SUPPLEMENTARY INFORMATION:

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

Table of Contents

I. Background and Summary of the Proposed Action

II. Public Comments and Responses

III. Final Action

IV. Statutory and Executive Order Reviews

I. Background and Summary of the Proposed Action

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. In 2006, the EPA strengthened the 24-hour PM_2.5 NAAQS by lowering the level from 65 to 35 micrograms per cubic meter (µg/m^[3] ).^[1] The 24-hour standards are based on a three-year average of 98th percentile 24-hour average PM_2.5 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_2.5 concentrations above these levels.

The EPA initially designated the San Joaquin Valley ^[2] as a nonattainment area for the 2006 24-hour PM_2.5 NAAQS effective December 14, 2009,^[3] and subsequently reclassified the area as a “Serious” nonattainment area for these NAAQS on January 20, 2016.^[4] On July 22, 2020, the EPA approved the State's attainment plan for meeting the Serious area attainment planning requirements for the 2006 24-hour PM_2.5 NAAQS (referred to herein as the “SJV PM_2.5 Plan”) and approved the State's request for an extension of the attainment date from December 31, 2019, to December 31, 2024, under section 188(e) of the Act.

On April 2, 2026, the EPA proposed two actions related to the San Joaquin Valley and the 2006 24-hour PM_2.5 NAAQS.^[5] First, the EPA proposed to correct our July 22, 2020, final rule granting a CAA section 188(e) attainment date extension for the 2006 24-hour PM_2.5 NAAQS from December 31, 2019, to December 31, 2024, and to instead deny the extension request. The EPA proposed this action in response to a decision from the Ninth Circuit Court of Appeals in Medical Advocates for Healthy Air et al. vs. EPA (“ Medical Advocates” ),^[6] which established that the EPA was mistaken in its approval of the aggregate commitment in the SJV PM_2.5 Plan. Because the Agency had relied on its approval of the aggregate commitment in its decision to also grant the attainment date extension,^[7] the EPA reasoned that it was in error to grant the extension. Thus, pursuant to CAA section 110(k)(6), the EPA proposed to revise its granting of the extension and to instead deny the extension. The EPA explained that if finalized, the action would have the effect of reestablishing the December 31, 2019 attainment date for the San Joaquin Valley for the 2006 24-hour PM_2.5 NAAQS.

Second, based on our proposal to reestablish the December 31, 2019 attainment date, and in accordance with CAA section 179(c)(1), the EPA proposed to determine that the San Joaquin Valley Serious nonattainment area failed to attain the 2006 24-hour PM_2.5 NAAQS by the December 31, 2019 applicable attainment date. This proposed determination was based on quality-assured and certified data from 2017 through 2019.

The April 2, 2026 proposed rulemaking described the CAA requirements that would apply if the EPA were to finalize the finding of failure to attain.^[8] Our proposal explained that CAA section 189(d) establishes that a state will submit the required SIP revision within 12 months after the applicable attainment date; however, because the submission deadline for a revised plan pursuant to CAA section 189(d) has already passed, it is impossible for the State to submit a revision by that date. Consistent with the EPA's past practice when application of the PM-specific requirements of subpart 4 would be impractical, we proposed to apply the applicable deadline found in CAA subpart 1, section 179(d)(1) and 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 that the San Joaquin Valley area failed to attain the 2006 24-hour PM_2.5 NAAQS.^[9]

( printed page 35420)

Finally, the April 2, 2026 proposed rulemaking explained that a final determination by the EPA of failure to attain the 2006 24-hour PM_2.5 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.^[10]

See our April 2, 2026 proposed rulemaking for additional background and detailed explanation of the rationale for our proposed actions.^[11]

II. Public Comments and Responses

The public comment period for the proposed rulemaking opened on April 2, 2026, the date of its publication in the Federal Register , and closed on May 4, 2026.^[12] During this period, the EPA received 1 comment submission from a coalition of 12 environmental and community organizations (collectively referred to herein as “Commenters”).^[13] The comment submission is included in the docket for this action. A summary of the comment submission and our response thereto follows.

Comment

Commenters express support for the EPA's finding of failure to attain, whether the attainment date was December 31, 2019, or December 31, 2024, and do not take a position on the EPA's proposed error correction.

However, Commenters oppose the EPA's proposed deadline for California to submit the attainment plan required under CAA section 189(d) (referred to herein as a “five percent plan” ^[14] ) within 12 months of the EPA's final determination that the area failed to attain by the December 31, 2019 attainment date. Commenters state that “EPA unlawfully and arbitrarily relies on an inapplicable deadline in Subpart 1 of the Act to set this new deadline. The particulate matter-specific provisions in Subpart 4 and the PM_2.5 SIP Requirements Rule provide for the deadline and those provision [ sic] control here.”

Citing to CAA section 189(d) and 40 CFR 51.1003(c)(2), Commenters state that if the attainment date remains December 31, 2024, “both Subpart 4 and the PM_2.5 SIP Requirements Rule require California to submit a five percent plan by December 31, 2025.” Commenters also assert that if the attainment date is reset to December 31, 2019, the State shall submit the five percent plan by December 31, 2020. Commenters note that both of these due dates have passed.

As a result, Commenters argue that “EPA's proposed rationale for utilizing the Subpart 1 general provisions to govern the deadline for the five percent plan is nonsensical and arbitrary because the five percent plan is past due even if EPA does not correct the attainment date.” They state that “California knew or should have known it would fail to attain the standard and therefore should have prepared and submitted a five percent plan by December 31, 2025.” Commenters explain that in their view, CAA section 189(d) mandates the deadline for submission of the five percent plan and does not contain an exception to this deadline nor any discretion to the EPA to apply the subpart 1 deadline if compliance is impracticable or impossible. Thus, they argue that “the plain language and best reading of section 189(d) provide the deadline for a five percent plan and EPA's proposed action to depart from that deadline is unlawful and arbitrary.”

Regarding the EPA's citation in the proposed rulemaking to Ninth Circuit Court of Appeals case law regarding use of subpart 1 deadlines when compliance with a subpart 4 deadline is impracticable, Commenters state that the EPA's reliance on the Association of Irritated Residents v. EPA, 423 F.3d 989 (9th Cir. 2005) case (“ AIR”), is incorrect. Commenters state that the problem in AIR was that subpart 4 did not provide an attainment date for a CAA section 189(d) five percent plan. They state that the Court affirmed the use of a subpart 1 date because CAA section 189(d) did not provide an attainment date, and nothing in subpart 4 prohibited the EPA from relying on subpart 1 to set a new attainment date. Commenters argue that the issue of when a CAA section 189(d) plan is due is different because “section 189(d) expressly answers the question of when a state must submit a five percent plan.” They argue that this CAA section 189 statutory language controls.

Finally, Commenters state that the fact that the deadline set forth in CAA section 189(d) has passed does not leave the EPA without a path forward, asserting that the “statutory scheme” requires the EPA to make a determination that the State has failed to submit a complete SIP, as provided in CAA section 110(k)(1)(B).

Response

We agree with the Commenters that both subpart 4 of the statute and the regulations implementing that part of the statute provide that a state shall submit a CAA section 189(d) five percent plan within 12 months of failing to attain by the applicable attainment date; ^[15] however, neither subpart 4 nor our implementing regulations establish a deadline for submittal of a plan if the date provided in CAA section 189(d) has already passed. Commenters suggest that the EPA must read the statute to require the EPA to use a retroactive deadline and to immediately issue a finding of failure to submit. Such a reading would start sanctions clocks against the State and empower the EPA to immediately regulate in place of the State because the State did not take an action that it had neither notice nor legal obligation to undertake at the time urged by the Commenters. For the reasons set forth in the remainder of this section, and consistent with the CAA's principles of cooperative federalism, we do not agree that this is the best reading of the statute.

CAA section 179 and implementing regulations at 40 CFR 52.31 establish a framework that imposes sanctions upon states in the event that the EPA finds that a state has failed to take a statutorily-required action, such as submittal of a required nonattainment plan, and fails to timely correct this deficiency. Under this framework, 18 months after such a finding an area that fails to correct the deficiency will be subject to increased emissions offset requirements for new or modified sources in the area and if such deficiency persists 24 months after the finding, the area will face the loss of Federal highway funds—a potentially ( printed page 35421) severe consequence for states relying on Federal highway funding.^[16]

Moreover, in addition to sanctions, CAA section 110(c) requires the EPA to implement a Federal implementation plan (FIP) “ at any time within two years after the Administrator . . . finds that a state has failed to make a required submission. . . .” ^[17] Importantly, the Act allows the EPA to issue a FIP “at any time” following such a finding.

Commenters essentially ask the EPA to resurrect a deadline for plan submittal that has long passed and to enforce the consequences of missing this retroactively-imposed deadline upon the State by issuing a finding of failure to submit. Such a finding would immediately start sanctions clocks and empower the EPA to issue a FIP, which would impose the EPA's direct regulatory authority on emissions sources in the San Joaquin Valley.

Given the Act's carefully constructed balance between state and Federal authority, the EPA believes that a clear indication from Congress would be required in order to interpret the statute in a way that would lead to the type of extraordinary results that Commenters suggest. The EPA does not believe that Congress intended the EPA to be able to impose sanctions clocks on a state by determining “state failure” to meet a deadline that it did not have notice of at the time. Even more so the EPA does not believe that Congress intended the EPA to be able to immediately impose its own regulatory requirements in place of a state's based on such a retroactive finding.

Commenters appear to suggest that the State should have submitted such a plan without an EPA finding that the area failed to attain. They write that “California knew or should have known it would fail to attain the standard and therefore should have prepared and submitted a five percent plan by December 31, 2025.” Such an anticipatory submission is not required under the Act.

A CAA section 189(d) five percent plan is required “[i]n the case of a Serious [particulate matter] nonattainment area in which the [particulate matter] standard is not attained by the applicable attainment date.” However, the statute tasks the EPA with determining whether or not an area has attained the standard by a particular date.^[18] A state is not free to substitute its judgment for the EPA's on this question. Accordingly, a state is not required to submit a CAA section 189(d) five percent plan until the EPA makes a finding that the area has failed to attain the standard by the applicable attainment date.^[19] A state is not required to guess whether the EPA will determine that the area attained and submit a plan based on the possibility that the EPA will find that the area failed to attain by the applicable deadline. While a state is free to begin to work on a plan if it expects that it may not attain the standard by the applicable attainment date, the best reading of the Act is that it does not empower the EPA to compel a state to submit a five percent plan in the absence of an EPA determination that an area failed to attain by the applicable deadline. By the same token, the best reading of the statute is that it does not require imposition of immediate sanction clocks or permit the EPA to issue an immediate FIP if the state does not submit a plan in advance of an EPA finding of failure to attain.^[20]

In addition to such a submission not being required until the EPA issues a finding of failure to attain, the state will lack information necessary to make such a submission until the EPA issues such a finding. In the AIR case, cited in the EPA's proposal and in the comment, the Ninth Circuit Court of Appeals upheld the EPA's application of the subpart 1 attainment date provisions for the purpose of a CAA section 189(d) five percent plan. Critically, the CAA section 189(d) attainment date established by the EPA was “as expeditiously as practicable, but no later than 5 years from the date of [the EPA's finding of failure to attain ]. . . .rdquo; ^[21] Because the outermost attainment date for a CAA section 189(d) five percent plan depends on the date of the EPA's finding that the area failed to attain, the State lacks information that is critical to its CAA section 189(d) five percent plan submission until the EPA issues a finding of failure to attain. Accordingly, Commenters' suggestion that California should have submitted its plan by December 31, 2025, is simply not practical. The State cannot be expected to make an attainment plan submission without knowing the outermost attainment date. It is not until the EPA issues a finding of failure to attain that a state is on notice that the area has failed to attain and is in a position to determine the new date by which the CAA section 189(d) five percent plan must show attainment. Accordingly, the EPA believes that a state must have a reasonable amount of time after that point to do the work of designing and submitting the updated plan (including the necessary public engagement required under the Act).

The statute is also clear that Congress intended states to have sufficient time to adopt an updated plan before the threat of sanctions and a FIP are imposed. While Commenters suggest that the “statutory scheme” requires the EPA to implement a retroactive deadline and issue a finding of failure to submit, the EPA believes this is an overly narrow reading of the statute. The statutory scheme, both in subpart 1 and in subpart 4, acknowledges the need for a state to have a reasonable period of time to develop its plan. In subpart 1, which the EPA proposed to apply in this instance because compliance with subpart 4 is impracticable, Congress has given states a year from the EPA's finding of failure to attain to submit an updated plan.^[22] However, subpart 4 as well evinces Congress's intent to provide states with time to develop and submit a plan. Because the Act provides up to six months after the attainment deadline for the EPA to make a determination of attainment,^[23] the deadline in CAA section 189(d) for submittal of a plan within twelve months after the attainment date suggests that Congress intended a state to have 6 to 12 months from the EPA's attainment determination to submit its plan before the EPA would be able to start sanctions and FIP clocks. Accordingly, the EPA's proposed ( printed page 35422) deadline of 12 months from the effective date of our final action is both expressly called for by subpart 1 and within the range of dates that the statute would provide under the prospective application of subpart 4. The EPA believes that this interpretation is more in line with the statutory scheme than retroactively applying a December 31, 2020 deadline that the State could not possibly make and then punishing the State for failing to make this deadline.

This interpretation is in line with past Agency actions in which unusual circumstances led to situations in which the CAA's statutory deadlines had passed.

In Wildearth Guardians v. EPA, 830 F.3d 529 (D.C. Cir. 2016) (“ Wildearth Guardians”), the EPA, following a court decision clarifying the applicability of subpart 4 versus subpart 1 of the statute, “made certain adjustments to those deadlines in an effort to avoid treating states as having already missed deadlines of which they were never aware.” Petitioners challenged the EPA's action arguing that the EPA was bound to apply the statutory deadlines regardless of whether those deadlines had already passed, and that the EPA was obligated to issue immediate findings of failure to submit for those dates that had lapsed. The court held that “EPA reasonably acted within its statutory authority in adopting new deadlines aimed to avoid imposing retroactive burdens on states seeking to achieve compliance with governing air quality standards.”

Similarly, in Sierra Club v. EPA, 356 F.3d 296 (D.C. Cir. 2004) (“ Sierra Club” ) the EPA reclassified the District of Columbia from “Serious” to “Severe” nonattainment. The Agency established a new deadline for the District's submission of a Severe-area nonattainment plan because the original statutory deadline for such plans had already passed. The Court rejected Sierra Club's argument that the original statutory deadline should govern, reasoning that such a result “would give the reclassification retroactive effect by holding the States in default of their submission obligations before the events necessary to trigger that obligation (reclassification) occurred.” ^[24]

In addition to the courts consistently upholding the EPA's authority to administer the statute in a way that avoids holding states to retroactive deadlines, courts have also looked favorably upon the EPA looking to subpart 1 when a workable deadline is not found in subpart 4. In AIR, the EPA applied the CAA subpart 1, section 179, requirements to set the outermost attainment date for a CAA section 189(d) five percent plan submission because subpart 4 was silent as to the attainment date requirements for such a plan. Petitioners challenged the EPA's application of the subpart 1 deadline, arguing that the more specific subpart 4 provisions foreclosed the EPA's use of the more general subpart 1 requirements. The court held that no language in subpart 4 prohibits the EPA's application of the general provisions and that the overall statutory scheme supported the EPA's position that the EPA may look to CAA section 179 to set a new attainment deadline.^[25]

The EPA believes that the same principles that decided those cases apply here. Most notably, as in Wildearth Guardians, the EPA is here faced with the unusual circumstance of a court decision impacting the applicable deadlines for attainment planning. Here, as explained in our proposal, the Ninth Circuit's Medical Advocates decision vacated part of the EPA's rule approving a prior extension of the attainment deadline. In this action, the EPA is correcting its erroneous granting of a CAA section 188(e) attainment date extension for the area, resetting the deadline to December 31, 2019. Because the December 31, 2020 submission due date that would follow from that correction has long passed, the EPA believes that it is appropriate to similarly set a prospective deadline to avoid the consequences that would come with the retroactive application of the December 31, 2020 deadline. As the EPA explained in the action that was the subject of the Sierra Club decision, “[a] failure to meet an obligation, especially one accompanied by sanctions, cannot occur in advance of the imposition of that obligation.” ^[26]

In light of the consequences of adopting an interpretation that would retroactively hold the State to a deadline that it had no notice of at the time, the EPA concludes, as it did in the AIR case, that looking to subpart 1 for a prospective deadline for the State is most in line with the text of the Act and the overall statutory scheme.

III. Final Action

For the reasons discussed in our proposed action and herein, the EPA is finalizing the correction to our previous action erroneously granting a CAA section 188(e) attainment date extension for the 2006 24-hour PM_2.5 NAAQS in the San Joaquin Valley and is now finalizing our denial of the extension. With this action, we are reestablishing the December 31, 2019 unextended attainment date for the San Joaquin Valley for the 2006 24-hour PM_2.5 NAAQS.

Based on our final action reestablishing the December 31, 2019 attainment date, and in accordance with CAA section 179(c)(1), the EPA is finalizing our determination that the San Joaquin Valley Serious PM_2.5 nonattainment area failed to attain the 2006 24-hour PM_2.5 NAAQS by the applicable attainment date of December 31, 2019. This determination is based on quality-assured and certified air quality monitoring data from 2017 through 2019.

As a result of the final determination that the San Joaquin Valley failed to attain the 2006 24-hour PM_2.5 NAAQS, the State of California is required under CAA sections 179(d) and 189(d) to submit, within one year of this final determination, a revision to the SIP for the San Joaquin Valley.^[27] The SIP revision must, among other elements, demonstrate expeditious attainment of the standards within the time period provided under CAA section 179(d), provide for an annual reduction in the emissions of PM_2.5 or a PM_2.5 precursor pollutant within the area of not less than five percent until attainment,^[28] demonstrate reasonable further progress, and include contingency measures. The requirement for a new attainment demonstration under CAA section 189(d) also triggers the requirement for a SIP revision for quantitative milestones under CAA section 189(c) that are to be achieved every three years until redesignation to attainment.

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 ( printed page 35423) 172(a)(2). Under 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 five years from the date of the final determination of failure to attain. 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.

Finally, as a result of this final determination that the San Joaquin Valley failed to attain the 2006 24-hour PM_2.5 NAAQS by the Serious area attainment date, the State is required to implement its contingency measures for these NAAQS in accordance with 40 CFR 51.1014.^[29]

IV. 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 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, will 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. It will neither impose substantial direct costs on federally recognized Tribal governments nor 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.

K. Congressional Review Act (CRA)

This action is subject to the 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).

L. Petitions for Judicial Review

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 August 10, 2026. Filing a petition for reconsideration by the Administrator of this final rule does not affect the finality of this rule 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)).

Part 52, chapter I, title 40 of the Code of Federal Regulations is amended as follows:

91 FR 35418