Proposed Rule2025-19280
Visibility Protection: Regional Haze State Plan Requirements Rule Revision
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
October 2, 2025
Issuing agencies
Environmental Protection Agency
Abstract
The Environmental Protection Agency (EPA or Agency) is soliciting information and requesting comment to assist in the development of regulatory changes pertaining to the restructuring of the Regional Haze Rule (RHR). Under the current RHR, states must submit state implementation plans (SIPs) to protect visibility in mandatory Class I Federal areas (Class I areas) to demonstrate reasonable progress towards the national visibility goal. The Agency is seeking input regarding how the EPA can meaningfully revise the RHR to streamline regulatory requirements impacting states' visibility improvement obligations under the Clean Air Act (CAA).
Full Text
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<title>Federal Register, Volume 90 Issue 189 (Thursday, October 2, 2025)</title>
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[Federal Register Volume 90, Number 189 (Thursday, October 2, 2025)]
[Proposed Rules]
[Pages 47677-47686]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-19280]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 51
[EPA-HQ-OAR-2025-1477; FRL-6714-04-OAR]
RIN 2060-AU01
Visibility Protection: Regional Haze State Plan Requirements Rule
Revision
AGENCY: Environmental Protection Agency (EPA).
ACTION: Advance notice of proposed rulemaking.
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SUMMARY: The Environmental Protection Agency (EPA or Agency) is
soliciting information and requesting comment to assist in the
development of regulatory changes pertaining to the restructuring of
the Regional Haze Rule (RHR). Under the current RHR, states must submit
state implementation plans (SIPs) to protect visibility in mandatory
Class I Federal areas (Class I areas) to demonstrate reasonable
progress towards the national visibility goal. The Agency is seeking
input regarding how the EPA can meaningfully revise the RHR to
streamline regulatory requirements impacting states' visibility
improvement obligations under the Clean Air Act (CAA).
DATES: Comments must be received on or before December 1, 2025.
ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OAR-2025-1477, by any of the following methods:
Federal eRulemaking Portal: <a href="https://www.regulations.gov/">https://www.regulations.gov/</a> (our
preferred method). Follow the online instructions for submitting
comments.
Instructions: All submissions received must include the Docket ID
No. for this rulemaking. Comments received may be posted without change
to <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>, including any personal information
provided. For detailed instructions on sending comments and additional
information on the rulemaking process, see the ``Public Participation''
heading of the SUPPLEMENTARY INFORMATION section of this document.
FOR FURTHER INFORMATION CONTACT: Ms. Paige Wantlin, Air Quality Policy
Division, Office of Air Quality Planning and Standards (Mail code C539-
01), Environmental Protection Agency, 109 TW Alexander Drive, Research
Triangle Park, NC 27711; telephone number: (919) 541-5670; email
address: <a href="/cdn-cgi/l/email-protection#4215232c362e2b2c6c12232b2527022732236c252d34"><span class="__cf_email__" data-cfemail="4d1a2c2339212423631d2c242a280d283d2c632a223b">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Public Participation
Written Comments
Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2025-
1477, at <a href="https://www.regulations.gov">https://www.regulations.gov</a> (our preferred method), or the
other methods identified in the ADDRESSES section. Once submitted,
comments cannot be edited or removed from the docket. The EPA may
publish any comment received to its public docket. The EPA requests
that reviewers and commenters number their responses, for example, if
responding to Topic 1, Question 1.a., please use the Topic and Question
within a header before providing a response. Do not submit to EPA's
docket at <a href="https://www.regulations.gov">https://www.regulations.gov</a> any information you consider to
be Confidential Business Information (CBI), Proprietary Business
Information (PBI), 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). Please visit <a href="https://www.epa.gov/dockets/commenting-epa-dockets">https://www.epa.gov/dockets/commenting-epa-dockets</a> for additional submission methods; the
full EPA public comment policy; information about CBI, PBI, or
multimedia submissions; and general guidance on making effective
comments.
II. General Information
A. Preamble Glossary of Terms and Acronyms
The following are abbreviations of terms used in this document.
ANPRM Advance notice of proposed rulemaking
NH<INF>3</INF> Ammonia
BACT Best available control technology
BART Best available retrofit technology
CAA Clean Air Act
CBI Confidential business information
CFR Code of Federal Regulations
Class I areas Class I Federal areas
EPA Environmental Protection Agency
FIP Federal implementation plan
FLM Federal land manager
LAER Lowest achievable emissions rate
NAAQS National Ambient Air Quality Standards
NO<INF>X</INF> Nitrogen oxide
OMB Office of Management and Budget
PM Particulate matter
PM<INF>2.5</INF> Particulate matter equal to or less than 2.5
microns in diameter (fine particulate matter)
PM<INF>10</INF> Particulate matter equal to or less than 10 microns
in diameter
PSD Prevention of significant deterioration
PBI Proprietary business information
RACT Reasonable available control technology
RAVI Reasonably attributable visibility impairment
RPG Reasonable progress goal
RHR Regional Haze Rule
SIP State implementation plan
SO<INF>2</INF> Sulfur dioxide
URP Uniform rate of progress
U.S. United States
VOC Volatile organic compound
B. How is this Federal Register document organized?
The information presented in this document is organized as follows:
I. Public Participation
II. General Information
[[Page 47678]]
A. Preamble Glossary of Terms and Acronyms
B. How is this Federal Register document organized?
C. Executive Summary
D. What is the purpose of this ANPRM?
E. Does this action apply to me?
III. What is the background for the EPA's proposed action?
A. Regional Haze
B. Requirements for Regional Haze SIPs for the First Planning
Period
C. Requirements for Regional Haze SIPs for the Second Planning
Period
D. EPA's 2024 Non-Regulatory Docket
IV. Request for Comments and Feedback
A. Overview and Introduction
B. Topic 1: Development and Implementation of a Reasonable
Progress Metric and Consideration of the Four Statutory Factors
C. Topic 2: Development of Criteria Used To Determine When a SIP
Revision Is Necessary
D. Topic 3: Determining SIP Content Requirements
V. Request for Comment and Additional Information
VI. What are the next steps EPA will take?
VII. Statutory and Executive Orders Reviews
C. Executive Summary
The Regional Haze program, established under Clean Air Act sections
169A and 169B, pertains to addressing visibility impairment in the 156
mandatory class I Federal areas, which includes specific national parks
and wilderness areas. The program targets visibility impairment caused
by manmade air pollution, primarily from industrial sources, vehicles,
and other human activities. Emissions of pollutants such as sulfur
dioxide (SO<INF>2</INF>), nitrogen oxides (NO<INF>X</INF>), and
particulate matter contribute significantly to Regional Haze. The goals
of the program are to prevent future, and remedy existing, impairment
of visibility in identified Class I areas from manmade air pollution. A
key statutory component of the program is the requirement for states to
develop state implementation plans (SIPs), which outline strategies for
achieving reasonable progress toward the national visibility goal
articulated under CAA section 169A(a)(1).\1\ States are also tasked
with monitoring visibility conditions and reporting progress to the
EPA, including tracking emissions reductions and visibility
improvements at Class I areas.\2\
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\1\ ``Congress hereby declares 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.''
\2\ See 40 CFR 51.308(f)(6).
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Throughout the implementation of the second planning period, we
received feedback from different stakeholder groups regarding the
unclear and resource intensive requirements of the Regional Haze
program. For example, some stakeholders (including various state air
agencies and regional planning organizations) commented that the
process of developing a Haze SIP revision is burdensome to both the
states and the EPA and that the EPA should provide regulatory clarity
regarding states' SIP revision obligations.\3\ In response to this
feedback, on March 12, 2025, the EPA announced that a priority would be
restructuring the Regional Haze program.\4\ Consistent with this
announcement, the EPA is reviewing its regulations implementing the
Regional Haze program to ensure the regulations fulfill Congressional
intent, are based on current scientific information, and reflect recent
improvements in air quality at the 156 Class I areas.\5\
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\3\ For example, see the following comments submitted to the
2024-nonregulatory docket (EPA-HQ-OAR-2023-0262) by SESARM/VISTAS,
the Alaska Department of Environmental Quality, CenSARA, Minnesota
Pollution Control Agency, and California Air Resources Board.
\4\ See <a href="https://www.epa.gov/newsreleases/epa-launches-biggest-deregulatory-action-us-history">https://www.epa.gov/newsreleases/epa-launches-biggest-deregulatory-action-us-history</a>.
\5\ See <a href="https://www.epa.gov/newsreleases/administrator-zeldin-begins-restructuring-regional-haze-program">https://www.epa.gov/newsreleases/administrator-zeldin-begins-restructuring-regional-haze-program</a>.
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D. What is the purpose of this ANPRM?
The EPA last revised the RHR in 2017 to clarify the relationship
between long-term strategies and reasonable progress goals (RPGs) in
SIPs and the long-term strategy obligation of all states; clarify and
modify the requirements for periodic comprehensive revisions of SIPs;
modify the set of days used to track progress towards natural
visibility conditions to account for events such as wildfires; provide
states with additional flexibility to account for impacts on visibility
from anthropogenic sources outside the United States (U.S.) and from
certain types of prescribed fires; modify certain requirements related
to the timing and form of progress reports; and update, simplify, and
extend to all states the provisions for reasonably attributable
visibility impairment, while revoking most existing reasonably
attributable visibility impairment Federal implementation plans
(FIPs).\6\ In the same action, the EPA also finalized an extension to
the due date for second planning period SIP revisions from 2018 to
2021.\7\ The EPA also proposed to extend the deadline for third
planning period SIP revisions from 2028 to 2031, but has not yet
finalized this proposal.\8\
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\6\ See ``Protection of Visibility: Amendments to Requirements
for State Plans''. 82 FR 3078 (January 10, 2017).
\7\ Id.
\8\ See 89 FR 104471 (December 23, 2024).
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The current RHR requirements governing the second planning period
are contained under 40 CFR 51.308(f), (g), (h), and (i). However, based
on SIP development and processing experiences during implementation of
the Regional Haze program's second planning period (2018 to 2028), the
EPA has identified a need to streamline and clarify the program's
requirements for the third planning period (2028 to 2038), and onward.
Further, commenters expressed concerns regarding what constitutes an
approvable SIP revision under the current RHR in the second and
subsequent planning periods.\9\
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\9\ See comments in EPA's non-regulatory docket (EPA-HQ-OAR-
2023-0262).
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Therefore, the EPA is now seeking comment and input in
restructuring existing regulations in a manner consistent with
applicable requirements in CAA sections 169A and 169B pertaining to the
protection of visibility at the 156 Class I areas addressed under the
Regional Haze program. The EPA has identified several topics that are
particularly relevant to the forthcoming RHR revisions and is
soliciting feedback on ways to streamline and clarify certain
requirements governing the Regional Haze program going forward. The EPA
is issuing this ANPRM as an efficient means for gaining the information
needed to inform EPA's decision-making, and to potentially aid in the
development of proposed revisions to the RHR. The EPA encourages the
public to participate in the regulatory process and provide specific
suggestions regarding potential regulatory changes. Following the
public comment period associated with this ANPRM, the Agency will move
forward with fundamentally revising the Regional Haze program.
E. Does this action apply to me?
Entities that may be interested in this ANPRM include state, local,
and Tribal governments, as well as Federal Land Managers (FLMs)
responsible for protection of visibility in mandatory Federal Class I
areas. This ANPRM may also be of interest to owners and operators of
sources that emit particulate matter equal to or less than 10 microns
in diameter (PM<INF>10</INF>), particulate matter equal to or less than
2.5 microns in diameter (PM<INF>2.5</INF> or fine PM), SO<INF>2</INF>,
NO<INF>X</INF>, volatile organic compounds (VOC), ammonia
(NH<INF>3</INF>), and other pollutants that may cause or contribute to
visibility impairment.
[[Page 47679]]
Others potentially interested in this ANPRM may include members of the
general public who live, work, or recreate near or in mandatory Class I
areas affected by visibility impairment. Additionally, members of the
general public may be interested in this ANPRM because emissions
sources that contribute to visibility impairment in Class I areas also
may contribute to air pollution in other areas.
III. What is the background for the EPA's proposed action?
A. Regional Haze
Regional haze is visibility impairment that is produced by a
multitude of sources and activities that are located across a broad
geographic area and directly emit PM<INF>10</INF>, PM<INF>2.5</INF>
(e.g., sulfates, nitrates, organic carbon, elemental carbon, and soil
dust) and/or their precursors (e.g., SO<INF>2</INF>, NO<INF>X</INF>,
and, in some cases, NH<INF>3</INF> and VOC). Fine particle precursors
react in the atmosphere to form PM<INF>2.5</INF>, which impairs
visibility by scattering and absorbing light. This light scattering and
absorbing reduces the clarity, color, and visible distance that one can
see. Particulate matter can also cause serious health effects in humans
and contribute to environmental effects such as acid deposition and
eutrophication.
B. Requirements for Regional Haze SIPs for the First Planning Period
Pursuant to a CAA directive to issue regulations, the EPA first
promulgated a rule to address regional haze in 1999, which established
the regulatory requirements for the first planning period Haze
SIPs.\10\ The 1999 RHR established a visibility protection program for
Class I areas consistent with CAA section 169A. The requirements for
the 1999 RHR and first planning period SIPs are found at 40 CFR
51.308(d) and (e), and 40 CFR 51.309. The initial Haze SIPs under the
1999 RHR were due to the EPA no later than December 17, 2007.\11\ Under
40 CFR 51.308(e), and the CAA, states were required to submit SIPs
evaluating the use of the best available retrofit technology (BART) at
certain larger, often uncontrolled, older stationary sources in order
to address visibility impairment from these sources.\12\ In addition to
the BART requirements, the 1999 RHR also required states under 40 CFR
51.308(d) to establish two distinct RPGs for the most impaired and
least impaired visibility days for each Class I area and a long-term
strategy for making progress towards achieving the national visibility
goal.
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\10\ See 64 FR 35714 (July 1, 1999).
\11\ See 70 FR 39104 (July 6, 2005).
\12\ The set of ``major stationary sources'' potentially
subject-to-BART is listed in CAA section 169A(g)(7).
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Since the RHR was finalized in 1999, Class I areas in all regions
of the contiguous U.S. have experienced measurable improvements in
visibility impairment.<SUP>13 14</SUP> Over the 2000-2019 period, there
was an observed improvement in regional average visibility impairment
at Class I areas, ranging from 0.5%/year to as much as 2.5%/year.\15\
These visibility improvements were greatest in the eastern U.S., driven
by strong decreases in sulfate impairment.
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\13\ The observed improvement was smaller in the Class I areas
in Alaska and Hawaii, with an observed increase in visibility
impairment in the Virgin Islands.
\14\ See 64 FR 35714 (July 1, 1999).
\15\ See Figure 7.9.5, IMPROVE Spatial and Seasonal Patterns and
Temporal Variability of Haze and Its Constituents in the United
States, Report VI, 2023.
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C. Requirements for Regional Haze SIPs for the Second Planning Period
In 2017, the EPA revised the Regional Haze Rule (2017 RHR) to
clarify states' obligations and streamline certain Regional Haze
requirements for the second planning period.\16\ Whereas the 1999 RHR
set the requirements for the first planning period, the 2017 RHR rule
revisions contained requirements for the second planning period (and
onward) relating to the requirement for SIPs to contain long-term
strategies for making reasonable progress towards the national
visibility goal. The requirements for the 2017 RHR are codified at 40
CFR 51.308(f), (g), (h), and (i). Among other changes, the 2017 RHR
adjusted the deadline for states to submit their second planning period
SIPs, clarified the order of analysis and the relationship between the
RPGs and the long-term strategy, and focused on making visibility
improvements on the days with the most manmade (or anthropogenic)
visibility impairment, as opposed to the days with the most visibility
impairment overall. In 2017, the EPA also revised requirements related
to periodic progress reports and FLM consultation.
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\16\ See 82 FR 3078 (January 10, 2017).
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Currently, 40 CFR 51.308(f) requires states to submit periodic
comprehensive revisions of implementation plans (referred to in this
document as periodic comprehensive SIP revisions) addressing regional
haze visibility impairment by no later than July 31, 2021, July 31,
2028, and every 10 years thereafter. All 50 states, the District of
Columbia, and the U.S. Virgin Islands are required to submit SIPs
satisfying the applicable requirements of the 2017 RHR. Each 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. To this
end, 40 CFR 51.308(f) lays out the process by which states determine
what constitutes their long-term strategies, with the requirements in
40 CFR 51.308(f)(1) through (3) establishing the process for evaluating
previous and current visibility conditions at Class I areas, the
development of a state's long-term strategy, and the establishment of
Class I areas' RPGs.\17\ Additionally, related requirements for SIP
development are located at 40 CFR 51.308(f)(4) through (6). In addition
to satisfying the requirements at 40 CFR 51.308(f) related to
reasonable progress, SIP revisions must address the requirements in 40
CFR 51.308(g)(1) through (5) pertaining to periodic reports describing
progress towards the RPGs, as well as requirements for FLM consultation
in 40 CFR 51.308(i) that apply to all visibility protection SIPs and
SIP revisions.
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\17\ We note that RPGs are a regulatory construct that the EPA
developed to address the statutory mandate in CAA section
169B(e)(1), which required our regulations to include ``criteria for
measuring `reasonable progress' toward the national goal.'' The RPGs
are different than the statutory requirement under CAA section
169A(a)(4) to make reasonable progress towards the national
visibility goal under CAA section 169A(a)(1). In the current
regulatory construct, RPGs measure the progress that is projected to
be achieved by the control measures a state has determined are
necessary to make reasonable progress. 40 CFR 51.308(f)(3)(ii).
However, consistent with both the 1999 RHR and 2017 RHR, the RPGs
are unenforceable, though they create a benchmark that allows for
analytical comparisons to the uniform rate of progress (URP) and
mid-implementation-period course corrections if necessary. 82 FR
3078, 3091-3092 (January 10, 2017).
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For additional background on the EPA's Regional Haze program and
the 2017 RHR revisions, please refer to Section III: Overview of
Visibility Protection Statutory Authority, Regulation, and
Implementation of ``Protection of Visibility: Amendments to
Requirements for State Plans'' of the 2017 RHR.\18\
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\18\ See <a href="https://www.federalregister.gov/d/2017-00268/p-94">https://www.federalregister.gov/d/2017-00268/p-94</a>.
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D. EPA's 2024 Non-Regulatory Docket
In Spring 2024, the EPA opened a non-regulatory docket (EPA-HQ-OAR-
2023-0262-0001) to solicit feedback on a specific list of topics
related to how the EPA could improve the implementation of the RHR in
potential future rule revisions. The docket was open for public comment
from March 28, 2024, to December 31, 2024, and the
[[Page 47680]]
EPA received 34 comments. Copies of the comments received and the EPA's
webinar presentation materials (docket ID: EPA-HQ-OAR-2023-0262-0002)
are available at <a href="http://regulations.gov">regulations.gov</a>.
In preparing this ANPRM, the EPA reviewed the feedback received on
the 2024 non-regulatory docket as well as comments received on
individual second planning period SIP actions. In reviewing this
feedback, the EPA observed concerns with the trajectory of the Regional
Haze program, implementation difficulties with the program, and
suggestions for changes to the current regulatory structure of the
program. With this information, the EPA developed a set of updated
questions regarding potential revisions to the regulatory framework of
the Regional Haze program. Specifically, the EPA is issuing this ANPRM
to solicit input on more specific and larger scale restructuring
concepts that are intended to respond to the feedback received in the
past several years.
A key goal of the forthcoming RHR revisions is to ensure clarity
regarding what is needed to develop a fully approvable Regional Haze
SIP revision, consistent with CAA requirements. The EPA is issuing this
ANPRM with the intent of ensuring that any potential revisions align
with the statutory goal of ensuring reasonable progress towards natural
visibility conditions, while also providing the public the opportunity
to submit additional ideas and reactions to the EPA in advance of our
forthcoming rulemaking.
IV. Request for Comments and Feedback
A. Overview and Introduction
The EPA is requesting feedback on a restructuring of the Regional
Haze program. To help guide feedback, the EPA is including background
and an overview of priority topics in this ANPRM, including questions
relating to how key aspects of the program could be implemented in
future planning periods. Notably, the questions the EPA is
highlighting, as well as the corresponding example solutions, do not
represent the full universe of topics that could be addressed in a
future rulemaking. Further, these questions should not be perceived as
identifying the EPA's position on a given topic. Rather, they are
intended to help reviewers consider different or new approaches for the
Regional Haze program. To that end, this ANPRM focuses on three key
topic areas that would serve to outline how the EPA might restructure
the Regional Haze program. These topic areas are: (1) development/use
of a reasonable progress metrics and consideration of the four
statutory reasonable progress factors in CAA section 169A(g)(1), (2)
development of SIP obligation criteria (i.e., criteria used to
determine when a SIP revision is required), and (3) determining SIP
requirements for states that are required to submit a SIP revision.
In identifying these key topic areas, the EPA observes that a
restructuring of the program would likely necessarily address these
topic areas, which are foundational parts of the current Regional Haze
program. The EPA observes that a program informed by current visibility
conditions at Class I areas in determining when SIP revisions are
required, as well as the content that SIP revisions must include, is
aligned with at least some of the feedback received by the public. For
example, rather than requiring every state (and territory) to submit a
SIP every planning period, a targeted, data-driven approach that
determines when SIP revisions are appropriate could be a way to manage
the program moving forward in light of the progress to date in
improving visibility conditions at the 156 Class I areas addressed
under the Regional Haze program. The topic areas, questions, and
concepts identified in this ANPRM are intended to support consideration
of a programmatic restructuring based on a fundamental concept of a
program that is data driven and recognizes both the current status of
remaining visibility impairment at mandatory Class I areas and the
measured improvement in visibility over the past 25 years of
implementing the Regional Haze program.
Feedback on the Regional Haze program need not be limited to the
material covered in this ANPRM and the three key topic areas. The EPA
has provided an initial set of questions and issues to facilitate
feedback. However, input is welcome on all aspects of the Regional Haze
program and applicable requirements under the CAA. The EPA encourages
reviewers and commenters to think broadly in their feedback and not
limit feedback to specific requirements or aspects of the current 2017
RHR. In submitting comments in response to this ANPRM, the EPA
encourages commenters to provide specific suggestions on program
restructuring and revisions along with a legal rationale and policy
objective. The EPA requests that reviewers and commenters number their
responses, for example, if responding to Topic 1, Question 1.a., please
use the Topic and Question within a header before providing a response.
Finally, in providing feedback on the questions discussed below, the
EPA welcomes commenters, where relevant, to provide redline-strikeout
edits to the current regulatory text of 40 CFR 51.308(f), (g), (h), and
(i) demonstrating how the EPA might incorporate commenters' suggested
changes. Alternatively, where commenters foresee a need for new
regulatory text to incorporate revisions to the Regional Haze program,
commenters are encouraged to provide potential new regulatory text and
an explanation of how commenters would implement the described changes.
B. Topic 1: Development and Implementation of a Reasonable Progress
Metric and Consideration of the Four Statutory Factors
In the 2017 RHR, the EPA interpreted CAA section 169A(b)(2) to
require states to substantively evaluate and determine potential
emissions reductions by considering the four statutory factors in CAA
section 169A(g)(1) after a state identified and selected sources that
contribute to visibility impairment at Class I areas.<SUP>19 20</SUP>
The EPA received feedback in its 2024 non-regulatory docket that the
Agency should consider developing an objective and numerically-based
reasonable progress metric (frequently referred to as a ``safe harbor''
in the comments received) that informs which, if any, additional
measures may be necessary to make reasonable progress. Commenters also
suggested that the reasonable progress metric could potentially be used
to determine when a SIP revision is required. Comments to the 2024 non-
regulatory docket also suggested that so long as reasonable progress
towards the national goal continues to be made at Class I areas, states
should not need to develop a SIP submission assessing additional
measures that may be necessary to achieve reasonable progress.
Therefore, by utilizing the concept of a ``safe harbor'' the EPA could
develop an objective, numerical metric to inform how much progress a
Class I area must make towards the national goal at any specific point
in time. If the metric is met (visibility impairment is at or below the
numerical metric at a certain point in time), the Class I area would be
making reasonable progress towards the national goal.
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\19\ See 82 FR 3078, January 10, 2017.
\20\ CAA section 169A(g)(1) states ``in determining reasonable
progress there shall be taken into consideration the costs of
compliance, the time necessary for compliance, and the energy and
nonair quality environmental impacts of compliance, and the
remaining useful life of any existing source subject to such
requirements.''
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[[Page 47681]]
This approach would be aligned with the CAA's direction in section
169B(e)(1) to include ``criteria for measuring reasonable progress
towards the national goal.'' A reasonable progress metric would provide
an objective way to determine the progress of the program and provide
certainty to states regarding the amount of visibility improvement that
is needed to meet the requirements of the Regional Haze program at
specific points in time, and if/when further analysis of emissions
control measures is needed. To the extent such a metric is used as the
exclusive method for determining whether a Class I area is making
reasonable progress, the EPA anticipates a need to explain the
relationship between the metric and consideration of the four statutory
factors. The CAA does not specify how or when the four statutory
factors must be taken into consideration when evaluating the measures
necessary for reasonable progress.\21\ These criteria and/or metrics
would also establish a framework that specifies when additional
analysis is necessary to ensure that ``reasonable progress'' is being
made, thereby dictating which specific actions (such as selecting
sources for consideration of emissions control measures) a state must
take during each planning period.
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\21\ Id.
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The EPA is considering whether to propose revising the rule to
include a reasonable progress metric that would serve to identify when
reasonable progress is being made towards the national visibility goal
under CAA section 169A(a)(1). This concept would be aligned with
stakeholder feedback that any metric used in this program should be a
definitive metric that indicates if or when states have specific
obligations to consider additional measures as may be necessary to make
reasonable progress at one or more Class I areas. In order to explore
these concepts further, the EPA solicits additional feedback on this
idea. To assist in development of feedback, the EPA encourages
consideration of the following questions.
1. Are there alternative approaches through which the EPA and/or
states can meet the CAA section 169A(g)(1) requirement to consider the
four factors in determining reasonable progress? Currently, this is
achieved by requiring all states contributing to visibility impairment
at a Class I area to evaluate and determine the emissions reduction
measures that are necessary to make reasonable progress by considering
the four statutory factors on a set of sources or group of sources
identified at the state's discretion. Potential alternative approaches
may include:
a. The EPA could develop a reasonable progress metric, consistent
with CAA section 169B(e)(1), considering the four factors. If a Class I
area does not achieve reasonable progress with measures already in the
regulatory portion of the SIP for a particular time period, the rule
could establish a process by which states would conduct more detailed
analyses. These analyses would be consistent with CAA section
169A(g)(1) and would be used to identify additional controls or
demonstrate that no additional controls are reasonable. For examples of
what form the reasonable progress metric could take, please see
Question 2 of Topic 1.
i. How could the EPA take the four factors under CAA section
169A(g)(1) into account when developing a reasonable progress metric?
For example, the EPA could anticipate current measures to be considered
into the reasonable progress metric. Here, control measures already in
place may have been developed through requirements such as reasonable
available control technology (RACT), best available control technology
(BACT), or lowest achievable emissions rate (LAER), which have similar
considerations to those of the four statutory factors.
b. The EPA could develop a reasonable progress metric, consistent
with CAA section 169B(e)(1). If a Class I area does not achieve
reasonable progress with existing measures previously incorporated into
the SIP, states would need to further consider the four factors to
either identify necessary controls or demonstrate that the EPA
reasonable progress metric is too ambitious. For example, so long as
the applicable Class I area(s) continue to make reasonable progress
consistent with the metric, the EPA could determine that no additional
consideration of the four factors is necessary to make reasonable
progress at that specific point in time. In that case, states'
existing, previously incorporated SIP measures would be all that is
needed to make reasonable progress. In this format, the four factors
serve as a ``backstop'' to ensure the Regional Haze program
requirements are not overly burdensome or costly.
i. In this scenario, how must the EPA take the four factors under
CAA section 169A(g)(1) into account when developing a reasonable
progress metric?
c. Another potential approach could be for the EPA to complete a
more comprehensive analysis of the projected visibility impacts of
current measures, as well as potentially available additional measures,
at Class I areas. In this analysis, the EPA would consider the four
factors and identify potential available emissions reductions,
calculate a projection of emissions to a future year (i.e., project
emissions), and conduct photochemical modeling to assess expected
improvement in visibility impairment. The visibility improvements
projected from the future year modeling would become the reasonable
progress target that each Class I area must meet. Commenters are
welcome to suggest inputs for this potential approach.
2. What form could a reasonable progress metric take? The EPA
encourages commenters to provide feedback on how and when the four
statutory factors would be taken into account within a reasonable
progress metric, and who (e.g., the EPA, states) should complete the
analytical work needed to determine a reasonable progress metric for
each Class I area. Potential approaches include:
a. Keep the current approach (perhaps with some minor adjustments).
In this scenario, the currently defined 2017 RHR uniform rate of
progress (URP) framework would apply (with adjustments for
international anthropogenic and prescribed fires,\22\ but no change to
the currently calculated 2064 end date).\23\ Being at or below the URP
line indicates the reasonable progress requirement has been met, so
long as the state has adequately considered the four statutory factors
in developing its SIP submission. This scenario would rely on states to
perform the four factor analysis on a set of selected sources, much
like the second planning period analysis.\24\ If this approach were
retained, restructuring could focus in on other aspects of the rule
such as how a SIP is developed and when it is required.
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\22\ Any reasonable progress metric that relies on natural
conditions as an endpoint, and/or is adjusted for international
anthropogenic and prescribed fire contributions should use revised
estimates based on updated photochemical modeling or a combination
of photochemical modeling and observational data.
\23\ Note that the URP's 2064 end date does not represent the
end date of the Regional Haze program. Rather, it purely serves as
an end point for calculating a ``glidepath'' towards natural
conditions over a 60-year time frame.
\24\ See 90 FR 16478, April 18, 2025 and 90 FR 29737, July 7,
2025.
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b. Revise the technical considerations that were the basis of the
URP framework. Potential revisions could include, but are not limited
to, the following ideas (noting that some of these ideas are not
mutually exclusive).
[[Page 47682]]
i. The EPA could change the end date to a year other than 2064,
presumably a later year. This would change the reasonable progress
requirement for any particular year and provide a longer glidepath (and
changing the angle of the glidepath), with less progress needed over
time to stay below the metric.
ii. The EPA could recalculate the URP every planning period
(adjusting for international anthropogenic impairment and international
and U.S. prescribed fire), which would be intended to ensure continuous
visibility improvement based on current visibility conditions at Class
I areas at the end of a planning period. Such a regularly occurring
adjustment would ensure that progress is being made in each planning
period at each Class I area. More progress would be required (steeper
slope) for areas that are above the current URP, and less progress
(gentler slope) would be required for areas that are below the current
URP.
iii. Develop a completely new concept such as a percent improvement
per planning period metric that is not based on the current URP. In
this type of scenario, reasonable progress would be defined as
achieving ``X%'' of remaining visibility improvement (with adjusted
natural conditions or other end goal as the end point) per planning
period that could be based on a required fixed percent progress every
planning period, or photochemical modeling of future available
emissions reductions, or other technical analyses.
3. Should the EPA revise the rule to include a concept akin to a
``safe harbor'' and what methods should the EPA use to track visibility
conditions and determine reasonable progress? While stakeholders have
long requested a ``safe harbor'' concept, the EPA is now soliciting
specific information from the public on how CAA requirements can be
embedded in such considerations. In this scenario, it is possible that
the EPA's reasonable progress metric could serve as a regulatory ``safe
harbor'' to better inform when a SIP revision is necessary. However,
the EPA recognizes that data is needed to track visibility conditions
at Class I areas to inform any kind of regulatory ``safe harbor''
implemented under the RHR. Potential approaches to track visibility
conditions at Class I areas include:
a. Using the ambient data collected through the IMPROVE network.
i. How should the EPA balance the accuracy of ambient data, the
associated time delay in collecting the data, and the time it takes
between ambient data collection and the SIP revision development
process?
b. Modeled estimates of U.S. anthropogenic impairment, tracked over
time through periodic updated modeling.
c. A combination of ambient data and future projections, which is
the current method employed under the 2017 RHR.
4. Are there recommended alternative metrics to the 20% clearest
days and 20% most impaired days to track visibility impairment?
Potential alternative approaches include:
a. Annual average of ambient visibility impairment (rather than
only considering the most impaired and clearest days).
b. A different distribution of days (e.g., the middle quintile--
40th to 60th percentile--of deciviews).\25\
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\25\ A ``deciview'' is a unit of measurement for quantifying in
a standard manner human perceptions of visibility. The deciview
index is derived from calculated or measured light extinction, such
that uniform increments of the index correspond to uniform
incremental changes in perception across the entire range of
conditions, from pristine to very obscured.
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5. Should the EPA continue to track visibility impairment using
IMPROVE ambient data in deciviews? Potential alternative approaches to
track impairment include:
a. Only extinction values (e.g., inverse megameters).
b. Trends in anthropogenic emissions of visibility impairing
precursors.
C. Topic 2: Development of Criteria Used To Determine When a SIP
Revision Is Necessary
The EPA received feedback in the 2024 non-regulatory docket that
the effort states undertake in preparing a SIP should be commensurate
with visibility improvements to date, as well as the resulting
obligation for further visibility improvement, at impacted Class I
areas.\26\ Likewise, air agency and industry stakeholders indicated
that there may be situations where additional evaluation or
implementation of further emissions controls are not necessary where
Class I areas have made ``enough'' reasonable progress for the planning
period at issue or where Class I areas are dominated by natural sources
of visibility impairment (e.g., wildfires or biogenics).\27\ In this
scenario, stakeholders suggested that states should not be required to
submit a SIP revision if reasonable progress is being made for that
planning period. Implementation of such an approach would likely
require significant changes and restructuring of the Regional Haze
program. Concepts that would support such an approach are described
below along with a broad solicitation for comment on these and any
other concepts throughout this topic.
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\26\ See comments received in the EPA's 2024 non-regulatory
docket (EPA-HQ-OAR-2023-0262).
\27\ Id.
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For example, the EPA could develop SIP obligation criteria that,
when applied, would give states definitive information about whether or
not a SIP revision is required. Further, such criteria would also
inform the content of any SIP that might be required to be submitted.
More specifically, in order to function this way, these criteria would
need to identify Class I areas where sufficient visibility progress is
being made at that specific point in time.
For this analysis, criteria could include (but are not limited to)
consideration of a Class I area that is sufficiently ``close to''
natural visibility conditions and/or Class I areas that are below a
reasonable progress metric for a particular time period. Further, the
EPA could also identify states whose sources do not, or no longer,
meaningfully contribute to visibility impairment in Class I areas for
that point in time. With these two key technical pieces of information,
the rule structure could essentially inform that if a state's
contributions are so small as to not cause or contribute to visibility
impairment at one or more Class I areas, the state is relieved of its
obligations to conduct additional analysis of emissions control
measures and revise its SIP for a specific planning period or point in
time, so long as its current SIP-approved long-term strategy for
addressing anthropogenic impairment is sufficient. This approach would
also need to ensure that the statutory requirement for preventing
future visibility impairment is also addressed.
The EPA also recognizes that until Class I areas meet the national
goal under CAA section 169A(a)(1), some level of continued future
planning is necessary in order to make reasonable progress and comply
with the statute. Under CAA section 169A(a)(1), Congress established
the national goal of ``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.'' Notably,
this section of the CAA calls for ``remedying of any existing
impairment of visibility . . . which impairment results from manmade
air pollution.'' As visibility conditions at Class I areas continue to
improve from reductions in anthropogenic impairment and get ``close
to'' natural visibility conditions, the EPA observes that visibility
impairment could reach a level below which it is not practical or
feasible to further control. This could be viewed as a ``de minimis''
level of visibility
[[Page 47683]]
impairment. A revised RHR could recognize this reality (where it
exists) and seek to establish a ``preservation'' category for Class I
areas where the EPA would determine that because a Class I area was so
close to achieving natural conditions, additional measures would be
unlikely to result in practical or feasible reductions in visibility
impairing pollutants, including any perceptible improvement in
visibility conditions. Therefore, just as the reasonable progress
metric discussed in Topic 1 could identify when a Class I area has
achieved reasonable progress for a specific point in time, Topic 2's
``preservation'' category could be used to identify Class I areas where
anthropogenic visibility impairment is sufficiently minimal, suggesting
that these areas have effectively achieved the national goal of the
Regional Haze program, as outlined in CAA section 169A(a)(1). The 2017
RHR does not account for this, and thus this portion of the ANPRM is
intended to solicit comment and identify potential approaches to
address this fact.
For example, the EPA could establish a ``preservation'' category of
Class I areas that are at or near achieving the national visibility
goal. In the BART Guidelines, the EPA has generally identified a one
deciview change as a small but noticeable change in visibility
impairment.\28\ Additionally, for the purpose of identifying BART-
eligible sources that caused or contributed to any impairment of
visibility in a Class I area, the BART Guidelines identified 0.5
deciviews as a contribution to visibility impairment and one deciview
as causing visibility impairment.\29\ Potentially informed by those
concepts, the EPA could identify criteria based on deciview differences
from natural conditions for when a Class I area could be in a
``preservation'' status. If a Class I area were to be placed into
``preservation'' status, nothing more would be needed to address
impairment at that Class I area for an identified time period and/or
planning period. However, this would not mean that the Regional Haze
requirements have been fully met into perpetuity or that the respective
Class I area(s) have reached natural conditions. At present, there are
numerous remaining sources of anthropogenic emissions that contribute
to visibility impairment, and such emissions may increase or change in
scope over time. Therefore, this approach would still require a
periodic evaluation of some sort (even if no SIP revision is ultimately
required). The CAA also does not require the national goal (as
articulated under CAA section 169A(a)(1)) to be achieved by a certain
date.\30\ Therefore, ``preservation'' status for a Class I area could
be considered as a temporary status (for the current planning period or
point in time), and the EPA (and/or the state) would continue to track
emissions and ambient data to ensure visibility has not degraded at
those Class I areas. Under this concept, the EPA would specify options
for remedying an increase in anthropogenic impairment if visibility
were to degrade. Such options might include the trigger for a SIP
revision, and/or parameters for the EPA to consider exercising its SIP
call authority, under CAA section 110(k)(5), for certain states to
evaluate emissions reduction measures through consideration of the four
statutory factors.
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\28\ See 64 FR 35725-35727, July 1, 1999.
\29\ See 70 FR 39104, July 6, 2005.
\30\ See CAA section 169A(f), which states: ``. . . the meeting
of the national goal specified in subsection (a)(1) of this section
by any specific date or dates shall not be considered a
`nondiscretionary duty' of the Administrator.''
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Notably, the EPA does not intend for the potential establishment of
a ``preservation'' category to affect the determination that visibility
is an important value at the Class I area(s). Rather, it would serve as
a regulatory tool for the EPA and states to track visibility
improvement towards the national visibility goal and ensure states' SIP
obligations reflect current visibility conditions at Class I areas. The
statutory and regulatory Regional Haze requirements would remain for
any state that may reasonably be anticipated to cause or contribute to
any visibility impairment at any Class I area.
This topic identifies potential new regulatory approaches and
associated criteria that may be applied to determine which mandatory
Class I areas are currently making ``sufficient reasonable progress''
and/or are ``close to'' achieving natural conditions such that
consideration of further emissions measures would not be necessary
during a specific planning period or at a given point in time. To
inform the EPA's decision on this issue, the EPA solicits feedback on
the following questions:
6. Does the national visibility goal articulated under CAA section
169A(a)(1) \31\ require Class I areas to be at natural visibility
conditions (i.e., elimination of all U.S. anthropogenic visibility
impairment) or does the goal refer to something less stringent than
natural visibility conditions (e.g., achieving a level of impairment
that is consistent with no perceptible U.S. anthropogenic impairment)?
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\31\ ``Congress hereby declares 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.''
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7. The national goal articulated under CAA section 169A(a)(1)
requires both ``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.'' Congress adopted
the visibility program in CAA section 169A to address existing
visibility impairment and the Prevention of Significant Deterioration
(PSD) program (CAA section 165) was intended to address (among other
things) the prevention of future visibility impairment.\32\
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\32\ The 1977 House Conference Report states: ``A major concern
which prompted the House to adopt the visibility protection
provision was the need to remedy existing pollution in Federal
mandatory class I areas from existing sources. Issues with respect
to visibility as an air quality value in application to new sources
are to be resolved within the procedures for prevention of
significant deterioration.'' See Legislative History of the Clean
Air Act Amendments of 1977 Public Law 95-95 91 Stat. 685 (1977).
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a. What is necessary to address future anthropogenic visibility
impairment? For example, is the PSD program sufficient to address the
prevention of any future anthropogenic visibility impairment?
8. Should the EPA develop a numerical threshold to identify when
Class I areas have achieved the national visibility goal? Potential
approaches include but are not limited to:
a. Total estimated anthropogenic impairment of 0 deciviews (ambient
data and/or model-based).
b. Total estimated anthropogenic impairment of 1 deciview or some
other indicator of perceptible impairment (ambient data and/or model-
based).
c. Estimated U.S. anthropogenic impairment of 0 deciviews (model-
based).
d. Estimated U.S. anthropogenic impairment of <less than 1 deciview
or some other indicator of perceptible impairment (model-based).
9. What types of criteria could the EPA describe to identify Class
I areas where sufficient visibility progress is being made during a
planning period such that states contributing to those areas would not
have any SIP revision, or substantive SIP revision obligations related
to those Class I areas (i.e., not account for those areas in their SIP
demonstration for that specific point in time)? Potential approaches
include:
a. The EPA could determine that a Class I area is achieving
reasonable progress based on reasonable progress
[[Page 47684]]
metric discussed under Topic 1 of this ANPRM.
i. Compare recent ambient data or projected visibility to an
identified reasonable progress metric to determine if criteria apply to
that Class I area.
b. The EPA could develop a ``preservation'' category that would be
defined as a Class I area being at or near natural visibility
conditions.
ii. In establishing a ``preservation'' category, the EPA could
compare recent ambient data or projected visibility data to estimated
(adjusted) natural conditions to determine if the identified criteria
apply to that Class I area. The EPA could strictly compare or establish
a threshold that defines ``close to'' natural conditions.
c. The EPA could determine that states with ``very small''
anthropogenic contributions to any Class I areas meet the statutory and
regulatory Regional Haze requirements and no new SIP revision would be
required unless visibility in those Class I areas degrades or is
projected to degrade.
iii. This would require the EPA to establish a de minimis
contribution threshold. Considering the statutory language in CAA
section 169A(b)(2), which states ``the emissions from which may
reasonably be anticipated to cause or contribute to any impairment of
visibility in any such area,'' how might the EPA establish and justify
a threshold for emissions that cause or contribute to ``any''
visibility impairment at one or more Class I areas?
iv. In developing such an approach, are there lessons learned from
other programmatic areas of the CAA where thresholds are used to
identify SIP requirements (e.g., PSD, interstate transport and national
ambient air quality standards (NAAQS) planning, etc.)? The EPA solicits
comments on the functionality of such approaches and implementation
experiences associated with those programs and ways in which such
programs might inform a similar style program in the Regional Haze
context.
10. What technical analyses and data are needed to inform
implementation of potential criteria; who is responsible for developing
and analyzing such data; and can commenters identify updated available
information from literature and/or recent studies? Potential
approaches:
a. Updated estimates of natural conditions and international/
prescribed fire adjustments.
b. Ambient data and/or photochemical modeling of visibility
impairment at Class I areas.
c. Reduced form tools based on photochemical modeling, similar to
those the EPA has developed for other CAA programs, such as PSD
permitting.\33\
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\33\ For an example of the methodologies behind reduced form
tools, please see the Modeled Emission Rates Precursors (MERPs)
Guidance: <a href="https://www.epa.gov/nsr/guidance-development-modeled-emission-rates-precursors-merps-tier-1-demonstration-tool-ozone">https://www.epa.gov/nsr/guidance-development-modeled-emission-rates-precursors-merps-tier-1-demonstration-tool-ozone</a>.
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11. The EPA observes significant differences across the U.S. in
visibility improvement made since the baseline period (2000-2004) and
in existing impairment. For example, while the eastern states have made
considerable progress towards reducing visibility impairing pollutants,
Class I areas in the Eastern U.S. generally remain more impaired than
western Class I areas. Given the significant difference in visibility
conditions and progress across Class I areas (e.g., East versus West),
how can the EPA ensure reasonable progress is being made at all Class I
areas?
D. Topic 3: Determining SIP Content Requirements
The EPA anticipates that even with a significant restructuring of
the Regional Haze program some states (now and/or in the future) would
still be required to submit a full Haze SIP revision. Many air agency
comments to the 2024 non-regulatory docket expressed frustration with
the workload necessary to achieve a fully approvable Haze SIP revision,
as well as concerns with the lack of clarity associated with the 2017
RHR's regulatory and administrative requirements.\34\ Therefore, where
the EPA determines a SIP revision to address visibility impairment at
one or more Class I areas is necessary, the EPA recognizes a need to
revise the Regional Haze program to ensure states have a clear
understanding and pathway for achieving a fully approvable Haze SIP
revision.
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\34\ See comments in EPA's 2024 non-regulatory docket (EPA-HQ-
OAR-2023-0262).
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In response, the EPA is soliciting more targeted feedback to
identify specific revisions that would serve to streamline the
perceived or actual SIP development burdens on states when a SIP
revision is required. To inform the EPA's decision on what regulatory
changes would best support states when preparing a fully approvable
Haze SIP revision, the EPA requests feedback on the following
questions:
12. Should the EPA maintain the current approach under 40 CFR
51.308(f) to have ``planning periods'' every 10 years? Potential
alternative approaches include:
a. Extend the 10-year planning periods to 15-year planning periods.
CAA section 169A(b)(2)(B) states that all states must submit a SIP
containing a 10-to-15-year long strategy for making reasonable progress
towards the national goal articulated under CAA section 169A(a)(1).
Under the 1999 and 2017 RHRs, the EPA has established that states must
submit periodic comprehensive SIP revisions containing a 10-year long-
term strategy for addressing anthropogenic impairment over the course
of successive 10-year planning periods.\35\ However, the RHR could be
revised so that planning periods occur in 15-year increments, as
permitted by the statute. Under this scenario, states' long-term
strategies would cover the 15-year period leading up to the next SIP
revision compliance deadline for the next planning period.
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\35\ See 82 FR 3078, January 10, 2017.
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b. Shift to requiring SIP revisions on an ``as needed'' basis. As
mentioned under the previous bullet (1a), CAA section 169A(b)(2)(B)
calls for states to submit a SIP containing ``a long-term (ten to
fifteen years) strategy for making reasonable progress toward meeting
the national goal.'' Furthermore, CAA section 169A(b)(2) requires each
implementation plan ``to contain such emission limits, schedules of
compliance, other measures as may be necessary to make reasonable
progress toward meeting the national goal.'' If the measures
incorporated into the states' long-term strategy continue to make
reasonable progress towards the national goal, states would not be
required to submit a SIP revision. Instead, states would be required to
update their long-term strategies when sufficient reasonable progress
is not being made towards the national goal, thereby fulfilling
Congress's mandate for long-term strategies to contain ``the measures
as may be necessary'' to achieve the national goal and potentially
fulfill the statutory requirement to have a 10-to-15-year long-term
strategy under CAA section 169A(b)(2)(B). In this approach, and if the
EPA were to implement one or more of the metrics and criteria discussed
under Topics 1 and 2 to determine when Haze SIP revisions are
necessary, the EPA could issue a SIP call informed by the EPA's current
understanding of visibility conditions at the 156 Class I areas. The
RHR could also be revised to include a mechanism for the EPA to
periodically report on visibility conditions at Class I areas to inform
this decision, consistent with CAA section 169B(b).
13. The 2017 RHR allows states to include the impacts of other CAA
regulatory programs when developing
[[Page 47685]]
their Regional Haze SIPs (e.g., NAAQS implementation). However, there
is some ambiguity to what extent states must make these other CAA
regulatory programs federally enforceable within the Regional Haze SIP
(i.e., the long-term strategy for Regional Haze). Therefore, how or
when should states consider and/or rely upon emissions reductions from
other CAA regulatory programs for Regional Haze purposes?
14. To what extent should states be required to incorporate
sources' current emissions measures into their Regional Haze SIP
revisions, consistent with the requirements of CAA section 169A(b)(2),
in order to obtain ``credit'' for such reductions as part of their
Regional Haze SIP and reasonable progress requirements?
a. What are potential pathways for making existing measures (e.g.,
permit limitations, statewide emissions management strategies, source-
specific consent agreements) federally enforceable in a SIP such that
they can be relied upon for the reasonable progress determination under
the Regional Haze program?
15. The purpose of the Regional Haze program, as outlined in CAA
section 169A(a)(1), is to remedy any existing and prevent any future
visibility impairment. How should visibility be considered as a
regulatory factor to ensure Regional Haze SIP revisions are evaluated
based on visibility improvement at Class I areas?
16. What would the benefits or drawbacks from removing states'
requirements under the 2017 RHR to submit a 5-year progress report
between SIP revision submittals under 40 CFR 51.308(g)?
17. In what way should the EPA consider revising the Reasonably
Attributable Visibility Impairment (RAVI) provisions under 40 CFR
51.302 to ensure CAA objectives are met? Examples of potential
revisions are:
a. Removing the RAVI provisions entirely from the RHR at 40 CFR
51.302, 40 CFR 51.304, and 40 CFR 51.305.
b. Restructuring RAVI by revising the process of FLMs certifying a
RAVI for a source (or sources), and what happens after a RAVI is
identified.
18. The EPA has observed in its implementation of the second
planning period that there is disagreement between states and FLMs on
the implementation of FLM consultation requirements. The CAA provides
for consultation with FLMs (see CAA section 169A(d)). The EPA also
recognizes the unique and important role served by the FLMs as it
pertains to mandatory Class I areas. The EPA solicits feedback on
specific revisions to FLM consultation provisions in 40 CFR 51.308(i),
consistent with the CAA, that ensures adequate FLM consultation but
does not unnecessarily delay or cause undue burden on states and others
engaged in the Regional Haze process. For example, in some instances,
the EPA observed that FLMs received portions of draft SIPs prior to a
public comment period on a SIP submittal at the state level. In other
instances, there were disagreements about whether the ``consultation''
met the statutory and regulatory requirements.
a. The EPA solicits specific feedback regarding the level of
consultation and materials that are needed to fulfill the statutory
obligations under CAA section 169A(d). Similarly, the EPA solicits
feedback regarding challenges states faced in submitting materials to
FLMs to fulfill the consultation requirements. Examples of feedback the
EPA would find most helpful include, but are not limited to:
i. In order to meet the statutory ``consultation'' requirements,
which SIP materials/content, if any, must be offered to the FLMs during
their opportunity for consultation?
ii. How can the EPA establish regulatory guidelines to clarify when
a Haze SIP revision must undergo FLM consultation? For example, does a
Haze SIP revision that addressed minor edits (e.g., spelling or
citation correction or revisions that are administrative in nature that
do not modify SIP requirements) need to undergo FLM consultation? Or is
FLM consultation only required when a state is proposing to
substantively revise its long-term strategy or underlying analysis?
b. The 2017 RHR requires states to provide FLMs a minimum of 60
days to review Haze SIPs.\36\ How much time should states need to
provide the FLMs during the opportunity for consultation?
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\36\ See 40 CFR 51.308(i)(2).
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c. How far in advance of the state public comment process should
FLM consultation occur?
19. The 2017 RHR currently includes an interstate consultation
process; however, the CAA itself does not mandate such a
consultation.\37\ Throughout implementation of the program, the EPA
observes that this provision brought states together to discuss
impairment at Class I areas in ways that all parties could find
beneficial. However, the interstate consultation process requires
states to allocate additional resources and extend the SIP development
timeline in a way that may not always result in a productive
consultation. Given this context, the EPA solicits feedback regarding
how the EPA could revise or clarify the interstate consultation process
(40 CFR 51.308(f)(2)(ii)) states must undergo before submitting a SIP
revision to the EPA.
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\37\ See 40 CFR 51.308(f)(2)(ii).
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a. Furthermore, what role should the regional planning
organizations play in interstate consultation and overall SIP
development?
V. Request for Comment and Additional Information
The EPA is seeking comment on all questions and topics described in
this ANPRM and welcomes submission of any other information, including
information which may not be specifically mentioned in this document.
The EPA requests that commenters make specific recommendations and
include supporting documentation where appropriate. In addition, the
EPA is seeking comment on how the agency could consider the valuation
of potential benefits from reducing regional haze. Please identify any
relevant peer reviewed studies and the appropriateness of applying
those studies within the context of potential regional haze regulatory
changes. Instructions for providing written comments are provided under
ADDRESSES, including how to submit any comments that contain CBI.
VI. What are the next steps EPA will take?
The EPA intends to use the information submitted in response to
this ANPRM to inform a forthcoming proposed rulemaking to revise the
RHR.
VII. Statutory and Executive Orders Reviews
Under Executive Order 12866, entitled Regulatory Planning and
Review (58 FR 51735, October 4, 1993), this is a ``significant
regulatory action''. Accordingly, the EPA submitted this action to the
Office of Management and Budget (OMB) for review under Executive Order
12866 and any changes made in response to Executive Order 12866 review
have been documented in the docket for this action. Because this action
does not propose or impose any requirements, other statutory and
executive order reviews that apply to rulemaking do not apply. Should
the EPA subsequently determine to pursue a rulemaking, the EPA will
address the statutes and executive orders as applicable to that
rulemaking.
Additional information about statutes and executive orders can be
found at <a href="https://www.epa.gov/laws-regulations/laws-and-executive-orders">https://www.epa.gov/laws-regulations/laws-and-executive-orders</a>.
[[Page 47686]]
List of Subjects in 40 CFR Part 51
Environmental protection, Administrative practice and procedure,
Air pollution control, Nitrogen dioxide, Particulate matter, Sulfur
oxides, Transportation, Volatile organic compounds.
Lee Zeldin,
Administrator.
[FR Doc. 2025-19280 Filed 10-1-25; 8:45 am]
BILLING CODE 6560-50-P
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</html>Indexed from Federal Register on October 2, 2025.
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