6560-50-P
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R09-OAR-2023-0539; FRL-11747-01-R9]
Partial Approval and Partial Disapproval of Air Quality State Implementation Plans;
Arizona; Infrastructure Requirements for Fine Particulate Matter
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
SUMMARY: The Environmental Protection Agency (EPA) is proposing to partially approve
and partially disapprove a revision to the Arizona state implementation plan (SIP) as meeting the
requirements of the Clean Air Act (CAA) for the implementation, maintenance, and enforcement
of the 2012 fine particulate matter (PM2.5) national ambient air quality standards (NAAQS or
“standards”). As part of this action, the EPA is proposing to approve regulatory provisions into
the Arizona SIP. The EPA is seeking public comment on this proposed action and will accept
comments from the public on this proposal for the next 30 days.
DATES: Any comments must arrive by [INSERT DATE 30 DAYS AFTER DATE OF
PUBLICATION IN THE FEDERAL REGISTER].
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-OAR-2023-0539
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: Michael Dorantes, Geographic Strategies and
Modeling Section (AIR-2-2), EPA Region IX, (415) 972-3934, dorantes.michael@epa.gov.
SUPPLEMENTAL INFORMATION: Throughout this document, “we,” “us,” and “our” refer
to the EPA.
Table of Contents
I. The EPA’s Approach to Reviewing Infrastructure SIPs
II. Background
A. Statutory Framework
B. Regulatory Background
III. State Submittals
A. Infrastructure SIP Submittal
B. Revised Rules and Regulations
IV. The EPA’s Evaluation and Proposed Action
A. Proposed Approvals and Partial Approvals
B. Proposed Partial Disapprovals
C. Incorporation of Rules into Arizona’s State Implementation Plan
D. Deferred Action
E. Revising Air Quality Control Regions and Evaluating Emergency Episode Planning
Requirements for PM2.5 in Arizona
F. Request for Public Comments
V. Incorporation by Reference
VI. Statutory and Executive Order Reviews
I. The EPA’s Approach to Reviewing 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” 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 intended to satisfy other
SIP requirements under the CAA, such as “nonattainment SIP” or “attainment SIP” submittals to

address the nonattainment planning requirements of CAA title I part D, “regional haze SIP”
submittals required by EPA rule to address the visibility protection requirements of section
169A, and nonattainment new source review (NSR) permit program submittals to address the
permit requirements of CAA title I part D.
Section 110(a)(1) of the Act requires that each State adopt and submit an infrastructure
SIP for the implementation, maintenance, and enforcement of each NAAQS promulgated by the
EPA, and that the EPA act on such SIP submittals. They are intended to address basic structural
SIP requirements for new or revised NAAQS including, but not limited to, legal authority,
regulatory structure, resources, permit programs, monitoring, and modeling necessary to assure
attainment and maintenance of the standards.
Herein, the EPA is acting on SIP submittals from Arizona that address the infrastructure
requirements of CAA sections 110(a)(1) and 110(a)(2) with respect to the primary and secondary
2012 PM2.5 NAAQS. Under section 110(a)(1), states are required to submit infrastructure SIPs
within three years (or such shorter period as the Administrator may prescribe) after the
promulgation of a national primary ambient air quality standard (or any revision thereof). The
statute directly imposes on States the duty to make these SIP submittals, and the requirement to
make the submittals is not conditioned upon the EPA taking any action other than promulgating
a new or revised NAAQS. Section 110(a)(2) includes a list of specific “elements” that each such
infrastructure SIP submittal must address.
CAA section 110(a)(1) addresses the timing and general requirements for infrastructure
SIP submittals, and section 110(a)(2) provides more details concerning the required contents of
these submittals. The list of required elements provided in section 110(a)(2) contains a wide
variety of disparate provisions, some of which pertain to required legal authority, some of which
pertain to required substantive program provisions, and some of which pertain to requirements

for both authority and substantive program provisions.1 The EPA therefore believes that, while
the timing requirement in section 110(a)(1) is unambiguous, some of the other statutory
provisions are ambiguous. In particular, the EPA believes that the list of required elements for
infrastructure SIP submittals provided in section 110(a)(2) contains ambiguities concerning what
is required for inclusion in an infrastructure SIP submittal.
The following examples of ambiguities illustrate the need for the EPA to interpret some
CAA section 110(a)(1) and section 110(a)(2) requirements with respect to infrastructure SIP
submittals for a given new or revised NAAQS. One example of ambiguity is that section
110(a)(2) requires that “each” SIP submittal must meet the list of requirements therein, while 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.2 Section 110(a)(2)(I) pertains to nonattainment SIP
requirements, and part D addresses when attainment plan SIP submittals to address
nonattainment area requirements are due. For example, 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 section 107(d)(1)(B) allows up to
two years, or in some cases three years, for such designations to be promulgated.3 This ambiguity
illustrates that, rather than apply all the stated requirements of section 110(a)(2) in a strict literal
sense, the EPA must determine which provisions of section 110(a)(2) are applicable for a
particular infrastructure SIP submittal. Another example of ambiguity within sections 110(a)(1)

For example, CAA section 110(a)(2)(E)(i) provides that States must provide assurances that they have adequate
legal authority under State and local law to carry out the SIP; section 110(a)(2)(C) provides that States must have a
SIP-approved program to address certain sources as required by part C of title I of the CAA; and section
110(a)(2)(G) provides that States must have legal authority to address emergencies as well as contingency plans that
are triggered in the event of such emergencies.
2 See, e.g, 70 FR 25162, 25163-25165 (May 12, 2005), explaining the relationship between the timing requirements
of CAA section 110(a)(2)(D) versus section 110(a)(2)(I).
3 The EPA notes that this ambiguity within CAA section 110(a)(2) is heightened by the fact that various subparts of
part D set specific dates for submittal of certain types of SIP submittals in designated nonattainment areas for
various pollutants. Note, for example, that section 182(a)(1) provides specific dates for submittal of emissions
inventories for the ozone NAAQS. Some of these specific dates are necessarily later than three years after
promulgation of the new or revised NAAQS.
and 110(a)(2) with respect to infrastructure SIPs pertains to whether States must meet all of the
infrastructure SIP requirements in a single SIP submittal and whether the EPA must act upon
such SIP submittal in a single action. Although section 110(a)(1) directs States to submit “a
plan” to meet these requirements, the EPA interprets the CAA to allow States to make multiple
SIP submittals separately addressing infrastructure SIP elements for the same NAAQS. If States
elect to make such multiple SIP submittals to meet the infrastructure SIP requirements, the EPA
can elect to act on such submittals either individually or in a larger combined action.4 Similarly,
the EPA interprets the CAA to allow it to take action on the individual parts of one larger,
comprehensive infrastructure SIP submittal for a given NAAQS without concurrent action on the
entire submittal. For example, the EPA has sometimes elected to act at different times on various
elements and subelements of the same infrastructure SIP submittal.5
Ambiguities within CAA sections 110(a)(1) and 110(a)(2) may also arise with respect to
infrastructure SIP submittal requirements for different NAAQS. Thus, the EPA notes that not
every element of section 110(a)(2) would be relevant, as relevant, or relevant in the same way,
for each new or revised NAAQS. The States’ attendant infrastructure SIP submittals for each
NAAQS therefore could be different. For example, the monitoring requirements that a State
might need to meet in its infrastructure SIP submittal for purposes of 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 be very different for an entirely new NAAQS than for a
minor revision to an existing NAAQS.6

See, e.g., the EPA’s final action approving the structural PSD elements of the New Mexico SIP submitted by the
State separately to meet the requirements of EPA’s 2008 NSR rule for PM2.5 at 78 FR 4339 (January 22, 2013), and
the EPA’s final action on the infrastructure SIP for the 2006 PM2.5 NAAQS at 78 FR 4337 (January 22, 2013).
5 On December 14, 2007, the State of Tennessee made a SIP revision to the EPA demonstrating that the State meets
the requirements of CAA sections 110(a)(1) and 110(a)(2). The EPA proposed action for infrastructure SIP elements
(C) and (J) at 77 FR 3213 (January 23, 2012) and took final action at 77 FR 14976 (March 14, 2012). The EPA took
separate proposed and final actions on all other section 110(a)(2) infrastructure SIP elements of Tennessee’s
December 14, 2007 submittal; see 77 FR 22533 (April 16, 2012) and 77 FR 42997 (July 23, 2012).
6 For example, implementation of the 1997 PM
2.5 NAAQS required the deployment of a system of new monitors to
measure ambient levels of new indicator species for the new NAAQS.
The EPA notes that interpretation of CAA section 110(a)(2) is also necessary when the
EPA reviews other types of SIP submittals required under the CAA. Therefore, as with
infrastructure SIP submittals, the EPA also has to identify and interpret the relevant elements of
section 110(a)(2) that logically apply to these other types of SIP submittals. For example, section
172(c)(7) requires that attainment plan SIP submittals required by part D have to meet the
“applicable requirements” of section 110(a)(2). Thus, for example, attainment plan SIP
submittals must meet the requirements of section 110(a)(2)(A) regarding enforceable emissions
limits and control measures and section 110(a)(2)(E)(i) regarding air agency resources and
authority. By contrast, it is clear that attainment plan SIP submittals required by part D would not
need to meet the portion of section 110(a)(2)(C) that pertains to the air quality prevention of
significant deterioration (PSD) program required in part C of title I of the CAA because PSD
does not apply to a pollutant for which an area is designated nonattainment and thus subject to
part D planning requirements. As this example illustrates, each type of SIP submittal may
implicate some elements of section 110(a)(2) but not others.
Given the potential for ambiguity in some of the statutory language of section 110(a)(1)
and section 110(a)(2), the EPA believes that it is appropriate to interpret the ambiguous portions
of section 110(a)(1) and section 110(a)(2) in the context of acting on a particular SIP submittal.
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 has adopted an approach under which it reviews infrastructure SIP submittals
against the list of elements in section 110(a)(2), but only to the extent each element applies for
that particular NAAQS.
Historically, the EPA has elected to use guidance documents to make recommendations
to States for infrastructure SIPs, in some cases conveying needed interpretations on newly arising
issues and in some cases conveying interpretations that have already been developed and applied

to individual SIP submittals for particular elements.7 The EPA most recently issued guidance for
infrastructure SIPs on September 13, 2013 (“2013 Infrastructure SIP Guidance”).8 The EPA
developed this document to provide States with up-to-date guidance for infrastructure SIPs for
any new or revised NAAQS. Within this guidance, the EPA describes the duty of States to make
infrastructure SIP submittals to meet basic structural SIP requirements within three years of
promulgation of a new or revised NAAQS. The EPA also made recommendations about many
specific subsections of CAA section 110(a)(2) that are relevant in the context of infrastructure
SIP submittals.9 The guidance also discusses the substantively important issues that are germane
to certain subsections of section 110(a)(2). Significantly, the EPA interprets sections 110(a)(1)
and 110(a)(2) such that infrastructure SIP submittals need to address certain issues and need not
address others. Accordingly, the EPA reviews each infrastructure SIP submittal for compliance
with the applicable statutory provisions of section 110(a)(2), as appropriate.
As an example, CAA section 110(a)(2)(E)(ii) is a required element of section 110(a)(2)
for infrastructure SIP submittals. Under this element, a State must meet the substantive
requirements of section 128, which pertain to State boards that approve permits or enforcement
orders and heads of executive agencies with similar powers. Thus, the EPA reviews
infrastructure SIP submittals to ensure that the State’s SIP appropriately addresses the
requirements of section 110(a)(2)(E)(ii) and section 128. The 2013 Infrastructure SIP Guidance
explains the EPA’s interpretation that there may be a variety of ways by which States can

The EPA notes, however, that nothing in the CAA requires the EPA to provide guidance or to promulgate
regulations for infrastructure SIP submittals. The CAA directly applies to States and requires the submittal of
infrastructure SIP submittals, regardless of whether or not the EPA provides guidance or regulations pertaining to
such submittals. The EPA elects to issue such guidance in order to assist States, as appropriate.
8 Memorandum dated September 13, 2013, from Stephen D. Page, Director, Office of Air Quality and Planning
Standards, U.S. EPA, Subject: “Guidance on Infrastructure State Implementation Plan (SIP) Elements under Clean
Air Act Sections 110(a)(1) and 110(a)(2).”
9 The 2013 Infrastructure SIP Guidance did not make recommendations with respect to infrastructure SIP submittals
to address CAA section 110(a)(2)(D)(i)(I). The EPA issued the guidance shortly after the U.S. Supreme Court
agreed to review the D.C. Circuit decision in EME Homer City, 696 F.3d7 (D.C. Cir. 2012) which had interpreted
the requirements of section 110(a)(2)(D)(i)(I). In light of the uncertainty created by ongoing litigation, the EPA
elected not to provide additional guidance on the requirements of section 110(a)(2)(D)(i)(I) at that time. As the
guidance is neither binding nor required by statute, whether the EPA elects to provide guidance on a particular
section has no impact on a State’s CAA obligations.
appropriately address these substantive statutory requirements, depending on the structure of an
individual State’s permitting or enforcement program (e.g., whether permits and enforcement
orders are approved by a multi-member board or by a head of an executive agency). However
they are addressed by the State, the substantive requirements of section 128 are necessarily
included in the EPA’s evaluation of infrastructure SIP submittals because section
110(a)(2)(E)(ii) explicitly requires that the State satisfy the provisions of section 128.
As another example, the EPA’s review of infrastructure SIP submittals with respect to the
PSD program requirements in CAA sections 110(a)(2)(C), 110(a)(2)(D)(i)(II), and 110(a)(2)(J)
focuses on the structural PSD program requirements contained in CAA title I part C and the
EPA’s PSD regulations. Structural PSD program requirements include provisions necessary for
the PSD program to address all regulated sources and regulated NSR pollutants, including
greenhouse gases (GHG). By contrast, structural PSD program requirements do not include
provisions that are not required under the EPA’s regulations at 40 CFR 51.166 but are merely
available as an option for the State, such as the option to provide grandfathering of complete
permit applications with respect to the 2012 PM2.5 NAAQS. Accordingly, the latter optional
provisions are types of provisions the EPA considers irrelevant in the context of an infrastructure
SIP action.
For other CAA section 110(a)(2) elements, however, the EPA’s review of a State’s
infrastructure SIP submittal focuses on assuring that the State’s SIP meets basic structural
requirements. For example, section 110(a)(2)(C) includes, inter alia, the requirement that States
have a program to regulate minor new sources. Thus, the EPA evaluates whether the State has a
SIP-approved minor NSR program and whether the program addresses the pollutants relevant to
that NAAQS. In the context of acting on an infrastructure SIP submittal, however, the EPA does
not think it is necessary to conduct a review of each and every provision of a State’s existing
minor source program (i.e., already in the existing SIP) for compliance with the requirements of
the CAA and the EPA’s regulations that pertain to such programs.

With respect to certain other issues, the EPA does not believe that an action on a State’s
infrastructure SIP submittal is necessarily the appropriate type of action in which to address
possible deficiencies in a State’s existing SIP. These issues include: (i) existing provisions
related to excess emissions from sources during periods of startup, shutdown, or malfunction
(SSM) that may be contrary to the CAA and EPA policies addressing such excess emissions; (ii)
existing provisions related to “director’s variance” or “director’s discretion” that may be contrary
to the CAA because they purport to allow revisions to SIP-approved emissions limits while
limiting public process or not requiring further approval by the EPA; and (iii) existing provisions
for PSD programs that may be inconsistent with current requirements of the EPA’s “Final NSR
Improvement Rule.”10 Thus, the EPA believes it may approve an infrastructure SIP submittal
without scrutinizing the totality of the existing SIP for such potentially deficient provisions and
may approve the submittal even if it is aware of such existing provisions.11 It is important to note
that the EPA’s approval of a State’s infrastructure SIP submittal should not be construed as
explicit or implicit reapproval of any existing potentially deficient provisions that relate to the
three specific issues just described.
The EPA’s approach to reviewing infrastructure SIP submittals is to identify the CAA
requirements that are logically applicable to that submittal. The EPA believes that this approach
to the review of a particular infrastructure SIP submittal is appropriate because it would not be
reasonable to read the general requirements of CAA section 110(a)(1) and the list of elements in
110(a)(2) as requiring review of each and every provision of a State’s existing SIP against all
requirements in the CAA and EPA regulations merely for purposes of assuring that the State in
question has the basic structural elements for a functioning SIP for a new or revised NAAQS.
Because SIPs have grown by accretion over the decades as statutory and regulatory requirements

See 67 FR 80186 (December 31, 2002), as amended by 72 FR 32526 (June 13, 2007).
By contrast, the EPA notes that if a State were to include a new provision in an infrastructure SIP submittal that
contained a legal deficiency, such as a new exemption for excess emissions during SSM events, then the EPA would
need to evaluate that provision for compliance against the rubric of applicable CAA requirements in the context of
the action on the infrastructure SIP.
10
under the CAA have evolved, they may include some outmoded provisions and historical
artifacts. These provisions, while not fully up to date, nevertheless may not pose a significant
problem for the purposes of “implementation, maintenance, and enforcement” of a new or
revised NAAQS when the EPA evaluates adequacy of the infrastructure SIP submittal. The EPA
believes that a better approach is for States and the EPA to focus attention on those elements of
section 110(a)(2) most likely to warrant a specific SIP revision due to the promulgation of a new
or revised NAAQS or other factors.
For example, the 2013 Infrastructure SIP Guidance 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 section 110(a)(2)(D)(i)(II).
Finally, the EPA believes that its approach with respect to infrastructure SIP
requirements is based on a reasonable reading of CAA sections 110(a)(1) and 110(a)(2) because
the CAA provides other avenues and mechanisms to address specific substantive deficiencies in
existing SIPs. These other statutory tools allow the EPA to take appropriately tailored action,
depending upon the nature and severity of the alleged SIP deficiency. Section 110(k)(5)
authorizes the EPA to issue a “SIP call” whenever the Agency determines that a State’s SIP is
substantially inadequate to attain or maintain the NAAQS, to mitigate interstate transport, or to
otherwise comply with the CAA.12 Section 110(k)(6) authorizes the EPA to correct errors in past
actions, such as past approvals of SIP submittals.13 Significantly, the EPA’s determination that

For example, the EPA issued a SIP call to Utah to address specific existing SIP deficiencies related to the
treatment of excess emissions during SSM events. See 76 FR 21639 (April 18, 2011).
13 The EPA has used this authority to correct errors in past actions on SIP submittals related to PSD programs. See
Limitation of Approval of Prevention of Significant Deterioration Provisions Concerning Greenhouse Gas EmittingSources in State Implementation Plans; Final Rule, 75 FR 82536 (December 30, 2010). The EPA has previously
used its authority under CAA section 110(k)(6) to remove numerous other SIP provisions that the Agency
determined it had approved in error. See, e.g., 61 FR 38664 (July 25, 1996) and 62 FR 34641 (June 27, 1997)
(corrections to American Samoa, Arizona, California, Hawaii, and Nevada SIPs); 69 FR 67062 (November 16,
2004) (corrections to California SIP); and 74 FR 57051 (November 3, 2009) (corrections to Arizona and Nevada
SIPs).
an action on a State’s infrastructure SIP submittal is not the appropriate time and place to address
all potential existing SIP deficiencies does not preclude the EPA’s subsequent reliance on
provisions in section 110(a)(2) as part of the basis for action to correct those deficiencies at a
later time. For example, although it may not be appropriate to require a State to eliminate all
existing inappropriate director’s discretion provisions in the course of acting on an infrastructure
SIP submittal, the EPA believes that section 110(a)(2)(A) may be among the statutory bases that
the EPA relies upon in the course of addressing such deficiency in a subsequent action.14
II. Background
A. Statutory Framework
As described in the previous section, CAA section 110(a)(1) requires States to make a
SIP submittal within three years after the promulgation of a new or revised primary NAAQS.
Section 110(a)(2) includes a list of specific elements that each infrastructure SIP submittal must
include. These infrastructure SIP elements required by section 110(a)(2) are as follows:
•

Section 110(a)(2)(A): Emission limits and other control measures.

•

Section 110(a)(2)(B): Ambient air quality monitoring/data system.

•

Section 110(a)(2)(C): Program for enforcement of control measures and regulation of
new and modified stationary sources.

•

Section 110(a)(2)(D)(i): Interstate pollution transport.

•

Section 110(a)(2)(D)(ii): Interstate and international pollution abatement.

•

Section 110(a)(2)(E): Adequate resources and authority, conflict of interest, and oversight
of local and regional government agencies.

•

Section 110(a)(2)(F): Stationary source monitoring and reporting.

•

Section 110(a)(2)(G): Emergency episodes.

See, e.g., the EPA’s disapproval of a SIP submittal from Colorado on the grounds that it would have included a
director’s discretion provision inconsistent with CAA requirements, including section 110(a)(2)(A). See, e.g., 75 FR
42342, 42344 (July 21, 2010) (proposed disapproval of director’s discretion provisions); 76 FR 4540 (January 26,
2011) (final disapproval of such provisions).
•

Section 110(a)(2)(H): SIP revisions.

•

Section 110(a)(2)(J): Consultation with government officials, public notification, PSD,
and visibility protection.

•

Section 110(a)(2)(K): Air quality modeling and submittal of modeling data.

•

Section 110(a)(2)(L): Permitting fees.

•

Section 110(a)(2)(M): Consultation/participation by affected local entities.
Two elements identified in CAA section 110(a)(2) are not governed by the three-year

submittal deadline of section 110(a)(1) and are therefore not addressed in this action. These two
elements are section 110(a)(2)(C), to the extent that it refers to permit programs required under
part D (nonattainment NSR), and section 110(a)(2)(I), pertaining to the nonattainment planning
requirements of part D. As a result, this action does not address infrastructure requirements for
the nonattainment NSR portion of section 110(a)(2)(C) or the entirety of section 110(a)(2)(I).
Additionally, this action does not address the requirements of section 110(a)(2)(D)(i)(I)
pertaining to contributions to nonattainment or interference with maintenance in other States,
referred to as “prongs 1 and 2” and 110(a)(2)(D)(i)(II) pertaining to interference with visibility
protection in other States, referred to as “prong 4”. The EPA will take action on Arizona’s SIP
revision with respect to prongs 1, 2, and 4 of section 110(a)(2)(D)(i) in a separate, future
rulemaking.
B. Regulatory Background
In January 2013, the EPA promulgated a revised primary NAAQS for annual PM2.5,
triggering a requirement for States to submit infrastructure SIPs. The EPA strengthened the
primary annual PM2.5 NAAQS by lowering the level from 15 micrograms per cubic meter
(µg/m3) to 12.0 µg/m3, while maintaining the secondary standard.15
III. State Submittals
A. Infrastructure SIP Submittal
78 FR 3086, (January 15, 2013).

The Arizona Department of Environmental Quality (ADEQ) submitted two SIP revisions
to address the infrastructure SIP requirements in CAA sections 110(a)(1) and 110(a)(2) for the
2012 PM2.5 NAAQS. On December 11, 2015, ADEQ submitted the “Arizona State
Implementation Plan Revision for the 2012 Fine Particulate Matter (PM2.5) National Ambient Air
Quality Standard” (“2015 PM2.5 I-SIP submittal”).16 On February 10, 2022, ADEQ submitted the
“State Implementation Plan Revision: Clean Air Act Section 110(a)(2) for the 2012 Fine
Particulate & 2015 Ozone NAAQS” (“2022 I-SIP supplement”).17 The submittals collectively
address the infrastructure SIP requirements for the 2012 PM2.5 NAAQS as described by this
proposed rule. We refer to them collectively herein as “Arizona’s 2012 PM2.5 I-SIP submittals.”
We find that Arizona’s 2012 PM2.5 I-SIP submittals meet the procedural requirements for
public participation under CAA section 110(a)(2) and 40 CFR 51.102.18 We also find that they
meet the applicable completeness criteria in Appendix V to 40 CFR part 51. We are proposing to
act on these submittals with respect to the 2012 PM2.5 NAAQS except for those portions of the
2012 PM2.5 I-SIP submittals addressing prongs 1, 2, and 4 of the interstate transport requirements
under CAA section 110(a)(2)(D)(i). We are also not taking action on the portions of the 2022 ISIP supplement addressing the 2015 ozone NAAQS in this rulemaking.
B. Revised Rules and Regulations
1. Rules and Regulations Submitted by the State

Letter dated December 11, 2015, from Eric Massey, Director, Air Quality Division, ADEQ, to Jared Blumenfeld,
Regional Administrator, EPA Region IX, Subject: “Arizona Infrastructure State Implementation Plan for the 2012
PM2.5 National Ambient Air Quality Standards.”
17 Letter dated February 10, 2022, from Daniel Czecholinski, Director, Air Quality Division, ADEQ, to Martha
Guzman, Regional Administrator, EPA Region IX, Subject: “Submittal of the Arizona State Implementation Plan
Revision under Clean Air Act Sections 110(a)(2) for the 2012 Fine Particulate and the 2015 Ozone NAAQS.”
18 For the 2015 PM
2.5 I-SIP submittal, ADEQ provided a 30-day public comment period that started on November 9,
2015 and concluded on December 9, 2015, with a public hearing occuring on the same date. No comments were
expressed during the 30-day comment period nor at the public hearing. The details of this public comment period
and hearing can be found in Appendix B of the 2015 PM2.5 I-SIP submittal. Similarly, for the 2022 I-SIP
supplement, ADEQ also provided a 30-day public comment between December 13, 2021, and January 13, 2022,
with a public hearing occuring on January 13, 2022. ADEQ received no verbal or written comments on the 2022 ISIP supplement. The details of this public comment period and hearing can be found in Appendix E to the 2022 ISIP supplement.
In a February 10, 2022 letter transmitting the 2022 I-SIP supplement, ADEQ included
revised rules and regulations for incorporation by reference into the Arizona SIP. These
submittals include: Arizona Administrative Code (AAC) R18-2-220 “Air Pollution Emergency
Episodes,” and the “Procedures for the Prevention of Emergency Episodes;” the Arizona Revised
Statute (ARS) 49–432(C), dealing with public availability of emissions records, Pinal County
Code (PCC) 17.24.010 “Confidentiality of trade secrets, sales data, and proprietary information,”
and Maricopa County Air Pollution Control Regulations, “Regulation VI – Emergency Episodes
Rule 600,” (“Rule 600”).19 The EPA has already proposed to approve the revised ARS 49–432
and PCC 17.24.010 for incorporation into the Arizona SIP in a previous proposed rulemaking.20
AAC R18-2-220 and Rule 600 are included as part of the 2022 I-SIP supplement to satisfy the
requirements of CAA section 110(a)(2)(G) for 2012 PM2.5 NAAQS emergency episodes.
2. What is the Purpose of the Submitted Rule Revisions
The revised AAC R18-2-220 is intended to satisfy outstanding CAA section 110(a)(2)(G)
requirements by adding details of averaging time with alert, warning, emergency, and significant
harm levels for PM2.5. Specifically, the averaging time is set to 24 hours, the alert level is set to
140.5 µg/m3, the warning level is set to 210.5 µg/m3, the emergency level is set to 280.5 µg/m3,
and the significant harm level is set to 350.5 µg/m3. These action levels are set in accordance
with the recommendations in EPA’s 2009 guidance on PM2.5 infrastructure SIPs (“2009 PM2.5 ISIP Guidance”).21 Furthermore, the ADEQ “Procedures for Prevention of Emergency Episodes”
incorporated by reference along with AAC R18-2-220 contains the specific actions and processes
that the State must follow in the event of an air pollution event reaching the various thresholds.
Additionally, Maricopa County Air Quality Department (MCAQD) amended Rule 600 to align

These submitted revised rules and regulations are included in Appendices C and D the 2022 I-SIP supplement.
87 FR 74349, December 5, 2022.
21 “Guidance on SIP Elements Required Under Section 110(a)(1) and (2) for the 2006 24-Hour Fine Particle (PM )
2.5
National Ambient Air Quality Standards (NAAQS),” September 25, 2009.
19
the rule with the episode level criteria and significant harm levels listed in AAC R18-2-220 and
the 2009 PM2.5 I-SIP Guidance.
IV. The EPA’s Evaluation and Proposed Action
We have evaluated Arizona’s 2012 PM2.5 I-SIP submittals, the associated revised rules
and regulations, and the existing provisions of the Arizona SIP for compliance with the
infrastructure SIP requirements of CAA section 110(a)(2) and the applicable regulations in 40
CFR part 51 (“Requirements for Preparation, Adoption, and Submittal of State Implementation
Plans”). The technical support document (TSD) for this rulemaking is available in the docket and
includes our detailed evaluation for these infrastructure SIP elements, rationale for our proposed
actions, and our evaluation of various statutory and regulatory provisions identified and
submitted by Arizona.
A. Proposed Approvals and Partial Approvals
Based on the evaluation presented in this notice and in the accompanying TSD, the EPA
proposes to approve Arizona’s 2012 PM2.5 I-SIP submittals with respect to the 2012 PM2.5
NAAQS for the following CAA requirements. Proposed partial approvals are indicated by the
parenthetical “(in part).”
•

110(a)(2)(A) – Emission limits and other control measures.

•

110(a)(2)(B) – Ambient air quality monitoring/data system.

•

110(a)(2)(C) – Program for enforcement of control measures and regulation of new

stationary sources (in part).
•

110(a)(2)(D)(i)(II) – Interference with PSD, or “prong 3” (in part).

•

110(a)(2)(D)(ii) – Interstate pollution abatement, CAA section 126 (in part).

•

110(a)(2)(D)(ii) – International pollution abatement, CAA section 115.

•

110(a)(2)(E) – Adequate resources and authority, conflict of interest, and oversight of

local governments and regional agencies.
•

110(a)(2)(F) – Stationary source monitoring and reporting.

•

110(a)(2)(G) – Emergency episodes.

•

110(a)(2)(H) – Consultation with government officials.

•

110(a)(2)(J) – Consultation with government officials, public notification, PSD, and

visibility protection (in part).
•

110(a)(2)(K) – Air quality modeling and submission of modeling data.

•

110(a)(2)(L) – Permitting fees.

•

110(a)(2)(M) – Consultation/participation by affected local entities.
Details about the partial approvals noted in this section are provided in Section IV.B of

this notice regarding proposed partial disapprovals. The EPA is taking no action on prongs 1, 2,
and 4 of CAA section 110(a)(2)(D)(i) in this rulemaking.
B. Proposed Partial Disapprovals
The EPA proposes to partially disapprove Arizona’s 2012 PM2.5 I-SIP submittals with
respect to the 2012 PM2.5 NAAQS for the following Clean Air Act requirements.
•

110(a)(2)(C) – Program for enforcement of control measures and regulation of new

stationary sources (in part).
•

110(a)(2)(D)(i)(II) – Interference with PSD, or “prong 3” (in part).

•

110(a)(2)(D)(ii) – Interstate pollution abatement, CAA section 126 (in part).

•

110(a)(2)(J) – Consultation with government officials, public notification, PSD and

visibility protection (in part).
The EPA is proposing to partially disapprove Arizona’s 2012 PM2.5 I-SIP submittals with
respect to the 2012 PM2.5 NAAQS for these CAA requirements due to deficiencies with respect
to PSD permitting of GHG in all permitting jurisdictions in Arizona and with respect to PSD
permitting of all NSR-regulated pollutants in Pima County. The EPA’s proposed disapprovals
apply only to the portions of these requirements that relate to PSD permitting of GHG in all areas
of Arizona and with respect to PSD permitting of all regulated pollutants in Pima County.

Arizona’s SIP does not fully satisfy the statutory and regulatory requirements for PSD
permit programs under CAA title I, part C. Thus, Pima County currently implements the Federal
PSD program in 40 CFR 52.21 for all regulated NSR pollutants pursuant to a delegation
agreement with the EPA, and all Arizona jurisdictions implement the Federal PSD program in 40
CFR 52.21 for GHG because Arizona is prohibited by State law from regulating emissions of
GHG. Although the Arizona SIP remains deficient with respect to PSD permitting for certain
pollutants in certain areas of Arizona as described, these deficiencies are adequately addressed in
both areas by existing Federal implementation plans (FIPs). If finalized, these partial
disapprovals of Arizona’s SIP would not create any new consequences for Arizona, the relevant
county agencies, or the EPA, as Arizona and the county agencies already implement the EPA’s
Federal PSD program at 40 CFR 52.21, pursuant to delegation agreements, for all regulated NSR
pollutants. These partial disapprovals, 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).
C. Incorporation of Rules into Arizona’s State Implementation Plan
As part of our proposed approval of the Arizona infrastructure SIP submittal elements
listed in Section IV.A, we are also proposing to approve two rules and one plan included with the
2022 I-SIP supplement for incorporation into the Arizona State SIP: the revised AAC R18-2-220
“Air Pollution Emergency Episodes,” submitted December 17, 2021, and the “Procedures for the
Prevention of Emergency Episodes" submitted February 10, 2022, with the 2022 I-SIP
supplement.22 Similarly, we are proposing approval of the revised Maricopa County Air
Pollution Control Regulation VI, “Emergency Episodes: Rule 600 Emergency Episodes,”
submitted on December 17, 2021, for incorporation into the State SIP.

ADEQ’s “Procedures for the Prevention of Emegency Episodes” are located in Appendix D to the 2022 I-SIP
supplement.
As a general matter, rules in the SIP must be enforceable (see CAA section 110(a)(2)),
must not interfere with applicable requirements concerning attainment and reasonable further
progress or other CAA requirements (see CAA section 110(l)), and must not modify certain SIP
control requirements in nonattainment areas without ensuring equivalent or greater emissions
reductions (see CAA section 193). We have evaluated the ADEQ and MCAQD revised rules for
compliance with CAA requirements for SIPs set forth in CAA section 110(a)(2) and for
compliance with CAA requirements for SIP revisions in CAA sections 110(l) and 193. In
general, the rules strengthen the SIP for the reasons discussed in Section III.B.2 of this document
and in our TSD. Based upon our analysis, we propose to find that AAC R18-2-220 “Air
Pollution Emergency Episodes,” the “Procedures for the Prevention of Emergency Episodes,”
and Maricopa County Rule 600 meet the requirements of CAA sections 110(a)(2), 110(l), and
193. Therefore, the EPA is proposing to approve the submitted revisions to AAC R18-2-220 “Air
Pollution Emergency Episodes,” the “Procedures for the Prevention of Emergency Episodes,”
and Maricopa County Rule 600 into the Arizona SIP.
D. Deferred Action
The EPA will address the following Clean Air Act Requirements in separate
rulemakings:
•

110(a)(2)(D) (in part): Interstate Pollution Transport
o 110(a)(2)(D)(i)(I) – significant contribution to a nonattainment area (prong 1).
o 110(a)(2)(D)(i)(I) – significant contribution to a maintenance area (prong 2).
o 110(a)(2)(D)(i)(II) – interference with visibility protection in Class I areas (prong
4).
We note that the EPA intends to act on Prongs 1 and 2 of 110(a)(2)(D)(i)(I) in a separate

rulemaking. We intend to act on Prong 4 of 110(a)(2)(D)(i)(II) when we act on Arizona’s plan
addressing Regional Haze requirements for the second planning period.

E. Revising Air Quality Control Regions and Evaluating Emergency Episode Planning
Requirements for PM2.5 in Arizona
Section 51.150 provides criteria for the classification of areas for emergency episode
planning purposes based on measured concentrations of ambient air pollutants, specifically sulfur
oxides, particulate matter, carbon monoxide, nitrogen dioxide, and ozone. The priority thresholds
for classification of air quality control regions (AQCR) are listed at 40 CFR 51.150, and the
specific classifications of AQCR in Arizona are listed at 40 CFR 52.121. Consistent with the
provisions of 40 CFR 51.153, reclassification of an AQCR must rely on the most recent three
years of air quality data. Under 40 CFR 51.151 and 51.152, regions classified under the more
stringent classifications of Priority I, IA, or II are required to have SIP-approved emergency
episode contingency plans, while those classified Priority III are not required to have plans. We
also interpret 40 CFR 51.153 as establishing the means for States to review air quality data and
request a higher or lower classification for any given region and as providing the regulatory basis
for the EPA to reclassify such regions, as appropriate, under the authorities of CAA sections
110(a)(2)(G) and 301(a)(1).
Arizona has six AQCRs: Maricopa Intrastate, which includes Maricopa County; Pima
Intrastate, which includes Pima County; Northern Arizona Intrastate, which includes Apache,
Coconino, Navajo, and Yavapai Counties; Mohave-Yuma Intrastate, which includes Mohave and
Yuma Counties; Central Arizona Intrastate, which includes Gila and Pinal Counties; and
Southeast Arizona Intrastate, which includes Cochise, Graham, Greenlee, and Santa Cruz
Counties.
La Paz County is not listed within any of Arizona’s AQCRs. This county composed the
northern portion of Yuma County prior to its establishment in 1983. The constituent counties of
Arizona’s AQCRs in 40 CFR 52.121 and the delimited boundaries listed in 40 CFR 81.268
predate the incorporation of La Paz County.23 Since that time, neither 40 CFR 52.121 nor 40

45 FR 7545 (February 4, 1980).

CFR 81.268 have been revised to include this county. Therefore, we propose a revision to 40
CFR 52.121 to add La Paz County to the list of constituent counties for the Mohave-Yuma
Intrastate AQCR, and to 40 CFR 81.268, we propose to add La Paz County to the delimited area
of the Mohave-Yuma Intrastate AQCR.24
The EPA’s emergency episode regulations were promulgated before the agency’s
regulation of PM2.5 as a priority pollutant, and do not include concentrations for the priority
classification based on PM2.5 concentrations in 40 CFR 51.150. As explained in our TSD, to
determine the appropriate priority classifications for Arizona’s AQCRs and any related
emergency episode planning requirements, we followed the recommended threshold
concentrations and corresponding priority classifications set forth in the EPA’s 2009 PM2.5 I-SIP
Guidance. We evaluated the three most recent years of complete, quality-assured, and certified
ambient air monitoring data to yield maximum 24-hour PM2.5 concentrations for each county;25
the maximum recorded 24-hour PM2.5 concentrations along with our proposed classifications for
each AQCR are compiled in Table 16 of the TSD accompanying this proposed rule.
The air quality data from 2020–2022 indicate the maximum 24-hour PM2.5 concentrations
monitored in the Pima Intrastate, Northern Arizona Intrastate, Mohave-Yuma Intrastate, Central
Arizona Intrastate, and Southeast Arizona Interstate AQCRs all fall below the Priority II
minimum of 140.5 µg/m3 for PM2.5 set forth in the 2009 PM2.5 I-SIP Guidance. However, the
maximum 24-hour concentration measured in the Maricopa Intrastate was 222.4 µg/m3,
exceeding the minimum Priority I threshold of 210.5 µg/m3. Therefore, the Maricopa Intrastate
AQCR is required to have an emergency episode plan for PM2.5. As mentioned in Section IV.C
of this notice, ADEQ and Maricopa County have both submitted emergency episode plans, and

The EPA has discussed the basis for these proposed amendments to 40 CFR 52.121 and 40 CFR 81.268 with
ADEQ and the State’s concurrence with these revisions will be included as a formal request letter in the docket for
this rulemaking with our notice of final action.
25 EPA AQS Daily Summary Report, AMP435, for 2020–2022 24-Hour PM
2.5 Values for Arizona. Report accessed
July 31, 2023, included in the docket for this rulemaking.
we propose to find that these plans satisfy the requirements of 40 CFR 51.152(a)–(b) and
110(a)(2)(G) of the CAA.
F. 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. Incorporation by Reference
In this rule, the EPA is proposing to include in a final EPA rule regulatory text that
includes incorporation by reference. In accordance with requirements of 1 CFR 51.5, the EPA is
proposing to incorporate by reference the ADEQ and MCAQD rules and plan listed and
discussed in Section IV.C of this preamble. The EPA has made, and will continue to make, these
documents generally available electronically in the docket for this rulemaking at
https://www.regulations.gov.
VI. Statutory and Executive Order Reviews
Under the Clean Air Act, 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 State choices, provided that they meet the criteria of the Clean Air Act.
Accordingly, this proposed action merely proposes to partially approve and partially disapprove
a revision to the Arizona SIP as meeting the requirements of sections 110(a)(1) and 110(a)(2) of
the Clean Air Act for the implementation, maintenance, and enforcement of the 2012 PM2.5
NAAQS as meeting Federal requirements and does not impose additional requirements beyond
those imposed by State law. For that reason, this proposed action:
•

Is not a “significant regulatory action” subject to review by the Office of Management
and Budget under Executive Orders 12866 (58 FR 51735, October 4, 1993), and 14094
(88 FR 21879, January 21, 2011);

•

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

•

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

•

Does not contain any unfunded mandate or significantly or uniquely affect small
governments, as described in the Unfunded Mandates Reform Act of 1995 (Public Law
104-4);

•

Does not have federalism implications as specified in Executive Order 13132 (64 FR
43255, August 10, 1999);

•

Is not subject to Executive Order 13045 (62 FR 19885, April 23, 1997) because it
proposes to approve a State program;

•

Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355,
May 22, 2001); and

•

Is not subject to requirements of Section 12(d) of the National Technology Transfer and
Advancement Act of 1995 (15 U.S.C. 272 note) because application of those
requirements would be inconsistent with the Clean Air Act.
Executive Order 12898 (Federal Actions to Adress Environmental Justice in Minority

Populations and Low-Income Populations, 59 FR 7629, Feb. 16, 1994) directs Federal agencies
to identify and address “disproportionately high and adverse human health or environmental
effects” of their actions on minority populations and low-income populations to the greatest
extent practicable and permitted by law. The EPA defines environmental justice (EJ) as “the fair
treatment and meaningful involvement of all people regardless of race, color, national origin, or
income with respect to the development, implementation, and enforcement of environmental
laws, regulations, and policies.” The EPA further defines the term fair treatment to mean that “no
group of people should bear a disproportionate burden of environmental harms and risks,
including those resulting from negative environmental consequences of industrial, governmental,

and commercial operations or programs and policies.”
The air agency did not evaluate environmental justice considerations as part of its SIP
submittal; the CAA and applicable implementing regulations neither prohibit nor require such an
evaluation. The EPA did not perform an EJ analysis and did not consider EJ in this action. Due
to the nature of the action described in this proposed rulemaking, this action is expected to have a
neutral to positive impact on the air quality of the affected area. Consideration of EJ is not
required as part of this proposed action, and there is no information in the record inconsistent
with the stated goal of E.O. 12898 of achieving environmental justice for people of color, lowincome populations, and Indigenous peoples.
In addition, 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. In
those areas of Indian country, the rule does not have Tribal implications and will not impose
substantial direct costs on Tribal governments or preempt Tribal law as specified by Executive
Order 13175 (65 FR 67249, November 9, 2000).
List of Subjects in 40 CFR Part 52
Environmental protection, Air pollution control, Incorporation by reference,
Intergovernmental relations, Nitrogen Dioxide, Particulate matter, Reporting and recordkeeping
requirements, Volatile organic compounds.

Dated: June 6, 2024.

Martha Guzman Aceves,
Regional Administrator,
Region IX.

[FR Doc. 2024-12781 Filed: 6/12/2024 8:45 am; Publication Date: 6/13/2024]