[Federal Register Volume 89, Number 214 (Tuesday, November 5, 2024)]
[Proposed Rules]
[Pages 87828-87838]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-25575]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52 and 81

[EPA-R09-OAR-2024-0339; FRL-12125-01-R9]


Air Plan Approval; Arizona; Yuma 2015 8-Hour Ozone Nonattainment 
Area; Redesignation Request and Maintenance Plan

AGENCY: Environmental Protection Agency (EPA).

[[Page 87829]]


ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve the State of Arizona's request to redesignate the Yuma 
nonattainment area from nonattainment to attainment for the 8-hour 
national ambient air quality standards (NAAQS or ``standard'') for 
ozone promulgated in 2015 (``2015 ozone NAAQS''). The EPA is also 
proposing to approve the ``SIP Revision: 2015 Ozone NAAQS, Yuma 
Redesignation Request and Maintenance Plan'' (``Yuma Maintenance Plan'' 
or ``Plan'') as a revision to the State Implementation Plan (SIP) for 
the State of Arizona. The Yuma Maintenance Plan includes, among other 
elements, an emissions inventory consistent with attainment, a 
maintenance demonstration, contingency provisions, and a motor vehicle 
emissions budget for the first ten-year maintenance period. With this 
proposed rulemaking, the EPA is beginning the adequacy process for the 
2020, 2030, and 2037 motor vehicle emissions budgets. The EPA is 
proposing these actions because this SIP revision meets the applicable 
Clean Air Act (CAA or ``the Act'') requirements for maintenance plans 
and because the State has met the requirements under the Act for 
redesignation of a nonattainment area to attainment with respect to the 
Yuma 2015 ozone NAAQS nonattainment area (``Yuma area'').

DATES: Written comments must arrive on or before December 5, 2024.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2024-0339 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: Andrew Ledezma, Planning and Analysis 
Branch (AIR-2), Air and Radiation Division, EPA Region IX, 75 Hawthorne 
Street, San Francisco, CA 94105, (415) 972-3985, or by email at 
<a href="/cdn-cgi/l/email-protection#9ad6fffeffe0f7fbb4dbf4fee8ffeddaffeafbb4fdf5ec"><span class="__cf_email__" data-cfemail="08446d6c6d7265692649666c7a6d7f486d7869266f677e">[email protected]</span></a>.

SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us,'' 
and ``our'' refer to the EPA.

Table of Contents

I. Background
    A. The 2015 Ozone National Ambient Air Quality Standards
    B. The Yuma Area and Regulatory Actions
    C. CAA and Regulatory Requirements for Redesignations and 
Maintenance Plans
II. Submissions From the State of Arizona To Redesignate the Yuma 
Area to Attainment for the 2015 Ozone NAAQS
    A. Summary of State Submissions
    B. CAA Procedural Requirements for Adoption and Submission of 
SIP Revisions
III. Evaluation of Arizona's Redesignation Request for the Yuma Area
    A. Evaluation of Whether the Yuma Area Has Attained the 2015 
Ozone NAAQS
    B. The Area Must Have a Fully Approved SIP Meeting the 
Requirements Applicable for the Purposes of Redesignation Under 
Section 110 and Part D of the CAA
    C. The Area Must Show That the Improvement in Air Quality Is Due 
to Permanent and Enforceable Emissions Reductions
    D. The Area Must Have a Fully Approved Maintenance Plan Under 
CAA Section 175A
IV. Proposed Action and Request for Public Comment
V. Statutory and Executive Order Review

I. Background

A. The 2015 Ozone National Ambient Air Quality Standards

    Ground-level ozone pollution is formed from the reaction of 
volatile organic compounds (VOC) and oxides of nitrogen 
(NO<INF>X</INF>) in the presence of sunlight. These two pollutants, 
referred to as ozone precursors, are emitted by many types of sources, 
including on- and nonroad motor vehicles and engines, power plants and 
industrial facilities, and smaller area sources such as lawn and garden 
equipment and paints.
    Scientific evidence indicates that adverse public health effects 
occur following exposure to ozone, particularly in children and adults 
with lung disease. Breathing air containing ozone can reduce lung 
function and inflame airways, which can increase respiratory symptoms 
and aggravate asthma or other lung diseases.\1\
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    \1\ ``Fact Sheet--2008 Final Revisions to the National Ambient 
Air Quality Standards for Ozone,'' dated March 2008.
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    Under section 109 of the Act, the EPA promulgates NAAQS for 
pervasive air pollutants, such as ozone. The NAAQS are concentration 
levels the EPA has determined to be requisite to protect public health 
and welfare. On February 8, 1979, the EPA established primary and 
secondary NAAQS for ozone at 0.12 parts per million (ppm) averaged over 
a 1-hour period.\2\ On July 18, 1997, the EPA revised the primary and 
secondary standards for ozone to set the acceptable level of ozone in 
the ambient air at 0.080 ppm averaged over an 8-hour period (``1997 
ozone NAAQS'').\3\
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    \2\ See 44 FR 8202 (February 8, 1979).
    \3\ See 62 FR 38856. On April 30, 2004, the EPA designated and 
classified areas of the country with respect to the 1997 ozone 
NAAQS. See 69 FR 23858.
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    In 2008, the EPA lowered the 8-hour ozone NAAQS to 0.075 ppm 
(``2008 ozone NAAQS'') to revise the 1997 ozone NAAQS.\4\ Then, in 
2015, the EPA lowered the primary and secondary 8-hour ozone NAAQS to 
0.070 ppm (``2015 ozone NAAQS'' or ``standard'' \5\).\6\ Most recently, 
in December 2020, the EPA finalized review of the ozone NAAQS, 
retaining the form and level of the standards.\7\ As a result, no new 
ozone area designations were triggered under the CAA, and therefore, no 
new nonattainment area requirements will apply. This action pertains to 
only the 2015 ozone NAAQS.
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    \4\ 73 FR 16436 (March 27, 2008).
    \5\ Since the primary and secondary 2015 ozone standards are the 
same, we hereafter refer to them herein using the singular ``2015 
ozone NAAQS'' or ``standard.''
    \6\ 80 FR 65292 (October 26, 2015).
    \7\ 85 FR 87256 (December 31, 2020). This proposed action 
relates to the requirements for the 2015 ozone NAAQS. Information 
regarding the December 31, 2020 retention of the prior 2015 ozone 
NAAQS is provided for reference only.
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B. The Yuma Area and Regulatory Actions

    Following promulgation of a new or revised NAAQS, the EPA is 
required by the CAA to promulgate designations for areas throughout the 
U.S. in accordance with section 107(a)(1) of the CAA. Effective August 
3, 2018, the EPA

[[Page 87830]]

established the initial air quality designations for most areas in the 
United States for the 2015 ozone NAAQS.\8\ The EPA designated the Yuma 
area as ``Marginal'' nonattainment for the 2015 ozone NAAQS based on 
monitoring data from 2014-2016. Areas classified as Marginal must 
attain the NAAQS within three years of the effective date of the 
nonattainment designation.\9\ The Yuma area covers 52 square miles in 
the Sonoran Desert region of southwestern Arizona and is adjacent to 
California and the international border with Mexico.\10\ In response to 
the designation and classification of the Yuma area as a Marginal area, 
Arizona submitted to the EPA revisions to its nonattainment new source 
review (NNSR) program. The EPA approved the revisions and determined 
that the NNSR program meets the applicable NNSR program requirements 
for areas classified as Marginal nonattainment for the 2015 ozone 
NAAQS.\11\ Arizona also submitted a plan titled ``Marginal Ozone Plan 
for the Yuma Nonattainment Area'' and a technical supplement which 
address the emissions inventory requirement in CAA section 182(a)(1) 
and the emissions statement requirement in CAA section 182(a)(3). The 
EPA approved the emissions inventory for the Yuma area on April 5, 
2022,\12\ and the emissions statement on July 29, 2022.\13\
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    \8\ 83 FR 25776 (June 4, 2018).
    \9\ CAA section 181(a)(1), 40 CFR 51.1102 and 51.1103(a).
    \10\ The Yuma nonattainment area is bounded on the north and 
west by the Arizona state line, bounded on the south by the line of 
latitude at 32[deg]39'20'' N, bounded on the east by the line of 
longitude 114[deg]33'50'' W, and excluding the section 10, 11, and 
12 of township T9S, R23W and any portion in Indian Country. See 40 
CFR 81.303.
    \11\ 89 FR 22963 (April 3, 2024).
    \12\ 87 FR 19629 (April 5, 2022).
    \13\ 87 FR 45657 (July 29, 2022).
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    On October 7, 2022, the EPA determined that the Yuma area attained 
the 2015 ozone NAAQS by August 3, 2021, the attainment deadline 
specified by the Act, with a design value of 0.068 ppm.\14\ The EPA 
relied on 2018-2020 quality-assured, certified ambient ozone data in 
making the determination that the Yuma area had attained the NAAQS by 
the applicable date.
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    \14\ 87 FR 60897 (October 7, 2022). The design value for the 
2015 ozone NAAQS is the fourth-highest daily maximum 8-hour average 
concentration of ozone averaged over a three-year period. 40 CFR 
part 50, appendix U.
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C. CAA and Regulatory Requirements for Redesignations and Maintenance 
Plans

    The CAA establishes the criteria that must be met for the EPA to 
redesignate a nonattainment area to attainment for a given NAAQS. 
Specifically, section 107(d)(3)(E) sets forth the following criteria: 
(1) the EPA must determine that the area has attained the applicable 
NAAQS; (2) the EPA must have a fully approved SIP for the area under 
CAA section 110(k); (3) the EPA must determine that the improvement in 
air quality is due to permanent and enforceable reductions in 
emissions; (4) the EPA must have fully approved a maintenance plan for 
the area as meeting the requirements of CAA section 175A; and, (5) the 
State must have met all requirements applicable to the area under 
section 110 and title I, part D (``part D'') of the CAA. Section 110 
identifies a comprehensive list of elements that must be included in 
SIPs, and part D establishes the SIP requirements for nonattainment 
areas. Part D is divided into six subparts. The generally applicable 
SIP requirements for nonattainment areas are found in subpart 1 of part 
D, and the ozone-specific SIP requirements are found in subpart 2 of 
part D. The EPA provided guidance on redesignations in a document 
titled ``State Implementation Plans; General Preamble for the 
Implementation of title I of the Clean Air Act Amendments of 1990,'' 
published in the Federal Register on April 16, 1992,\15\ and 
supplemented on April 28, 1992 \16\ (collectively referred to herein as 
the ``General Preamble''). The EPA issued additional guidance in two 
memoranda: a September 4, 1992 memorandum from John Calcagni, titled 
``Procedures for Processing Requests to Redesignate Areas to 
Attainment'' (``Calcagni memo''); \17\ and a 1995 memorandum from Mary 
D. Nichols, titled ``Part D New Source Review (part D NSR) Requirements 
for Areas Requesting Redesignation to Attainment'' (``Nichols 
memo'').\18\
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    \15\ 57 FR 13498 (April 16, 1992).
    \16\ 57 FR 18070 (April 28, 1992).
    \17\ Memorandum dated September 4, 1992, from John Calcagni, Air 
Quality Management Division, U.S. EPA, to Regional Air Directors, 
Regions I-X, Subject: ``Procedures for Processing Requests to 
Redesignate Areas to Attainment,'' available at https://www.epa.gov/sites/default/files/2016-03/documents/calcagni_memo_-_procedures_for_processing_requests_to_redesignate_areas_to_attainment_090492.pdf.
    \18\ Memorandum dated October 14, 1994, from Mary D. Nichols, 
Assistant Administrator, U.S. EPA, to EPA Regional Air Directors, 
Region I-X, Subject: ``Part D New Source Review (part D NSR) 
Requirements for Areas Requesting Redesignation to Attainment,'' 
available at https://www.epa.gov/sites/default/files/2015-07/documents/101494m.pdf.
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    The EPA's approval of a State's maintenance plan is one of the CAA 
prerequisites for redesignation of a nonattainment area to attainment. 
Section 175A of the CAA provides the general framework for a State's 
maintenance plans. A State's initial 10-year maintenance plan must 
provide for maintenance of the NAAQS for at least 10 years after 
redesignation and include any additional control measures necessary to 
ensure such maintenance. In addition, maintenance plans must contain 
contingency provisions necessary to assure the prompt correction of a 
violation of the NAAQS during the maintenance period. At a minimum, 
these contingency provisions must include a requirement that a State 
will implement all control measures contained in the nonattainment SIP 
prior to redesignation. Because a State's maintenance plan submittals 
are SIP revisions, the EPA is obligated under CAA section 110(k) to 
approve them or disapprove them depending upon whether they meet the 
applicable CAA requirements for such plans outlined above.
    For the reasons described in section III of this proposal, the EPA 
is proposing to approve the Yuma Maintenance Plan and approve Arizona's 
request for redesignation of the Yuma area to attainment for the 2015 
ozone NAAQS. The EPA's proposed approvals are based on our conclusion 
that Arizona has satisfied all the criteria under CAA section 
107(d)(3)(E).

II. Submissions From the State of Arizona To Redesignate the Yuma Area 
to Attainment for the 2015 Ozone NAAQS

A. Summary of State Submissions

    On December 27, 2023, the Arizona Department of Environmental 
Quality (ADEQ) submitted to the EPA its redesignation request and the 
Yuma Maintenance Plan as a revision to the Arizona SIP.\19\ This 
document addresses all of the CAA section 107(d)(3)(E) requirements for 
redesignating a nonattainment area to attainment for the NAAQS and 
includes the required maintenance plan elements. The Yuma Maintenance 
Plan is organized into eight chapters and two appendices. Appendix A of 
the Plan provides technical support for the emissions inventory, and 
appendix B of the Plan contains the procedural requirements and 
authority to implement the Yuma Maintenance Plan.
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    \19\ Letter dated December 27, 2023, from Hether Krause, Deputy 
Assistant Director, ADEQ, to Martha Guzman, Regional Administrator, 
EPA Region IX.

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[[Page 87831]]

B. CAA Procedural Requirements for Adoption and Submission of SIP 
Revisions

    CAA sections 110(a) and 110(l) require a State to provide 
reasonable public notice and opportunity for public hearing prior to 
the adoption and submission of a SIP revision to the EPA. To meet this 
procedural requirement, a State must include evidence that it provided 
adequate public notice and an opportunity for a public hearing, 
consistent with the EPA's implementing regulations in 40 CFR 51.102.
    ADEQ's December 27, 2023 SIP submittal includes documentation of 
the public process conducted by ADEQ in its adoption the Yuma 
Maintenance Plan.\20\ On November 15, 2023, ADEQ released a draft 
version of the plan for public review and published a notice of public 
meeting to be held on December 15, 2023, to consider the adoption of 
the Yuma Maintenance Plan. ADEQ adopted the Yuma Maintenance Plan on 
December 15, 2023, following a public hearing, as documented in the 
public hearing presiding officer certification \21\ and public hearing 
transcript.\22\ Based on the documentation in the December 27, 2023 SIP 
submittal, ADEQ has satisfied the applicable statutory and regulatory 
requirements for reasonable public notice and hearing prior to adoption 
and submission of the Plan. Therefore, the submission of the Yuma 
Maintenance Plan meets the procedural requirements for public notice 
and hearing in CAA sections 110(a) and 110(l) and in 40 CFR 51.102.
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    \20\ ADEQ submitted a signed version of its ``Notice of Public 
Hearing'' published online, and in print in The Arizona Republic on 
November 14 and 15, 2023 and in the Yuma Sun on November 14, 2023.
    \21\ ADEQ submitted a signed version of the ``Public hearing 
presiding officer certification,'' which certifies that ADEQ 
conducted public hearing on December 15, 2023.
    \22\ ADEQ submitted a written transcript of the public hearing 
conducted on December 15, 2023, in which the Yuma Maintenance Plan 
was adopted.
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    On June 23, 2024, the Yuma Maintenance Plan became complete by 
operation of law pursuant to CAA section 110(k)(1)(B).\23\
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    \23\ For more information regarding the completeness criteria as 
per CAA section 110(k)(1)(A) and 40 CFR part 51, appendix V, see the 
completeness checklist in the Yuma Maintenance Plan, v-viii.
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III. Evaluation of Arizona's Redesignation Request for the Yuma Area

A. Evaluation of Whether the Yuma Area Has Attained the 2015 Ozone 
NAAQS

1. Statutory and Regulatory Requirements
    Pursuant to section 107(d)(3)(E)(i) of the CAA, for a nonattainment 
area to be redesignated to attainment, the EPA must determine that the 
area has attained the relevant NAAQS. The EPA interprets this 
requirement to mean that the area must have an attaining design value 
based on the most recently available and quality-assured air quality 
monitoring data, collected in accordance with the requirements of 40 
CFR part 58.\24\ These requirements include quality assurance 
procedures for monitor operation and data handling, siting parameters 
for instruments or instrument probes, and minimum ambient air quality 
monitoring network requirements.\25\ State, local, or Tribal agencies 
that operate air monitoring sites in accordance with 40 CFR part 58 
must enter the ambient air quality data from these sites in the EPA Air 
Quality System (AQS) database.\26\ These monitoring agencies certify 
annually that these data are accurate to the best of their knowledge, 
taking into consideration the quality assurance findings.\27\ 
Accordingly, the EPA relies primarily on AQS data when determining the 
attainment status of an area.
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    \24\ 57 FR 13948 at 13563 (April 12, 1992).
    \25\ 40 CFR 58.2(a).
    \26\ 40 CFR 58.16. AQS is the EPA's national repository of 
ambient air quality data.
    \27\ 40 CFR 58.15(a).
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    In accordance with 40 CFR part 50, appendix U, the EPA's finding of 
attainment of the 2015 ozone NAAQS must be based upon complete, 
certified data gathered at monitoring sites in the nonattainment area 
in accordance with 40 CFR part 58 and entered into AQS.\28\ Under 40 
CFR 50.19 and in accordance with part 50, appendix U, an area meets the 
2015 ozone NAAQS when the design value at each eligible monitoring site 
within the area is less than or equal to 0.070 ppm, based on the 
calculations set forth in 40 CFR part 50, appendix U.\29\
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    \28\ 40 CFR part 50, appendix U, section 3.
    \29\ The 2015 ozone NAAQS design value is the annual fourth-
highest daily maximum 8-hour average ozone concentration, averaged 
over three years.
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    To have a valid design value showing attainment of the ozone 
standard at a given monitoring site, the ambient air quality data must 
meet data completeness or substitution requirements for each year under 
consideration. The completeness requirements are met when at least 90 
percent of the days in the ozone season are complete,\30\ on average, 
for the three-year period, with a minimum of at least 75 percent of the 
complete days within the ozone monitoring period in any one year.\31\ 
When computing whether the minimum data completeness requirements have 
been met, meteorological or ambient data may be sufficient to 
demonstrate that meteorological conditions on missing days were not 
conducive to concentrations above the level of the 2015 ozone NAAQS. 
Missing days assumed less than the level of the 2015 ozone NAAQS are 
counted for the purpose of meeting the minimum data completeness 
requirements, subject to the approval of the Regional 
Administrator.\32\
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    \30\ Ozone season refers to seasons of the year that are 
conducive to ozone formation, identified on a state-by-state basis 
per 40 CFR part 58, appendix D 4.1(i), table D-3. The Yuma 
Maintenance Plan identifies their high ozone season as April to 
September. Yuma Maintenance Plan, 9.
    \31\ 40 CFR part 50, appendix U, section 4.b.
    \32\ 40 CFR part 50, appendix U, section 4.c.
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2. Monitoring Network Review, Quality Assurance, and Data Completeness
    ADEQ is the governmental agency with the authority and 
responsibilities under the State's laws for collecting ambient air 
quality data in the Yuma area. As a result, ADEQ submits annual 
monitoring network plans to the EPA.\33\ These plans document the 
status of ADEQ's air monitoring network, as required under 40 CFR 
58.10. The EPA reviews these annual network plans for compliance with 
the specific requirements in 40 CFR part 58. With respect to ozone, we 
have found that the annual network plans submitted by ADEQ met these 
requirements under 40 CFR part 58, including the minimum monitoring 
requirements.\34\ Yuma Supersite (AQS ID No. 04-027-8011) is the only 
ozone monitor in the Yuma area.
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    \33\ We have included in the docket for this rulemaking, EPA 
reviews of ADEQ annual network plans and the correspondence 
transmitting this review, e.g., from Dena Vallano, Manager, 
Monitoring and Analysis Section, EPA Region IX, to Daniel 
Czecholinski, Air Division Director, ADEQ.
    \34\ See e.g., ``Arizona Air Monitoring Network Plan for the 
Year 2023,'' Tables 2.1-10 and 2.1-11, ``Minimum Monitoring 
Requirements for O3.''
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    In accordance with 40 CFR 58.15, ADEQ certifies annually that the 
previous years' ambient concentration and quality assurance data are 
completely submitted to AQS and that

[[Page 87832]]

the ambient concentration data are accurate, taking into consideration 
the quality assurance findings.\35\ Along with the certification 
letters, ADEQ submits a summary of the precision and accuracy data for 
all ambient air quality data.\36\ The EPA's evaluations of the relevant 
quality assurance data are reflected in the associated AQS design value 
reports.\37\ These reports include a certification evaluation and 
concurrence (``Cert&Eval'') flag indicating the overall quality of the 
corresponding monitoring data. Over the period of 2021-2023, the 
associated Cert&Eval flag in the design value report was ``Y'' for the 
monitoring site in the Yuma area,\38\ meaning that ``[t]he certifying 
agency has submitted a certification letter, and EPA has no unresolved 
reservations about data quality (after reviewing the letter, the 
attached summary reports, the amount of quality assurance data 
submitted to AQS, the quality statistics, and the highest reported 
concentrations).'' \39\
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    \35\ We have included in our docket ADEQ's annual data 
certifications for 2020-2022. Annual data certification requirements 
can be found at 40 CFR 58.15.
    \36\ 40 CFR 58.15(c).
    \37\ AQS, Design Value Report (AMP480), dated February 21, 2024.
    \38\ In 2021, the one-point quality control check requirement 
was not met. ADEQ did not complete the required number of checks 
throughout the year. However, according to 40 CFR part 58, appendix 
A, section 1.2.3, failure to conduct or pass a required check or 
procedure, or a series of required checks or procedures, does not by 
itself invalidate data for regulatory decision making.
    \39\ AQS, Design Value Report (AMP480), dated February 21, 2024.
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    The Yuma area Design Value Report also included a validity 
indicator (``Y'') that reflects whether the design value is valid 
(i.e., calculated using data that meet the applicable completeness 
criteria). For the purposes of this proposal, we reviewed the data for 
the 2021-2023 period for completeness and determined that the ozone 
data collected by ADEQ met the completeness criterion at the ozone 
monitoring site in the Yuma area.\40\
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    \40\ Id.
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    Finally, the EPA conducts regular technical system audits (TSAs) 
where we review and inspect State and local ambient air monitoring 
programs to assess compliance with applicable regulations concerning 
the collection, analysis, validation, and reporting of ambient air 
quality data. For the purposes of this proposal, we reviewed the 
findings from the EPA's 2021 TSA of ADEQ's ambient air monitoring 
program.\41\ In Finding 4 of the 2021 TSA, the EPA noted that ADEQ did 
not report all valid measurement quality checks to AQS as required by 
the CFR. ADEQ conducted nightly zero/precision/span checks on its ozone 
analyzers with certified transfer standards but did not report these to 
AQS. In the past, the rationale for not reporting these checks was that 
the stability was not tracked or was questionable given the limited 
time for the zero/precision/span to occur, (i.e., 11:45 p.m.-12:15 
a.m.). To address this finding, as of October 2023, ADEQ has begun to 
submit nightly ozone precision checks to AQS. The EPA did not recommend 
invalidating any data from the monitoring site in the Yuma area based 
on this TSA.
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    \41\ Technical Systems Audit of the Ambient Air Monitoring 
Program: Arizona Department of Environmental Quality, February 8-12, 
2021; Final Report dated April 2022 (``2021 TSA''). The 2021 TSA is 
attached to its transmittal letter dated April 7, 2022, from 
Elizabeth J. Adams, EPA Region IX, to Bradley Busby, Manager, ADEQ.
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    In summary, based on the EPA's reviews of the relevant monitoring 
network plans, certifications, quality assurance data, and the 2021 
TSA, we propose to find that the ozone data collected in the Yuma area 
are suitable for determining whether the area has attained the 2015 8-
hour ozone NAAQS based on the most recent certified data available in 
AQS.
3. Evaluation of Attainment
    Table 1 shows the calculated 2015 ozone design values at the Yuma 
Supersite monitor (AQS ID No. 04-027-8011). The data show that the 
monitor in the Yuma area met the 2015 ozone NAAQS in the 2020-2022 
period. In addition, preliminary data for 2024 shows that the Yuma 
Supersite monitor is attaining the 2015 ozone NAAQS.\42\
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    \42\ See ``AQS Quicklook Report,'' dated October 1, 2024, 
available in the docket for this proposed rule. At the Yuma 
Supersite, available data for 2024 on includes the first and second 
quarter of the year (January through June). Based on that first and 
second quarter, the fourth-highest 8-hour ozone concentration so far 
in 2014 is 0.068 ppm.

  Table 1--Yuma Supersite Monitor (AQS ID No. 04-027-8011) Design Value
                 for the 2015 Ozone NAAQS From 2008-2022
                      [Parts per million (ppm)] \a\
------------------------------------------------------------------------
                          Year                             Design value
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2010....................................................           0.073
2011....................................................           0.073
2012....................................................           0.077
2013....................................................           0.076
2014....................................................           0.077
2015....................................................           0.076
2016....................................................           0.074
2017....................................................           0.072
2018....................................................           0.071
2019....................................................           0.071
2020....................................................           0.068
2021....................................................           0.067
2022....................................................           0.068
2023....................................................           0.070
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\a\ Source: AQS, Design Value Report, dated May 1, 2024.

    Consequently, based upon three complete, quality assured and 
certified data from 2021-2023, the EPA proposes to determine that the 
Yuma area has attained and continues to attain the 2015 ozone NAAQS.

B. The Area Must Have a Fully Approved SIP Meeting the Requirements 
Applicable for the Purposes of Redesignation Under Section 110 and Part 
D of the CAA

    Sections 107(d)(3)(E)(ii) and (v) of the CAA require the EPA to 
determine that the area has a fully approved applicable SIP under CAA 
section 110(k) that meets all applicable requirements under section 110 
and part D for the purposes of redesignation. We interpret the 
references to the ``applicable implementation plan'' and ``applicable 
requirements'' in section 107(d)(3)(E)(ii) and in 107(d)(3)(E)(v), 
respectively, to mean that a SIP must be fully approved only with 
respect to requirements that are applicable for purposes of 
redesignation. The CAA section 110 and part D requirements that are 
linked to a particular nonattainment area's designation and 
classification (except those directly related to attainment) are the 
relevant measures to evaluate in reviewing a redesignation request. 
Requirements that apply regardless of the designation of an area of a 
State are not applicable requirements for the purpose of redesignation, 
and the State will remain subject to these requirements after the 
nonattainment area is redesignated to attainment.\43\ The EPA may rely 
on prior SIP approvals in

[[Page 87833]]

approving a redesignation request \44\ as well as any additional 
measure or element it may approve in conjunction with a redesignation 
action.\45\
---------------------------------------------------------------------------

    \43\ See the Calcagni memo; memorandum dated September 17, 1993, 
from Michael Shapiro, Acting Assistant Administrator for Air and 
Radiation, Subject: ``State Implementation Plan (SIP) Requirements 
for Areas Submitting Requests for Redesignation to Attainment of the 
Ozone and Carbon Monoxide (CO) National Ambient Air Quality 
Standards (NAAQS) on or after November 15, 1992,''; 60 FR 12459, 
12465-66 (March 7, 1995) (redesignation of Detroit-Ann Arbor, 
Michigan); 68 FR 25418, 25424-25427 (May 12, 2003) (redesignation of 
St. Louis, Missouri); and Sierra Club v. EPA, 375 F.3d 537, 541 (7th 
Cir. 2004) (upholding EPA's redesignation rulemaking applying this 
interpretation).
    \44\ Calcagni memo, 3; Wall v. EPA, 265 F.3d 426, 438 (6th Cir. 
2001).
    \45\ Calcangi memo, 3; 68 FR 25418, 25426 (May 12, 2003).
---------------------------------------------------------------------------

1. State Implementation Plan Requirements Under Section 110
    The general SIP elements and requirements set forth in CAA section 
110(a)(2) include, but are not limited to, the following: (1) submittal 
of a SIP that has been adopted by the State after reasonable public 
notice and hearing; (2) provisions for establishment and operation of 
appropriate procedures needed to monitor ambient air quality; (3) 
implementation of a source permitting program; (4) provisions for the 
implementation of part C requirements for prevention of significant 
deterioration (PSD); (5) provisions for the implementation of part D 
requirements for nonattainment new source review permit programs; (6) 
provisions for air pollution modeling; and (7) provisions for public 
and local agency participation in planning and emission control rule 
development.
    On numerous occasions, Arizona has submitted, and the EPA has 
approved provisions addressing the basic CAA section 110 provisions. 
The Arizona SIP contains enforceable emissions limitations, requires 
monitoring, compiling, and analyzing of ambient air quality data; 
requires preconstruction review of new or modified stationary sources; 
provides for adequate funding, staff, and associated resources 
necessary to implement its requirements; and provides the necessary 
assurances that the State maintains responsibility for ensuring that 
the CAA requirements are satisfied in the event that local or regional 
agencies are unable to meet their CAA obligations. Most recently, on 
September 4, 2024, the EPA finalized a partial approval and partial 
disapproval of SIP revisions submitted by the State of Arizona with 
respect to the requirements of CAA section 110(a)(2) for the 2015 ozone 
NAAQS.\46\ Specifically, the EPA partially disapproved the SIP 
revisions for CAA requirements in sections 110(a)(2)(C) (program for 
enforcement of control measures and regulation of new stationary 
sources), 110(a)(2)(D)(i)(II) (interference with maintenance of the 
NAAQS in any other State, or ``prong 3''), 110(a)(2)(D)(ii) (interstate 
pollution abatement, CAA section 126), and 110(a)(2)(J) (PSD and 
visibility protection). The deficiencies are adequately addressed by 
existing Federal implementation plans.
---------------------------------------------------------------------------

    \46\ 89 FR 71830 (September 4, 2024).
---------------------------------------------------------------------------

    In conclusion, we find that there are no outstanding or disapproved 
applicable SIP submittals that prevent redesignation of the Yuma area 
for the 2015 ozone NAAQS. Therefore, we propose to conclude that the 
State has met all SIP requirements for the Yuma area that are 
applicable for purposes of redesignation under section 110 of the CAA.
2. State Implementation Plan Requirements Under Part D
    Part D of the CAA establishes the plan requirements for 
nonattainment areas. Section 172(c) in subpart 1 of part D sets forth 
the basic requirements of air quality plans for States with 
nonattainment areas that are required to submit plans on a schedule 
pursuant to CAA section 172(b). Subpart 2 of part D, which includes 
section 182 of the CAA, establishes specific requirements for ozone 
nonattainment areas depending on the areas' nonattainment 
classifications. The Yuma area is classified as Marginal nonattainment 
for the 2015 ozone NAAQS, and thus, the area is subject to the subpart 
1 requirements contained in CAA sections 172(c) and 176, as well as CAA 
section 182(c). A thorough discussion of the requirements contained in 
sections 172(c) and 182(c) can be found in the ``General Preamble for 
Implementation of Title I of the Clean Air Act Amendments of 1990.'' 
\47\
---------------------------------------------------------------------------

    \47\ 57 FR 13498 (April 16, 1992).
---------------------------------------------------------------------------

    CAA requirements for ozone nonattainment areas are cumulative in 
that ``Extreme'' areas must also meet the applicable requirements for 
the four lesser classifications: Marginal, ``Moderate,'' ``Serious,'' 
and ``Severe.'' Because the Yuma area was classified as Marginal 
nonattainment for ozone, the area is only required to meet the 
applicable Marginal ozone requirements.\48\ Since its classification as 
a Marginal nonattainment area, the State has adopted and the EPA has 
approved into the Arizona SIP the following Marginal area requirements 
for the Yuma area with respect to the 2015 ozone NAAQS: emissions 
inventories,\49\ emissions statements,\50\ and nonattainment new source 
review programs.\51\
---------------------------------------------------------------------------

    \48\ The requirements can be found in CAA section 182(a).
    \49\ 87 FR 19629 (April 5, 2022).
    \50\ 87 FR 45657 (July 29, 2022).
    \51\ 89 FR 22963 (April 3, 2024).
---------------------------------------------------------------------------

    In conclusion, we find that the Yuma area has a fully approved SIP 
under CAA section 110(k) that satisfies the criterion for redesignation 
under sections 107(d)(3)(E)(ii) and (v) of the CAA.

C. The Area Must Show That the Improvement in Air Quality Is Due to 
Permanent and Enforceable Emissions Reductions

    To approve a redesignation to attainment, section 107(d)(3)(E)(iii) 
of the CAA requires the EPA to determine that the improvement in air 
quality is due to emissions reductions that are permanent and 
enforceable, and that the improvement results from the implementation 
of the applicable SIP, applicable Federal air pollution control 
regulations, and other permanent and enforceable regulations. Under 
this criterion, a State must be able to reasonably attribute the 
improvement in air quality to permanent and enforceable emissions 
reductions. Attainment resulting from temporary reductions in emissions 
(e.g., reduced production or shutdown due to temporary adverse economic 
conditions) or unusually favorable meteorology would not qualify as an 
air quality improvement due to permanent and enforceable emissions 
reductions.\52\
---------------------------------------------------------------------------

    \52\ Calcagni memo, 4.
---------------------------------------------------------------------------

    ADEQ found that the Yuma area has demonstrated that the observed 
air quality improvements with respect to the 2015 ozone NAAQS are due 
to enforceable emissions reductions through the implementation of 
Federal vehicle standards, engine standards, and rules for boilers, 
reciprocating internal combustion engines, and electrical utility 
generation units. ADEQ found that, within the Yuma area, Federal 
regulations have been the primary measures contributing to permanent 
and enforceable emissions reductions, leading to attainment of the 
NAAQS.\53\
---------------------------------------------------------------------------

    \53\ Yuma Maintenance Plan, 28-32.
---------------------------------------------------------------------------

    The Federal motor vehicle program and Federal fuel standards for 
sulfur content in diesel have contributed to attainment of the 2015 
ozone NAAQS in the Yuma area by reducing VOC and NO<INF>X</INF>.\54\ 
Federal tier 2 and 3 motor vehicle standards implemented from 2004 to 
2014 helped to reduce on-road mobile source VOC and NO<INF>X</INF> 
emissions in the Yuma area through increasingly stringent emissions 
standards. Federal sulfur content standards for diesel fuel were 
implemented in conjunction with the Federal motor vehicle program 
standards. Sulfur occurs naturally in gasoline and interferes with the 
operation of catalytic converters on vehicles, which results in higher 
NO<INF>X</INF>

[[Page 87834]]

emissions. Lower sulfur content fuel has reduced sulfur dioxide 
(SO<INF>2</INF>) emissions and allowed pollution control equipment to 
operate more effectively to reduce emissions of other pollutants as 
well.
---------------------------------------------------------------------------

    \54\ Yuma Maintenance Plan, 28-31.
---------------------------------------------------------------------------

    Federal nonroad and stationary standards also contributed to 
attainment of the 2015 ozone NAAQS. Nonroad spark-ignition and 
recreational engine standards implemented between 2003 and 2020 have 
contributed to a 72 percent reduction in VOCs and an 80 percent 
reduction in NO<INF>X</INF>.\55\ The boiler and reciprocating internal 
combustion engines national emissions standards for hazardous air 
pollutants (NESHAPs), as well as the utility mercury and air toxics 
standards (MATS) and new source performance standards (NSPS) rules for 
electricity generating units also have contributed to VOC and 
NO<INF>X</INF> reductions in the Yuma area.\56\ Taken together, these 
Federal programs contributed to VOC and NO<INF>X</INF> emissions 
reductions in the Yuma area.
---------------------------------------------------------------------------

    \55\ Id.
    \56\ Id.
---------------------------------------------------------------------------

    With respect to the connection between the emissions reductions and 
the improvement in air quality, we also conclude that the air quality 
improvement in the Yuma area is due to permanent and enforceable 
emissions reductions and not the result of temporary or impermanent 
factors such as local economic downturn, temporary emissions 
reductions, or unusual or extreme weather patterns. Our conclusion is 
based on the observation that the ozone design value for the Yuma area 
has been below 0.070 ppm, the level of the 2015 ozone NAAQS, since 
2020.\57\ In sum, ambient ozone concentrations in the Yuma area have 
been consistently below the NAAQS since 2020 and have not been subject 
to large swings and disparate observations that might result from a 
sudden facility closure or an extreme weather pattern.
---------------------------------------------------------------------------

    \57\ Yuma Maintenance Plan, Figure 2-2.
---------------------------------------------------------------------------

    In conclusion, we find that the improvement in ambient air quality 
in the Yuma area is due to permanent and enforceable reductions in 
emissions of VOC and NO<INF>X</INF>, resulting from control measures 
such as (1) Federal vehicle standards and (2) stationary source control 
measures. Therefore, we propose to find that Arizona has satisfied the 
criterion for redesignation set forth at CAA section 107(d)(3)(E)(iii).

D. The Area Must Have a Fully Approved Maintenance Plan Under CAA 
Section 175A

    Section 107(d)(3)(E)(iv) of the CAA requires, as a pre-condition to 
being redesignated from nonattainment to attainment, that the 
Administrator has fully approved a maintenance plan for the area as 
meeting the requirements of section 175A of the Act.
    Section 175A of the CAA sets forth the elements of a maintenance 
plan for areas seeking redesignation from nonattainment to attainment. 
The maintenance plan is a SIP revision that provides for maintenance of 
the relevant NAAQS in the area for at least 10 years after 
redesignation. The Calcagni memo, dated September 4, 1992, provides 
additional guidance on the required content of a maintenance plan.
    A maintenance plan should address the following five areas: the 
attainment emissions inventory, maintenance demonstration, monitoring 
network, verification of continued attainment, and a contingency plan. 
The attainment emissions inventory identifies the emissions level in 
the area that is sufficient to attain the 2015 ozone NAAQS based on 
emissions during a three-year period which had no monitored violations. 
To demonstrate maintenance of the 2015 ozone NAAQS, ADEQ has projected 
the attainment emissions inventory through the first maintenance period 
and ensured that it was less than or equal to the inventory at the time 
of attainment. A maintenance plan must also include provisions for 
continued operation of an appropriate air quality monitoring network. 
The State must show how it will track and verify the progress of the 
maintenance plan. Finally, the maintenance plan must include a list of 
potential contingency measures which ensure prompt correction of any 
violation of the 2015 ozone NAAQS. Based on our review and evaluation 
of the Yuma Maintenance Plan, as described in the following sections, 
we are proposing to approve the Plan as meeting the requirements of CAA 
section 175A.
1. Attainment Inventories and Projected Future Inventories
    A maintenance plan should include an ``attainment emissions 
inventory'' of ozone precursors in the area to identify a level of 
emissions sufficient to attain the NAAQS.\58\ The attainment emissions 
inventory should be consistent with the EPA's most recent guidance on 
emissions inventories for nonattainment areas available at the time it 
was developed and should represent emissions during the timeframe 
associated with the ambient air quality monitoring data showing 
attainment of the NAAQS. The attainment inventory will generally be the 
actual inventory during the time period that the area attained the 
standard. The EPA has provided guidance for developing ozone emissions 
inventories in ``Emissions Inventory Guidance for Implementation of 
Ozone and Particulate Matter National Ambient Air Quality Standards 
(NAAQS) and Regional Haze Regulations''.\59\
---------------------------------------------------------------------------

    \58\ Calcagni memo, 8-9.
    \59\ ``Emissions Inventory Guidance for Implementation of Ozone 
and Particulate Matter National Ambient Air Quality Standards and 
Regional Haze Regulations,'' EPA-454/B-17-002, May 2017.
---------------------------------------------------------------------------

    ADEQ selected 2020 as the base year for the attainment inventory in 
the Yuma Maintenance Plan. The Yuma area attained the 2015 ozone NAAQS 
in 2020, and therefore, the emissions inventory from 2020 represents 
emissions levels consistent with continued attainment (i.e., 
maintenance) of the NAAQS. We consider the selection of the 2020 base 
year inventory to be appropriate given that it was the most recent 
emissions inventory associated with the reporting schedule required 
under the Air Emissions Reporting Requirements rule at the time of 
development of the Plan.
    Table 2 presents the VOC and NO<INF>X</INF> emissions estimates 
contained in the Yuma Maintenance Plan for 2020 and presents the Plan's 
projected emissions inventories of ozone precursors for an interim year 
(2030) and the maintenance plan's horizon year (2037).\60\
---------------------------------------------------------------------------

    \60\ The maintenance plan horizon year refers to the final year 
of the maintenance period covered by the plan.

[[Page 87835]]



                               Table 2--Yuma Area 2020 and Projected 2030 and 2037 VOC and NOX Ozone Season Day Emissions
                                                                  [Pounds per day] \a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       2020                            2030                            2037
                    Emissions source                     -----------------------------------------------------------------------------------------------
                                                                VOC             NOX             VOC             NOX             VOC             NOX
--------------------------------------------------------------------------------------------------------------------------------------------------------
Point...................................................             104           1,662           1,384           4,628           1,384           4,628
Nonpoint................................................           5,754           1,410           6,281           1,556           6,738           1,660
Mobile--Nonroad.........................................           1,792           1,620           1,720             923           1,754             782
Mobile--On-road.........................................           8,939           5,412           4,908           2,747           4,222           2,390
                                                         -----------------------------------------------------------------------------------------------
    Total \b\...........................................          16,589          10,104          14,293           9,854          14,098           9,460
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Source: Yuma Maintenance Plan, 43.
\b\ Emissions have been added to the Mobile--On-road emissions source category to account for safety margins added to proposed motor vehicle emissions
  budget. See the Yuma Maintenance Plan, page 50.

    The data shown in Table 3 in this document is based on the EPA's 
2020 national emissions inventory (NEI). The inventory addresses point 
sources,\61\ nonpoint sources,\62\ nonroad mobile sources,\63\ and on-
road mobile sources. Appendix A to the Yuma Maintenance Plan contains 
source-specific descriptions of emissions calculation procedures and 
sources of input data.
---------------------------------------------------------------------------

    \61\ For the Yuma Maintenance Plan, ``point sources'' include 
rock crusher/screener plants, electricity generation facilities, 
paper mills, gas filling stations, and vapor extraction units.
    \62\ For the Yuma Maintenance Plan, ``nonpoint sources'' include 
biogenic emissions, dry cleaning, surface coating, residential and 
industrial fuel combustion, and open burning.
    \63\ For the Yuma Maintenance Plan, ``Mobile--Nonroad sources'' 
includes agricultural, commercial, lawn and garden, pleasure craft, 
railroad, and recreational nonroad mobile sources.
---------------------------------------------------------------------------

    The EPA has reviewed the emissions inventory submitted by ADEQ and 
proposes to conclude that the Plan's inventory is based on reasonable 
assumptions and methodologies, and that the inventory is comprehensive, 
current, accurate, and consistent with applicable CAA provisions and 
the Calcagni memo. Therefore, we are proposing that the inventory is 
acceptable for use in demonstrating maintenance of the 2015 ozone 
NAAQS.
2. Maintenance Demonstration
    Section 175A(a) of the CAA requires that the maintenance plan 
``provide for the maintenance of the national primary ambient air 
quality standard for such air pollutant in the area concerned for at 
least 10 years after the redesignation.'' A State may generally 
demonstrate maintenance of the NAAQS by either showing that future 
emissions of a pollutant or its precursors will not exceed the level of 
the attainment inventory, or by conducting modeling that shows that the 
future mix of sources and emissions rates will not cause a violation of 
the NAAQS.\64\ Assumptions concerning emissions rates in maintenance 
demonstrations should generally reflect permanent, enforceable 
measures.\65\ Therefore, the analysis should assume that sources are 
operating at permitted levels (or historic peak levels), unless 
evidence is presented that such an assumption is unrealistic.\66\
---------------------------------------------------------------------------

    \64\ Calcagni memo, 9-11.
    \65\ Calcagni memo, 9.
    \66\ Id. at 4. See also, memorandum dated November 30, 1993, 
from Kent D. Berry, Acting Director, Air Quality Management 
Division, EPA, Subject: ``Use of Actual Emissions in Maintenance 
Demonstrations for Ozone and Carbon Monoxide (CO) Nonattainment 
Areas.''
---------------------------------------------------------------------------

    The Yuma Maintenance Plan demonstrates maintenance of the 2015 
ozone NAAQS for a ten-year period beginning in 2027. ADEQ used the 2020 
NEI and the Motor Vehicle Emission Simulator (MOVES) version 3.1 as the 
baseline to develop growth factors for point, nonpoint, mobile on-road, 
and mobile nonroad sources. For point sources, ADEQ used permitted 
potential to emit (PTE) levels of emissions, except for the Arizona 
Public Service (APS) Yucca Power Plant. ADEQ argues that, for the APS 
Yucca Power Plant, permitted PTE is calculated by assuming the facility 
would burn fuel oil at maximum capacity, overestimating emissions from 
the facility. ADEQ argues that the facility runs primarily on natural 
gas and burns little fuel oil each year.\67\ Therefore, ADEQ used 
historic high emissions from 2018 for the baseline. We agree that this 
method for estimating emissions from APS Yucca Power Plant is 
consistent with EPA guidance. For nonpoint sources, ADEQ used the 2020 
NEI held constant, or multiplied by a projection factor based on 
population.\68\ ADEQ used MOVES 3.1 to model future on-road emissions, 
using Arizona Department of Transportation vehicle registration data 
and MOVES defaults.\69\ ADEQ used the EPA defaults for Yuma County and 
applied a population allocation factor to apportion the county-wide 
nonroad mobile source emissions to the Yuma nonattainment area. ADEQ 
also used MOVES to model future nonroad mobile source emissions.
---------------------------------------------------------------------------

    \67\ For the year 2018, the APS Yucca Power Plant utilized 99.3 
percent natural gas and 0.7 percent fuel oil. For a demonstration 
and justification for this estimation method, see the Yuma 
Maintenance Plan, appendix A, section A8.1, A-54.
    \68\ Yuma Maintenance Plan, appendix A, A-41, A-42.
    \69\ Yuma Maintenance Plan, appendix A, A-42-A-50.
---------------------------------------------------------------------------

    Table 2 compares the VOC and NO<INF>X</INF> emissions estimated for 
the Yuma area for 2020 with those projected for 2030 and 2037 by source 
category. The projected VOC and NO<INF>X</INF> emissions show that VOC 
and NO<INF>X</INF> emissions are projected to remain below the 
attainment levels throughout the 10-year period following 
redesignation.
3. Monitoring Network
    Once an area has been redesignated, the State should continue to 
operate an appropriate air quality monitoring network in accordance 
with 40 CFR part 58 to verify the attainment status of the area.\70\ 
Data collected by the monitoring network are also needed to determine 
if the contingency provisions of the maintenance plan are triggered. 
ADEQ currently operates one ozone monitor (the Yuma Supersite monitor) 
in the Yuma area.
---------------------------------------------------------------------------

    \70\ Calcagni memo, 11.
---------------------------------------------------------------------------

    In the Yuma Maintenance Plan \71\ ADEQ indicates its intention to 
continue operation of an air quality monitoring network to verify 
continued attainment of the 2015 ozone NAAQS.\72\ We approved ADEQ's 
State and Local Air Monitoring Stations (SLAMS) air quality network in 
their annual monitoring network plan for year 2023

[[Page 87836]]

on October 30, 2023, prior to ADEQ's submittal of the Yuma Maintenance 
Plan.\73\ We find ADEQ's commitment for continued ambient ozone 
monitoring set forth in the Yuma Maintenance Plan to be acceptable for 
the purpose of verifying continued maintenance in the Yuma area.
---------------------------------------------------------------------------

    \71\ Yuma Maintenance Plan, 43.
    \72\ Although the Yuma Maintenance Plan is not explicit in this 
regard, we presume that ADEQ's intention to continue operation of a 
monitoring network indicates the agency's intention to do so 
consistent with the EPA's monitoring requirements in 40 CFR part 58 
(``Ambient Air Quality Surveillance'').
    \73\ The EPA's requirements for annual review of monitoring 
networks are no longer codified at 40 CFR 58.20(d) but are now found 
at 40 CFR 58.10.
---------------------------------------------------------------------------

4. Verification of Continued Attainment
    Each State should ensure that it has the legal authority to 
implement and enforce all measures necessary to maintain the NAAQS.\74\
---------------------------------------------------------------------------

    \74\ Calcagni memo, 11.
---------------------------------------------------------------------------

    ADEQ has the legal authority to implement and enforce the 
requirements of the Yuma Maintenance Plan under title 49 of the Arizona 
Revised Statutes, ``The Environment.'' This includes the authority to 
adopt, implement, and enforce any emissions control contingency 
measures determined to be necessary to correct 2015 ozone NAAQS 
violations. To verify continued attainment, ADEQ committed to the 
continued operation of an ozone monitoring network that meets the EPA 
air quality surveillance requirements. In addition, ADEQ committed to 
track the progress of the maintenance plan through continued 
development and submission of periodic emissions inventories to the EPA 
and review of the inventory to determine whether changes could affect 
maintenance of the 2015 ozone NAAQS. These methods are sufficient for 
the purpose of verifying continued attainment.
5. Contingency Provisions
    Section 175A(d) of the CAA requires that maintenance plans contain 
contingency provisions, as the EPA deems necessary, to promptly correct 
any violations of the NAAQS that occur after redesignation of the area. 
Such provisions must include a requirement that the State will 
implement all measures with respect to the control of the air pollutant 
concerned that were contained in the SIP prior to the area being 
redesignated to attainment. These contingency provisions are 
distinguished from contingency measures required for nonattainment 
areas under CAA section 172(c)(9) in that they are not required to be 
fully adopted measures that will take effect without further action by 
the State for the maintenance plan to be approved. The contingency 
provisions of a maintenance plan are, however, an enforceable part of 
the SIP and should ensure that contingency measures are adopted 
expeditiously once the Plan's contingency provisions are triggered by a 
specified event. Thus, a State should identify the specific indicators 
or triggers that will be used to determine when the contingency 
measures need to be implemented. Next, the maintenance plan should 
clearly identify the measures to be adopted, include a schedule and 
procedure for adoption and implementation of the measures, and contain 
a specific timeline for action by a State.
    As required by section 175A of the CAA, ADEQ has adopted a 
contingency plan to address possible future ozone air quality 
problems.\75\ ADEQ identifies two triggers: a warning level response 
and action level response. The warning level response would be 
triggered if an annual 4th high monitored concentration is above the 
level of the 2015 ozone NAAQS. This would initiate an analysis to 
determine whether the high ozone concentrations indicate a trend 
towards high ozone levels. The study would include an assessment of 
meteorological conditions and an assessment of whether actual emissions 
have deviated significantly from the emissions projections contained in 
the maintenance plan, along with an evaluation of which source sectors 
are responsible for emissions increases. The action level response 
would be triggered if a certified design value exceeds the level of the 
2015 ozone NAAQS. Within 18 months of the certified design value 
exceedance, ADEQ commits to identify and implement necessary control 
measures.
---------------------------------------------------------------------------

    \75\ Yuma Maintenance Plan, 45-47.
---------------------------------------------------------------------------

    Potential contingency measures listed in the maintenance plan are 
those emissions controls or other measures that ADEQ may choose to 
adopt and implement in response to the contingency trigger. The 
contingency plan lists the following potential contingency provisions 
that will be considered for adoption and implementation by the 
applicable State agency, while the Plan indicates that the list is not 
considered to be exhaustive:
    <bullet> Anti-idling control program for mobile sources, targeting 
diesel vehicles;
    <bullet> Diesel exhaust retrofits;
    <bullet> Traffic flow improvements;
    <bullet> Park and ride facilities; and
    <bullet> Rideshare/carpool program.
    Upon our review of the Plan, we find that the contingency 
provisions in the Yuma Maintenance Plan clearly identify specific 
contingency measures, contain sufficient tracking and triggering 
mechanisms to determine when contingency provisions are needed, contain 
an adequate description of the process of recommending and implementing 
contingency measures, and contain specific timelines for action. Thus, 
we conclude that the contingency provisions of the Yuma Maintenance 
Plan are adequate to ensure prompt correction of a violation and 
therefore comply with section 175A(d) of the Act.
6. Motor Vehicle Emissions Budgets
    Section 176(c) of the CAA requires Federal actions in nonattainment 
and maintenance areas to conform to the SIP's goals of eliminating or 
reducing the severity and number of violations of the NAAQS and 
achieving expeditious attainment of the standards. Conformity to the 
SIP's goals means that such actions will not: (1) cause or contribute 
to violations of the NAAQS, (2) worsen the severity of an existing 
violation, (3) or delay timely attainment of any NAAQS or any interim 
milestone.
    Actions involving Federal Highway Administration (FHWA) or Federal 
Transit Administration (FTA) funding or approval are subject to the 
EPA's transportation conformity rule, codified in 40 CFR part 93, 
subpart A. Under this rule, regional transit authorities in 
nonattainment and maintenance areas coordinate with State and local air 
quality and transportation agencies, the EPA, FHWA, and FTA to 
demonstrate that an area's regional transportation plans and 
transportation improvement programs conform to the applicable SIP. This 
demonstration is typically done by showing that estimated emissions 
from existing and planned highway and transit systems are less than or 
equal to the motor vehicle emissions budgets (``budgets'') contained in 
submitted or approved control strategy SIPs and maintenance plans.\76\
---------------------------------------------------------------------------

    \76\ Control strategy SIPs refer to reasonable further progress 
(RFP) and attainment demonstration SIPs. 40 CFR 93.101.
---------------------------------------------------------------------------

    These control strategy SIPs and maintenance plans typically set 
budgets for criteria pollutants and/or their precursors to address 
pollution from cars and trucks. Budgets are generally established for 
specific years and specific pollutants or precursors. Maintenance plan 
submittals should identify budgets for transportation related VOC and 
NO<INF>X</INF> emissions in the last year of the maintenance period.
    For budgets in a maintenance plan to be approvable, they must meet, 
at a minimum, the EPA's adequacy criteria.\77\ To meet these 
requirements,

[[Page 87837]]

the budgets must be consistent, when considered with emissions from all 
other sources, with maintenance of the NAAQS and reflect all the motor 
vehicle control measures relied upon for the maintenance demonstration. 
The EPA's process for determining adequacy of a budget consists of 
three basic steps: (1) providing public notification of a SIP 
submission; (2) providing the public the opportunity to comment on the 
budgets during a public comment period; and (3) making a finding of 
adequacy. The process for determining the adequacy of a submitted 
budget is codified at 40 CFR 93.118(f). The EPA can notify the public 
by either posting an announcement that the EPA has received SIP budgets 
on the EPA's adequacy website,\78\ or via a Federal Register notice of 
proposed rulemaking when the EPA reviews the adequacy of a maintenance 
plan budget simultaneously with its review and action on the SIP 
submittal itself.\79\
---------------------------------------------------------------------------

    \77\ 40 CFR 93.118(e)(4) and (5). For more information on the 
transportation conformity requirement and applicable policies on 
budgets, which can be found at https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-93.
    \78\ See the EPA adequacy website: https://www.epa.gov/state-and-local-transportation/state-implementation-plans-sip-submissions-currently-under-epa.
    \79\ See the EPA memorandum dated July 15, 2024, titled: 
``Adequacy Documentation for Motor Vehicle Emissions Budgets in the 
Yuma Maintenance Plan.''
---------------------------------------------------------------------------

    The Yuma Maintenance Plan contains VOC and NO<INF>X</INF> budgets 
for 2020, 2030, and 2037. Any and all comments on the approvability of 
the budgets should be submitted during the comment period stated in the 
Dates section of this document.
    The EPA proposes to approve the 2020, 2030, and 2037 budgets in the 
Yuma Maintenance Plan for transportation conformity purposes. If the 
EPA issues a final action to approve the budgets, these budgets must be 
used in future transportation conformity determinations for the Yuma 
area for the 2015 ozone standard.
    The new budgets, if approved in the final rulemaking, will be 
effective on the date of publication of the EPA's final rulemaking in 
the Federal Register. The applicable VOC and NO<INF>X</INF> budgets for 
the Yuma nonattainment area are defined in Table 3.

   Table 3--Proposed Motor Vehicle Emissions Budgets for the Yuma Area
                      [Pounds per ozone season day]
------------------------------------------------------------------------
                      Budget year                         VOC      NOX
------------------------------------------------------------------------
2020..................................................    8,939    5,412
2030..................................................    4,908    2,747
2037..................................................    4,222    2,390
------------------------------------------------------------------------
Source: Yuma Maintenance Plan, Table 7-1.

    The budgets are the on-road mobile source VOC and NO<INF>X</INF> 
emissions for the Yuma area for 2020, 2030, and 2037. The budgets are 
compatible with the 2020, 2030, and 2037 on-road mobile source VOC and 
NO<INF>X</INF> emissions included in Yuma's 2020, 2030 and 2037 
emissions inventories, as summarized in Table 2. The derivation of the 
budget is thoroughly discussed in appendix A to the Yuma Maintenance 
Plan.
    We evaluated the budgets against our adequacy criteria in 40 CFR 
93.118(e)(4) and (5) as part of our review of the budget's 
approvability and expect to complete the adequacy review of the budgets 
concurrent with our final action on the Yuma Maintenance Plan. The EPA 
is not required under its transportation conformity rule to find 
budgets adequate prior to proposing approval of them. In this notice, 
the EPA is announcing that the adequacy process for these budgets 
begins, and the public has 30 days to comment on their adequacy, per 
the transportation conformity rule at 40 CFR 93.118(f)(2)(i) and (ii).
    ADEQ developed budgets for 2020, 2030 and 2037 using on-road motor 
vehicle emission estimates using the EPA's MOVES3 model fleet data from 
Arizona Motor Vehicle Division registration data, and travel demand 
modeling from the Yuma Metropolitan Planning Organization (YMPO). As 
documented in a separate memorandum \80\ included in the docket for 
this rulemaking, we preliminarily conclude that the budgets in the Yuma 
Maintenance Plan meet each adequacy criterion. While adequacy and 
approval are two separate actions, reviewing the budgets in terms of 
the adequacy criteria informs the EPA's decision to propose to approve 
the budgets. We have completed our detailed review and are proposing to 
approve the demonstration of maintenance for the 2015 ozone area 
through the year 2037. We have also reviewed the budgets in the Yuma 
Maintenance Plan and found that they are consistent with the 
maintenance demonstration for which we are proposing approval, are 
clearly identified and precisely quantified, are based on control 
measures that have already been adopted and implemented and meet all 
other applicable statutory and regulatory requirements including the 
adequacy criteria in 40 CFR 93.118(e)(4) and (5). The EPA is proposing 
to approve the budgets for 2020, 2030, and 2037 as part of our approval 
of the Yuma Maintenance Plan. Once the EPA finalizes the adequacy 
process or approves the budgets as proposed (whichever occurs first, 
noting that finalization of the adequacy process and approval of the 
budgets may also occur concurrently per 40 CFR 93.118(f)(2)(iii)), the 
budgets must be used by YMPO for transportation conformity 
determinations for the Yuma area.
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    \80\ See the EPA memorandum dated July 15, 2024, titled: 
``Adequacy Documentation for Motor Vehicle Emissions Budgets in the 
Yuma Maintenance Plan.''
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IV. Proposed Action and Request for Public Comment

    Under CAA section 110(k)(3), and for the reasons set forth in this 
document, the EPA is proposing to approve the Yuma Maintenance Plan 
submitted by ADEQ on December 27, 2023, as a revision to the Arizona 
SIP,\81\ and to redesignate the Yuma nonattainment area to attainment 
for the 2015 ozone NAAQS. We are proposing to approve the maintenance 
demonstration and contingency provisions as meeting all applicable 
requirements for maintenance plans and related contingency provisions 
in CAA section 175A, and the budgets for 2020, 2030 and 2037 (shown in 
Table 4) for transportation conformity purposes as we find they meet 
all applicable criteria for such budgets including the adequacy 
criteria under 40 CFR 93.118(e). We are soliciting comments on these 
proposed actions. We will accept comments from the public for 30 days 
following publication of this proposal in the Federal Register and will 
consider any relevant comments before taking final action.
---------------------------------------------------------------------------

    \81\ Yuma Maintenance Plan (submitted electronically December 
27, 2023).
---------------------------------------------------------------------------

V. Statutory and Executive Order Review

    Under the CAA, redesignation of an area to attainment and the 
accompanying approval of a maintenance plan under section 107(d)(3)(E) 
are actions that affect the status of a geographical area and do not 
impose any additional regulatory requirements on sources beyond those 
imposed by State law. A redesignation to attainment does not in and of 
itself create any new requirements, but rather results in the 
applicability of requirements contained in the CAA for areas that have 
been redesignated to attainment. Moreover, the Administrator is 
required to approve a SIP submission that complies with the provisions 
of the CAA 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

[[Page 87838]]

the criteria of the CAA. Accordingly, this action merely approves State 
law as meeting Federal requirements and does not impose additional 
requirements beyond those imposed by State law. For that reason, this 
proposed action:
    <bullet> 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 13563 (76 FR 3821, January 21, 
2011);
    <bullet> Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
    <bullet> 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.);
    <bullet> Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
    <bullet> Does not have federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
    <bullet> Is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
    <bullet> Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
    <bullet> 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; and
    <bullet> Will not have disproportionately high and adverse human 
health or environmental effects on minority populations, low-income 
populations and/or indigenous peoples, as specified in Executive Order 
12898 (59 FR 7629, February 16, 1994), as discussed in section VI of 
this proposal.
    The EPA has identified Tribal areas within the Yuma area covered by 
this rulemaking that would be potentially affected by this proposed 
action. Specifically, the Cocopah Tribe of Arizona and the Quechan 
Tribe of the Fort Yuma Indian Reservation are located within the 
boundaries of the Yuma area.
    The EPA has concluded that the final rule may have Tribal 
implications for these tribes for the purposes of transportation 
conformity only, as this document sets motor vehicle emissions budgets 
for ozone precursors for the Yuma area, which includes some Tribal 
roads. The EPA has communicated with the potentially affected tribes 
located within the boundaries of the Yuma nonattainment area.\82\
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    \82\ Letter dated June 4, 2024, from Matthew Lakin, Director, 
EPA Region IX to Sherry Cordova, Chairwoman, Cocopah Tribe of 
Arizona, Subject: ``Invitation to Consult on a Redesignation Request 
and Maintenance Plan from the State of Arizona for the 2015 Ozone 
National Ambient Air Quality Standards (NAAQS),'' and letter dated 
June 4, 2024 from Matt Lakin, Director, EPA Region IX to Jordan 
Joaquin, President, Quechan Tribe of the Fort Yuma Indian 
Reservation, Subject: ``Invitation to Consult on a Redesignation 
Request and Maintenance Plan from the State of Arizona for the 2015 
Ozone National Ambient Air Quality Standards (NAAQS).''
---------------------------------------------------------------------------

    Executive Order 12898 (Federal Actions To Address 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 communities with environmental justice 
(EJ) concerns to the greatest extent practicable and permitted by law. 
EPA defines 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.'' 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 the 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. EPA did not perform an EJ analysis and did not consider EJ 
in this action. Due to the nature of the action being taken here, 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 action, and there is no information in the record 
inconsistent with the stated goal of E.O. 12898 of achieving 
environmental justice for communities with EJ concerns.

List of Subjects

40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Nitrogen dioxide, Reporting and recordkeeping requirements, 
Sulfur Dioxide, Volatile organic compounds.

 40 CFR Part 81

    Environmental Protection, Air pollution control.

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

    Dated: October 29, 2024.
Martha Guzman Aceves,
Regional Administrator, Region IX.
[FR Doc. 2024-25575 Filed 11-4-24; 8:45 am]
BILLING CODE 6560-50-P


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