFR part 58, appendix D, section 4.7.2.
Under 40 CFR 58.10, states are required to submit annual monitoring network plans to the EPA. [^35] Within the San Joaquin Valley, CARB and the District are the agencies responsible for assuring that the area meets PM <sub>2.5</sub> air quality monitoring requirements. The District submits annual monitoring network plans (ANPs) to the EPA that describe the various monitoring sites operated by the District as well as those operated by CARB within the San Joaquin Valley. These plans discuss the status of the air monitoring network, as required under 40 CFR 58.10. Each year, the EPA reviews these ANPs for compliance with the applicable monitoring requirements in 40 CFR part 58. On October 29, 2020, the EPA approved those portions of the “2020 Air Monitoring Network Plan” that pertain to the adequacy of the network for PM <sub>2.5</sub> monitoring purposes. [^36]
[^35] 40 CFR 58.10(a)(1).
[^36] See “San Joaquin Valley Air Pollution Control District, 2020 Air Monitoring Network Plan,” dated June 29, 2020, and the EPA's approval via letter dated October 26, 2020, from Gwen Yoshimura, Manager, Air Quality Analysis Office, EPA Region IX, to Jon Klassen, Director of Strategies and Incentives, SJVUAPCD, with enclosure.
During the 2017-2019 period, ambient PM <sub>2.5</sub> concentration data that are eligible for use in determining whether an area has attained the PM <sub>2.5</sub> NAAQS were collected at a total of 17 sites within the San Joaquin Valley. The District operates 11 of these sites and CARB operates 6 of the sites. All of the sites are designated as SLAMS for PM <sub>2.5</sub> . [^37] Based on our review of the PM <sub>2.5</sub> monitoring network, we propose to find that the monitoring network in the San Joaquin Valley is adequate for the purpose of collecting ambient PM <sub>2.5</sub> concentration data for use in determining whether the San Joaquin Valley attained the 2006 24-hour PM <sub>2.5</sub> NAAQS by the December 31, 2019 attainment date.
[^37] There are a number of other PM <sub>2.5</sub> monitoring sites within the valley, including other sites operated by the National Park Service and certain Indian Tribes, but the data collected from these sites are non-regulatory and not eligible for use in determining whether the San Joaquin Valley has attained the PM <sub>2.5</sub> NAAQS.
In accordance with 40 CFR 58.15, monitoring agencies must submit a letter to the EPA to certify that all of the ambient concentration and quality assurance data for the previous year have been submitted to AQS and that the ambient concentration data are accurate to the best of their knowledge, taking into consideration the quality assurance findings. The letter must address data for all FRM and FEM monitors at SLAMS and special purpose monitoring stations that meet the criteria specified in 40 CFR part 58, appendix A. CARB annually certifies that the data the agency submits to AQS are quality assured, including data collected by CARB at monitoring sites in the San Joaquin Valley. [^38] SJVUAPCD does the same for data submitted to AQS from monitoring sites operated by the District. [^39]
[^38] We have included CARB's annual data certifications for 2017, 2018, and 2019 in the docket for this action.
[^39] We have included SJVUAPCD's annual data certifications for 2017, 2018, and 2019 in the docket for this action.
With respect to data completeness, we determined that the data collected by CARB and the District met the quarterly completeness criterion for all 12 quarters of the three-year period at most of the PM <sub>2.5</sub> monitoring sites in the San Joaquin Valley. More specifically, among the 17 PM <sub>2.5</sub> monitoring sites from which regulatory data are available, the data from 1 of the sites did not meet the 75 percent completeness criterion for at least one quarter in the 2017-2019 period. We note that monitors with incomplete data in one or more quarters may still produce valid design values if the conditions for applying one of the EPA's data substitution tests are met. [^40] The Manteca monitoring site (AQS ID: 06-077-2010) did not meet the 75 percent completeness criterion for three quarters in 2019; however, the resulting 24-hour design value is valid because it is greater than the level of the 2006 24-hour PM <sub>2.5</sub> NAAQS.
[^40] See 40 CFR part 50, appendix N, section 4.2(b).
Finally, the EPA conducts regular technical systems audits (TSAs) where we review and inspect state and local ambient air monitoring programs to assess compliance with applicable regulations concerning the collection, analysis, validation, and reporting of ambient air quality data. For the purposes of this proposal, we reviewed the findings from the EPA's most recent TSAs of the CARB and the District ambient air monitoring programs. [^41] The results of the TSAs do not preclude the EPA from relying on these data to determine whether the San Joaquin Valley PM <sub>2.5</sub> nonattainment area attained the 2006 24-hour PM <sub>2.5</sub> NAAQS by the December 31, 2019 attainment date.
[^41] See letter dated March 14, 2024, from Matthew Lakin, Director, Air and Radiation Division, EPA Region IX, to Edie Chang, Deputy Executive Officer, CARB and enclosure titled “Technical Systems Audit of the Ambient Air Monitoring Program: California Air Resources Board, December 2021-August 2022.”
In summary, based on the EPA's reviews of the relevant ANPs, certifications, quality assurance data, and TSAs, we propose to find that the PM <sub>2.5</sub> data collected at the San Joaquin Valley monitoring sites are suitable for determining whether the San Joaquin Valley PM <sub>2.5</sub> nonattainment area attained the 2006 24-hour PM <sub>2.5</sub> NAAQS by the December 31, 2019 attainment date.
**B. The EPA's Evaluation of Attainment**
Table 1 of this document lists the 24-hour PM <sub>2.5</sub> design values at each of the 17 monitoring sites within the San Joaquin Valley PM <sub>2.5</sub> nonattainment area, expressed as a single design value representing the 2017-2019 period and the annual 98th percentile for each individual year. The PM <sub>2.5</sub> data show that the design values for the 2017-2019 period are greater than 35 µg/m <sup>3</sup> at 16 of the sites in the San Joaquin Valley.
| Site name | AQS ID | Annual 98th percentile | 2017 | 2018 | 2019 | 2017-2019 |
| --- | --- | --- | --- | --- | --- | --- |
| | | | | | | |
| Fresno-Garland | 06-019-0011 | 68.0 | 63.5 | 36.9 | 56 | |
| Tranquillity | 06-019-2009 | 34.4 | 51.4 | 17.1 | 34 | |
| Clovis-Villa | 06-019-5001 | 50.0 | 57.0 | 28.0 | 45 | |
| Fresno-Pacific | 06-019-5025 | 73.2 | 65.5 | 37.1 | 59 | |
| | | | | | | |
| Bakersfield-Golden/M-St | 06-029-0010 | 71.3 | 60.9 | 44.3 | 59 | |
| Bakersfield-California | 06-029-0014 | 71.8 | 69.2 | 43.4 | 61 | |
| Bakersfield-Airport (Planz) | 06-029-0016 | 69.7 | 60.8 | 46.7 | 59 | |
| | | | | | | |
| Corcoran-Patterson | 06-031-0004 | 69.7 | 78.0 | 45.1 | 64 | |
| Hanford-Irwin | 06-031-1004 | 68.7 | 78.2 | 41.1 | 63 | |
| | | | | | | |
| Madera-City | 06-039-2010 | 45.8 | 50.2 | 23.9 | 40 | |
| | | | | | | |
| Merced-Coffee | 06-047-0003 | 44.7 | 56.0 | 23.4 | 41 | |
| Merced-M St | 06-047-2510 | 40.3 | 52.7 | 29.5 | 41 | |
| | | | | | | |
| Stockton-Hazelton | 06-077-1002 | 44.2 | 92.3 | 32.9 | 56 | |
| Manteca | 06-077-2010 | 36.4 | 96.9 | 26.8 | 53 | |
| | | | | | | |
| Modesto-14th Street | 06-099-0005 | 51.1 | 100.4 | 28.4 | 60 | |
| Turlock | 06-099-0006 | 48.0 | 88.6 | 36.0 | 58 | |
| | | | | | | |
| Visalia-Church | 06-107-2002 | 74.6 | 63.4 | 45.5 | 61 | |
The data in Table 1 of this document show that all but one site in the San Joaquin Valley failed to attain the 2006 24-hour PM <sub>2.5</sub> NAAQS by December 31, 2019. The 2019 24-hour design value site, *i.e.,* the site with the highest design value based on 2017-2019 data, is the Corcoran-Patterson site with a 2019 24-hour PM <sub>2.5</sub> design value of 64 µg/m <sup>3</sup> .
For an area to attain the 2006 24-hour PM <sub>2.5</sub> NAAQS by December 31, 2019, the 2019 design value (reflecting data from 2017-2019) at each eligible monitoring site must be equal to or less than 35 µg/m <sup>3</sup> . Table 1 of this document shows that the 2019 design values at all but one site in the San Joaquin Valley area are greater than 35 µg/m <sup>3</sup> . Therefore, based on quality-assured and certified data for 2017-2019, we are proposing to determine that the San Joaquin Valley failed to attain the 2006 24-hour PM <sub>2.5</sub> NAAQS by the 2019 attainment date. [^42]
[^42] We note that based on the most recent quality-assured and certified data for 2022-2024, the San Joaquin Valley continues to violate the 2006 24-hour PM <sub>2.5</sub> NAAQS with a 2024 design value of 48 µg/m [^3] . EPA, AQS Design Value Report (AMP480), Report Request ID: 2351309, February 5, 2026.
**C. Consequences for a Serious PM
2.5
Nonattainment Area Failing To Attain Standards by the Attainment Date**
The consequences for a Serious PM <sub>2.5</sub> nonattainment area for failing to attain the standards by the applicable attainment date are set forth in CAA sections 179(d) and 189(d). Under section 179(d) of the CAA, a state must submit a SIP revision for the area meeting the requirements of CAA sections 110 and 172. Section 172 of the CAA requires, among other elements, a demonstration of attainment and reasonable further progress, and contingency measures. Section 189(d) of the CAA requires that the SIP revision must provide for attainment of the standards and, from the date of the SIP submittal until attainment, for an annual reduction in the emissions of direct PM <sub>2.5</sub> or a PM <sub>2.5</sub> plan precursor within the area of not less than five percent of the amount of such emissions as reported in the most recent inventory prepared for such area. [^43] The requirement for a new attainment demonstration under CAA section 189(d) also triggers the requirement for a SIP revision for quantitative milestones under section 189(c) that are to be achieved every three years until redesignation to attainment.
[^43] 81 FR 58010 at 58100, 58158 (August 24, 2016). The EPA defines PM <sub>2.5</sub> plan precursor as those PM <sub>2.5</sub> precursors required to be regulated in the applicable attainment plan and/or nonattainment new source review program. Id. at 58152.
The new attainment date is set by CAA section 179(d)(3), which relies upon section 172(a)(2) to establish a new attainment date but with a different starting point than provided in section 172(a)(2). Under CAA section 179(d)(3), the new attainment date is the date by which attainment can be achieved as expeditiously as practicable, but no later than 5 years from the date of the final determination of failure to attain, except that the EPA may extend the attainment date for a period no greater than 10 years from the final determination, considering the severity of nonattainment and the availability and feasibility of pollution control measures.
Section 189(d) of the CAA establishes that a state shall submit the required SIP revision within 12 months after the applicable attainment date. In this case, because we are proposing to find that the San Joaquin Valley area failed to attain by the December 31, 2019 attainment date, the submission deadline for a revised plan for the 2006 24-hour PM <sub>2.5</sub> NAAQS pursuant to section 189(d) of the CAA would have been December 31, 2020. This deadline has already passed and it is now impossible for the State to submit a revised plan by the December 31, 2020 submission deadline. Consistent with the EPA's past practice when application of the particulate matter-specific requirements of subpart 4 would be impracticable, the EPA proposes to apply the applicable deadline from the general nonattainment area requirements found in subpart 1. [^44] Under the CAA subpart 1 section specifying “Consequences for failure to attain,” found in section 179(d)(1), states are required to submit a revision to the applicable SIP within one year after the EPA publishes the notice of failure to attain. Consistent with the one-year timeframe provided under CAA section 179(d)(1), if the EPA finalizes this determination that the San Joaquin Valley failed to attain the 2006 24-hour PM <sub>2.5</sub> NAAQS by the December 31, 2019 attainment date, the EPA proposes to require that California submit a SIP revision that complies with CAA sections 179(d) and 189(d) within one year of the EPA's final determination.
[^44] See *Ass'n of Irritated Residents* v. *EPA,* 423 F. 3d 989 (9th Cir. 2005) (upholding the EPA's application of subpart 1 attainment deadlines and noting that strictly applying the subpart 4 deadlines “would leave the EPA with no ability to set a new date at all once a PM-10 area has missed its deadline.”).
Additionally, a final determination by the EPA of failure to attain the 2006 24-hour PM <sub>2.5</sub> NAAQS in the San Joaquin Valley by the Serious area attainment date would trigger the requirement for the State to implement contingency measures in accordance with 40 CFR 51.1014. [^45]
[^45] The State's contingency measures for the San Joaquin Valley for the 2006 24-hour PM <sub>2.5</sub> NAAQS consist of CARB's “Smog Check Contingency Measure,” the District's contingency provisions in Rule 8051 (“Open Areas”), and the District's contingency provisions in Rule 4901 (“Wood Burning Fireplaces and Wood Burning Heaters”) (89 FR 80749, October 4, 2024). A previous EPA finding that the San Joaquin Valley failed to attain the 1997 8-hour ozone standards constituted the first triggering event of two triggers for CARB's Smog Check Contingency Measure (90 FR 30607, July 10, 2025). Thus, a final determination of failure to attain the 2006 24-hour PM <sub>2.5</sub> NAAQS would constitute a second and final triggering event for that measure in the San Joaquin Valley. A final determination of failure to attain for the 2006 24-hour PM <sub>2.5</sub> NAAQS would constitute a first triggering event of two triggers for the Rule 4901 (“Wood Burning Fireplaces and Wood Burning Heaters”) contingency provisions and the only triggering event for the Rule 8051 (“Open Areas”) contingency provisions.
**IV. The EPA's Proposed Action**
For the reasons discussed in section II of this document, we are proposing to correct our previous erroneous granting of a CAA section 188(e) attainment date extension for the 2006 24-hour PM <sub>2.5</sub> NAAQS in the San Joaquin Valley from December 31, 2019, to December 31, 2024, and to now deny California's request for an extension. If finalized, this action would have the effect of reestablishing the December 31, 2019 attainment date for the San Joaquin Valley for the 2006 24-hour PM <sub>2.5</sub> NAAQS.
Based on our proposal to reestablish the December 31, 2019 attainment date, and in accordance with section 179(c)(1) of the CAA, the EPA is proposing to determine that the San Joaquin Valley Serious PM <sub>2.5</sub> nonattainment area has failed to attain the 2006 24-hour PM <sub>2.5</sub> NAAQS by the applicable attainment date of December 31, 2019. If we finalize our action as proposed, California will be required under CAA sections 179(d) and 189(d) to submit a revision to the SIP for the San Joaquin Valley that, among other elements, demonstrates expeditious attainment of the standards within the time period provided under CAA section 179(d) and that provides for annual reduction in the emissions of PM <sub>2.5</sub> or a PM <sub>2.5</sub> plan precursor pollutant within the area of not less than five percent until attainment. The SIP revision required under CAA sections 179(d) and 189(d) would be due for submittal to the EPA within 12 months of the EPA's final determination that the area failed to attain by the December 31, 2019 attainment date.
The EPA is soliciting public comments on the issues discussed in this document. We will accept comments from the public on this proposal until May 4, 2026. We will consider these comments before taking final action.
**V. Statutory and Executive Order Reviews**
Additional information about these statutes and Executive Orders can be found at *https://www.epa.gov/laws-regulations/laws-and-executive-orders.*
**A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review**
This action is not a significant regulatory action and was therefore not submitted to the Office of Management and Budget (OMB) for review.
**B. Executive Order 14192: Unleashing Prosperity Through Deregulation**
This action is not expected to be an Executive Order 14192 regulatory action because this action is not significant under Executive Order 12866.
**C. Paperwork Reduction Act (PRA)**
This action does not impose an information collection burden under the PRA because this action does not impose additional requirements beyond those imposed by state law.
**D. Regulatory Flexibility Act (RFA)**
I certify that this action will not have a significant economic impact on a substantial number of small entities under the RFA. This action will not impose any requirements on small entities beyond those imposed by state law.
**E. Unfunded Mandates Reform Act (UMRA)**
This action does not contain any unfunded mandate as described in UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect small governments. This action does not impose additional requirements beyond those imposed by state law. Accordingly, no additional costs to state, local, or Tribal Governments, or to the private sector, result from this action.
**F. Executive Order 13132: Federalism**
This action does not have federalism implications. It will not have substantial direct effects on the states, on the relationship between the national government and the states, or on the distribution of power and responsibilities among the various levels of government.
**G. Executive Order 13175: Coordination With Indian Tribal Governments**
This action does not have Tribal implications, as specified in Executive Order 13175, because the SIP is not approved to apply on any Indian reservation land or in any other area where the EPA or an Indian Tribe has demonstrated that a Tribe has jurisdiction, and will not impose substantial direct costs on Tribal governments or preempt Tribal law. Thus, Executive Order 13175 does not apply to this action.
**H. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety Risks**
The EPA interprets Executive Order 13045 as applying only to those regulatory actions that concern environmental health or safety risks that the EPA has reason to believe may disproportionately affect children, per the definition of “covered regulatory action” in section 2-202 of the Executive Order. This action is not subject to Executive Order 13045 because it does not concern an environmental health risk or safety risk.
**I. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution, or Use**
This action is not subject to Executive Order 13211, because it is not a significant regulatory action under Executive Order 12866.
**J. National Technology Transfer and Advancement Act (NTTAA)**
Section 12(d) of the NTTAA directs the EPA to use voluntary consensus standards in its regulatory activities unless to do so would be inconsistent with applicable law or otherwise impractical. The EPA believes that this action is not subject to the requirements of section 12(d) of the NTTAA because application of those requirements would be inconsistent with the CAA.
**List of Subjects in 40 CFR Part 52**
Environmental protection, Air pollution control, Ammonia, Incorporation by reference, Intergovernmental relations, Nitrogen oxides, Particulate matter, Reporting and recordkeeping requirements, Sulfur oxides, Volatile organic compounds.
Dated: March 20, 2026.
Michael Martucci,
Acting Regional Administrator, Region IX.