SUPPLEMENTARY INFORMATION:

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

Table of Contents

I. Statutory Requirements and the EPA's Considerations for Evaluating Infrastructure SIPs

II. Background and Withdrawal of the EPA's Prior Proposed Partial Approval and Partial Disapproval of PSD Requirements Under CAA sections 110(a)(2)(C), 110(a)(2)(D)(i)(II), 110(a)(2)(D)(ii), and 110(a)(2)(J)

III. The EPA's Updated Policy Rationale and Summary of the EPA's Proposed Partial Approval and Partial Disapproval

IV. Request for Public Comments

V. Statutory and Executive Order Reviews

I. Statutory Requirements and the EPA's Considerations for Evaluating Infrastructure SIPs

The EPA has historically referred to SIP submittals made for the purpose of satisfying the requirements of CAA sections 110(a)(1) and 110(a)(2) as “infrastructure SIP” (I-SIP) submittals. Although the term “infrastructure SIP” does not appear in the CAA, the EPA uses the term to distinguish this particular type of SIP submittal from submittals that are primarily intended to satisfy other SIP requirements under the CAA, such as “nonattainment SIP” or “attainment SIP” submittals intended to address the nonattainment planning requirements of CAA title I part D, “regional haze SIP” submittals required by the EPA rule to address the visibility protection requirements of CAA section 169A, and nonattainment new source review (NSR) permit program submittals to address the permit requirements of CAA title I part D.

CAA section 110(a)(1) addresses the timing and general requirements for infrastructure SIP submittals, and CAA section 110(a)(2) provides details concerning the required content of these submittals. Notably, section 110(a)(1) of the Act clearly requires that each State adopt and submit an infrastructure SIP ( printed page 50743) for the implementation, maintenance, and enforcement of each NAAQS promulgated by the EPA, and that the EPA act on such SIP submittals, while CAA section 110(a)(2) provides an extensive list of required elements, some with provisions pertaining directly to legal authority, some with provisions pertaining to substantive program requirements, and some others which pertain to requirements for both authority and substantive program provisions. The EPA has historically asserted that this list of required provisions leads to ambiguities concerning what is required for inclusion in any SIP submittal subject to CAA section 110(a)(2). For example, CAA section 110(a)(2) requires that “each” SIP submittal must meet the list of requirements therein. However, the EPA has long noted that this literal reading of the statute is internally inconsistent and would create a conflict with the nonattainment provisions in CAA title I part D, which specifically address nonattainment SIP requirements.^[1] Section 110(a)(2)(I) of the CAA pertains to nonattainment SIP requirements, and part D addresses when attainment plan SIP submittals to address nonattainment area requirements are due. Moreover, CAA section 172(b) requires the EPA to establish a schedule for submittal of such plans for certain pollutants when the Administrator promulgates the designation of an area as nonattainment, and CAA section 107(d)(1)(B) allows up to two years, or in some cases three years, for such designations to be promulgated.^[2] As another example, CAA section 172(c)(7) requires that attainment plan SIP submittals required by part D have to meet only the “applicable requirements” of CAA section 110(a)(2). Thus, the EPA has interpreted this provision such that attainment plan SIP submittals must meet the requirements of CAA section 110(a)(2)(A) regarding enforceable emissions limits and control measures and CAA section 110(a)(2)(E)(i) regarding air agency resources and authority. As this example illustrates, each type of SIP submittal may implicate some elements of CAA section 110(a)(2) but not others, and rather than apply all the stated requirements of CAA section 110(a)(2) in a strict literal sense, as is the case for CAA section 110(a)(1), the EPA must determine how provisions of CAA section 110(a)(2) are applicable for a particular SIP submittal, including infrastructure SIPs.

In the context of a specific NAAQS, the EPA has also historically recognized that CAA section 110(a)(2) should also be read and interpreted in a logical context with respect to how infrastructure SIP submittal requirements should be structured. For example, the monitoring requirements that a State might need to meet in its infrastructure SIP submittal for purposes of CAA section 110(a)(2)(B) could be very different for different pollutants, because the content and scope of a State's infrastructure SIP submittal to meet this element might vary by NAAQS promulgation.^[3] Thus, the EPA notes that the best reading of CAA section 110(a)(2) can vary for each new or revised NAAQS, and therefore, requirements for the States' attendant infrastructure SIP submittals for each NAAQS may be different.

Given this, the EPA believes that it is appropriate to interpret the requirements of CAA section 110(a)(2) in the context of acting on individual SIP submittals. In other words, the EPA assumes that Congress could not have intended that each and every SIP submittal, regardless of the NAAQS in question or the history of SIP development for the relevant pollutant, would meet each of the requirements, or meet each of them in the same way. Therefore, the EPA reviews infrastructure SIP submittals against the list of elements in CAA section 110(a)(2), but only applies the required elements for the new or revised NAAQS. To this end, the EPA has issued guidance documents to make recommendations to States as to how their infrastructure SIP submittals can be structured to meet the requirements of CAA section 110(a)(2). The EPA most recently issued guidance for infrastructure SIPs on September 13, 2013 (“2013 Infrastructure SIP Guidance”).^[4] One notable example from the 2013 Infrastructure SIP Guidance is how it gives simpler recommendations with respect to carbon monoxide than other NAAQS pollutants to meet the visibility requirements of CAA section 110(a)(2)(D)(i)(II) because carbon monoxide does not affect visibility. As a result, an infrastructure SIP submittal for any future new or revised NAAQS for carbon monoxide need only state this fact in order to address the visibility prong of CAA section 110(a)(2)(D)(i)(II).

Historically, the EPA has elected to use guidance in order to explain our current best interpretation of the relevant statute in lieu of promulgating regulations to govern CAA section 110(a)(2) infrastructure SIP requirements. However, the CAA ultimately governs what is required in infrastructure SIP submittals, regardless of whether EPA has provided advance guidance speaking to such requirements.

Section 110(a)(1) of the CAA requires States to submit to the EPA, within three years after the promulgation of a new or revised NAAQS, a SIP submission that meets the applicable requirements of CAA section 110(a)(2) to provide for the implementation, maintenance, and enforcement of the new or revised NAAQS.

CAA section 110(a)(2) includes several provisions that reference PSD-related requirements for the regulation of new and modified major stationary sources. Specifically:

• CAA section 110(a)(2)(C) requires States to include a program for the regulation of new and modified major stationary sources, including a permit program as required by title I part C of the CAA;
• CAA section 110(a)(2)(D)(i)(II) requires States to include “adequate provisions” to prohibit interference with any other State's PSD program;
• CAA section 110(a)(2)(D)(ii) requires States to include “adequate provisions” to ensure compliance with CAA section 126, which requires States to notify neighboring air agencies of potential impacts from new and modified major stationary sources of air pollution; and
• CAA section 110(a)(2)(J) requires States to meet the applicable requirements of part C (relating to PSD).

II. Background and Withdrawal of the EPA's Prior Proposed Partial Approval and Partial Disapproval of PSD Requirements Under CAA Sections 110(a)(2)(C), 110(a)(2)(D)(i)(II), 110(a)(2)(D)(ii), and 110(a)(2)(J)

On January 15, 2013 the EPA promulgated a revision to the PM_2.5 NAAQS (2012 PM_2.5 NAAQS), lowering ( printed page 50744) the level of the primary standard to 12.0 micrograms per cubic meter (µg/m^[3] ), while maintaining the secondary standard.^[5] The ADEQ submitted two SIP revisions to address the infrastructure SIP requirements in CAA sections 110(a)(1) and 110(a)(2) for the 2012 PM_2.5 NAAQS. This action pertains only to ADEQ's December 11, 2015 submittal, which addresses the PSD-related requirements of CAA section 110, titled “Arizona State Implementation Plan Revision for the 2012 Fine Particulate Matter (PM_2.5) National Ambient Air Quality Standard” (“2012 PM_2.5 I-SIP submittal”).^[6]

On June 13, 2024,^[7] the EPA proposed to partially approve and partially disapprove Arizona's 2012 PM_2.5 I-SIP submittal with respect to the PSD-related requirements of CAA sections 110(a)(2)(C), 110(a)(2)(D)(i)(II), 110(a)(2)(D)(ii), and 110(a)(2)(J). Our proposed partial disapproval of these elements was based, at the time, on deficiencies we identified with respect to PSD permitting of greenhouse gases (GHGs) in all permitting jurisdictions in Arizona, as well as deficiencies with respect to PSD permitting of all NSR-regulated pollutants in Pima County. Our proposed partial approval for the PSD-related requirements of Arizona's submittal applied to those Arizona permitting jurisdictions with a SIP-approved PSD permitting program covering all other NSR-regulated pollutants. Our proposed action provided a 30-day public comment period during which we received four comments. One of the comments failed to raise issues germane to the proposed action, which we determined did not necessitate a response. There were three additional comments concerning the ADEQ's PSD permitting program.^[8]

On December 18, 2025,^[9] we took final action on most of what we proposed in our June 13, 2024 rulemaking. However, we deferred action on the PSD-related requirements of CAA sections 110(a)(2)(C), 110(a)(2)(D)(i)(II), 110(a)(2)(D)(ii), and 110(a)(2)(J). Consequently, we did not respond to the comments concerning ADEQ's PSD permitting program.

In this proposed action, we are withdrawing our June 13, 2024 proposed action insofar as it pertained to the PSD-related requirements of CAA sections 110(a)(2)(C), 110(a)(2)(D)(i)(II), 110(a)(2)(D)(ii), and 110(a)(2)(J) for the 2012 PM_2.5 NAAQS. We are now re-proposing partial approval and partial disapproval of these elements based on a change in policy, as discussed in Section III of this document. Commenters who would like the EPA to consider any comments submitted on the June 13, 2024 proposed rule that may be relevant to this re-proposal must resubmit such comments during the comment period for this proposed action.

III. The EPA's Updated Policy Rationale and Summary of the EPA's Proposed Partial Approval and Partial Disapproval

In our June 13, 2024 action, we proposed to partially disapprove the PSD-related requirements of the Arizona I-SIP submittal for the 2012 PM_2.5 NAAQS based on our interpretation at that time of CAA section 110(a)(2)(C). Historically, we have read CAA section 110(a)(2)(C) to require that each infrastructure SIP submission demonstrate that the State and its relevant permitting authorities have SIP-approved PSD permitting programs that meet certain “structural” elements for all NSR pollutants regulated under CAA title I part C, and not just for those relevant to the new or revised NAAQS that prompted the infrastructure SIP submittal.^[10] As we stated in our 2013 I-SIP guidance: “There is no specific language in the last clause of [CAA section 110(a)(2)(C)] that restricts its application to only those provisions of CAA title I part C that pertain to the particular new or revised NAAQS addressed by the particular infrastructure SIP action. Because the scope of CAA title I part C is comprehensive (covering all pollutants subject to regulation under the CAA, including GHG), the EPA likewise reads the unrestricted reference to CAA title I part C . . . to mean that this provision has the same scope as CAA title I part C itself.”

At the same time, we have noted in rulemakings and the 2013 I-SIP guidance that the broad scope of 110(a)(2)(C) with respect to PSD permitting can make it difficult for air agencies and the EPA to address substantive issues in an I-SIP submission in a reasonable and timely fashion.^[11] We have thus found that it is reasonable to evaluate the PSD permitting subelement of 110(a)(2)(C) on the basis that each air agency's PSD program contains certain “structural” permitting provisions necessary for administration of the program. The basic structural elements of a PSD program that the EPA looks for in each I-SIP submission include:

1. Provisions identifying oxides of nitrogen (NO_X) as an ozone precursor;

2. Provisions to regulate PM_2.5, including condensable PM, and its precursor emissions (sulfur dioxide (SO₂) in all areas, and NO_X, and/or volatile organic compounds as appropriate);

3. Provisions to regulate PSD increments consistent with the requirements of the EPA's PSD implementation rule for PM_2.5; and

4. Provisions to regulate GHGs.

Historically, the EPA has interpreted a submittal's adequate satisfaction of the PSD-related requirements under CAA section 110(a)(2)(C) as extending to the PSD-related requirements of CAA sections 110(a)(2)(D)(i)(II), 110(a)(2)(D)(ii), and 110(a)(2)(J), and conversely, disapproval of certain PSD-related requirements under CAA section 110(a)(2)(C) extends to the related requirements found under CAA sections 110(a)(2)(D)(i)(II), 110(a)(2)(D)(ii), and 110(a)(2)(J). As such, our June 13, 2024 proposed partial disapproval was based on deficiencies with respect to the requirements for PSD permitting of greenhouse gases (GHGs) in all Arizona permitting jurisdictions and deficiencies with respect to PSD permitting of all NSR-regulated pollutants in Pima County.^[12]

In this proposed action, the EPA is announcing a new interpretation of CAA sections 110(a)(2)(C), 110(a)(2)(D)(i)(II), 110(a)(2)(D)(ii), and 110(a)(2)(J), such that, for the PSD-related requirements, infrastructure SIPs need only demonstrate that State and county PSD permitting programs adequately regulate the pollutant(s) for which the I-SIP is being submitted. This new position reflects a change in policy as to the basic structural elements of a PSD permitting program required to adequately satisfy the relevant requirements of CAA sections 110(a)(2)(C), 110(a)(2)(D)(i)(II), 110(a)(2)(D)(ii), and 110(a)(2)(J). However, the EPA believes that this new interpretation better aligns with the overall purpose of the statute. In particular, this interpretation better aligns with the language in CAA section ( printed page 50745) 110(a)(1), which states that within three years of promulgation of a new NAAQS, States are required to submit a plan that provides for “implementation, maintenance, and enforcement of such. . . standard” (emphasis added). The fact that CAA section 110(a)(1) specifically states that the obligation is for “such . . . standard,” referencing the NAAQS that triggered the submittal, suggests that Congress intended to limit the scope of the obligation to just the newly promulgated NAAQS.^[13] In addition, the fact that CAA section 110(a)(1) specifically ties the obligation to submit a new plan to a period of time immediately following the promulgation of a new NAAQS also supports EPA's new interpretation that the obligation for the I-SIP relates just to the new standard. The EPA has the discretion and authority to change policy. In FCC v. Fox Television Stations, Inc., the U.S Supreme Court plainly stated that an agency is free to change a prior policy and “need not demonstrate . . . that the reasons for the new policy are better than the reasons for the old one; it suffices that the new policy is permissible under the statute, that there are good reasons for it, and that the agency believes it to be better.” ^[14]

The EPA's new policy is that for the PSD-related requirements of CAA sections 110(a)(2)(C), 110(a)(2)(D)(i)(II), 110(a)(2)(D)(ii), and 110(a)(2)(J), infrastructure SIP submittals need only demonstrate that State and county PSD permitting programs adequately regulate the pollutant(s) for which the I-SIP is being submitted. The EPA believes that this new interpretation better aligns with the requirements of the statute, in particular, that infrastructure SIP submissions demonstrate adequate provisions against the relevant portions of CAA section 110(a)(2), but only to the extent they are necessary to assure the implementation, maintenance, and enforcement of the specific NAAQS for which an infrastructure SIP is required under CAA section 110(a)(1), and not all air pollutants considered in CAA title I part C. To this end, the EPA now finds the following basic structural element(s) appropriate, depending on the NAAQS the submittal is intended to address:

1. Provisions identifying NO_X as an ozone precursor;

2. Provisions to regulate PM_2.5, including condensable PM, and its precursor emissions (sulfur dioxide (SO₂) in all areas, and NO_X, and/or volatile organic compounds as appropriate); and

3. Provisions to regulate PSD increments consistent with the requirements of the EPA's PSD implementation rule for PM_2.5.

As such, the EPA believes that as long as an infrastructure SIP submittal for the 2012 PM_2.5 NAAQS demonstrates SIP-approved provisions, for all relevant permitting authorities, in accordance with structural elements 2 (provisions to regulate PM_2.5, including condensable PM_2.5, and its precursors) and 3 (provisions to regulate PSD increments for PM_2.5 ) listed above, it would satisfy the PSD-related requirements of CAA sections 110(a)(2)(C), 110(a)(2)(D)(i)(II), 110(a)(2)(D)(ii), and 110(a)(2)(J). If a permitting authority instead implements one or more of these basic structural elements by means of a Federal PSD implementation plan, the EPA maintains that this does not adequately satisfy the PSD-related requirements under CAA section 110(a)(2). Because Arizona's submittal was inconsistent with our previous interpretation of the Act and past rulemakings on the PSD-related provisions of CAA section 110(a)(2), the new interpretation we are proposing here does not involve a cognizable reliance issue for Arizona.^[15]

Under this new interpretation of the relevant CAA provisions, we evaluated Arizona's 2012 PM_2.5 I-SIP submittal and the relevant existing provisions of the Arizona SIP for compliance with the infrastructure SIP PSD-related requirements of CAA sections 110(a)(2)(C), 110(a)(2)(D)(i)(II), 110(a)(2)(D)(ii), and 110(a)(2)(J). In our evaluation, we found that the State has SIP-approved provisions that adequately satisfy the relevant structural elements 2 and 3 for the ADEQ, MCAQD, and PCAQCD permitting authorities with respect to the 2012 PM_2.5 NAAQS. We also found that PDEQ does not have a SIP-approved PSD program and instead implements a comprehensive PSD Federal implementation plan (FIP) for PM_2.5 and its precursors.

Therefore, the EPA now proposes to approve Arizona's 2012 PM_2.5 I-SIP submittal with respect to the 2012 PM_2.5 NAAQS for the following CAA requirements to the extent they apply to the PSD permitting jurisdictions of ADEQ, MCAQD, and PCAQCD:

• CAA section 110(a)(2)(C)—Program for regulation of new and modified major source stationary sources;
• CAA section 110(a)(2)(D)(i)(II)—Interference with PSD (prong 3);
• CAA section 110(a)(2)(D)(ii)—Interstate pollution abatement, CAA section 126; and
• CAA section 110(a)(2)(J)—PSD.

The EPA also proposes to disapprove Arizona's 2012 PM_2.5 I-SIP submittal with respect to the 2012 PM_2.5 NAAQS for the same CAA requirements to the extent they apply to the PSD permitting jurisdiction of PDEQ.

Although the Arizona SIP remains deficient with respect to PSD permitting of PM_2.5 and its precursors in the PDEQ permitting jurisdiction, as described, these deficiencies are adequately addressed by an existing FIP. If finalized, this disapproval of Arizona's SIP would not create any new consequences for Arizona, the county agency, or the EPA, as the county agency already implements the EPA's Federal PSD program at 40 CFR 52.21, pursuant to delegation agreements, for PM_2.5 and its precursors. This disapproval, if finalized, would also not result in any offset or highway sanctions, which are not triggered by disapprovals of infrastructure SIPs under CAA section 110(a)(2).

IV. Request for Public Comments

The EPA is soliciting public comments on this proposed rulemaking. We will accept comments from the public for the next 30 days. We will consider any comments received before taking final action.

V. Statutory and Executive Order Reviews

Under the CAA, the Administrator is required to approve a SIP submission that complies with the provisions of the Act and applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, the EPA's role is to review State choices, and approve those choices if they meet the minimum criteria of the Act. Accordingly, this proposed rulemaking proposes to partially approve and partially disapprove State law as meeting Federal requirements and does not impose additional requirements beyond those imposed by State law.

Additional information about these statutes and Executive Orders can be found at 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 (58 FR 51735, October 4, 1993)

This action is not a significant regulatory action and was therefore not submitted to the Office of Management and Budget (OMB) for review. ( printed page 50746)

B. Executive Order 14192: Unleashing Prosperity Through Deregulation (90 FR 9065, February 6, 2025)

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) (44 U.S.C. 3501 et seq.)

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) (5 U.S.C. 601 et seq.)

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) (Pub. L. 104-4)

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 (64 FR 43255, August 10, 1999)

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 (65 FR 67249, November 9, 2000)

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 (62 FR 19885, April 23, 1997)

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. Therefore, this action is not subject to Executive Order 13045 because it merely proposes to partially approve and partially disapprove State law as meeting Federal requirements. Furthermore, the EPA's Policy on Children's Health does not apply to this action.

I. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution, or Use (66 FR 28355, May 22, 2001)

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) (15 U.S.C. 272 Note)

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.

(Authority: 42 U.S.C. 7401 et seq.)

91 FR 50742