Proposed Rule2026-21288
Approval and Promulgation of Implementation Plans-Pinal County (Part); West Pinal, AZ PM10 Nonattainment Area; Moderate Area, Serious Area, and Section 189(d) Plan for Attainment of the 24-Hour PM10 Standard
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
October 19, 2026
Issuing agencies
Environmental Protection Agency
Abstract
The U.S. Environmental Protection Agency (EPA) is proposing to approve a state implementation plan (SIP) revision submitted by the State of Arizona to meet Clean Air Act (CAA or "Act") requirements applicable to the Pinal County (Part); West Pinal PM<INF>10</INF> nonattainment area ("West Pinal County PM<INF>10</INF> Nonattainment Area"). The EPA is proposing to find that the submitted SIP revision meets all applicable "Moderate" area, "Serious" area, and CAA section 189(d) requirements for the PM<INF>10</INF> national ambient air quality standards (NAAQS). Additionally, the EPA is proposing to approve the PM<INF>10</INF> motor vehicle emissions budgets included with the SIP revision for transportation conformity purposes. The EPA is also starting the adequacy process for these budgets. Our proposed approval of the SIP revision would establish an attainment date of December 31, 2026, for the area.
Full Text
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<title>Federal Register, Volume 91 Issue 200 (Monday, October 19, 2026)</title>
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[Federal Register Volume 91, Number 200 (Monday, October 19, 2026)]
[Proposed Rules]
[Pages 66048-66058]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-21288]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R09-OAR-2026-5119; FRL-13482-01-R9]
Approval and Promulgation of Implementation Plans--Pinal County
(Part); West Pinal, AZ PM10 Nonattainment Area; Moderate Area, Serious
Area, and Section 189(d) Plan for Attainment of the 24-Hour PM10
Standard
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: The U.S. Environmental Protection Agency (EPA) is proposing to
approve a state implementation plan (SIP) revision submitted by the
State of Arizona to meet Clean Air Act (CAA or ``Act'') requirements
applicable to the Pinal County (Part); West Pinal PM<INF>10</INF>
nonattainment area (``West Pinal County PM<INF>10</INF> Nonattainment
Area''). The EPA is proposing to find that the submitted SIP revision
meets all applicable ``Moderate'' area, ``Serious'' area, and CAA
section 189(d) requirements for the PM<INF>10</INF> national ambient
air quality standards (NAAQS). Additionally, the EPA is proposing to
approve the PM<INF>10</INF> motor vehicle emissions budgets included
with the SIP revision for transportation conformity purposes. The EPA
is also starting the adequacy process for these budgets. Our proposed
approval of the SIP revision would establish an attainment date of
December 31, 2026, for the area.
DATES: Comments must be received on or before November 18, 2026.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2026-5119 at <a href="https://www.regulations.gov">https://www.regulations.gov</a>. For comments submitted at
<a href="http://Regulations.gov">Regulations.gov</a>, follow the online instructions for submitting
comments. Once submitted, comments cannot be edited or removed from
<a href="http://Regulations.gov">Regulations.gov</a>. 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.
[[Page 66049]]
The written comment is considered the official comment and should
include discussion of all points you wish to make. The EPA will
generally not consider comments or comment contents located outside of
the primary submission (i.e., on the web, cloud, or other file sharing
system). For additional submission methods, please contact the person
identified in the FOR FURTHER INFORMATION CONTACT section. For the full
EPA public comment policy, information about CBI or multimedia
submissions, and general guidance on making effective comments, please
visit <a href="https://www.epa.gov/dockets/commenting-epa-dockets">https://www.epa.gov/dockets/commenting-epa-dockets</a>. If you need
assistance in a language other than English or if you are a person with
a disability who needs a reasonable accommodation at no cost to you,
please contact the person identified in the FOR FURTHER INFORMATION
CONTACT section.
FOR FURTHER INFORMATION CONTACT: Jennifer Williams, EPA Region IX, 75
Hawthorne St., San Francisco, CA 94105. By telephone: (213) 244-1824,
or by email at <a href="/cdn-cgi/l/email-protection#67100e0b0b0e060a14490d0209090e0102152702170649000811"><span class="__cf_email__" data-cfemail="a7d0cecbcbcec6cad489cdc2c9c9cec1c2d5e7c2d7c689c0c8d1">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION: Throughout this proposed rule, the use of
``we,'' ``us,'' or ``our'' is intended to refer to the EPA. We use
multiple abbreviations and terms in this proposed rule. While this list
may not be exhaustive, for ease of reading and for reference purposes,
the EPA defines the following terms and acronyms here:
ADEQ Arizona Department of Environmental Quality
BACM Best Available Control Measures
BACT Best Available Control Technology
CAA Clean Air Act
CBI Confidential Business Information
EI Emissions Inventory
EPA U.S. Environmental Protection Agency
FHWA Federal Highway Administration
FTA Federal Transit Administration
MAG Maricopa Association of Governments
[micro]g/m\3\ Micrograms per Cubic Meter
MPO Metropolitan Planning Organization
NAAQS National Ambient Air Quality Standards
NEI National Emission Inventory
NH<INF>3</INF> Ammonia
NO<INF>X</INF> Oxides of Nitrogen
PCAQCD Pinal County Air Quality Control District
PM Particulate Matter
PM<INF>10</INF> Particulate Matter with a Diameter of Ten Microns or
Less
RACM Reasonably Available Control Measures
RFP Reasonable Further Progress
SIP State Implementation Plan
SO<INF>2</INF> Sulfur Dioxide
TSD Technical Support Document
VOC Volatile Organic Compounds
VMT Vehicle Miles Traveled
West Pinal County Pinal County (Part); West Pinal
Table of Contents
I. Executive Summary
A. What proposed action is the EPA taking?
B. What is the legal authority and what are the requirements?
II. PM<INF>10</INF> Air Quality Planning in the West Pinal County
PM<INF>10</INF> Nonattainment Area
III. Overview of Applicable CAA Requirements
A. Emissions Inventories
B. PM<INF>10</INF> Precursors
C. Best Available Control Measures and Reasonably Available
Control Measures Demonstration
D. CAA Section 189(d) Attainment Demonstration and Five Percent
Requirement
E. Reasonable Further Progress and Quantitative Milestones
F. Contingency Measures
G. Transportation Conformity and Motor Vehicle Emissions Budgets
H. Adequate Authority
IV. Evaluation of the 2023 Five Percent Plan's Compliance With CAA
Requirements
A. Emissions Inventories
B. PM<INF>10</INF> Precursors
C. Best Available Control Measures and Reasonably Available
Control Measures Demonstration
D. CAA Section 189(d) Attainment Demonstration and Five Percent
Requirement
E. Reasonable Further Progress and Quantitative Milestones
F. Contingency Measures
G. Transportation Conformity and Motor Vehicle Emissions Budgets
H. Adequate Legal Authority
V. Summary of Proposed Actions
VI. Statutory and Executive Order Reviews
I. Executive Summary
A. What proposed action is the EPA taking?
The EPA is proposing to approve a SIP revision submitted by the
State of Arizona to meet all Moderate area, Serious area, and CAA
section 189(d) requirements applicable to the West Pinal County
PM<INF>10</INF> Nonattainment Area for the PM<INF>10</INF> NAAQS. The
EPA is also proposing to approve the PM<INF>10</INF> motor vehicle
emissions budgets included with the SIP revision for transportation
conformity purposes and is starting the adequacy process for these
budgets.
B. What is the legal authority and what are the requirements?
CAA sections 188 and 189 contain specific planning and control
requirements relevant to the PM<INF>10</INF> NAAQS while CAA sections
110 and 172 contain general planning and control requirements for all
nonattainment plans.
The EPA is proposing approval of the baseline and attainment year
emission inventory requirements of CAA section 172(c)(3), the BACM
demonstration requirements of CAA section 189(b)(1)(B), the RACM
demonstration requirements of CAA sections 189(a)(1)(C) and 172(c)(1),
the attainment demonstration requirements of CAA sections 189(d) and
179(d)(3), the five percent demonstration requirements of CAA section
189(d), the reasonable further progress and quantitative milestone
demonstration requirements of CAA sections 172(c)(2) and 189(c), the
contingency measures requirements of CAA section 172(c)(9), and the
motor vehicle emissions budgets as meeting the criteria for budgets in
CAA section 176(c) and 40 CFR 93.118(e). The EPA is also starting the
adequacy process for these budgets under 40 CFR 93.188(f).
II. PM10 Air Quality Planning in the West Pinal County PM10
Nonattainment Area
The NAAQS are standards for certain ambient air pollutants set by
the EPA to protect public health and welfare. Particulate matter with a
diameter of ten microns or less (PM<INF>10</INF>) is among the ambient
air pollutants for which the EPA has established health-based
standards. PM<INF>10</INF> causes adverse health effects by penetrating
deep in the lungs, aggravating the cardiopulmonary system. Children,
the elderly, and people with asthma and heart conditions are the most
vulnerable.
On July 1, 1987, the EPA revised the health-based NAAQS for
particulate matter, establishing two PM<INF>10</INF> standards, an
annual standard and a 24-hour standard.\1\ Effective December 18, 2006,
the EPA revoked the annual PM<INF>10</INF> standard but retained the
24-hour PM<INF>10</INF> standard.\2\ The 24-hour PM<INF>10</INF>
standard of 150 micrograms per cubic meter ([micro]g/m\3\) is attained
when the expected number of days with a 24-hour average concentration
above 150 [micro]g/m\3\ per calendar year averaged over a three-year
period, as determined in accordance with appendix K to 40 CFR part 50,
is equal to or less than one.\3\
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\1\ 52 FR 24672 (July 1, 1987).
\2\ 71 FR 61144 (Oct. 17, 2006).
\3\ 40 CFR 50.6 and 40 CFR part 50, appendix K.
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On May 31, 2012, the EPA designated a portion of State lands in
Pinal County, Arizona (``West Pinal County'') as nonattainment for the
1987 PM<INF>10</INF> NAAQS based on 2006-2008 data.\4\ West Pinal
County is located in central Arizona, southeast of the Phoenix
metropolitan area and northwest of the city of Tucson. Pinal County
covers 5,365 square miles and has two distinct western and eastern
regions with
[[Page 66050]]
different characteristics relevant to pollution formation. The West
Pinal County PM<INF>10</INF> Nonattainment Area is located within the
western region, characterized by low desert valleys and an arid
climate. The eastern region is mountainous, with elevations up to 6,441
feet. The West Pinal County PM<INF>10</INF> Nonattainment Area
encompasses all land geographically located within Pinal County west of
the north-south line defined by the boundary between Townships 10E and
11E, but excluding the main reservation of the Tohono O'odham Nation
and excluding the Apache Junction portion of the existing Phoenix
PM<INF>10</INF> nonattainment area.
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\4\ 77 FR 32024 (May 31, 2012). The boundaries for the West
Pinal County PM<INF>10</INF> Nonattainment Area are described in 40
CFR 81.303.
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As a result of the nonattainment designation, the West Pinal County
PM<INF>10</INF> Nonattainment Area was classified as a Moderate
PM<INF>10</INF> nonattainment area with an attainment date of as
expeditiously as practicable, but no later than December 31, 2018. The
Arizona Department of Environmental Quality (ADEQ) submitted a SIP
revision intended to meet the Moderate PM<INF>10</INF> nonattainment
requirements on December 21, 2015 (``2015 West Pinal Plan'').
On June 24, 2020, the EPA determined that West Pinal County
PM<INF>10</INF> Nonattainment Area did not attain the 1987
PM<INF>10</INF> NAAQS by December 31, 2018.\5\ Pursuant to CAA section
188(b)(2), the area was reclassified to ``Serious'' nonattainment with
an attainment date of as expeditiously as practicable, but no later
than December 31, 2022.\6\
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\5\ 85 FR 37756 (June 24, 2020).
\6\ Id.
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On January 8, 2021, the EPA proposed to disapprove the 2015 West
Pinal Plan.\7\ On May 17, 2021, ADEQ withdrew the 2015 West Pinal Plan,
with the exception of several rules and statutes that had been approved
into the SIP in 2017.\8\ Consequently, the EPA did not finalize the
actions proposed on January 8, 2021, with respect to the Moderate area
plan requirements. Instead, on July 23, 2021, the EPA found that
Arizona had failed to submit a plan to address these requirements.\9\
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\7\ 86 FR 1347 (Jan. 8, 2021).
\8\ Letter dated May 17, 2021, from Daniel Czecholinski,
Director, Air Quality Division, ADEQ, to Deborah Jordan, Acting
Regional Administrator, EPA Region IX, Subject: ``RE: Withdrawal
from EPA Consideration of the 2015 Arizona State Implementation Plan
Revision: West Pinal County PM<INF>10</INF> Nonattainment Area.''
\9\ 86 FR 38928 (July 23, 2021).
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On May 31, 2022, ADEQ adopted and submitted the ``2022 Serious Area
Particulate Plan for PM<INF>10</INF> for the West Pinal County
Nonattainment Area'' (``2022 West Pinal Plan''),\10\ as a revision to
the Arizona SIP.\11\ In addition to addressing the Moderate and Serious
area plan requirements, the 2022 West Pinal Plan included a request for
an extension of the December 31, 2022 attainment date pursuant to CAA
section 188(e). On November 30, 2022, the EPA issued a letter finding
the 2022 West Pinal Plan complete under CAA section 110(k).\12\
However, the EPA did not approve the Plan or the attainment date
extension request. On May 19, 2025, ADEQ withdrew the 2022 West Pinal
Plan.\13\
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\10\ West Pinal PM<INF>10</INF> Plan, Appendix E, Exhibit 2,
Resolution to Adopt the 2022 Serious Area Particulate Plan for PM-10
for the West Pinal County Nonattainment Area.
\11\ Letter dated May 31, 2022, from Daniel Czecholinski,
Director, Air Quality Division, ADEQ, to Martha Guzman, Regional
Administrator, EPA Region IX, Subject: ``Arizona State
Implementation Plan Revision, Maricopa Association of Governments
2022 Serious Area Particulate Plan for PM-10 for the West Pinal
County Nonattainment Area.''
\12\ Letter dated November 30, 2022, from Elizabeth J. Adams,
Director, Air and Radiation Division, EPA Region IX, to Misael
Cabrera, Director, ADEQ, Subject: ``Completeness Finding for State
Implementation Plan (SIP) Submission for West Pinal County for the
1987 PM<INF>10</INF> National Ambient Air Quality Standards (NAAQS)
and Termination of Clean Air Act (CAA) Sanctions Clocks.''
\13\ Letter dated May 15, 2025, from Daniel Czecholinkski,
Director, Air Quality Division, ADEQ to Josh F.W. Cook, Regional
Administrator, EPA Region IX, Subject: ``Withdrawal from EPA
Consideration of the 2022 Serious Area Particulate Plan for
PM<INF>10</INF> for the West Pinal County Nonattainment Area.''
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On July 21, 2023, the EPA determined that the West Pinal County
PM<INF>10</INF> Nonattainment Area did not attain the 1987
PM<INF>10</INF> NAAQS by the December 31, 2022 Serious area attainment
date.\14\ Pursuant to CAA section 189(d), Arizona was required to
submit a revision to the SIP for the West Pinal County PM<INF>10</INF>
Nonattainment Area by December 31, 2023.
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\14\ 88 FR 47026 (July 21, 2023).
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On November 29, 2023, the Maricopa Association of Governments (MAG)
adopted the ``2023 Five Percent Particulate Plan for PM-10 for the West
Pinal County Nonattainment Area'' (``2023 Five Percent Plan'' or
``Plan''). On December 14, 2023, ADEQ submitted the 2023 Five Percent
Plan on behalf of MAG.\15\ The EPA reviewed the submission for
completeness under our completeness criteria in 40 CFR part 51,
appendix V and determined that the submittal meets these minimum
criteria on June 14, 2024.\16\ The EPA is proposing approval of the
submission as meeting the requirements of CAA section 189(d) as well as
Moderate and Serious area requirements.
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\15\ Letter dated December 13, 2023, from Hether Krause, Deputy
Director, Air Quality Division, ADEQ to Martha Guzman, Regional
Administrator, EPA Region IX, Subject: ``Arizona State
Implementation Plan Revision, Maricopa Association of Governments
2023 Five Percent Particulate Plan for PM-10 for the West Pinal
County Nonattainment Area.''
\16\ Letter dated June 14, 2024, from Mathew Lakin, Director,
Air and Radiation Division, EPA Region IX to Karen L. Peters,
Cabinet Executive Officer, ADEQ, Subject: ``Re: Completeness Finding
for the State Implementation Plan (SIP) Submission for the West
Pinal Nonattainment Area for the 1987 PM<INF>10</INF> National
Ambient Air Quality Standards (NAAQS).''
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III. Overview of Applicable CAA Requirements
As a Serious PM<INF>10</INF> nonattainment area that failed to
attain the NAAQS by its applicable attainment date of December 31,
2022, the West Pinal County PM<INF>10</INF> Nonattainment Area is
subject to the requirements of CAA section 189(d). In addition, because
the EPA has not previously approved a Moderate or a Serious area plan
for the West Pinal County PM<INF>10</INF> Nonattainment Area, the area
is also required to demonstrate that it has met the requirements
associated with these classifications.
CAA section 189(d) provides that the State shall ``submit within 12
months after the applicable attainment date, plan revisions that
provide for attainment of the PM<INF>10</INF> air quality standard and,
from the date of such submission until attainment, for an annual
reduction of PM<INF>10</INF> or PM<INF>10</INF> precursor emissions
within the area of not less than 5 percent of the amount of such
emissions as reported in the most recent inventory prepared for the
area.''
The general planning and control requirements for all nonattainment
plans are found in CAA sections 110 and 172. More specific planning and
control requirements relevant to the PM<INF>10</INF> NAAQS are found in
part D, subpart 4, in CAA sections 188 and 189. The EPA has issued a
General Preamble \17\ and Addendum to the General Preamble \18\ to
provide guidance to States for meeting the CAA's requirements for the
PM<INF>10</INF> NAAQS. The General Preamble mainly addresses the
requirements for Moderate nonattainment areas and the Addendum
addresses the requirements for Serious nonattainment areas. The EPA has
also issued other guidance documents
[[Page 66051]]
related to PM<INF>10</INF> plans that are discussed and cited below.
The specific PM<INF>10</INF> attainment planning requirements addressed
by this SIP submission are summarized below.
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\17\ ``State Implementation Plans; General Preamble for the
Implementation of Title I of the Clean Air Act Amendments of 1990,''
57 FR 13498 (Apr. 16, 1992) (``General Preamble'') and 57 FR 18070
(Apr. 28, 1992).
\18\ ``State Implementation Plans for Serious PM-10
Nonattainment Areas, and Attainment Date Waivers for PM-10
Nonattainment Areas Generally; Addendum to the General Preamble for
the Implementation of Title I of the Clean Air Act Amendments of
1990,'' 59 FR 41998 (Aug. 16, 1994) (``Addendum'').
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A. Emissions Inventories
CAA section 172(c)(3) requires a ``base year inventory'' that is a
comprehensive, accurate, current inventory of actual emissions from all
sources of the relevant pollutant or pollutants in the area. The plan
should also include a second projected attainment year inventory for
the year that the area is projected to attain the PM<INF>10</INF>
standards.
B. PM10 Precursors
CAA section 189(e) requires that the control requirements for major
stationary sources of direct PM<INF>10</INF> also apply to major
stationary sources of PM<INF>10</INF> precursors, except where the
Administrator determines that such sources do not contribute
significantly to PM<INF>10</INF> levels that exceed the standard in the
area. While CAA section 189(e) expressly requires control of precursors
from major stationary sources, subpart 4 and other CAA provisions
collectively require the control of direct PM<INF>10</INF> and
PM<INF>10</INF> precursors from all types of sources (i.e., stationary
sources, area sources and mobile sources) as may be needed for the
purposes of demonstrating attainment as expeditiously as practicable in
a given nonattainment area.\19\
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\19\ See CAA requirements for States to demonstrate attainment
``as expeditiously as practicable,'' CAA sections 188(c)(1) and
172(a)(1).
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C. Best Available Control Measures and Reasonably Available Control
Measures Demonstration
CAA section 189(b)(1)(B) requires that Serious area PM<INF>10</INF>
attainment plans provide for the implementation of best available
control measures (BACM) within four years of reclassification to
Serious. Because the Serious area attainment date of December 31, 2022,
has passed, and the EPA found that the area failed to attain by the
Serious area attainment date,\20\ we are evaluating the submission for
compliance with the BACM requirements now, in conjunction with the
State's SIP submission intended to meet the Moderate area, Serious
area, and CAA section 189(d) plan requirements. Furthermore, because
the EPA has not previously taken action to approve the SIP as meeting
the subpart 4 reasonably available control measures (RACM) Moderate
area planning requirements under CAA section 189 for the West Pinal
County PM<INF>10</INF> Nonattainment Area, the EPA is reviewing the
2023 Five Percent Plan for compliance with those requirements as
well.\21\
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\20\ See note 13.
\21\ The EPA does not normally conduct a separate evaluation to
determine whether a Serious area plan's measures also meet the RACM
requirements. As explained in the Addendum to the General Preamble,
we interpret the BACM requirement as generally subsuming the RACM
requirement--i.e., if we determine that the measures are indeed the
``best available,'' we have necessarily concluded that they are
``reasonably available.'' (Addendum to the General Preamble, 42010).
Therefore, a separate analysis to determine if the measures
represent a RACM level of control is not necessary. A proposed
approval of a Plan's provisions concerning implementation of BACM is
also a proposed finding that the Plan provides for the
implementation of RACM.
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D. CAA Section 189(d) Attainment Demonstration and Five Percent
Requirement
For Serious PM<INF>10</INF> nonattainment areas that do not attain
the PM<INF>10</INF> NAAQS by the applicable attainment date, CAA
section 189(d) requires the State to submit plan revisions that provide
for attainment of the NAAQS (i.e., an attainment demonstration) as
expeditiously as practicable, but no later than five years from the
publication date of the notice of a nonattainment finding. The plan
must also provide for an annual five percent reduction in
PM<INF>10</INF> or PM<INF>10</INF> precursor emissions for each year
from the date of submission until attainment. CAA section 189(d)
specifies that the State must submit these plan revisions within 12
months of the applicable attainment date that the area failed to meet.
E. Reasonable Further Progress and Quantitative Milestones
CAA section 172(c)(2) requires that implementation plans
demonstrate reasonable further progress (RFP) as defined in CAA section
171(1). CAA section 171(1) defines RFP as ``such annual incremental
reductions in emissions of the relevant air pollutant as are required
by this part [part D of title I] or may reasonably be required by the
Administrator for the purpose of ensuring attainment of the applicable
national ambient air quality standard by the applicable date.'' The
general RFP requirement of CAA section 172(c)(2) applies to SIP
submissions necessary to meet CAA section 189(d) for the
PM<INF>10</INF> NAAQS.
In addition, CAA section 189(c)(1), specifically applicable to the
PM<INF>10</INF> NAAQS, requires that an implementation plan contain
quantitative milestones that will be achieved every three years and
that will demonstrate that RFP is being met.
F. Contingency Measures
CAA section 172(c)(9) requires that implementation plans provide
for ``the implementation of specific measures to be undertaken if the
area fails to make reasonable further progress, or to attain the NAAQS
by the attainment date applicable under this part [part D of title I].
Such measures are to take effect in any such case without further
action by the State or the Administrator.'' The contingency measure
requirement of CAA section 172(c)(9) applies to the SIP submissions
necessary to meet CAA section 189(d) for the PM<INF>10</INF> NAAQS.
G. Transportation Conformity and Motor Vehicle Emissions Budgets
Transportation conformity is required by CAA section 176(c). The
conformity regulations found at 40 CFR part 93, subpart A require that
transportation plans, programs, and projects conform to the purpose of
the SIP and establish the criteria and procedures for determining
whether or not they do so. Conformity to the purpose of the SIP means
that transportation activities will not produce new air quality
violations, worsen existing violations, or delay timely attainment of
the NAAQS or any interim milestones. Once a SIP that contains motor
vehicle emissions budgets (``budgets'') has been submitted to the EPA,
and the Agency has found them adequate, these budgets are used for
determining conformity: emissions from planned transportation
activities must be less than or equal to the budgets.\22\
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\22\ See 40 CFR 93.118(a) to (e).
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H. Adequate Authority
CAA section 110(a)(2)(E)(i) requires that implementation plans
provide necessary assurances that the State (or the general purpose
local government or regional agency designated by the State for this
purpose) will have adequate personnel, funding and authority under
State law to carry out the requirements of such plan. Requirements for
legal authority are further defined in 40 CFR part 51, subpart L
(51.230-51.232) and for resources in 40 CFR 51.280. States and
responsible local agencies must also demonstrate that they have the
legal authority to adopt and enforce provisions of the SIP and to
obtain information necessary to determine compliance.
[[Page 66052]]
IV. Evaluation of the 2023 Five Percent Plan's Compliance With CAA
Requirements
A. Emissions Inventories
CAA section 172(c)(3) requires all nonattainment area plans to
include a base year emissions inventory that is a comprehensive,
accurate, and current inventory of actual emissions from all sources of
the relevant pollutant or pollutants in the area at issue. Also, the
State should submit a projected attainment year emissions inventory for
the year in which the State projects that the area will attain the
PM<INF>10</INF> standards. The EPA's emission inventory guidance
provides recommendations on how to develop and document emission
inventories.\23\
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\23\ See ``Emissions Inventory Guidance for Implementation of
Ozone and Particulate Matter National Ambient Air Quality Standards
(NAAQS) and Regional Haze Regulations,'' EPA, May 2017 (``2017 EI
Guidance'').
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The 2023 Five Percent Plan uses a 2017 base year emissions
inventory for Pinal County (``2017 PM<INF>10</INF> Inventory'') as a
starting point in the analysis. The 2017 PM<INF>10</INF> Inventory was
developed by ADEQ, Pinal County Air Quality Control District (PCAQCD),
and MAG. The 2017 PM<INF>10</INF> Inventory included emissions from
point sources (permitted sources), nonpoint sources (area sources),
nonroad mobile sources, and on-road mobile sources. This emission
inventory is sufficiently comprehensive, covering all sources of
PM<INF>10</INF> that have been found to be important sources of
relevant emissions in this and other PM<INF>10</INF> nonattainment
areas.
The 2017 PM<INF>10</INF> Inventory shows that the most significant
sources of annual emissions in the West Pinal County PM<INF>10</INF>
Nonattainment Area are unpaved road dust: private roads (31.5 percent),
unpaved road dust: agricultural roads (24.7 percent), unpaved road
dust: public roads (16.2 percent), windblown dust (9.0 percent),
tilling and harvesting (5.0 percent), feedlots (3.3 percent), and
construction (2.7 percent). The annual and daily PM<INF>10</INF>
emissions inventories and the emission estimation methodologies used to
develop the 2017 PM<INF>10</INF> Inventory are described in detail in
Appendix A, Exhibit 1 of the 2023 Five Percent Plan.
In general, the base year emissions inventory represents the
emissions contributing to the air quality problem addressed by the SIP
revision. Because the EPA's final rule determining that the West Pinal
County PM<INF>10</INF> Nonattainment Area failed to attain the
PM<INF>10</INF> standard by its attainment date used 2020-2022
monitoring data to make its determination, a year that is included
within that time period and the triennial schedule of the National
Emission Inventory (NEI) would generally be an appropriate base year.
While the 2020 NEI year would have been the most recent such year to
consider at the time of this plan's development, due to COVID-related
emissions anomalies, the 2023 Five Percent Plan concludes that 2020 was
not an appropriate inventory year. The base year, 2017, was chosen as
it is a reasonably current NEI year, and the most recent NEI year
available that was not 2020 at the time of plan development.
The 2017 PM<INF>10</INF> Inventory includes only primary
PM<INF>10</INF> emissions and does not include emissions for
PM<INF>10</INF> precursors. As described in section IV.B of this
document, MAG determined that precursors do not play a significant role
in the PM<INF>10</INF> exceedances in the West Pinal County
PM<INF>10</INF> Nonattainment Area and the EPA's analysis supports this
conclusion.
The 2023 Five Percent Plan includes a 2026 projected attainment
year emissions inventory (``attainment year inventory'') that was
developed using annual PM<INF>10</INF> emissions under implementation
of Moderate area (existing) controls from the 2017 base year inventory
through 2021 and Serious area controls from 2022 through 2026. Emission
growth factors were developed for each source category relative to 2017
(growth or decline) and applied based on factors including, but not
limited to, forecasted total population growth and vehicle miles
traveled (VMT). Control reductions were then applied as appropriate,
based on category-specific control effectiveness estimates for each
individual measure. The resulting 2026 attainment year inventory was
then provided for each source category and in total.\24\
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\24\ 2023 Five Percent Plan, Appendix B, Exhibit I, pp. III-59-
III-62.
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In developing the emissions inventories, MAG followed the EPA's
2017 EI Guidance and recommendations regarding the use of emission
factors, activity estimates, and control factors, and the other source-
specific inventory development methodologies. The relative accuracy of
each estimate underwent the prescribed quality assurance procedures,
documented in the State's emissions inventory preparation plan.\25\
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\25\ 2023 Five Percent Plan, ``Pinal County PM Inventory
Preparation Plan,'' Report No. SR2013-01-01, prepared by Sierra
Research for the Arizona Department of Environmental Quality,
February 2013.
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The EPA's analysis indicates the inventories are sufficiently
accurate for the purposes of the 2023 Five Percent Plan. Because we
find that the inventory is current, comprehensive, and accurate, we
propose to approve the 2017 PM<INF>10</INF> base year inventory and
2026 attainment year inventory under CAA section 172(c)(3).
B. PM10 Precursors
The provisions of subpart 4 of part D, title I of the CAA do not
define the term ``precursor'' for purposes of PM<INF>10</INF>, nor do
they explicitly require the control of any specific particulate matter
(PM) precursor. The statutory definition of ``air pollutant'' in CAA
section 302(g), however, provides that the term ``includes any
precursors to the formation of any air pollutant, to the extent the
Administrator has identified such precursor or precursors for the
particular purpose for which the term `air pollutant' is used.'' The
EPA has identified sulfur dioxide (SO<INF>2</INF>), oxides of nitrogen
(NO<INF>X</INF>), volatile organic compounds (VOC), and ammonia
(NH<INF>3</INF>) as precursors to the formation of PM.\26\ Accordingly,
a State must include emissions of direct PM and these four precursors
in emissions inventories and must control emissions from sources of all
of these pollutants, unless the State demonstrates to the EPA's
satisfaction that control of one or more of these pollutants is not
needed for expeditious attainment of the NAAQS in the nonattainment
area at issue.
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\26\ See 81 FR 58010, 58018 (Aug. 24, 2016).
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On December 11, 2025, the EPA published a final notice approving
the portion of the Arizona SIP that addresses the CAA section 189(e)
requirement regarding precursor emissions from major stationary sources
of PM<INF>10</INF> for the purpose of nonattainment new source review
in the West Pinal County PM<INF>10</INF> Nonattainment Area.\27\
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\27\ 90 FR 57365 (Dec. 11, 2025).
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Regarding the remaining plan requirements, the 2023 Five Percent
Plan contains a demonstration that precursors do not significantly
contribute to PM<INF>10</INF> exceedances in the West Pinal County
PM<INF>10</INF> Nonattainment Area.\28\ The EPA has evaluated this
demonstration and included a detailed analysis in the West Pinal
PM<INF>10</INF> Modeling Technical Support Document (``EPA's Modeling
TSD'').\29\ The EPA proposes to find that precursors do not
significantly contribute to PM<INF>10</INF> exceedances in the West
Pinal County PM<INF>10</INF> Nonattainment Area, and thus that the area
is not required to regulate
[[Page 66053]]
precursors for the purposes of RACM, BACM, and attainment planning.
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\28\ 2023 Five Percent Plan, Appendix A, Exhibit 1, Attachment
A.
\29\ West Pinal PM<INF>10</INF> Modeling Technical Support
Document, Section 2.9, ``Precursor Demonstration Weight of
Evidence.''
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C. Best Available Control Measures and Reasonably Available Control
Measures Demonstration
CAA section 189(b)(1)(B) requires that Serious area PM<INF>10</INF>
plans provide for the implementation of BACM within four years of
reclassification to Serious.\30\ The EPA has established a process for
evaluating potential BACM (including best available control technology
(BACT)) in Serious areas.\31\ The first step in determining BACM is to
develop a comprehensive emissions inventory of the sources of
PM<INF>10</INF> that can be used with modeling to determine the effects
of these sources on ambient PM<INF>10</INF> levels. Based on our review
of the emission inventories provided in the 2023 Five Percent Plan, the
EPA's analysis indicates that the 2023 Five Percent Plan appropriately
identifies all sources of PM<INF>10</INF> that are subject to
evaluation for potential control consistent with the requirements of
subpart 4 of part D, title I of the Act.
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\30\ As noted in section III.C, because the EPA has not
previously approved an attainment plan for the Moderate area
classification, the EPA is also evaluating the submission against
the RACM requirement.
\31\ Addendum, 42012.
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The remaining steps are to identify potential control measures for
each source category, determine whether available control measures or
technologies are technologically and economically feasible for
implementation in the area, and determine the earliest date by which
those control measures or technologies found to be feasible can be
implemented, in whole or in part. In accordance with these steps, the
significant source categories examined for BACM evaluation in the 2023
Five Percent Plan are: Construction Sites, Cleared Areas, Dairies,
Cattle Concentrated Animal Feeding Operations, Agriculture (Cropland),
Unpaved Roads, Unpaved Lots, and Paved Roads.
We provide a detailed evaluation of the 2023 Five Percent Plan's
control measures for sources in the nonattainment area in the EPA's
``Technical Support Document, EPA Evaluation of BACM, West Pinal County
2023 Five Percent Plan for the 1987 PM-10 NAAQS,'' July 2026 (``EPA's
BACM TSD'').\32\ The EPA notes that its BACM analysis is based on the
rules currently approved in the Pinal County SIP, as well as rules that
the EPA is proposing to approve elsewhere in today's Federal Register--
specifically, regulations addressing fugitive dust and agricultural
best management practices. As described in further detail in EPA's BACM
TSD, we find that the evaluation process followed by MAG in the 2023
Five Percent Plan to identify potential BACM is consistent with the
requirements, the evaluation of potential measures is appropriate, and
reasoned justifications are provided for the rejection of potential
measures based on technological or economic infeasibility.
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\32\ Technical Support Document, EPA Evaluation of BACM, West
Pinal County 2023 Five Percent Plan for the 1987 PM-10 NAAQS.
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For the foregoing reasons, we propose to find that the 2023 Five
Percent Plan provides for the implementation of BACM for all required
sources of PM<INF>10</INF> in accordance with the requirements of CAA
section 189(b)(1)(B).
The EPA does not normally conduct a separate evaluation to
determine whether a Serious area plan's measures also meet the RACM
requirements. However, because in this instance, we have not previously
approved a Moderate area plan as meeting the RACM requirement, we must
evaluate the control strategy for RACM as well. As explained in the
General Preamble Addendum, we interpret the BACM requirement as
generally subsuming the RACM requirement-- i.e., if we determine that
the measures are indeed the ``best available,'' we have necessarily
concluded that they are ``reasonably available.'' \33\ Therefore, we
have not conducted a separate analysis to determine if the measures
represent a RACM level of control, and propose to find that the
measures satisfy the RACM requirement, because our analysis indicates
that they meet the stricter BACM requirement.
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\33\ 59 FR 41998, 42010 (Aug. 16, 1994).
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D. CAA Section 189(d) Attainment Demonstration and Five Percent
Requirement
CAA section 189(d) requires the submittal of plan revisions that
provide for expeditious attainment of the PM<INF>10</INF> NAAQS. The
attainment deadline applicable to an area that fails to attain by the
Serious area attainment date is as soon as practicable, but no later
than five years from the publication date of the notice of a
nonattainment finding unless extended by the EPA as meeting certain
specified requirements.\34\ Because the EPA published the nonattainment
finding for the West Pinal County PM<INF>10</INF> Nonattainment Area on
July 21, 2023, the State must demonstrate attainment no later than July
21, 2028, unless the date is extended.
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\34\ CAA section 179(d)(3).
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1. Attainment Deadline
The 2023 Five Percent Plan models attainment of the PM<INF>10</INF>
NAAQS by December 31, 2026. The 2023 Five Percent Plan contains a
demonstration supporting the conclusion that December 31, 2026, is as
expeditiously as the area can attain the standard. Due to the timeline
for feasible development and implementation of control measures, the
first full year that all control measures relied upon in the plan would
be implemented was 2024. Therefore the 2026 design value, which
includes 2024-2026 data, is the first design value year to include
three years of fully implemented control measures. MAG also notes that
maximum compliance rates will not be achieved until 2026. For these
reasons, the EPA agrees that the submission shows that the area could
not practicably attain the NAAQS prior to December 31, 2026.
2. Modeled Attainment Demonstration
The 2023 Five Percent Plan shows attainment of the PM<INF>10</INF>
NAAQS through modeled attainment demonstrations for three sites (Hidden
Valley, Pinal County Housing, and Stanfield) in the West Pinal County
PM<INF>10</INF> Nonattainment Area.\35\ MAG conducted modeling for
seven design days across the three monitoring sites, representing the
meteorological conditions associated with exceedances in the
nonattainment area.\36\
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\35\ The Plan also contains an unmonitored area analysis for the
region surrounding the Hidden Valley monitor.
\36\ Exceedances of the PM<INF>10</INF> NAAQS have been
associated with three general meteorological scenarios: low wind/
stagnant conditions, elevated wind conditions, and high wind dust
events. MAG selected design days that would likely not be considered
high wind dust events (i.e., the geographic extent of the
exceedances did not suggest the occurrence of an area-wide storm
event, resulting in emissions that could not be reasonably
controlled).
[[Page 66054]]
Table 1--Design Days Selection
----------------------------------------------------------------------------------------------------------------
24-hour
PM10
Monitor Date ([micro]g/ Exceedance type
m\3\)
----------------------------------------------------------------------------------------------------------------
Hidden Valley (AQS ID: 04-021-3015)...... June 15, 2017.............. 251 Low Wind.
July 6, 2018............... 261 Elevated Wind (Low
Pressure).
August 28, 2017............ 222 Elevated Wind
(Thunderstorm).
October 7, 2017............ 229 Low Wind.
Pinal County Housing (AQS ID: 04-021- December 1, 2017........... 185 Low Wind.
3011).
Stanfield (AQS ID: 04-021-3008).......... June 18, 2016.............. 171 Low Wind.
July 6, 2018............... 193 Elevated Wind (Low
Pressure).
July 16, 2016.............. 209 Elevated Wind
(Thunderstorm).
----------------------------------------------------------------------------------------------------------------
The methods used for modeling the design days are consistent with
EPA guidance.<SUP>37 38</SUP> The results of the modeling demonstrate
that the emission reductions in the plan are expected to result in
PM<INF>10</INF> levels that provide for attainment of the NAAQS by
December 31, 2026. The EPA notes that preliminary ambient air quality
data for the area suggest that the control strategy may not have
achieved reductions at the levels predicted in the Plan. The EPA has
not identified deficiencies in the modeling, or in the substantive
requirements contained in the rules that constitute the control
strategy that would cause this discrepancy. However, the EPA has
previously noted that an earlier version of the AgBMP rules, which
regulate sources that predominate in the area surrounding the design
value monitor, may not have contained implementation requirements
sufficient to achieve the level of compliance predicted in the
Plan.\39\ The State has updated the AgBMP rules, substantially
strengthening the enforceability of the rules in a manner that the EPA
expects will result in reductions in line with those modeled in the
Plan.\40\ Therefore, the EPA proposes to find that the 2023 Five
Percent Plan's attainment demonstration adequately demonstrates
attainment of the PM<INF>10</INF> standard in the West Pinal County
PM<INF>10</INF> Nonattainment Area. The EPA's detailed analysis of the
modeling can be found in EPA's Modeling TSD for this action.
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\37\ 40 CFR part 51, Appendix W.
\38\ PM10 SIP Development Guideline (June 1987). EPA-450/2-86-
001.
\39\ See 86 FR 1347, 1358 (Jan. 8, 2021).
\40\ The revisions to the AgBMP rules are described in a
separate rulemaking that the EPA is proposing in today's Federal
Register. The EPA also notes that EPA delays in adding the submitted
rules to the SIP have delayed the Federal enforceability of the
rules and thus possibly the rate of compliance. The EPA's parallel
proposal to add these updated rules to the Arizona SIP is also
expected to help bring emission levels into line with those
predicted in the modeling.
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3. Five Percent Requirement
Under CAA section 189(d), the SIP revision submitted by the State
must provide for an annual reduction in PM<INF>10</INF> or
PM<INF>10</INF> precursor emissions of not less than five percent from
the date of such submission until attainment. The 2023 Five Percent
Plan's demonstration of annual five percent reductions is found in
Chapter 6. MAG used the 2017 PM<INF>10</INF> Inventory as the baseline
inventory and derived emissions levels for years 2017-2027 based on the
2017 PM<INF>10</INF> Inventory.\41\ The demonstration of annual five
percent reductions uses 2024 as the point at which the reductions
should start.\42\ Since the plan demonstrates attainment by December
31, 2026, annual five percent reductions are shown for three years:
2024, 2025, and 2026. The 2023 Five Percent Plan's demonstration is
summarized in Table 2 of this document.
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\41\ 2023 Five Percent Plan, Chapter 6, p. 6-1.
\42\ Id. The EPA notes that ADEQ submitted the 2023 Five Percent
Plan on December 14, 2023. Because CAA section 189(d) states that
the reductions should be shown ``from the date of such submission
until attainment,'' the Plan should show the five percent reductions
beginning on that date. However, the EPA finds that showing
reductions beginning in 2024 is sufficient. First, the amount of
time between submission and the beginning of the reduction period is
minimal--less than three weeks. Second, the emission inventories
used to calculate the reductions are generally on a calendar year
basis. Accordingly, the EPA believes it was reasonable to wait until
the turn of the calendar year, given the short amount of time
between the dates. Third, the submitted analysis shows excess
reductions that more than account for the small amount of reductions
that would be required in a small pro-rated portion of 2023 that
remained at the time of submission. See Table 2 of this document.
And fourth, the State could have waited until the turn of the year
to submit the Plan to avoid needing to account for these days in
late 2023, and the EPA does not agree that it is appropriate to
provide an incentive for the State to delay plan submittal. The EPA
has articulated, in the context of the CAA section 189(d)
requirements for PM<INF>2.5,</INF> that it is sufficient to show
reductions from the due date of the CAA section 189(d) plan. The EPA
has noted that this prevents States making late submissions from
avoiding the requirement to achieve reductions for the timeframe of
the delay. See 81 FR 58010, 58101; 86 FR 53150, 53166 (Sep. 24,
2021).
Table 2--2023 Five Percent Plan Emissions by Year
----------------------------------------------------------------------------------------------------------------
Year 2024 2025 2026
----------------------------------------------------------------------------------------------------------------
2017 Baseline Inventory (tons).................................. 41,168 41,168 41,168
Five Percent Annual Requirement (tons).......................... 2,058 2,058 2,058
Five Percent Cumulative Reduction (tons)........................ 2,058 4,117 6,175
2017 Base PM10 Emissions Minus Five Percent Annual Reductions 39,110 37,051 34,993
(tons).........................................................
Projected Annual PM10 Emissions with BACM Implementation (tons). 35,901 35,248 34,016
Excess Benefit = Total PM10 Emissions Reductions Minus Five 3,209 1,803 977
Percent Reductions (tons)......................................
----------------------------------------------------------------------------------------------------------------
The ``2017 Baseline Inventory (tons)'' values are derived from the
2017 PM<INF>10</INF> Inventory. The ``Five Percent Annual Requirement
(tons)'' values indicate the annual five percent reduction target as
calculated by multiplying the total ``2017 Baseline Inventory (tons)''
(41,168 tons) by five percent, resulting in a value of 2,058 tons. The
``Five Percent Cumulative Reduction (tons)'' indicate the cumulative
yearly
[[Page 66055]]
reductions, increasing by five percent of the 2017 Baseline Inventory
each year.
The ``2017 Base PM<INF>10</INF> Emissions Minus Five Percent Annual
Reductions (tons)'' values are calculated as the ``2017 Baseline
Inventory (tons)'' minus the ``Five Percent Annual Requirement
(tons),'' representing the maximum total emission in tons that could be
emitted each year to meet the five percent requirement. The ``Projected
Annual PM<INF>10</INF> Emissions with BACM Implementation (tons)''
values are the projected actual emissions between 2024 and 2026
reflecting the implementation of control measures. The ``Excess Benefit
= Total PM<INF>10</INF> Emissions Reductions Minus Five Percent
Reductions (tons)'' indicates the surplus of cumulative emissions
reductions each year beyond the five percent requirement.
The 2023 Five Percent Plan demonstrates compliance with the five
percent reduction requirement by comparing the cumulative reductions
against the total five percent reduction values each year and shows
that the reductions exceed the five percent per year requirement. Most
of the required reductions were achieved in the early years of the
plan. The EPA encourages this approach as it accelerates the
environmental benefits of the reductions.\43\ Because the 2023 Five
Percent Plan demonstrates that the area will achieve the requisite
reductions from 2024 until the modeled attainment date in 2026, the EPA
proposes to find that Plan meets the CAA section 189(d) five percent
requirement.
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\43\ This approach is consistent with the approach taken in
previous actions involving CAA section 189(d) plans for the San
Joaquin Valley, California and Maricopa County, Arizona. See 69 FR
5411 (Feb. 4, 2004), 69 FR 30006 (May 26, 2004), 79 FR 7118 (Feb. 6,
2014) and 79 FR 33107 (June 10, 2014).
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E. Reasonable Further Progress and Quantitative Milestones
Pursuant to CAA sections 172(c)(2) and 189(c)(1), the State must
demonstrate RFP in the 2023 Five Percent Plan. We have explained in
guidance that for areas such as the West Pinal County PM<INF>10</INF>
Nonattainment Area where ``the nonattainment problem is attributed to
area type sources (e.g., fugitive dust, etc.), RFP should be met by
showing annual incremental emission reductions sufficient generally to
maintain linear progress towards attainment. Total PM<INF>10</INF>
emissions should not remain constant or increase from 1 year to the
next in such an area.'' \44\ Further, we have stated that, ``in
reviewing the SIP, EPA will determine whether the annual incremental
emission reductions to be achieved are reasonable in light of the
statutory objective to ensure timely attainment of the PM<INF>10</INF>
NAAQS.'' \45\
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\44\ Addendum, 42015.
\45\ Id. at 42016.
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CAA section 189(c) further requires PM<INF>10</INF> attainment
plans to contain quantitative milestones that are to be achieved every
three years and that demonstrate RFP for the area. These quantitative
milestones should consist of elements that allow RFP to be quantified
or measured objectively. Specifically, States should identify and
submit quantitative milestones that allow for evaluation of whether the
plan is achieving emissions reductions adequate to attain the NAAQS by
the applicable attainment date.\46\
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\46\ Id.
---------------------------------------------------------------------------
The 2023 Five Percent Plan includes an RFP demonstration in Chapter
9.\47\ This analysis uses the 2017 inventory totals by year as shown in
Table 2 of this document. Specifically, the 2023 Five Percent Plan
shows the following levels of PM<INF>10</INF>, which decline between
2022 and 2027, with BACM control implementation in Table 3 below.
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\47\ 2023 Five Percent Plan, Chapter 9, Attainment
Demonstration, pp. 9-17-9-27.
Table 3--Annual PM10 Emissions
------------------------------------------------------------------------
Year Tons
------------------------------------------------------------------------
2022.................................................... 37,614
2023.................................................... 37,563
2024.................................................... 35,901
2025.................................................... 35,248
2026.................................................... 34,016
2027.................................................... 33,629
------------------------------------------------------------------------
The analysis required for the five percent demonstration provides
annual emission targets between 2024 and the attainment year of 2026.
These annual totals show a steady downward trend in emissions that
fulfills the milestone requirement of every three years.\48\ The trend
is more sharply downward in 2024 due to the implementation schedule of
control measures. The EPA proposes to find that the 2023 Five Percent
Plan has demonstrated RFP and that by setting annual target emission
levels, the plan has met the requirement to provide for milestones
every three years.
---------------------------------------------------------------------------
\48\ 2023 Five Percent Plan, Chapter 9, Attainment
Demonstration, pg. 9-27.
---------------------------------------------------------------------------
F. Contingency Measures
CAA section 172(c)(9) requires that attainment plans provide for
the implementation of specific measures to be undertaken if the area
fails to meet RFP requirements or fails to attain the PM<INF>10</INF>
standard as projected in the plan. That section further requires that
such measures are to take effect in any such case without further
action by the State or the EPA. The CAA does not specify how many
contingency measures are necessary nor does it specify the level of
emission reductions they must achieve.
The purpose of contingency measures is to continue progress in
reducing emissions while a State revises its SIP to meet the missed RFP
milestone or to develop a new plan demonstrating attainment of the
NAAQS. Contingency measures must consist of measures that the State is
not otherwise relying on to meet other attainment plan requirements in
the area. Thus, these additional emission reductions that will be
achieved by the contingency measures ensure continued progress towards
attainment while the State is revising the SIP to correct the failure
to meet RFP or to attain.
In interpreting the requirement that the contingency measures must
``take effect without further action by the State or the
Administrator,'' the General Preamble provides the following general
guidance: ``[s]tates must show that their contingency measures can be
implemented with minimal further action on their part and with no
additional rulemaking actions such as public hearings or legislative
review.'' Further, ``[i]n general, EPA will expect all actions needed
to affect full implementation of the measures to occur within 60 days
after EPA notifies the State of its failure.''
In December 2024, the EPA released the ``Guidance on the
Preparation of State Implementation Plan Provisions that Address the
Nonattainment Area Contingency Measure Requirements for Ozone and
Particulate Matter (December 3, 2024)'' (``Revised Contingency Measure
Guidance'').\49\ This guidance primarily relates to the EPA's
recommendations concerning the specific amount of emissions reductions
that implementation of contingency
[[Page 66056]]
measures should achieve and the timing for when the emissions
reductions from the contingency measures should occur.
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\49\ The EPA announced the availability of the guidance document
at 89 FR 101602 (Dec. 16, 2024). A copy of the guidance document
itself is available in the docket for this action. The EPA had
previously released a draft of this document, ``Draft: Guidance on
the Preparation of State Implementation Plan Provisions that Address
the Nonattainment Area Contingency Measure Requirements for Ozone
and Particulate Matter (DRAFT--3/17/23--Public Review Version)''
(``Draft Revised Contingency Measure Guidance''). The EPA published
a notice of availability for the Draft Revised Contingency Measure
Guidance at 88 FR 17571 (Mar. 23, 2023). The Revised Contingency
Measure Guidance that the EPA finalized in December 2024 is
consistent with the guidance set forth in the Draft Revised
Contingency Measure Guidance that the EPA released in March 2023.
---------------------------------------------------------------------------
Prior to the release of the Revised Contingency Measure Guidance,
the EPA's recommendation for the amount of emissions reductions to
achieve from implementation of contingency measures was one year's
worth of RFP. For PM<INF>10</INF>, prior EPA guidance recommended that
RFP should represent generally linear progress towards attainment
(i.e., the difference between the attainment projected inventory \50\
and the base year emissions inventory, divided by the number of years
between the base year and the attainment year).\51\
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\50\ The term ``attainment projected inventory'' is described
further in Section 3.8.1 (for ozone) and Section 3.8.2 (for
particulate matter) of the EPA's ``Emissions Inventory Guidance for
Implementation of Ozone and Particulate Matter NAAQS and Regional
Haze Regulations.'' See <a href="https://www.EPA.gov/air-emissions-inventories/air-emissions-inventory-guidance-implementation-ozone-and-particulate">https://www.EPA.gov/air-emissions-inventories/air-emissions-inventory-guidance-implementation-ozone-and-particulate</a>.
\51\ 59 FR 41998, 42015 (Aug. 16, 1994).
---------------------------------------------------------------------------
The Revised Contingency Measure Guidance introduces ``one year's
worth of progress,'' a metric intended to be more closely tied to the
emissions reductions required for attainment of the NAAQS, for
determining the amount of emissions reductions that contingency
measures should achieve. One year's worth of ``progress'' is calculated
by determining the average annual reductions between the base year
emissions inventory and the projected attainment year emissions
inventory, determining what percentage of the base year emissions
inventory this amount represents, and then applying that percentage to
the projected attainment year emissions inventory to determine the
amount of reductions needed to ensure ongoing progress if contingency
measures are triggered.\52\
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\52\ See Chapter 3 of the Revised Contingency Measure Guidance.
---------------------------------------------------------------------------
The 2023 Five Percent Plan identified one adopted contingency
measure of a speed limit reduction on public unpaved roads. This
contingency measure is PCAQCD Rule 4-1-030.6.C, which the State
submitted to the EPA for approval into the SIP on February 13, 2023.
The measure would require owners or operators of unpaved public roads
of 26 annual average daily traffic or more to establish a speed limit
of 15 miles per hour in the event that the area fails to make RFP or
fails to attain the PM<INF>10</INF> NAAQS by the attainment date.\53\
The EPA is proposing to approve Rule 4-1-030.6.C in a separate notice
in today's Federal Register. While that rulemaking action evaluates the
approvability of the rule into the SIP, in this action we evaluate
whether the contingency provision in that rule satisfies the
contingency measure planning requirement for the PM<INF>10</INF> NAAQS
associated with the submitted plan.
---------------------------------------------------------------------------
\53\ 2023 Five Percent Plan, Chapter 9, Attainment
Demonstration, pp. 9-28-9-29.
---------------------------------------------------------------------------
If the EPA finalizes the measure's approval into the SIP, our
analysis indicates that the measure meets all relevant requirements to
satisfy the contingency measure requirement for the PM<INF>10</INF>
NAAQS. The measure has been fully adopted and will be triggered upon an
EPA finding that the area has failed to attain the NAAQS by the
applicable attainment date or has failed to meet the RFP requirement.
The measure goes into effect immediately upon such a finding, with no
additional action required by the State. In addition, the method used
to estimate emissions reductions from this contingency measure is
consistent with the EPA's recommended calculation methods for such
measures, and the total reductions exceed the target of one year's
worth of progress.\54\ Because it meets all applicable requirements,
the EPA proposes to approve the contingency measure element described
in the 2023 Five Percent Plan.
---------------------------------------------------------------------------
\54\ As explained in the 2023 Five Percent Plan, the contingency
measure is expected to generate 950.81 tons of reductions. The
threshold for one year's worth of progress is 657 tons. Thus, the
measure is sufficient to achieve the quantity of reductions
indicated in the EPA's Revised Contingency Measure Guidance. The EPA
notes that under the previously suggested method for calculating
contingency measure reductions (one year's worth of RFP), the value
would be 795 tons. The measure thus achieves sufficient reductions
under both previous and current EPA guidance.
---------------------------------------------------------------------------
G. Transportation Conformity and Motor Vehicle Emissions Budgets
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 (MPOs)
in nonattainment and maintenance areas coordinate with State and local
air quality and transportation agencies, the EPA, the FHWA, and the FTA
to determine that an area's regional transportation plans and
transportation improvement programs conform to the applicable SIP. This
determination typically includes a showing that estimated emissions
from existing and planned highway and transit systems are less than or
equal to the budgets that the EPA has found adequate or approved in the
area's control strategy SIP.\55\ Budgets are generally established for
specific years and specific pollutants or precursors. Attainment plans
for PM<INF>10</INF> nonattainment areas should identify budgets for on-
road mobile source emissions of PM<INF>10</INF>, i.e., vehicle
emissions and fugitive dust emissions, in the area for each RFP
milestone year, as appropriate, and the attainment year, if the plan
demonstrates attainment.\56\
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\55\ See definition of ``control strategy implementation plan
revision'' at 40 CFR 93.101.
\56\ 40 CFR 93.102(b)(1).
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For budgets to be approvable, they must meet, at a minimum, the
EPA's adequacy criteria at 40 CFR 93.118(e)(4). While we have not yet
made an adequacy finding, the EPA is starting the adequacy process with
this notice and as such, the EPA is also proposing to approve the
budgets based on these criteria. To meet these requirements, the
budgets must be consistent with the attainment and RFP requirements and
reflect all the motor vehicle control measures contained in the
attainment and RFP demonstrations.\57\
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\57\ 40 CFR 93.118(e)(4)(iii), (iv) and (v). For more
information on the transportation conformity requirements and
applicable policies on budgets, please visit our transportation
conformity website at: <a href="https://www.epa.gov/state-and-local-transportation/transportation-conformity">https://www.epa.gov/state-and-local-transportation/transportation-conformity</a>.
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The EPA's process for determining the 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.\58\ During the comment period for this notice,
the public can comment on the adequacy of the budgets in addition to
other aspects of this proposed rule.
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\58\ 40 CFR 93.118(f)(2).
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The 2023 Five Percent Plan specifies the maximum transportation-
related PM<INF>10</INF> emissions for the RFP milestone year of 2023,
and for the RFP milestone and attainment year of 2026. The State's
submitted 2023 and 2026 budgets for PM<INF>10</INF> are included in
Table 4 of this document. These budgets include emissions from vehicle
exhaust, tire wear, brake wear, road construction, re-entrained dust
from vehicles traveling on paved roads, and fugitive dust generated
from vehicles traveling on public unpaved and private non-agricultural
\59\ unpaved roads.
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\59\ Unpaved, private, non-agricultural roads have been included
as an emission source category in the motor vehicle emissions
budgets as they are generally accessible and used by the public.
Conversely, unpaved, private, agricultural roads are primarily used
to access irrigation canals or farm fields and are not included as a
category in the motor vehicle emissions budgets because they are not
generally accessed or used by the public.
[[Page 66057]]
Table 4--Motor Vehicle Emissions Budgets for the West Pinal County PM10
Nonattainment Area
[Metric tons/day]
------------------------------------------------------------------------
Source 2023 2026
------------------------------------------------------------------------
Exhaust, tire wear, and brake wear...... 0.4 0.3
Paved road dust......................... 2.6 2.5
Road construction....................... 0.5 0.4
Unpaved public roads.................... 15.9 14.1
Unpaved (non-agricultural) private roads 25.7 25.2
-------------------------------
Total............................... 45.0 42.5
------------------------------------------------------------------------
Source: 2023 Five Percent Plan, Table 9-8.
The methodologies MAG used to develop the budgets are provided in
Chapter 9 and Appendix B, Exhibit 1 of the 2023 Five Percent Plan.\60\
MAG used MOVES3 in the development of these budgets; this emissions
factor model was the latest EPA-approved version at the time the 2023
Five Percent Plan was developed.\61\ Annual emission estimates from
road construction were developed from calculations provided by PCAQCD,
published emission factors for construction, and local data inputs.\62\
MAG used the most recently approved EPA-provided AP-42 emissions factor
equations to develop paved and unpaved road fugitive dust emissions
estimates.\63\ Paved road vehicle miles traveled (VMT) estimates for
estimating direct and fugitive PM<INF>10</INF> emissions were provided
by MAG for 2026, and estimated for 2023 using an interpolation of the
2017 base year VMT.\64\ Unpaved public road VMT estimates for
estimating fugitive PM<INF>10</INF> emissions were interpolated from
the 2017 base year VMT.\65\ Unpaved private non-agricultural VMT
estimates for estimating fugitive PM<INF>10</INF> were held constant
from the 2017 base year VMT estimates.\66\
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\60\ Chapter 9, pp. 9-31-9-34, and Appendix B, Exhibit 1,
Chapter III, pp. II-10-II-12.
\61\ The MOtor Vehicle Emission Simulator model, ``MOVES3'' was
used to calculate 2026 annual and daily PM<INF>10</INF> emissions
from exhaust, tire wear, and brake wear; 2023 PM<INF>10</INF> annual
emissions from exhaust, tire wear, and brake wear were interpolated
between MOVES3 runs for the 2017 base year and the 2026 attainment
year.
\62\ See Appendix A, Exhibit 1 of the 2023 Five Percent Plan for
more details on the calculations and inputs used. Uncontrolled
annual road construction emissions were calculated for 2017 and then
grown by population to 2023 and 2026.
\63\ MAG 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 road
fugitive dust emissions can be found in Appendix A, Exhibit 1 of the
2023 Five Percent Plan. The AP-42 emission factor equation inputs
for estimating unpaved road fugitive dust emissions can be found in
Appendix A, Exhibit 1 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 (Feb. 4,
2011).
\64\ 2023 Five Percent Plan, pp. 9-20 and 9-33. The
interpolation methodology for 2023 VMT is based on the rate of paved
road VMT increases between the 2017 base year and the 2026
attainment year.
\65\ See p. 9-34 of the 2023 Five Percent Plan. 2023 and 2026
VMT estimates for unpaved public roads were grown from 2017 VMT
based upon the rate at which low-arterial paved road vehicle miles
traveled increases as estimated by MAG travel demand models, as
reliable VMT estimates on unpaved roads were not available.
\66\ See p. 9-34 of the 2023 Five Percent Plan. VMT usage on
private unpaved roads is very low and estimated as under 25 trips
per day.
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We are proposing to approve the budgets for 2023 and 2026 as part
of our approval of the 2023 Five Percent Plan. The EPA has determined
that the 2023 and 2026 motor vehicle emissions budgets are consistent
with emission control measures in the SIP and the attainment
demonstration, five percent demonstration, and RFP demonstration. The
details of the EPA's evaluation of the budgets for compliance with the
budget adequacy criteria of 40 CFR 93.118(e) is provided in a separate
document included in the docket for this rulemaking.\67\ If we find the
budgets adequate or finalize approval of the budgets in the 2023 Five
Percent Plan as proposed, then these budgets must be used in future
transportation conformity analyses for the West Pinal County
PM<INF>10</INF> Nonattainment Area.\68\
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\67\ Memorandum dated June 29, 2026, from Lindsay Wickersham,
EPA, to Rulemaking Docket EPA-R09-OAR-2026-5119, Subject: Adequacy
Documentation for Motor Vehicle Emission Budgets in 2023 Five
Percent Plan.
\68\ See 40 CFR 93.109(c).
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H. Adequate Legal Authority
CAA section 110(a)(2)(E)(i) requires that implementation plans
provide necessary assurances that the State (or the local government in
the case of delegation) will have adequate personnel, funding and
authority under State law. Requirements for legal authority are further
defined in 40 CFR part 51, subpart L (sections 51.230-51.232) and for
resources in 40 CFR 51.280.
States and responsible local agencies must demonstrate that they
have the legal authority to adopt and enforce provisions of the SIP and
to obtain information necessary to determine compliance. These
requirements are addressed in the cover letters and submittal package
for the 2023 Five Percent Plan.\69\
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\69\ Letter dated December 13, 2023, from Hether Krause, Deputy
Director, Air Quality Division, ADEQ, to Martha Guzman, Regional
Administrator, EPA Region IX, Subject: ``Arizona State
Implementation Plan Revision, Maricopa Association of Governments
2023 Five Percent Particulate Plan for PM-10 For the West Pinal
County Nonattainment Area.''
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MAG derives its authority to develop and adopt air quality plans,
including the 2023 Five Percent Plan, from Arizona Revised Statute
(ARS) 49-406 and from a June 22, 2016 letter from the Governor of
Arizona designating MAG as responsible for those tasks.\70\ ADEQ is
authorized to adopt and submit the 2023 Five Percent Plan by ARS 49-404
and ARS 49-406. PCAQCD implements air quality programs within Pinal
County.
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\70\ Letter from Douglas A. Ducey, Governor, to Alexis Strauss,
Acting Regional Administrator, EPA Region IX, Subject: ``Re:
Certification of Maricopa Association of Governments and Pima
Association of Governments as Lead Planning Organizations under
Clean Air Act Sec. 174(a) and A.R.S. Sec. 49-406(A).'' 2023 Five
Percent Plan, Appendix D, Exhibit II.
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For the reasons discussed above, we propose to find that the
requirements of CAA section 110(a)(2)(E) and related regulations have
been met with respect to legal authority.
V. Summary of Proposed Actions
The EPA is proposing to approve the CAA section 189(d) plan for the
West Pinal County PM<INF>10</INF> Nonattainment Area as meeting all
relevant Moderate, Serious, and CAA section 189(d) requirements.
Specifically, we propose to approve the following:
(1) The 2017 baseline emissions inventory and the attainment year
emission inventories as meeting the requirements of CAA section
172(c)(3);
[[Page 66058]]
(2) the BACM demonstration as meeting the requirements of CAA
section 189(b)(1)(B), and the RACM demonstration as meeting the
requirements of CAA sections 189(a)(1)(C) and 172(c)(1);
(3) the attainment demonstration as meeting the requirements of CAA
sections 189(d) and 179(d)(3), with an attainment date of December 31,
2026;
(4) the five percent demonstration as meeting the requirements of
CAA section 189(d);
(5) the reasonable further progress and quantitative milestone
demonstrations as meeting the requirements of CAA sections 172(c)(2)
and 189(c);
(6) the contingency measure as meeting the requirements of CAA
section 172(c)(9); and
(7) the motor vehicle emissions budgets, as they meet the criteria
for budgets in CAA section 176(c) and 40 CFR 93.118(e)(4).
The EPA is also starting the adequacy process for these budgets.
VI. Statutory and Executive Order Reviews
Under the CAA, the Administrator is required to approve a SIP
submission that complies with the provisions of the Act and applicable
Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in
reviewing SIP submissions, the EPA's role is to approve State choices,
provided that they meet the criteria of the CAA. Accordingly, this
proposed action merely proposes to approve State law as meeting Federal
requirements and does not impose additional requirements beyond those
imposed by State law. For that reason, this proposed action:
<bullet> Is not a significant regulatory action subject to review
by the Office of Management and Budget under Executive Order 12866 (58
FR 51735, Oct. 4, 1993);
<bullet> Is not an Executive Order 14192 (90 FR 9065, Feb. 6, 2025)
regulatory action because this action is not significant under
Executive Order 12866;
<bullet> Does not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
<bullet> Is certified as not having a significant economic impact
on a substantial number of small entities under the Regulatory
Flexibility Act (5 U.S.C. 601 et seq.);
<bullet> Does not contain any unfunded mandate or significantly or
uniquely affect small governments, as described in the Unfunded
Mandates Reform Act of 1995 (Pub. L. 104-4);
<bullet> Does not have federalism implications as specified in
Executive Order 13132 (64 FR 43255, Aug. 10, 1999);
<bullet> Is not subject to Executive Order 13045 (62 FR 19885, Apr.
23, 1997) because it proposes to approve a State program;
<bullet> Is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001); and
<bullet> Is not subject to requirements of section 12(d) of the
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272
note) because application of those requirements would be inconsistent
with the CAA.
In addition, the SIP is not approved to apply on any Indian
reservation land or in any other area where the EPA or an Indian Tribe
has demonstrated that a Tribe has jurisdiction. In those areas of
Indian country, the rule does not have Tribal implications and will not
impose substantial direct costs on Tribal governments or preempt Tribal
law as specified by Executive Order 13175 (65 FR 67249, Nov. 9, 2000).
List of Subjects in 40 CFR Part 52
Environmental protection, Air pollution control, Incorporation by
reference, Intergovernmental relations, Particulate matter, Reporting
and recordkeeping requirements.
Authority: 42 U.S.C. 7401 et seq.
Dated: October 14, 2026.
Michael Martucci,
Acting Regional Administrator, Region IX.
[FR Doc. 2026-21288 Filed 10-16-26; 8:45 am]
BILLING CODE 6569-60-P
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This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.