[Federal Register Volume 89, Number 106 (Friday, May 31, 2024)]
[Proposed Rules]
[Pages 47398-47438]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-11807]



[[Page 47397]]

Vol. 89

Friday,

No. 106

May 31, 2024

Part III





 Environmental Protection Agency





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40 CFR Part 52





Partial Approval and Disapproval of Air Quality Implementation Plans; 
Arizona; Regional Haze State Implementation Plan for the Second 
Implementation Period and Prong 4 (Visibility) for the 2015 Ozone and 
2012 Particulate Matter Standards; Proposed Rule

  Federal Register / Vol. 89 , No. 106 / Friday, May 31, 2024 / 
Proposed Rules  

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2024-0005; FRL-11919-01-R9]


Partial Approval and Disapproval of Air Quality Implementation 
Plans; Arizona; Regional Haze State Implementation Plan for the Second 
Implementation Period and Prong 4 (Visibility) for the 2015 Ozone and 
2012 Particulate Matter Standards

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
partially approve and partially disapprove the regional haze state 
implementation plan (SIP) revision submitted by Arizona on August 15, 
2022 (``2022 Arizona Regional Haze Plan''), under the Clean Air Act 
(CAA) and the EPA's Regional Haze Rule for the program's second 
implementation period. Arizona's SIP submission addresses the 
requirement that states must periodically revise their long-term 
strategies for making reasonable progress towards the national goal of 
preventing any future, and remedying any existing, anthropogenic 
impairment of visibility, including regional haze, in mandatory Class I 
Federal areas. The SIP submission also addresses other applicable 
requirements for the second implementation period of the regional haze 
program. Within this action, the EPA is also proposing to disapprove 
the visibility transport prong of Arizona's infrastructure SIP 
submittals for the 2012 annual fine particulate matter 
(PM2.5) and 2015 ozone National Ambient Air Quality 
Standards (NAAQS). The EPA is taking this action pursuant to CAA 
sections 110 and 169A.

DATES: Written comments must be received on or before July 1, 2024.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2024-0005 at https://www.regulations.gov. For comments submitted at 
Regulations.gov, follow the online instructions for submitting 
comments. Once submitted, comments cannot be edited or removed from 
Regulations.gov. The EPA may publish any comment received to its public 
docket. Do not submit electronically any information you consider to be 
confidential business information (CBI) or other information whose 
disclosure is restricted by statute. Multimedia submissions (audio, 
video, etc.) must be accompanied by a written comment. The written 
comment is considered the official comment and should include 
discussion of all points you wish to make. The EPA will generally not 
consider comments or comment contents located outside of the primary 
submission (i.e., on the web, cloud, or other file sharing system). For 
additional submission methods, please contact the person identified in 
the FOR FURTHER INFORMATION CONTACT section. For the full EPA public 
comment policy, information about CBI or multimedia submissions, and 
general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. If you need assistance in a 
language other than English or if you are a person with a disability 
who needs a reasonable accommodation at no cost to you, please contact 
the person identified in the FOR FURTHER INFORMATION CONTACT section.

FOR FURTHER INFORMATION CONTACT: Khoi Nguyen, Geographic Strategies & 
Modeling Section (AIR-2-2), Planning & Analysis Branch, EPA Region IX, 
75 Hawthorne Street, San Francisco, CA 94105, (415) 947-4120, or by 
email at [email protected].

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

Table of Contents

I. What action is the EPA proposing for regional haze?
II. Background and Requirements for Regional Haze Plans
    A. Regional Haze Background
    B. Roles of Agencies in Addressing Regional Haze
III. Requirements for Regional Haze Plans for the Second 
Implementation Period
    A. Identification of Class I Areas
    B. Calculations of Baseline, Current, and Natural Visibility 
Conditions; Progress to Date; and the Uniform Rate of Progress
    C. Long-Term Strategy for Regional Haze
    D. Reasonable Progress Goals
    E. Monitoring Strategy and Other State Implementation Plan 
Requirements
    F. Requirements for Periodic Reports Describing Progress Towards 
the Reasonable Progress Goals
    G. Requirements for State and Federal Land Manager Coordination
IV. The EPA's Evaluation of Arizona's Regional Haze Submission for 
the Second Implementation Period
    A. Background on Arizona's First Implementation Period SIP 
Submission
    B. Overview of Arizona's Second Implementation Period SIP 
Submission
    C. Identification of Class I Areas
    D. Calculations of Baseline, Current, and Natural Visibility 
Conditions; Progress to Date; and the Uniform Rate of Progress
    E. Long-Term Strategy for Regional Haze
    1. Arizona's Long-Term Strategy in the 2022 Arizona Regional 
Haze Plan
    2. The EPA's Evaluation of Arizona's Long-Term Strategy
    F. Reasonable Progress Goals
    G. Additional Monitoring To Assess Reasonably Attributable 
Visibility Impairment
    H. Monitoring Strategy and Other Implementation Plan 
Requirements
    I. Requirements for Periodic Reports Describing Progress Towards 
the Reasonable Progress Goals
    J. Requirements for State and Federal Land Manager Coordination
V. Prong 4 (Visibility) of the 2012 PM2.5 NAAQS and 2015 
Ozone NAAQS Infrastructure SIPs
    A. Infrastructure SIPs
    B. Prong 4 Requirements
    1. 2012 PM2.5 NAAQS
    2. 2015 Ozone NAAQS
    C. Arizona's Prong 4 Elements
    D. The EPA's Evaluation of Arizona's Submittal
VI. Proposed Action
VII. Statutory and Executive Order Reviews

I. What action is the EPA proposing for regional haze?

    On August 15, 2022,\1\ the Arizona Department of Environmental 
Quality (ADEQ) submitted the 2022 Arizona Regional Haze Plan. ADEQ 
supplemented its SIP revision on August 25, 2023, with nonpoint source 
rules (``2023 Arizona Regional Haze Rules Supplement'').\2\ ADEQ made 
these SIP submissions to satisfy requirements of the CAA's regional 
haze program pursuant to CAA sections 169A and 169B and 40 CFR 51.308. 
The EPA is proposing to partially approve and partially disapprove the 
2022 Arizona Regional Haze Plan. For the reasons described in this 
document, the EPA is proposing to approve the elements of the 2022 
Arizona Regional Haze Plan related to requirements contained in 40 CFR 
51.308(f)(1), (f)(4)-(6), and (g)(1)-(5). The EPA is proposing to 
disapprove the elements of the 2022 Arizona Regional Haze Plan related 
to requirements contained in 40 CFR 51.308(f)(2), (f)(3), and (i)(2)-
(4). We are

[[Page 47399]]

not proposing to act on the 2023 Arizona Regional Haze Rules Supplement 
at this time.
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    \1\ Letter dated August 15, 2022, from Daniel Czecholinski, 
Director, Arizona Department of Environmental Quality Air Quality 
Division, to Martha Guzman, Regional Administrator, EPA Region IX 
(submitted electronically August 15, 2022). On August 16, 2022, the 
EPA determined that the SIP submittal met the completeness criteria 
outlined in 40 CFR part 51, Appendix V. Letter dated August 16, 
2022, from Elizabeth Adams, Director, Air and Radiation Division, 
EPA Region IX, to Daniel Czecholinski, Director, Arizona Department 
of Environmental Quality Air Quality Division.
    \2\ Letter dated August 21, 2023, from Daniel Czecholinski, 
Director, Arizona Department of Environmental Quality Air Quality 
Division, to Martha Guzman, Regional Administrator, EPA Region IX 
(submitted electronically August 25, 2023).
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II. Background and Requirements for Regional Haze Plans

A. Regional Haze Background

    In the 1977 CAA Amendments, Congress created a program for 
protecting visibility in the nation's mandatory Class I Federal areas, 
which include certain national parks and wilderness areas.\3\ The CAA 
establishes as a national goal the ``prevention of any future, and the 
remedying of any existing, impairment of visibility in mandatory class 
I Federal areas which impairment results from manmade air pollution.'' 
\4\ The CAA further directs the EPA to promulgate regulations to assure 
reasonable progress toward meeting this national goal.\5\ On December 
2, 1980, the EPA promulgated regulations to address visibility 
impairment in mandatory Class I Federal areas (hereinafter referred to 
as ``Class I areas'') that is ``reasonably attributable'' to a single 
source or small group of sources.\6\ These regulations, codified at 40 
CFR 51.300 through 51.307, represented the first phase of the EPA's 
efforts to address visibility impairment. In 1990, Congress added 
section 169B to the CAA to further address visibility impairment, 
specifically, impairment from regional haze.\7\ The EPA promulgated the 
Regional Haze Rule (RHR), codified at 40 CFR 51.308,\8\ on July 1, 
1999.\9\ These regional haze regulations are a central component of the 
EPA's comprehensive visibility protection program for Class I areas.
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    \3\ CAA 169A. Areas statutorily designated as mandatory Class I 
Federal areas consist of national parks exceeding 6,000 acres, 
wilderness areas and national memorial parks exceeding 5,000 acres, 
and all international parks that were in existence on August 7, 
1977. CAA 162(a). There are 156 mandatory Class I areas. The list of 
areas to which the requirements of the visibility protection program 
apply is in 40 CFR part 81, subpart D.
    \4\ CAA 169A(a)(1).
    \5\ CAA 169A(a)(4).
    \6\ 45 FR 80084 (December 2, 1980).
    \7\ CAA 169B.
    \8\ In addition to the generally applicable regional haze 
provisions at 40 CFR 51.308, the EPA also promulgated regulations 
specific to addressing regional haze visibility impairment in Class 
I areas on the Colorado Plateau at 40 CFR 51.309. ADEQ submitted SIP 
revisions to address the regional haze regulations at 40 CFR 51.309, 
on December 23, 2003, December 30, 2004, and December 24, 2008. The 
EPA approved certain burning and smoke management rules that were 
part of the 2008 SIP submittal, but disapproved the remainder of 
those submittals. 78 FR 48326 (August 8, 2013).
    \9\ 64 FR 35714.
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    Regional haze is visibility impairment that is produced by a 
multitude of anthropogenic sources and activities which are located 
across a broad geographic area and that emit pollutants that impair 
visibility. Visibility impairing pollutants include fine and coarse 
particulate matter (PM) (e.g., sulfates, nitrates, organic carbon, 
elemental carbon, and soil dust) and their precursors (e.g., sulfur 
dioxide (SO2), nitrogen oxides (NOX), and, in 
some cases, volatile organic compounds (VOC) and ammonia 
(NH3)). Fine particle precursors react in the atmosphere to 
form PM2.5, which impairs visibility by scattering and 
absorbing light. Visibility impairment reduces the perception of 
clarity and color, as well as visible distance.\10\
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    \10\ There are several ways to measure the amount of visibility 
impairment, i.e., haze. One such measurement is the deciview, which 
is the principal metric used by the RHR. Under many circumstances, a 
change in one deciview will be perceived by the human eye to be the 
same on both clear and hazy days. The deciview is unitless. It is 
proportional to the logarithm of the atmospheric extinction of 
light, which is the perceived dimming of light due to its being 
scattered and absorbed as it passes through the atmosphere. 
Atmospheric light extinction (b\ext\) is a metric used for 
expressing visibility and is measured in inverse megameters 
(Mm-\1\). The EPA's Guidance on Regional Haze State 
Implementation Plans for the Second Implementation Period (``2019 
Guidance'') offers the flexibility for the use of light extinction 
in certain cases. Light extinction can be simpler to use in 
calculations than deciviews, since it is not a logarithmic function. 
See, e.g., 2019 Guidance, pp 16, 19, https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period, The EPA Office of Air Quality Planning and 
Standards, Research Triangle Park (August 20, 2019). The formula for 
the deciview is 10 ln (b\ext\)/10 Mm - 1). 40 CFR 51.301.
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    To address regional haze visibility impairment, the 1999 RHR 
established an iterative planning process that requires both states in 
which Class I areas are located and states ``the emissions from which 
may reasonably be anticipated to cause or contribute to any impairment 
of visibility'' in a Class I area to periodically submit SIP revisions 
to address such impairment.\11\ Under the CAA, each SIP submission must 
contain ``a long-term (ten to fifteen years) strategy for making 
reasonable progress toward meeting the national goal.'' \12\ The 
initial round of SIP submissions also had to address the statutory 
requirement that certain older, larger sources of visibility impairing 
pollutants install and operate the best available retrofit technology 
(BART).\13\ States' first regional haze SIPs were due by December 17, 
2007,\14\ with subsequent SIP submissions containing updated long-term 
strategies originally due July 31, 2018, and every ten years 
thereafter.\15\ The EPA established in the 1999 RHR that all states 
either have Class I areas within their borders or ``contain sources 
whose emissions are reasonably anticipated to contribute to regional 
haze in a Class I area;'' therefore, all states must submit regional 
haze SIPs.\16\
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    \11\ CAA 169A(b)(2). The RHR expresses the statutory requirement 
for states to submit plans addressing out-of-state class I areas by 
providing that states must address visibility impairment ``in each 
mandatory Class I Federal area located outside the State that may be 
affected by emissions from within the State.'' 40 CFR 51.308(d), 
(f). See also 40 CFR 51.308(b), (f) (establishing submission dates 
for iterative regional haze SIP revisions); (64 FR at 35768, July 1, 
1999).
    \12\ CAA 169A(b)(2)(B).
    \13\ CAA 169A(b)(2)(A); 40 CFR 51.308(d), (e).
    \14\ 40 CFR 51.308(b).
    \15\ 64 FR at 35768 (July 1, 1999).
    \16\ Id. at 35721. In addition to each of the fifty states, the 
EPA also concluded that the Virgin Islands and District of Columbia 
must also submit regional haze SIPs because they either contain a 
Class I area or contain sources whose emissions are reasonably 
anticipated to contribute regional haze in a Class I area. See 40 
CFR 51.300(b), (d)(3).
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    Much of the focus in the first implementation period of the 
regional haze program, which ran from 2007 through 2018, was on 
satisfying states' BART obligations. First implementation period SIPs 
were additionally required to contain long-term strategies for making 
reasonable progress toward the national visibility goal, of which BART 
is one component. The core required elements for the first 
implementation period SIPs (other than BART) are laid out in 40 CFR 
51.308(d). Those provisions required that states containing Class I 
areas establish reasonable progress goals (RPGs) that are measured in 
deciviews and reflect the anticipated visibility conditions at the end 
of the implementation period including from implementation of states' 
long-term strategies. The first planning period RPGs were required to 
provide for an improvement in visibility for the most impaired days 
over the period of the implementation plan and ensure no degradation in 
visibility for the least impaired days over the same period. In 
establishing the RPGs for any Class I area in a state, the state was 
required to consider four statutory factors: the costs of compliance, 
the time necessary for compliance, the energy and non-air quality 
environmental impacts of compliance, and the remaining useful life of 
any potentially affected sources.\17\
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    \17\ CAA 169A(g)(1); 40 CFR 51.308(d)(1).
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    States were also required to calculate baseline (using the five 
year period of 2000-2004) and natural visibility conditions (i.e., 
visibility conditions without anthropogenic visibility impairment) for 
each Class I area, and to calculate the linear rate of progress needed 
to attain natural visibility conditions, assuming a starting point of 
baseline visibility conditions in 2004

[[Page 47400]]

and ending with natural conditions in 2064. This linear interpolation 
is known as the uniform rate of progress (URP) and is used as a 
tracking metric to help states assess the amount of progress they are 
making towards the national visibility goal over time in each Class I 
area.\18\ The 1999 RHR also provided that States' long-term strategies 
must include the ``enforceable emissions limitations, compliance, 
schedules, and other measures as necessary to achieve the reasonable 
progress goals.'' \19\ In establishing their long-term strategies, 
states are required to consult with other states that also contribute 
to visibility impairment in a given Class I area and include all 
measures necessary to obtain their shares of the emission reductions 
needed to meet the RPGs.\20\ Section 51.308(d) also contains seven 
additional factors states must consider in formulating their long-term 
strategies,\21\ as well as provisions governing monitoring and other 
implementation plan requirements.\22\ Finally, the 1999 RHR required 
states to submit periodic progress reports, which are SIP revisions due 
every five years that contain information on states' implementation of 
their regional haze plans and an assessment of whether anything 
additional is needed to make reasonable progress,\23\ and to consult 
with the Federal Land Manager(s) \24\ (FLMs) responsible for each Class 
I area according to the requirements in CAA section 169A(d) and 40 CFR 
51.308(i).
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    \18\ 40 CFR 51.308(d)(1)(i)(B), (d)(2). The EPA established the 
URP framework in the 1999 RHR to provide ``an equitable analytical 
approach'' to assessing the rate of visibility improvement at Class 
I areas across the country. The starting point for the URP analysis 
is 2004 and the endpoint was calculated based on the amount of 
visibility improvement that was anticipated to result from 
implementation of existing CAA programs over the period from the 
mid-1990s to approximately 2005. Assuming this rate of progress 
would continue into the future, the EPA determined that natural 
visibility conditions would be reached in 60 years, or 2064 (60 
years from the baseline starting point of 2004). However, the EPA 
did not establish 2064 as the year by which the national goal must 
be reached. 64 FR at 35731-32. That is, the URP and the 2064 date 
are not enforceable targets but are rather tools that ``allow for 
analytical comparisons between the rate of progress that would be 
achieved by the state's chosen set of control measures and the 
URP.'' 82 FR 3078, 3084 (January 10, 2017).
    \19\ 40 CFR 51.308(d)(3).
    \20\ 40 CFR 51.308(d)(3)(i), (ii).
    \21\ 40 CFR 51.308(d)(3)(v).
    \22\ 40 CFR 51.308(d)(4).
    \23\ See 40 CFR 51.308(g), (h).
    \24\ The EPA's regulations define ``Federal Land Manager'' as 
``the Secretary of the department with authority over the Federal 
Class I area (or the Secretary's designee) or, with respect to 
Roosevelt-Campobello International Park, the Chairman of the 
Roosevelt-Campobello International Park Commission.'' 40 CFR 51.301.
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    On January 10, 2017, the EPA promulgated revisions to the RHR, 
which apply for the second and subsequent implementation periods.\25\ 
The 2017 rulemaking made several changes to the requirements for 
regional haze SIPs to clarify States' obligations and streamline 
certain regional haze requirements. The revisions to the regional haze 
program for the second and subsequent implementation periods focused on 
the requirement that States' SIPs contain long-term strategies for 
making reasonable progress towards the national visibility goal. The 
reasonable progress requirements as revised in the 2017 rulemaking 
(referred to here as the 2017 RHR Revisions) are codified at 40 CFR 
51.308(f). Among other changes, the 2017 RHR Revisions adjusted the 
deadline for States to submit their second implementation period SIPs 
from July 31, 2018, to July 31, 2021, clarified the order of analysis 
and the relationship between RPGs and the long-term strategy, and 
focused on making visibility improvements on the days with the most 
anthropogenic visibility impairment, as opposed to the days with the 
most visibility impairment overall. The EPA also revised requirements 
of the visibility protection program related to periodic progress 
reports and FLM consultation. The specific requirements applicable to 
second implementation period regional haze SIP submissions are 
addressed in detail in Section III of this document.
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    \25\ 82 FR 3078.
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    The EPA provided guidance to the states for their second 
implementation period SIP submissions in the preamble to the 2017 RHR 
Revisions as well as in subsequent, stand-alone guidance documents. In 
August 2019, the EPA issued ``Guidance on Regional Haze State 
Implementation Plans for the Second Implementation Period'' (``2019 
Guidance'').\26\ On July 8, 2021, the EPA issued a memorandum 
containing ``Clarifications Regarding Regional Haze State 
Implementation Plans for the Second Implementation Period'' (``2021 
Clarifications Memo'').\27\ Additionally, the EPA further clarified the 
recommended procedures for processing ambient visibility data and 
optionally adjusting the URP to account for international anthropogenic 
and prescribed fire impacts in two technical guidance documents: the 
December 2018 ``Technical Guidance on Tracking Visibility Progress for 
the Second Implementation Period of the Regional Haze Program'' (``2018 
Visibility Tracking Guidance''),\28\ and the June 2020 ``Recommendation 
for the Use of Patched and Substituted Data and Clarification of Data 
Completeness for Tracking Visibility Progress for the Second 
Implementation Period of the Regional Haze Program'' and associated 
Technical Addendum (``2020 Data Completeness Memo'').\29\
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    \26\ Guidance on Regional Haze State Implementation Plans for 
the Second Implementation Period. https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period. The EPA Office of Air Quality Planning and 
Standards, Research Triangle Park (August 20, 2019).
    \27\ Clarifications Regarding Regional Haze State Implementation 
Plans for the Second Implementation Period. https://www.epa.gov/system/files/documents/2021-07/clarifications-regarding-regional-haze-state-implementation-plans-for-the-second-implementation-period.pdf. The EPA Office of Air Quality Planning and Standards, 
Research Triangle Park (July 8, 2021).
    \28\ Technical Guidance on Tracking Visibility Progress for the 
Second Implementation Period of the Regional Haze Program. https://www.epa.gov/visibility/technical-guidance-tracking-visibility-progress-second-implementation-period-regional The EPA Office of Air 
Quality Planning and Standards, Research Triangle Park. (December 
20, 2018).
    \29\ Recommendation for the Use of Patched and Substituted Data 
and Clarification of Data Completeness for Tracking Visibility 
Progress for the Second Implementation Period of the Regional Haze 
Program. https://www.epa.gov/visibility/memo-and-technical-addendum-ambient-data-usage-and-completeness-regional-haze-program The EPA 
Office of Air Quality Planning and Standards, Research Triangle Park 
(June 3, 2020).
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    As explained in the 2021 Clarifications Memo, the EPA intends the 
second implementation period of the regional haze program to secure 
meaningful reductions in visibility impairing pollutants that build on 
the significant progress states have achieved to date. The Agency also 
recognizes that analyses regarding reasonable progress are state-
specific and that, based on states' and sources' individual 
circumstances, what constitutes reasonable reductions in visibility 
impairing pollutants will vary from state-to-state. While there exist 
many opportunities for states to leverage both ongoing and upcoming 
emissions reductions under other CAA programs, the Agency expects 
states to undertake rigorous reasonable progress analyses that identify 
further opportunities to advance the national visibility goal 
consistent with the statutory and regulatory requirements.\30\ This is 
consistent with Congress's determination that a visibility protection 
program is needed in addition to the CAA's NAAQS and Prevention of 
Significant Deterioration (PSD) programs, as further emissions 
reductions may be necessary to adequately protect visibility in Class I 
areas throughout the country.\31\
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    \30\ See generally 2021 Clarifications Memo.
    \31\ See, e.g., H.R. Rep No. 95-294 p. 205 (``In determining how 
to best remedy the growing visibility problem in these areas of 
great scenic importance, the committee realizes that as a matter of 
equity, the national ambient air quality standards cannot be revised 
to adequately protect visibility in all areas of the country.''), 
(``the mandatory class I increments of [the PSD program] do not 
adequately protect visibility in class I areas'').

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B. Roles of Agencies in Addressing Regional Haze

    Because the air pollutants and pollution affecting visibility in 
Class I areas can be transported over long distances, successful 
implementation of the regional haze program requires long-term, 
regional coordination among multiple jurisdictions and agencies that 
have responsibility for Class I areas and the emissions that impact 
visibility in those areas. To address regional haze, states need to 
develop strategies in coordination with one another, considering the 
effect of emissions from one jurisdiction on the air quality in 
another. Five regional planning organizations (RPOs),\32\ which include 
representation from state and Tribal governments, the EPA, and FLMs, 
were developed in the lead-up to the first implementation period to 
address regional haze. RPOs evaluate technical information to better 
understand how emissions from State and Tribal land impact Class I 
areas across the country, pursue the development of regional strategies 
to reduce emissions of particulate matter and other pollutants leading 
to regional haze, and help states meet the consultation requirements of 
the RHR.
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    \32\ RPOs are sometimes also referred to as ``multi-
jurisdictional organizations,'' or MJOs. For the purposes of this 
notice, the terms RPO and MJO are synonymous.
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    The Western Regional Air Partnership (WRAP), one of the five RPOs, 
is a collaborative effort of state governments, Tribal governments, and 
various Federal agencies established to initiate and coordinate 
activities associated with the management of regional haze, visibility, 
and other air quality issues in the western corridor of the United 
States. Member states (listed alphabetically) include: Alaska, Arizona, 
California, Colorado, Idaho, Montana, Nevada, New Mexico, North Dakota, 
Oregon, South Dakota, Utah, Washington, and Wyoming. The Federal 
partner members of WRAP are the EPA, U.S. National Parks Service (NPS), 
U.S. Fish and Wildlife Service (FWS), and U.S. Forest Service (USFS). 
There are also 468 federally recognized Tribes within the WRAP region.

III. Requirements for Regional Haze Plans for the Second Implementation 
Period

    Under the CAA and the EPA's regulations, all 50 states, the 
District of Columbia, and the U.S. Virgin Islands were required to 
submit regional haze SIP revisions satisfying the applicable 
requirements for the second implementation period of the regional haze 
program by July 31, 2021. Each state's SIP must contain a long-term 
strategy for making reasonable progress toward meeting the national 
goal of remedying any existing and preventing any future anthropogenic 
visibility impairment in Class I areas.\33\ To this end, section 
51.308(f) lays out the process by which states determine what 
constitutes their long-term strategies, with the order of the 
requirements in section 51.308(f)(1) through (3) generally mirroring 
the order of the steps in the reasonable progress analysis \34\ and 
(f)(4) through (6) containing additional, related requirements. Broadly 
speaking, a state first must identify the Class I areas within the 
state and determine the Class I areas outside the state in which 
visibility may be affected by emissions from the state. These are the 
Class I areas that must be addressed in the state's long-term 
strategy.\35\ For each Class I area within its borders, a state must 
then calculate the baseline, current, and natural visibility conditions 
for that area, as well as the visibility improvement made to date and 
the URP.\36\ Each state having a Class I area and/or emissions that may 
affect visibility in a Class I area must then develop a long-term 
strategy that includes the enforceable emissions limitations, 
compliance schedules, and other measures that are necessary to make 
reasonable progress in such areas. A reasonable progress determination 
is based on applying the four factors in CAA section 169A(g)(1) to 
sources of visibility-impairing pollutants that the state has selected 
to assess for controls for the second implementation period. 
Additionally, as further explained below, the RHR at 40 CFR 
51.308(f)(2)(iv) separately provides five ``additional factors'' \37\ 
that states must consider in developing their long-term strategies.\38\ 
A state evaluates potential emissions reduction measures for those 
selected sources and determines which are necessary to make reasonable 
progress. Those measures are then incorporated into the state's long-
term strategy. After a state has developed its long-term strategy, it 
then establishes RPGs for each Class I area within its borders by 
modeling the visibility impacts of all reasonable progress controls at 
the end of the second implementation period, i.e., in 2028, as well as 
the impacts of other requirements of the CAA. The RPGs include 
reasonable progress controls not only for sources in the state in which 
the Class I area is located, but also for sources in other states that 
contribute to visibility impairment in that area. The RPGs are then 
compared to the baseline visibility conditions and the URP to ensure 
that progress is being made towards the statutory goal of preventing 
any future and remedying any existing anthropogenic visibility 
impairment in Class I areas.\39\
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    \33\ CAA 169A(b)(2)(B).
    \34\ The EPA explained in the 2017 RHR Revisions that we were 
adopting new regulatory language in 40 CFR 51.308(f) that, unlike 
the structure in 51.308(d), ``tracked the actual planning 
sequence.'' 82 FR 3091 (January 10, 2017).
    \35\ See 40 CFR 51.308(f), (f)(2).
    \36\ See 40 CFR 51.308(f)(1).
    \37\ The five ``additional factors'' for consideration in 
section 51.308(f)(2)(iv) are distinct from the four factors listed 
in CAA section 169A(g)(1) and 40 CFR 51.308(f)(2)(i) that states 
must consider and apply to sources in determining reasonable 
progress.
    \38\ See 40 CFR 51.308(f)(2).
    \39\ 40 CFR 51.308(f)(2)-(3).
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    In addition to satisfying the requirements at 40 CFR 51.308(f) 
related to reasonable progress, the regional haze SIP revisions for the 
second implementation period must address the requirements in section 
51.308(g)(1) through (5) pertaining to periodic reports describing 
progress towards the RPGs,\40\ as well as requirements for FLM 
consultation that apply to all visibility protection SIPs and SIP 
revisions.\41\
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    \40\ 40 CFR 51.308(f)(5).
    \41\ 40 CFR 51.308(i).
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    A state must submit its regional haze SIP and subsequent SIP 
revisions to the EPA according to the requirements applicable to all 
SIP revisions under the CAA and the EPA's regulations.\42\ Upon EPA 
approval, a SIP is enforceable by the Agency and the public under the 
CAA. If the EPA finds that a state failed to make a required SIP 
revision, or if the EPA finds that a state's SIP is incomplete or 
disapproves the SIP, the Agency must promulgate a federal 
implementation plan (FIP) that satisfies the applicable 
requirements.\43\
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    \42\ See CAA 169A(b)(2); CAA 110(a).
    \43\ CAA 110(c)(1).
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A. Identification of Class I Areas

    The first step in developing a regional haze SIP is for a state to 
determine which Class I areas, in addition to those within its borders, 
``may be affected'' by emissions from within the state. In the 1999 
RHR, the EPA determined that all states contribute to visibility 
impairment in at least one Class I area,\44\ and explained that the 
statute and regulations lay out an ``extremely low triggering 
threshold'' for determining

[[Page 47402]]

``whether States should be required to engage in air quality planning 
and analysis as a prerequisite to determining the need for control of 
emissions from sources within their State.'' \45\
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    \44\ 64 FR 35720-22.
    \45\ Id. at 35721.
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    A state must determine which Class I areas must be addressed by its 
SIP by evaluating the total emissions of visibility impairing 
pollutants from all sources within the state. While the RHR does not 
require this evaluation to be conducted in any particular manner, the 
EPA's 2019 Guidance provides recommendations for how such an assessment 
might be accomplished, including by, where appropriate, using the 
determinations previously made for the first implementation period.\46\ 
In addition, the determination of which Class I areas may be affected 
by a state's emissions is subject to the requirement in 40 CFR 
51.308(f)(2)(iii) to ``document the technical basis, including 
modeling, monitoring, cost, engineering, and emissions information, on 
which the State is relying to determine the emission reduction measures 
that are necessary to make reasonable progress in each mandatory Class 
I Federal area it affects.''
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    \46\ 2019 Guidance, pp. 8-9.
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B. Calculations of Baseline, Current, and Natural Visibility 
Conditions; Progress to Date; and the Uniform Rate of Progress

    As part of assessing whether a SIP submission for the second 
implementation period is providing for reasonable progress towards the 
national visibility goal, the RHR contains requirements in section 
51.308(f)(1) related to tracking visibility improvement over time. The 
requirements of this section apply only to states that have Class I 
areas within their borders; the required calculations must be made for 
each such Class I area. The EPA's 2018 Visibility Tracking Guidance 
\47\ provides recommendations to assist states in satisfying their 
obligations under section 51.308(f)(1); specifically, in developing 
information on baseline, current, and natural visibility conditions, 
and in making optional adjustments to the URP to account for the 
impacts of international anthropogenic emissions and prescribed fires.
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    \47\ The 2018 Visibility Tracking Guidance references and relies 
on parts of the 2003 Tracking Guidance: ``Guidance for Tracking 
Progress Under the Regional Haze Rule,'' which can be found at 
https://www.epa.gov/sites/default/files/2021-03/documents/tracking.pdf.
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    The RHR requires tracking of visibility conditions on two sets of 
days: the clearest and the most impaired days. Visibility conditions 
for both sets of days are expressed as the average deciview index for 
the relevant five-year period (the period representing baseline or 
current visibility conditions). The RHR provides that the relevant sets 
of days for visibility tracking purposes are the 20 percent clearest 
(the 20 percent of monitored days in a calendar year with the lowest 
values of the deciview index) and 20 percent most impaired days (the 20 
percent of monitored days in a calendar year with the highest amounts 
of anthropogenic visibility impairment).\48\ A state must calculate 
visibility conditions for both the 20 percent clearest and 20 percent 
most impaired days for the baseline period of 2000-2004 and the most 
recent five-year period for which visibility monitoring data are 
available (representing current visibility conditions).\49\ States must 
also calculate natural visibility conditions for the clearest and most 
impaired days,\50\ by estimating the conditions that would exist on 
those two sets of days absent anthropogenic visibility impairment.\51\ 
Using all these data, states must then calculate, for each Class I 
area, the amount of progress made since the baseline period (2000-2004) 
and how much improvement is left to achieve to reach natural visibility 
conditions.
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    \48\ 40 CFR 51.301. This notice also refers to the 20 percent 
clearest and 20 percent most anthropogenically impaired days as the 
``clearest'' and ``most impaired'' or ``most anthropogenically 
impaired'' days, respectively.
    \49\ 40 CFR 51.308(f)(1)(i), (iii).
    \50\ The RHR at 40 CFR 51.308(f)(1)(ii) contains an error 
related to the requirement for calculating two sets of natural 
conditions values. The rule says ``most impaired days or the 
clearest days'' where it should say ``most impaired days and 
clearest days.'' This is an error that was intended to be corrected 
in the 2017 RHR Revisions but did not get corrected in the final 
rule language. This is supported by the preamble text at 82 FR 3098: 
``In the final version of 40 CFR 51.308(f)(1)(ii), an occurrence of 
``or'' has been corrected to ``and'' to indicate that natural 
visibility conditions for both the most impaired days and the 
clearest days must be based on available monitoring information.''
    \51\ 40 CFR 51.308(f)(1)(ii).
---------------------------------------------------------------------------

    Using the data for the set of most impaired days only, states must 
plot a line between visibility conditions in the baseline period and 
natural visibility conditions for each Class I area to determine the 
URP--the amount of visibility improvement, measured in deciviews, that 
would need to be achieved during each implementation period to achieve 
natural visibility conditions by the end of 2064. The URP is used in 
later steps of the reasonable progress analysis for informational 
purposes and to provide a non-enforceable benchmark against which to 
assess a Class I area's rate of visibility improvement.\52\ 
Additionally, in the 2017 RHR Revisions, the EPA provided states the 
option of proposing to adjust the endpoint of the URP to account for 
impacts of anthropogenic sources outside the United States and/or 
impacts of certain types of wildland prescribed fires. These 
adjustments, which must be approved by the EPA, are intended to avoid 
any perception that states should compensate for impacts from 
international anthropogenic sources and to give states the flexibility 
to determine that limiting the use of wildland-prescribed fire is not 
necessary for reasonable progress.\53\
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    \52\ Being on or below the URP is not a ``safe harbor''; i.e., 
achieving the URP does not mean that a Class I area is making 
``reasonable progress'' and does not relieve a state from using the 
four statutory factors to determine what level of control is needed 
to achieve such progress. See, e.g., 82 FR 3093.
    \53\ 82 FR 3107 footnote 116.
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    The EPA's 2018 Visibility Tracking Guidance can be used to help 
satisfy the 40 CFR 51.308(f)(1) requirements, including in developing 
information on baseline, current, and natural visibility conditions, 
and in making optional adjustments to the URP. In addition, the 2020 
Data Completeness Memo provides recommendations on the data 
completeness language referenced in section 51.308(f)(1)(i) and 
provides updated natural conditions estimates for each Class I area.

C. Long-Term Strategy for Regional Haze

    The core component of a regional haze SIP submission is a long-term 
strategy that addresses regional haze in each Class I area within a 
state's borders and each Class I area that may be affected by emissions 
from the state. The long-term strategy ``must include the enforceable 
emissions limitations, compliance schedules, and other measures that 
are necessary to make reasonable progress, as determined pursuant to 
(f)(2)(i) through (iv).'' \54\ The amount of progress that is 
``reasonable progress'' is based on applying the four statutory factors 
in CAA section 169A(g)(1) in an evaluation of potential control options 
for sources of visibility impairing pollutants, which is referred to as 
a ``four-factor'' analysis. The outcome of that analysis is the 
emissions reduction measures that a particular source or group of 
sources needs to implement to make reasonable progress towards the 
national visibility goal.\55\ Emissions reduction measures that are 
necessary to make reasonable progress may be either new, additional 
control measures for a source, or they

[[Page 47403]]

may be the existing emissions reduction measures that a source is 
already implementing.\56\ Such measures must be represented by 
``enforceable emissions limitations, compliance schedules, and other 
measures'' (i.e., any additional compliance tools) in a state's long-
term strategy in its SIP.\57\
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    \54\ 40 CFR 51.308(f)(2).
    \55\ See 40 CFR 51.308(f)(2)(i).
    \56\ See 2019 Guidance, p. 43; 2021 Clarifications Memo, pp. 8-
10.
    \57\ 40 CFR 51.308(f)(2).
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    Section 51.308(f)(2)(i) provides the requirements for the four-
factor analysis. The first step of this analysis entails selecting the 
sources to be evaluated for emissions reduction measures; to this end, 
states should consider ``major and minor stationary sources or groups 
of sources, mobile sources, and area sources'' of visibility impairing 
pollutants for potential four-factor control analysis.\58\ A threshold 
question at this step is which visibility impairing pollutants will be 
analyzed. As the EPA previously explained, consistent with the first 
implementation period, the EPA generally expects that each state will 
analyze at least SO2 and NOX in selecting sources 
and determining control measures.\59\ A state that chooses not to 
consider at least these two pollutants should demonstrate why such 
consideration would be unreasonable.\60\
---------------------------------------------------------------------------

    \58\ 40 CFR 51.308(f)(2)(i).
    \59\ See 2019 Guidance, p. 12; 2021 Clarifications Memo, p. 4.
    \60\ 2021 Clarifications Memo, p. 4.
---------------------------------------------------------------------------

    While states have the option to analyze all sources, the 2019 
Guidance explains that ``an analysis of control measures is not 
required for every source in each implementation period,'' and that 
``[s]electing a set of sources for analysis of control measures in each 
implementation period is . . . consistent with the Regional Haze Rule, 
which sets up an iterative planning process and anticipates that a 
state may not need to analyze control measures for all its sources in a 
given SIP revision.'' \61\ However, given that source selection is the 
basis of all subsequent control determinations, a reasonable source 
selection process ``should be designed and conducted to ensure that 
source selection results in a set of pollutants and sources the 
evaluation of which has the potential to meaningfully reduce their 
contributions to visibility impairment.'' \62\
---------------------------------------------------------------------------

    \61\ 2019 Guidance, p. 9.
    \62\ 2021 Clarifications Memo, p. 3.
---------------------------------------------------------------------------

    The EPA explained in the 2021 Clarifications Memo that each state 
has an obligation to submit a long-term strategy that addresses the 
regional haze visibility impairment that results from emissions from 
within that state. Thus, source selection should focus on the in-state 
contribution to visibility impairment and be designed to capture a 
meaningful portion of the state's total contribution to visibility 
impairment in Class I areas. A state should not decline to select its 
largest in-state sources on the basis that there are even larger out-
of-state contributors.\63\
---------------------------------------------------------------------------

    \63\ Id. at 4. Similarly, in responding to comments on the 2017 
RHR Revisions, the EPA explained that ``[a] state should not fail to 
address its many relatively low-impact sources merely because it 
only has such sources and another state has even more low-impact 
sources and/or some high impact sources.'' Responses to Comments on 
Protection of Visibility: Amendments to Requirements for State 
Plans; Proposed Rule (81 FR 26942, May 4, 2016), pp. 87-88.
---------------------------------------------------------------------------

    Thus, while states have discretion to choose any source selection 
methodology that is reasonable, whatever choices they make should be 
reasonably explained. To this end, 40 CFR 51.308(f)(2)(i) requires that 
a state's SIP submission include ``a description of the criteria it 
used to determine which sources or groups of sources it evaluated.'' 
The technical basis for source selection, which may include methods for 
quantifying potential visibility impacts such as emissions divided by 
distance metrics, trajectory analyses, residence time analyses, and/or 
photochemical modeling, must also be appropriately documented, as 
required by 40 CFR 51.308(f)(2)(iii).
    Once a state has selected the set of sources, the next step is to 
determine the emissions reduction measures for those sources that are 
necessary to make reasonable progress for the second implementation 
period.\64\ This is accomplished by considering the four factors--``the 
costs of compliance, the time necessary for compliance, and the energy 
and non-air quality environmental impacts of compliance, and the 
remaining useful life of any existing source subject to such 
requirements.'' \65\ The EPA has explained that the four-factor 
analysis is an assessment of potential emissions reduction measures 
(i.e., control options) for sources; ``use of the terms `compliance' 
and `subject to such requirements' in section 169A(g)(1) strongly 
indicates that Congress intended the relevant determination to be the 
requirements with which sources would have to comply to satisfy the 
CAA's reasonable progress mandate.'' \66\ Thus, for each source it has 
selected for four-factor analysis,\67\ a state must consider a 
``meaningful set'' of technically feasible control options for reducing 
emissions of visibility impairing pollutants.\68\ The 2019 Guidance 
provides that ``[a] state must reasonably pick and justify the measures 
that it will consider, recognizing that there is no statutory or 
regulatory requirement to consider all technically feasible measures or 
any particular measures. A range of technically feasible measures 
available to reduce emissions would be one way to justify a reasonable 
set.'' \69\
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    \64\ The CAA provides that, ``[i]n determining reasonable 
progress there shall be taken into consideration'' the four 
statutory factors. CAA 169A(g)(1). However, in addition to four-
factor analyses for selected sources, groups of sources, or source 
categories, a state may also consider additional emissions reduction 
measures for inclusion in its long-term strategy, e.g., from other 
newly adopted, on-the-books, or on-the-way rules and measures for 
sources not selected for four-factor analysis for the second 
planning period.
    \65\ CAA 169A(g)(1).
    \66\ 82 FR 3091.
    \67\ ``Each source'' or ``particular source'' is used here as 
shorthand. While a source-specific analysis is one way of applying 
the four factors, neither the statute nor the RHR requires states to 
evaluate individual sources. Rather, states have ``the flexibility 
to conduct four-factor analyses for specific sources, groups of 
sources or even entire source categories, depending on state policy 
preferences and the specific circumstances of each state.'' 82 FR at 
3088. However, not all approaches to grouping sources for four-
factor analysis are necessarily reasonable; the reasonableness of 
grouping sources in any particular instance will depend on the 
circumstances and the manner in which grouping is conducted. If it 
is feasible to establish and enforce different requirements for 
sources or subgroups of sources, and if relevant factors can be 
quantified for those sources or subgroups, then states should make a 
separate reasonable progress determination for each source or 
subgroup. 2021 Clarifications Memo, pp. 7-8.
    \68\ Id. at 3088.
    \69\ 2019 Guidance, p. 29.
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    The EPA's 2021 Clarifications Memo provides further guidance on 
what constitutes a reasonable set of control options for consideration: 
``A reasonable four-factor analysis will consider the full range of 
potentially reasonable options for reducing emissions.'' \70\ In 
addition to add-on controls and other retrofits (i.e., new emissions 
reduction measures for sources), the EPA explained that states should 
generally analyze efficiency improvements for sources' existing 
measures as control options in their four-factor analyses, as in many 
cases such improvements are reasonable given that they typically 
involve only additional operation and maintenance costs. Additionally, 
the 2021 Clarifications Memo provides that states that have assumed a 
higher emissions rate than a source has achieved or could potentially 
achieve using its existing measures should also consider lower 
emissions rates as potential control options. That is, a state should 
consider a source's recent actual and projected emissions rates to 
determine if it could reasonably attain lower emissions rates with its 
existing

[[Page 47404]]

measures. If so, the state should analyze the lower emissions rate as a 
control option for reducing emissions.\71\ The EPA's recommendations to 
analyze potential efficiency improvements and achievable lower 
emissions rates apply to both sources that have been selected for four-
factor analysis and those that have forgone a four-factor analysis on 
the basis of existing ``effective controls.'' \72\
---------------------------------------------------------------------------

    \70\ 2021 Clarifications Memo, p. 7.
    \71\ Id. at 7.
    \72\ Id. at 5, 10.
---------------------------------------------------------------------------

    After identifying a reasonable set of potential control options for 
the sources it has selected, a state then collects information on the 
four factors with regard to each option identified. The EPA has also 
explained that, in addition to the four statutory factors, states have 
flexibility under the CAA and RHR to reasonably consider visibility 
benefits as an additional factor alongside the four statutory 
factors.\73\ The 2019 Guidance provides recommendations for the types 
of information that can be used to characterize the four factors (with 
or without visibility), as well as ways in which states might 
reasonably consider and balance that information to determine which of 
the potential control options is necessary to make reasonable 
progress.\74\ The 2021 Clarifications Memo contains further guidance on 
how states can reasonably consider modeled visibility impacts or 
benefits in the context of a four-factor analysis.\75\ Specifically, 
the EPA explained that while visibility can reasonably be used when 
comparing and choosing between multiple reasonable control options, it 
should not be used to summarily reject controls that are reasonable 
given the four statutory factors.\76\ Ultimately, while states have 
discretion to reasonably weigh the factors and to determine what level 
of control is needed, section 51.308(f)(2)(i) provides that a state 
``must include in its implementation plan a description of . . . how 
the four factors were taken into consideration in selecting the measure 
for inclusion in its long-term strategy.''
---------------------------------------------------------------------------

    \73\ See, e.g., Responses to Comments on Protection of 
Visibility: Amendments to Requirements for State Plans; Proposed 
Rule (81 FR 26942, May 4, 2016), Docket Number EPA-HQ-OAR-2015-0531, 
U.S. Environmental Protection Agency at 186; 2019 Guidance, pp. 36-
37.
    \74\ See 2019 Guidance, pp. 30-36.
    \75\ 2021 Clarifications Memo, pp. 12-15.
    \76\ Id. at 13.
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    As explained above, section 51.308(f)(2)(i) requires states to 
determine the emissions reduction measures for sources that are 
necessary to make reasonable progress by considering the four factors. 
Pursuant to section 51.308(f)(2), measures that are necessary to make 
reasonable progress towards the national visibility goal must be 
included in a state's long-term strategy and in its SIP.\77\ If the 
outcome of a four-factor analysis is a new, additional emissions 
reduction measure for a source, that new measure is necessary to make 
reasonable progress towards remedying existing anthropogenic visibility 
impairment and must be included in the SIP. If the outcome of a four-
factor analysis is that no new measures are reasonable for a source, 
continued implementation of the source's existing measures is generally 
necessary to prevent future emissions increases and thus to make 
reasonable progress towards the second part of the national visibility 
goal: preventing future anthropogenic visibility impairment.\78\ That 
is, when the result of a four-factor analysis is that no new measures 
are necessary to make reasonable progress, the source's existing 
measures are generally necessary to make reasonable progress and must 
be included in the SIP. However, there may be circumstances in which a 
state can demonstrate that a source's existing measures are not 
necessary to make reasonable progress. Specifically, if a state can 
demonstrate that a source will continue to implement its existing 
measures and will not increase its emissions rate, it may not be 
necessary to have those measures in the long-term strategy to prevent 
future emissions increases and future visibility impairment. The EPA's 
2021 Clarifications Memo provides further explanation and guidance on 
how states may demonstrate that a source's existing measures are not 
necessary to make reasonable progress.\79\ If the state can make such a 
demonstration, it need not include a source's existing measures in the 
long-term strategy or its SIP.
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    \77\ States may choose to, but are not required to, include 
measures in their long-term strategies beyond just the emission 
reduction measures that are necessary for reasonable progress. See 
2021 Clarifications Memo, p. 16. For example, states with smoke 
management programs may choose to submit their smoke management 
plans to the EPA for inclusion in their SIPs but are not required to 
do so. See, e.g., 82 FR at 3108-09 (requirement to consider smoke 
management practices and smoke management programs under 40 CFR 
51.308(f)(2)(iv) does not require states to adopt such practices or 
programs into their SIPs, although they may elect to do so).
    \78\ See CAA 169A(a)(1).
    \79\ See 2021 Clarifications Memo, pp. 8-10.
---------------------------------------------------------------------------

    As with source selection, the characterization of information on 
each of the factors is also subject to the documentation requirement in 
section 51.308(f)(2)(iii). The reasonable progress analysis, including 
source selection, information gathering, characterization of the four 
statutory factors (and potentially visibility), balancing of the four 
factors, and selection of the emissions reduction measures that 
represent reasonable progress, is a technically complex exercise, but 
also a flexible one that provides states with bounded discretion to 
design and implement approaches appropriate to their circumstances. 
Given this flexibility, section 51.308(f)(2)(iii) plays an important 
function in requiring a state to document the technical basis for its 
decision making so that the public and the EPA can comprehend and 
evaluate the information and analysis the state relied upon to 
determine what emissions reduction measures must be in place to make 
reasonable progress. The technical documentation must include the 
modeling, monitoring, cost, engineering, and emissions information on 
which the state relied to determine the measures necessary to make 
reasonable progress. This documentation requirement can be met through 
the provision of and reliance on technical analyses developed through a 
regional planning process, so long as that process and its output has 
been approved by all state participants. In addition to the explicit 
regulatory requirement to document the technical basis of their 
reasonable progress determinations, states are also subject to the 
general principle that those determinations must be reasonably moored 
to the statute.\80\ That is, a state's decisions about the emissions 
reduction measures that are necessary to make reasonable progress must 
be consistent with the statutory goal of remedying existing and 
preventing future visibility impairment.
---------------------------------------------------------------------------

    \80\ See Arizona ex rel. Darwin v. U.S. EPA, 815 F.3d 519, 531 
(9th Cir. 2016); Nebraska v. U.S. EPA, 812 F.3d 662, 668 (8th Cir. 
2016); North Dakota v. EPA, 730 F.3d 750, 761 (8th Cir. 2013); 
Oklahoma v. EPA, 723 F.3d 1201, 1206, 1208-10 (10th Cir. 2013); cf. 
also Nat'l Parks Conservation Ass'n v. EPA, 803 F.3d 151, 165 (3d 
Cir. 2015); Alaska Dep't of Envtl. Conservation v. EPA, 540 U.S. 
461, 485, 490 (2004).
---------------------------------------------------------------------------

    The four statutory factors (and potentially visibility) are used to 
determine what emissions reduction measures for selected sources must 
be included in a state's long-term strategy for making reasonable 
progress. Additionally, the RHR at 40 CFR 51.3108(f)(2)(iv) separately 
provides five ``additional factors'' \81\ that states must consider in 
developing their long-term strategies: (1) Emissions reductions due

[[Page 47405]]

to ongoing air pollution control programs, including measures to 
address reasonably attributable visibility impairment; (2) measures to 
reduce the impacts of construction activities; (3) source retirement 
and replacement schedules; (4) basic smoke management practices for 
prescribed fire used for agricultural and wildland vegetation 
management purposes and smoke management programs; and (5) the 
anticipated net effect on visibility due to projected changes in point, 
area, and mobile source emissions over the period addressed by the 
long-term strategy. The 2019 Guidance provides that a state may satisfy 
this requirement by considering these additional factors in the process 
of selecting sources for four-factor analysis, when performing that 
analysis, or both, and that not every one of the additional factors 
needs to be considered at the same stage of the process.\82\ The EPA 
provided further guidance on the five additional factors in the 2021 
Clarifications Memo, explaining that a state should generally not 
reject cost-effective and otherwise reasonable controls merely because 
there have been emissions reductions since the first planning period 
owing to other ongoing air pollution control programs or merely because 
visibility is otherwise projected to improve at Class I areas. 
Additionally, states generally should not rely on these additional 
factors to summarily assert that the state has already made sufficient 
progress and, therefore, no sources need to be selected or no new 
controls are needed regardless of the outcome of four-factor 
analyses.\83\
---------------------------------------------------------------------------

    \81\ The five ``additional factors'' for consideration in 
section 51.308(f)(2)(iv) are distinct from the four factors listed 
in CAA section 169A(g)(1) and 40 CFR 51.308(f)(2)(i) that states 
must consider and apply to sources in determining reasonable 
progress.
    \82\ See 2019 Guidance, p. 21.
    \83\ 2021 Clarifications Memo, p. 13.
---------------------------------------------------------------------------

    Because the air pollution that causes regional haze crosses state 
boundaries, section 51.308(f)(2)(ii) requires a state to consult with 
other states that also have emissions that are reasonably anticipated 
to contribute to visibility impairment in a given Class I area. 
Consultation allows for each state that impacts visibility in an area 
to share whatever technical information, analyses, and control 
determinations may be necessary to develop coordinated emissions 
management strategies. This coordination may be managed through inter- 
and intra-RPO consultation and the development of regional emissions 
strategies; additional consultations between states outside of RPO 
processes may also occur. If a state, pursuant to consultation, agrees 
that certain measures (e.g., a certain emissions limitation) are 
necessary to make reasonable progress at a Class I area, it must 
include those measures in its SIP.\84\ Additionally, the RHR requires 
that states that contribute to visibility impairment at the same Class 
I area consider the emissions reduction measures the other contributing 
states have identified as being necessary to make reasonable progress 
for their own sources.\85\ If a state has been asked to consider or 
adopt certain emissions reduction measures, but ultimately determines 
those measures are not necessary to make reasonable progress, that 
state must document in its SIP the actions taken to resolve the 
disagreement.\86\ The EPA will consider the technical information and 
explanations presented by the submitting state and the state with which 
it disagrees when considering whether to approve the state's SIP.\87\ 
Under all circumstances, a state must document in its SIP submission 
all substantive consultations with other contributing states.\88\
---------------------------------------------------------------------------

    \84\ 40 CFR 51.308(f)(2)(ii)(A).
    \85\ 40 CFR 51.308(f)(2)(ii)(B).
    \86\ 40 CFR 51.308(f)(2)(ii)(C).
    \87\ See id.; 2019 Guidance, p. 53.
    \88\ 40 CFR 51.308(f)(2)(ii)(C).
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D. Reasonable Progress Goals

    Reasonable progress goals ``measure the progress that is projected 
to be achieved by the control measures states have determined are 
necessary to make reasonable progress based on a four-factor 
analysis.'' \89\ Their primary purpose is to assist the public and the 
EPA in assessing the reasonableness of states' long-term strategies for 
making reasonable progress towards the national visibility goal.\90\ 
States in which Class I areas are located must establish two RPGs, both 
in deciviews--one representing visibility conditions on the clearest 
days and one representing visibility on the most anthropogenically 
impaired days--for each area within their borders.\91\ The two RPGs are 
intended to reflect the projected impacts, on the two sets of days, of 
the emissions reduction measures the state with the Class I area, as 
well as all other contributing states, have included in their long-term 
strategies for the second implementation period.\92\ The RPGs also 
account for the projected impacts of implementing other CAA 
requirements, including non-SIP based requirements. Because RPGs are 
the modeled result of the measures in states' long-term strategies (as 
well as other measures required under the CAA), they cannot be 
determined before states have conducted their four-factor analyses and 
determined the control measures that are necessary to make reasonable 
progress.\93\
---------------------------------------------------------------------------

    \89\ 82 FR 3091.
    \90\ See 40 CFR 51.308(f)(3)(iii)-(iv).
    \91\ 40 CFR 51.308(f)(3)(i).
    \92\ RPGs are intended to reflect the projected impacts of the 
measures all contributing states include in their long-term 
strategies. However, due to the timing of analyses and of control 
determinations by other states, other on-going emissions changes, a 
particular state's RPGs may not reflect all control measures and 
emissions reductions that are expected to occur by the end of the 
implementation period. The 2019 Guidance provides recommendations 
for addressing the timing of RPG calculations when states are 
developing their long-term strategies on disparate schedules, as 
well as for adjusting RPGs using a post-modeling approach. 2019 
Guidance, pp. 47-48.
    \93\ See 2021 Clarifications Memo, p. 6.
---------------------------------------------------------------------------

    For the second implementation period, the RPGs are set for 2028. 
Reasonable progress goals are not enforceable targets; \94\ rather, 
they ``provide a way for the states to check the projected outcome of 
the [long-term strategy] against the goals for visibility 
improvement.'' \95\ While states are not legally obligated to achieve 
the visibility conditions described in their RPGs, section 
51.308(f)(3)(i) requires that ``[t]he long-term strategy and the 
reasonable progress goals must provide for an improvement in visibility 
for the most impaired days since the baseline period and ensure no 
degradation in visibility for the clearest days since the baseline 
period.'' Thus, states are required to have emissions reduction 
measures in their long-term strategies that are projected to achieve 
visibility conditions on the most impaired days that are better than 
the baseline period and shows no degradation on the clearest days 
compared to the clearest days from the baseline period. The baseline 
period for the purpose of this comparison is the baseline visibility 
condition--the annual average visibility condition for the period 2000-
2004.\96\
---------------------------------------------------------------------------

    \94\ 40 CFR 51.308(f)(3)(iii).
    \95\ 2019 Guidance, p. 46.
    \96\ See 40 CFR 51.308(f)(1)(i), 82 FR 3097-98.
---------------------------------------------------------------------------

    So that RPGs may also serve as a metric for assessing the amount of 
progress a state is making towards the national visibility goal, the 
RHR requires states with Class I areas to compare the 2028 RPG for the 
most impaired days to the corresponding point on the URP line 
(representing visibility conditions in 2028 if visibility were to 
improve at a linear rate from conditions in the baseline period of 
2000-2004 to natural visibility conditions in 2064). If the most 
impaired days RPG in 2028 is above the URP (i.e., if visibility 
conditions are improving more slowly than the rate described by the 
URP), each state that contributes to visibility impairment in the Class 
I area must demonstrate, based on the four-factor analysis required

[[Page 47406]]

under 40 CFR 51.308(f)(2)(i), that no additional emissions reduction 
measures would be reasonable to include in its long-term strategy.\97\ 
To this end, 40 CFR 51.308(f)(3)(ii) requires that each state 
contributing to visibility impairment in a Class I area that is 
projected to improve more slowly than the URP provide ``a robust 
demonstration, including documenting the criteria used to determine 
which sources or groups [of] sources were evaluated and how the four 
factors required by paragraph (f)(2)(i) were taken into consideration 
in selecting the measures for inclusion in its long-term strategy.'' 
The 2019 Guidance provides suggestions about how such a ``robust 
demonstration'' might be conducted.\98\
---------------------------------------------------------------------------

    \97\ 40 CFR 51.308(f)(3)(ii).
    \98\ See 2019 Guidance, pp. 50-51.
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    The 2017 RHR, 2019 Guidance, and 2021 Clarifications Memo also 
explain that projecting an RPG that is on or below the URP based on 
only on-the-books and/or on-the-way control measures (i.e., control 
measures already required or anticipated before the four-factor 
analysis is conducted) is not a ``safe harbor'' from the CAA's and 
RHR's requirement that all states must conduct a four-factor analysis 
to determine what emissions reduction measures constitute reasonable 
progress. The URP is a planning metric used to gauge the amount of 
progress made thus far and the amount left before reaching natural 
visibility conditions. However, the URP is not based on consideration 
of the four statutory factors and therefore cannot answer the question 
of whether the amount of progress being made in any particular 
implementation period is ``reasonable progress.'' \99\
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    \99\ See 82 FR 3093, 3099-3100; 2019 Guidance, p. 22; 2021 
Clarifications Memo, pp. 15-16.
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E. Monitoring Strategy and Other State Implementation Plan Requirements

    Section 51.308(f)(6) requires states to have certain strategies and 
elements in place for assessing and reporting on visibility. Individual 
requirements under this section apply either to states with Class I 
areas within their borders, states with no Class I areas but that are 
reasonably anticipated to cause or contribute to visibility impairment 
in any Class I area, or both. A state with Class I areas within its 
borders must submit with its SIP revision a monitoring strategy for 
measuring, characterizing, and reporting regional haze visibility 
impairment that is representative of all Class I areas within the 
state. SIP revisions for such states must also provide for the 
establishment of any additional monitoring sites or equipment needed to 
assess visibility conditions in Class I areas, as well as reporting of 
all visibility monitoring data to the EPA at least annually. Compliance 
with the monitoring strategy requirement may be met through a state's 
participation in the Interagency Monitoring of Protected Visual 
Environments (IMPROVE) monitoring network, which is used to measure 
visibility impairment caused by air pollution at the 156 Class I areas 
covered by the visibility program.\100\ The IMPROVE monitoring data is 
used to determine the 20 percent most anthropogenically impaired and 20 
percent clearest sets of days every year at each Class I area and 
tracks visibility impairment over time.
---------------------------------------------------------------------------

    \100\ 40 CFR 51.308(f)(6), (f)(6)(i), (f)(6)(iv).
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    All states' SIPs must provide for procedures by which monitoring 
data and other information are used to determine the contribution of 
emissions from within the state to regional haze visibility impairment 
in affected Class I areas.\101\ Section 51.308(f)(6)(v) further 
requires that all states' SIPs provide for a statewide inventory of 
emissions of pollutants that are reasonably anticipated to cause or 
contribute to visibility impairment in any Class I area; the inventory 
must include emissions for the most recent year for which data are 
available and estimates of future projected emissions. States must also 
include commitments to update their inventories periodically. The 
inventories themselves do not need to be included as elements in the 
SIP revision and are not subject to EPA review as part of the Agency's 
evaluation of a SIP revision.\102\ All states' SIP revisions must also 
provide for any other elements, including reporting, recordkeeping, and 
other measures, that are necessary for states to assess and report on 
visibility.\103\ Per the 2019 Guidance, a state may note in its 
regional haze SIP revision that its compliance with the in 40 CFR part 
51 subpart A satisfies the requirement to provide for an emissions 
inventory for the most recent year for which data are available. To 
satisfy the requirement to provide estimates of future projected 
emissions, a state may explain in its SIP revision how projected 
emissions were developed for use in establishing RPGs for its own and 
nearby Class I areas.\104\
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    \101\ 40 CFR 51.308(f)(6)(ii), (iii).
    \102\ See ``Step 8: Additional requirements for regional haze 
SIPs'' in 2019 Guidance, p. 55.
    \103\ 40 CFR 51.308(f)(6)(vi).
    \104\ Id.
---------------------------------------------------------------------------

    Separate from the requirements related to monitoring for regional 
haze purposes under 40 CFR 51.308(f)(6), the RHR also contains a 
requirement at 40 CFR 51.308(f)(4) related to any additional monitoring 
that may be needed to address visibility impairment in Class I areas 
from a single source or a small group of sources. This is called 
``reasonably attributable visibility impairment.'' \105\ Under this 
provision, if the EPA or the FLM of an affected Class I area has 
advised a state that additional monitoring is needed to assess 
reasonably attributable visibility impairment, the state must include 
in its SIP revision for the second implementation period an appropriate 
strategy for evaluating such impairment.
---------------------------------------------------------------------------

    \105\ The EPA's visibility protection regulations define 
``reasonably attributable visibility impairment'' as ``visibility 
impairment that is caused by the emission of air pollutants from 
one, or a small number of sources.'' 40 CFR 51.301.
---------------------------------------------------------------------------

F. Requirements for Periodic Reports Describing Progress Towards the 
Reasonable Progress Goals

    Section 51.308(f)(5) requires a state's regional haze SIP revision 
to address the requirements of paragraphs 40 CFR 51.308(g)(1) through 
(5) so that the plan revision due in 2021 will serve also as a progress 
report addressing the period since submission of the progress report 
for the first implementation period. The regional haze progress report 
requirement is designed to inform the public and the EPA about a 
state's implementation of its existing long-term strategy and whether 
such implementation is in fact resulting in the expected visibility 
improvement.\106\ To this end, every state's SIP revision for the 
second implementation period is required to describe the status of 
implementation of all measures included in the state's long-term 
strategy, including BART and reasonable progress emissions reduction 
measures from the first implementation period, and the resulting 
emissions reductions.\107\
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    \106\ See 81 FR 26942, 26950 (May 4, 2016); 82 FR 3119 (January 
10, 2017).
    \107\ 40 CFR 51.308(g)(1) and (2).
---------------------------------------------------------------------------

    A core component of the progress report requirements is an 
assessment of changes in visibility conditions on the clearest and most 
impaired days. For second implementation period progress reports, 
section 51.308(g)(3) requires states with Class I areas within their 
borders to first determine current visibility conditions for each area 
on the most impaired and clearest days,\108\ and then to calculate the 
difference between those current conditions and baseline (2000-2004) 
visibility conditions to assess progress made to date.\109\ States

[[Page 47407]]

must also assess the changes in visibility impairment for the most 
impaired and clearest days since they submitted their first 
implementation period progress reports.\110\ Since different states 
submitted their first implementation period progress reports at 
different times, the starting point for this assessment will vary state 
by state.
---------------------------------------------------------------------------

    \108\ 40 CFR 51.308(g)(3)(i).
    \109\ See 40 CFR 51.308(g)(3)(ii).
    \110\ See 40 CFR 51.308(g)(3)(iii), (f)(5).
---------------------------------------------------------------------------

    Similarly, states must provide analyses tracking the change in 
emissions of pollutants contributing to visibility impairment from all 
sources and activities within the state over the period since they 
submitted their first implementation period progress reports.\111\ 
Changes in emissions should be identified by the type of source or 
activity. Section 51.308(g)(5) also addresses changes in emissions 
since the period addressed by the previous progress report and requires 
states' SIP revisions to include an assessment of any significant 
changes in anthropogenic emissions within or outside the state. This 
assessment must explain whether these changes in emissions were 
anticipated and whether they have limited or impeded progress in 
reducing emissions and improving visibility relative to what the state 
projected based on its long-term strategy for the first implementation 
period.
---------------------------------------------------------------------------

    \111\ See 40 CFR 51.308(g)(4), (f)(5).
---------------------------------------------------------------------------

G. Requirements for State and Federal Land Manager Coordination

    CAA section 169A(d) requires that before a state holds a public 
hearing on a proposed regional haze SIP revision, it must consult with 
the appropriate FLM or FLMs; pursuant to that consultation, the state 
must include a summary of the FLMs' conclusions and recommendations in 
the notice to the public. Consistent with this statutory requirement, 
the RHR also requires that states ``provide the [FLM] with an 
opportunity for consultation, in person and at a point early enough in 
the State's policy analyses of its long-term strategy emission 
reduction obligation so that information and recommendations provided 
by the [FLM] can meaningfully inform the State's decisions on the long-
term strategy.'' \112\ Consultation that occurs 120 days prior to any 
public hearing or public comment opportunity will be deemed ``early 
enough,'' but the RHR provides that in any event the opportunity for 
consultation must be provided at least 60 days before a public hearing 
or comment opportunity. This consultation must include the opportunity 
for the FLMs to discuss their assessment of visibility impairment in 
any Class I area and their recommendations on the development and 
implementation of strategies to address such impairment.\113\ For the 
EPA to evaluate whether FLM consultation meeting the requirements of 
the RHR has occurred, the SIP submission should include documentation 
of the timing and content of such consultation. The SIP revision 
submitted to the EPA must also describe how the state addressed any 
comments provided by the FLMs.\114\ Finally, a SIP revision must 
provide procedures for continuing consultation between the state and 
FLMs regarding the state's visibility protection program, including 
development and review of SIP revisions, five-year progress reports, 
and the implementation of other programs having the potential to 
contribute to impairment of visibility in Class I areas.\115\
---------------------------------------------------------------------------

    \112\ 40 CFR 51.308(i)(2).
    \113\ 40 CFR 51.308(i)(2).
    \114\ 40 CFR 51.308(i)(3).
    \115\ 40 CFR 51.308(i)(4).
---------------------------------------------------------------------------

IV. The EPA's Evaluation of Arizona's Regional Haze Submission for the 
Second Implementation Period

A. Background on Arizona's First Implementation Period SIP Submission

    Arizona submitted its initial regional haze SIP under 40 CFR 51.308 
to the EPA on February 28, 2011 (hereinafter ``2011 Submittal'').\116\ 
The EPA actions following the 2011 Submittal are outlined in Table 1.
---------------------------------------------------------------------------

    \116\ On December 23, 2003, ADEQ submitted a Regional Haze plan 
under 40 CFR 51.309 (``309 Plan''). Letter dated December 23, 2003, 
from Stephen A. Owens, Director, ADEQ, to Wayne Nastri, Regional 
Administrator, EPA, Region IX. On December 30, 2004, ADEQ submitted 
a revision to its 309 Plan, consisting of rules on emissions trading 
and smoke management, and a correction to the State's regional haze 
statutes. Letter dated December 30, 2004, from Stephen A. Owens, 
Director, ADEQ, to Wayne Nastri, Regional Administrator, EPA. On 
December 24, 2008, ADEQ sent a letter resubmitting the 309 Plan 
revisions to the EPA. Letter dated December 24, 2008, from Stephen 
A. Owens, Director, ADEQ, to Wayne Nastri, Regional Administrator, 
EPA. On May 16, 2006 (71 FR 28270) and May 8, 2007 (72 FR 25973), 
the EPA approved the smoke management rules that were part of these 
submittals. On August 8, 2013 (78 FR 48326), the EPA disapproved the 
remainder of the State's submittals under 40 CFR 309.

    Table 1--Summary of EPA Actions Under CAA Section 308 on Arizona
            Regional Haze in the First Implementation Period
------------------------------------------------------------------------
            Date                              EPA action
------------------------------------------------------------------------
December 5, 2012............  ``Phase 1'' partial approval and partial
                               disapproval of certain provisions of the
                               2011 Submittal and promulgation of
                               partial federal implementation plan
                               (FIP).\a\
July 30, 2013...............  ``Phase 2'' partial approval and partial
                               disapproval of remaining portions of
                               Arizona Regional Haze 2011 Submittal.\b\
September 3, 2014...........  ``Phase 3'' promulgation of FIP for
                               remaining portions of Arizona Regional
                               Haze program.\c\
April 10, 2015..............  Approval of SIP revision for the Arizona
                               Electric Power Cooperative (AEPCO) Apache
                               Generating Station.\d\
April 17, 2015..............  FIP revision replacing the control
                               technology demonstration requirements for
                               NOX at Lhoist North America of Arizona,
                               Inc. Nelson Lime Plant with revised
                               recordkeeping and reporting
                               requirements.\e\
April 13, 2016..............  FIP revision revising NOX requirements for
                               the Salt River Project Agricultural
                               Improvement and Power District (SRP)
                               Coronado Generating Station.\f\
November 21, 2016...........  FIP revision replacing the control
                               technology demonstration requirements for
                               NOX at CalPortland Cement (CPC) Rillito
                               Plant Kiln 4 and Phoenix Cement Company
                               (PCC) Clarkdale Plant Kiln 4 with revised
                               recordkeeping and reporting
                               requirements.\g\
March 27, 2017..............  Approval of SIP revision to replace FIP
                               for Arizona Public Service (APS) Cholla
                               Generating Station.\h\
October 10, 2017............  Approval of SIP revision to replace FIP
                               for the SRP Coronado Generating
                               Station.\i\
------------------------------------------------------------------------
\a\ 77 FR 72512 (December 5, 2012).
\b\ 78 FR 46142 (July 30, 2013).
\c\ 79 FR 52420 (September 3, 2014).
\d\ 80 FR 19220 (April 10, 2015).
\e\ 80 FR 21176 (April 17, 2015).
\f\ 81 FR 21735 (April 13, 2016).
\g\ 81 FR 83144 (November 21, 2016).
\h\ 82 FR 15139 (March 27, 2017).

[[Page 47408]]

 
\i\ 82 FR 46903 (October 10, 2017).

    On November 12, 2015, the State of Arizona submitted its Progress 
Report to meet the requirements of 40 CFR 51.308(g) and (h).\117\ The 
EPA approved the Progress Report on July 11, 2019.\118\
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    \117\ Letter dated November 12, 2015, from Eric C. Massey, 
Director, Air Quality Division, ADEQ, to Jared Blumenfeld, Regional 
Administrator, EPA Region IX.
    \118\ 84 FR 33002.
---------------------------------------------------------------------------

B. Overview of Arizona's Second Implementation Period SIP Submission

    In accordance with CAA sections 169A and the RHR at 40 CFR 
51.308(f), on August 15, 2022, ADEQ submitted a revision to the Arizona 
SIP to address its regional haze obligations for the second 
implementation period, which runs through 2028. Arizona made its 2022 
Regional Haze Plan submission available for public comment on June 13, 
2022. ADEQ received and responded to public comments and included the 
comments and responses to those comments in their submission.
    The following sections describe Arizona's SIP submission, including 
analyses conducted by the WRAP and Arizona, Arizona's assessment of 
progress made since the first implementation period in reducing 
emissions of visibility impairing pollutants, and the visibility 
improvement progress at its Class I areas and nearby Class I areas. 
This notice also provides the EPA's evaluation of Arizona's submission 
against the requirements of the CAA and RHR for the second 
implementation period of the regional haze program.

C. Identification of Class I Areas

    Section 169A(b)(2) of the CAA requires each state in which any 
Class I area is located or ``the emissions from which may reasonably be 
anticipated to cause or contribute to any impairment of visibility'' in 
a Class I area to have a plan for making reasonable progress toward the 
national visibility goal. The RHR implements this statutory requirement 
at 40 CFR 51.308(f), which provides that each state's plan ``must 
address regional haze in each mandatory Class I Federal area located 
within the State and in each mandatory Class I Federal area located 
outside the State that may be affected by emissions from within the 
State,'' and (f)(2), which requires each state's plan to include a 
long-term strategy that addresses regional haze in such Class I areas.
    The EPA explained in the 1999 RHR preamble that the CAA section 
169A(b)(2) requirement that states submit SIP revisions to address 
visibility impairment establishes ``an `extremely low triggering 
threshold' in determining which States should submit SIPs for regional 
haze.'' \119\ In concluding that each of the contiguous 48 states and 
the District of Columbia meet this threshold,\120\ the EPA relied on 
``a large body of evidence demonstrat[ing] that long-range transport of 
fine PM contributes to regional haze,'' \121\ including modeling 
studies that ``preliminarily demonstrated that each State not having a 
Class I area had emissions contributing to impairment in at least one 
downwind Class I area.'' \122\ In addition to the technical evidence 
supporting a conclusion that each state contributes to existing 
visibility impairment, the EPA also explained that the second half of 
the national visibility goal--preventing future visibility impairment--
requires having a framework in place to address future growth in 
visibility-impairing emissions and makes it inappropriate to 
``establish criteria for excluding States or geographic areas from 
consideration as potential contributors to regional haze visibility 
impairment.'' \123\ Thus, the EPA concluded that the agency's 
``statutory authority and the scientific evidence are sufficient to 
require all States to develop regional haze SIPs to ensure the 
prevention of any future impairment of visibility, and to conduct 
further analyses to determine whether additional control measures are 
needed to ensure reasonable progress in remedying existing impairment 
in downwind Class I areas.'' \124\ The EPA's 2017 revisions to the RHR 
did not disturb this conclusion.\125\
---------------------------------------------------------------------------

    \119\ 64 FR 35721.
    \120\ The EPA determined that ``there is more than sufficient 
evidence to support our conclusion that emissions from each of the 
48 contiguous states and the District of Columba may reasonably be 
anticipated to cause or contribute to visibility impairment in a 
Class I area.'' 64 FR at 35721. Hawaii, Alaska, and the U.S. Virgin 
Islands must also submit regional haze SIPs because they contain 
Class I areas.
    \121\ Id.
    \122\ Id. at 35722.
    \123\ Id. at 35721.
    \124\ Id. at 35722.
    \125\ See 82 FR 3094.
---------------------------------------------------------------------------

    Arizona has 12 Class I areas within its borders: the Chiricahua 
National Monument, Chiricahua Wilderness Area, Galiuro Wilderness Area, 
Grand Canyon National Park, Mazatzal Wilderness Area, Mount Baldy 
Wilderness Area, Petrified Forest National Park, Pine Mountain 
Wilderness, Saguaro National Park,\126\ Sierra Ancha Wilderness Area, 
Superstition Wilderness Area, and Sycamore Canyon Wilderness Area.
---------------------------------------------------------------------------

    \126\ Saguaro National Park was originally established in 1933 
as a National Monument. In 1976, portions of Saguaro National 
Monument were designated as a Wilderness Area, and the Saguaro 
Wilderness Area was designated as a Mandatory Class I area in 1979. 
44 FR 69124 (November 30, 1979). Congress officially elevated the 
area known as Saguaro National Monument to the current designation 
as a National Park in 1994.
---------------------------------------------------------------------------

    Arizona did not expressly identify within its SIP which Class I 
Federal areas located outside of Arizona may be affected by emissions 
from within Arizona. However, as part of its source selection process 
described in Chapter 8 and Appendix C, Section C2 of the 2022 Arizona 
Regional Haze Plan, Arizona included the Q/d \127\ values associated 
with Class I areas outside the State. Further, ADEQ reviewed the source 
apportionment results of the ``On the Books'' (``2028OTBa2'') 
projections scenario from the WRAP Regional Haze photochemical grid 
modeling platform.\128\ ADEQ participated in interstate consultation 
with California, Utah, Nevada, Colorado, and New Mexico, which included 
discussion of the WRAP modeling and source apportionment products.\129\ 
For New Mexico specifically, ADEQ also provided WRAP regional modeling 
platform source apportionment results for the 20 percent most impaired 
days at the four Class I areas in New Mexico that are closest to 
Arizona.\130\
---------------------------------------------------------------------------

    \127\ Q/d represents a source's annual emissions in tons (Q) 
divided by the distance in kilometers (d) between the source and the 
nearest Class I area. For regional haze purposes, only primary 
visibility-impairing pollutants were included in a source's total Q: 
NOX, SO2, and PM10.
    \128\ 2022 Arizona Regional Haze Plan, Chapter 7.4 and Appendix 
D. The Particle Source Apportionment Technology (PSAT) tool was 
applied at a regional level to separate U.S. anthropogenic 
contributions from those of fire, natural, and international 
anthropogenic contributions for a current period and a future year 
in 2028.
    \129\ Id. at Chapter 2.6.
    \130\ Id. at Table 2-3.
---------------------------------------------------------------------------

    As explained above, the EPA concluded in the 1999 RHR that ``all 
[s]tates contain sources whose emissions are reasonably anticipated to 
contribute to regional haze in a Class I area,'' \131\ and this 
determination was not changed in the 2017 RHR. Critically, the statute 
and regulation both require that the cause-or-contribute assessment 
consider all emissions of visibility-impairing pollutants from a state, 
as opposed to emissions of a particular pollutant or emissions from a 
certain set

[[Page 47409]]

of sources. Consistent with these requirements, the 2019 Guidance makes 
it clear that ``all types of anthropogenic sources are to be included 
in the determination'' of whether a state's emissions are reasonably 
anticipated to result in any visibility impairment.\132\ As explained 
in Section IV.E.2 of this document, we are proposing to find that the 
2022 Arizona Regional Haze Plan did not fully meet the requirements of 
40 CFR 51.308(f)(2) related to the development of a long-term strategy. 
Although the State's failure to identify specific out-of-state Class I 
areas is not the basis for this proposed disapproval, we recommend that 
ADEQ more clearly identify which out-of-state Class I areas may be 
affected by emissions from Arizona.
---------------------------------------------------------------------------

    \131\ 64 FR at 35721.
    \132\ 2019 Guidance, p. 8.
---------------------------------------------------------------------------

D. Calculations of Baseline, Current, and Natural Visibility 
Conditions; Progress to Date; and the Uniform Rate of Progress

    Section 51.308(f)(1) requires states to determine the following for 
``each mandatory Class I Federal area located within the State'': 
baseline visibility conditions for the most impaired and clearest days, 
natural visibility conditions for the most impaired and clearest days, 
progress to date for the most impaired and clearest days, the 
differences between current visibility conditions and natural 
visibility conditions, and the URP. This section also provides the 
option for states to propose adjustments to the URP line for a Class I 
area to account for visibility impacts from anthropogenic sources 
outside the United States and/or the impacts from wildland prescribed 
fires that were conducted for certain, specified objectives.\133\
---------------------------------------------------------------------------

    \133\ 40 CFR 51.308(f)(1)(vi)(B).
---------------------------------------------------------------------------

    In the 2022 Arizona Regional Haze Plan, ADEQ used visibility data 
from IMPROVE monitoring sites for 2000-2004 for baseline 
visibility.\134\ ADEQ also obtained visibility data from IMPROVE 
monitoring data for 2005-2019. The five-year average of 2015-2019 
represents current visibility conditions. ADEQ also determined natural 
visibility by estimating the natural concentrations of visibility-
impairing pollutants and then calculating total light extinction with 
the IMPROVE algorithm. Comparison of baseline conditions to natural 
visibility conditions shows the improvement necessary to attain natural 
visibility by 2064 measured in deciviews of improvement per year that 
represents the URP. The calculations of baseline, current, and natural 
visibility conditions, as well as the progress to date, differences 
between current visibility conditions and natural visibility 
conditions, and the URP for each of the state's Class I areas can be 
found in Chapter 5.2 of the 2022 Arizona Regional Haze Plan. The URP 
glidepaths and 2028 visibility projections are discussed further in 
Section 7 and Appendix D. A summary of Arizona's visibility conditions 
and unadjusted URPs is also presented in Table 2 of this document. A 
summary of Arizona's adjusted URPs is presented in Table 21 of this 
document.
---------------------------------------------------------------------------

    \134\ 2022 Arizona Regional Haze Plan, Chapter 5.
---------------------------------------------------------------------------

    Data for the Chiricahua National Monument, Chiricahua Wilderness 
Area, and the Galiuro Wilderness Area come from the CHIR1 monitoring 
site.\135\ These three Class I areas have 2000-2004 baseline visibility 
conditions of 4.9 deciviews on the 20 percent clearest days and 10.5 
deciviews on the 20 percent most impaired days. ADEQ calculated an 
estimated natural background visibility of 1.8 deciviews on the 20 
percent clearest days and 4.9 deciviews on the 20 percent most impaired 
days for these three Class I areas. The current visibility conditions, 
which are based on 2015-2019 monitoring data, were 3.9 deciviews on the 
clearest days and 9.5 deciviews on the most impaired days, which are 
2.1 deciviews and 4.6 deciviews greater than natural conditions on the 
respective sets of days. The progress to date, subtracting current 
conditions from baseline conditions, yields a 1.1 deciview improvement 
for the 20 percent clearest days and 1.0 deciview improvement for the 
20 percent most impaired days. ADEQ calculated an annual URP of 0.09 
deciviews per year needed to reach natural visibility on the 20 percent 
most impaired days by 2064. ADEQ also indicates that the visibility 
improvement needed to maintain the URP from the baseline to 2028 is 2.2 
deciviews.
---------------------------------------------------------------------------

    \135\ Figure 5-2 in the 2022 Arizona Regional Haze Plan depicts 
the annual and 5-year average most impaired day and clearest day 
visibility in deciviews (dv), the unadjusted MID URP, and the 
clearest days threshold for the CHIR1 site.
---------------------------------------------------------------------------

    Data for the Grand Canyon National Park come from the GRCA2 
site.\136\ The Grand Canyon has 2000-2004 baseline visibility 
conditions of 2.2 deciviews on the 20 percent clearest days and 8 
deciviews on the 20 percent most impaired days. ADEQ calculated an 
estimated natural background visibility of 0.3 deciviews on the 20 
percent clearest days and 4.2 deciviews on the 20 percent most impaired 
days for these three Class I areas. The current visibility conditions, 
which are based on 2015-2019 monitoring data, were 1.6 deciviews on the 
clearest days and 6.9 deciviews on the most impaired days, which are 
1.3 deciviews and 2.7 deciviews greater than natural conditions on the 
respective sets of days. The progress to date, subtracting current 
conditions from baseline conditions, yields a 0.6 deciview improvement 
for the 20 percent clearest days and 1.1 deciview improvement for the 
20 percent most impaired days. ADEQ calculated an annual URP of 0.06 
deciviews per year needed to reach natural visibility on the 20 percent 
most impaired days by 2064. ADEQ also indicates that the visibility 
improvement needed to maintain the URP from the baseline to 2028 is 1.5 
deciviews.
---------------------------------------------------------------------------

    \136\ Figure 5-3 in the 2022 Arizona Regional Haze Plan depicts 
the annual and 5-year average most impaired day and clearest day 
visibility in dv, the unadjusted MID URP, and the clearest days 
threshold for the GRCA2 site.
---------------------------------------------------------------------------

    Data for the Mazatzal Wilderness Area and Pine Mountain Wilderness 
Area come from the IKBA1 monitoring site.\137\ These two Class I areas 
have 2000-2004 baseline visibility conditions of 5.4 deciviews on the 
20 percent clearest days and 11.2 deciviews on the 20 percent most 
impaired days. ADEQ calculated an estimated natural background 
visibility of 1.9 deciviews on the 20 percent clearest days and 5.2 
deciviews on the 20 percent most impaired days for these two Class I 
areas. The current visibility conditions, which are based on 2015-2019 
monitoring data, were 4.2 deciviews on the clearest days and 9.5 
deciviews on the most impaired days, which are 2.3 deciviews and 4.3 
deciviews greater than natural conditions on the respective sets of 
days. The progress to date, subtracting current conditions from 
baseline conditions, yields a 1.2 deciview improvement for the 20 
percent clearest days and 1.7 deciview improvement for the 20 percent 
most impaired days. ADEQ calculated an annual URP of 0.10 deciviews per 
year needed to reach natural visibility on the 20 percent most impaired 
days by 2064. ADEQ indicates that the visibility improvement needed to 
maintain the URP from the baseline to 2028 is 2.4 deciviews.
---------------------------------------------------------------------------

    \137\ Figure 5-4 in the 2022 Arizona Regional Haze Plan depicts 
the annual and 5-year average most impaired day and clearest day 
visibility (dv), the unadjusted MID URP, and the clearest days 
threshold for the IKBA1 site.
---------------------------------------------------------------------------

    Data for the Mount Baldy Wilderness Area come from the BALD1 
monitoring

[[Page 47410]]

site.\138\ Mount Baldy has 2000-2004 baseline visibility conditions of 
3.0 deciviews on the 20 percent clearest days and 8.8 deciviews on the 
20 percent most impaired days. ADEQ calculated an estimated natural 
background visibility of 0.5 on the 20 percent clearest days and 4.2 
deciviews on the 20 percent most impaired days. The current visibility 
conditions, which are based on 2015-2019 monitoring data, were 1.8 
deciviews on the clearest days and 7.3 deciviews on the most impaired 
days, which are 1.3 deciviews and 3.1 deciviews greater than natural 
conditions on the respective sets of days. The progress to date, 
subtracting current conditions from baseline conditions, yields a 1.2 
deciview improvement for the 20 percent clearest days and 1.5 deciview 
improvement for the 20 percent most impaired days. ADEQ calculated an 
annual URP of 0.08 deciviews per year needed to reach natural 
visibility on the 20 percent most impaired days by 2064. ADEQ indicates 
that the visibility improvement needed to maintain the URP from the 
baseline to 2028 is 1.8 deciviews.
---------------------------------------------------------------------------

    \138\ 2022 Arizona Regional Haze Plan, Tables 5-1 through 5-3.
---------------------------------------------------------------------------

    Data for the Petrified Forest National Park come from the PEFO1 
monitoring site.\139\ The Class I area has 2000-2004 baseline 
visibility conditions of 5.0 deciviews on the 20 percent clearest days 
and 9.8 deciviews on the 20 percent most impaired days. ADEQ calculated 
an estimated natural background visibility of 1.1 deciviews on the 20 
percent clearest days and 4.2 deciviews on the 20 percent most impaired 
days. The current visibility conditions, which are based on 2015-2019 
monitoring data, were 3.3 deciviews on the clearest days and 8.1 
deciviews on the most impaired days, which are 2.2 deciviews and 3.9 
deciviews greater than natural conditions on the respective sets of 
days. The progress to date, subtracting current conditions from 
baseline conditions, yields a 1.8 deciview improvement for the 20 
percent clearest days and 1.7 deciview improvement for the 20 percent 
most impaired days. ADEQ calculated an annual URP of 0.09 deciviews per 
year needed to reach natural visibility on the 20 percent most impaired 
days by 2064. ADEQ indicates that the visibility improvement needed to 
maintain the URP from the baseline to 2028 is 2.4 deciviews.
---------------------------------------------------------------------------

    \139\ Figure 5-5 in the 2022 Arizona Regional Haze Plan depicts 
the annual and 5-year average most impaired day and clearest day 
visibility in dv, the unadjusted MID URP, and the clearest days 
threshold for the PEFO1 site.
---------------------------------------------------------------------------

    Data for the Saguaro National Park come from the SAGU1 monitoring 
site.\140\ The Class I area has 2000-2004 baseline visibility 
conditions of 6.9 deciviews on the 20 percent clearest days and 12.6 
deciviews on the 20 percent most impaired days. ADEQ calculated an 
estimated natural background visibility of 2.2 deciviews on the 20 
percent clearest days and 5.1 deciviews on the 20 percent most impaired 
days. The current visibility conditions, which are based on 2015-2019 
monitoring data, were 5.8 deciviews on the clearest days and 10.7 
deciviews on the most impaired days, which are 3.6 deciviews and 5.6 
deciviews greater than natural conditions on the respective sets of 
days. The progress to date, subtracting current conditions from 
baseline conditions, yields a 1.1 deciview improvement for the 20 
percent clearest days and 1.9 deciview improvement for the 20 percent 
most impaired days. ADEQ calculated an annual URP of 0.12 deciviews per 
year needed to reach natural visibility on the 20 percent most impaired 
days by 2064. ADEQ indicates that the visibility improvement needed to 
maintain the URP from the baseline to 2028 is 3.0 deciviews.
---------------------------------------------------------------------------

    \140\ Figure 5-6 in the 2022 Arizona Regional Haze Plan depicts 
the annual and 5-year average most impaired day and clearest day 
visibility in dv, the unadjusted MID URP, and the clearest days 
threshold for the SAGU1 site.
---------------------------------------------------------------------------

    Data for the Sierra Ancha Wilderness Area come from the SIAN1 
monitoring site.\141\ The Class I area has 2000-2004 baseline 
visibility conditions of 6.2 deciviews on the 20 percent clearest days 
and 10.8 deciviews on the 20 percent most impaired days. ADEQ 
calculated an estimated natural background visibility of 2.0 deciviews 
on the 20 percent clearest days and 5.1 deciviews on the 20 percent 
most impaired days. The current visibility conditions, which are based 
on 2015-2019 monitoring data, were 4.3 deciviews on the clearest days 
and 9.4 deciviews on the most impaired days, which are 2.3 deciviews 
and 4.3 deciviews greater than natural conditions on the respective 
sets of days. The progress to date, subtracting current conditions from 
baseline conditions, yields a 1.9 deciview improvement for the 20 
percent clearest days and 1.4 deciview improvement for the 20 percent 
most impaired days. ADEQ calculated an annual URP of 0.09 deciviews per 
year needed to reach natural visibility on the 20 percent most impaired 
days by 2064. ADEQ indicates that the visibility improvement needed to 
maintain the URP from the baseline to 2028 is 2.3 deciviews.
---------------------------------------------------------------------------

    \141\ Figure 5-7 in the 2022 Arizona Regional Haze Plan depicts 
the annual and 5-year average most impaired day and clearest day 
visibility in dv, the unadjusted MID URP, and the clearest days 
threshold for the SIAN1 site. Data is not available for 2016-2020 
for SIAN1.
---------------------------------------------------------------------------

    Data for the Superstition Wilderness Area come from the TONT1 
monitoring site.\142\ The Class I area has 2000-2004 baseline 
visibility conditions of 6.5 deciviews on the 20 percent clearest days 
and 11.7 deciviews on the 20 percent most impaired days. ADEQ 
calculated an estimated natural background visibility of 2.0 deciviews 
on the 20 percent clearest days and 5.1 deciviews on the 20 percent 
most impaired days. The current visibility conditions, which are based 
on 2015-2019 monitoring data, were 4.9 deciviews on the clearest days 
and 10.3 deciviews on the most impaired days, which are 2.9 deciviews 
and 5.2 deciviews greater than natural conditions on the respective 
sets of days. The progress to date, subtracting current conditions from 
baseline conditions, yields a 1.6 deciview improvement for the 20 
percent clearest days and 1.3 deciview improvement for the 20 percent 
most impaired days. ADEQ calculated an annual URP of 0.09 deciviews per 
year needed to reach natural visibility on the 20 percent most impaired 
days by 2064. ADEQ indicates that the visibility improvement needed to 
maintain the URP from the baseline to 2028 is 2.6 deciviews.
---------------------------------------------------------------------------

    \142\ Figure 5-8 in the 2022 Arizona Regional Haze Plan depicts 
the annual and 5-year average most impaired day and clearest day 
visibility in dv, the unadjusted MID URP, and the clearest days 
threshold for the TONT1 site.
---------------------------------------------------------------------------

    Data for the Sycamore Canyon Wilderness Area come from the 
SYCA_RHTS monitoring site.\143\ The Class I area has 2000-2004 baseline 
visibility conditions of 5.6 deciviews on the 20 percent clearest days 
and 12.2 deciviews on the 20 percent most impaired days. ADEQ 
calculated an estimated natural background visibility of 1.0 deciview 
on the 20 percent clearest days and 4.7 deciviews on the 20 percent 
most impaired days. The current visibility conditions, which are based 
on 2015-2019 monitoring data, were 3.9 deciviews on the clearest days 
and 11.7 deciviews on the most impaired days, which are 2.9 deciviews 
and 7.0 deciviews greater than natural

[[Page 47411]]

conditions on the respective sets of days. The progress to date, 
subtracting current conditions from baseline conditions, yields a 1.6 
deciview improvement for the 20 percent clearest days and 0.4 deciview 
improvement for the 20 percent most impaired days. ADEQ calculated an 
annual URP of 0.12 deciviews per year needed to reach natural 
visibility on the 20 percent most impaired days by 2064. ADEQ indicates 
that the visibility improvement needed to maintain the URP from the 
baseline to 2028 is 3.0 deciviews.
---------------------------------------------------------------------------

    \143\ Figure 5-9 in the 2022 Arizona Regional Haze Plan depicts 
the annual and 5-year average most impaired day and clearest day 
visibility in dv, the unadjusted MID URP, and the clearest days 
threshold for the SYCA_RHTS site. The abbreviation ``SYCA_RHTS'' is 
for Sycamore Regional Haze Tracking Site, and combines data from the 
SYCA1 IMPROVE site, which closed in 2015 during the baseline period, 
and data from the newer SYCA2 site.

                                                         Table 2--Visibility Conditions and Uniform Rate of Progress, in Deciviews (dv)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                             20% Clearest days                          20% Most-impaired days                          Maintain URP
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                                                          total dv     total dv
                         Class I Area                           Baseline   Current    Natural    Difference   Baseline   Current    Natural    Difference  dv per year   (baseline    (baseline
                                                                                                                                                                          to 2019)     to 2028)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Chiricahua NM WA.............................................        4.9        3.9        1.8          2.1       10.5        9.5        4.9          4.6         0.09          1.4          2.2
Chiricahua WA................................................        4.9        3.9        1.8          2.1       10.5        9.5        4.9          4.6         0.09          1.4          2.2
Galiuro WA...................................................        4.9        3.9        1.8          2.1       10.5        9.5        4.9          4.6         0.09          1.4          2.2
Grand Canyon NP..............................................        2.2        1.6        0.3          1.3        8.0        6.9        4.2          2.7         0.06          1.0          1.5
Mazatzal WA..................................................        5.4        4.2        1.9          2.3       11.2        9.5        5.2          4.3         0.10          1.5          2.4
Mount Baldy WA...............................................        3.0        1.8        0.5          1.3        8.8        7.3        4.2          3.1         0.08          1.2          1.8
Petrified Forest NP..........................................        5.0        3.3        1.1          2.2        9.8        8.1        4.2          3.9         0.09          1.4          2.2
Pine Mountain WA.............................................        5.4        4.2        1.9          2.3       11.2        9.5        5.2          4.3         0.10          1.5          2.4
Saguaro NP...................................................        6.9        5.8        2.2          3.6       12.6       10.7        5.1          5.6         0.12          1.9          3.0
Sierra Ancha WA..............................................        6.2        4.3        2.0          2.3       10.8        9.4        5.1          4.3         0.09          1.2          2.3
Superstition WA..............................................        6.5        4.9        2.0          2.9       11.7       10.3        5.1          5.2         0.11          1.6          2.6
Sycamore Canyon WA...........................................        5.6        3.9        1.0          2.9       12.2       11.7        4.7          7.0         0.12          1.9          3.0
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, p. 38, Tables 5-1, 5-2, and 5-3. Baseline conditions are for 2000-2004 Current Conditions are for 2015-2019; Difference is Current dv minus Natural
  Conditions. Maintain URP shows the deciviews per year and the total deciview improvements needed to maintain the Uniform Rate of Progress to 2019 and 2028.

    ADEQ chose to adjust its URP to account for international 
anthropogenic impacts and for the impacts of wildland prescribed fires. 
The WRAP/WAQS Regional Haze modeling platform used scaled 2014 NEI 
wildland prescribed fire data for purposes of calculating the URP 
adjustments. ADEQ submits activity data related to wildland prescribed 
fires approved under its SIP approved Enhanced Smoke Management Program 
to the EPA for use in the development of the NEI. WRAP used the results 
from the CAMx 2028OTBa2 High-Level Source Apportionment run to obtain 
concentrations due to international emissions and to prescribed fire. 
These concentrations were then used in a relative sense to estimate the 
contributions for use in adjusting the URP. That is, the modeled 
relative effect of removing their emissions (relative response factors) 
was applied to projections of 2028 concentrations. The resulting 
concentration decrease was taken as the contribution of these sources. 
The international and prescribed fire contributions were therefore 
calculated in a fashion consistent with each other and with the 2028 
projections. This approach is consistent with the default method 
described in the EPA's September 2019 regional haze modeling Technical 
Support Document (``EPA 2019 Modeling TSD'') \144\ and with the source 
apportionment approach described in EPA's 2018 Visibility Tracking 
Guidance.\145\ Two different adjusted glidepath options, 
``International Emissions Only (A)'' and ``International Emissions + 
Wildland Rx Fire (B),'' were made available on the WRAP TSS to adjust 
the URP glidepath end points projections at 2064 for Class I federal 
areas on the most impaired days. ADEQ used the International Emissions 
+ Wildland Rx Fire glidepath endpoint adjustment option. The choice of 
adjustment option made a negligible difference for five of the nine 
IMPROVE monitor locations, a small difference for three others, and a 
larger difference for the SYCA_RHTS monitor covering the Sycamore 
Canyon Wilderness. The deciview values for the URP glidepaths, both 
unadjusted and adjusted, were fairly close to values estimated in the 
EPA 2019 Modeling TSD. The choice of adjustment option made no 
difference in whether the RPG for each area was above or below its URP 
glidepath, which is discussed in the Section IV.F of this document.
---------------------------------------------------------------------------

    \144\ Memorandum from Richard A. Wayland, Director, Air Quality 
Assessment Division, EPA, to Regional Air Division Directors, 
Subject: ``Availability of Modeling Data and Associated Technical 
Support Document for the EPA's Updated 2028 Visibility Air Quality 
Modeling,'' September 19, 2019, available at https://www.epa.gov/visibility/technical-support-document-epas-updated-2028-regional-haze-modeling.
    \145\ Memorandum from Richard A. Wayland, Director, Air Quality 
Assessment Division, EPA, to Regional Air Division Directors, 
Subject: ``Technical Guidance on Tracking Visibility Progress for 
the Second Implementation Period of the Regional Haze Program,'' 
December 20, 2018, available at https://www.epa.gov/sites/default/files/2018-12/documents/technical_guidance_tracking_visibility_progress.pdf.
---------------------------------------------------------------------------

    The EPA is therefore proposing to find that Chapter 5 and Appendix 
A of the 2022 Arizona Regional Haze Plan meet the requirements of 40 
CFR 51.308(f)(1) related to the calculations of baseline, current, and 
natural visibility conditions; progress to date; differences between 
current visibility conditions and natural visibility conditions; and 
the URPs for the second implementation period. We also propose to find 
that ADEQ has estimated the impacts from anthropogenic sources outside 
the United States and wildland prescribed fires using scientifically 
valid data and methods, and we therefore propose to approve the 
adjustments to the URPs pursuant to 40 CFR 51.308(f)(1)(vi)(B).

E. Long-Term Strategy for Regional Haze

1. Arizona's Long-Term Strategy in the 2022 Arizona Regional Haze Plan
    Each state having a Class I area within its borders or emissions 
that may affect visibility in a Class I area must develop a long-term 
strategy for making reasonable progress towards the national visibility 
goal. As explained in Section 3 of this notice, reasonable progress is 
achieved when all states contributing to visibility impairment in

[[Page 47412]]

a Class I area are implementing the measures determined--through 
application of the four statutory factors to sources of visibility 
impairing pollutants--to be necessary to make reasonable progress.\146\ 
Each state's long-term strategy must include the enforceable emissions 
limitations, compliance schedules, and other measures that are 
necessary to make reasonable progress.\147\ All new (i.e., additional) 
measures that are the outcome of four-factor analyses are necessary to 
make reasonable progress and must be in the long-term strategy. If the 
outcome of a four-factor analysis and analysis of other measures 
necessary to make reasonable progress is that no new measures are 
reasonable for a source, that source's existing measures are necessary 
to make reasonable progress, unless the state can demonstrate that the 
source will continue to implement those measures and will not increase 
its emissions rate. Existing measures that are necessary to make 
reasonable progress must also be in the long-term strategy. In 
developing its long-term strategies, a state must also consider the 
five additional factors in section 51.308(f)(2)(iv). As part of its 
reasonable progress determinations, the state must describe the 
criteria used to determine which sources or group of sources were 
evaluated in a four-factor analysis for the second implementation 
period and how the four factors were taken into consideration in 
selecting the emissions reduction measures for inclusion in the long-
term strategy.\148\
---------------------------------------------------------------------------

    \146\ 40 CFR 51.308(f)(2)(i).
    \147\ 40 CFR 51.308(f)(2).
    \148\ 40 CFR 51.308(f)(2)(iii).
---------------------------------------------------------------------------

    The consultation requirements of section 51.308(f)(2)(ii) provide 
that states must consult with other states that are reasonably 
anticipated to contribute to visibility impairment in a Class I area to 
develop and coordinate emissions management strategies containing the 
emissions reduction measures that are necessary to make reasonable 
progress. Section 51.308(f)(2)(ii)(A) and (B) require states to 
consider the emissions reduction measures identified by other states as 
necessary for reasonable progress and to include agreed upon measures 
in their SIPs, respectively. Section 51.308(f)(2)(ii)(C) speaks to what 
happens if states cannot agree on what measures are necessary to make 
reasonable progress.
    The following sections summarize Arizona's long-term strategy for 
the second planning period, as set forth in the 2022 Arizona Regional 
Haze Plan. The EPA's evaluation with respect to the requirements of 
51.308(f)(2) is provided in Section IV.E.2.
a. Point Sources
i. Source Selection
    PM is composed of different chemical constituents, including 
sulfates, nitrates, organic carbon, elemental carbon, coarse mass, and 
soil dust (``PM species'' or ``species''). ADEQ focused its source 
evaluation on the PM species that dominate visibility impairment at its 
Class I areas.\149\ ADEQ evaluated light extinction for PM species by 
calculating total light extinction \150\ and anthropogenic extinction 
\151\ for each species on the most impaired days at its Class I areas. 
ADEQ indicated that when the anthropogenic portion of the impact is 
considered, the sulfate, nitrate, and coarse mass species collectively 
constitute 80 percent of total extinction on average across the Arizona 
Class I areas (ranging from 72.3 percent at the PEFO1 monitor to 88.8 
percent at the CHIR1 monitor).\152\ ADEQ also noted that, while organic 
carbon mass and light absorbing carbon account for more than 10 percent 
of the anthropogenic light extinction impact for at least one of the 
Class I areas, the emissions that contribute to these species are 
primarily from biogenic, wildfires, and onroad sources, for which the 
State has limited available control opportunities. Based on this 
analysis, ADEQ determined that sulfate, nitrate, and coarse mass are 
the three species that should be evaluated for source controls during 
this planning period in order to maximize the visibility benefit of 
controls. SO2 emissions are a precursor to the formation of 
sulfate, and NOX emissions are a precursor to the formation 
of nitrate. Coarse mass emissions involve particulates with an 
aerodynamic diameter between 10 and 2.5 microns (i.e., PM10 
less PM2.5). Because coarse mass is not commonly included in 
emissions inventories, states generally use particulate matter with an 
aerodynamic diameter under 10 microns (PM10) as a surrogate 
for coarse mass. Therefore, ADEQ conducted its screening based on 
NOX, SO2, and PM10 emissions.
---------------------------------------------------------------------------

    \149\ 2022 Arizona Regional Haze Plan, Section 8.2.1.
    \150\ Id., Appendix C, Table 3.
    \151\ Id. at Table 4.
    \152\ Id. at Table 5.
---------------------------------------------------------------------------

    Arizona used the Q/d method to identify sources that are reasonably 
expected to contribute to visibility impairment at any Class I area. 
ADEQ used a Q/d threshold of 10 (combined NOX, 
SO2 and PM10 emissions) based on the 2014 
National Emissions Inventory (NEI) Version 2 (``2014v2'') emissions. 
ADEQ's approach included additional steps in order to screen out 
processes within the identified sources that have installed or will 
install ``effective controls'' prior to the end of the second planning 
period.\153\ ADEQ evaluated 2018 operational and emissions data to 
determine which processes have an effective control installed or 
incorporated within the last five years or will install or incorporate 
an effective control prior to 2028.\154\
---------------------------------------------------------------------------

    \153\ A full description of the methodology and determinations 
of effective controls and their treatment are included in Appendix C 
of the 2022 Arizona Regional Haze Plan. Figure 8-1 of the 2022 
Arizona Regional Haze Plan presents a flowchart of ADEQ's major 
point source screening process.
    \154\ Arizona Regional Haze Plan, Appendix C, Section C2.2.1.2.
---------------------------------------------------------------------------

    ADEQ used following the criteria for determining what constitutes 
an effective control: (1) the control was installed within the last 
five years of this analysis (i.e., during or since 2014) or will be 
installed prior to 2028; (2) the control was installed to meet (a) PSD 
requirements (or is otherwise considered a to be equivalent to the best 
available control technology (BACT)), (b) BART requirements (including 
BART reconsiderations and better-than-BART determinations),\155\ (c) 
Regional Haze 1st planning period Reasonable Progress, requirements, or 
(d) other SIP requirements to achieve NAAQS compliance; and (3) process 
emissions must be controlled through routing those emissions through a 
newly constructed or recently upgraded pollution control device or 
``taking emission limits that would otherwise equate to the 
installation of a pollution control device.'' \156\
---------------------------------------------------------------------------

    \155\ Pursuant to 40 CFR 51.308(e)(2), States have the 
flexibility to adopt alternatives that provide greater reasonable 
progress towards natural visibility conditions than BART for one or 
more subject-to-BART sources (commonly known as ``better-than-BART'' 
alternatives).
    \156\ Arizona Regional Haze Plan Appendix C, p. 30.
---------------------------------------------------------------------------

    ADEQ further determined that the application of the effective 
control screening should be applied at the process level as opposed to 
the facility-wide level. Given an increase in resolution at the process 
level as compared to the unit level, ADEQ determined that examining 
facility processes was the most appropriate level of resolution for 
determining which emission sources at a facility would undergo a four-
factor control determination. Additionally, given that some permitted 
sources submit emissions inventories containing hundreds of processes, 
including many that emit low levels of pollutants, ADEQ

[[Page 47413]]

determined that it was unnecessary to perform a control evaluation on 
all processes at each facility, but that at least the largest 80 
percent of pollutant- and process-specific emissions at a source should 
be considered.
    As shown in Table 3 of this document, ADEQ determined that 55 
processes within the identified sources were effectively 
controlled.\157\ These include certain processes where no control has 
been installed within the last five years, but where new emissions 
limits were established, such as Tucson Electric Power (TEP) Company 
Irvington Generating Station (IGS) Unit 4 and AEPCO Apache Generating 
Station Unit 2, both of which converted from coal to natural gas as 
part of better-than-BART alternatives during the first planning period. 
ADEQ then screened out these effectively controlled processes from 
further consideration and indicated that these effectively controlled 
processes will be reevaluated in future rounds of Regional Haze 
planning.
---------------------------------------------------------------------------

    \157\ Id. at Exhibit CI.

             Table 3--List of Effective Controls Identified by ADEQ for Arizona Major Point Sources
----------------------------------------------------------------------------------------------------------------
                                   Unit/process
           Facility                description      Control program                    Comments
----------------------------------------------------------------------------------------------------------------
AEPCO--Apache Generating        Steam Unit 1 Gas.  Regional Haze--    NOX limit of 0.056 pounds per million
 Station.                                           BART Alternative.  British thermal unit (lb/MMBtu)
                                                                       standalone and 0.1 lb/MMBtu combined ST1/
                                                                       GT1 and a 30-calendar day average of
                                                                       1,205 lb/day, PM10 limit of 0.0075 lb/
                                                                       MMBtu, and SO2 limit of 0.00064 lb/MMBtu.
AEPCO--Apache Generating        Steam Unit 2 Gas.  Regional Haze--    Conversion from coal to natural gas with
 Station.                                           BART Alternative.  NOX limit of 0.085 lb/MMBtu 30-day
                                                                       average, SO2 limit of 0.00064 lb/MMBtu 30-
                                                                       day average, PM10 limit of 0.008 lb/MMBtu
                                                                       30-day average.
AEPCO--Apache Generating        Steam Unit 2 Coal  Regional Haze--    Conversion from coal to natural gas w/NOX
 Station.                                           BART Alternative.  limit of 0.085 lb/MMBtu 30-day average,
                                                                       SO2 limit of 0.00064 lb/MMBtu 30-day
                                                                       average, PM10 limit of 0.008 lb/MMBtu 30-
                                                                       day average.
AEPCO--Apache Generating        Steam Unit 3 Coal  Regional Haze--    Selective non-catalytic reduction (SNCR)
 Station.                                           BART Alternative.  installation w/a NOX 30-day average limit
                                                                       of 0.23 lb/MMBtu.
AEPCO--Apache Generating        Steam Unit 3 Gas.  Regional Haze--    SNCR installation w/a NOX 30-day average
 Station.                                           BART Alternative.  limit of 0.23 lb/MMBtu.
AEPCO--Apache Generating        Gas Combust        Regional Haze--    NOX limit of 0.056 lb/MMBtu standalone and
 Station.                        Turbine #1.        BART Alternative.  0.1 lb/MMBtu combined ST1/GT1 and a 30-
                                                                       calendar day average of 1,205 lb/day,
                                                                       PM10 limit of 0.0075 lb/MMBtu, and SO2
                                                                       limit of 0.00064 lb/MMBtu.
APS--Cholla Power Plant.......  Coal Combustion    Regional Haze--    Cease operation or convert unit from coal
                                 In Steam Unit #1.  BART.              to natural gas by April 30, 2025, with
                                                                       20% annual capacity factor.
APS--Cholla Power Plant.......  Coal Combustion    Regional Haze--    Permanently shut down April 1, 2016.
                                 in Steam Unit #2.  BART.
APS--Cholla Power Plant.......  Coal Combustion    Regional Haze--    Permanently cease coal burning by April
                                 in Steam Unit #3.  BART.              30, 2025. Natural gas option with less
                                                                       than 20% average annual capacity factor
                                                                       (NOX, SO2, and PM10 emissions limits
                                                                       specified).
APS--Cholla Power Plant.......  Coal Combustion    Regional Haze--    Permanently cease coal burning by April
                                 in Steam Unit #4.  BART.              30, 2025. Natural gas option with less
                                                                       than 20% average annual capacity factor
                                                                       (NOX, SO2, and PM10 emissions limits
                                                                       specified).
Asarco--Hayden Smelter........  Flash Furnace,     SIP Action--Pb,    Converter retrofit & HSA Lime Injection/
                                 Converter.         SO2.               Baghouse.
Asarco--Hayden Smelter........  Paved Road         SIP Action--Pb...  Limits on Lead Bearing Fugitive Dust from
                                 Traffic.                              the Hayden smelter.
Asarco--Hayden Smelter........  Product Dryer      SIP Action--Pb,    Converter retrofit & HSA Lime Injection/
                                 Baghouses.         SO2.               Baghouse.
Asarco--Hayden Smelter........  Storage &          SIP Action--Pb...  Limits on Lead Bearing Fugitive Dust from
                                 Handling.                             the Hayden smelter.
Asarco--Hayden Smelter........  Unpaved Road       SIP Action--Pb...  Limits on Lead Bearing Fugitive Dust from
                                 Traffic.                              the Hayden smelter.
Asarco--Hayden Smelter........  Flash Furnace/     SIP Action--SO2..  Flash furnace fugitive SO2 capture and
                                 Converter                             control improvements made as part of the
                                 Primary                               converter retrofit project.
                                 Ventilation--Aci
                                 d Plant Outlet.
Asarco--Hayden Smelter........  Converter Aisle    SIP Action--SO2..  New tertiary ventilation system.
                                 Fugitives.
Asarco--Hayden Smelter........  Fines Crushing     SIP Action--Pb...  Limits on Lead Bearing Fugitive Dust from
                                 Circuit.                              the Hayden smelter.
Asarco--Hayden Smelter........  Flash Furnace      SIP Action--SO2..  Flash furnace fugitive SO2 capture and
                                 Fugitives.                            control improvements made as part of the
                                                                       converter retrofit project.
Asarco--Hayden Smelter........  Flash Furnace      SIP Action--SO2..  Flash furnace fugitive SO2 capture and
                                 Baghouse Outlet.                      control improvements made as part of the
                                                                       converter retrofit project.
Asarco--Hayden Smelter........  Peirce Smith       SIP Action--SO2..  New tertiary ventilation system.
                                 Converters.
Asarco--Hayden Smelter........  Peirce Smith       SIP Action--Pb,    Converter retrofit & HSA Lime Injection/
                                 Converters.        SO2.               Baghouse.
Asarco--Hayden Smelter........  Revert Crushing    SIP Action--Pb...  Limits on Lead Bearing Fugitive Dust from
                                 Circuit.                              the Hayden smelter.
Asarco--Hayden Smelter........  Secondary Hood     SIP Action--SO2..  New tertiary ventilation system.
                                 Baghouse.

[[Page 47414]]

 
Asarco--Hayden Smelter........  Tertiary Hood      SIP Action--SO2..  New tertiary ventilation system.
                                 Ventilation
                                 Outlet.
Calportland-Rillito Cement      Preheater & Kiln   Regional Haze--    SNCR installation with a NOX limit of 3.46
 Plant.                          4.                 Reasonable         lb/ton.
                                                    Progress.
Chemical Lime Nelson Plant....  Baghouse.........  Regional Haze--    SNCR NOX limit of 3.80 lb/ton. Use of
                                                    BART.              lower sulfur fuel with SO2 limit of 9.32
                                                                       lb/ton.
Chemical Lime Nelson Plant....  Baghouse.........  Regional Haze--    SNCR NOX limit of 2.61 lb/ton. Use of
                                                    BART.              lower sulfur fuel with SO2 limit of 9.73
                                                                       lb/ton.
Coronado Generating Plant.....  Coal Combustion    Regional Haze--    Selective catalytic reduction (SCR)
                                 Unit 1.            BART.              installation or shut down by 12/31/2025.
                                                                       0.065 lb/MMBtu average NOX limit and
                                                                       0.060 lb/MMBtu average SO2 limit.
                                                                       Additional facility-wide cap on SO2
                                                                       emissions.
Coronado Generating Plant.....  Fuel Oil           Regional Haze--    SCR installation or shut down by 12/31/
                                 Combustion Unit    BART.              2025. 0.065 lb/MMBtu average NOX limit
                                 1.                                    and 0.060 lb/MMBtu average SO2 limit.
                                                                       Additional facility-wide cap on SO2
                                                                       emissions.
Coronado Generating Plant.....  Coal Combustion    Regional Haze--    SCR installation in June 2014.
                                 Unit 2.            BART.
Coronado Generating Plant.....  Fuel Oil           Regional Haze--    SCR installation in June 2014.
                                 Combustion Unit    BART.
                                 2.
Freeport McMoran Miami Smelter  Smelting: Isa &    SIP Action--SO2..  2018 environmental upgrades included
                                 Elf.                                  capture of anode vessel process
                                                                       emissions, routing to baghouse and
                                                                       caustic scrubber.
Freeport McMoran Miami Smelter  Captured           SIP Action--SO2..  Anode process emissions routed through
                                 Converter                             baghouse and caustic scrubber, Converter
                                 Fugitives and                         fugitive emissions routed through caustic
                                 Anode Process                         scrubber.
                                 Emissions.
Freeport McMoran Miami Smelter  Collected          SIP Action--SO2..  Vent fume system, including Wet
                                 Fugitives.                            Electrostatic Precipitator (ESP) and
                                                                       caustic scrubber.
Freeport McMoran Miami Smelter  Bypass Stack.....  SIP Action--SO2..  Bypass stack subject to facility-wide SO2
                                                                       limit in SO2 and permit.
Freeport McMoran Miami Smelter  Smelting           SIP Action--SO2..  Fugitive originating from IsaSmelt vessel,
                                 Fugitives.                            electric furnace, converters, and anode
                                                                       vessels, each of which have emissions
                                                                       capture and control systems.
Freeport McMoran Miami Smelter  Natural Gas        SIP Action--SO2..  Majority of smelter natural gas combustion
                                 Combustion.                           occurs within IsaSmelt, Electric Furnace,
                                                                       Converters and Anode Vessels and is co-
                                                                       mingled with process gas which is routed
                                                                       to the various control devices.
                                                                       Insignificant emissions originating from
                                                                       uncontrolled space heaters, small water
                                                                       heaters, etc.
Freeport McMoran Miami Smelter  Anode Refining...  SIP Action--SO2..  2018 environmental upgrades included
                                                                       capture of anode vessel process
                                                                       emissions, routing to baghouse and
                                                                       caustic scrubber.
Phoenix Cement--Clarkdale.....  Raw Mill/Kiln....  Regional Haze--    SNCR installation with a NOX limit of 2.67
                                                    Reasonable         lb/ton.
                                                    Progress.
Phoenix Cement--Clarkdale.....  Coal Milling.....  Regional Haze--    SNCR installation with a NOX limit of 2.67
                                                    Reasonable         lb/ton.
                                                    Progress.
Tucson Electric Power--         U1 Boiler--        PSD BACT.........  Replacement of unit with 10 upgraded
 Irvington.                      Natural Gas.                          reciprocating internal combustion engines
                                                                       (RICE) engines and a combined annual NOX
                                                                       limit of 170 tons per year (tpy).
Tucson Electric Power--         U2 Boiler--        PSD BACT.........  Replacement of unit with 10 upgraded RICE
 Irvington.                      Natural Gas.                          engines and a combined annual NOX limit
                                                                       of 170 tpy.
Tucson Electric Power--         U4 Boiler--        Regional Haze--    Fuel switch with a 0.25 lb/MMBtu NOX
 Irvington.                      Natural Gas.       BART Alternative.  limit, 0.57 lb/MMBtu SO2 limit, and 0.010
                                                                       lb/MMBtu PM10 limit.
Tucson Electric Power--         IGT1-Turbine--Nat  PSD BACT.........  Replacement of unit with 10 upgraded RICE
 Irvington.                      ural Gas.                             engines and a combined annual NOX limit
                                                                       of 170 tpy.
Tucson Electric Power--         IGT2-Turbine--Nat  PSD BACT.........  Replacement of unit with 10 upgraded RICE
 Irvington.                      ural Gas.                             engines and a combined annual NOX limit
                                                                       of 170 tpy.
----------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Appendix C, Exhibit CI.

    ADEQ then recalculated Q/d using a threshold of 10 for each 
facility utilizing the remaining processes and 2018 data.
    Based on the source screening results, ADEQ determined that the 11 
permitted sources listed in Table 4 of this document would undergo a 
four-factor analysis.\158\
---------------------------------------------------------------------------

    \158\ 2022 Arizona Regional Haze Plan, Table 8-2.

                                    Table 4--Arizona Source Screening Results
----------------------------------------------------------------------------------------------------------------
                 Facility                     Q (tpy)       d (km)        Q/d           Nearest Class I area
----------------------------------------------------------------------------------------------------------------
ASARCO LLC--Mission Complex...............        1,254           42           30  Saguaro National Park.
ASARCO LLC--Ray Operations................          371           26           14  Superstition Wilderness Area.

[[Page 47415]]

 
CalPortland--Rillito Cement Plant.........          246            8           30  Saguaro National Park.
Drake Cement LLC..........................          375           22           17  Sycamore Canyon Wilderness
                                                                                    Area.
El Paso Natural Gas--Willcox Compressor             321           27           12  Chiricahua Wilderness Area.
 Station.
El Paso Natural Gas--Williams Compressor            786           19           40  Sycamore Canyon Wilderness
 Station.                                                                           Area.
Freeport-McMoran--Morenci.................        2,768           54           52  Gila Wilderness Area.
Freeport-McMoran--Sierrita Mine...........          869           42           21  Saguaro National Park.
Phoenix Cement--Clarkdale.................          136           10           14  Sycamore Canyon Wilderness
                                                                                    Area.
Tucson Electric Power Co--Irvington.......          444           16           28  Saguaro National Park.
Tucson Electric Power Co--Springerville...       17,044           50          339  Mount Baldy Wilderness Area.
----------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Table 8-2. The Q and Q/d values shown here exclude those processes that
  ADEQ screened out based on a finding that they were effectively controlled.

ii. Overall Approach to Four-Factor Analyses
    For cost calculation interest rates, ADEQ requested that the 
sources undergoing a four-factor analysis provide source specific 
lending/interest rates in line with the general recommendations of the 
7th Edition of the EPA Control Cost Manual.\159\ In the absence of 
source-specific information, ADEQ relied on a 4.75 percent interest 
rate developed by analyzing and averaging historical bank prime rate 
data. ADEQ looked at 3-year average bank prime rates for the periods of 
2017-2019 (4.83 percent) and April 2018-March 2020 (4.78 percent). 
These dates were chosen as they were the most recent data at the time 
of the analysis. ADEQ determined, based on these 3-year averages, that 
a 3-year average bank prime rate of 4.75 percent was appropriate. ADEQ 
indicates that the use of a 3-year average was more appropriate than 
the utilization of the bank prime rate at a singular point in time due 
to the variability that can occur in bank prime rates over time. ADEQ 
also performed an analysis to determine a reasonable cost-effectiveness 
(cost/ton) threshold for Arizona emissions sources evaluated under the 
four-factor analysis in the regional haze second planning period, based 
on the cost-effectiveness values for controls required in regional haze 
SIP revisions from the first planning period. ADEQ indicated that it 
found that none of the implemented cost-effectiveness values during the 
first planning period exceeded $5,300/ton. Adjusting the cost for 
inflation to 2019 dollars based on Chemical Engineering Plant Cost 
Index values,\160\ ADEQ determined that any controls having an average 
cost-effectiveness of more than $6,500/ton would be cost excessive and 
could be rejected without further justification.
---------------------------------------------------------------------------

    \159\ 2022 Arizona Regional Haze Plan, Section 8.3.2.
    \160\ Available at https://www.chemengonline.com/site/plant-cost-index/.
---------------------------------------------------------------------------

iii. Summary of Four-Factor Analyses

                Table 5--Summary of Facilities and Processes Evaluated Under Four-Factor Analysis
----------------------------------------------------------------------------------------------------------------
                                                                                                 Projected 2028
                Facility                           Process                   Pollutant           emissions (tpy)
----------------------------------------------------------------------------------------------------------------
ASARCO LLC--Mission Complex............  Trucks hauling ore and      PM10.....................               713
                                          waste rock.
                                         Rubber tire rigs traveling  PM10.....................                97
                                          on unpaved roads.
ASARCO LLC--Ray Operations.............  Trucks hauling ore and      PM10.....................               158
                                          waste rock.
                                         Miscellaneous vehicles      PM10.....................                87
                                          traveling on unpaved
                                          roads.
                                         Dumps and tailings          PM10.....................                41
                                          windblown dust.
                                         Dozing mine areas, dumps    PM10.....................                21
                                          and stockpiles.
                                         Blasting ore and waste      NOX......................                89
                                          rock.
CalPortland--Rillito Cement Plant......  Clinker From K234--         PM10.....................              62.5
                                          Overhead Crane Building.
                                         Unpaved Roads.............  PM10.....................              51.7
                                         Plant Materials...........  PM10.....................              17.3
                                         Finish Milling--D2-PC.....  PM10.....................               9.5
                                         Iron Stockpile............  PM10.....................               8.5
                                         Finish Milling--D3-1-DC2..  PM10.....................               7.1
                                         Cooler--Kiln 4 H2-GB......  PM10.....................               7.0
                                         Quarry Materials..........  PM10.....................               6.5
                                         Paved Roads...............  PM10.....................               5.8
                                         Mining Operations--         NOX......................               5.7
                                          Blasting.
                                         Quarry Crusher System--B2-  PM10.....................               5.3
                                          DC1.
Drake Cement LLC.......................  Raw Mill and Kiln.........  NOX......................           \a\ 316
El Paso Natural Gas--Willcox Compressor  TURBINE-1.................  NOX......................               134
 Station.
                                         TURBINE-2.................  NOX......................               157
El Paso Natural Gas--Williams            TURBINE-1.................  NOX......................               290
 Compressor Station.
                                         RECIP-1...................  NOX......................               148
                                         RECIP-2...................  NOX......................               170
                                         RECIP-5...................  NOX......................               205
Freeport--McMoran--Morenci.............  Haul Trucks Traveling on    PM10.....................             1,552
                                          Mine Roads.
                                         Other Vehicles Traveling    PM10.....................               229
                                          on Mine Roads.
                                         Loading Ores into Haul      PM10.....................               120
                                          Trucks.

[[Page 47416]]

 
Freeport--McMoran--Sierrita Mine.......  Unpaved Roads.............  PM10.....................               449
                                         Loading Ores into Haul      PM10.....................                82
                                          Trucks.
                                         Sierrita Tailings.........  PM10.....................               171
                                         Blasting Operations.......  NOX......................                97
Phoenix Cement--Clarkdale..............  Rock Sampling and Storage-- PM10.....................              31.4
                                          Raw Storage Piles.
                                         Coal/Coke Handling 2--Coal/ PM10.....................              12.1
                                          Coke Storage Pile.
                                         Gypsum Handling--Gypsum     PM10.....................               7.4
                                          Storage Piles.
                                         Cement Storage--DC510.....  PM10.....................               5.5
                                         Quarry Rds/Blast/Drill--    NOX......................               3.5
                                          Quarry--Blasting.
                                         Raw Storage and Homog2--    PM10.....................               3.1
                                          DC607.
                                         Kiln Feed System--DC409...  PM10.....................               3.0
                                         Clinker Handling and STR3-- PM10.....................               2.8
                                          DC352.
                                         Finish Milling--DC340.....  PM10.....................               2.6
                                         Cement Storage 2--DC512...  PM10.....................               2.6
                                         Raw Mill--DC366...........  PM10.....................               2.2
                                         Rock Reclaimer and TPS--    PM10.....................               2.4
                                          DC205.
                                         Cement Storage 2--DC508...  PM10.....................               2.1
                                         Clinker Handling and STR3-- PM10.....................               2.0
                                          DC350.
                                         Raw Storage and Homog1--    PM10.....................               1.9
                                          DC601.
                                         Clinker Handling and STR1-- PM10.....................               1.9
                                          DC447.
                                         Clinker Cooling--DC445....  PM10.....................               1.7
                                         Clinker Handling and STR3-- PM10.....................               1.6
                                          DC312.
                                         Raw Storage and Homog2--    PM10.....................               1.6
                                          DC224.
                                         Raw Storage and Homog2--    PM10.....................               1.6
                                          DC228.
                                         Raw Storage and Homog2--    PM10.....................               1.6
                                          DC615.
                                         Raw Storage and Homog2--    PM10.....................               1.6
                                          DC616.
                                         Coal/Coke Handling1--DC452  PM10.....................               1.4
                                         Finish Milling--DC341.....  PM10.....................               1.3
                                         Paved Plant Roads.........  PM10.....................               1.2
Tucson Electric Power Co--Irvington....  Unit 3....................  NOX......................               251
Tucson Electric Power Co--Springerville  Unit 1 Boiler.............  PM10.....................                92
                                                                     NOX......................             2,099
                                                                     SO2......................             2,869
                                         Unit 2 Boiler.............  PM10.....................               107
                                                                     NOX......................             2,283
                                                                     SO2......................             2,982
                                         Unit 3 Boiler.............  PM10.....................               158
                                                                     NOX......................             1,019
                                                                     SO2......................             1,036
                                         Unit 4 Boiler.............  PM10.....................                31
                                                                     NOX......................               929
                                                                     SO2......................             1,039
----------------------------------------------------------------------------------------------------------------
\a\ The Plan does not state the projected 2028 emissions for this unit. However, the highest annual facility-
  wide NOX emissions during the baseline period were 316 tpy in 2018, so this may be considered an upper-bound
  of emissions from the Raw Mill and Kiln.
Source: 2022 Arizona Regional Haze Plan, Appendix C.

    ASARCO LLC (Asarco) Mission Complex \161\ is a copper mine located 
in Sahuarita, Arizona. The facility operates an open-pit copper mine, 
two concentrators, and a by-products molybdenum plant. Asarco Mission 
Complex was screened in with a Q/d value of 30, and the nearest Class I 
area is Saguaro National Park at 42 kilometers away. ADEQ identified 
two processes that are subject to the four-factor analysis for Asarco 
Mission Complex: haul trucks hauling ore and waste rock, and rubber 
rigs traveling on unpaved roads. Using information supplied by Asarco, 
ADEQ conducted four-factor analyses for these two processes, the 
results of which are summarized in Table 6 of this document. Based on 
these results, ADEQ determined that the emissions controls that Asarco 
is implementing for the two processes, such as a speed limit of 35 
miles per hour and application of water, reflect current best 
management practices for the mining industry and that it is reasonable 
not to require additional controls during this planning period. 
Although ADEQ did not specify why no other controls were reasonable, 
cost appears to have been the determining factor, as the cost 
effectiveness of all feasible controls exceeded ADEQ's chosen cost-
effectiveness threshold of $6,500/ton.
---------------------------------------------------------------------------

    \161\ 2022 Arizona Regional Haze Plan, Chapter 8.3.3.1 and 
Appendix C, Section C3.3.

[[Page 47417]]



                         Table 6--Summary of Control Options for Asarco Mission Complex
----------------------------------------------------------------------------------------------------------------
                                                                                                       Cost-
                 Process                            Control               Emission reduction       effectiveness
                                                                                                      ($/ton)
----------------------------------------------------------------------------------------------------------------
Truck Hauling Ore and Waste Rock........  Reduce the speed limit for  203.7.....................         $80,544
                                           haul trucks from 35 mph
                                           to 25 mph.
                                          Apply additional water to   71.3......................          12,183
                                           haul roads (outside pit
                                           only).
                                          Apply additional water to   356.5.....................          10,117
                                           haul roads (inside and
                                           outside pit).
                                          Increase freeboard in the   Emissions reductions could             N/A
                                           haul trucks.                not be quantified.
Rubber Tire Rigs Traveling on Unpaved     Reduce the speed limit for  No reduction expected                  N/A
 Non-Haul Roads.                           rubber tire rigs from 35    since average traveling
                                           mph to 25 mph.              speed of rubber tire rigs
                                                                       is 15 mph.
                                          Apply additional water to   49.7......................          18,043
                                           unpaved roads (non-haul
                                           roads only).
                                          Apply additional water to   59.4......................          15,771
                                           unpaved roads (haul roads
                                           non-haul roads only).
                                          Apply and maintain surface  5.1.......................          25,711
                                           gravel on unpaved non-
                                           haul roads (decreasing
                                           the silt content from
                                           6.9% to 6.4%).
                                          Paving unpaved non-haul     73.7......................          47,295
                                           roads.
----------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Appendix C, Section C.3.3.

    Asarco Ray Operations is located near Kearny, Arizona and consists 
of an open pit mine, concentrator, solvent extraction-electrowinning 
operation, and associated maintenance, warehouse, and administrative 
facilities.\162\ The facility was screened in with a Q/d value of 14, 
and the nearest Class I area is Saguaro National Park at 26 kilometers 
away. ADEQ identified five processes that are subject to the four-
factor analysis for Asarco Ray Operations: trucks hauling ore and waste 
rock, miscellaneous vehicles traveling on unpaved roads, dumps and 
tailings windblown dust, dozing mine areas, dumps and stockpiles, and 
blasting ore and waste rock. Asarco completed and submitted a four-
factor analysis report for the five processes in December 2019 and 
provided additional information in March 2020 through 2021. ADEQ's 
determination in the 2022 Arizona Regional Haze Plan is that the 
emissions controls that Asarco is implementing for these processes, 
such as a speed limit of 35 miles per hour, water sprays, and 
application of chemical dust suppressants (on non-haul roads), reflect 
current best management practices for the mining industry and that it 
is reasonable not to require additional controls during this planning 
period.
---------------------------------------------------------------------------

    \162\ 2022 Arizona Regional Haze Plan, Chapter 8.3.3.2 and 
Appendix C, Section C3.4.
---------------------------------------------------------------------------

    CalPortland Rillito Cement Plant is a portland cement manufacturing 
plant in Rillito, Arizona.\163\ The facility was screened in with a Q/d 
value of 30, and the nearest Class I area is Superstition Wilderness 
Area at 8 kilometers away. ADEQ evaluated potential controls at nine 
emissions sources at the CalPortland Rillito Cement Plant and conducted 
a four-factor analysis for each control that it found to be feasible. 
The results of these analyses are shown in Table 7. While ADEQ's was 
conducting its four-factor analysis for the Rillito facility, 
CalPortland took on a voluntary, enforceable air quality control permit 
condition for the location of its iron stockpile (horseshoe pit, three-
sided artificial windbreak).\164\ ADEQ subsequently found that no other 
controls were reasonable based the statutory four factors. Although 
ADEQ did not specify why no other controls were reasonable, cost 
appears to have been the determining factor, as the cost effectiveness 
of all feasible controls exceeded ADEQ's chosen cost-effectiveness 
threshold of $6,500/ton.
---------------------------------------------------------------------------

    \163\ 2022 Arizona Regional Haze Plan, Chapter 8.3.3.3 and 
Appendix C.
    \164\ ADEQ Air Quality Control Permit #85424 Attachment C 
Section XI Regional Haze Requirements of the 2022 Arizona Regional 
Haze Plan. ADEQ has not submit the new permit condition as a SIP 
revision.

                           Table 7--Summary of Control Options for CalPortland Cement
----------------------------------------------------------------------------------------------------------------
                                                                   Technically     Emissions          Cost-
                Source                       Control option       feasible (Y/     reduction    effectiveness ($/
                                                                       N)            (tpy)            ton)
----------------------------------------------------------------------------------------------------------------
Clinker to Overhead Crane Building....  Fabric Filter Baghouse..            N              N/A               N/A
Clinker to Overhead Crane Building....  Full Enclosure..........            Y             9.38           $13,605
Unpaved Road Vehicular Traffic........  Traffic Management Plans            N              N/A               N/A
Unpaved Road Vehicular Traffic........  Additional Watering.....            Y            44.34            23,955
Unpaved Road Vehicular Traffic........  Surface Gravel..........            N              N/A               N/A
Unpaved Road Vehicular Traffic........  Paving..................            N              N/A               N/A
Unpaved Road Vehicular Traffic........  Chemical Dust                       N              N/A               N/A
                                         Suppressant.
Paved Road Vehicular Traffic..........  Cover Haul Trucks.......            N              N/A               N/A
Paved Road Vehicular Traffic..........  Stabilize Unpaved Points            Y                0               N/A
Paved Road Vehicular Traffic..........  Rapid Cleanup of Spills.            N              N/A               N/A
Paved Road Vehicular Traffic..........  Curb or Pave Shoulders..            N              N/A               N/A
Paved Road Vehicular Traffic..........  Street Sweepers.........            Y              1.5            28,146

[[Page 47418]]

 
Material Handling.....................  Water Sprays............            N              N/A               N/A
Material Handling.....................  Baghouse................            N              N/A               N/A
Material Handling.....................  Enclosures..............            N              N/A               N/A
Iron Stockpile........................  Water Application.......            N              N/A               N/A
Iron Stockpile........................  Chemical Dust                       N              N/A               N/A
                                         Suppressant.
Iron Stockpile........................  Artificial Wind Break...            Y                0               N/A
Iron Stockpile........................  Vegetative Wind Break...            Y                0               N/A
Iron Stockpile........................  Compact Piles...........            N              N/A               N/A
Iron Stockpile........................  Cover with Tarps........            N              N/A               N/A
Finish Mill...........................  Improved Baghouses......            Y      15.85-18.26     14,254-16,057
Clinker Cooler........................  Improved Baghouses......            Y            21.19            16,210
Quarry Crusher........................  Improved Baghouses......            Y             5.92            12,099
Blasting..............................  N/A.....................          N/A              N/A               N/A
----------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan Appendix C, Section C.3.5.

    The Drake Cement Paulden facility is a Portland cement 
manufacturing facility in Paulden, Yavapai County, Arizona.\165\ The 
facility was screened in with a Q/d value of 17, and the nearest Class 
I area is Sycamore Canyon Wilderness Area at 22 kilometers away. One 
emission source, the Main Baghouse Raw Mill and Kiln, contributed 
approximately 84 percent of the facility's total NOX, 
SO2, and PM10 combined emissions, and ADEQ 
evaluated this unit for regional haze controls. The Plan does not state 
the projected 2028 emissions for this unit. However, the highest annual 
facility-wide NOX emissions during the baseline period were 
316 tpy in 2018, so this may be considered an upper-bound of emissions 
from the Raw Mill and Kiln. ADEQ indicated that Low NOX 
Burners, Preheater Riser Duct Firing, and SNCR are currently 
implemented at the Drake Cement Paulden facility. The only remaining 
potential control available for implementation at the Paulden facility 
is SCR. Noting that SCR has been employed at only a handful of cement 
plants in Europe and one in the United States, ADEQ concluded that SCR 
was technically infeasible. Despite this, ADEQ conducted a four-factor 
analysis of SCR, using a control efficiency of 65 percent, which 
resulted in a reduction of 83.6 tons per year at approximately $30,521/
ton.\166\ This cost exceeds ADEQ's cost threshold and therefore, ADEQ 
determined that it is reasonable not to require additional controls on 
Drake Cement during this planning period.
---------------------------------------------------------------------------

    \165\ 2022 Arizona Regional Haze Plan, Appendix C, Section C3.6.
    \166\ Drake Cement estimated a cost effectiveness of $28,641/ton 
utilizing a 3 percent interest rate. ADEQ updated the interest rate 
to 4.75 percent for consistency with other four-factor analyses in 
its SIP submittal. The cost is based on a 30-year lifespan of the 
SCR.
---------------------------------------------------------------------------

    EPNG Willcox Compressor Station is a natural gas compressor station 
facility that provides natural gas compression to EPNG's pipeline 
network.\167\ The facility screened in with a Q/d value of 12, and the 
nearest Class I area is Chiricahua Wilderness Area at 27 kilometers 
away. The two units subject to four-factor analysis were TURBINE-1 and 
TURBINE-2, with 2028 emissions of 134.72 and 157.44 tons 
NOX, respectively.
---------------------------------------------------------------------------

    \167\ 2022 Arizona Regional Haze Plan, Chapter 8.3.3.6 and 
Appendix C, Section C3.8.
---------------------------------------------------------------------------

    ADEQ found that EPNG was already implementing Good Combustion 
Practices at both units, and that the following control options would 
be technically feasible: Combustion Liner Upgrade with Dry Low 
NOX (DLN; 68-71 percent control effectiveness) and SCR (77 
percent control effectiveness). The results of ADEQ's analysis of these 
two options are summarized in Table 8 of this document.

                              Table 8--Summary of Control Options for EPNG Willcox
----------------------------------------------------------------------------------------------------------------
                                                                                                       Cost-
                  Process                                  Control                   Emission      effectiveness
                                                                                     reduction        ($/ton)
----------------------------------------------------------------------------------------------------------------
TURBINE-1..................................  Lean Head End Combustion Liner                91.24         $12,764
                                              Upgrade with Dry Low-NOX Control.
                                             SCR................................             106          10,008
TURBINE-2..................................  Lean Head End Combustion Liner               115.82          10,524
                                              Upgrade with Dry Low-NOX Control.
                                             SCR................................             124           8,892
----------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Appendix C, Section C3.8.

    ADEQ determined that neither the Combustion Liner Upgrade with DLN 
nor SCR are cost-effective options because they exceed ADEQ's cost 
threshold. ADEQ found that EPNG should continue to implement Good 
Combustion Practices but did not consider whether or not this measure 
was necessary to make reasonable progress.
    El Paso Natural Gas (EPNG) Williams Compressor Station is a natural 
gas compressor station facility that provides natural gas compression 
to EPNG's pipeline network.\168\ The facility was screened in with a Q/
d value of 40, and the nearest Class I area is Sycamore Canyon 
Wilderness Area at 19 kilometers away. EPNG reviewed NOX 
control options for both the General Electric (GE) gas turbine 
(TURBINE-1, with 2028 emissions of 290.42 tons NOX) and 
three reciprocating engines (RECIP-1, RECIP-2, and RECIP-5, with

[[Page 47419]]

2028 emissions of 148.4, 179.4, and 205.16 tons NOX, 
respectively) located at the Williams Compressor Station.
---------------------------------------------------------------------------

    \168\ 2022 Arizona Regional Haze Plan, Chapter 8.3.3.5 and 
Appendix C, Section C3.7.
---------------------------------------------------------------------------

    Based on information provided by EPNG, ADEQ evaluated the following 
controls for the Williams compressor station TURBINE-1 for 
NOX: Water or Steam Injection, Combustion Liner Upgrade with 
Low NOX Burner Design, Good Combustion Practices, 
EMXTM/SCONOXTM Technology, SCR, and SNCR. Of the 
list, ADEQ determined three of the control options to be technically 
feasible: water or steam injection (74 percent control effectiveness), 
SCR (80 percent control effectiveness), and combustion liner upgrade 
with low NOX burner design (78 percent control 
effectiveness). The results of this analysis are summarized in Table 9 
of this document. After the evaluation of these costs of compliance, 
ADEQ determined that the control options were not cost effective, and 
that the continued use of Good Combustion Practices is reasonable for 
TURBINE-1. ADEQ did not determine whether this measure was necessary to 
make reasonable progress.
    Additionally, the following controls were evaluated for the three 
Williams compressor station reciprocating engines: SCR, Air-Fuel Ratio 
Adjustment with High Energy Ignition, Low-Emission Combustion (LEC) 
Retrofits, Replacement of Three Engines with one Low NOX 
Emissions Gas Turbine, Replacement of Three Engines with Electric 
Motors or a Gas Turbine, and Good Combustion Practices. The results of 
ADEQ's four-factor analysis for the engines are summarized in Table 9 
of this document. Based on these results, ADEQ found that all LEC 
options were cost-effective for every engine based on average cost-
effectiveness. However, ADEQ also found that the incremental cost 
effectiveness of requiring LEC-3 on RECIP-1 as compared to requiring 
LEC-2 ($11,120/ton) was ``cost-excessive.'' Therefore, while ADEQ 
determined that LEC-3 was necessary to make reasonable progress for 
RECIP-2 and RECIP-5, it selected a less stringent control, LEC-2, for 
RECIP-1. ADEQ also found that replacement of the three engines with a 
gas turbine would be cost-effective but did not adopt this option due 
to issues and uncertainties with this option, such as the need for 
operational flexibility to control pipeline flowrate changes and a 
potential increase in fuel usage and emissions during low flow 
conditions.\169\
---------------------------------------------------------------------------

    \169\ Id. at 126-127.

                              Table 9--Summary of Control Options for EPNG Williams
----------------------------------------------------------------------------------------------------------------
                                                                                                       Cost-
                  Process                                  Control                   Emission      effectiveness
                                                                                     reduction        ($/ton)
----------------------------------------------------------------------------------------------------------------
TURBINE-1..................................  Water Injection....................          201.54          $6,536
                                             Steam Injection....................          201.54           7,601
                                             Combustion Liner Upgrade and Low              213.5           8,775
                                              NOX Burner Design.
                                             SCR................................             219           8,051
RECIP-1....................................  Air-Fuel Ratio Adjustment with High           20.67           2,484
                                              Energy Ignition.
                                             LEC-1..............................           76.46           4,058
                                             LEC-2..............................          116.30           4,581
                                             LEC-3..............................          131.45           5,334
                                             SCR................................          119.18           5,782
                                             Replacement with Electric Motors...          140.21          20,880
RECIP-2....................................  LEC-1..............................           74.36           4,172
                                             LEC-2..............................          127.42           4,181
                                             LEC-3..............................          147.59           4,751
                                             SCR................................          135.37           5,553
                                             Replacement with Electric Motors...          159.26          23,301
RECIP-5....................................  LEC-1..............................           87.51           3,645
                                             LEC-2..............................          181.86           2,977
                                             LEC-3..............................          217.72           3,302
                                             SCR................................          202.70           4,409
                                             Replacement with Electric Motors...          238.47          27,011
RECIP-1, 2, & 5............................  Replacement of Three Engines with            484.21           3,905
                                              Low NOX Emissions Gas Turbine.
----------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Appendix C, Section C.3.7.

    Freeport-McMoRan Morenci Complex is located in Greenlee County, 
Arizona and consists of three major operations: mining operations, 
including the drilling and blasting of ore in open-pit copper mines, 
three in-pit crushers and an ore conveying system, the Morenci 
Concentrator and Metcalf Concentrator operations for production of 
copper and molybdenum concentrates through conventional milling and 
froth flotation operations, and the Metcalf Mine-for-Leach (MFL) plant 
and five Solution Extraction and four Electrowinning facilities (SX/EW) 
operations for production of high quality copper cathodes through 
leaching and hydrometallurgy.\170\ The facility was screened in with a 
Q/d value of 52 and the nearest Class I area is Gila Wilderness Area at 
54 kilometers away.
---------------------------------------------------------------------------

    \170\ 2022 Arizona Regional Haze Plan, Chapter 8.3.3.7 and 
Appendix C, Section C3.9.
---------------------------------------------------------------------------

    ADEQ identified two processes that are subject to the four-factor 
analysis for Freeport-McMoRan Morenci: haul trucks and other vehicles 
travel on mine roads and loading ore into haul trucks. Using 
information supplied by Freeport-McMoRan, ADEQ conducted four-factor 
analyses for these two processes, the results of which are summarized 
in Table 10 of this document. Based on these results, ADEQ determined 
that the emissions controls Freeport is already implementing for the 
two processes, such as a speed limit of 35 miles per hour and 
application of water, reflect current best management practices for the 
mining industry, and that it is reasonable not to require additional 
controls during this planning period. Although ADEQ did not specify why 
it found that no other controls were reasonable, cost appears to have 
been the determining factor, as the cost effectiveness of all feasible 
controls

[[Page 47420]]

exceeded ADEQ's chosen threshold of $6,500/ton.

                        Table 10--Summary of Control Options for Freeport-McMoRan Morenci
----------------------------------------------------------------------------------------------------------------
                                                                                                       Cost-
               Process                         Control                 Emission reduction          effectiveness
                                                                                                      ($/ton)
----------------------------------------------------------------------------------------------------------------
Haul Trucks and Other Vehicles         Reduce the speed limit   427.............................        $383,018
 Traveling on Mine Roads.               for haul trucks to 25
                                        mph.
                                       Apply additional water   890.8...........................          10,949
                                        to unpaved mine roads.
                                       Increase freeboard in    Not quantifiable................             N/A
                                        the haul trucks.
Loading Ores into Haul Trucks........  Apply additional water   52.06...........................         406,990
                                        to ores.
                                       Ceasing operations       0.06............................      14,625,548
                                        during high wind hours.
----------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Appendix C, Section C.3.9.

    Freeport-McMoRan Sierrita Complex is located in southern Pima 
County, Arizona and consists of three major operations: mining 
operations, including the drilling and blasting of ore in open-pit 
copper mines, the Sierrita concentrator operations for production of 
copper and molybdenum concentrates, and the run of mine (ROM) oxide-
leaching plant and the Twin Buttes SX/EW operations for production of 
high quality copper cathodes.\171\ The facility was screened in with a 
Q/d value of 21, and the nearest Class I area is Saguaro National Park 
at 42 kilometers away. ADEQ identified four processes that are subject 
to the four-factor analysis for the Freeport-McMoRan Sierrita complex: 
vehicle travel on unpaved roads, tailings, loading/unloading ore into 
haul trucks, and blasting operations. Using information supplied by 
Freeport-McMoRan, ADEQ conducted four-factor analyses for these four 
processes, the results of which are summarized in Table 11 of this 
document. Based on these results, ADEQ determined that the emissions 
controls Freeport-McMoRan is already implementing, such as a speed 
limit of 35 miles per hour and water application, reflect current best 
management practices for the mining industry, and that it is reasonable 
not to require additional controls during this planning period. 
Although ADEQ did not specify why it found that no other controls were 
reasonable, cost appears to have been the determining factor, as the 
cost effectiveness of all feasible controls exceeded ADEQ's chosen 
threshold of $6,500/ton.
---------------------------------------------------------------------------

    \171\ 2022 Arizona Regional Haze Plan, Chapter 8.3.3.8 and 
Appendix C, Section C3.10.

                       Table 11--Summary of Control Options for Freeport-McMoRan Sierrita
----------------------------------------------------------------------------------------------------------------
                                                                                                       Cost-
               Process                         Control                 Emission reduction          effectiveness
                                                                                                      ($/ton)
----------------------------------------------------------------------------------------------------------------
Vehicle Travel on Unpaved Mine Roads.  Reduce the speed limit   124.............................        $233,539
                                        from 34.5 mph to 25
                                        mph.
                                       Apply additional water   224.7...........................          12,021
                                        to unpaved roads
                                        (increasing the
                                        control efficiency
                                        from 90% to 95%).
                                       Increase freeboard in    Emissions reductions could not               N/A
                                        the haul trucks.         be quantified.
Loading Ores into Haul Trucks........  Apply water to ores to   57.73...........................         240,703
                                        increase the moisture
                                        content from 2% to
                                        4.8%.
                                       Ceasing loading          0.66............................       8,081,366
                                        operations during high
                                        wind hours.
Emissions from Tailings..............  No feasible controls...  N/A.............................             N/A
Blasting Operations..................  No feasible controls...  N/A.............................             N/A
----------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Appendix C, Section C.3.10.

    Phoenix Cement Clarkdale Facility is a Portland cement plant and 
quarry near Clarkdale, Arizona that is owned by an enterprise division 
of the Salt River Pima-Maricopa Indian Community.\172\ The facility was 
screened in with a Q/d value of 14, and the nearest Class I area is 
Sycamore Canyon Wilderness Area at 10 kilometers away. As shown in 
Table 3 of this document, ADEQ screened out the raw mill/kiln and coal 
milling emissions sources because they were required to install SNCR as 
part of the first implementation period of the Regional Haze Rule and 
were deemed effectively controlled. The remaining emissions sources 
subject to a four-factor analysis included: raw storage piles, coal/
coke storage piles, gypsum storage piles, paved plant roads, quarry 
blasting, and material handling processes. Based on the results of 
these analyses, which are summarized in Table 12 of this document, ADEQ 
determined that no new controls were reasonable. Although ADEQ did not 
specify its reasoning, cost appears to have been the determining 
factor, as the cost effectiveness of all feasible controls exceeded 
ADEQ's cost-effectiveness threshold of $6,500/ton.
---------------------------------------------------------------------------

    \172\ 2022 Arizona Regional Haze Plan, Chapter 8.3.3.9 and 
Appendix C, Section C3.11.

[[Page 47421]]



                        Table 12--Summary of Control Options for Phoenix Cement Clarkdale
----------------------------------------------------------------------------------------------------------------
                                                                                                       Cost-
                 Process                            Control               Emission reduction       effectiveness
                                                                                                      ($/ton)
----------------------------------------------------------------------------------------------------------------
Raw Storage Piles.......................  Enclosure.................  28.31.....................        $154,422
                                          Increase Moisture Content.  Technically Infeasible....             N/A
                                          Cover with Tarps..........  Technically Infeasible....             N/A
Coal/Coke Storage Pile..................  Enclosure.................  10.94.....................         228,410
                                          Increase Moisture Content.  Technically Infeasible....             N/A
Gypsum Storage Piles....................  Enclosure.................  6.64......................          44,441
                                          Increase Moisture Content.  Technically Infeasible....             N/A
                                          Cover with Tarps..........  Technically Infeasible....             N/A
Paved Plant Roads.......................  Berm Installation.........  Already Implemented.......             N/A
                                          Curbing/Paving or Shoulder  Already Implemented.......             N/A
                                           Stabilization.
                                          Curbing with Gutters......  Already Implemented.......             N/A
                                          Traffic Rerouting.........  Already Implemented.......             N/A
                                          Storm Water Drainage......  Already Implemented.......             N/A
                                          Street Sweepers...........  Already Implemented.......             N/A
                                          Watering..................  1.10......................          77,438
Quarry Blasting.........................  N/A.......................  N/A.......................             N/A
Material Handling Processes.............  Fabric Filters............  Already Implemented.......             N/A
----------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Appendix C, Section C.3.11.

    Tucson Electric Power (TEP) Company Irvington Generating Station 
(IGS) is located in Tuscon, Arizona and includes two fossil fuel-fired 
electric utility steam-generating units, designated as Units 3 and 4; 
two simple cycle combustion turbines; ten RICE; and various ancillary 
units used to produce electricity for consumers.\173\ The facility is 
permitted by the Pima Department of Environmental Quality (PDEQ), and 
was screened in with a Q/d value of 28, with the nearest Class I area 
16 kilometers away at Saguaro National Park. As shown in Table 3, ADEQ 
screened out IGS Unit 4 as effectively controlled based on the fact 
that it was subject to a ``better-than-BART'' alternative 
determination, and the simple cycle turbines were replaced with ten 
RICE engines, leaving only Unit 3 subject to a four-factor analysis.
---------------------------------------------------------------------------

    \173\ 2022 Arizona Regional Haze Plan, Chapter 8.3.3.10 and 
Appendix C, Section C3.12.
---------------------------------------------------------------------------

    On January 18, 2021, TEP submitted a permit application to PDEQ for 
the following voluntary NOX emissions limits for Unit 3: 335 
tons per 12-month rolling total, 753 tons per 36-month rolling total, 
and 1,285 cumulative tons for the remaining life of the unit. The unit 
must shut down permanently before the cumulative limit is exceeded. 
ADEQ updated the four-factor analysis for IGS to include these new 
emissions limits as the baseline emissions for control evaluation, as 
these limits will become enforceable upon finalization of the revised 
IGS permit and approval of ADEQ's regional haze reasonable progress 
determination for IGS by the EPA. Specifically, ADEQ analyzed a range 
of different scenarios under which Unit 3 could meet the emissions 
limits, using a remaining useful life of between 6 and 20 years, as 
shown in Table 13 of this document. Under each of these scenarios, the 
cost of all available control options (low NOX burners 
(LNB), SCR, and SCR+LNB) exceeded ADEQ's cost threshold of $6,500/ton. 
Therefore, ADEQ determined that with the emissions reductions 
associated with the new Unit 3 emissions caps, no additional controls 
are necessary to make reasonable progress towards natural visibility at 
Class I areas during this implementation period. ADEQ also indicated 
that despite the expected emissions reductions at IGS Unit 3, ADEQ 
cannot guarantee emissions reductions for the single year 2028 long-
term strategy (2028LTS) modeling scenario as compared to the baseline. 
However, the limits in place will ensure no degradation as compared to 
the baseline.\174\ Therefore, ADEQ indicated that they are 
conservatively assuming no change in NOX emissions in the 
2028 RPG calculations.
---------------------------------------------------------------------------

    \174\ 2022 Arizona Regional Haze Plan, Appendix B, Section 
B2.2.2.

               Table 13--Summary of Control Options for IGS Unit 3 With Lifetime Cap of 1,285 Tons
----------------------------------------------------------------------------------------------------------------
                                                                                                      Cost-
                 Control                  Remaining useful  Annual emissions      Emission      effectiveness ($/
                                            life (years)     with cap (tpy)    reduction (tpy)        ton)
----------------------------------------------------------------------------------------------------------------
LNB.....................................                20             64.25             33.23           $10,355
                                                        15             85.67             44.30             9,020
                                                        10            128.50             66.45             7,729
                                                         6            214.17            110.75             6,730
SCR.....................................                20             64.25             51.84            26,260
                                                        15             85.67             69.12            23,231
                                                        10            128.50            103.68            20,318
                                                         6            214.17            172.80            18,091
SCR+LNB.................................                20             64.25             58.05            29,253
                                                        15             85.67             77.40            25,791
                                                        10            128.50            116.09            22,482

[[Page 47422]]

 
                                                         6            214.17            193.49            19,938
----------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan Appendix C, Section C3.12.

    TEP Springerville Generating Station (SGS) is located near 
Springerville, Arizona, and consists of four coal-fired electric 
generating units with a combined, nominal, net generating capacity of 
1,620 megawatts.\175\ Units 1 and 2 at SGS are owned and operated by 
TEP. Unit 3 is owned by Tri-State Generation and Transmission 
Association, Inc., and Unit 4 is owned by the Salt River Project 
Agricultural Improvement and Power District. All units are operated by 
TEP. The facility was screened in with a Q/d value of 339, and the 
nearest Class I area is Mount Baldy Wilderness Area at 50 kilometers 
away. Based on information from TEP, ADEQ completed four-factor 
analyses that considered emissions of PM10, NOX, 
and SO2, and associated control technologies, the results of 
which are summarized in Table 14 of this document.
---------------------------------------------------------------------------

    \175\ 2022 Arizona Regional Haze Plan, Chapter 8.3.3.11 and 
Appendix C, Section C3.13.

                    Table 14--Summary of Control Options for Springerville Generating Station
----------------------------------------------------------------------------------------------------------------
                                                                   Technically                         Cost
           Process                  Control         Pollutant     feasible (Y/     Emissions      effectiveness
                                                                       N)       reduction (tpy)      ($/ton)
----------------------------------------------------------------------------------------------------------------
Unit 1.......................  Baghouse........  PM10...........            Y   Already          N/A
                                                                                 Implemented.
                               Wet ESP.........  PM10...........            Y   Not further      N/A.
                                                                                 considered.
                               ESP.............  PM10...........            Y   Not further      N/A.
                                                                                 considered.
                               LNB and overfire  NOX............            Y   Already          N/A
                                air (OFA).                                       Implemented.
                               SNCR............  NOX............            Y   289............  8,079.
                               SCR.............  NOX............            Y   1,375..........  9,194.
                               Current Spray     SO2............          N/A   Already          N/A.
                                Dryer Absorber                                   Implemented.
                                (SDA).
                               Upgraded SDA....  SO2............            Y   1,060..........  883 (20 years),
                                                                                                  828 (30
                                                                                                  years).
                               Dry Sorbent       SO2............            Y   699............  11,976 (20
                                Injection (DSI).                                                  years), 11,544
                                                                                                  (30 years).
                               Circulating Dry   SO2............            Y   2,025..........  8,230 (20
                                Scrubber (CDS).                                                   years), 6,670
                                                                                                  (30 years).
                               Wet Flue Gas      SO2............            Y   2,508..........  8,185 (20
                                Desulfurization                                                   years), 6,393
                                (FGD).                                                            (30 years).
Unit 2.......................  Baghouse........  PM10...........            Y   Already          N/A.
                                                                                 Implemented.
                               Wet ESP.........  PM10...........            Y   Not further      N/A.
                                                                                 considered.
                               ESP.............  PM10...........            Y   Not further      N/A.
                                                                                 considered.
                               LNB and OFA.....  NOX............            Y   Already          N/A.
                                                                                 Implemented.
                               SNCR............  NOX............            Y   364............  6,769.
                               SCR.............  NOX............            Y   1,516..........  8,395.
                               Current SDA.....  SO2............          N/A   Already          N/A.
                                                                                 Implemented.
                               Upgraded SDA....  SO2............            Y   1,062..........  908 (20
                                                                                                  years),853 (30
                                                                                                  years).
                               DSI.............  SO2............            Y   678............  12,843 (20
                                                                                                  years), 12,399
                                                                                                  (30 years).
                               CDS.............  SO2............            Y   2,086..........  7,995 (20
                                                                                                  years), 6,480
                                                                                                  (30 years).
                               Wet FGD.........  SO2............            Y   2,598..........  7,638 (20
                                                                                                  years), 5,944
                                                                                                  (30 years).
Unit 3.......................  Baghouse........  PM10...........            Y   Already          N/A.
                                                                                 Implemented.
                               Wet ESP.........  PM10...........            Y   Not further      N/A.
                                                                                 considered.
                               ESP.............  PM10...........            Y   Not further      N/A.
                                                                                 considered.
                               LNB, OFA and SCR  NOX............            Y   Already          N/A.
                                                                                 Implemented.
                               Low sulfur coal   SO2............          N/A   Not further      N/A.
                                and SDA.                                         considered.
Unit 4.......................  Baghouse........  PM10...........            Y   Already          N/A.
                                                                                 Implemented.
                               Wet ESP.........  PM10...........            Y   Not further      N/A.
                                                                                 considered.
                               ESP.............  PM10...........            Y   Not further      N/A.
                                                                                 considered.
                               LNB, OFA and SCR  NOX............            Y   Already          N/A.
                                                                                 Implemented.
                               Low sulfur coal   SO2............          N/A   Not further      N/A.
                                and SDA.                                         considered.
----------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan Appendix C, Section C3.13.


[[Page 47423]]

    For PM10, ADEQ concluded that because Units 1-3 are 
already equipped with baghouses to control particulate matter 
emissions, further evaluation was not needed. However, ADEQ did not 
consider whether these measures were necessary to make reasonable 
progress and thus a part of their long-term strategy. For electrostatic 
precipitators (ESP) and wet ESP, ADEQ indicated that because ESP 
collection efficiency is comparable to or less than that of the current 
baghouses installed on the units, ADEQ determined that replacing the 
control device with an ESP, while technically feasible, should not be 
considered further.
    For NOX at Units 1 and 2, ADEQ appears to have rejected 
new controls based on costs being above ADEQ's $6,500/ton threshold. 
ADEQ concluded that TEP should continue to implement the existing 
NOX controls but did not consider whether these measures 
were necessary to make reasonable progress and thus should be a part of 
their long-term strategy.
    For NOX at Units 3 and 4, ADEQ concluded that the 
existing controls of combustion controls (LNB+OFA) and SCR is the most 
effective control technology available for NOX for coal 
fired EGUs, and thus, no further analysis for other control 
technologies was needed.
    For SO2 at Units 1 and 2, ADEQ evaluated control costs 
based on a remaining useful life of 20 and 30 years. For CDS and FGD at 
Units 1 and 2, ADEQ indicated that the average cost-effective values 
were near or exceeding ADEQ's cost-effectiveness threshold of $6,500/
ton. ADEQ also calculated incremental costs for these measures that 
ranged from approximately $9,400 to over $13,500. ADEQ indicated that 
due to the high incremental costs and excessive capital cost of the 
controls, CDS and wet FGD were not reasonable. ADEQ also reported the 
results of visibility modeling performed by TEP and stated that, while 
it did not consider visibility impacts as a fifth factor, ``the small 
visibility benefits associated with the modeled SO2 controls 
supports the determination that CDS and wet FGD control options are not 
necessary to make reasonable progress towards natural visibility at 
Class I areas during this implementation period.'' \176\ Therefore, 
ADEQ concluded that it was reasonable to require TEP to upgrade the 
current SDA systems. However, instead of setting a throughput-based 
limit (e.g., lb/MMBtu) corresponding to the upgraded SDA on each unit, 
ADEQ instead chose to set mass-based emissions caps that it determined 
to be ``equivalent'' to upgraded SDA. Specifically, ADEQ set a combined 
emissions limitation for Unit 1 and Unit 2 of 16.1 tons per day limit, 
on a 30-calendar-day rolling averaging period and 3,729 tons per year 
limit, on a 12-month rolling averaging period. ADEQ indicated that 
these caps would ``provide compliance flexibility yet still guarantee 
that each unit is well controlled to protect and improve the visibility 
in Class I areas.'' \177\
---------------------------------------------------------------------------

    \176\ 2022 Arizona Regional Haze Plan, Appendix C, p. 233.
    \177\ Id. at 239.
---------------------------------------------------------------------------

    For SO2 at Units 3 and 4, ADEQ indicated that these 
units were equipped with SDA systems subject to the 2012 Mercury Air 
Toxics Standards (MATS) rule. ADEQ reviewed the most recent 5 years 
(2016-2020) of the SO2 emissions data for SGS. The 
SO2 emissions rates for Unit 3 and Unit 4 ranged from 0.069 
to 0.090 lb/MMBtu and from 0.076 to 0.10 lb/MMBtu on an annual basis, 
respectively. ADEQ indicated that this demonstrates that Unit 3 and 
Unit 4 have continuously complied with the applicable MATS rule 
SO2 emission standard of 0.20 lb/MMBtu. ADEQ therefore 
determined that no new controls are reasonable. ADEQ did not address 
whether or not the existing measures were necessary to make reasonable 
progress and thus should be a part of its long-term strategy.
    For each new control determined to be reasonable, ADEQ submitted 
revised permit conditions for EPA approval into the Arizona portion of 
the SIP. Table 20 of this document provides a summary of controls and 
permit conditions that ADEQ submitted for EPA approval.
b. Nonpoint Sources
i. Source Selection
    ADEQ also determined that it was appropriate to examine nonpoint 
sources (also known as ``area sources'') that emit visibility impairing 
pollutants, based on feedback from stakeholders to consider sources not 
previously controlled in the last round of planning. ADEQ used the 
following steps to select area sources for analysis:
    1. Gather 2014 EPA NEIv2 county-level nonpoint datasets for the 
State of Arizona.
    2. Isolate source classification code (SCC) annual emissions (tpy) 
for PM10 primary, nitrogen oxide, and sulfur dioxide.
    3. Remove PM10 primary emissions from consideration for 
those counties that are not located within 50 km of a Class I area 
since PM10 does not generally experience high transport 
distances.
    4. Sum the remaining SCC-specific PM10 primary, nitrogen 
oxide, and sulfur dioxide annual emissions to calculate ``Q.''
    5. Sort all SCCs from highest to lowest ``Q.''
    6. Determine the ``Q''-threshold which achieved inclusion of the 
SCCs with the largest ``Q's'' until >80 percent of total ``Q'' 
emissions across all SCCs are accounted for (i.e., ``Q'' >13,500 tpy 
includes 6 sectors which account for 81.6 percent of the total 
statewide).
    7. Isolate those sources with a ``Q'' value greater than 13,500 
tpy.
    Following this process, ADEQ identified six nonpoint source 
sectors, as shown in Table 15 of this document. ADEQ removed locomotive 
and biogenic sectors from consideration, due to the majority of 
emissions from these sectors originating from sources which ADEQ is 
generally unable to control.

                                                Table 15--Summary of Selected Non-Point Source Categories
--------------------------------------------------------------------------------------------------------------------------------------------------------
                      SCC                              NOX            PM10             SO2              Q                         Sector
--------------------------------------------------------------------------------------------------------------------------------------------------------
2285002006.....................................          18,045             541              11          18,597  Mobile--Locomotives.
2294000000.....................................               0          14,501               0          14,501  Dust--Paved Road Dust.
2296000000.....................................               0         107,924               0         107,924  Dust--Unpaved Road Dust.
2311020000.....................................               0          15,536               0          15,536  Dust--Industrial/Commercial/
                                                                                                                  Institutional Construction Dust.
2325000000.....................................               0          44,753               0          44,753  Industrial Processes--Mining.
2701220000.....................................          13,912               0               0          13,912  Biogenics--Vegetation and Soil.
--------------------------------------------------------------------------------------------------------------------------------------------------------


[[Page 47424]]

ii. Overall Approach to Four-Factor Analyses
    Because the selected non-point source categories were all 
PM10 sources, ADEQ focused on evaluating PM10 
controls on nonpoint sources in those Class I areas which monitors 
exhibited coarse mass impacts on the most impaired days of greater than 
10 percent of the total anthropogenic extinction during the 2013-2017 
period.\178\ These Class I areas were: Chiricahua National Monument and 
Wilderness Area, Galiuro Wilderness Area, Saguaro National Park, and 
Superstition Wilderness Area. ADEQ indicated that because 
PM10 is generally not transported long distances, it limited 
its evaluation of emissions reduction strategies for paved and unpaved 
roads, mining and quarrying, and non-residential construction on 
nonpoint sources within 50 km of these Class I areas.
---------------------------------------------------------------------------

    \178\ 2022 Arizona Regional Haze Plan, Chapter 8.3.4.
---------------------------------------------------------------------------

    ADEQ used a cost threshold of $5,000/ton for cost effective 
measures for non-point sources.\179\ ADEQ stated that it had selected a 
lower threshold for nonpoint sources compared to point sources, because 
(1) this threshold was used by Colorado in its first planning period 
action for nonpoint sources; (2) ADEQ considers the economic burden of 
control costs higher for nonpoint sources than point sources because 
these are generally smaller sources and less able to afford expensive 
control requirements; and (3) ADEQ ``is able to achieve reasonable 
progress at Arizona Class I areas with the nonpoint control measures 
identified with a $5,000/ton threshold.'' \180\
---------------------------------------------------------------------------

    \179\ Id. at Appendix C, p. 242.
    \180\ Id. at footnote 207.
---------------------------------------------------------------------------

iii. Summary of Four-Factor Analyses
    ADEQ indicated that Industrial/Commercial/Institutional (ICI) 
construction dust was based on general construction activities, 
earthmoving, material handling, transport, and storage, activity on 
disturbed surfaces, and emissions from uncovered haul trucks. ADEQ 
reviewed available controls and considered stakeholder input. ADEQ 
further relied on cost estimates derived from industry representatives 
such as the Associated General Contractors of Arizona (AGCA), vendor 
quotes, and estimates from Pinal County and Maricopa County control 
measure analyses. The results of ADEQ's four-factor analysis for this 
source category are summarized in Table 16 of this document. The 
following control options were determined to be reasonable with cost 
effectiveness values below ADEQ's cost threshold of $5,000/ton: paving 
unpaved parking and staging areas, applying acrylic polymer to unpaved 
parking and staging areas, applying gravel to unpaved parking and 
staging areas, and limiting vehicle speed at work sites to 15 mph with 
signage.

        Table 16--Summary of Control Options for ICI Construction
------------------------------------------------------------------------
                                                             Cost-
         Control measure               Technically     effectiveness ($/
                                        feasible?             ton)
------------------------------------------------------------------------
Require dust control plans         Yes...............  $5,076.
 [permit] for construction or
 land clearing projects.
Require haul trucks to be covered/ Yes...............  N/A.
 Control freeboard and spillage
 from haul vehicles. [material
 transport].
Alter load-in load-out procedures  Yes...............  $25,040-$25,304.
 (e.g., load on downwind side,
 watering, empty loader slowly,
 keep bucket close to truck while
 dumping). [material handling].
Utilize trackout control device,   Yes...............  $24,875 for
 gravel pad, or other means to                          gravel pad--
 stabilize access points where                          $147,248 for
 unpaved traffic surfaces adjoin                        pipe grid.
 paved roads.
Provide for rapid clean-up of mud/ Yes...............  $5,164.
 dirt track out, material spills,
 on paved roads (Street Sweeping).
Apply water to disturbed surfaces  Yes...............  $7,959-$8,770 for
 and dust generating operations                         unpaved traffic
 (pre-watering, operational).                           areas,
                                                        $1,194,223-$1,37
                                                        5,027 for open
                                                        areas.
Apply chemical stabilizers/dust    Yes...............  $3,528 for
 suppressants to unpaved parking                        acrylic polymer,
 and staging areas.                                     $2,139 for
                                                        gravel, $4,820
                                                        for paving.
Limit, restrict or reroute motor   Yes...............  $16,635.
 vehicle access to work site.
 [Reduce vehicle disturbance of
 unpaved surfaces (access/haul
 roads, staging areas, parking
 areas/lots, etc.).].
Limit vehicle speed at work site.  Yes...............  $2,526-$4,717.
------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Appendix C, Section C.4.3.

    For nonpoint mining and quarrying, ADEQ evaluated three activities: 
earthmoving, including overburden removal and replacement; drilling and 
blasting; and material handling, including loading and unloading. 
Relying on cost estimates derived from industry representatives such as 
the Arizona Rock Products Association and vendor quotes, ADEQ conducted 
a four-factor analysis of available controls, the results of which are 
summarized in Table 17 of this document. Because the controls were 
either not technically feasible or the cost-effectiveness values far 
exceeded ADEQ's $5,000/ton cost threshold ($18,308/ton for additional 
watering and purchasing an additional water truck being the lowest cost 
effectiveness value), ADEQ determined it is not reasonable to require 
additional nonpoint mining and quarrying controls during this planning 
period.

[[Page 47425]]



                          Table 17--Summary of Control Options for Mining and Quarrying
----------------------------------------------------------------------------------------------------------------
                                                                                                      Cost-
             Activity                          Control measure                 Technically      effectiveness ($/
                                                                                feasible?             ton)
----------------------------------------------------------------------------------------------------------------
Earthmoving & Excavating..........  Additional Watering--Purchase         Yes.................           $18,308
                                     Additional Water Truck.
                                    Additional Watering--Rent Additional  Yes.................            24,496
                                     Water Truck.
                                    Implement Additional Watering with    N/A.................  ................
                                     Available Trucks.
                                    Water in Operational Areas--Other     N/A.................  ................
                                     Water Distribution Systems (besides
                                     trucks).
                                    Applying dust suppressants (other     No..................  ................
                                     than water).
                                    Avoid clearing during wind gusts....  N/A.................  ................
Material Handling--Bulk Loading...  Partial Closure with Hanging          Yes.................           101,309
                                     Curtains and the use of Water
                                     Spraying at Primary Dump.
                                    Regularly Apply Water Through         Yes.................           204,319
                                     Wetting of Material at the Pit.
                                    Regularly Apply Water Through Water   N/A.................  ................
                                     Sprays.
                                    Reduce Falling Distance.............  N/A.................  ................
                                    Use of Loading Spouts...............  No..................  ................
                                    Use of Loading Spout Equipped with    No..................  ................
                                     Dust Control System.
                                    Use of Cascading Loading Spouts.....  No..................  ................
                                    Use of Cascading Loading Spouts       No..................  ................
                                     Equipped with Wind Shrouds and
                                     Discharge Skirts.
                                    Use of Conical Loading Hoppers (Dust  No..................  ................
                                     Suppression Hopper).
                                    Use of Dry Fog Dust Suppression       No..................  ................
                                     System at Loading/Unloading Points.
Material Handling--Stockpiles.....  Wetting Product with Plain Water and/ Yes.................           204,319
                                     or Wetting Agents as it is Loaded/
                                     Unloaded Onto Stockpile Through Use
                                     Of New Water Truck.
                                    Continuous Watering with New Water    N/A.................  ................
                                     Truck.
                                    Continuous Watering with Existing     N/A.................  ................
                                     Water Truck.
                                    Wetting Product with Plain Water and/ N/A.................  ................
                                     or Wetting Agents as It Is Loaded/
                                     Unloaded onto Stockpile Through Use
                                     of Spray Bars.
                                    Dry Fog Dust Suppression System       N/A.................  ................
                                     during Material Loading/Unloading
                                     onto Pile.
                                    Reduce Falling Distance.............  N/A.................  ................
Blasting..........................  Utilize Good Design (i.e., Drilling   N/A.................  ................
                                     Fewer Holes).
                                    Temporarily Cease Operations Until    N/A.................  ................
                                     Conditions Improve.
                                    Employ BMPs.........................  N/A.................  ................
                                    Wet Down Blasting Area..............  No..................  ................
                                    Water Cartridges (Underground         No..................  ................
                                     Blasting).
                                    Fogger Spray........................  No..................  ................
                                    Air Filtration System (Underground    No..................  ................
                                     Blasting).
                                    Minimize Area to Be Blasted at Any    N/A.................  ................
                                     One Time.
----------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Appendix C, Section C.4.3.

    For paved road dust, ADEQ indicated that emissions estimates were 
based on re-entrained road dust emissions from paved road surfaces, re-
entrained road dust emissions from unpaved shoulders of paved roads, 
re-entrained road dust emissions from medians of paved roads, re-
entrained road dust emissions and track out from access points where 
unpaved traffic surfaces adjoin paved roads, and re-entrained road dust 
emissions from material spills. ADEQ conducted a four-factor analysis 
of available controls, the results of which are summarized in Table 18 
of this document. Based on these results, ADEQ determined the following 
two control measures to be reasonable: paving access points where 
unpaved traffic surfaces adjoin paved roads and providing for traffic 
rerouting or rapid cleanup of temporary (and not readily preventable) 
sources of dust on paved roads (trackout, spills, water erosion, 
runoff, and skid control sand). Therefore, ADEQ indicated that these 
new measures were considered to be a part of Arizona's long-term 
strategy for the second planning period.\181\ ADEQ rejected other 
evaluated controls because they exceeded ADEQ's $5,000/ton threshold.
---------------------------------------------------------------------------

    \181\ 2022 Arizona Regional Haze Plan, p. 96.

        Table 18--Summary of Control Options for Paved Road Dust
------------------------------------------------------------------------
                                      Technically     Cost-effectiveness
         Control measure               feasible?            ($/ton)
------------------------------------------------------------------------
Pave, cover with aggregate, or     Yes..............              $5,058
 chemically stabilize access
 points where unpaved traffic
 surfaces adjoin paved roads.
 (Aggregate Coverage).
Pave, cover with aggregate, or     Yes..............               2,351
 chemically stabilize access
 points where unpaved traffic
 surfaces adjoin paved roads.
 (Paving).
Pave, cover with aggregate, or     Yes..............                 221
 chemically stabilize access
 points where unpaved traffic
 surfaces adjoin paved roads.
 (Chemical Stabilization).
Require haul trucks to be covered  Yes..............                 N/A
Provide for traffic rerouting or   Yes..............               3,614
 rapid cleanup of temporary (and
 not readily preventable) sources
 of dust on paved roads
 (trackout, spills, water
 erosion, runoff, and skid
 control sand).

[[Page 47426]]

 
Reduced usage of skid control      N/A..............                 N/A
 sand or salt and improved
 material specification (e.g.,
 require use of coarse, non-
 friable material during snow and
 ice season).
Require curbing and pave or        Yes..............               9,434
 stabilize shoulders of paved
 roads. (Asphalt Concrete).
Require curbing and pave or        Yes..............              14,144
 stabilize shoulders of paved
 roads. (Chemical Stabilization).
Stabilize medians of paved roads.  Yes..............               9,434
 (Asphalt Concrete).
Stabilize medians of paved roads.  Yes..............              14,144
 (Chemical Stabilization).
Ensure stabilization during work   Yes..............              31,877
 on unpaved shoulders of paved
 roads (e.g., weed abatement/
 vegetation management).
Provide for storm water drainage   No...............                 N/A
 to prevent water erosion onto
 paved roads.
Employ PM10 certified street       Yes..............               5,164
 sweepers on principal arterials..
Reduce speed limits..............  No...............                 N/A
------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Appendix C, Section C.4.4.

    For unpaved road dust, ADEQ evaluated re-entrained road dust 
emissions from unpaved roads as part of its analysis. ADEQ conducted a 
four-factor analysis of available controls, the results of which are 
summarized in Table 19 of this document. Based on these results, ADEQ 
determined that it is not reasonable to require additional unpaved road 
dust controls during this planning period. Although ADEQ did not 
specify why no other controls were reasonable, cost appears to have 
been the determining factor, as the cost effectiveness of all feasible 
controls exceeded ADEQ's chosen cost-effectiveness threshold of $5,000/
ton.

       Table 19--Summary of Control Options for Unpaved Road Dust
------------------------------------------------------------------------
                                      Technically     Cost-effectiveness
         Control measure               feasible?            ($/ton)
------------------------------------------------------------------------
Develop traffic reduction plans    No...............                 N/A
 for unpaved roads. Use of speed
 bumps, low speed limits, etc.,
 to encourage use of other
 (paved) roads.
Pave unpaved roads (chip-seal)     Yes..............             $19,545
 800 average daily trips (ADT).
Pave unpaved roads (asphalt) 800   Yes..............              26,227
 ADT.
Pave unpaved roads (concrete) 800  Yes..............              33,571
 ADT.
Chemically stabilize unpaved       Yes..............              47,528
 roads (dust suppressants other
 than water). 800 ADT.
Apply and maintain surface         Yes..............             223,420
 gravel. 800 ADT.
Prohibit [limit] construction of   Yes..............              19,545
 new unpaved roads chip seal.
Prohibit [limit] construction of   Yes..............              26,227
 new unpaved roads asphalt.
Prohibit [limit] construction of   Yes..............              33,571
 new unpaved roads concrete.
------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Appendix C, Section C.4.5.

    In the 2023 Arizona Regional Haze Rules Supplement, ADEQ submitted 
``Nonpoint Rules to Supplement Arizona's 2022 Regional Haze SIP.'' ADEQ 
added three new rules to Arizona Administrative Code (A.A.C.) Title 18, 
Chapter 2, Article 13 to incorporate measures intended to reduce 
emissions of fugitive dust from nonpoint sources in and around the 
following Class I areas: Chiricahua National Monument and Wilderness 
Area, Galiuro Wilderness Area, Saguaro National Park, and Superstition 
Wilderness Area. The rules limit emissions from certain dust generating 
activities at nonresidential construction sites and from paved roads to 
implement ADEQ's control determinations for the nonpoint sources. The 
three rules submitted are: A.A.C. R18-2-D1301 (Definitions for R18-2-
D1302 and R18-2-D1303), A.A.C. R18-2-D1302 (Fugitive Dust Emissions 
from Nonresidential Construction), and A.A.C. R18-2-D1303 (Fugitive 
Dust Emissions from Paved Roads). The EPA will act on these three rules 
in a separate rulemaking.
    Arizona is not using the anticipated emissions reductions from the 
nonpoint source emissions reduction measures in the state's 2028 RPG 
calculations and in the estimate of emissions reductions from their 
long-term strategy. ADEQ indicated that while the new emissions 
reduction measures are reasonable on a per event/location basis, the 
agency does not currently have enough information to quantify the total 
number of track out events and access points to which these controls 
would be applicable. ADEQ indicated that it intends to gather 
additional information through the implementation of these measures and 
take emissions reduction credits in future Regional Haze planning 
periods.
c. Summary of Control Determinations
    Arizona's control measure determinations, including the specific 
permit conditions and rules submitted to the EPA for approval into the 
Arizona SIP by incorporation by reference, are summarized in Table 20 
of this proposed rulemaking document. Some emissions controls are 
included in the modeling of 2028 RPGs of Arizona's long-term strategy, 
and ADEQ estimated the emissions reductions to be: 2,122 tpy 
SO2 for SGS 1 & 2, and 499 tpy NOX for Williams 
Compressor Station. ADEQ indicated that the State's calculation of 2028 
RPGs does not include anticipated emissions reductions from IGS Unit 3 
nor the nonpoint sources.

[[Page 47427]]



                                           Table 20--Arizona Regional Haze New Control Measure Determinations
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                  Permit conditions or
                                                                                                                                   rules submitted for
              Source                       Unit                   Control                 Pollutant        Compliance deadline      approval into the
                                                                                                                                       Arizona SIP
--------------------------------------------------------------------------------------------------------------------------------------------------------
Springerville Generating Station.  Units 1 and 2.......  Combined annual SO2 cap    SO2.................  One year after SIP    Arizona Department of
                                   Units 1 and 2.......   for Units 1 & 2 of 3,729  SO2.................   approval.             Environmental Quality
                                                          tpy.                                            One year after SIP     Significant Permit
                                                         Combined 16.1 tons/day                            approval.             Revision No. 91093 to
                                                          SO2 30-day rolling                                                     Operating Permit No.
                                                          average.                                                               65614 Cover Page and
                                                                                                                                 Attachment ``E''
                                                                                                                                 Regional Haze
                                                                                                                                 Provisions: Tucson
                                                                                                                                 Electric Power Plant--
                                                                                                                                 Springerville
                                                                                                                                 Generating Station.
Williams Compressor Station......  RECIP-1.............  Low Emission Combustion    NOX.................  18 months after SIP   Arizona Department of
                                                          (LEC-2) controls.                                approval.             Environmental Quality
                                                                                                                                 Significant Permit
                                                                                                                                 Revision No. 93062 to
                                                                                                                                 Operating Permit No.
                                                                                                                                 77575 Cover Page and
                                                                                                                                 Attachment ``D'':
                                                                                                                                 Regional Haze
                                                                                                                                 Provisions.
                                   RECIP-2.............  Low Emission Combustion    NOX.................  18 months after SIP
                                                          (LEC-3) controls.                                approval.
                                   RECIP-5.............  LEC-3 controls...........  NOX.................  18 months after SIP
                                                                                                           approval.
Irvington Generating Station.....  Unit 3..............  Useful life NOX cap of     NOX.................  One year after SIP    Pima Department of
                                                          1,285 tons.                                      approval.             Environmental Quality
                                                                                                                                 Air Quality Permit No.
                                                                                                                                 1052 Cover Page and
                                                                                                                                 Section VI. Unit EGU-I3
                                                                                                                                 Regional Haze State
                                                                                                                                 Implementation Plan.
                                                         Rolling 3-year average     NOX.................  One year after SIP
                                                          NOX cap of 251 tpy.                              approval.
                                                         Single year annual NOX     NOX.................  One year after SIP
                                                          cap of 392 tpy.                                  approval.
Industrial, Commercial, and        N/A.................  (1) Paving unpaved         PM10................  January 1, 2025.....  A.A.C. R18-2-D1301
 Institutional Construction.                              parking and staging                                                    (Definitions for R18-2-
                                                          areas, (2) applying                                                    D1302 and R18-2-D1303)
                                                          acrylic polymer to                                                     and A.A.C. R18-2-D1302
                                                          unpaved parking and                                                    (Fugitive Dust
                                                          staging areas, (3)                                                     Emissions from
                                                          applying gravel to                                                     Nonresidential
                                                          unpaved parking and                                                    Construction).
                                                          staging areas, and (4)
                                                          limiting vehicle speed
                                                          at work site to 15 mph
                                                          with signage.
Paved Roads......................  N/A.................  (1) Paving access points   PM10................  September 10, 2023..  A.A.C. R18-2-D1301
                                                          where unpaved traffic                                                  (Definitions for R18-2-
                                                          surfaces adjoin paved                                                  D1302 and R18-2-D1303)
                                                          roads; (2) Providing for                                               and A.A.C. R18-2-D1303
                                                          traffic rerouting or                                                   (Fugitive Dust
                                                          rapid cleanup of                                                       Emissions from Paved
                                                          temporary (and not                                                     Roads).
                                                          readily preventable)
                                                          sources of dust on paved
                                                          roads (trackout, spills,
                                                          water erosion, runoff,
                                                          and skid control sand).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan and 2023 Arizona Regional Haze Rules Supplement.
Note: ADEQ is not claiming emissions reduction credit in calculating RPGs for IGS or for the nonpoint sources. ADEQ stated that it intends to claim
  emissions reduction credit stemming from the enactment of the nonpoint emissions reduction measures in future Regional Haze planning periods.

d. Additional Long-Term Strategy Requirements
    Arizona indicates in its submittal that the State consulted with 
other WRAP states in development of this SIP.\182\ The majority of 
state consultation in the development of the regional haze SIPs was 
conducted through the WRAP's Regional Haze Planning group, as Arizona 
participated in regular calls with WRAP states.
---------------------------------------------------------------------------

    \182\ 2022 Arizona Regional Haze Plan, Chapters 2.3 and 2.6.
---------------------------------------------------------------------------

    Arizona also had individual consultations with California, Utah, 
Nevada, Colorado, and New Mexico regarding source screening, approaches 
to four factor analyses, and general SIP preparation. ADEQ indicated 
that these states were selected by Arizona for consultation in 
anticipation that they may contribute to visibility impairment in the 
State's mandatory Class I Federal areas given their proximity to the 
Arizona border. No other states approached Arizona for regional haze 
consultation during this planning period. Pursuant to 40 CFR 
51.308(f)(2)(ii)(A), ADEQ and the above agencies did not agree on any 
measures during their state-to-state consultations. Pursuant to 40 CFR 
51.308(f)(2)(ii)(B), the agencies confirmed that they shared the 
measures they have identified as being necessary to make reasonable 
progress in a mandatory Class I Federal area with ADEQ, and that the 
Agencies have not requested for ADEQ to consider any measures necessary 
to make reasonable progress in any mandatory Class I Federal areas. 
Pursuant to 40 CFR 51.308(f)(2)(ii)(C), ADEQ indicates that there are 
currently no disagreements between ADEQ and other state agencies on 
Arizona's emissions reduction measures. ADEQ also documented outreach 
efforts with the New Mexico Environmental Department but indicated that 
no feedback was received from New Mexico.
    In its submittal, Arizona also commits to continue consultation 
with California, Nevada, Utah, Colorado, New Mexico, and any other 
state which may reasonably be anticipated to cause or contribute to 
visibility impairment in Class I Federal areas located within 
Arizona.\183\ As part of this commitment, Arizona will also continue 
consultation with any state for which Arizona's emissions may 
reasonably be anticipated to cause or contribute to visibility 
impairment in those states' Class I areas. With regard to the 
established or updated goal for reasonable progress, should 
disagreement arise between another state or group of states, Arizona 
indicated that it will describe the actions taken to resolve the 
disagreement in future regional haze SIP revision. With regard to 
assessing or updating long-term strategies, Arizona also committed to 
coordinate its emissions management strategies with affected states and 
to continue to include in its future regional haze SIP revisions all 
measures agreed to during state-to-state consultations or a regional

[[Page 47428]]

planning process, or measures that will provide equivalent visibility 
improvement.\184\
---------------------------------------------------------------------------

    \183\ 2022 Arizona Regional Haze Plan, Chapter 2.6.3.
    \184\ Id.
---------------------------------------------------------------------------

2. The EPA's Evaluation of Arizona's Long-Term Strategy
    The EPA is proposing to find that, due to flaws in some of its 
analyses and conclusions, Arizona has not fully satisfied the long-term 
strategy requirements of section 51.308(f)(2). In the following 
sections we summarize the most significant shortcomings in Arizona's 
source selection process, four-factor analyses, and control 
determinations, which form the basis for this proposed finding.
a. Source Selection
    The EPA finds that many aspects of ADEQ's source selection process, 
such as its focus on sulfate, nitrate, and coarse mass and its use of a 
Q/d value of 10 for point sources, were reasonable and adequately 
explained and documented. However, ADEQ did not provide an adequate 
justification for screening out certain sources and units from 
conducting a four-factor analysis on the basis that they are 
``effectively controlled'' as part of its source selection 
process.\185\ Specifically, in some cases, ADEQ did not identify the 
controls for each pollutant at each unit or process, the associated 
limits, or where the controls/limits currently exist in the Arizona 
SIP. In other cases, ADEQ listed the controls, but did not clearly 
explain why it is reasonable to assume, without conducting a four-
factor analysis, that no additional controls would be reasonable.\186\ 
For example, ADEQ cites better-than-BART determinations from the first 
planning period for Apache Generating Station Units 2 and 3 and IGS 
Unit 4 as a rationale that it is not necessary to conduct a four factor 
analysis.\187\ However, despite ADEQ providing some of the limits 
associated with these determinations, the mere fact that a unit 
installed BART (or better-than-BART) controls in the first planning 
period is not a sufficient justification on its own that no new 
controls are necessary for reasonable progress in the second planning 
period.\188\ Indeed, the evaluation and control of BART sources under 
the reasonable progress requirements in the second planning period may 
be necessary to achieve the national goal of the prevention of any 
future, and the remedying of any existing, manmade impairment of 
visibility in Class I areas.\189\ Accordingly, ADEQ should have 
identified where the existing limits are found in the SIP or FIP and 
clearly explained why no additional controls would likely be reasonable 
under a four-factor reasonable progress analysis for the second 
planning period. Therefore, ADEQ also did not adequately explain 
whether these facilities' existing controls were necessary for 
reasonable progress and therefore a part of the state's long-term 
strategy.\190\
---------------------------------------------------------------------------

    \185\ See 40 CFR 51.308(f)(2)(i) (``. . . The State must include 
in its implementation plan a description of the criteria is used to 
determine which sources or groups of sources it evaluated and how 
the four factors were taken into consideration in selecting the 
measures for inclusion in its long-term strategy'').
    \186\ Id., see also 2021 Clarifications Memo, p. 5, 2019 
Guidance, p. 23.
    \187\ 2022 Arizona Regional Haze Plan, pp. 109 and 114.
    \188\ See 40 CFR 51.308(e)(5) (``After a State has met the 
requirements for BART or implemented an emissions trading program or 
other alternative measure that achieves more reasonable progress 
than the installation and operation of BART, BART-eligible sources 
will be subject to the requirements of [40 CFR 51.308(d) and (f)], 
as applicable, in the same manner as other sources.'').
    \189\ See 2019 Guidance, p. 25 (``[S]tates may not categorically 
exclude all BART-eligible sources, or all sources that installed 
BART controls, as candidates for analysis of control measures.'').
    \190\ 40 CFR 51.308(f)(2) (``Each State must submit a long-term 
strategy that addresses regional haze visibility impairment . . . 
the long-term strategy must include the enforceable emissions 
limitations . . . that are necessary to make reasonable 
progress.''); see also 2021 Clarifications Memo, pp. 8-9.
---------------------------------------------------------------------------

b. Four-Factor Analyses
    The EPA finds that many of ADEQ's four-factor analyses included 
flaws in the cost analyses, which in some instances, significantly 
affected the resulting cost effectiveness values that ADEQ used to 
determine what measures are necessary to make reasonable progress. 
These flaws are detailed in the following sections.
i. Controlled Emission Rates
    The emission rates used in some of Arizona's four-factor analyses 
did not appropriately reflect the emissions rate achievable with the 
relevant controls. For example, in the NOX four-factor 
analysis for SGS Units 1 and 2, ADEQ determined that the emission rates 
of 0.060 lb/MMBtu and 0.15 lb/MMBtu provide a reasonable estimate of 
the achievable rates for SCR and SNCR, respectively. ADEQ noted 
considerations related to more frequent startup/shutdown cycles 
occurrences at SGS and higher baseline NOX emissions 
compared to other similar units, as reasons for using these emissions 
rates.
    SCR has been demonstrated to achieve 0.05 lb/MMBtu (or up to 90 
percent reduction) a retrofit basis,\191\ and achieving this emission 
rate at Units 1 and 2 instead of 0.06 lb/MMBtu would result in 
approximately 150 tpy of additional NOX reductions per unit 
(based upon 2028 emissions provided in Table 5 of this document). We 
acknowledge that the startup/shutdown considerations noted by ADEQ are 
relevant, particularly for establishing emissions limits on a short-
term averaging period (such as 24-hour average or rolling 30-day), 
where startup and shutdown emissions can represent a larger portion of 
a unit total emission rate. However, ADEQ has not demonstrated why 
these startup/shutdown considerations would be significant enough at 
SGS Units 1 and 2 on an annual average basis, which is the averaging 
period used to calculate ton/year emissions reductions for cost 
effectiveness calculations, to preclude them from achieving this 
emissions reduction level with SCR. Similarly, while these factors 
could also be relevant to SNCR performance, it has not been 
demonstrated why they would cause SNCR on these units to achieve as 
little as a 15 percent reduction. Use of lower emissions rates that 
more accurately reflect the rates achievable with the associated 
control technologies on an annual basis would have resulted in greater 
emissions reductions and thus lower cost per ton values associated with 
these control options. The State's failure to analyze such lower limits 
in their four-factor analyses, combined with other flaws discussed in 
Section IV.E.2.b.ii of this document, render the State's analyses 
insufficient to support reasoned control determinations.
---------------------------------------------------------------------------

    \191\ Ravi K. Srivastava, Robert E. Hall, Sikander Khan, Kevin 
Culligan & Bruce W. Lani (2005) Nitrogen Oxides Emission Control 
Options for Coal-Fired Electric Utility Boilers, Journal of the Air 
& Waste Management Association, 55:9, 1367-1388, DOI: 10.1080/
10473289.2005.10464736. Available at: https://www.tandfonline.com/action/showCitFormats?doi=10.1080/10473289.2005.10464736.
---------------------------------------------------------------------------

ii. Deviations From Control Cost Manual
    When developing a long-term strategy for making reasonable 
progress, states must consider the four statutory factors.\192\ In 
considering these factors, including the costs of compliance and the 
remaining useful life of affected sources, it is important to use 
consistent methods in order to allow for comparisons between different 
sources within a state, and cost analyses in other states. Therefore, 
as part of any four-factor analysis, the EPA has recommended that costs 
of compliance should be calculated consistent with the

[[Page 47429]]

methods set forth in the EPA's Control Cost Manual.\193\ As we have 
previously noted in relation to BART determinations, ``[w]ithout an 
`apples-to-apples' comparison of costs, it is impossible to draw 
rational conclusions about the reasonableness of the costs of 
compliance for particular control options. Use of the [Control Cost 
Manual] methodology is intended to allow a fair comparison of pollution 
control costs between similar applications for regulatory purposes.'' 
\194\ The same principle applies to the evaluation of the cost of 
compliance as part of a four-factor analysis.\195\ Therefore, where a 
state deviates from these methods, it should explain how its 
alternative approach is appropriate and consistent with the regulations 
and the statutory requirement to make reasonable progress towards the 
national goal. Arizona did not do so.
---------------------------------------------------------------------------

    \192\ See CAA 169A(b)(2)(B), CAA 169A(g)(7), and 40 CFR 
51.308(f)(2)(i).
    \193\ 2019 Guidance, p. 31.
    \194\ 77 FR 72512, 72518. See also Arizona ex rel. Darwin v. 
EPA, 815 F.3d 519, 540 (9th Cir. 2016); (upholding this 
interpretation as reasonable).
    \195\ 2019 Guidance, p. 31.
---------------------------------------------------------------------------

    One important element of a cost-effectiveness analysis is the 
remaining useful life of the equipment. The equipment life used to 
calculate costs for each control technology option, unless constrained 
by an enforceable retirement date for the source contained in the SIP, 
should be consistent with that found in the respective chapter of the 
Control Cost Manual. Any deviations from the Control Cost Manual should 
be documented and an appropriate rationale provided.\196\ ADEQ did not 
provide appropriate documentation of the remaining useful life (i.e., 
the control equipment life) used to calculate the costs of controls for 
some of the facilities it analyzed. For example, in its analysis for 
EPNG Williams TURBINE-1, ADEQ assumed a useful life of 25 years for 
NOX controls, including for SCR, based on the expected life 
of the turbine. However, an enforceable shutdown date is not associated 
with the turbine, and in situations where an enforceable shutdown date 
does not exist, the remaining useful life of a control under 
consideration should be the full period of the useful life of that 
control as recommended by the EPA's Control Cost Manual.\197\ 
Similarly, in its analysis for the compressor engines at EPNG Williams, 
ADEQ amortized SCR and other control options over a 20-year period. 
This assumption is not supported with any additional information in 
either ADEQ's TSD or in the original source document from EPNG.
---------------------------------------------------------------------------

    \196\ Id. at pp. 33-34. See also 40 CFR 51.308(f)(2)(iii) (``The 
State must document the technical basis, including modeling, 
monitoring, cost, engineering, and emissions information, on which 
the State is relying to determine the emission reduction measures 
that are necessary to make reasonable progress in each mandatory 
Class I Federal area it affects'').
    \197\ Id.
---------------------------------------------------------------------------

    Another important element of the cost effectiveness analysis is the 
interest rate used. In its cost calculations for EPNG Willcox and 
Williams, ADEQ used an interest rate of 8.53 percent (for most control 
options such as SCR) and 9 percent for water/steam injection. These 
values were well above the bank prime interest rates at the time these 
analyses were developed, and above the source-specific interest rates 
used in other facilities' analyses. While the TSD notes that 8.53 
percent is based upon site specific information provided by EPNG, that 
information is not in the TSD or the original source document from 
EPNG. Additional documentation is needed to support the use of the 8.53 
percent and 9 percent interest rates in cost calculations.\198\
---------------------------------------------------------------------------

    \198\ Control Cost Manual, Chapter 2, p. 15. See also 40 CFR 
51.308(f)(2)(iii) (``The State must document the technical basis, 
including modeling, monitoring, cost, engineering, and emissions 
information, on which the State is relying to determine the emission 
reduction measures that are necessary to make reasonable progress in 
each mandatory Class I Federal area it affects'').
---------------------------------------------------------------------------

    In the absence of adequate documentation supporting deviations from 
the Control Cost Manual, we find that ADEQ's cost analyses are not 
sufficiently reliable to support its control determinations.
c. Control Determinations
    In addition to the issues with source selection and four-factor 
analyses noted in the previous sections, we find that ADEQ did not 
reasonably weigh the statutory factors in reaching its control 
determinations for certain sources, as detailed in the following 
paragraphs. In addition, where ADEQ determined that no additional 
measures were necessary to make reasonable progress for a particular 
source, it did not determine whether the source's existing measures are 
necessary to make reasonable progress and therefore, whether they 
should be a part of its long-term strategy.
i. Application of Cost Thresholds
    As described in Sections IV.E.1.a.ii and IV.E.1.b of this document, 
ADEQ set an average cost-effectiveness threshold of $6,500/ton for 
point sources. Generally, ADEQ did not provide an adequate 
justification for how this threshold resulted in a reasonable set of 
control measures.\199\ In a few instances, ADEQ rejected controls for 
which the average cost effectiveness was below this chosen threshold 
based on incremental cost effectiveness (i.e., the cost-effectiveness 
of a more expensive control compared to a less expensive control). 
Specifically, ADEQ rejected wet FGD on SGS 1 and 2, and LEC-3 on 
Williams RECIP-1, on the grounds that the incremental costs of these 
controls, relative to less stringent controls, were excessive. Although 
states may choose to consider incremental costs in a reasonable 
manner,\200\ we find it was unreasonable for ADEQ to do so only for 
specific units and only as a reason to reject controls that otherwise 
met the state's chosen cost-effectiveness threshold. In addition, while 
ADEQ conducted an analysis of numerous first planning period control 
determinations to set its threshold of $6,500/ton, it considered only a 
single BART determination to determine that incremental costs of 
$11,120/ton (for LEC-3 on Williams Units RECIP-1), and $9,400-13,500/
ton (for wet WGD on SGS 1 and 2) were excessive.\201\ We find that the 
use of incremental cost in this way, without adequate support or 
consistent application, is not reasonable.
---------------------------------------------------------------------------

    \199\ ``As the Ninth Circuit explained in NPCA v. EPA, 788 F.3d 
at 1142, the Regional Haze Rule does not prevent states from 
implementing `bright line' rules, such as thresholds, when 
considering costs and visibility benefits. However, the state must 
explain the basis for any thresholds or other rules (see 40 CFR 
51.308(f)(2)).'' 2019 Guidance, p. 38.
    \200\ Id. p. 40.
    \201\ 2022 Arizona Regional Haze Plan, Appendix C, pp. 121 and 
229.
---------------------------------------------------------------------------

    In addition, we note that several controls were rejected by ADEQ on 
the grounds that they were marginally above the chosen cost threshold 
($6,500/ton for point sources and $5,000/ton for nonpoint sources). For 
example, the cost effectiveness for water injection at Williams 
TURBINE-1 was close to ADEQ's cost effectiveness threshold of $6,500/
ton, with a difference of $36. The cost effectiveness threshold for 
SNCR on SGS Unit 2 was also marginally above the $6,500/ton threshold, 
with a $269 difference. Additionally, a few nonpoint source controls 
were also marginally above ADEQ's $5,000/ton threshold but rejected 
based on cost, such as a dust control plan ($76 difference) and 
sweeping ($164 difference) for ICI construction and sweeping ($164 
difference) for paved road dust. Given the flaws in the cost-
effectiveness analyses noted in Section IV.E.2.b, which may have 
resulted in inflated cost-effectiveness values, we

[[Page 47430]]

recommend that ADEQ revisit these control determinations in particular.
ii. Use of Visibility as a Factor To Avoid Controls
    The EPA has explained that states choosing to consider visibility 
benefits as an optional additional factor should not use visibility to 
summarily dismiss cost-effective potential controls, and that a state 
that has identified cost-effective controls but rejects most or all of 
them based on visibility benefits is likely to be improperly using 
visibility as an additional factor.\202\ Arizona has not considered 
visibility benefits for most of its sources, but appears to have 
considered visibility modeling submitted by TEP for SGS. In the SGS 
analysis, ADEQ stated that ``[a]ny controls having an average cost-
effectiveness of 6,500 $/ton are cost excessive unless there [is] 
compelling evidence that the controls would result in a significant 
visibility improvement at Class I areas.'' \203\ In addition, ADEQ 
pointed to ``small visibility benefits'' associated with the modeled 
NOX and SO2 controls to support its 
determinations that no new NOX controls and a less stringent 
SO2 control (SDA upgrades) are necessary to make reasonable 
progress with respect to SGS Units 1 and 2.\204\ However, ADEQ has not 
defined what it considers to be a significant visibility improvement or 
how its analysis comports with the regional haze regulations.
---------------------------------------------------------------------------

    \202\ 2021 Clarifications Memo, p. 13.
    \203\ 2022 Arizona Regional Haze Plan, Appendix C, p. 216.
    \204\ Id. at 234.
---------------------------------------------------------------------------

    Whether a particular visibility impact is meaningful should be 
assessed in context and cannot be used to undermine the four statutory 
factors that are to be analyzed in order to determine what measures are 
necessary for reasonable progress.\205\ As many of the largest 
individual visibility impairing sources have either already been 
controlled (under the RHR or other CAA or state programs) or have 
retired, the remaining individual sources are often smaller and better 
controlled, with each source making relatively smaller contributions to 
a Class I area as a proportion of total impairment. This does not mean, 
however, that additional emissions reductions are not needed in the 
second planning period and beyond, and the remaining sources need not 
be analyzed for additional controls. To the contrary, the evaluation 
and control of such smaller sources may be necessary to achieve the 
national goal of the prevention of any future, and the remedying of any 
existing, anthropogenic impairment of visibility in Class I areas.
---------------------------------------------------------------------------

    \205\ 40 CFR 51.308(f)(2)(i); 2021 Clarifications Memo, p. 14.
---------------------------------------------------------------------------

    With a Q of 17,044 and a Q/d of 339, SGS is by far the largest 
emissions source analyzed by ADEQ in the 2022 Arizona Regional Haze 
Plan. ADEQ found that Units 3 and 4, as well as Units 1 and 2 for 
PM10, were effectively controlled, leaving only 
NOX and SO2 at Units 1 and 2 as providing an 
opportunity for further control. In the absence of any opportunities 
for larger emissions reductions and corresponding visibility benefits, 
we find that ADEQ's reliance on ``small'' visibility benefits as an 
additional justification for not adopting more stringent controls at 
these units is not persuasive.
    We also have concerns with certain aspects of the modeling for SGS. 
In particular, the analysis considered visibility benefits from a 
NOX control on Units 1 and 2 with an emission factor of 0.08 
lb/MMBtu, roughly half that resulting from SNCR (0.15 lb/MMBtu) and 25 
percent higher than that resulting from SCR (0.06 lb/MMBtu). In 
addition, the analyses focused on the average over the 20 percent most 
impaired days and concluded the visibility benefits from installing SCR 
were small. While it is reasonable to consider visibility impacts on 
the most impaired days, due to variability in daily transport patterns, 
the EPA's guidance recommends that for individual sources, the maximum 
daily visibility impact on all days may be a more meaningful 
metric.\206\
---------------------------------------------------------------------------

    \206\ 2019 Guidance, pp. 15-16.
---------------------------------------------------------------------------

    In sum, we find that ADEQ's consideration of visibility benefits of 
potential controls at SGS Units 1 and 2 did not provide meaningful 
support of its rejection of more stringent NOX and 
SO2 controls at these two units.
iii. Mass-Based Emissions Caps at SGS
    For SGS Units 1 and 2, ADEQ determined that ``emission reductions 
equivalent to SDA upgrades at Unit 1 and Unit 2 are necessary to make 
reasonable progress'' and established two combined emissions limits for 
Unit 1 and Unit 2: 3,729 tons per year on 12-month rolling average; and 
16.1 tons per day (tpd) on a 30-calendar-day rolling average. ADEQ 
stated that ``establishing the two capped emission limits within the 
two emission units can provide compliance flexibility yet still 
guarantee that each unit is well controlled to protect and improve the 
visibility in Class I areas.'' \207\ For the reasons that follow, the 
EPA proposes to find that these limits will not ensure implementation 
of the emissions reduction measures that are necessary to make 
reasonable progress at these units.
---------------------------------------------------------------------------

    \207\ 2022 Arizona Regional Haze Plan, Appendix C, p. 239.
---------------------------------------------------------------------------

    First, as noted in the preceding section, ADEQ rejected wet FGD for 
SGS 1 and 2 in part due to incremental cost effectiveness compared to 
SDA.\208\ However, as ADEQ acknowledged in the SIP submittal, the 
proposed emissions caps will not, in fact, require TEP to upgrade the 
SDA controls at these units. Instead, ``TEP will be very likely to 
manage its operating level strategically instead of completing the 
upgrades to the SDA systems for meeting the RP requirements.'' \209\ 
Given that TEP will not be required to implement SDA upgrades, we find 
it was not reasonable to reject wet FGD on the basis of incremental 
cost relative to SDA.
---------------------------------------------------------------------------

    \208\ Id. at p. 229.
    \209\ Id. at p. 236.
---------------------------------------------------------------------------

    Second, the cost of SDA upgrades was well below ADEQ's established 
cost threshold of $6,500/ton, ranging from $828-$883/ton for SGS Unit 1 
and $853-$908/ton for SGS Unit 2. Therefore, even if TEP meets the 
proposed annual and 30-day limits, it appears that SDA upgrades would 
still be cost-effective, based on ADEQ's established cost threshold.
    Third, because the limits are set across two units and the tpd 
limit is set on a 30-calendar-day basis (rather than a 30-day-boiler-
operating day),\210\ they would not meaningfully constrain the 
emissions from one unit during periods when the other unit is not 
operating. In particular, the annual SO2 cap of 3,739 tpy is 
significantly higher than ADEQ's projected 2028 SO2 
emissions for either Unit 1 or Unit 2 (2,869 and 2,982 tpy, 
respectively) and nearly double each unit's recent emissions (1,980 and 
1,988 tpy respectively on average 2021-2023).\211\ Similarly, the daily 
SO2 cap of 16.1 tpd is greater than half of the maximum 
combined 30-calendar-day emissions of both Unit 1 and Unit 2 over the 
baseline period of 2016-2019.\212\ As noted by ADEQ in their submission 
and confirmed in TEP's most recent Integrated Resources Plan, TEP 
intends to retire Unit 1 in 2027.\213\ If this occurs,

[[Page 47431]]

Unit 2 would be able to emit 3,739 tpy SO2 in 2028, nearly 
double what it emitted on average in 2021-2023 and significantly more 
than the 2,982 tpy it is projected to emit in the absence of a cap. In 
contrast, a lb/MMbtu limit representing SDA set on each unit would 
ensure emissions from Unit 2 would be reduced by approximately \1/3\ 
from recent emissions levels even if Unit 1 ceases operation.
---------------------------------------------------------------------------

    \210\ A limit based on boiler operating days would effectively 
exclude days with zero emissions from the calculation of the 30-day 
average whereas a limit based on calendar days does not.
    \211\ Emissions information can be publicly accessed through the 
EPA Clean Air Markets Program data, available at https://campd.epa.gov/.
    \212\ 2022 Arizona Regional Haze Plan, Appendix C, Figure 5: 
Comparison 30-CD Rolling Average Emission Rates over Baseline Years 
against Emission Limit. ADEQ did not provide separate daily 
emissions data for Units 1 and 2.
    \213\ As part of its preferred alternative in its 2023 
Integrated Resources Plan, p. 56, TEP states that ``Initially, the 
units will alternate idling between spring and fall (both seasons 
include the adjacent winter months). TEP plans to transition Unit 1 
to summer-only operations prior to full retirement at the end of 
2027.''
---------------------------------------------------------------------------

    By comparison, the NOX emission limits ADEQ proposed for 
IGS Unit 3 are also mass-based limits and share some similar elements 
with the proposed SGS Unit 1 and 2 limits. We note that the IGS Unit 3 
NOX limits differ primarily because the proposed limits are 
not relied upon to implement the control determination of a four-factor 
analysis. Rather, the IGS Unit 3 limits, which consist of a combination 
of limitations on unit capacity and total lifetime emissions, are 
subsequently reflected in the unit's four-factor analysis and have the 
effect of increasing the cost effectiveness of additional controls into 
a cost per ton range that ADEQ considered to be not cost effective. 
However, we also note that as currently established in the permit 
revision submitted by ADEQ, the IGS Unit 3 limits would become 
effective only upon approval of ADEQ's regional haze reasonable 
progress determination for IGS by the EPA. Because these limits are not 
yet enforceable, we find that they are not an appropriate basis for 
modifying the baseline control scenario for a four-factor 
analysis.\214\
---------------------------------------------------------------------------

    \214\ See 40 CFR 51.231(b) (SIP must show the State has the 
authority to carry out the SIP at the time of submittal); 2019 
Guidance, p. 29 (``[e]nforceable requirements are one reasonable 
basis for projecting a change in operating parameters and thus 
emissions'').
---------------------------------------------------------------------------

    Finally, we note that ADEQ's proposed determination is that 
``emission reductions equivalent to SDA upgrades at SGS Unit 1 and Unit 
2 are necessary to make reasonable progress,'' \215\ rather than that 
the SDA upgrades themselves are necessary to make reasonable progress. 
This conclusion is not supported by the four-factor analysis, which 
examines specific control measures (including SDA upgrades), rather 
than total emissions reductions levels and, which concludes ``it is 
reasonable to require TEP to upgrade the current SDA systems to further 
reduce the SO\2\ emissions at Unit 1 and Unit 2.'' \216\ In particular, 
as noted above, ADEQ rejected the use of a more stringent control (wet 
FGD), based on incremental costs compared to the cost of actual SDA 
upgrades, not emission reductions ``equivalent'' to such upgrades.
---------------------------------------------------------------------------

    \215\ 2022 Arizona Regional Haze Plan, p. 236.
    \216\ Id. at 232.
---------------------------------------------------------------------------

    For all of these reasons, we propose to find that the 
SO2 emissions caps adopted for SGS Units 1 and 2 will not 
ensure implementation of the emissions reduction measures that are 
necessary to make reasonable progress at these units.
iv. Analysis of Existing Measures Necessary for Reasonable Progress
    As described in Section III.C of this document, where a state 
determines that no additional measures are necessary to make reasonable 
progress for a particular source, the state must then determine whether 
the source's existing measures are necessary to make reasonable 
progress. Generally, a source's existing measures are needed to prevent 
future emissions increases and are thus needed to make reasonable 
progress. If the existing controls at a selected source are necessary 
to make reasonable progress, the state must adopt emissions limits 
based on those controls as part of its long-term strategy for the 
second planning period and include those limits in its SIP (to the 
extent they do not already exist in the SIP).
    ADEQ has not addressed whether any of the existing measures relied 
upon in its four-factor analyses or its ``effective controls'' 
determinations are necessary to make reasonable progress and thus 
should be a part of the State's long-term strategy for the second 
planning period. For example, for SGS Units 3 and 4, ADEQ determined 
that no new measures were necessary to make reasonable progress for any 
pollutant. Similarly, ADEQ found that no additional controls were 
necessary for NOX or PM10 at SGS Units 1 and 2. 
However, ADEQ did not evaluate nor determine whether any of the 
existing measures for these units and pollutants were necessary to make 
reasonable progress and therefore should be a part of its long-term 
strategy. The same is true for the many other emissions processes for 
which ADEQ determined that no new measures were necessary to make 
reasonable progress. Additionally, in general, an emissions limit 
reflecting a source's existing measures that are necessary to make 
reasonable progress should be in the form of the emissions rate 
achieved when implementing those measures (e.g., pounds per million 
British thermal units or lbs/MMBtu, pounds per hour or lbs/hr, or 
pounds per ton or lbs/ton of produced material) and should correspond 
to the emissions rate that was determined to be necessary to make 
reasonable progress.\217\ It is therefore unclear what measures the 
State is relying on to make reasonable progress, and which are a part 
of its long-term strategy for the second planning period.
---------------------------------------------------------------------------

    \217\ See Clarifications Memo, p. 11.
---------------------------------------------------------------------------

    As part of its analysis of whether existing effective measures are 
necessary to make reasonable progress, the State should have considered 
whether the relevant sources are subject to enforceable emissions 
limits that ensure their emissions rates will not increase.\218\
---------------------------------------------------------------------------

    \218\ See Section III.C of this document.
---------------------------------------------------------------------------

e. Conclusions
    As explained in the preceding sections, due to flaws and omissions 
in its source selection and four-factor analyses and the resulting 
control determinations, the EPA proposes to find that Arizona failed to 
reasonably ``evaluate and determine the emission reduction measures 
that are necessary to make reasonable progress'' by considering the 
four statutory factors as required by 40 CFR 51.308(f)(2)(i) and CAA 
section 169A(g)(1). We also propose to find that Arizona failed to 
adequately document the technical basis that it relied upon to 
determine these emissions reduction measures, as required by 40 CFR 
51.308(f)(2)(iii). In so doing, Arizona failed to submit to the EPA a 
long-term strategy that includes ``the enforceable emissions 
limitations, compliance schedules, and other measures that are 
necessary to make reasonable progress'' as required by 40 CFR 
51.308(f)(2).\219\
---------------------------------------------------------------------------

    \219\ See also CAA 169A(b)(2), 169(b)(2)(B) (the CAA requires 
that each implementation plan for a State in which the emissions 
from may reasonably be anticipated to cause or contribute to 
visibility impairment in a Class I area ``contain such emision 
limits, schedules of compliance and other measures as may be 
necessary to make reasonable progress toward meeting the national 
goal, . . . including . . . a long-term . . . strategy for making 
reasonable progress[.]''
---------------------------------------------------------------------------

    Consequently, the EPA is proposing to find that the 2022 Arizona 
Regional Haze Plan does not satisfy the requirements of 40 CFR 
51.308(f)(2). Therefore, we are proposing to disapprove Chapters 2, 
6.1-6.3, 8, and 9 and Appendices B, C, E, F, G, and H of the 2022 
Arizona Regional Haze Plan.

F. Reasonable Progress Goals

    Section 51.308(f)(3) contains the requirements pertaining to RPGs 
for each Class I area. Because Arizona is host to Class I areas, it is 
subject to

[[Page 47432]]

section 51.308(f)(3)(i) and potentially subject to 51.308(f)(3)(ii). 
Section 51.308(f)(3)(i) requires a state in which a Class I area is 
located to establish RPGs--one each for the most impaired and clearest 
days--reflecting the visibility conditions that will be achieved at the 
end of the implementation period as a result of the emissions 
limitations, compliance schedules, and other measures required under 
paragraph (f)(2) to be in states' long-term strategies, as well as 
implementation of other CAA requirements. The long-term strategies as 
reflected by the RPGs must provide for an improvement in visibility on 
the most impaired days relative to the baseline period and ensure no 
degradation on the clearest days relative to the baseline period. 
Section 51.308(f)(3)(ii) applies in circumstances in which a Class I 
area's RPGs for the most impaired days represents a slower rate of 
visibility improvement than the uniform rate of progress calculated 
under 40 CFR 51.308(f)(1)(vi). Under section 51.308(f)(3)(ii)(A), if 
the state in which a mandatory Class I area is located establishes an 
RPG for the most impaired days that provides for a slower rate of 
visibility improvement than the URP, the state must demonstrate that 
there are no additional emissions reduction measures for anthropogenic 
sources or groups of sources in the state that would be reasonable to 
include in its long-term strategy. Section 51.308(f)(3)(ii)(B) requires 
that if a state contains sources that are reasonably anticipated to 
contribute to visibility impairment in a Class I area in another state, 
and the RPG for the most impaired days in that Class I area is above 
the URP, the upwind state must provide the same demonstration.
    Independent of the URP endpoint adjustments, WRAP used three 
different visibility projection methods to estimate visibility 
conditions in 2028 (EPA, EPAwoF, and ModMID) for initial calculation of 
RPGs. These represent, respectively, the standard approach recommended 
in EPA photochemical modeling guidance,\220\ the same approach except 
without fire (``woF'') emissions, and a further variant in which the 
model is used to select the most impaired days (``Mod'', ``MID''), 
rather than selecting them using baseline monitoring data. The approach 
ultimately relied upon by ADEQ was EPAwoF. Excluding fire emissions 
from the model runs used to calculate the relative change in 
concentrations between 2014 and 2028 has the effect of focusing the 
projection on the changes in anthropogenic emissions over the period. 
(Including fire emissions would make the impairment projection less 
responsive to changes in anthropogenic emissions.) While this is not 
the standard procedure, it is consistent with the use of anthropogenic 
impairment from IMPROVE monitor data. These 2028 estimates are 
described in Appendix D of the 2022 Arizona Regional Haze Plan and are 
calculated following ``Procedures for Making Visibility Projections and 
Adjusting Glidepaths using the WRAP-WAQS 2014 Modeling Platform'' \221\ 
to post-process model results from the 2028OTBa2 projections scenario.
---------------------------------------------------------------------------

    \220\ Modeling Guidance for Demonstrating Air Quality Goals for 
Ozone, PM2.5, and Regional Haze, EPA 454/R-18-009, EPA 
OAQPS, November 2018, available at https://www.epa.gov/scram/state-implementation-plan-sip-attainment-demonstration-guidance.
    \221\ ``Procedures for Making Visibility Projections and 
Adjusting Glidepaths using the WRAP-WAQS 2014 Modeling Platform,'' 
Ramboll, March 1, 2021, final draft, available at the WRAP Regional 
Technical Operations Work Group website, https://www.wrapair2.org/RTOWG.aspx; direct link: https://www.wrapair2.org/pdf/2028_Vis_Proj_Glidepath_Adj_2021-03-01draft_final.pdf.
---------------------------------------------------------------------------

    ADEQ's RPGs for its Class I areas (shown by the IMPROVE monitor), 
as compared with baseline conditions and the 2028 Adjusted URP (for the 
most-impaired days) are set out in Tables 10-1 and 10-2 of the 2022 
Arizona Regional Haze Plan and shown in Table 21 of this document. As 
compared to the 2028 projections illustrated in plan figures 7-11 
through 7-19 as ``2028OTBa2 EPA w/o Fire Projection--MID'', these RPGs 
account for point-source controls resulting from ADEQ's four factor 
analyses. Appendix D, section D6 of the plan describes how 
SOX and NOX emissions reductions due to the 
controls were used to scale extinction as used in the IMPROVE equation, 
then summed and converted to deciviews. While the decreases in the RPGs 
from this procedure were quite small, the result better fits the 
regulatory definition of RPG as reflecting the effect of controls.

                                            Table 21--Arizona Baseline Conditions, Adjusted URP and 2028 RPGs
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                  20% Most-impaired days                            20% Clearest days
                                                          ----------------------------------------------------------------------------------------------
                           Site                                2000-2004                                                2000-2004
                                                                Baseline      2028 adjusted URP       2028 RPG           Baseline           2028 RPG
--------------------------------------------------------------------------------------------------------------------------------------------------------
BALD1....................................................               8.80               7.85               6.71               2.98               1.46
CHIR1....................................................              10.50               9.39               8.90               4.91               3.63
GRCA2....................................................               7.98               7.33               6.37               2.18               1.29
IKBA1....................................................              11.19               9.65               8.63               5.40               3.77
PEFO1....................................................               9.82               8.37               7.41               5.02               2.78
SAGU1....................................................              12.64              10.65              10.33               6.94               5.77
SIAN1 **.................................................              10.76               9.35               8.41               6.16               3.98
SYCA_RHTS................................................              12.16              10.14              10.73               5.58               3.43
TONT1....................................................              11.65              10.00               9.68               6.46               4.48
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Tables 10-1 and 10-2.
** 2013-2017 data is presented instead of 2014-2018 data for SIAN1 as it contains the most recent, complete 3-years dataset for SIAN1.

    As described in Section IV.E.2 of this document, we find that 
ADEQ's determination of emissions reduction measures that are necessary 
to make reasonable progress does not meet the requirements of section 
51.308(f)(2). Section 51.308(f)(3)(i) specifies that RPGs must reflect 
``enforceable emissions limitations, compliance schedules, and other 
measures required under paragraph (f)(2) of this section.'' We commend 
ADEQ for setting reasonable progress goals in an effort to meet the 
requirements of 51.308(f)(3) in Chapter 3 of the 2022 Arizona Regional 
Haze Plan. However, in the absence of an approved long-term strategy, 
we cannot approve the associated RPGs.
    We also note that for this planning period, all but one Arizona 
IMPROVE monitor are projected to have RPGs for the 20 percent most 
impaired days that provide for a greater rate of improvement in 
visibility than the

[[Page 47433]]

adjusted uniform rate of progress. The IMPROVE visibility monitor for 
the Sycamore Canyon Wilderness Class I area is projected to have a 0.59 
dv slower rate of visibility improvement than the uniform rate of 
progress by 2028.\222\ Section 51.308(f)(3)(ii) of the Regional Haze 
Rule requires that if a state adopts an RPG for the most impaired days 
that provides for a slower rate of improvement in visibility than the 
uniform rate of progress, i.e., if the RPG is above the URP glidepath, 
it must include within its SIP submission an assessment of the number 
of years it would take to attain natural visibility conditions if 
visibility improvement were to continue at the rate of progress 
selected by the state as reasonable for the implementation period. ADEQ 
provided a discussion in its submission that explains how the monitor 
was relocated in 2015 and experienced increases in soil and coarse mass 
extinction.\223\ However, the rule requires the state with the Class I 
area and any other state with sources affecting that area to make a 
``robust demonstration'' that there are no additional emissions 
reduction measures for sources that may reasonably be anticipated to 
contribute to visibility impairment that would be reasonable to include 
in the long-term strategy. The robust demonstration requires an 
analysis to ensure there are no additional emissions reduction measures 
that would be reasonable to include in the long-term strategy. Because 
we are proposing to find that ADEQ has not met the requirements of 
51.308(f)(2), we also propose to find that it has not satisfied 
51.308(f)(3)(ii) with respect to Sycamore Canyon.
---------------------------------------------------------------------------

    \222\ 2022 Arizona Regional Haze Plan, Chapter 10.1.
    \223\ 2022 Arizona Regional Haze Plan, Appendix A.
---------------------------------------------------------------------------

    Finally, we also note that Arizona has not considered whether 
sources in Arizona are reasonably anticipated to contribute to 
visibility impairment in a Class I area in another state whose RPG for 
the most impaired days in that Class I area is above the URP, as 
required under 40 CFR 51.308(f)(3)(ii)(B).
    For these reasons, we propose to disapprove Chapters 7 and 10 and 
Appendix D of the 2022 Arizona Regional Haze Plan for not meeting the 
requirements of 40 CFR 51.308(f)(3) pertaining to RPGs.

G. Additional Monitoring To Assess Reasonably Attributable Visibility 
Impairment

    The EPA and FLMs have not previously advised Arizona that 
additional monitoring is needed to assess reasonably attributable 
visibility impairment. Therefore, the requirements under 40 CFR 
51.308(f)(4) are not applicable to Arizona.

H. Monitoring Strategy and Other Implementation Plan Requirements

    Section 51.308(f)(6) specifies that each comprehensive revision of 
a state's regional haze SIP must contain or provide for certain 
elements, including monitoring strategies, emissions inventories, and 
any reporting, recordkeeping, and other measures needed to assess and 
report on visibility. A main requirement of this section is for states 
with Class I areas to submit monitoring strategies for measuring, 
characterizing, and reporting on visibility impairment. Compliance with 
this requirement may be met through participation in the IMPROVE 
network.
    According to Chapter 4 of the 2022 Arizona Regional Haze Plan, 
there are nine IMPROVE monitors and 12 Class 1 areas in Arizona, as 
summarized in Table 22 of this document. The monitoring sites are 
operated and maintained through a formal cooperative relationship 
between the EPA, NPS, FWS, USFS, and Bureau of Land Management.

                   Table 22--Arizona IMPROVE Monitors
------------------------------------------------------------------------
       IMPROVE monitor              Class I area              FLM
------------------------------------------------------------------------
BALD1........................  Mount Baldy            USFS.
                                Wilderness.
CHIR1........................  Chiricahua National    NPS.
                                Monument.
                               Chiricahua             USFS.
                                Wilderness, Galiuro
                                Wilderness.
GRCA2........................  Grand Canyon National  NPS.
                                Park.
IKBA1........................  Mazatzal Wilderness,   USFS.
                                Pine Mountain
                                Wilderness.
PEFO1........................  Petrified Forest       NPS.
                                National Park.
SAGU1........................  Saguaro National Park  NPS.
SIAN1........................  Sierra Ancha           USFS.
                                Wilderness.
SYCA2........................  Sycamore Canyon        USFS.
                                Wilderness.
TONT1........................  Superstition           USFS.
                                Wilderness.
------------------------------------------------------------------------
Source: 2022 Arizona Regional Haze Plan, Table 4-1.

    Section 51.308(f)(6)(i) requires SIPs to provide for the 
establishment of any additional monitoring sites or equipment needed to 
assess whether reasonable progress goals to address regional haze for 
all mandatory Class I Federal areas within the state are being 
achieved. Regional haze data for each Class I area in Arizona is 
collected by an IMPROVE monitor that is operated and maintained by the 
FLMs specified in Table 22 of this document. Pursuant to 40 CFR 
51.308(f)(6)(i), ADEQ does not recommend the establishment of any 
additional monitoring sites or equipment to assess whether reasonable 
progress goals to address regional haze for all Class I Federal areas 
within the State are being achieved. ADEQ also indicated that there 
have been incomplete years of data and temporarily closed sites. 
Arizona has engaged in discussions with IMPROVE, USFS, and the EPA on 
improving data collection at closed sites and hopes future site changes 
will increase data reliability.
    Section 51.308(f)(6)(ii) requires SIPs to provide for procedures by 
which monitoring data and other information are used in determining the 
contribution of emissions from within the state to regional haze 
visibility impairment at mandatory Class I Federal areas both within 
and outside the state.
    ADEQ indicates that pursuant to 40 CFR 51.308(f)(6)(ii), Chapters 
5, 6.4, and 9 of the 2022 Arizona Regional Haze Plan describe the 
procedures used in developing this SIP revision. These chapters include 
the procedures to assess the quantitative impact of emissions from 
Arizona on Class I Federal areas in Arizona and on Class I Federal 
areas that Arizona's emissions affect in other states. In general, the 
WRAP has analyzed and provided information on relative contributions to

[[Page 47434]]

visibility impairment for Arizona. Arizona has also used data reported 
by the IMPROVE program as input into the regional technical support 
analysis tool found at the Visibility Information Exchange Web System 
and WRAP's Technical Support System, as well as other analysis tools 
and efforts sponsored by the WRAP.
    Section 51.308(f)(6)(iii) does not apply to Arizona, as it has a 
Class I area.
    Section 51.308(f)(6)(iv) requires the SIP to provide for the 
reporting of all visibility monitoring data to the Administrator at 
least annually for each Class I area in the state. ADEQ indicates that 
it does not directly collect or handle IMPROVE data, and that ADEQ will 
continue to participate in the IMPROVE Visibility Information Exchange 
Web System for reporting monitoring data. As noted in Table 22 of this 
document, the IMPROVE monitors are operated and maintained by FLMs. The 
monitoring strategy for Arizona relies upon the continued availability 
of the IMPROVE network.
    Section 51.308(f)(6)(v) requires SIPs to provide for a statewide 
inventory of emissions of pollutants that are reasonably anticipated to 
cause or contribute to visibility impairment, including emissions for 
the most recent year for which data are available and estimates of 
future projected emissions. It also requires a commitment to update the 
inventory periodically.
    Chapter 6 and Appendix B of the 2022 Arizona Regional Haze Plan 
describe the procedures used to produce the statewide emissions 
inventory of pollutants reasonably anticipated to cause or contribute 
to visibility impairment in the Class I Federal areas that Arizona's 
emissions affect. ADEQ indicates that their plan relies primarily upon 
four different emissions inventory scenarios: 2014v2, RepBase2, 
2028OTBa2, and 2028LTS. Three of those scenarios (2014v2, RepBase2, 
2028OTBa2) were developed by WRAP utilizing methods agreed upon by 
member states, local air agencies, and western Tribal organizations and 
in coordination with FLMs and the EPA. The WRAP 2014v2 inventory is 
based on the 2014v2 NEI plus updates provided by western states through 
the WRAP Regional Haze workgroup's Emissions and Modeling Protocol 
subcommittee. The Representative Baseline (RepBase2) emissions scenario 
updates the 2014v2 inventory to account for changes and variation in 
emissions between 2014 and 2018 for key WRAP source sectors, as defined 
by the WRAP Emissions and Modeling Protocol subcommittee.
    Section 51.308(f)(6)(v) also requires states to include estimates 
of future projected emissions and include a commitment to update the 
inventory periodically.
    ADEQ described its 2028 emissions projection methodology in Chapter 
6 and Appendix B Section B3 of the 2022 Arizona Regional Haze Plan. 
ADEQ indicates that the WRAP 2028OTBa emissions inventory projection 
follows the methods applied in the EPA 2019 Modeling TSD. The WRAP 
states updated source sectors to account for implementation of all 
applicable federal and state requirements for U.S. anthropogenic 
emissions by 2028.
    The 2028LTS is an emissions inventory developed by ADEQ with the 
2028OTBa2 as a base. The scenario adjusts 2028OTBa2 emissions to 
account for those controls included within ADEQ's long-term strategy 
for which statewide emission reductions could be estimated. Arizona has 
also committed in its SIP submittal to periodically update the 
emissions inventories which will include incorporation of emissions 
reductions from any new or ongoing air pollution control programs and 
any new source retirement/replacement schedules.\224\
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    \224\ 2022 Arizona Regional Haze Plan, Chapter 6.4.
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    The EPA proposes to find that Arizona has met the requirements of 
40 CFR 51.308(f)(6) as described above, including through its continued 
participation in the IMPROVE network, continued inventory work with the 
WRAP, and commitment to update the inventory periodically, and that no 
further elements are necessary at this time for Arizona to assess and 
report on visibility pursuant to 40 CFR 51.308(f)(6)(vi). The EPA 
therefore is proposing to approve Chapters 4 and 6.4 of the 2022 
Arizona Regional Haze Plan as meeting the requirements of 40 CFR 
51.308(f)(6).

I. Requirements for Periodic Reports Describing Progress Towards the 
Reasonable Progress Goals

    Section 51.308(f)(5) requires that periodic comprehensive revisions 
of states' regional haze plans also address the progress report 
requirements of 40 CFR 51.308(g)(1)-(5). The purpose of these 
requirements is to evaluate progress towards the applicable RPGs for 
each Class I area within the state and each Class I area outside the 
state that may be affected by emissions from within that state. 
Sections 51.308(g)(1) and (2) apply to all states and require a 
description of the status of implementation of all measures included in 
a state's first implementation period regional haze plan and a summary 
of the emissions reductions achieved through implementation of those 
measures. Section 51.308(g)(3) applies only to states with Class I 
areas within their borders and requires such states to assess current 
visibility conditions, changes in visibility relative to baseline 
(2000-2004) visibility conditions, and changes in visibility conditions 
relative to the period addressed in the first implementation period 
progress report. Section 51.308(g)(4) applies to all states and 
requires an analysis tracking changes in emissions of pollutants 
contributing to visibility impairment from all sources and sectors 
since the period addressed by the first implementation period progress 
report. This provision further specifies the year, or years, through 
which the analysis must extend depending on the type of source and the 
platform through which its emissions information is reported. In 
addition, section 51.308(g)(5), which also applies to all states, 
requires an assessment of any significant changes in anthropogenic 
emissions within or outside the state have occurred since the period 
addressed by the first implementation period progress report, including 
whether such changes were anticipated and whether they have limited or 
impeded expected progress towards reducing emissions and improving 
visibility.
    Section 51.308(f)(5) specifies that a progress report submitted as 
part of a comprehensive regional haze SIP revision must address the 
time period since the most recent progress report. Arizona submitted 
its most recent progress report to the EPA on November 12, 2015, which 
presented data analysis for the period 2009 through 2013.\225\ 
Therefore, for Arizona, the time period required to be addressed in the 
progress report began in 2014.
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    \225\ 84 FR 33002 (July 11, 2019).
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    Arizona's submission also describes the status of measures of the 
long-term strategy from the first implementation period, explaining the 
controls required under both the SIP and FIP and how those controls 
have been implemented.\226\
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    \226\ 2022 Arizona Regional Haze Plan, Chapter 11 and 2023 
Arizona Regional Haze Technical Supplement.
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    Arizona's submission also contains a summary of the emissions from 
the long-term strategy from the first implementation period for 
NOX, SO2, and PM10 at BART 
facilities.\227\ In total, ADEQ estimated reductions of 21,296

[[Page 47435]]

tpy NOX, 34,533-38,999 tpy SO2, and 849 tpy 
PM10.
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    \227\ 2022 Arizona Regional Haze Plan, Table 11-8.
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    The EPA therefore proposes to find that Arizona has met the 
requirements of 40 CFR 51.308(g)(1) and (2) because its SIP submission 
describes the measures included in the long-term strategy from the 
first implementation period, as well as the status of their 
implementation and the emission reductions achieved through such 
implementation.
    Arizona's SIP submission included summaries of the visibility 
conditions and the trend of the 5-year averages at the Class I 
areas.\228\ The SIP submission included the 5-year baseline (2000-2004) 
visibility conditions and current conditions (2015-2019) for the 
clearest and most impaired days, as discussed in Section IV.D of this 
document. The EPA therefore proposes to find that Arizona has met the 
requirements of 40 CFR 51.308(g)(3).
---------------------------------------------------------------------------

    \228\ 2022 Arizona Regional Haze Plan, Chapter 5.
---------------------------------------------------------------------------

    In a technical supplement sent on November 22, 2023 (``2023 Arizona 
Regional Haze Technical Supplement''),\229\ ADEQ provided additional 
supporting information to address the requirements of 40 CFR 
51.308(g)(4)-(5). Pursuant to section 51.308(g)(4), Arizona provided a 
summary of emissions of NOX, SO2, 
PM10, PM2.5, VOC, and NH3 from all 
sources and activities, including from point, nonpoint, non-road 
mobile, and on-road mobile sources for the progress report period, 
using the 2014 and 2017 NEI. ADEQ also provided 2014-2019 Clean Air 
Markets Program Data (CAMPD) data for all sources with emissions of 
visibility impairing pollutants. The reductions achieved by Arizona 
emissions control measures are seen in the emissions inventory and 
visibility progress. The EPA is therefore proposing to find that 
Arizona has met the requirements of section 51.308(g)(4) by providing 
emissions information for NOX, SO2, 
PM10, PM2.5, VOC, and NH3 broken down 
by type of sources and activities within the state.
---------------------------------------------------------------------------

    \229\ Letter dated November 22, 2023, from Hether Krause, Deputy 
Assistant Director, ADEQ Air Quality Division, to Martha Guzman, 
Regional Administrator, EPA Region IX (submitted electronically 
November 22, 2023).
---------------------------------------------------------------------------

    Pursuant to section 51.308(g)(5), Arizona provided an assessment of 
any significant changes in anthropogenic emissions within or outside 
the state that have occurred since the period, including whether or not 
these changes in anthropogenic emissions were anticipated in that most 
recent plan, and whether they have limited or impeded progress in 
reducing pollutant emissions and improving visibility.\230\ ADEQ noted 
overall reductions of 21 percent in NOX, 11 percent in 
SO2, and 48 percent in VOC using NEI data. ADEQ also noted 
overall reductions of 45 percent NOX and 47 percent 
SO2 in CAMPD EGU emissions during the progress report 
period. ADEQ indicated that these reductions have met or exceeded the 
downward trend predicted from the regional haze plan in the first 
round. For NH3, ADEQ noted increases from the agriculture 
sector, but primarily from a different methodology used to calculate 
the emissions. ADEQ noted that the increases in NH3 have not 
limited or impeded visibility progress. The EPA is proposing to find 
that Arizona has met the requirements of section 51.308(g)(5).
---------------------------------------------------------------------------

    \230\ 2023 Arizona Regional Haze Technical Supplement, Section 
3.
---------------------------------------------------------------------------

    Additionally, the 2022 Arizona Regional Haze SIP includes a 
commitment to submit periodic progress reports in accordance with 
section 51.308(f) \231\ and a commitment to evaluate progress towards 
the reasonable progress goal for each mandatory Class I Federal area 
located within the state and in each mandatory Class I Federal area 
located outside the state that may be affected by emissions from within 
the state in accordance with section 51.308(g).\232\
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    \231\ 40 CFR 51.308(f) (``. . . The [regional haze SIP] revision 
due on or before July 31, 2021, must include a commitment by the 
State to meet the requirements of paragraph (g) of this section. . . 
.''
    \232\ 2022 Arizona Regional Haze Plan, Chapter 11.4.
---------------------------------------------------------------------------

    For these reasons, the EPA proposes to approve Chapter 11 of the 
2022 Arizona Regional Haze Plan (as supplement by the 2023 Arizona 
Regional Haze Technical Supplement) as meeting the requirements of 40 
CFR 51.308(f)(5) and 40 CFR 51.308(g)(1)-(5) for periodic progress 
reports.

J. Requirements for State and Federal Land Manager Coordination

    CAA section 169A(d) requires states to consult with FLMs before 
holding the public hearing on a proposed regional haze SIP, and to 
include a summary of the FLMs' conclusions and recommendations in the 
notice to the public. In addition, the FLM consultation provision in 
section 51.308(i)(2) requires a state to provide FLMs with an 
opportunity for consultation that is early enough in the state's policy 
analyses of its emissions reduction obligation so that information and 
recommendations provided by the FLMs can meaningfully inform the 
state's decisions on its long-term strategy. If the consultation has 
taken place at least 120 days before a public hearing or public comment 
period, the opportunity for consultation will be deemed early enough. 
Regardless, the opportunity for consultation must be provided at least 
sixty days before a public hearing or public comment period at the 
state level. Section 51.308(i)(2) also provides two substantive topics 
on which FLMs must be provided an opportunity to discuss with states: 
assessment of visibility impairment in any Class I area and 
recommendations on the development and implementation of strategies to 
address visibility impairment. Section 51.308(i)(3) requires states, in 
developing their implementation plans, to include a description of how 
they addressed FLMs' comments.
    ADEQ met with USFS and NPS and communicated with the FLMs via email 
on multiple occasions before providing the draft SIP to those agencies 
for comment.\233\ ADEQ indicated that the purpose of these meetings was 
to discuss source screening methodologies, selection of particulate 
matter species for analysis, effective control determinations, initial 
control determinations, and general consultation on the formation of 
the long-term strategy. ADEQ also indicated that FWS was invited to 
these events but did not participate.
---------------------------------------------------------------------------

    \233\ 2022 Arizona Regional Haze Plan, Chapter 2.4.2 and Table 
2-2.
---------------------------------------------------------------------------

    On January 4, 2022, Arizona submitted a draft Regional Haze SIP to 
the FLMs for a 60-day review and comment period pursuant to 40 CFR 
51.308(i)(2).\234\ ADEQ also met with USFS and NPS on January 13, 2022, 
to present the draft SIP revision, answer questions, and receive 
initial feedback. Arizona received comments from the USFS on March 10, 
2022, and from the NPS on March 11, 2022. ADEQ responded to the FLM 
comments and included the responses in Appendix L of their submission 
to the EPA, in accordance with section 51.308(i)(3).
---------------------------------------------------------------------------

    \234\ 2022 Arizona Regional Haze Plan, Chapter 2.4.
---------------------------------------------------------------------------

    However, as explained above, because the EPA is proposing to 
disapprove certain elements of Arizona's SIP revision, namely the long-
term strategy under 51.308(f)(2) and the reasonable progress goals 
under 51.308(f)(3), the EPA is also proposing to disapprove the Plan 
with respect to the FLM consultation requirements under 51.308(i). 
While Arizona did take administrative steps to provide the FLMs the 
requisite opportunity to review and provide feedback on the state's 
initial draft plan, the EPA cannot approve the requirements under

[[Page 47436]]

51.308(f)(i) because Arizona's consultation was based on a SIP revision 
that did not meet the required statutory and regulatory requirements of 
the CAA and the RHR, respectively. Additionally, we note that ADEQ did 
not indicate whether the 2023 Arizona Regional Haze Rules Supplement 
went through the FLM 60-day review period pursuant to 40 CFR 
51.308(i)(2). In addition, if the EPA finalizes the partial approval 
and partial disapproval of the Plan, as proposed in this document, in 
the process of correcting the deficiencies outlined above with respect 
to the RHR and statutory requirements, the state (or the EPA in the 
case of an eventual FIP) will be required to again satisfy the FLM 
consultation requirement under 51.308(i). Therefore, we are proposing 
to disapprove Section 2.4 (``Consultation with Federal Land Managers'') 
and Appendix L of the 2022 Arizona Regional Haze Plan for not meeting 
the requirements under 40 CFR 51.308(i) as outlined in this section.

V. Prong 4 (Visibility) of the 2012 PM[bdi2].[bdi5] NAAQS 
and 2015 Ozone NAAQS Infrastructure SIPs

A. Infrastructure SIPs

    Under CAA sections 110(a)(1) and 110(a)(2), each state is required 
to submit a SIP that provides for the implementation, maintenance, and 
enforcement of each primary or secondary NAAQS. Moreover, CAA section 
110(a)(1) and section 110(a)(2) require each state to make this new SIP 
submission within three years (or less, if the Administrator so 
prescribes) after promulgation of a new or revised NAAQS. This type of 
SIP submission is commonly referred to as an ``infrastructure SIP.'' 
The overall purpose of the infrastructure SIP requirements is to ensure 
that the necessary structural components of each state's air quality 
management program are adequate to meet the state's responsibilities 
for the new or revised NAAQS. Overall, the infrastructure SIP 
submission process provides an opportunity for the responsible air 
agency, the public, and the EPA to review the basic structural 
requirements of the air agency's air quality management program in 
light of each new or revised NAAQS.
    Section 110(a)(2)(D) has two components: 110(a)(2)(D)(i) and 
110(a)(2)(D)(ii). Section 110(a)(2)(D)(i) includes four distinct 
components, commonly referred to as ``prongs,'' that must be addressed 
in infrastructure SIP submissions. The first two prongs, which are 
codified in section 110(a)(2)(D)(i)(I), prohibit any source or other 
type of emissions activity in one state from contributing significantly 
to nonattainment of the NAAQS in another state (prong 1) and from 
interfering with maintenance of the NAAQS in another state (prong 2). 
The third and fourth prongs, which are codified in section 
110(a)(2)(D)(i)(II), prohibit emissions activity in one state from 
interfering with measures required to prevent significant deterioration 
of air quality in another state (prong 3) or from interfering with 
measures to protect visibility in another state (prong 4).

B. Prong 4 Requirements

    Section 110(a)(2)(D)(i)(II) requires SIPs to contain provisions 
prohibiting sources in that state from emitting pollutants in amounts 
that interfere with any other state's efforts to protect visibility 
under part C of the CAA (which includes sections 169A and 169B). The 
EPA issued guidance on infrastructure SIPs in a September 13, 2013 
memorandum from Stephen D. Page titled ``Guidance on Infrastructure 
State Implementation Plan (SIP) Elements under Clean Air Act Sections 
110(a)(1) and 110(a)(2)'' (``2013 Guidance''). The 2013 Guidance states 
that these prong 4 requirements can be satisfied by approved SIP 
provisions that the EPA has found to adequately address any 
contribution of that state's sources that impact the visibility program 
requirements in other states. The 2013 Guidance also states that the 
EPA interprets this prong to be pollutant-specific, such that the 
infrastructure SIP submission need only address the potential for 
interference with protection of visibility caused by the pollutant 
(including precursors) to which the new or revised NAAQS applies.
    The 2013 Guidance lays out how a state's infrastructure SIP may 
satisfy prong 4. In the second planning period, confirmation that the 
state has a fully approved regional haze SIP that fully meets the 
requirements of 40 CFR 51.308 or 51.309 will satisfy the requirements 
of prong 4.\235\ The regulations at 40 CFR 51.308 and 51.309 
specifically require that a state participating in a regional planning 
process include all measures needed to achieve its apportionment of 
emission reduction obligations agreed upon through that process. A 
fully approved regional haze SIP \236\ will ensure that emissions from 
sources under an air agency's jurisdiction are not interfering with 
measures required to be included in other air agencies' plans to 
protect visibility.
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    \235\ The EPA acknowledges that in the 2013 Guidance, we 
indicate that the EPA may find it appropriate to supplement the 
guidance regarding the relationship between regional haze SIPs and 
prong 4 after second planning SIPs become due, which occurred on 
July 31, 2021. After a review of the 2013 guidance and the second 
planning period regional haze requirements, the EPA maintains the 
interpretation that a fully approved regional haze SIP satisfies 
Prong 4 requirements in the second planning period.
    \236\ Since second planning period SIPs became due, a ``fully 
approved regional haze SIP'' would necessarily include fully 
approved first and second planning period regional haze SIPs.
---------------------------------------------------------------------------

    Through this action, the EPA is proposing to disapprove the prong 4 
portion of Arizona's infrastructure SIP submissions for the 2012 
PM2.5 and 2015 ozone NAAQS. All other applicable 
infrastructure SIP requirements for these SIP submissions have been or 
will be addressed in separate rulemakings. A brief background regarding 
the NAAQS relevant to this proposal is provided in the following 
sections.
1. 2012 PM2.5 NAAQS
    On December 14, 2012, the EPA revised the annual primary 
PM2.5 NAAQS to 12 [mu]g/m\3\.\237\ States were required to 
submit infrastructure SIP submissions for the 2012 PM2.5 
NAAQS to the EPA within three years of promulgation of the revised 
NAAQS. Arizona submitted its infrastructure SIP for the 2012 
PM2.5 NAAQS on December 11, 2015 (``2015 PM2.5 I-
SIP submittal'').\238\ This proposed rulemaking only addresses the 
prong 4 element of 2015 PM2.5 I-SIP submittal.
---------------------------------------------------------------------------

    \237\ 78 FR 3086 (January 15, 2013).
    \238\ Letter dated December 11, 2015, from Eric Massey, 
Director, Air Quality Division, ADEQ, to Jared Blumenfeld, Regional 
Administrator, EPA Region IX.
---------------------------------------------------------------------------

2. 2015 Ozone NAAQS
    On October 26, 2015, the EPA revised the 8-hour ozone NAAQS to 70 
parts per billion.\239\ States were required to submit infrastructure 
SIPs within three years of promulgation of the revised NAAQS. Arizona 
submitted its infrastructure SIP for the 2015 ozone NAAQS on September 
24, 2018 (``2018 Ozone I-SIP submittal'').\240\ This proposed 
rulemaking only addresses the prong 4 element of the 2018 Ozone I-SIP 
submittal.\241\
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    \239\ 80 FR 65292 (October 26, 2015).
    \240\ Letter dated September 24, 2018, from Timothy S. 
Franquist, Director, Air Quality Division, ADEQ, to Michael Stoker, 
Regional Administrator, EPA Region IX (submitted electronically 
September 24, 2018).
    \241\ The EPA proposed action on the rest of the 2018 Ozone I-
SIP submittal in two separate rulemakings. See 87 FR 37776 (June 24, 
2022) and 87 FR 74349 (December 5, 2022). On February 16, 2024, the 
EPA issued a supplemental proposal regarding transport prongs 1 and 
2 (88 FR 12666). The EPA proposed to partially approve the 2018 
Ozone I-SIP submittal with respect to Prong 1 and to partially 
disapprove the 2018 Ozone I-SIP submittal with respect to Prong 2.

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[[Page 47437]]

C. Arizona's Prong 4 Elements

    Arizona's 2018 Ozone I-SIP submittal and 2015 PM2.5 I-
SIP submittal acknowledge that Arizona does not currently have a fully 
approved Regional Haze SIP. They therefore rely, in part, on 
regulations imposed by FIPs during the first planning period to address 
visibility impairment in Class I Areas caused by NOX, 
SO2, and PM.\242\ The FIPs include emissions limits for the 
following facilities: Freeport McMoran Miami Smelter,\243\ Asarco 
Hayden Smelter,\244\ Sundt Generating Station Unit 4,\245\ Nelson Lime 
Plant Kilns 1 and 2,\246\ CPC Rillito Kiln 4,\247\ and PCC Clarkdale 
Kiln 4.\248\ Emissions limits have been incorporated into the state 
SIP, replacing previous FIPs, at AEPCO Apache Generating Station Units 
1, 2, and 3,\249\ APS Cholla Power Plant Units 1-4,\250\ and SRP 
Coronado Generating Station Units 1 and 2.\251\
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    \242\ Arizona Infrastructure SIP for the 2012 PM2.5 
NAAQS, p. 11; Arizona Infrastructure SIP for the 2015 Ozone NAAQS, 
pp. 15-16.
    \243\ 79 FR 52420 (September 3, 2014).
    \244\ Id.
    \245\ Id. Sundt Generating Station is also known as Irvington 
Generating Station.
    \246\ Id.
    \247\ 81 FR 83144 (November 21, 2016).
    \248\ Id.
    \249\ 80 FR 19220 (April 10, 2015).
    \250\ 82 FR 15139 (March 27, 2017).
    \251\ 82 FR 46903 (October 10, 2017).
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D. The EPA's Evaluation of Arizona's Submittal

    Because Arizona does not have a fully approved regional haze plan 
for the first or second planning period, it cannot rely on a fully 
approved regional haze SIP in order to fulfill the prong 4 requirements 
for the 2012 PM2.5 and 2015 ozone NAAQS. Consequently, the 
EPA is proposing to disapprove the prong 4 portion of Arizona's 2018 
Ozone I-SIP submittal and 2015 PM2.5 I-SIP submittal.

VI. Proposed Action

    For the reasons discussed in this notice, under CAA section 
110(k)(3), the EPA is proposing to partially approve and partially 
disapprove the 2022 Arizona Regional Haze Plan. We propose to approve 
the following portions of the 2022 Arizona Regional Haze Plan:
     Chapter 5 and Appendix A of the 2022 Arizona Regional Haze 
Plan as meeting the 40 CFR 51.308(f)(1) requirements related to 
calculations of baseline, current, and natural visibility conditions, 
progress to date, and the uniform rate of progress;
     Chapters 4 and 6.4 of the 2022 Arizona Regional Haze Plan 
as meeting the 40 CFR 51.308(f)(4) requirements for additional 
monitoring to assess reasonably attributable visibility impairment, 
which is not applicable to Arizona;
     Chapter 11 of the 2022 Arizona Regional Haze Plan and the 
2023 Arizona Regional Haze Technical Supplement as meeting the 40 CFR 
51.308(f)(5) requirements for the plan to serve as a progress report;
     Chapters 4 and 6.4 of the Arizona Regional Haze Plan as 
meeting the 40 CFR 51.308(f)(6) monitoring strategy requirements; and
     Chapter 11 of the 2022 Arizona Regional Haze Plan and the 
2023 Arizona Regional Haze Technical Supplement as meeting the 40 CFR 
51.308 (g)(1)-(5) progress report requirements.
    Additionally, the EPA is proposing to approve Chapters 1 
(``Regional Haze Program Overview'') and 3 (``Description of Arizona 
Class I Federal Areas'') as supporting information. The EPA is 
excluding Appendix I (``Authorizing Statutes'') of the 2022 Arizona 
Regional Haze Plan, which provides information on the authorizing 
statutes in Arizona, from our action.
    The EPA is proposing to disapprove the following portions of the 
2022 Arizona Regional Haze Plan:
     Chapters 2, 6.1-6.3, 8, and 9 and Appendices B, C, E, F, 
G, H, and J of the 2022 Arizona Regional Haze Plan for not meeting the 
40 CFR 51.308(f)(2) long-term strategy requirement;
     Chapters 7 and 10, and Appendix D of the 2022 Arizona 
Regional Haze Plan for not meeting the 40 CFR 51.308(f)(3) reasonable 
progress goals requirement;
     Chapter 2.4 (``Consultation with Federal Land Managers'') 
and Appendix L of the 2022 Arizona Regional Haze Plan for not meeting 
the 40 CFR 51.308(i)(2)-(4) FLM consultation requirements.
    Further, the EPA is proposing to disapprove the interstate 
transport requirements of CAA section 110(a)(2)(D)(i)(II) prong 4 
(visibility) for the 2018 Ozone I-SIP submittal and 2015 
PM2.5 I-SIP submittal.
    Under section 179(a) of the CAA, final disapproval of a submittal 
that addresses a requirement of part D, title I of the CAA or is 
required in response to a finding of substantial inadequacy as 
described in CAA section 110(k)(5) (SIP Call) starts a sanctions clock. 
Arizona's 2022 Regional Haze Plan, 2018 Ozone I-SIP submittal, and 2015 
PM2.5 I-SIP submittal were not submitted to meet any of 
these requirements. Therefore, if finalized, these disapprovals would 
not trigger any offset or highway sanctions clocks. Disapproving a SIP 
submission also establishes a two-year deadline for the EPA to 
promulgate a FIP to address the relevant requirements under CAA section 
110(c), unless the EPA approves a subsequent SIP submission that meets 
these requirements. We anticipate that, if these disapprovals are 
finalized, any SIP or FIP that remedies the disapprovals with respect 
to Regional Haze requirements, would also, in conjunction with the 
existing Arizona Regional Haze FIP, remedy the disapproval for the 
interstate transport visibility requirement of CAA section 
110(a)(2)(D)(i)(II) for the 2018 Ozone I-SIP submittal and 2015 
PM2.5 I-SIP submittal.

VII. Statutory and Executive Order Reviews

    Under the CAA, the Administrator is required to approve a SIP 
submission that complies with the provisions of the Act and applicable 
federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in 
reviewing SIP submissions, the EPA's role is to review state choices, 
and approve those choices if they meet the minimum criteria of the Act. 
Accordingly, this proposed rulemaking proposes to partially approve and 
partially disapprove state law as meeting federal requirements and does 
not impose additional requirements beyond those imposed by state law.
    Additional information about these statutes and Executive Orders 
can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive 
Order 13563: Improving Regulation and Regulatory Review

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

B. Paperwork Reduction Act (PRA)

    This action does not impose an information collection burden under 
the PRA because this action does not impose additional requirements 
beyond those imposed by state law.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action will not impose any requirements on small entities beyond those 
imposed by state law.

[[Page 47438]]

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in 
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect 
small governments. This action does not impose additional requirements 
beyond those imposed by state law. Accordingly, no additional costs to 
state, local, or Tribal governments, or to the private sector, will 
result from this action.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the national government and the states, or on the distribution of power 
and responsibilities among the various levels of government.

F. Executive Order 13175: Coordination With Indian Tribal Governments

    This action does not have Tribal implications, as specified in 
Executive Order 13175, because the SIP is not approved to apply on any 
Indian reservation land or in any other area where the EPA or an Indian 
Tribe has demonstrated that a Tribe has jurisdiction, and will not 
impose substantial direct costs on Tribal governments or preempt Tribal 
law. Thus, Executive Order 13175 does not apply to this action.

G. Executive Order 13045: Protection of Children From Environmental 
Health Risks and Safety Risks

    The EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that concern environmental health or safety risks 
that the EPA has reason to believe may disproportionately affect 
children, per the definition of ``covered regulatory action'' in 
section 2-202 of the Executive Order. Therefore, this action is not 
subject to Executive Order 13045 because it merely proposes to 
partially approve and partially disapprove state law as meeting federal 
requirements. Furthermore, the EPA's Policy on Children's Health does 
not apply to this action.

H. Executive Order 13211: Actions That Significantly Affect Energy 
Supply, Distribution, or Use

    This action is not subject to Executive Order 13211, because it is 
not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act (NTTAA)

    Section 12(d) of the NTTAA directs the EPA to use voluntary 
consensus standards in its regulatory activities unless to do so would 
be inconsistent with applicable law or otherwise impractical. The EPA 
believes that this action is not subject to the requirements of section 
12(d) of the NTTAA because application of those requirements would be 
inconsistent with the CAA.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Population

    Executive Order 12898 (Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations, 59 FR 7629, 
Feb. 16, 1994) directs Federal agencies to identify and address 
``disproportionately high and adverse human health or environmental 
effects'' of their actions on minority populations and low-income 
populations to the greatest extent practicable and permitted by law. 
The EPA defines environmental justice (EJ) as ``the fair treatment and 
meaningful involvement of all people regardless of race, color, 
national origin, or income with respect to the development, 
implementation, and enforcement of environmental laws, regulations, and 
policies.'' The EPA further defines the term fair treatment to mean 
that ``no group of people should bear a disproportionate burden of 
environmental harms and risks, including those resulting from the 
negative environmental consequences of industrial, governmental, and 
commercial operations or programs and policies.''
    The State did not evaluate environmental justice considerations as 
part of its SIP submittals; the CAA and applicable implementing 
regulations neither prohibit nor require such an evaluation. The EPA 
did not perform an EJ analysis and did not consider EJ in this action. 
Due to the nature of the action being taken here, if finalized, this 
action is expected to have a neutral to positive impact on the air 
quality of the affected area. Consideration of EJ is not required as 
part of this action, and there is no information in the record 
inconsistent with the stated goal of E.O. 12898 of achieving 
environmental justice for people of color, low-income populations, and 
Indigenous peoples.

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Nitrogen dioxide, Ozone, Particulate matter, Sulfur oxides.

    Dated: May 23, 2024.
Martha Guzman Aceves,
Regional Administrator, Region IX.
[FR Doc. 2024-11807 Filed 5-30-24; 8:45 am]
BILLING CODE 6560-50-P