Document ID: EPA-R09-OAR-2021-0869-0001
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: Arizona; Maintenance Plan and Redesignation Request; Nogales PM2.5 Planning Area
Posted Date: 2022-03-02T05:00Z

[Federal Register Volume 87, Number 41 (Wednesday, March 2, 2022)]
[Proposed Rules]
[Pages 11664-11680]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-04070]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52 and 81

[EPA-R09-OAR-2021-0869; FRL-9503-01-R9]

Maintenance Plan and Redesignation Request; Nogales PM2.5 
Planning Area; Arizona

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve the ``FINAL SIP Revision: Nogales PM2.5 Maintenance 
Plan and Redesignation Request (2006 Fine Particulate NAAQS)'' 
(``Nogales Maintenance Plan'' or ``Plan'') as a revision to the state 
implementation plan (SIP) for the State of Arizona. The Nogales 
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 ten-year 
maintenance period. The EPA is also proposing to approve the State of 
Arizona's request to redesignate the Nogales area from nonattainment to 
attainment for the 24-hour national ambient air quality standard (NAAQS 
or ``standard'') for particulate matter of 2.5 micrometers or less 
(PM2.5). The EPA is proposing these

[[Page 11665]]

actions because this SIP revision meets the applicable Clean Air Act 
(CAA or ``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 Nogales area.

DATES: Written comments must arrive on or before April 1, 2022.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2021-0869 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, or if you need assistance in a language 
other than English or if you are a person with disabilities who needs a 
reasonable accommodation at no cost to you, 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.

FOR FURTHER INFORMATION CONTACT: Anita Lee, Air Planning Office (ARD-
2), EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105, (415) 
972-3958, or by email at [email protected].

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

Table of Contents

I. Background
    A. The PM2.5 National Ambient Air Quality Standards
    B. The Nogales Area and Regulatory Actions
    C. CAA and Regulatory Requirements for Redesignations and 
Maintenance Plans
II. Submissions from the State of Arizona to Redesignate the Nogales 
Area to Attainment of the 24-Hour PM2.5 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 Nogales 
Area
    A. Evaluation of Whether the Nogales Area Has Attained the PM2.5 
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. Environmental Justice Considerations
V. Proposed Action and Request for Public Comment
VI. Statutory and Executive Order Reviews

I. Background

A. The PM2.5 National Ambient Air Quality Standards

    The EPA sets the NAAQS for certain ambient air pollutants at levels 
required to protect human health and the environment. Particulate 
matter with an aerodynamic diameter less than or equal to 2.5 
micrometers, or PM2.5, is one of these ambient air 
pollutants for which the EPA has established health-based standards. On 
July 18, 1997, the EPA established the first NAAQS for PM2.5 
(``the 1997 PM2.5 Standards''), including an annual standard 
of 15.0 micrograms per cubic meter ([mu]g/m\3\) based on a three-year 
average of annual mean PM2.5 concentrations, and a 24-hour 
(or daily) standard of 65 [mu]g/m\3\ based on a three-year average of 
the 98th percentile of 24-hour concentrations.\1\ The EPA established 
the 1997 PM2.5 NAAQS based on significant evidence and 
numerous health studies demonstrating the serious health effects 
associated with exposures to PM2.5. Subsequently, on October 
17, 2006, the EPA strengthened the 24-hour PM2.5 NAAQS by 
revising it to 35 [mu]g/m\3\ and retained the level of the annual 
PM2.5 standard at 15.0 [mu]g/m\3\.\2\
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    \1\ 62 FR 38652.
    \2\ 71 FR 61144.
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B. The Nogales 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(d)(1) of the CAA. Effective 
December 14, 2009, the EPA established the initial air quality 
designations for most areas in the United States for the 2006 24-hour 
PM2.5 NAAQS.\3\ Among these areas so designated in 2009, the 
EPA designated the Nogales planning area (``Nogales area'') as 
nonattainment for the 2006 24-hour PM2.5 NAAQS based on 
monitoring data from 2004 through 2007. The Nogales area covers 76.1 
square miles and is in southern Santa Cruz County, Arizona, adjacent to 
the international border with Mexico and the city of Nogales, Sonora, 
Mexico.\4\
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    \3\ 74 FR 58688 (November 13, 2009).
    \4\ The legal nonattainment area boundaries for the Nogales area 
are described in 40 CFR 81.303. ADEQ provided a map portraying these 
boundaries in the Nogales Maintenance Plan, 5, Figure 2.
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    On June 2, 2014, the EPA classified as ``Moderate'' all areas that 
were designated nonattainment for the 1997 and/or 2006 PM2.5 
standards at the time under subpart 4 of part D of CAA title I, 
including the Nogales area.\5\ The EPA also established a due date of 
December 31, 2014, for states to submit SIP revisions related to 
attainment and nonattainment new source review required for these areas 
pursuant to subpart 4.
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    \5\ 79 FR 31566.
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    On January 7, 2013, the EPA issued a determination under our clean 
data policy (a ``clean data determination'') for the Nogales area in 
relation to the 2006 24-hour PM2.5 NAAQS based on three 
years of complete, quality-assured, and certified data for the 2009-
2011 time frame.\6\ The EPA's clean data determination for the Nogales 
area suspended, for so long as the area continues to attain the 2006 
PM2.5 NAAQS, CAA requirements in sections 172 and 189 for an 
attainment demonstration, reasonably available control measure (RACM) 
demonstration, and reasonable further progress (RFP) demonstration; it 
also suspended the contingency measure provisions in section 172.\7\
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    \6\ 78 FR 887.
    \7\ For a discussion of the clean data determination for the 
Nogales area and our clean data policy, see our October 30, 2012 
proposed rulemaking (77 FR 65656). Also, the EPA codified the clean 
data policy in regulation as part of the PM2.5 
implementation rule finalized on August 24, 2016; 81 FR 58010 
(codified at 40 CFR 51.1015).
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    Although the EPA's clean data determination suspended certain CAA 
requirements for the State, the requirement to submit PM2.5 
emissions inventories consistent with CAA section 172(c)(3) remained. 
Consequently, in September 2013, Arizona submitted to the EPA emissions 
inventories for PM2.5 and PM2.5 precursors 
(oxides of nitrogen (NOX), volatile organic compounds 
(VOCs), sulfur dioxide (SO2),\8\ and ammonia 
(NH3)). The EPA approved

[[Page 11666]]

these PM2.5 and precursor emissions inventories on February 
9, 2015.\9\
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    \8\ SO2 is commonly used as the indicator for all 
gaseous sulfur oxides (SOX).
    \9\ 80 FR 6907.
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    In May 2017, as required by the CAA, the EPA determined that the 
Nogales area attained the 2006 24-hour PM2.5 NAAQS by 
December 31, 2015, the date specified by the Act.\10\ The EPA relied on 
2013-2015 ambient PM2.5 data in making this determination 
that the Nogales area attained the NAAQS by the applicable date.
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    \10\ 82 FR 21711 (May 10, 2017).
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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 of 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 fully approved the applicable 
implementation plan 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 particulate matter-
specific SIP requirements are found in subpart 4 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,\11\ and supplemented on April 28, 
1992 (collectively referred to herein as the ``General Preamble'').\12\ 
The EPA issued additional guidance in two memoranda: A September 4, 
1992 memorandum from John Calcagni, Director, Air Quality Management 
Division, EPA Office of Air Quality Planning and Standards, titled 
``Procedures for Processing Requests to Redesignate Areas to 
Attainment'' (referred to herein as the ``Calcagni memo''); and, a 1994 
memorandum from Mary D. Nichols, titled ``Part D New Source Review 
(part D NSR) Requirements for Areas Requesting Redesignation to 
Attainment'' (``Nichols memo'').
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    \11\ 57 FR 13498.
    \12\ 57 FR 18070.
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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 Nogales Maintenance Plan and to approve 
Arizona's request for redesignation of the Nogales area to attainment 
for the 2006 24-hour PM2.5 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 Nogales 
Area To Attainment of the 24-Hour PM2.5 NAAQS

A. Summary of State Submissions

    On April 13, 2021, the Arizona Department of Environmental Quality 
(ADEQ) submitted to the EPA its redesignation request and the Nogales 
Maintenance Plan as a revision to the Arizona SIP.\13\ This document 
addresses all of the CAA section 107(d)(3)(E) requirements for 
redesignating a nonattainment area to attainment of the NAAQS and 
includes the required maintenance plan elements. The Nogales 
Maintenance Plan is organized into seven chapters and five appendices 
with the maintenance plan elements found in Chapters 5 and 6. The five 
appendices provide support for the Plan and are divided into the 
following categories: Technical support and documentation for emissions 
inventories (appendices B-D); and SIP adoption authority, public notice 
and hearing documentation (appendices A and E).
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    \13\ Letter dated April 7, 2021, from Daniel Czecholinski, 
Director, Air Quality Division, Arizona Department of Environmental 
Quality, to Deborah Jordan, Acting Regional Administrator, EPA 
Region IX. Subsequently, Arizona made an electronic submittal of the 
Nogales Maintenance Plan on April 13, 2021, via the EPA's State Plan 
Electronic Collection System.
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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 provided public notice and opportunity for public comment on 
the Nogales Maintenance Plan. On December 29, 2020, ADEQ released a 
draft of the Nogales Maintenance Plan for public review and published a 
notice of public meeting to be held on January 28, 2021, to consider 
adoption of the Nogales Maintenance Plan.\14\ Following a virtual 
public hearing on January 28, 2021,\15\ ADEQ adopted the Nogales 
Maintenance Plan as a revision to the Arizona SIP on April 7, 2021, and 
submitted the Plan to the EPA on April 13, 2021. On October 13, 2021, 
the Nogales Maintenance Plan became complete by operation of law 
pursuant to CAA section 110(k)(1)(B).
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    \14\ ``Arizona Department of Environmental Quality and Public 
Comment Period and Hearing'' published in the Nogales International 
on December 29, 2020, and January 1, 2021; Exhibit E-III, Appendix 
E, Nogales PM2.5 Maintenance Plan. A similar public 
notice appeared on the ADEQ website.
    \15\ ``Public Hearing Presiding Officer Certification'' signed 
by Zachary Dorn, Presiding Officer, notarized and dated February 17, 
2021, Appendix E, Nogales Maintenance Plan. The hearing transcript, 
the public comments, and State responses are also found in Appendix 
E of the Nogales Maintenance Plan.
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    Based on information provided in the SIP submission and summarized 
in this proposal, the EPA proposes to find that the submittal of the 
Nogales Maintenance Plan meets the procedural requirements for public 
notice and hearing in CAA sections 110(a) and 110(l) and 40 CFR 51.102.

[[Page 11667]]

III. Evaluation of Arizona's Redesignation Request for the Nogales Area

A. Evaluation of Whether the Nogales Area Has Attained the PM2.5 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.\16\ 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.\17\ State, local, or tribal agencies 
that operate air monitoring sites in accordance with 40 CFR part 58 
must enter the ambient air quality data and associated quality 
assurance data from these sites in the EPA Air Quality System (AQS) 
database.\18\ These monitoring agencies certify annually that these 
data are accurate to the best of their knowledge, taking into 
consideration the quality assurance findings.\19\ Accordingly, the EPA 
relies primarily on AQS data when determining the attainment status of 
an area.
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    \16\ 57 FR 13563.
    \17\ 40 CFR 58.2(a).
    \18\ 40 CFR 58.16. AQS is the EPA's national repository of 
ambient air quality data.
    \19\ 40 CFR 58.15(a).
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    In accordance with 40 CFR part 50, Appendix N, generally the EPA's 
finding of attainment of the 2006 24-hour PM2.5 NAAQS must 
be based upon complete, certified data gathered at eligible monitoring 
sites in the nonattainment area in accordance with 40 CFR part 58 and 
entered in AQS.\20\ For the 24-hour PM2.5 standard, Appendix 
N section 1.0(c) defines eligible monitoring sites as those that meet 
the technical requirements in 40 CFR 58.11. Under 40 CFR 50.13 and in 
accordance with part 50, Appendix N, an area meets the 2006 24-hour 
PM2.5 NAAQS when the design value at each eligible 
monitoring site within the area is less than or equal to 35 [mu]g/m\3\, 
based on the rounding convention in 40 CFR part 50, Appendix N.\21\
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    \20\ 40 CFR part 50, Appendix N, section 3.0.
    \21\ The 24-hour PM2.5 standard design value is the 
three-year average of 98th percentile of 24-hour concentrations.
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    To have a valid design value showing attainment of the 
PM2.5 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 75 percent of the scheduled sampling days for each 
quarter have valid data.\22\ In determining whether data are suitable 
for regulatory determinations, the EPA uses a ``weight of evidence'' 
approach, considering the requirements of 40 CFR part 58, Appendix A 
``in combination with other data quality information, reports, and 
similar documentation that demonstrate overall compliance with Part 
58.'' \23\
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    \22\ 40 CFR part 50, Appendix N, section 4.2(b).
    \23\ 40 CFR part 58, Appendix A, section 1.2.3.
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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 for the Nogales area. As a result, ADEQ submits annual 
monitoring network plans to the EPA.\24\ 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 
PM2.5, we have found that the annual network plans submitted 
by ADEQ meet these requirements under 40 CFR part 58, including minimum 
monitoring requirements.\25\ The Nogales Post Office monitoring site 
(AQS ID: 04-023-0004) is the only PM2.5 monitoring site in 
the Nogales area.\26\
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    \24\ We have included in our docket copies of Arizona's 
monitoring network plans for 2018-2020, e.g., ``State of Arizona Air 
Monitoring Network Plan for the Year 2020.''
    \25\ We have included in our docket our reviews of ADEQ's annual 
network plans and the correspondence transmitting these reviews, 
e.g., correspondence dated October 28, 2020, from Gwen Yoshimura, 
Manager, Air Quality Analysis Office, EPA Region IX, to Daniel 
Czecholinski, Director, Air Quality Division, ADEQ.
    \26\ See, e.g., ``State of Arizona Air Monitoring Network Plan 
for the Year 2020,'' Table 2.2-1, ``SIP Network Monitoring 
Requirements.''
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    In accordance with 40 CFR 58.15, ADEQ certifies annually that the 
previous year's ambient concentration and quality assurance data are 
completely submitted to AQS and that the ambient concentration data are 
accurate, taking into consideration the quality assurance findings.\27\ 
Along with the certification letters, ADEQ submits a summary of the 
precision and accuracy data for all ambient air quality data.\28\ The 
EPA's evaluations of the relevant quality assurance data are reflected 
in the associated AQS design value reports.\29\ These reports include a 
certification evaluation and concurrence (``Cert&Eval'') flag 
indicating the overall quality of the corresponding monitoring data. 
Over the period 2018-2020, the associated Cert&Eval flag in the design 
value report was ``Y'' for the Nogales Post Office PM2.5 
monitoring site, 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).'' \30\
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    \27\ We have included in our docket ADEQ's annual data 
certifications for 2018, 2019, and 2020, e.g., correspondence dated 
April 26, 2021, from Daniel Czecholinski, Director, Air Quality 
Division, ADEQ, to Gwen Yoshimura, Manager, Air Quality Analysis 
Office, EPA Region IX. Annual data certification requirements can be 
found at 40 CFR 58.15.
    \28\ 40 CFR 58.15(c).
    \29\ AQS, Design Value Report (AMP480), dated November 19, 2021.
    \30\ Id.
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    The Nogales area Design Value Report also included a validity 
indicator (``Valid Ind.'') 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 2018-2020 period for completeness and determined that 
the PM2.5 data collected by ADEQ met the 75 percent 
completeness criterion for all 12 quarters at the PM2.5 
monitoring site in the Nogales area.\31\
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    \31\ Id.
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    Finally, the EPA conducts regular technical systems audits (TSAs) 
where we review and inspect state and local ambient air monitoring 
programs to assess compliance with applicable regulations concerning 
the collection, analysis, validation, and reporting of ambient air 
quality data. For the purposes of this proposal, we reviewed the 
findings from the EPA's 2018 TSA of ADEQ's ambient air monitoring 
program.\32\ In Finding 11 of the 2018 TSA, the EPA noted that:
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    \32\ Technical Systems Audit of the Ambient Air Monitoring 
Program: Arizona Department of Environmental Quality, April 2--April 
6, 2018; Final Report dated April 2019 (``2018 TSA''). The 2018 TSA 
is attached to its transmittal letter dated April 25, 2019, from 
Elizabeth J. Adams, EPA Region IX, to Timothy J. Franquist, ADEQ.

[[Page 11668]]

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    The distance between collocated PM2.5 monitors were 
not being met at Nogales Post Office (AQS ID: 04-023-0004). The 
primary Federal Reference Method (FRM) PM2.5 monitor was 
4.5 meters from the collocated FRM PM2.5 monitor and 
therefore not meeting the requirement of 2 to 4 meters between 
monitors. Additionally, the collocated FRM PM2.5 monitor 
was closer to the side of the building than the primary FRM 
PM2.5 monitor and was close to not meeting siting 
requirements. Since the collocated FRM PM2.5 monitor was 
4.5 meters closer to the side of the building than the primary FRM 
PM2.5 monitor, the monitor pair could measure different 
concentrations.\33\
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    \33\ Id. at 24.

    To address this finding, ADEQ moved the collocated monitor to 2.2 
meters from the primary FRM monitor on February 2, 2019.\34\
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    \34\ Letter dated July 2, 2019, from Daniel Czecholinski, 
Director, Air Quality Division, ADEQ, to Gwen Yoshimura, Manager, 
Air Quality Analysis Office, EPA Region IX, Attachment: Finding 
Corrective Action Form.
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    The EPA did not recommend invalidating any data from the Nogales 
Post Office monitoring site based on this TSA finding.\35\ The purpose 
of distance requirements for collocated PM2.5 monitors is to 
ensure that the two monitors measure similar concentrations so that 
data from the monitors can be compared to estimate the precision of the 
measurements.\36\ Under the EPA's weight of evidence approach for 
evaluating the suitability of data for regulatory purposes, the 
precision of PM2.5 measurements is considered a systematic 
criterion,\37\ meaning that it is important for the correct 
interpretation of the data, but it does not usually affect the validity 
of a sample or group of samples.\38\ Accordingly, the fact that the 
collocated monitors were 4.5 meters apart does not affect the validity 
of the data collected at the Nogales Post Office monitoring site.
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    \35\ 2018 TSA Report, 24.
    \36\ 40 CFR part 58, Appendix A, sections 3.2.3 and 4.2.1.
    \37\ EPA, Quality Assurance Handbook for Air Pollution 
Measurement Systems (``QA Handbook''), Vol. II, Ambient Air Quality 
Monitoring Program, appendix D, March 2017, 28.
    \38\ Id., 2.
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    To summarize, based on the EPA's reviews of the relevant monitoring 
network plans, certifications, quality assurance data, and 2018 TSA, we 
propose to find that the PM2.5 data collected at the Nogales 
Post Office monitoring site are suitable for determining whether the 
Nogales area has attained 2006 PM2.5 24-hour NAAQS based on 
the most recent certified data available in AQS.
3. Evaluation of Attainment
    Table 1 shows the calculated 24-hour PM2.5 design value 
at the Nogales Post Office monitoring site within the Nogales area for 
the 2018-2020 period.\39\ The data show that the 24-hour design value 
for the 2018-2020 period, 26 [mu]g/m\3\, was equal to or less than 35 
[mu]g/m\3\, the 2006 PM2.5 24-hour NAAQS; \40\ and, 
preliminary data for 2021 continue to show that the Nogales area is 
meeting the NAAQS.\41\ Consequently, based upon three years of 
complete, quality-assured and certified data from 2018-2020, the EPA 
proposes to determine that the Nogales area has attained and continues 
to attain the 2006 24-hour PM2.5 NAAQS.
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    \39\ We calculated the design value for the 2018-2020 period as 
the average of the annual 98th percentiles for each of the three 
years according to 40 CFR 50, Appendix N, section 4.5.
    \40\ AQS, Design Value Report, dated November 19, 2021.
    \41\ AQS, Combined Site Sample Values Report, dated November 19, 
2021.

      Table 1--Nogales Area 2020 Design Value for the 2006 PM2.5 24-Hour NAAQS With Annual 98th Percentile
                                                 Concentrations
                                                  [[mu]g/m\3\]
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                                                                  98th percentile
             Monitor               AQS site  ID  ------------------------------------------------    2018-2020
                                        No.            2018            2019            2020        design value
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Nogales Post Office.............     04-023-0004            21.8            24.7            32.2              26
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Source: AQS, Design Value Report, dated November 19, 2021.

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

    Under CAA section 107(d)(3)(E)(ii) and (v), the EPA must have fully 
approved the applicable SIP for the nonattainment area under CAA 
section 110(k) and the state containing such an area must have met all 
requirements applicable to the area under section 110 and part D. 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, as 
discussed in section II.B.2 of this proposal) 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.
    For example, CAA section 110(a)(2)(D) requires that SIPs contain 
certain measures to prevent sources in a state from significantly 
contributing to air quality problems in another state; these SIPs are 
often referred to as ``transport SIPs.'' Because the section 
110(a)(2)(D) requirements for transport SIPs are not linked to a 
particular nonattainment area's designation and classification, but 
apply regardless of the area's attainment status, these are not 
applicable requirements for the purpose of redesignation, under CAA 
section 107(d)(3)(E). This is consistent with the EPA's existing policy 
on applicability of the conformity SIP requirement for 
redesignations.\42\
---------------------------------------------------------------------------

    \42\ 75 FR 36023, 36026 (June 24, 2010) and citations within.
---------------------------------------------------------------------------

    The EPA may rely on prior SIP approvals in approving a 
redesignation request,\43\ and any additional measure or element we may 
approve in conjunction with our redesignation action.\44\
---------------------------------------------------------------------------

    \43\ Calcagni Memo, 3; Wall v. EPA, F.3d 426 (6th Cir. 2001); 
and Southwest Pennsylvania Growth Alliance v. Browner, 114 F.3d 984, 
989-990 (6th Cir. 1998).
    \44\ 68 FR 25418, 25426 (May 12, 2003) and citations within.

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[[Page 11669]]

1. State Implementation Plan Requirements Under Section 110
    The general SIP elements and requirements set forth in CAA section 
110 include, but are not limited to, the following: Submittal of a SIP 
that has been adopted by the state after reasonable public notice and 
hearing; provisions for establishment and operation of appropriate 
procedures needed to monitor ambient air quality; implementation of a 
source permitting program; provisions for the implementation of part C 
requirements for prevention of significant deterioration (PSD); 
provisions for the implementation of part D requirements for 
nonattainment new source review permit programs; provisions for air 
pollution modeling; and, provisions for public and local agency 
participation in planning and emissions control rule development.
    On numerous occasions, ADEQ 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. Relevant to this 
proposal, on November 5, 2012, the EPA approved SIP revisions submitted 
by the state of Arizona with respect to the requirements of CAA section 
110(a)(2) for the 2006 PM2.5 NAAQS.\45\
---------------------------------------------------------------------------

    \45\ 77 FR 66398. The EPA approved the submittals as satisfying 
most requirements of CAA section 110(a)(2), but disapproved the 
submittals with respect to sections 110(a)(2)(C), (D)(i)(II), 
(D)(ii), (J), and (K) because of a deficiency with respect to PSD 
requirements in Maricopa and Pima counties. We also partially 
disapproved the submittals with respect to 110(a)(2)(E)(ii), but 
this disapproval pertained only to Maricopa, Pima, and Pinal 
counties and thus has no relevance to the Nogales area.
---------------------------------------------------------------------------

    In conclusion, we find that there are no outstanding or disapproved 
applicable SIP submittals that prevent redesignation of the Nogales 
area for the 2006 24-hour PM2.5 standard. Therefore, we 
propose to conclude that the ADEQ has met all SIP requirements for the 
Nogales area that are applicable for purposes of redesignation under 
section 110 of the CAA.
2. State Implementation Plan Requirements Under Part D
    Subparts 1 and 4 of part D, title I of the CAA contain air quality 
planning requirements for PM2.5 nonattainment areas. Subpart 
1 contains general requirements for all nonattainment areas of any 
pollutant governed by a NAAQS, including PM2.5. The subpart 
1 requirements include, in relevant part, provisions for implementation 
of RACM, a demonstration of RFP, emissions inventories, a program for 
preconstruction review and permitting of new or modified major 
stationary sources, contingency measures, and transportation 
conformity.
    Subpart 4 contains specific planning and scheduling requirements 
for PM2.5 nonattainment areas. The requirements described in 
CAA section 189(a), (c), and (e) apply specifically to Moderate 
PM2.5 nonattainment areas and include the following: An 
approved permit program for construction of new or modified major 
stationary sources; provisions for RACM; an attainment demonstration; 
quantitative milestones demonstrating RFP toward attainment by the 
applicable attainment date; and, provisions to ensure that the control 
requirements applicable to major stationary sources of PM2.5 
also apply to major stationary sources of PM2.5 precursors, 
except where the Administrator has determined that such sources do not 
contribute significantly to PM2.5 levels that exceed the 
NAAQS in the area.
    As noted in section I.B of this proposal, in 2013 the EPA issued a 
clean data determination for the Nogales area, based on 2009-2011 data. 
As part of this determination, we found that the following CAA 
requirements in sections 172 and 189 would not apply to the Nogales 
area for so long as the area continued to attain the PM2.5 
standard or until the area was redesignated to attainment: An 
attainment demonstration, RACM, RFP, and contingency measures.
    Moreover, in the context of evaluating the area's eligibility for 
redesignation, there is a separate and additional justification for 
finding that requirements associated with attainment are not applicable 
for purposes of redesignation. Prior to and independent of the clean 
data policy, and in the context of redesignations specifically, the EPA 
has interpreted CAA SIP submittal requirements associated with 
attainment of the NAAQS (such as attainment and RFP demonstrations) as 
not being applicable for purposes of redesignation.\46\ Similarly, the 
Calcagni memo provides that requirements for RFP and other measures 
needed for attainment will not apply for redesignations because they 
have meaning and applicability only where areas do not meet the 
NAAQS.\47\ With respect to contingency measures, the EPA explained that 
the section 172(c)(9) contingency measure requirements are directed at 
ensuring RFP and attainment by the applicable date; consequently, these 
requirements no longer apply when an area has attained the standards 
and is eligible for redesignation. In addition, CAA section 175A(d) 
provides requirements for specific maintenance plan contingency 
provisions that effectively supersede the requirements of section 
172(c)(9) for these maintenance areas.
---------------------------------------------------------------------------

    \46\ General Preamble, 13564.
    \47\ Calcagni memo, 6.
---------------------------------------------------------------------------

    In sum, the EPA has concluded that the requirements associated with 
attainment do not apply for purposes of evaluating whether an area 
attaining the standards qualifies for redesignation. The EPA has 
enunciated this position since the General Preamble was published in 
1992, and it represents our interpretation of what constitutes 
applicable requirements under section 107(d)(3)(E). The courts have 
recognized the scope of the EPA's authority to interpret ``applicable 
requirements'' in the redesignation context.\48\
---------------------------------------------------------------------------

    \48\ The Seventh Circuit decision in Sierra Club v. EPA, 375 
F.3d 537 (7th Cir. 2004) (upholding the EPA's redesignation of the 
St. Louis metropolitan area to attainment) is one such example.
---------------------------------------------------------------------------

    The remaining applicable part D requirements for Moderate 
PM2.5 areas include the following: (1) An emissions 
inventory under section 172(c)(3); (2) a permit program for the 
construction and operation of new and modified major stationary sources 
of PM2.5 under sections 172(c)(5) and 189(a)(1)(A); (3) 
control requirements for major stationary sources of PM2.5 
precursors under section 189(e), except where the Administrator 
determines that such sources do not contribute significantly to 
PM2.5 levels that exceed the standards in the area; (4) 
requirements under section 172(c)(7) that meet the applicable 
provisions of section 110(a)(2); and, (5) provisions to ensure that 
federally supported or funded projects conform to the air quality 
planning goals in the applicable SIP under section 176(c). We discuss 
each of these requirements next.
a. Emissions Inventory
    Section 172(c)(3) of the CAA requires states to submit a 
comprehensive, accurate, current inventory of PM2.5 and

[[Page 11670]]

precursor pollutants for the baseline year from all sources within the 
nonattainment area. As noted earlier in section I.C, we approved the 
Nogales area emissions inventories under CAA section 172(c)(3) in 2015.
b. Permits for New and Modified Major Stationary Sources
    CAA sections 172(c)(5) and 189(a)(1)(A) require that states submit 
SIP revisions that establish certain requirements for new or modified 
major stationary sources in nonattainment areas, including provisions 
to ensure that major new sources or major modifications of existing 
sources of nonattainment pollutants incorporate the highest level of 
control (referred to as the lowest achievable emission rate (LAER)), 
and that increases in emissions from such stationary sources are offset 
to provide for RFP towards attainment in the nonattainment area. The 
major source threshold for Moderate PM2.5 nonattainment 
areas is 100 tons per year of PM2.5.\49\ The process for 
reviewing permit applications and issuing permits for new or modified 
stationary sources of air pollution is referred to as new source review 
(NSR). With respect to nonattainment pollutants in nonattainment areas, 
this process is referred to as nonattainment NSR (NNSR). Areas that are 
designated as attainment or unclassifiable for one or more NAAQS are 
required to submit SIP revisions that ensure that major new stationary 
sources or major modifications of existing stationary sources meet the 
federal requirements for PSD, including application of best available 
control technology for each applicable pollutant emitted in significant 
amounts, among other requirements.\50\
---------------------------------------------------------------------------

    \49\ CAA section 302(j).
    \50\ PSD requirements control the growth of new source emissions 
in areas designated as attainment or unclassifiable for a NAAQS.
---------------------------------------------------------------------------

    ADEQ has air permitting responsibilities in Santa Cruz County and 
the Nogales area. ADEQ has an EPA-approved NNSR program for 
PM2.5.\51\ With respect to sources subject to ADEQ's 
jurisdiction, EPA-approved regulations include rules for the review of 
applications for new or modified stationary sources. The EPA has not 
approved ADEQ regulations specifically meeting the NNSR requirements of 
CAA sections 172(c)(5) and 189(a)(1)(A). The EPA interprets section 
107(d)(3)(E)(v) of the CAA, however, such that final approval of an 
NNSR program is not a prerequisite to approving a state's redesignation 
request. The EPA has determined in past redesignations that an NNSR 
program does not have to be approved prior to redesignation provided 
that the area demonstrates maintenance of the standards without part D 
NNSR requirements in effect.\52\
---------------------------------------------------------------------------

    \51\ 80 FR 67319 (November 2, 2015); 83 FR 19631 (May 4, 2018); 
86 FR 31927 (June 16, 2021).
    \52\ See, generally, the Nichols memo; see also, the more 
detailed explanations in the following redesignation rulemakings: 
Detroit, Michigan (60 FR 12467-12468, March 7, 1996); Cleveland-
Akron-Lorrain, Ohio (61 FR 20458, 20469-20470, May 7, 1996); 
Louisville, Kentucky (66 FR 53665, 53669, October 23, 2001); Grand 
Rapids, Michigan (61 FR 31831, 31836-31837, June 21, 1996); and San 
Joaquin Valley, California (73 FR 22307, 22313, April 25, 2008 and 
73 FR 66759, 66766-66767, November 12, 2008).
---------------------------------------------------------------------------

    The demonstration of maintenance of the PM2.5 NAAQS in 
the Nogales Maintenance Plan relies on projections of future emissions 
based on various growth factors. For the types of stationary sources 
that are subject to ADEQ jurisdiction, future emissions are projected 
based on either the operational history of the facility or population 
growth projections and do not take credit for future control technology 
requirements, such as LAER, or for imposition of emissions offsets.\53\ 
Thus, we find that the maintenance demonstration for the Nogales area 
does not rely on an NNSR program, and that the area need not have a 
fully-approved NNSR program prior to approval of the PM2.5 
redesignation request for the area.
---------------------------------------------------------------------------

    \53\ In Section III.D of this proposal, we discuss the point 
source emissions projections with respect to the Valencia Power 
Plant, the sole operating point source in the Nogales area and 
include perquisite citations to the Plan.
---------------------------------------------------------------------------

    If we finalize the redesignation action as proposed herein, the 
requirements of the PSD program will apply with respect to 
PM2.5.\54\ With respect to the PSD requirements, ADEQ has an 
EPA-approved PSD program under CAA sections 160 through 165 of the CAA, 
except for greenhouse gases (GHGs), and the EPA has delegated to ADEQ 
the authority to administer the federal PSD program for GHGs under 40 
CFR 52.21.\55\ These programs will apply to PM2.5 emissions 
from new major sources and major modifications upon redesignation of 
the area to attainment. Thus, new major sources and major modifications 
to existing major sources with significant PM2.5 emissions, 
as defined under 40 CFR 51.166 and 52.21, will be required to obtain a 
PSD permit.
---------------------------------------------------------------------------

    \54\ With respect to other criteria pollutants, PSD requirements 
already apply in the Nogales area.
    \55\ 40 CFR 52.144.
---------------------------------------------------------------------------

    We conclude that the Arizona SIP adequately meets the requirements 
of section 172(c)(5) and 189(a)(1)(A) for purposes of redesignation of 
the Nogales area.
c. Control Requirements for PM2.5 Precursors
    Section 189(e) of the CAA provides that control requirements for 
major stationary sources of direct PM10 (including 
PM2.5) also apply to PM precursors from those sources, 
except where the EPA determines that major stationary sources of such 
precursors do not contribute significantly to PM10 levels 
that exceed the standards in the area. The CAA does not explicitly 
address whether it would be appropriate to include a potential 
exemption from precursor controls for all source categories under 
certain circumstances. In implementing subpart 4 for PM10, 
the EPA has allowed states to determine that a precursor was 
``insignificant'' where the state could show in its attainment plan 
that it would attain the NAAQS expeditiously without adoption of 
emissions reduction measures aimed at that precursor. This approach was 
upheld in Association of Irritated Residents v. EPA.\56\ Subsequently, 
the EPA included this approach within the PM2.5 SIP 
Requirements Rule.\57\ A state may develop its attainment plan and 
adopt RACM that target and control only those precursors that are 
necessary for the purpose of timely attainment.\58\
---------------------------------------------------------------------------

    \56\ 423 F.3d 989 (9th Cir. 2005).
    \57\ See generally 81 FR 58017-58026.
    \58\ Id at 58020.
---------------------------------------------------------------------------

    Therefore, because the section 189(e) requirement is primarily 
actionable in the context of addressing precursors in an attainment 
plan, a precursor exemption analysis under section 189(e) and the EPA's 
implementing regulations is not an applicable requirement that needs to 
be fully approved in the context of a redesignation under CAA section 
107(d)(3)(E)(ii). As discussed earlier in our proposal, for areas that 
are attaining the standards, the EPA does not interpret the 
requirements of subpart 1 and subpart 4 that are associated with 
attainment to be applicable requirements for the purpose of 
redesignating the area to attainment.
    As previously noted, the EPA determined in 2013 and more recently 
in 2017 that the Nogales area had attained the 24-hour PM2.5 
NAAQS.\59\ Therefore, no additional controls of any pollutant, 
including any PM2.5 precursor, are necessary to bring the 
area into attainment. In section III.A of this proposal, we propose to 
find that the area continues to attain the NAAQS. In section III.C, the 
EPA proposes to determine that the Nogales area has

[[Page 11671]]

attained the standard due to permanent and enforceable emissions 
reductions. Also, as presented in section III.D, we propose to find 
that the Nogales Maintenance Plan demonstrates continued maintenance of 
the 24-hour PM2.5 NAAQS through 2032. Taken together, these 
factors support our conclusion that PM2.5 precursors are 
controlled adequately.
---------------------------------------------------------------------------

    \59\ Also, the Nogales area has recorded ambient air quality 
data under the PM2.5 NAAQS continuously since 2009; refer 
to Nogales Maintenance Plan, 15, Figure 6.
---------------------------------------------------------------------------

d. Compliance With Section 110(a)(2)
    Section 172(c)(7) of the CAA requires the SIP to meet the 
applicable provisions of section 110(a)(2). As described in section 
III.B.1 of this proposal, we conclude that the Arizona SIP meets the 
requirements of section 110(a)(2) that are applicable for purposes of 
this redesignation.
e. General and Transportation Conformity Requirements
    Under section 176(c) of the CAA, states are required to revise 
their SIPs to establish criteria and procedures to ensure that 
federally supported or funded projects in nonattainment areas and 
former nonattainment areas subject to a maintenance plan (referred to 
as ``maintenance areas'') conform to the air quality planning goals in 
the applicable SIP. Section 176(c) further provides that state 
conformity provisions must be consistent with federal conformity 
regulations that the CAA requires the EPA to promulgate. The EPA's 
conformity regulations are codified at 40 CFR part 93, subpart A 
(referred to herein as ``transportation conformity'') and subpart B 
(referred to herein as ``general conformity''). Transportation 
conformity applies to transportation plans, programs, and projects 
developed, funded, and approved under title 23 U.S.C. or the Federal 
Transit Laws (49 U.S.C. Chapter 53), and general conformity applies to 
all other federally supported or funded projects. SIP revisions 
intended to address the conformity requirements are referred to herein 
as ``conformity SIPs.'' In 2005, Congress amended section 176(c) of the 
CAA. Under the amended conformity statutory provisions, states are no 
longer required to submit conformity SIPs for general conformity, and 
the conformity SIP requirements for transportation conformity have been 
reduced to include only those relating to consultation, enforcement, 
and enforceability.\60\
---------------------------------------------------------------------------

    \60\ CAA section 176(c)(4)(E).
---------------------------------------------------------------------------

    We have not approved a transportation conformity SIP for the 
Nogales area. We consider it reasonable, however, to interpret the 
conformity SIP requirements as not applying for purposes of a 
redesignation request under section 107(d) because the conformity SIP 
requirement continues to apply post-redesignation (conformity applies 
in maintenance areas as well as nonattainment areas) and because the 
federal conformity rules (set forth in 40 CFR part 93, subpart A and 
subpart B) apply where the EPA has not approved a state's rule.\61\
---------------------------------------------------------------------------

    \61\ See Wall v. EPA, 265 F.3d 426 (6th Cir. 2001), upholding 
this interpretation. See also, 60 FR 62748 (December 7, 1995).
---------------------------------------------------------------------------

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, under section 
107(d)(3)(E)(iii) of the CAA, the EPA is required to determine that a 
nonattainment area's 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 rates (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.\62\
---------------------------------------------------------------------------

    \62\ Calcagni memo, 4.
---------------------------------------------------------------------------

    Within the Nogales area, federal programs have been the primary 
measures contributing permanent and enforceable emissions reductions 
leading to attainment of the NAAQS. Increasingly stringent federal 
motor vehicle standards for cars and trucks, federal requirements for 
lower sulfur content in diesel fuel, and capital improvements to ports 
of entry (POE), and expansion of the Mariposa POE have contributed to 
reducing ambient PM2.5 concentrations since the Nogales area 
was classified as nonattainment in 2009.
    The federal motor vehicle program and federal fuel standards for 
sulfur content in diesel have contributed to attainment of the 
PM2.5 NAAQS in the Nogales area by reducing emissions of 
direct PM2.5 and PM2.5 precursors, such as 
SO2 and NOX.\63\ Federal tier 2 and 3 motor 
vehicle standards implemented from 2004 to 2014 helped to reduce on-
road mobile source PM2.5 emissions in the Nogales area by 53 
percent, from 2008 to 2017.\64\ Federal sulfur content standards for 
diesel fuel were implemented in conjunction with the federal motor 
vehicle program standards. Lower sulfur content fuel has reduced 
SO2 emissions and allowed pollution control equipment to 
operate more effectively to reduce emissions of other pollutants as 
well. Taken together these federal programs contributed to 
NOX emission reductions of 56 percent in the Nogales area, 
in addition to the PM2.5 emissions reduction discussed 
above.\65\
---------------------------------------------------------------------------

    \63\ Nogales Maintenance Plan, 22-24.
    \64\ Nogales Maintenance Plan, 22.
    \65\ Nogales Maintenance Plan, 24.
---------------------------------------------------------------------------

    Beginning in 2010, the Mariposa POE, located 1.7 miles west of the 
Nogales Post Office monitor, underwent a series of capital improvements 
to expand this POE, to divert truck traffic from the DeConcini POE 
located in downtown Nogales, and to facilitate faster vehicle 
inspections resulting in less truck idling and faster throughput at the 
Mariposa POE.\66\ These capital improvements included significant 
increases in the number of inspection facilities for both commercial 
trucks and motor vehicles. These POE capital improvements contributed 
to reduced PM2.5 emissions associated with truck crossings 
at the U.S./Mexico border.\67\
---------------------------------------------------------------------------

    \66\ Nogales Maintenance Plan, 19-22.
    \67\ Nogales Maintenance Plan, 21.
---------------------------------------------------------------------------

    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 Nogales area is not the result of a local economic 
downturn, temporary emissions reductions, or unusual or extreme weather 
patterns. Our conclusion is based on the observation that the 
PM2.5 design value for the Nogales area has been below 35 
[mu]g/m\3\, the level of the 2006 PM2.5 24-hour NAAQS, since 
2009 and has been consistently between 25-30 [mu]g/m\3\ from 2011 to 
2020.\68\ In sum, ambient PM2.5 concentrations in the 
Nogales area have been consistently below the NAAQS for a lengthy 
period of time, and have not been subject to large swings and disparate 
observations that a sudden facility closure or an extreme weather 
pattern might produce.
---------------------------------------------------------------------------

    \68\ Id. at 15, Figure 6.
---------------------------------------------------------------------------

    In conclusion, we find that the improvement in ambient air quality 
in the Nogales area is due to permanent and enforceable reductions in 
emissions of direct PM2.5 and PM2.5 precursors, 
resulting from control measures such as (1) implementation of the 
federal motor vehicle program and diesel fuel

[[Page 11672]]

standards; and (2) facility capital expansions and processing 
improvements leading to reduced motor vehicle idling times and faster 
vehicle throughput at federal POEs. 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

    Under section 107(d)(3)(E)(iv) of the CAA, to approve a 
redesignation to attainment, the EPA must fully approve a maintenance 
plan for the area as meeting the requirements of section 175A of the 
CAA. Section 175A specifies the required elements of a maintenance plan 
for areas seeking redesignation from nonattainment to attainment. Under 
section 175A, the plan must demonstrate continued attainment of the 
applicable NAAQS for at least 10 years after the EPA approves a 
redesignation to attainment. Eight years after redesignation, a state 
must submit a revised maintenance plan that demonstrates continued 
attainment for the subsequent 10-year period following the initial 10-
year maintenance period. To address the possibility of future NAAQS 
violations, the maintenance plan must contain such contingency 
provisions as the EPA deems necessary to promptly correct any violation 
of the NAAQS that occurs after redesignation of the area. The Calcagni 
memo provides further guidance on the content of a maintenance plan, 
explaining that a maintenance plan should include an attainment 
emissions inventory, maintenance demonstration, monitoring and 
verification of continued attainment, and a contingency plan. Based on 
our review and evaluation of the Nogales Maintenance Plan, we are 
proposing to approve the Plan as meeting the requirements of CAA 
section 175A.
1. Attainment Inventory
    A maintenance plan for the PM2.5 NAAQS should include an 
``attainment emissions inventory'' of direct PM2.5 emissions 
and PM2.5 precursors in the area to identify a level of 
emissions sufficient to attain the 24-hour PM2.5 NAAQS.\69\ 
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 EPA has provided guidance for 
developing PM emissions inventories in ``Emissions Inventory Guidance 
for Implementation of Ozone and Particulate Matter National Ambient Air 
Quality Standards (NAAQS) and Regional Haze Regulations'' (July 2017).
---------------------------------------------------------------------------

    \69\ Calcagni Memo, 8-9.
---------------------------------------------------------------------------

    The Nogales Maintenance Plan's demonstration that the area attained 
the standard is based on monitoring data from 2017-2019, the three most 
recent years with certified air quality data available at the time of 
adoption and submittal of the Plan.\70\ Consistent with this timeframe, 
ADEQ selected 2017 for the attainment emissions inventory. Appendix B 
of the Nogales Maintenance Plan is a technical support document (TSD) 
detailing the emissions data and development of the emissions inventory 
for the Plan.\71\
---------------------------------------------------------------------------

    \70\ The Plan was submitted to the EPA on April 13, 2021, prior 
to certification of 2020 monitoring data on April 26, 2021.
    \71\ Nogales Maintenance Plan, Appendix B--``Emissions Inventory 
Technical Support Document for the 2006 Nogales PM2.5 
Maintenance Area''.
---------------------------------------------------------------------------

    The attainment emissions inventory in the Nogales Maintenance Plan 
includes PM2.5, NOX, SOX, VOC, and 
NH3 estimates from all relevant source categories, which the 
Plan divides among point, nonpoint, on-road mobile, non-road mobile, 
and fugitive road dust.\72\ ADEQ developed the emissions estimates for 
each source type using appropriate sources and methods.\73\ Point 
source emissions were based on ADEQ's State and Local Emissions 
Inventory System (SLEIS) database and facility permit data.\74\ Non-
point source emissions were based on the county-level data in the EPA's 
2014 National Emissions Inventory (NEI) projected to 2017 and allocated 
to the smaller nonattainment area.\75\ On-road mobile source emissions 
were derived from running the MOVES2014b \76\ emissions factor model 
with the appropriate vehicle population and vehicle miles traveled 
data.\77\ Non-road mobile source emissions were derived from the same 
MOVES2014b model and county-level data, again allocated to the smaller 
nonattainment area.\78\ Fugitive road dust emissions, from paved and 
unpaved roads, were derived from the county-wide 2014 NEI estimates, 
projected to 2017 using Arizona Department of Transportation (ADOT) 
vehicle miles traveled (VMT) estimates, and allocated to the Nogales 
area using population share.\79\
---------------------------------------------------------------------------

    \72\ Nogales Maintenance Plan, 38, section 5.1 and Table 5-1.
    \73\ TSD, 25, Table 3-1.
    \74\ Id. at 25, Section 3.1.
    \75\ Id. at 27, Section 3.3.
    \76\ EPA's Motor Vehicle Emission Simulator (MOVES) is a state-
of-the-science emission modeling system.
    \77\ Id. at 25, Section 3.2.1.
    \78\ Id. at 25, Section 3.2.2.
    \79\ Id. at 27, Section 3.2.3.
---------------------------------------------------------------------------

    Table 2 presents a summary of actual annual PM2.5 
emissions estimates for the 2017 attainment year for sources in the 
Nogales area.\80\ Based on the emissions estimates for 2017 in Table 2, 
combined fugitive road dust (unpaved and paved roads) accounts for 
approximately 59 percent of total PM2.5 emissions in the 
area. The next highest source category is non-point sources at 30 
percent.
---------------------------------------------------------------------------

    \80\ As we discuss in section III.D.2 of this proposal, the 
winter day emissions inventories for the maintenance demonstration 
include winter daily emissions estimates and daily average emissions 
estimates scaled from the annual emissions estimates.

        Table 2--2017 Nogales Area PM2.5 and Precursor Compound Emissions Inventories by Source Category
                                                 [Tons per year]
----------------------------------------------------------------------------------------------------------------
            Category                   PM2.5            NOX             SOX             VOC             NH3
----------------------------------------------------------------------------------------------------------------
Point Sources...................            0.17             7.8           0.054           0.066  ..............
Non-Point Sources...............            57.0            39.0             2.4           432.0             3.7
On-Road Mobile Emissions........            10.2           414.4             1.8           245.1             6.0
Non-Road Mobile Emissions.......             9.3           123.2            0.48            77.0           0.188
Unpaved Road Fugitive Dust......            96.2  ..............  ..............  ..............  ..............
Paved Road Fugitive Dust........            13.6  ..............  ..............  ..............  ..............
                                 -------------------------------------------------------------------------------
    Totals......................           186.5           584.4             4.7           754.2             9.9
----------------------------------------------------------------------------------------------------------------
Source: TSD, 41, Table 4-9. Numbers may differ slightly due to rounding.

[[Page 11673]]

    Based on our review of the attainment emissions inventory in the 
Nogales Maintenance Plan, including the supporting information in the 
TSD, we find that the attainment year inventory is comprehensive, the 
methods and assumptions used by ADEQ to develop the inventories are 
reasonable, and the 2017 inventory reasonably estimates actual 
PM2.5 emissions in that year. We also find that the 2017 
emissions inventory is appropriate for use as the attainment inventory 
for the Nogales Maintenance Plan because the year 2017 is within the 
2017-2019 period during which the area was attaining the 24-hour 
PM2.5 NAAQS.\81\
---------------------------------------------------------------------------

    \81\ Nogales Maintenance Plan, 15, Table 2-2.
---------------------------------------------------------------------------

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.\82\ Assumptions concerning emissions rates in maintenance 
demonstrations should generally reflect permanent, enforceable 
measures.\83\ 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.\84\
---------------------------------------------------------------------------

    \82\ Calcagni memo, 9-11.
    \83\ Calcagni memo, 9.
    \84\ Id. at 4. See also, Memorandum dated November 30, 1993, 
from Kent D. Berry, Acting Director, Air Quality Management 
Division, Subject: Use of Actual Emissions in Maintenance 
Demonstrations for Ozone and Carbon Monoxide (CO) Nonattainment 
Areas.
---------------------------------------------------------------------------

    To demonstrate maintenance of the 2006 24-hour PM2.5 
NAAQS for ten years from redesignation, ADEQ projected annual and 
winter emissions inventories for PM2.5, NOX, 
SOX, VOC, and NH3 for 2026, the interim 
maintenance year, and 2032, the ten-year maintenance demonstration 
year.\85\ Given that almost all recorded exceedances of the 24-hour 
PM2.5 NAAQS in the recent past have occurred during the 
winter months of December and January,\86\ ADEQ based its maintenance 
demonstration on a winter day emissions inventories analysis. 
Furthermore, because the 24-hour PM2.5 NAAQS is a daily 
standard it is appropriate for the maintenance demonstration to be in 
the form of a daily emissions inventory comparison.
---------------------------------------------------------------------------

    \85\ Nogales Maintenance Plan, section 5 and TSD.
    \86\ TSD, 20-22, Section 2.3 and Table 2-1.
---------------------------------------------------------------------------

a. Annual Emissions Inventories Comparisons
    Using the 2017 emissions inventories as a baseline and growth 
factors described in the TSD, ADEQ projected emissions inventories for 
2026 and 2032. These projections were based primarily on Arizona's 
forecasts of population and VMT or in some cases, information 
particular to a given source or source category. To estimate mobile 
source emissions, ADEQ used an EPA on-road emissions model (i.e., 
MOVES2014b).\87\ Table 3 summarizes ADEQ's 2017 attainment year 
PM2.5 emissions and projected PM2.5 emission 
levels for 2026 and 2032.
---------------------------------------------------------------------------

    \87\ The EPA announced the release of a new version of MOVES in 
the Federal Register on January 7, 2021. 86 FR 1106. In that 
document, we explained that state and local agencies that had 
already completed significant work on a SIP with a version of 
MOVES2014 could continue to rely on the earlier version of MOVES. 
Id. at 1108. As of January 7, 2021, ADEQ had already released a 
draft of the Nogales Maintenance Plan for public review. Therefore, 
we consider the Plan's reliance on MOVES2014b to be appropriate.

            Table 3--2017, 2026, and 2032 Nogales Area PM2.5 Emissions Inventories by Source Category
                                                 [Tons per year]
----------------------------------------------------------------------------------------------------------------
                                                                                                     Projected
                    Category                           2017            2026            2032         change from
                                                                                                   2017 to 2032
----------------------------------------------------------------------------------------------------------------
Point Sources...................................            0.17            1.23            1.23           +1.06
Non-Point Sources...............................            57.0            57.9            57.6            +0.6
On-Road Mobile Emissions........................            10.2             2.2             1.4            -8.8
Non-Road Mobile Emissions.......................             9.3             6.0             5.2            -4.1
Unpaved Road Fugitive Dust......................            96.2            98.8           100.6            +4.4
Paved Road Fugitive Dust........................            13.6            14.0            14.2            +0.6
                                                 ---------------------------------------------------------------
    Totals......................................           186.5           180.1           180.2            -6.3
----------------------------------------------------------------------------------------------------------------
Source: TSD 41, Table 4-9; TSD 60-63, Tables 6-4 through 6-8. Numbers may differ slightly due to rounding.

    Despite expected population growth in the Nogales area,\88\ the 
Plan's projected PM2.5 annual emissions through 2032 are 
lower than the 2017 attainment year inventory emissions. The decrease 
in annual PM2.5 emissions from 2017 to 2032 most likely 
reflects continued implementation of the federal motor vehicle program, 
cleaner motor vehicle fuels, and ongoing vehicle fleet turnover, 
whereby newer and cleaner vehicles are substituted for older more 
polluting vehicles as they are retired. A comparison of precursor 
compound totals from 2017 to 2032 in Table 4 suggests a similar 
conclusion. VOC and NOX emissions are projected to decrease 
due to large reductions in the on-road mobile source category.\89\ 
SOX emissions are projected to increase, largely due to 
emissions in the point source category from the Valencia Power Plant 
(VPP), an electrical generation facility located north of the City of 
Nogales.\90\ To address this projected increase in SOX 
emissions in the annual and winter daily inventories, ADEQ provided 
additional analyses to demonstrate that VPP operations are unlikely to 
cause or contribute to future violations of the PM2.5 NAAQS. 
We review the VPP analyses before proceeding to our review of the 
winter daily emissions inventories.
---------------------------------------------------------------------------

    \88\ Nogales Maintenance Plan, 8, Table 1-5.
    \89\ Id. at 39, Table 5-2.
    \90\ Nogales Maintenance Plan Section 5.2.3; TSD Section 5.1; 
TSD-Appendix D. TSD 19, Figure 2-2 provides a map showing the 
location of the Valencia Power Plant in relation to the City of 
Nogales and the Nogales Post Office air quality monitoring station.

[[Page 11674]]

    Table 4--2017, 2026, and 2032 Nogales Area Emissions Inventories for PM2.5 and Precursor Pollutant Totals
                                                 [Tons per year]
----------------------------------------------------------------------------------------------------------------
                                                                                                     Projected
                    Pollutant                          2017            2026            2032         change from
                                                                                                   2017 to 2032
----------------------------------------------------------------------------------------------------------------
PM2.5...........................................           186.5           179.9           180.2            -6.3
NOX.............................................           584.4           307.4           250.6          -333.8
SOX.............................................             4.7             9.8             9.8            +5.1
VOC.............................................           754.3           665.8           650.0          -104.3
NH3.............................................             9.8             8.3             7.9            -1.9
----------------------------------------------------------------------------------------------------------------
Source: Plan 39, Tables 5-2 and 5-3. Numbers may differ slightly due to rounding.

    As noted, the EPA generally recommends use of permitted ``maximum 
potential to emit'' (``PTE'') levels or maximum historical emissions in 
maintenance demonstrations, unless a state presents evidence that such 
an assumption is unrealistic. ADEQ examined past VPP emissions levels 
to determine if the facility has approached its PTE. Facility records 
from 2000 to 2018 show that VPP has operated at levels significantly 
below its PTE.\91\ For instance, from 2000-2018, the VPP's highest 
annual particulate matter emissions was 1.23 tons per year (tpy) in 
2001 compared to its PM2.5 PTE of 45.52 tpy.\92\ Emissions 
levels from VPP have been even lower since 2014, due to a reduction in 
operating hours that resulted from improvements to transmission lines 
in the area.\93\ Given that VPP's 2001 emissions represent the highest 
level of facility emissions since 2000, ADEQ used this data set as the 
basis for projecting conservative annual emissions estimates of direct 
PM2.5 and PM2.5 precursors for VPP.
---------------------------------------------------------------------------

    \91\ Id. at 44, Table 5-4.
    \92\ Id. at Tables 5-3 and 5-4.
    \93\ Id. at 44.
---------------------------------------------------------------------------

    Also, because VPP can legally emit at its PTE, ADEQ conducted an 
analysis to determine the ambient air quality effects for direct 
PM2.5 in the Nogales area if VPP were to operate at PTE 
levels.\94\ VPP emissions of NOX and SOX are well 
below the Modeled Emission Rates for Precursors recommended in EPA 
guidance, and so we would not be expect them to cause or contribute to 
a violation of the PM2.5 NAAQS.\95\ ADEQ used AERSCREEN, an 
EPA screening-level air quality model to estimate VPP's worst case 24-
hour PM2.5 concentration when operating at PTE for direct 
PM2.5 emissions. AERSCREEN \96\ provides conservatively high 
concentration estimates by using worst case meteorology from among a 
range of wind speeds, degrees of cloud cover, temperatures, and other 
meteorological parameters. ADEQ post-processed AERSCEEN model output to 
exclude locations inside the facility boundary because they are not 
considered ambient air subject to the NAAQS. The analysis covered 
distances out to 10 kilometers; the highest concentrations were near 
the facility boundary, decreasing with distance from the boundary. 
ADEQ's analysis estimated that the highest ground level ambient 
PM2.5 concentration that would result from VPP operating at 
its PTE, including background PM2.5 concentrations, would be 
30.9 [micro]g/m\3\, which is below the 24-hour PM2.5 NAAQS 
of 35 [micro]g/m\3\.\97\
---------------------------------------------------------------------------

    \94\ TSD-Appendix D: Valencia AERSCREEN Modeling Overview 
Technical Memo, from Kamran Khan, ADEQ, to Scott Bohning, EPA-Region 
IX, December 19, 2018.
    \95\ A Modeled Emission Rate for Precursors (MERP) is the 
precursor emission rate that is likely to cause an impact that may 
cause or contribute to a NAAQS violation. The VPP PTE emissions of 
240 tpy NOX and 200 tpy SOX are far below the 
MERP levels for annual impacts for the southwestern U.S., roughly 
11,000 tpy for each; also, VPP PTE emissions are also far below the 
MERPs for 24-hour impacts (i.e., 6514 tpy for NOX and 
1508 tpy for SOX). ``Guidance on the Development of 
Modeled Emission Rates for Precursors (MERPs) as a Tier 1 
Demonstration Tool for Ozone and PM2.5 under the PSD 
Permitting Program,'' EPA 454/R-19-003. U.S. Environmental 
Protection Agency, Office of Air Quality Planning and Standards, 
April 2019, available at https://www.epa.gov/scram/clean-air-act-permit-modeling-guidance.
    \96\ EPA, 2011. ``AERSCREEN Released as the EPA Recommended 
Screening Model''. Memorandum dated April 11, 2011, Office of Air 
Quality Planning and Standards, Research Triangle Park, NC. 
Available at web page https://www.epa.gov/scram/air-quality-dispersion-modeling-screening-models#aerscreen.
    \97\ TSD, 43 and TSD-Appendix D.
---------------------------------------------------------------------------

    In addition to the AERSCREEN analysis, ADEQ examined the Nogales 
area meteorological data and wind patterns and determined that 
prevailing winds blow from south to north and that in cold weather with 
stagnant wind conditions, cold air masses move south to north.\98\ 
Given that VPP is well north of the Nogales Post Office monitor, usual 
Nogales wind patterns and air movement are likely to move VPP emissions 
away from the monitor and the urbanized area in the southern portion of 
the nonattainment area. Furthermore, peak electrical power consumption 
in the desert southwestern U.S. is during the summer months, making 
this the most likely period VPP is to be operational, whereas the 
winter months have the highest PM2.5 concentrations in the 
Nogales area.\99\
---------------------------------------------------------------------------

    \98\ TSD, 18, 19; Figures 2-1 and 2-2, respectively.
    \99\ Id. at 44.
---------------------------------------------------------------------------

    To summarize, as a conservative estimate of annual emissions levels 
at VPP, ADEQ utilized 2001 emissions data, the highest historical 
emissions levels in the 2000-2018 period. In addition, ADEQ estimated 
the worst case 24-hour PM2.5 concentration for VPP and 
determined that at PTE levels the facility's PM2.5 emissions 
are unlikely to cause or contribute to a violation of the 
PM2.5 NAAQS. This conclusion is further buttressed by 
prevailing wind direction and meteorological data for the Nogales area.
b. Winter Daily Emissions Inventories Comparisons
    In determining the need for winter daily emissions inventories as a 
basis for an attainment year (2017) to maintenance year (2032) 
comparison, ADEQ reviewed the 2014-2016 ambient air quality data sets. 
ADEQ found the ambient PM2.5 concentrations rose as 
temperature dropped with the onset of the winter season, November 
through January.\100\ December had the highest ambient PM2.5 
concentrations and concentrations rose as ambient temperatures dropped, 
particularly on days where the daily low temperature was less than 
40[deg] F. Given the data, ADEQ selected November-January as the 
Nogales area winter season.
---------------------------------------------------------------------------

    \100\ TSD, 64, Section 7.1 and Appendices B & C.
---------------------------------------------------------------------------

    With a few exceptions, the winter daily emissions inventories are 
based on the annual emission inventories.\101\ More precisely, most 
winter daily source category emissions estimates are average daily 
emissions estimates

[[Page 11675]]

(annual emissions estimates divided by 365 days per year), except for 
the seasonal calculations for residential fuel combustion (RFC). The 
annual RFC emissions estimate was allocated to the 92-day November 
through January winter season. The winter daily emissions estimates for 
VPP were not based on winter operations, but were conservative in that 
all estimated annual VPP emissions were assigned to the 92-day winter 
season. The 2017 daily emissions estimate was based on 2013-2018 VPP 
operational data. The projected 2026 and 2032 daily emissions estimates 
were conservative estimates based on 2013-2018 data and operational 
maximums from 2013.\102\ Then, ADEQ compared the ``winter daily'' 
projected 2026 and 2032 PM2.5 estimate for VPP (i.e., 1.8 
tpy or 44 pounds per day) with the historical 2001 high 
PM2.5 value (i.e., 1.2 tpy), and found it to be a relatively 
more conservative estimate.\103\
---------------------------------------------------------------------------

    \101\ Id. at 64-66, Section 7.2.
    \102\ ADEQ used 0.0000964 ton of PM per megawatt hour (i.e., 
0.1928 pounds of PM per megawatt hour) as an emissions level and a 
gross daily load of 228 megawatt hours per day as an activity level, 
both values representing the highest operational data from 2013-
2018. TSD, 65-66, Equation 7-2, within Section 7.2.1.
    \103\ TSD, 66. ADEQ calculated 1.8 tpy by multiplying 44 pounds 
per day by 83 days; 83 days are the maximum number of VPP operating 
days in the 2013-2018 period. In generating its 2032 projected VPP 
emissions, ADEQ is assuming that all 83 operational days are 
occuring during the winter season at the facility's highest recent 
rate; hence, their assertion that this is a conservative estimate of 
VPP emissions, given that VPP is more likely to be operational 
during the summer months during peak periods of energy demand.

            Table 5--2017, 2026, and 2032 Nogales Area PM2.5 Emissions Inventories by Source Category
                                             [Pounds per winter day]
----------------------------------------------------------------------------------------------------------------
                                                                                                     Projected
                    Category                           2017            2026            2032         change from
                                                                                                   2017 to 2032
----------------------------------------------------------------------------------------------------------------
Point Sources...................................            13.8            44.0            44.0           +30.2
Non-Point Sources...............................           164.0           181.9           190.9           +26.9
Residential Fuel Consumption....................           561.0           500.0           463.0           -98.0
On-Road Mobile Emissions........................            56.3            12.0             8.2           -48.1
Non-Road Mobile Emissions.......................            51.2            32.7            28.5           -22.7
Unpaved Road Fugitive Dust......................           527.2           541.5           551.0           +23.8
Paved Road Fugitive Dust........................            74.5            76.5            77.8            +3.3
                                                 ---------------------------------------------------------------
    Totals......................................         1,448.0         1,388.0         1,363.0           -84.6
----------------------------------------------------------------------------------------------------------------
Source: TSD, 67-70, Tables 7-2 and 7-4. Numbers may differ slightly due to rounding.

    A review of the total daily PM2.5 emissions in Table 5 
shows that overall emissions are expected to decrease from 2017 to 
2032. Like the annual emissions inventories estimates, mobile source 
emissions show the largest decreases and offset smaller increases in 
fugitive dust. RFC emissions are projected to decrease because of 
households switching to cleaner burning fuel sources over time.\104\
---------------------------------------------------------------------------

    \104\ TSD, 31, 32, 64. Section 3.3.2.2 describes how the annual 
RFC per capita emissions factor was generated and applied to get an 
annual RFC emissions estimate. This annual estimate was then 
converted to a winter daily missions estimate by dividing the annual 
emissions estimate by the number of winter days from November 
through January, 92 days.

       Table 6--2017, 2026, and 2032 Nogales Area Emissions Inventories for PM2.5 and Precursor Pollutants
                                             [Pounds per winter day]
----------------------------------------------------------------------------------------------------------------
                                                                                                     Projected
                    Pollutant                          2017            2026            2032         change from
                                                                                                   2017 to 2032
----------------------------------------------------------------------------------------------------------------
PM2.5...........................................           1,448           1,388           1,363             -85
NOX.............................................           3,821           2,882           2,594          -1,227
SOX.............................................              45              82              83             +38
VOC.............................................           4,672           4,172           4,069            -603
NH3.............................................             105              93              89             -16
----------------------------------------------------------------------------------------------------------------
Source: TSD 67-70, Tables 7-2 and 7-3. Numbers may differ slightly due to rounding.

    A review of Table 6 shows that PM2.5 and all precursor 
compound emissions are decreasing from 2017 to 2032, except for 
SOX emissions. SOX emissions are predicted to 
increase by 38 pounds per day over this timeframe due to increases in 
projected emissions from VPP, the only point source in the Nogales 
area.\105\ As discussed, the projected 2032 daily VPP emissions 
estimates are very conservative when compared to past historical 
operations data, in terms of both magnitude and seasonal intensity, 
i.e., assuming all facility emissions occur during the winter season. 
Also, ADEQ has examined the effect on ambient PM2.5 
concentrations if VPP emitted PM2.5 at PTE levels and 
determined that the facility's direct PM2.5 emissions are 
unlikely to cause a violation of the 24-hour PM2.5 NAAQS, 
even at such high and historically unachieved emissions levels. Lastly, 
the Nogales area meteorology and wind pattern make it unlikely that VPP 
emissions would have a significant effect on ambient PM2.5 
concentrations at the Nogales Post Office monitor.
---------------------------------------------------------------------------

    \105\ Nogales Maintenance Plan, 43, Table 5-6.
---------------------------------------------------------------------------

c. EPA Evaluation and Conclusion
    Based on our review, we find that ADEQ used reasonable methods, 
growth factors, and assumptions to project direct PM2.5 and 
precursor compound emissions to 2026 and 2032. ADEQ's emissions 
inventory projections show that future emissions through 2032 will be 
below estimated actual emissions in

[[Page 11676]]

2017, the attainment year, for PM2.5 and all relevant 
precursor pollutants, except SOX. ADEQ's projected 2032 
SOX emissions increase represents a small percentage of the 
overall emissions inventory compared to PM2.5 and 
precursors, whether compared individually or collectively.\106\ Also, 
the projected SOX emissions estimates reflect conservative 
assumptions concerning VPP future operations when considered against 
the facility's historical record and most likely future operating 
scenario. ADEQ provided additional analyses and information to 
demonstrate that VPP is unlikely to cause a violation of the 
PM2.5 NAAQS if VPP were to emit PM2.5 at PTE 
levels. In conclusion, we find that ADEQ has provided an adequate basis 
to demonstrate maintenance of the 24-hour PM2.5 NAAQS within 
the Nogales area through 2032.
---------------------------------------------------------------------------

    \106\ Our conclusion is further supported by the meteorological 
data (TSD, 17-24) and chemical speciation data (Plan, 44) that ADEQ 
has presented.
---------------------------------------------------------------------------

    Section 175A requires that maintenance plans provide for 
maintenance of the relevant NAAQS in the area for at least 10 years 
after redesignation. If this redesignation becomes effective in 2022, 
the projected 2032 emissions inventory demonstrates that the Nogales 
area will maintain the PM2.5 NAAQS for 10 years beyond 
redesignation. Moreover, the projected interim emissions inventory for 
2026, i.e., the milestone year between the 2017 attainment inventory 
and the 2032 maintenance plan horizon year, sufficiently demonstrates 
that the Nogales area will maintain the standards throughout the period 
from redesignation through 2032. Therefore, we propose to find that the 
Nogales Maintenance Plan adequately demonstrates maintenance of the 24-
hour PM2.5 NAAQS through 2032.
3. Verification of Continued Attainment
    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.\107\ 
Data collected by the monitoring network are also needed to implement, 
if triggered, the contingency provisions of the maintenance plan.
---------------------------------------------------------------------------

    \107\ Calcagni memo, 11.
---------------------------------------------------------------------------

    As discussed in section III.A of this proposal, PM2.5 is 
currently monitored by ADEQ within the Nogales area. In section 5.2 of 
the Nogales Maintenance Plan, ADEQ commits to continue operating a 
PM2.5 air quality monitoring network in the Nogales area 
consistent with federal regulations and to consult with the EPA via the 
annual network review process regarding any potential changes to the 
network. We find that the Nogales Maintenance Plan contains adequate 
provisions for continued ambient PM2.5 monitoring to verify 
continued attainment of the NAAQS through the maintenance period.
    In addition to the ambient air monitoring program, the EPA also 
recommends that the State verify continued attainment through methods 
other than ambient air quality monitoring to show no significant change 
in projected activity levels or emissions factors, e.g., periodic 
reviews of key data and assumptions used to develop the attainment 
inventory.\108\ In the Nogales Maintenance Plan, ADEQ commits to 
perform a comprehensive review of the factors and assumptions used to 
develop the attainment and projected inventories to determine whether 
significant changes have occurred.\109\ ADEQ's review will be conducted 
for the 2026 interim projection year and may include the following 
elements: Permit applications and source reports, population data, 
agricultural activity information, wildfire/prescribed burning data, 
and motor vehicle activity data.\110\ In the Plan, ADEQ also identifies 
the legal authority under which the State collects the needed 
information to conduct the comprehensive review of the factors and 
assumptions used in developing the attainment and projected emissions 
inventories. We find that ADEQ's commitment to verify continued 
attainment of the NAAQS through a comprehensive review of the factors 
and assumptions used to develop the emissions inventories in the 
Nogales Maintenance Plan is acceptable.
---------------------------------------------------------------------------

    \108\ Id.
    \109\ Nogales Maintenance Plan, 46, Section 5.4.
    \110\ Id. at 45-46.
---------------------------------------------------------------------------

4. 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.
    The State has adopted a contingency plan to address possible future 
PM2.5 air quality problems in the Nogales area. The 
contingency provisions are included in section 5.5 of the Plan. Upon a 
monitored violation of the PM2.5 24-hour NAAQS, ADEQ commits 
to the following steps:

    1. Within 60 days of the NAAQS violation trigger, ADEQ will 
begin analyzing the cause(s) of the exceedances that led to the 
violation. The analysis will include review and validation of 
ambient air quality and meteorological data, evaluation to determine 
if any of the exceedances qualifies as an exceptional event per the 
EPA's Exceptional Event Rule (EER),\111\ and assessment of emissions 
sources contributing to elevated PM2.5 levels.
---------------------------------------------------------------------------

    \111\ 81 FR 68216 (October 3, 2016).
---------------------------------------------------------------------------

    2. If an exceedance qualifies as an exceptional event, ADEQ will 
prepare and submit to the EPA an exceptional event demonstration. 
If, during its evaluation, ADEQ determines that new measures are 
needed to satisfy the requirements of the exceptional events rule, 
ADEQ will adopt and implement new measures that are permanent and 
enforceable and meet the ``reasonable'' level of control described 
in the EER.
    3. If the exceedance does not qualify as an exceptional event, 
ADEQ will determine which source(s) contributed to the exceedance, 
identify existing control measures for the source(s), verify 
source(s) compliance with existing measures, and if necessary, 
develop, adopt and implement new permanent and enforceable measures 
or strengthen existing measures.

    Under the contingency plan, if new control measures are needed, 
then the adoption process will begin within 12 months and final 
adoption will be completed within 18 months of the triggering event 
(i.e., a monitored violation of the PM2.5 NAAQS). The State 
would require compliance with new control measures within six months of 
final adoption of the contingency measures.

[[Page 11677]]

    The Nogales Maintenance Plan includes a list of contingency 
measures considered for implementation if the contingency plan is 
triggered focusing on the principal source categories contributing to 
PM2.5 emissions in the Nogales area.\112\ The source 
categories include stationary sources, fugitive dust sources, and 
residential wood burning devices. In addition to the contingency plan, 
ADEQ commits to initiate a review of VPP operations to reduce emissions 
and implement control measures, as needed, if the facility's direct 
PM2.5 emissions exceed 20 percent of PTE as shown in the VPP 
annual facility emissions report.\113\
---------------------------------------------------------------------------

    \112\ Nogales Maintenance Plan, 47.
    \113\ Id. at 47-48.
---------------------------------------------------------------------------

    From our review, we find that the State has established a 
contingency plan for the Nogales area that clearly contains the 
following: (1) Tracking and triggering mechanisms to determine when 
contingency measures are needed; (2) a description of the process for 
developing and implementing contingency measures; (3) specific 
timelines for action; and (4) identifies specific source categories for 
review, including a specific review process and trigger for the VPP 
facility. Thus, we propose to conclude that the contingency provisions 
of the Nogales Maintenance Plan are adequate to ensure prompt 
correction of a NAAQS violation and satisfy the requirements of the CAA 
section 175A(d).
5. Transportation Conformity and 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 cause or contribute to 
violations of the NAAQS, worsen the severity of an existing violation, 
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 at 40 CFR part 93, 
subpart A. Under this rule, metropolitan planning organizations 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 
all control strategy SIPs and maintenance plans.\114\
---------------------------------------------------------------------------

    \114\ Control strategy SIPs refer to 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 established for specific 
years and specific pollutants or precursors and must reflect the motor 
vehicle control measures contained in the RFP plan and the attainment 
or maintenance demonstration. Under the transportation conformity rule, 
budgets must be established for the last year of the maintenance plan 
for direct PM2.5 and PM2.5 precursors subject to 
transportation conformity analyses.\115\
---------------------------------------------------------------------------

    \115\ Section 93.102(b)(2)(iii) of the conformity rule 
identifies VOC and NOX as PM10 precursor 
pollutants that are presumed insignificant unless the SIP makes a 
finding that the precursor is significant.
---------------------------------------------------------------------------

    For budgets to be approvable, they must meet, at a minimum, the 
EPA's adequacy criteria.\116\ To meet these requirements in maintenance 
plans, the budgets must be consistent with the maintenance requirements 
and reflect all the motor vehicle control measures contained in the 
maintenance demonstration.\117\ 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 budget during a public comment period; 
and (3) making a finding of adequacy or inadequacy.\118\
---------------------------------------------------------------------------

    \116\ 40 CFR 93.118(e)(4).
    \117\ 40 CFR 93.118(e)(4)(iii), (iv) and (v). For more 
information on the transportation conformity requirements and 
applicable policies on MVEBs, please visit our transportation 
conformity website at: https://www.epa.gov/otaq/stateresources/transconf/index.htm.
    \118\ 40 CFR 93.118(f)(2).
---------------------------------------------------------------------------

    Within the Nogales Maintenance Plan, ADEQ described the process the 
State followed for developing the budgets and has enumerated a budgets 
for the Nogales area.\119\ The 2032 conformity budgets for 
PM2.5 and NOX for the Nogales area are provided 
in Table 7 on a pounds per day basis consistent with the maintenance 
demonstration emissions inventories discussed this proposal. Because 
the Nogales area experiences high volumes of commercial trucking 
crossing the international border with Mexico, ADEQ included a 
NOX budget because NOX emissions are a mobile 
source related PM2.5 precursor. ADEQ did not include 
emissions from road construction and maintenance. Upon reviewing the 
emissions inventories, the State determined that road construction and 
maintenance emissions were de minimis and unlikely to cause or 
contribute to violations of the 24-hour PM2.5 NAAQS.\120\
---------------------------------------------------------------------------

    \119\ Nogales Maintenance Plan, 49-52.
    \120\ Id. at 50.

   Table 7--2032 Motor Vehicle Emissions Budgets for the Nogales Area
                         [Pounds per winter day]
------------------------------------------------------------------------
                                               PM2.5      NOX  emissions
                 Source                      emissions
------------------------------------------------------------------------
Direct On-Road Mobile Sources (exhaust,              8.2           513.0
 tire and brake wear)...................
Paved Road Fugitive Dust................            77.8  ..............
Unpaved Road Fugitive Dust..............           551.0  ..............
                                         -------------------------------
    Totals..............................           637.0           513.0
------------------------------------------------------------------------
Source: Plan, 51, 52; Tables 6-3 and 6-4.

[[Page 11678]]

    Table 8 shows the 2032 budgets provided by ADEQ on a tons per year 
basis, consistent with the annual emissions inventories.\121\
---------------------------------------------------------------------------

    \121\ It should be noted that a transcription error occurred in 
Table 6-3 of the Plan where the figures for paved and unpaved road 
emissions were inadvertently switched, each for the other in the 
tons per day column. Table 8 reflects the correct tons per year 
assignment consistent with the pounds per day figures and the annual 
emissions inventories figures.

   Table 8--2032 Motor Vehicle Emissions Budgets for the Nogales Area
                             [Tons per year]
------------------------------------------------------------------------
                                               PM2.5      NOX  emissions
                 Source                      emissions
------------------------------------------------------------------------
Direct On-Road Mobile Sources (exhaust,              1.4            93.7
 tire and brake wear)...................
Paved Road Fugitive Dust................            14.2  ..............
Unpaved Road Fugitive Dust..............           100.6  ..............
                                         -------------------------------
    Total...............................           116.2            93.7
------------------------------------------------------------------------
Source: Plan, 51, 52; Tables 6-3 and 6-4.

    ADEQ provided the methodologies to develop the motor vehicle 
emissions budgets in the TSD and appendices C and D of the Plan. As 
discussed in section III.D of this proposal, ADEQ used the EPA's 
MOVES2014b model in the development of these budgets; this was the 
latest available version of the model at the time the Nogales 
Maintenance Plan was developed. Paved road VMT estimates for estimating 
direct and fugitive PM2.5 emissions were provided by and in 
consultation with ADOT using an interpolation methodology where 2017, 
2026, and 2032 VMT were estimated from Nogales area traffic data.\122\ 
ADEQ used the most recent AP-42 emissions factor equations from the EPA 
and National Emissions Inventory data to develop paved and unpaved road 
fugitive dust emissions estimates.\123\
---------------------------------------------------------------------------

    \122\ TSD, 46-48, Section 5.3; TSD, 60 61, Section 6.3.
    \123\ ADEQ used the appropriate AP-42 guidance in sections 
13.2.1 and 13.2.2 to calculate fugitive dust from paved and unpaved 
roads. The AP-42 emission factor equation inputs for estimating 
paved and unpaved road fugitive dust emissions can be found in 
Appendices C and D of the Plan. The most recent EPA revision and 
approval of these AP-42 emission factor equations occurred in 2011 
and are reflected in the Plan's estimates; 76 FR 6328 (February 4, 
2011).
---------------------------------------------------------------------------

    As part of our review of the approvability of the motor vehicle 
emissions budget in the Nogales Maintenance Plan, we have evaluated the 
budgets using the adequacy criteria specified in the transportation 
conformity rule.\124\ First and foremost, Section 93.118(e)(4)(iv) 
requires that a budget, when considered together with all other 
emissions sources, be consistent with applicable requirements for RFP, 
attainment, or maintenance (whichever is relevant to a given 
implementation plan submission). In this case, the Nogales area budget 
is consistent with the requirements for maintenance, as discussed in 
Sections III.D of this proposal. Second, the Nogales budget is 
presented in a daily format consistent with a maintenance plan intended 
to meet the 24-hour PM2.5 NAAQS, as well as an annual and 
tons per year basis consistent with the emissions inventories. Third, 
Section 93.118(e)(4)(iii) requires that the budget be clearly 
identified and precisely quantified. ADEQ has done so in Section 6.3.3 
of the Plan. Fourth, ADEQ developed the budgets in consultation with 
ADOT, the regional transportation agency for the Nogales area. Lastly, 
prior to their submission to the EPA, ADEQ submitted the budgets for 
public inspection and comment as discussed in Section II.B of this 
proposal.
---------------------------------------------------------------------------

    \124\ 40 CFR 93.118(e)(4) and (5).
---------------------------------------------------------------------------

    We have reviewed the motor vehicle emissions budgets in the Nogales 
Maintenance Plan and find that they meet applicable statutory and 
regulatory requirements including the adequacy criteria in 40 CFR 
93.1118(e)(4) and (5). We will complete the adequacy review concurrent 
with our final action on the Nogales Maintenance Plan. The EPA is not 
required under the transportation conformity rule to find budgets 
adequate prior to our proposing approval of them.\125\ In this proposed 
rule, the EPA is announcing that the adequacy process for these budgets 
begins, and the public has 30 days to comment on the budgets presented 
here and in the Nogales Maintenance Plan.\126\
---------------------------------------------------------------------------

    \125\ Under the transportation conformity regulations, the EPA 
may review the adequacy of submitted motor vehicle emission budgets 
simultaneously with the EPA's approval or disapproval of the 
submitted implementation plan. 40 CFR 93.118(f)(2).
    \126\ 40 CFR 93.118(f)(2)(i) and (ii).
---------------------------------------------------------------------------

    While a finding of adequacy and approval are two separate actions, 
reviewing the budgets for their adequacy against the criteria in the 
transportation conformity rule informs the EPA's decision to propose 
approval of the budgets. We have completed our detailed review of the 
Nogales Maintenance Plan and are proposing herein to approve the 
maintenance demonstration in section III.D, and we have reviewed the 
budgets in the Nogales Maintenance Plan and find that they are 
consistent with this maintenance demonstration. Furthermore, the 
budgets are based on control measures that have been adopted and 
implemented, and they meet all other applicable statutory and 
regulatory requirements including the adequacy criteria in 40 CFR 
93.1118(e)(4) and (5). Therefore, we are proposing to approve the 2032 
maintenance year budgets in the Nogales Maintenance Plan. We may either 
finalize the adequacy process and find the budgets adequate for the 
purposes of transportation conformity or approve the budgets for the 
24-hour PM2.5 NAAQS in the Nogales area as proposed, 
whichever occurs first. We may also finalize an adequacy finding and 
approval of the budgets in our final action on the Nogales Maintenance 
Plan, per 40 CFR 93.118(f)(2)(iii).

IV. Environmental Justice Considerations

    Executive Order 12898 requires that federal agencies, to the 
greatest extent practicable and permitted by law, identify and address 
disproportionately high and adverse human health or environmental 
effects of their actions on minority and low-income populations.\127\ 
Additionally, Executive Order 13985 directs federal government agencies 
to assess whether, and to what extent, their programs and policies 
perpetuate systemic barriers to opportunities and benefits for people 
of color and other underserved groups,\128\

[[Page 11679]]

and Executive Order 14008 directs federal agencies to develop programs, 
policies, and activities to address the disproportionate health, 
environmental, economic, and climate impacts on disadvantaged 
communities.\129\ To identify environmental burdens and susceptible 
populations in underserved communities in the Nogales area, we 
performed a screening-level analysis using the EPA's environmental 
justice (EJ) screening and mapping tool (``EJSCREEN'').\130\ Our 
screening-level analysis indicates that the Nogales area scores high 
when compared to the national average for the EJSCREEN ``Demographic 
Index,'' which is the average of an area's percent minority and percent 
low income populations, i.e., the two demographic indicators explicitly 
named in Executive Order 12898.\131\ As discussed in the EPA's EJ 
technical guidance, people of color and low-income populations often 
experience greater exposure and disease burdens than the general 
population, which can increase their susceptibility to adverse health 
effects from environmental stressors.\132\ Underserved communities can 
also experience reduced access to health care, nutritional, and fitness 
resources, further increasing their susceptibility.
---------------------------------------------------------------------------

    \127\ 59 FR 7629 (February 16, 1994).
    \128\ 86 FR 7009 (January 25, 2021).
    \129\ 86 FR 7619 (February 1, 2021).
    \130\ ``EJScreen for NogalesAZ NAA 2006 FinePM NAAQS 
18Jan2022.xlsx'' in the docket for this proposal. The EPA used 
EJSCREEN to obtain environmental and demographic indicators 
representing the Nogales area. EJSCREEN provides a nationally 
consistent dataset and approach for combining environmental and 
demographic indicators and is available at https://www.epa.gov/ejscreen/what-ejscreen.
    \131\ EJSCREEN reports environmental indicators (e.g., air 
toxics cancer risk, lead paint exposure, and traffic proximity and 
volume) and demographic indicators (e.g., people of color, low 
income, and linguistically isolated populations). Depending on the 
indicator, a community that scores highly for an indicator may have 
a higher percentage of its population within a demographic group or 
a higher average exposure or proximity to an environmental health 
hazard compared to the state, region, or national average. EJSCREEN 
also reports EJ indexes, which are combinations of a single 
environmental indicator with the EJSCREEN Demographic Index. For 
additional information about environmental and demographic 
indicators and EJ indexes reported by EJSCREEN, see EPA, ``EJSCREEN 
Environmental Justice Mapping and Screening Tool--EJSCREEN Technical 
Documentation,'' section 2, September 2019.
    \132\ EPA, ``Technical Guidance for Assessing Environmental 
Justice in Regulatory Analysis,'' section 4, June 2016.
---------------------------------------------------------------------------

    As discussed in section III.A, the Nogales area meets the health-
based 2006 PM2.5 24-hour NAAQS of 35 [mu]g/m\3\ based on the 
2018-2020 design value and continues to meet the NAAQS based on 
preliminary data for 2021. This proposed action would redesignate the 
Nogales area to attainment. Redesignation to attainment would not, in 
and of itself, create any new requirements. Rather, it would result in 
the applicability of requirements already contained in the CAA for 
areas that have been redesignated to attainment. Thus, we believe that 
our proposed action 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.

V. Proposed Action and Request for Public Comment

    Under CAA section 110(k)(3), and for the reasons presented above, 
the EPA is proposing to approve the Nogales Maintenance Plan submitted 
by ADEQ on April 13, 2021, as a revision to the Arizona SIP. In doing 
so, we are proposing to approve the maintenance demonstration and 
contingency provisions as meeting all of the applicable requirements 
for maintenance plans and related contingency provisions in CAA section 
175A, and to approve the motor vehicle emissions budgets and find that 
these budgets are adequate.
    In addition, under CAA section 107(d)(3)(D), we are proposing to 
approve Arizona's request to redesignate the Nogales area from 
nonattainment to attainment for the 2006 24-hour PM2.5 
NAAQS. We are doing so based on our conclusion that the State has met 
all the criteria for redesignation under CAA section 107(d)(3)(E). 
Specifically, we propose to make the following findings:
     The Nogales area has attained the 24-hour PM2.5 
NAAQS based on the most recent three-year period (2018-2020) of 
quality-assured, certified, and complete PM2.5 data;
     The relevant portions of the Arizona SIP are fully 
approved;
     The improvement in Nogales area ambient air quality is due 
to permanent and enforceable reductions in direct and precursor 
PM2.5 emissions;
     Arizona has met all requirements applicable to the Nogales 
area with respect to section 110 and part D of the CAA; and
     The Nogales area has a fully approved maintenance plan 
meeting the requirements of CAA section 175A, including motor vehicle 
emissions budgets for the year 2032.
    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.

VI. Statutory and Executive Order Reviews

    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 geographic area and do not 
impose any additional regulatory requirements on sources beyond those 
imposed by state law. 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 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 
approve state choices provided they meet the criteria of the CAA. 
Accordingly, these proposed actions merely propose to approve a state 
plan and redesignation request as meeting federal requirements and do 
not impose additional requirements beyond those imposed by state law. 
For these reasons, the proposed actions:
     Are 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);
     Do not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Are 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.);
     Do 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);
     Do not have Federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999)
     Are not an economically significant regulatory action 
based on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Are not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Are 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 CAA; and

[[Page 11680]]

     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 IV of 
this proposal.
    In addition, there are no areas of Indian country within the 
Nogales area, and the State plan for which the EPA is proposing 
approval does not 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, this proposed action 
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), because 
redesignation is an action that affects the status of a geographical 
area and does not impose any new regulatory requirements on tribes, 
impact any existing sources of air pollution on tribal lands, nor 
impair the maintenance of NAAQS in tribal lands.

List of Subjects

40 CFR Part 52

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

40 CFR Part 81

    Environmental protection, Air pollution control, National parks, 
Wilderness areas.

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

    Dated: February 18, 2022.
Martha Guzman Aceves,
Regional Administrator, Region IX.
[FR Doc. 2022-04070 Filed 3-1-22; 8:45 am]
BILLING CODE 6560-50-P