[Federal Register Volume 89, Number 128 (Wednesday, July 3, 2024)]
[Proposed Rules]
[Pages 55140-55168]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-14612]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R07-OAR-2024-0286; FRL-12046-01-R7]


Air Plan Partial Approval and Partial Disapproval; Missouri; 
Regional Haze

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 a revision to Missouri's 
State Implementation Plan (SIP) submitted on August 26, 2022, to 
satisfy applicable requirements under the Clean Air Act (CAA) and the 
EPA's Regional Haze Rule (RHR) for the program's second planning 
period. As required by section 169A of the Clean Air Act, the Federal 
Regional Haze Rule calls for state and Federal agencies to work 
together to improve visibility, including Regional Haze, in 156 
national parks and wilderness areas. The rule requires the states, in 
coordination with the EPA, the National Parks Service (NPS), the U.S. 
Fish and Wildlife Service (FWS), the U.S. Forest Service (FS), and 
other interested parties, to develop and implement air quality 
protection plans in which states revise their long-term strategies 
(LTS) for making reasonable progress towards the national goal of 
preventing any future, and remedying any existing, anthropogenic 
impairment of visibility in these mandatory Class I Federal areas. 
Disapproval does not start a mandatory sanctions clock.

DATES: Comments must be received on or before August 2, 2024.

ADDRESSES: You may send comments, identified by Docket ID No. EPA-R07-
OAR-2024-0286 to https://www.regulations.gov. Follow the online 
instructions for submitting comments.
    Instructions: All submissions received must include the Docket ID 
No. for this rulemaking. Comments received will be posted without 
change to https://www.regulations.gov/, including any personal 
information provided. For detailed instructions on sending comments and 
additional information on the rulemaking process, see the ``Written 
Comments'' heading of the SUPPLEMENTARY INFORMATION section of this 
preamble.

FOR FURTHER INFORMATION CONTACT: Ashley Keas, Environmental Protection 
Agency, Region 7 Office, Air and Radiation Division, 11201 Renner 
Boulevard, Lenexa, Kansas 66219; telephone number: (913) 551-7629; 
email address: [email protected].

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

Table of Contents

I. Written Comments
II. What is being addressed in this document?
III. Background and Requirements for Regional Haze Plans
    A. Regional Haze Background
    B. Roles of Agencies in Addressing Regional Haze
IV. Requirements for Regional Haze Plans for the Second 
Implementation Period
    A. Identification of Class I Areas
    B. Calculation 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
V. The EPA's Evaluation of Missouri's Regional Haze Submission for 
the Second Implementation Period
    A. Background on Missouri's First Implementation Period SIP 
Submission
    B. Missouri's Second Implementation Period SIP Submission and 
the EPA's Evaluation
    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. Source Selection
    2. Four-Factor Analysis
    3. Additional Long-Term Strategy Requirements
    F. Reasonable Progress Goals
    G. Monitoring Strategy and Other Implementation Plan 
Requirements
    H. Requirements for Periodic Reports Describing Progress Towards 
the Reasonable Progress Goals
    I. Requirements for State and Federal Land Manager Coordination
VI. What action is the EPA proposing to take?
VII. Environmental Justice Considerations
VIII. Statutory and Executive Order Reviews

I. Written Comments

    Submit your comments, identified by Docket ID No. EPA-R07-OAR-2024-
0286, at https://www.regulations.gov. 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, 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.

II. What is being addressed in this document?

    On August 26, 2022, the Missouri Department of Natural Resources 
(MoDNR) submitted a plan to the EPA to satisfy the regional haze 
program requirements pursuant to CAA sections 169A and 40 CFR 51.308. 
The EPA is proposing to partially approve and partially disapprove 
Missouri's Regional Haze plan for the second planning period. 
Consistent with section 110(k)(3) of the CAA, the EPA may partially 
approve portions of a submittal

[[Page 55141]]

if those elements meet all applicable requirements and may disapprove 
the remainder so long as the elements are fully separable.\1\ As 
required by section 169A of the CAA, the Federal RHR calls for state 
and Federal agencies to work together to improve visibility in 156 
national parks and wilderness areas. The rule requires the states, in 
coordination with the EPA, NPS, FWS, FS, and other interested parties, 
to develop and implement air quality protection plans to reduce the 
pollution that causes visibility impairment. 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)). As discussed in further detail 
below, the EPA is proposing to find that Missouri has submitted a 
Regional Haze plan that does not meet all the Regional Haze 
requirements for the second planning period. For the reasons described 
in this document, the EPA is proposing to approve the elements of 
Missouri's plan related to requirements contained in 40 CFR 
51.308(f)(1), (f)(5), (f)(6), and (g)(1) through (g)(5). The EPA is 
proposing to disapprove the elements of Missouri's plan related to 
requirements contained in 40 CFR 51.308(f)(2), (f)(3), and (i). The 
State's submission can be found in the docket for this action.
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    \1\ See CAA section 110(k)(3) and July 1992 EPA memorandum 
titled ``Processing of State Implementation Plan (SIP) Submittals'' 
from John Calcagni, at https://www.epa.gov/sites/default/files/2015-07/documents/procsip.pdf.
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III. 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.\2\ CAA 
section 169A. 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.'' CAA section 169A(a)(1). The CAA further 
directs the EPA to promulgate regulations to assure reasonable progress 
toward meeting this national goal. CAA section 169A(a)(4). 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. (45 FR 80084, December 2, 1980). 
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. CAA section 169B. The EPA promulgated the RHR, codified at 40 CFR 
51.308,\3\ on July 1, 1999. (64 FR 35714, July 1, 1999). These Regional 
Haze regulations are a central component of the EPA's comprehensive 
visibility protection program for Class I Areas.
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    \2\ 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 
section 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.
    \3\ 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. The latter 
regulations are applicable only for specific jurisdictions' regional 
haze plans submitted no later than December 17, 2007, and thus are 
not relevant here.
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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 PM 
(e.g., sulfates, nitrates, organic carbon, elemental carbon, and soil 
dust) and their precursors (e.g., SO2, NOX, and, 
in some cases, VOC and NH3). Fine particle precursors react 
in the atmosphere to form fine particulate matter (PM2.5), 
which impairs visibility by scattering and absorbing light. Visibility 
impairment reduces the perception of clarity and color, as well as 
visible distance.\4\
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    \4\ 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 to 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 at 
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. CAA section 169A(b)(2); \5\ see also 40 CFR 
51.308(b), (f) (establishing submission dates for iterative Regional 
Haze SIP revisions); (64 FR 35714 at 35768, July 1, 1999). 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,'' CAA section 169A(b)(2)(B); 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). CAA section 
169A(b)(2)(A); 40 CFR 51.308(d), (e). States' first Regional Haze SIPs 
were due by December 17, 2007, 40 CFR 51.308(b), with subsequent SIP 
submissions containing updated long-term strategies originally due July 
31, 2018, and every ten years thereafter. (64 FR 35714 at 35768, July 
1, 1999). 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.\6\ Id. at 35721.
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    \5\ 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).
    \6\ 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

[[Page 55142]]

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. CAA section 169A(g)(1); 40 CFR 
51.308(d)(1).
    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 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.\7\ 40 CFR 
51.308(d)(1)(i)(B), (d)(2). 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.'' 40 CFR 51.308(d)(3). 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. 40 CFR 
51.308(d)(3)(i) and (ii). Section 51.308(d) also contains seven 
additional factors states must consider in formulating their long-term 
strategies, 40 CFR 51.308(d)(3)(v), as well as provisions governing 
monitoring and other implementation plan requirements. 40 CFR 
51.308(d)(4). Finally, the 1999 RHR required states to submit periodic 
progress reports--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, see 40 CFR 51.308(g), (h)--and to consult with the 
Federal Land Manager(s) \8\ (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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    \7\ 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 
start 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).
    \8\ 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, (82 
FR 3078, January 10, 2017), that apply for the second and subsequent 
implementation periods. 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 below.
    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'').\9\ 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'').\10\ 
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''),\11\ 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'').\12\
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    \9\ 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).
    \10\ 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).
    \11\ 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).
    \12\ 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 previously 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 
emission 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. See 
generally 2021 Clarifications Memo. This is consistent with Congress's 
determination that a visibility protection program is needed in 
addition to the CAA's National Ambient Air Quality Standards (NAAQS) 
and Prevention of Significant Deterioration (PSD) programs, as further 
emission reductions may be necessary to adequately protect visibility 
in Class I areas throughout the country.\13\
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    \13\ See, e.g., H.R. Rep No. 95-294 at 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. In order 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),\14\ 
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 PM and other pollutants 
leading to Regional Haze, and help states meet the consultation 
requirements of the RHR.
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    \14\ RPOs are sometimes also referred to as ``multi-
jurisdictional organizations,'' or MJOs. For the purposes of this 
document, the terms RPO and MJO are synonymous.
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    The Central Regional Air Planning association (CenRAP), one of the 
five RPOs mentioned above, that Missouri was a member of during the 
first planning period, was a collaborative effort of state governments, 
tribal governments, and Federal agencies established to initiate and 
coordinate activities associated with the management of Regional Haze, 
visibility, and other air quality issues in parts of the Great Plains, 
Midwest, Southwest, and South Regions of the United States.
    After the first planning period SIPs were submitted, the CenRAP was 
disbanded, and the relevant regulatory entities reorganized as the 
Central States Air Resources Agencies (CenSARA). CenSARA is a 
collaborative effort of state governments established to initiate and 
coordinate activities associated with the management of Regional Haze 
and other air quality issues in parts of the Great Plains, Midwest, 
Southwest, and South Regions of the United States. Member states 
include: Arkansas, Iowa, Missouri, Louisiana, Kansas, Missouri, 
Nebraska, Oklahoma, and Texas. Unlike CenRAP, CenSARA's voting members 
are only comprised of state agency representatives. However, CenSARA 
continues to include interested Tribal and Federal partners on 
communications and regular meetings. The Federal partners of CenSARA 
are the EPA, NPS, FWS, and FS.

IV. 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 are required to 
submit Regional Haze SIPs 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. CAA section 169A(b)(2)(B). To this end, Sec.  
51.308(f) lays out the process by which states determine what 
constitutes their long-term strategies, with the order of the 
requirements in Sec.  51.308(f)(1) through (f)(3) generally mirroring 
the order of the steps in the reasonable progress analysis \15\ and 
paragraphs (f)(4) through (f)(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. See 40 CFR 51.308(f) and (f)(2). 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. See 40 CFR 
51.308(f)(1). 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 emission 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 51.3108(f)(2)(iv) separately 
provides five ``additional factors'' \16\ that states must consider in 
developing their long-term strategies. See 40 CFR 51.308(f)(2). A state 
evaluates potential emission reduction measures for those selected 
sources and determines which are necessary to make reasonable progress 
using the four statutory factors. 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

[[Page 55144]]

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. 40 CFR 51.308(f)(2)-(3).
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    \15\ 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 40 CFR 51.308(d), ``tracked the actual planning 
sequence.'' (82 FR 3078 at 3091, January 10, 2017).
    \16\ 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.
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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 Sec.  
51.308(g)(1) through (5) pertaining to periodic reports describing 
progress towards the RPGs, 40 CFR 51.308(f)(5), as well as requirements 
for FLM consultation that apply to all visibility protection SIPs and 
SIP revisions. 40 CFR 51.308(i).
    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. See CAA section 
169(b)(2); CAA section 110(a). Upon EPA approval, a SIP is enforceable 
by the Agency and the public under the CAA. If the EPA finds that a 
state fails to make a required SIP revision, or if the EPA finds that a 
state's SIP is incomplete or if disapproves the SIP, the Agency must 
promulgate a Federal Implementation Plan (FIP) that satisfies the 
applicable requirements. CAA section 110(c)(1).

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, 64 FR 35714 at 35720 through 
35722, and explained that the statute and regulations lay out an 
``extremely low triggering threshold'' for determining ``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.'' Id. at 35721.
    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. 
2019 Guidance at 8-9. 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.''

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 Sec.  
51.308(f)(1) related to tracking visibility improvement over time. The 
requirements of this subsection apply only to states having 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 
\17\ provides recommendations to assist states in satisfying their 
obligations under Sec.  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. 
See 82 FR 3078 at 3103 through 3105, January 10, 2017.
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    \17\ The 2018 Visibility Tracking Guidance references and relies 
on parts of the 2003 Tracking Guidance: ``Guidance for Tracking 
Progress Under the RHR,'' which can be found at https://www3.epa.gov/ttnamti1/files/ambient/visible/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% clearest (the 20% 
of monitored days in a calendar year with the lowest values of the 
deciview index) and 20% most impaired days (the 20% of monitored days 
in a calendar year with the highest amounts of anthropogenic visibility 
impairment).\18\ 40 CFR 51.301. A state must calculate visibility 
conditions for both the 20% clearest and 20% 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). 40 CFR 51.308(f)(1)(i) and (iii). States must 
also calculate natural visibility conditions for the clearest and most 
impaired days,\19\ by estimating the conditions that would exist on 
those two sets of days absent anthropogenic visibility impairment. 40 
CFR 51.308(f)(1)(ii). 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 in order 
to reach natural visibility conditions.
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    \18\ This publication also refers to the 20% clearest and 20% 
most anthropogenically impaired days as the ``clearest'' and ``most 
impaired'' or ``most anthropogenically impaired'' days, 
respectively.
    \19\ 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 3078 
at 3098, January 10, 2017: ``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.''
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    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 in order 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.\20\ 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

[[Page 55145]]

not necessary for reasonable progress. 82 FR 3078 at 3107 footnote 116, 
January 10, 2017.
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    \20\ 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 3078 at 3093, January 10, 
2017.
---------------------------------------------------------------------------

    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 Sec.  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 
paragraphs (f)(2)(i) through (iv).'' 40 CFR 51.308(f)(2). 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 emission reduction measures that a 
particular source or group of sources needs to implement in order to 
make reasonable progress towards the national visibility goal. See 40 
CFR 51.308(f)(2)(i). Emission reduction measures that are necessary to 
make reasonable progress may be either new, additional control measures 
for a source, or they may be the existing emission reduction measures 
that a source is already implementing. See 2019 Guidance at 43; 2021 
Clarifications Memo at 8-10. 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. 40 CFR 51.308(f)(2).
    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 emission reduction measures; to this end, 
the RHR requires states to 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. 40 CFR 51.308(f)(2)(i). 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. See 2019 Guidance at 12, 2021 Clarifications Memo at 
4. A state that chooses not to consider at least these two pollutants 
should demonstrate why such consideration would be unreasonable. 2021 
Clarifications Memo at 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 RHR, 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.'' 2019 Guidance at 9. 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.'' 2021 Clarifications Memo at 
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. 2021 Clarifications Memo at 4.\21\
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    \21\ 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. Docket Document ID: EPA-HQ-OAR-2015-0531-0635 
at pages 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.\22\ This is accomplished by considering the Four Factors--``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.'' CAA section 169A(g)(1). The EPA has explained that the 
four-factor analysis is an assessment of potential emission 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 in order to 
satisfy the CAA's reasonable progress mandate.'' 82 FR 3078 at 3091, 
January 10, 2017. Thus, for each source it has selected for four-factor 
analysis,\23\ a state

[[Page 55146]]

must consider a ``meaningful set'' of technically feasible control 
options for reducing emissions of visibility impairing pollutants. Id. 
at 3088. 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.'' 2019 Guidance at 29.
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    \22\ The CAA provides that, ``[i]n determining reasonable 
progress there shall be taken into consideration'' the four 
statutory factors. CAA section 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 emission 
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.
    \23\ ``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 
3078 at 3088, January 10, 2017. 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 at 7-8.
---------------------------------------------------------------------------

    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.'' 2021 
Clarifications Memo at 7. In addition to add-on controls and other 
retrofits (i.e., new emission 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 emission rate than a source has achieved or could 
potentially achieve using its existing measures should also consider 
lower emission rates as potential control options. That is, a state 
should consider a source's recent actual and projected emission rates 
to determine if it could reasonably attain lower emission rates with 
its existing measures. If so, the state should analyze the lower 
emission rate as a control option for reducing emissions. 2021 
Clarifications Memo at 7. The EPA's recommendations to analyze 
potential efficiency improvements and achievable lower emission 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.'' See 2021 Clarifications Memo 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.\24\ 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. 
See 2019 Guidance at 30-36. 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. 2021 Clarifications Memo at 12-13, 14-15. 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. 2021 Clarifications Memo at 13. 
Ultimately, while states have discretion to reasonably weigh the 
factors and to determine what level of control is needed, Sec.  
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.''
---------------------------------------------------------------------------

    \24\ 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 at 36-37.
---------------------------------------------------------------------------

    As explained above, Sec.  51.308(f)(2)(i) requires states to 
determine the emission reduction measures for sources that are 
necessary to make reasonable progress by considering the Four Factors. 
Pursuant to Sec.  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.\25\ If the 
outcome of a four-factor analysis is a new, additional emission 
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 emission increases and thus to make 
reasonable progress towards the second part of the national visibility 
goal: preventing future anthropogenic visibility impairment. See CAA 
section 169A(a)(1). 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 emission rate, it may not 
be necessary to have those measures in the long-term strategy in order 
to prevent future emission 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. See 2021 
Clarifications Memo at 8-10. 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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    \25\ 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 at 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 3078 at 3108 and 3109, January 10, 2017 
(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).
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    As with source selection, the characterization of information on 
each of the factors is also subject to the documentation requirement in 
Sec.  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 emission 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, Sec.  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 emission reduction measures must be in place to make 
reasonable progress. The technical documentation must include the 
modeling, monitoring, cost, engineering,

[[Page 55147]]

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.\26\ That 
is, a state's decisions about the emission reduction measures that are 
necessary to make reasonable progress must be consistent with the 
statutory goal of remedying existing and preventing future visibility 
impairment.
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    \26\ 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 emission 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'' \27\ that states must consider in 
developing their long-term strategies: (1) emission reductions due 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. See 2019 
Guidance at 21. 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 emission 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. 2021 Clarifications Memo at 13.
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    \27\ 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.
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    Because the air pollution that causes Regional Haze crosses state 
boundaries, Sec.  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 emission 
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 emission limitation) are 
necessary to make reasonable progress at a Class I area, it must 
include those measures in its SIP. 40 CFR 51.308(f)(2)(ii)(A). 
Additionally, the RHR requires that states that contribute to 
visibility impairment at the same Class I area consider the emission 
reduction measures the other contributing states have identified as 
being necessary to make reasonable progress for their own sources. 40 
CFR 51.308(f)(2)(ii)(B). If a state has been asked to consider or adopt 
certain emission 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. 40 
CFR 51.308(f)(2)(ii)(C). 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. See id.; 2019 Guidance at 53. Under all circumstances, a 
state must document in its SIP submission all substantive consultations 
with other contributing states. 40 CFR 51.308(f)(2)(ii)(C).

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.'' 82 FR 3078 at 3091, January 10, 2017. 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. See 40 CFR 51.308(f)(3)(iii) and (iv). 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. 40 CFR 51.308(f)(3)(i). The 
two RPGs are intended to reflect the projected impacts, on the two sets 
of days, of the emission 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.\28\ 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. See 2021 Clarifications Memo at 6.
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    \28\ 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 at 47-48.
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    For the second implementation period, the RPGs are set for 2028. 
Reasonable progress goals are not enforceable targets, 40 CFR 
51.308(f)(3)(iii); rather, they ``provide a way for the states to check 
the projected outcome of the [long-term strategy] against the goals for 
visibility improvement.'' 2019 Guidance at 46.

[[Page 55148]]

While states are not legally obligated to achieve the visibility 
conditions described in their RPGs, Sec.  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 emission 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 through 2004. See 40 CFR 
51.308(f)(1)(i), 82 FR 3078 at 3097 and 3098, January 10, 2017.
    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 
under 40 CFR 51.308(f)(2)(i), that no additional emission reduction 
measures would be reasonable to include in its long-term strategy. 40 
CFR 51.308(f)(3)(ii). 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. See 2019 Guidance at 50-
51.
    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 emission 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.'' See 82 FR 3078 at 
3093, 3099 and 3100, January 10, 2017; 2019 Guidance at 22; 2021 
Clarifications Memo at 15-16.

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 subsection 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. 40 CFR 51.308(f)(6), (f)(6)(i), and 
(f)(6)(iv). The IMPROVE monitoring data is used to determine the 20% 
most anthropogenically impaired and 20% clearest sets of days every 
year at each Class I area and tracks visibility impairment over time.
    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. 40 CFR 51.308(f)(6)(ii) and (iii). 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 and are not subject to EPA review as 
part of the Agency's evaluation of a SIP revision.\29\ All states' SIPs 
must also provide for any other elements, including reporting, 
recordkeeping, and other measures, that are necessary for states to 
assess and report on visibility. 40 CFR 51.308(f)(6)(vi). Per the 2019 
Guidance, a state may note in its Regional Haze SIP that its compliance 
with the Air Emissions Reporting Rule (AERR) 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 how projected emissions were developed for use 
in establishing RPGs for its own and nearby Class I areas.\30\
---------------------------------------------------------------------------

    \29\ See ``Step 8: Additional requirements for regional haze 
SIPs'' in 2019 Regional Haze Guidance at 55.
    \30\ Id.
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    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 Sec.  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.'' \31\ 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.
---------------------------------------------------------------------------

    \31\ 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.

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[[Page 55149]]

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 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. See 81 FR 26942, 26950 (May 4, 2016), (82 FR 3078 at 3119, 
January 10, 2017). 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 emission reduction 
measures from the first implementation period, and the resulting 
emissions reductions. 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, Sec.  
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, 40 CFR 51.308(g)(3)(i)(B), and then to 
calculate the difference between those current conditions and baseline 
(2000-2004) visibility conditions in order to assess progress made to 
date. See 40 CFR 51.308(g)(3)(ii)(B). States must also assess the 
changes in visibility impairment for the most impaired and clearest 
days since they submitted their first implementation period progress 
reports. See 40 CFR 51.308 (f)(5) and (g)(3)(iii)(B). Since different 
states submitted their first implementation period progress reports at 
different times, the starting point for this assessment will vary state 
by state.
    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. See 40 
CFR 51.308(f)(5) and (g)(4). 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 include an explanation of 
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.

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.'' 40 CFR 51.308(i)(2). 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. 40 CFR 51.308(i)(2). In order 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. 40 CFR 51.308(i)(3). 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. 40 CFR 
51.308(i)(4).

V. The EPA's Evaluation of Missouri's Regional Haze Submission for the 
Second Implementation Period

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

    Missouri submitted its Regional Haze SIP for the first 
implementation period to the EPA on August 5, 2009, and supplemented on 
January 30, 2012. Missouri relied on the Clean Air Interstate Rule 
(CAIR) to satisfy BART requirements. The EPA approved Missouri's first 
implementation period Regional Haze SIP submission on June 26, 2012 (77 
FR 38007, June 26, 2012).\32\ The requirements for Regional Haze SIPs 
for the first implementation period are contained in 40 CFR 51.308(d) 
and (e). 40 CFR 51.308(b). In July 2008, the CAIR rule was vacated by 
the District of Columbia Circuit Court.\33\ In response on August 8, 
2011, the EPA replaced CAIR with the Cross-State Air Pollution Rule 
(CSAPR).\34\ Afterwards, the EPA promulgated the CSAPR better than BART 
rule, allowing states to rely on CSAPR to satisfy BART 
requirements.\35\ In that same action, the EPA issued FIPs to replace 
reliance on CAIR for BART with reliance on CSAPR to satisfy BART 
requirements. This action included Missouri. Pursuant to 40 CFR 
51.308(g), Missouri was also required to submit a five-year progress 
report as a SIP revision for the first implementation period. On August 
5, 2014, Missouri submitted the required progress report to the EPA. 
The EPA approved the progress report on September 29, 2015 (80 FR 
58410, September 29, 2015). On July 31, 2017, Missouri submitted a SIP 
revision to change their reliance on CAIR for BART to relying on CSAPR 
for BART. The EPA approved this SIP revision.\36\
---------------------------------------------------------------------------

    \32\ The EPA's action included a limited approval as the state 
relied on the EPA's Federal Implementation Plan (FIP) for the 
interstate transport program to address the required best available 
retrofit technology (BART) requirements for certain electric 
generating units (EGUs).
    \33\ North Carolina v. EPA, 531 F.3d 896 (D.C. Cir. 2008), 
modified on rehearing, North Carolina v. EPA, 550 F.3d 1176, 1178 
(D.C. Cir. 2008).
    \34\ 76 FR 48208 August 8, 2011.
    \35\ 77 FR 33642 June 7, 2012.
    \36\ 81 FR 50531 September 24, 2018.
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B. Missouri's Second Implementation Period SIP Submission and the EPA's 
Evaluation

    In accordance with CAA sections 169A and the RHR at 40 CFR 
51.308(f), (g), and (i), on August 26, 2022, Missouri submitted a 
revision to Missouri's SIP to address its Regional

[[Page 55150]]

Haze obligations for the second implementation period. Missouri made 
its second implementation period Regional Haze SIP submission available 
for public comment from March 28, 2022, through May 5, 2022. The state 
held a public hearing for the plan on April 28, 2022. Missouri received 
and responded to public comments and included both the comments and 
responses to those comments in their submission.
    The following sections describe Missouri's SIP submission as well 
as the EPA's evaluation to determine if Missouri's submission meets all 
of 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 paragraph (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 SIPs to address visibility 
impairment establishes ``an `extremely low triggering threshold' in 
determining which States should submit SIPs for regional haze.'' 64 FR 
35714 at 35721, July 1, 1999. In concluding that each of the contiguous 
48 states and the District of Columbia meet this threshold,\37\ the EPA 
relied on ``a large body of evidence demonstrat[ing] that long-range 
transport of fine PM contributes to regional haze,'' id., 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.'' Id. at 35722. 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.'' Id. at 35721. 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.'' Id. at 35722. The EPA's 2017 
revisions to the RHR did not disturb this conclusion. See 82 FR 3078 at 
3094, January 10, 2017.
---------------------------------------------------------------------------

    \37\ 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 35714 at 35721, July 1, 1999. Hawaii, Alaska, 
and the U.S. Virgin Islands must also submit regional haze SIPs 
because they contain Class I areas.
---------------------------------------------------------------------------

    Missouri contains two Class I Areas: Hercules-Glades Wilderness 
Area and Mingo National Wildlife Refuge. In Missouri's Regional Haze 
plan for the first planning period, submitted on August 5, 2009, and 
supplemented on January 30, 2012, Missouri analyzed four Class I Areas 
as potentially affected by Missouri emissions. In addition to the two 
Class I Areas in Missouri, the state identified Caney Creek Wilderness 
Area and Upper Buffalo Wilderness Area located in Arkansas.\38\ In 
Missouri's Regional Haze plan for the second planning period, submitted 
August 26, 2022, Missouri identifies nine Class I Areas: Hercules-
Glades Wilderness Area and Mingo National Wildlife Refuge in Missouri, 
Upper Buffalo Wilderness Area, Arkansas, Seney National Wildlife Refuge 
and Isle Royale Wilderness in Michigan, Mammoth Cave National Park, 
Kentucky, Linville Gorge Wilderness Area and Shining Rock Wilderness 
Area in North Carolina, and Sipsey Wilderness Area, Alabama; as 
potentially affected by Missouri emissions. To make this determination, 
Missouri primarily relied on the cumulative sulfate and nitrate 
extinction weighted residence time (EWRT) multiplied by Q/d (emissions 
divided by distance) analysis performed by a CenSARA contractor to 
identify the sources with the highest estimated contributions to Class 
I Areas. As further discussed in section E of this preamble, Missouri 
selected sources contributing more than 1 percent to any Class I Area 
for further evaluation.\39\
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    \38\ ``State of Missouri Air Quality State Implementation Plan 
Regional Haze, Section D, Plan Revision'' Page 47, submitted 
November 9, 2009. Available in Docket: EPA-R07-OAR-2012-0153.
    \39\ See Table 36, starting on page 103 of Missouri's August 
2022 submittal.
---------------------------------------------------------------------------

    CenSARA performed technical analyses to help assess source and 
state-level contributions to visibility impairment and the need for 
interstate consultation. CenSARA's analyses relied on a back-trajectory 
model combined with air quality measurement data and emission 
inventories to identify the geographic areas and emission sources with 
a high probability of contributing to anthropogenically impaired 
visibility at Class I areas within CenSARA and nearby states. For the 
EWRT multiplied by Q/d analysis, back trajectory residence times were 
first calculated by summing the amount of time trajectories reside in a 
specific geographic area (e.g., modeling grid cell). The trajectory 
residence times were then weighted by sulfate and nitrate extinction 
coefficients to account for the varying contributions of sulfates and 
nitrates to total light extinction. To determine the potential impact 
from sources of SO2 and NOX emissions (precursors 
of SO4 and NO3, respectively), the EWRT values 
for SO4 and NO3 were combined with emissions (Q) 
from sources of SO2 and NOX, respectively. 
CenSARA states chose to focus on electric generating units (EGU) and 
non-EGU stationary point sources since these sources comprise major 
fractions of the NOX and SO2 emissions inventory. 
To incorporate the effects of dispersion, deposition and chemical 
transformation along the path of the trajectories, emissions were 
inversely weighted by the distance (d) between the centers of the grid 
cell emitting the emissions and the grid cell containing the IMPROVE 
site.
    Missouri also included Class I Areas that were identified through 
the consultation process as being affected by sources in Missouri, when 
the consulting state identified specific Missouri sources that impact 
the downwind Class I Area.\40\ Missouri also consulted with MANE-VU on 
Class I Areas in Maine, New Jersey, New Hampshire and Vermont. Neither 
MANE-VU nor Missouri specifically list which Areas in those states are 
affected by Missouri sources. The EPA believes the affected Class I 
areas may include:

[[Page 55151]]

Acadia, Moosehorn, and Roosevelt Campobello in Maine; Great Gulf and 
Presidential Range-Dry River in New Hampshire; Brigantine Wilderness, 
New Jersey; and Lye Brook, Vermont. New Jersey consulted with Missouri. 
Neither MANE-VU nor New Jersey specify a source for which Missouri 
should conduct a four-factor analysis for its impact on Brigantine 
Wilderness. Missouri does not explicitly state why it treats the MANE-
VU Areas different than the other consulted Areas, other than to point 
out MANE-VU and New Jersey did not specify a Missouri source to 
evaluate. While MANE-VU and New Jersey did not specify a source for 
Missouri to analyze, MANE-VU did have six ``Asks'' of other states. 
Although Missouri does not include the MANE-VU Class I Areas in the 
same way as the other identified Areas, Missouri did consult with MANE-
VU and New Jersey on the ``Asks.'' Despite the apparent inconsistencies 
in Missouri's treatment of Class I Areas, we find the resulting 
identification of Class I Areas as being impacted by Missouri sources 
to be reasonable. However, the EPA finds this requirement is not 
separable from the overarching requirement of 40 CFR 51.308(f)(2) to 
establish a long-term strategy and as explained in section V.E. of this 
preamble, the EPA is proposing to disapprove Missouri's long-term 
strategy. Accordingly, the EPA proposes to disapprove this element of 
Missouri's second planning period regional haze plan.
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    \40\ See Table 37, starting on page 104 of Missouri's submittal.
---------------------------------------------------------------------------

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. 40 CFR 
51.308(f)(1)(vi)(B).
    In Chapter 3 of MoDNR's submittal, Missouri determines and presents 
the baseline, natural, and current visibility conditions as well as the 
differences between these for both the 20 percent most 
anthropogenically impaired days and the 20 percent clearest days for 
the state's two Class I Areas consistent with the EPA's RHR and 
guidance. Specifically, Missouri presents the latest available 
visibility monitoring data as accessed on January 14, 2020, for the 
most recent 5-year period (2014-2018) and the baseline period (2000-
2004) as collected at IMPROVE sites and made available on the Federal 
Land Manager Environmental Database (FED). Using the EPA's revised 
IMPROVE equation (Pitchford et al., 2007), Missouri also calculated the 
light extinction contributions from individual particle components. The 
state provides the required calculated visibility data as summarized in 
Table 1 of this preamble. Missouri also presents the progress made 
since the baseline period (2000-2004) as well as the difference between 
current (2014-2018) and natural visibility conditions for both the most 
impaired and clearest days. Missouri presents the uniform rate of 
progress data for each Missouri Class I Area and additional light 
extinction information for specific particle components in section 
3.3.6 of the state's submittal. Missouri calculated annual URP values 
of 0.27 dv/year and 0.29 dv/year needed to reach natural visibility on 
the 20% most impaired days at at Hercules-Glades and Mingo, 
respectively.\41\ Missouri's URP values for 2028 are shown in Table 1 
of this preamble. Missouri did not choose to adjust its URP for 
international anthropogenic impacts or to account for the impacts of 
wildland prescribed fires as allowed in 40 CFR 51.308(f)(1)(vi)(B). 
Missouri additionally compares observed and modeled visibility 
conditions and extinction compositions in section 3.3.9 of the 
submittal. The EPA further reviews the state's calculations and 
visibility data in the technical support document (TSD) as contained in 
the docket for this rulemaking. Based on the EPA's review, detailed in 
the TSD, the EPA proposes to find that Missouri appropriately 
determined the baseline, current and natural visibility conditions as 
well as the other required calculations for the two Missouri Class I 
Areas and thus meets the requirements of 40 CFR 51.308(f)(1). 
Therefore, the EPA proposes to approve this element of Missouri's 
submission.
---------------------------------------------------------------------------

    \41\ See ``Table 9. Uniform Annual Rate of Improvements Needed 
to Reach 2016 Natural Visibility for the Most Impaired Days'' in the 
MO Regional Haze SIP--Final August 2022.

                                                  Table 1--Missouri Class I Areas Visibility Conditions
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                            Baseline 2000-2004 average        Natural visibility (dv)        Current 2014-2018 average
                                                  visibility (dv)        --------------------------------         visibility (dv)          2028 Uniform
          Missouri Class I area          --------------------------------                                --------------------------------     rate of
                                             20% Most      20% Clearest      20% Most      20% Clearest      20% Most      20% Clearest    progress (dv)
                                           impaired days       days        impaired days       days        impaired days       days
--------------------------------------------------------------------------------------------------------------------------------------------------------
Hercules Glades.........................           25.17           12.84            9.30            4.69           18.72            9.71           18.82
Mingo...................................           26.31           14.37            9.24             5.3           20.13           11.08           19.48
--------------------------------------------------------------------------------------------------------------------------------------------------------

E. Long-Term Strategy for Regional Haze

1. Source Selection
    40 CFR 51.308(f)(2)(i) requires states to ``. . . consider 
evaluating major and minor stationary sources or groups of sources, 
mobile sources, and area sources. The State must include in its 
implementation plan a description of the criteria it 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.'' As part of its reasonable 
progress determinations, the state must describe the criteria used to 
determine which sources or group of sources were evaluated (i.e., 
subjected to four-factor analysis) for the second implementation period 
and how the Four Factors were

[[Page 55152]]

taken into consideration in selecting the emission reduction measures 
for inclusion in the long-term strategy. 40 CFR 51.308(f)(2)(iii).
    States may rely on technical information developed by the RPOs of 
which they are members to select sources for four-factor analysis and 
to conduct that analysis, as well as to satisfy the documentation 
requirements under Sec.  51.308(f). Where an RPO has performed source 
selection and/or four-factor analyses (or considered the five 
additional factors in Sec.  51.308(f)(2)(iv)) for its member states, 
those states may rely on the RPO's analyses for the purpose of 
satisfying the requirements of Sec.  51.308(f)(2)(i) so long as the 
states have a reasonable basis to do so and all state participants in 
the RPO process have approved the technical analyses. 40 CFR 
51.308(f)(3)(iii). States may also satisfy the requirement of Sec.  
51.308(f)(2)(ii) to engage in interstate consultation with other states 
that have emissions that are reasonably anticipated to contribute to 
visibility impairment in a given Class I area under the auspices of 
intra- and inter-RPO engagement.
    Missouri explains various methods the state considered when 
determining which sources to bring forward for further evaluation. 
Ultimately, Missouri primarily relied on the cumulative sulfate and 
nitrate extinction weighted residence time (EWRT) multiplied by Q/d 
(emissions divided by distance) analysis performed by a CenSARA 
contractor to determine the sources with the highest estimated 
contributions to Class I Areas. Missouri selected sources contributing 
more than 1 percent to any Class I Area for further evaluation.\42\ 
This resulted in the selection of nine Missouri sources and eighteen 
out of state sources. Missouri also considered sources identified by 
other states, RPOs or FLMs and explained whether they would be further 
evaluated or not and the rationale behind that decision. Missouri 
removed two sources initially selected, Buzzi Unicem and Ameren 
Meramec, due to decreasing emissions trends. Specifically, Buzzi Unicem 
provided the state with updated emissions information and demonstrated 
that the reductions were due to an enforceable consent decree entered 
in 2017. After the state reevaluated Buzzi Unicem's impacts with the 
updated emissions information, the visibility contribution dropped 
below the 1 percent threshold used by the state and was therefore 
removed from further consideration. Regarding Ameren Meramec, Missouri 
points out that the facility voluntarily switched two boilers from 
burning coal to natural gas in 2016 and that the facility was expected 
to retire by December 2022. Due to the expected shutdown date before 
2028, Missouri removed Meramec from consideration of additional control 
measures. However, the shutdown date cited by Missouri for Ameren 
Meramec is not federally enforceable. The EPA independently confirmed 
that emissions from the Meramec facility have indeed decreased 
significantly consistent with reduced operations preparing for shutdown 
and with no reported emissions or operating hours in 2023. Given these 
facts, the EPA finds that removal of these two sources is consistent 
with the EPA's 2019 Guidance and 2021 Clarifications Memo. However, 
Missouri may also consider in future planning periods whether 
evaluation of the removed sources (assuming continued operation of the 
sources) would result in a more effective control technology being 
found reasonable.
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    \42\ See Table 36, starting on page 103 of Missouri's submittal.
---------------------------------------------------------------------------

    The seven sources Missouri selected for further evaluation are: 
John Twitty Energy Center, Associated Electric Cooperative Incorporated 
(AECI) New Madrid Power Plant, AECI Thomas Hill Power Plant, Sikeston 
Power Station, Ameren Labadie Energy Center, Ameren Rush Island Energy 
Center, and Mississippi Lime Company. More information on these sources 
is provided here and in the TSD.
    John Twitty Energy Center is located in Springfield, Missouri in 
Greene County. Units 1 and 2 are dry bottom wall fired boilers. Unit 1 
has a capacity of 205 megawatts (MW). Unit 2 has a capacity of 309.6 
MW. Both units burn Powder River Basin low sulfur coal. Unit 1 does not 
utilize SO2 controls. Unit 2 has fluidized bed limestone 
injection for SO2 control. Both units have selective 
catalytic reduction (SCR) for NOX control. Unit 2 also has 
overfire air (OFA). Both units have baghouses for particulate control.
    AECI New Madrid Power Plant is located near Marston, Missouri in 
New Madrid County. Units 1 and 2 are cyclone boilers with capacities of 
640 MW each and burn Powder River Basin low sulfur coal. The units do 
not utilize SO2 control. For NOX control, both 
units have SCR and OFA. For particulate control, both units have 
electrostatic precipitators (ESP).
    AECI Thomas Hill Power Plant is located in Clifton Hill, Missouri 
in Randolph County. Units 1 and 2 are cyclone boilers. Unit 3 is a dry 
bottom wall fired boiler. Unit 1 has capacity of 185 MW. Unit 2 has a 
capacity of 305 MW. Unit 3 has capacity of 777 MW. All units burn 
Powder River Basin low sulfur coal and do not utilize SO2 
control. Units 1 and 2 have OFA and SCR for NOX control. 
Unit 3 has OFA, low NOX burners, and SCR for NOX 
control. For particulate control, all 3 units have ESP.
    Sikeston Power Station is located near Sikeston, Missouri in Scott 
County. Unit 1 is a dry bottom wall fired boiler with capacity of 235 
MW and burns Powder River Basin low sulfur coal. Unit 1 has a tray/
Venturi wet scrubber with control device efficiency of 76% (per state's 
four factor analysis), but the scrubber is not operating and is not 
easily restarted. The facility does not currently utilize any 
SO2 control. For NOX control, Unit 1 has low 
NOX burners with OFA. For particulate control, Unit 1 has an 
ESP.
    Ameren Labadie Energy Center is located in Labadie, Missouri in 
Franklin County. Units 1 and 2 are tangentially fired boilers with 
capacities of 675 MW each and burn Powder River Basin low sulfur coal. 
Units 3 and 4 are tangentially fired boilers with capacities of 690 MW 
each and burn Powder River Basin low sulfur coal. None of the units 
utilize control for SO2. For NOX control, all of 
the units have low NOX burners, separated overfire air 
(SOFA), and neural network optimization. For particulate control, all 
of the units have ESP.
    Ameren Rush Island Energy Center is located in Festus, Missouri in 
Jefferson County. Units 1 and 2 are tangentially fired boilers with 
capacities of 621 MW each and burn Powder River Basin low sulfur coal. 
The units do not utilize SO2 control. For NOX 
control, both units have low NOX burners, SOFA, and neural 
network optimization. For particulate control, both units have ESP.
    Mississippi Lime Company is a lime processing plant located in Ste. 
Genevieve, Missouri in Ste. Genevieve County. The following emission 
units were determined to be the plant's primary sources of 
NOX and SO2 emissions: Peerless Rotary Kilns and 
Mississippi Rotary Kilns which fire coal and coke. For SO2 
control, the Mississippi Rotary Kilns are equipped with wet scrubbers. 
Some kilns have lime injection. The remaining Mississippi Rotary Kiln 
units do not have lime injection; however, the facility indicates that 
the exhaust stream provides inherent process scrubbing of the exhaust 
stream due to lime in the process. The facility indicates good 
combustion and optimization of processes control of NOX on 
all the units, and that the Peerless kilns also utilize a preheater. 
The units do not have any add-on NOX controls.

[[Page 55153]]

    Although the EPA finds Missouri's source selection methodology and 
the sources selected for further analysis reasonable for the second 
planning period, the EPA believes the RHR requirement at 51.308(f)(2), 
to consider the four factors in establishing the long-term strategy, 
encompasses the selection of sources for further analysis, and 
therefore is not separable. For the reasons described in section E.2 of 
this preamble, the EPA is proposing to disapprove Missouri's long-term 
strategy, which encompasses source selection, in Missouri's second 
implementation period regional haze plan as not meeting the 
requirements of 40 CFR 51.308(f)(2).
2. Four-Factor Analysis
    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. CAA section 169A(b)(2)(B). As explained in the Background section 
of this document, reasonable progress is achieved when all states 
contributing to visibility impairment in 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. 40 CFR 51.308(f)(2)(i). Each 
state's long-term strategy must include the enforceable emission 
limitations, compliance schedules, and other measures that are 
necessary to make reasonable progress. 40 CFR 51.308(f)(2). 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 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 emission rate. Existing measures that are necessary to 
make reasonable progress must also be included as permanent and 
federally enforceable \43\ emissions limits in the long-term strategy. 
In developing its long-term strategies, a state must also consider the 
five additional factors in Sec.  51.308(f)(2)(iv).
---------------------------------------------------------------------------

    \43\ The EPA also interprets the requirement to be permanent and 
federally enforceable as being practically enforceable, i.e., an 
operational or emissions limit with the necessary reporting and 
recordkeeping requirements such that the source reports compliance 
with and that can practically be measured and enforced.
---------------------------------------------------------------------------

    In Chapter 4 of Missouri's submittal, the state explains the four-
factor analyses performed either by the state or the source for the 
seven Missouri sources that were brought forward for further 
evaluation. The state describes how each of the four factors is 
considered. First, Missouri explains the cost of compliance is 
considered by performing a cost analysis for each source and each 
technically feasible control measure for both SO2 and 
NOX. The state also describes the process used to establish 
the cost threshold that the state uses to determine whether the cost 
effectiveness of each control measure is reasonable and therefore 
should be included in the long-term strategy. Specifically, Missouri 
refers to control cost values from the first implementation period, 
compiled by the state of Arkansas, to set a cost threshold derived from 
those values. Second, Missouri generally describes how the state 
assumed the time necessary for compliance for each control type based 
on prior EPA studies and literature. Third, Missouri describes how 
energy and non-air quality environmental impacts of compliance are 
considered. For example, quantifiable energy impacts for a given 
control type are included in the cost estimates. Fourth, Missouri 
explains the two methods used to estimate the remaining useful life of 
the sources evaluated while also considering the remaining useful life 
of the control types. In response to comment on this point, Missouri 
included cost estimates assuming the default remaining useful life 
values that the EPA recommends using for specific control devices.
    Ameren Missouri and Mississippi Lime Company provided full four-
factor analyses for their respective facilities. Missouri performed the 
four-factor analyses for the remaining sources. The four-factor 
analyses presented in Missouri's SIP cover what Missouri determined to 
be technically feasible control measures for both SO2 and 
NOX for each source. Specifically, the control technologies 
evaluated by Missouri are displayed in Table 2 of this preamble.

           Table 2--Control Technologies Evaluated by Missouri
------------------------------------------------------------------------
 
-------------------------------------------------------------------------
                         SO Control Technologies
------------------------------------------------------------------------
Flue Gas Desulfurization (FGD)--Wet, Spray Dry, Dry Scrubber (50% to 99%
 control efficiency):
     Wet Lime Scrubber, typical control efficiency 90%-99%
     Wet Limestone Scrubber, typical control efficiency 90%-99%
     Dual-Alkali Scrubber, typical control efficiency 90%-95%
     Spray Dry Absorber (SDA), typical control efficiency 90%-
     95%
     Dry Sorbent Injection (DSI), typical control efficiency 50%-
     80%
     Circulating Dry Scrubber
     Hydrated Ash Reinjection
Limestone Injection.
Low sulfur content coal.
Fuel Switch.
------------------------------------------------------------------------
                         NO Control Technologies
------------------------------------------------------------------------
Selective Catalytic Reduction (SCR), typical control efficiency 90%.
Low NOX Burners (LNB), typical control efficiency 40%-60%.
Selective Non-Catalytic Reduction (SNCR), typical control efficiency 35%-
 50%.
Overfire Air (OFA), typical control efficiency 20%.
Flue Gas Recirculation (FGR).
Low Excess Air (LEA).
------------------------------------------------------------------------


[[Page 55154]]

    The full details for the state and source performed four-factor 
analyses are included in Appendix C to the state submittal included in 
the docket for this action.

                                             Table 3--Summary of Results of Missouri's Four-Factor Analyses
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                             Emission
                                                                                                            Annualized       reduction    Effective cost
              Facility                        Unit                 Pollutant         Control technology      cost ($)        (tons per        ($/ton)
                                                                                                                               year)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Labadie Energy Center *............  B1....................  SO2.................  DSI..................     $27,074,061           7,011          $3,862
                                                             NOX.................  SNCR.................       3,261,106             450           7,247
                                     B2....................  SO2.................  DSI..................      27,074,061           7,031           3,851
                                                             NOX.................  SNCR.................       3,261,106             450           7,247
                                     B3....................  SO2.................  DSI..................      25,419,801           6,592           3,856
                                                             NOX.................  SNCR.................       3,333,575             425           7,844
                                     B4....................  SO2.................  DSI..................      25,419,801           6,854           3,709
                                                             NOX.................  SNCR.................       3,333,575             425           7,844
Rush Island Energy Center *........  B1....................  SO2.................  DSI..................      28,751,220           6,831           4,209
                                                             NOX.................  SNCR.................       3,000,218             375           8,001
                                     B2....................  SO2.................  DSI..................      28,822,931           7,337           3,928
                                                             NOX.................  SNCR.................       3,000,218             375           8,001
Mississippi Lime Company *.........  EP-069, EP-070, EP-071  SO2.................  DSI..................         984,041           11.61          84,800
                                                             NOX.................  SNCR.................         465,644              24          19,100
                                     EP-640, EP-645........  SO2.................  DSI..................       1,344,685            8.62         156,000
                                                             NOX.................  SNCR.................         809,506              85           9,500
                                     EP-180H, EP-186N, EP-   SO2.................  Wet Lime Scrubber....       1,632,862          171.09           9,500
                                      187N.
New Madrid Power Plant *...........  B1....................  SO2.................  DSI..................      20,268,773           5,025           4,033
                                     B2....................  SO2.................  DSI..................      22,003,761           5,561           3,957
Thomas Hill Energy Center *........  B1....................  SO2.................  DSI..................       8,255,270           1,837           4,494
                                     B2....................  SO2.................  DSI..................      12,245,800           2,867           4,271
                                     B3....................  SO2.................  DSI..................      29,936,230           7,698           3,889
John Twitty Energy Center *........  B1....................  SO2.................  DSI..................       6,764,511           1,794           3,771
Sikeston Power Station *...........  B1....................  SO2.................  DSI..................      13,532,594           3,443           3,930
                                                             NOX.................  SCR..................       7,899,846             774          10,209
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Missouri noted these cost estimates were calculated assuming a remaining useful life consistent with the EPA's control cost manual (CCM), however,
  some values still do not comport with EPA's control cost manual. Specifically, Missouri assumed a 25-year useful life for Wet FGD, SDA and DSI
  controls when the EPA recommends a 30-year useful life. Missouri assumed a 30-year useful life for SCR and a 20-year useful life for SNCR, consistent
  with the CCM.

    The results of Missouri's four-factor analyses are shown in Table 3 
of this preamble. Missouri details the cost effectiveness for each 
control type and unit and categorically concludes that each control 
measure is not reasonable because the cost effectiveness exceeds the 
cost threshold set by Missouri, as discussed later in this section. 
Consistent with the finding that new control measures are not 
necessary, Missouri finds that current existing operations at each 
facility are needed for reasonable progress.
    For the reasons described below, the EPA proposes to find that 
Missouri has not adequately supported the conclusion that existing 
measures satisfy the requirement to make reasonable progress. Missouri 
has not definitively shown that further reductions of visibility 
impairing pollutants are not reasonable and has not adequately 
explained how its approach is consistent with the CAA's requirement to 
make reasonable progress. The EPA discusses each of the following lines 
of evidence that support this proposed finding. First, the state 
rejected otherwise reasonable control measures that would reduce tens 
of thousands of tons of visibility impairing pollutants and improve 
visibility at Missouri and other states' Class I areas. This decision 
was based primarily on the unreasonable justification and use of the 
selected cost threshold. Second, the state's cost effectiveness 
calculations do not fully align with EPA guidance such as the Control 
Cost Manual. When the EPA corrects the deficiencies of Missouri's cost 
analysis, we find cost effective controls are available on most if not 
all sources evaluated by Missouri. Third, Missouri has not included 
practically enforceable emissions limits as part of its long-term 
strategy to make reasonable progress. Specifically, the included source 
agreements do not contain explicit enforceable emissions limits 
associated with existing operations in addition to problematic 
provisions included in the source agreements rendering them 
unenforceable and not permanent.

Missouri's Justification and Use of the Selected Cost Threshold Is 
Unreasonable

    Missouri chose to establish a cost threshold based on control cost 
values from the first planning period adjusted to 2021 dollars. Using a 
database of first planning period control costs,\44\ Missouri selected 
a cost threshold of $3,658 per ton specific to SO2 for EGUs 
by calculating the first planning period

[[Page 55155]]

mean cost per ton value plus one standard deviation specifically for 
new control technologies (i.e., excluding upgrades to existing controls 
or reliance on lower sulfur coal). Application of this threshold means 
that Missouri considers all cost effectiveness values greater than 
$3,658 per ton to be not cost effective and therefore rejects the 
control measure. Using a similar methodology for NOX 
controls, Missouri selected a cost threshold of $5,370 per ton. The EPA 
commented during both the early engagement period and the formal 
comment period requesting further documentation and justification for 
use of such a cost threshold. In response to comments, Missouri revised 
the control cost thresholds to be slightly higher than originally 
proposed and provided additional documentation. The EPA also commented 
on the fact that multiple sources in the underlying statistical data 
(in the Appendix F spreadsheet) installed controls at costs above the 
state's threshold including at sources similar to the sources selected 
by Missouri. This dataset does not include any Missouri units. By 
selecting the mean plus one standard deviation as a cost effectiveness 
threshold, Missouri appears to ignore those costs that fall above the 
threshold, costs that were found reasonable at nine units (or twenty 
percent) of the previously analyzed EGUs, most of similar size to the 
Missouri EGUs. EPA guidance states that ``when the cost/ton of a 
possible measure is within the range of the cost/ton values that have 
been incurred multiple times by sources of similar type to meet 
regional haze requirements or any other [Clean Air Act] requirement, 
this weighs in favor of concluding that the cost of compliance is not 
an obstacle to the measure being considered necessary to make.'' \45\ 
Missouri states that higher cost/ton values are largely associated with 
smaller capacity EGUs and therefore are not directly comparable with 
cost values for their larger capacity EGUs. However, in the EPA's 
review of the state's cost threshold statistical data, the EPA finds 
that values presented for EGUs greater than 500 MW yield maximum costs 
in the range of $5,000/ton to $6,000/ton for SO2 control and 
generally exceed the cost effectiveness of SO2 control at 
smaller (less than 500 MW) EGUs.
---------------------------------------------------------------------------

    \44\ Missouri relied on a dataset compiled by the State of 
Arkansas. Note that the EPA is not proposing an action with respect 
to Arkansas's regional haze SIP and we are not commenting on the 
approvability of Arkansas's use of the cost methodology, their cost 
threshold, or their overall SIP. Missouri's cost threshold dataset 
is available in Appendix F to the state submittal, in the docket for 
this action.
    \45\ EPA's 2019 ``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.
---------------------------------------------------------------------------

    Additionally, the EPA notes that CenRAP (predecessor organization 
to CenSARA) conducted a sensitivity analysis which evaluated controls 
for sources with a Q/d>5 and cost-effectiveness up to $10,000/ton 
related to the first regional haze planning period. Based on that 
analysis, CenRAP suggested that a range from $4,000 to $5,000/ton (in 
2005 dollars) would be a reasonable threshold for controls because of 
diminishing emission reductions as costs increase beyond that 
range.\46\ In 2021 dollars, the CenRAP range becomes $6,060 to $7,600/
ton.\47\ As described earlier, Missouri relied on other analyses 
performed by CenSARA for this planning period, as well as considered 
costs from the prior planning period so the EPA finds this analysis 
further undermines the reasonableness of Missouri's selected cost 
threshold.
---------------------------------------------------------------------------

    \46\ See ``Sensitivity Run Specifications for CenRAP 
Consultation.pdf,'' available in the docket for this action. See 
also ``so2_cost_ton.xls'' and ``nox_cost_ton.xls,'' also available 
in the docket for this action.
    \47\ Based on the Chemical Engineering Plant Cost Index (CEPCI). 
For 2005 the CEPCI value is 468.2. For 2021, the CEPCI value is 
708.8.
---------------------------------------------------------------------------

    Similarly, the EPA recently proposed a BART FIP for Texas that 
references past BART decisions, specifically that several controls were 
required by either the EPA or States as BART with average cost-
effectiveness values in the $4,200 to $5,100/ton range (escalated to 
2020 dollars).\48\ In 2021 dollars, this range is $5,300/ton to $6,500/
ton.
---------------------------------------------------------------------------

    \48\ See 88 FR 28918, 28963. For 2020 the CEPCI value is 596.2.
---------------------------------------------------------------------------

    Despite the costs from the first planning period being adjusted to 
2021 dollars, the cost thresholds set by Missouri are lower than 
historical values found necessary for BART and reasonable progress 
determinations as evidenced by the control costs above Missouri's 
threshold in the cost effectiveness spreadsheet.\49\ Missouri's cost 
thresholds are based on costs found reasonable during the first 
planning period and therefore do not account for control costs found 
reasonable since that time. For example, other states have since found 
higher control costs to be reasonable, such as Oregon \50\ selecting a 
$10,000/ton threshold. Additionally, Arkansas's second planning period 
regional haze SIP,\51\ which relies on the same underlying statistical 
cost data to establish a threshold as used by Missouri, sets a 
threshold of $5,086 per ton for EGUs for both SO2 and 
NOX control measures.
---------------------------------------------------------------------------

    \49\ The sources listed in the cost effectiveness spreadsheet 
(Appendix F to the state submittal) are accompanied by a link to the 
relevant EPA action.
    \50\ The EPA proposed approval of Oregon's second planning 
period regional haze SIP on February 23, 2024, 89 FR 13622.
    \51\ https://www.adeq.state.ar.us/air/planning/sip/regional-haze.aspx.
---------------------------------------------------------------------------

    One reason for considering higher cost effectiveness thresholds for 
the second planning period (compared to the first planning period) is 
that most of the cheapest available cost-effective emissions reductions 
were required and implemented during the first planning period. These 
were typically SO2 and NOX controls at the 
largest uncontrolled point sources (mostly electric generating units), 
which in many cases had cost-effectiveness values well under $1,000 per 
ton. These relatively cheap controls lead to a low bias when using 
first planning period cost database numbers to calculate mean costs 
(even when adding in one standard deviation). Most remaining point 
sources have smaller emissions and do not have cost effective controls 
at those previously ``cheap'' levels. However, by itself, that is not a 
reasonable justification to reject otherwise potentially cost-effective 
controls in the second planning period and beyond. As we move forward 
in time to subsequent planning periods, source emissions will get 
smaller and potential controls will get more expensive on a cost per 
ton basis. However, the statute still requires states to continue to 
make reasonable progress towards the national goal.
    Missouri's use of the selected cost threshold has the effect of 
rejecting control measures that historically have been widely used to 
meet the regional haze rule requirements, without requiring additional 
emissions reductions or enforceable shutdowns beyond existing 
operations. The EPA has not established a bright line or a recommended 
cost effectiveness threshold to be used by States. However, the EPA 
finds that Missouri's justification and use of the selected cost 
threshold to summarily reject control measures, often with cost 
effectiveness values just above the selected threshold value, is not 
reasonable and does not comport with the stated goals of the CAA and 
RHR. This is especially apparent when considering the magnitude of 
available emissions reductions at Missouri sources and associated 
visibility improvements at Missouri and other states' Class I Areas.
    Missouri still has multiple power plants that are uncontrolled for 
SO2. In fact, Missouri has had the second highest statewide 
total SO2 emissions in the country for each of the last five 
years (2018-2022). Further, of the EGUs selected by Missouri, three 
were among the top 15 SO2 emitters in the country in 2023, 
with Ameren Labadie being the

[[Page 55156]]

highest SO2 emitter in 2023.\52\ As described earlier, many 
states relied on transport programs to satisfy BART in the first 
planning period instead of requiring source specific control 
determinations, including Missouri.\53\ While trading programs are 
effective at reducing emissions on a regional scale, they do not 
require emission reductions or installation of controls on specific 
sources. Therefore, individual sources may avoid installing controls or 
reducing emissions through the purchase or trading of allowances from 
other sources that did opt to install controls or reduce emissions. 
Many of the sources selected by Missouri for further evaluation, such 
as Ameren Labadie, have not installed post combustion control 
equipment. Generally, sources that did not install or consistently 
operate post combustion control equipment relied on the purchase of 
allowances for trading program compliance. And as discussed further 
below, the EPA proposes to find that sources in Missouri have the 
potential for cost-effective control options.
---------------------------------------------------------------------------

    \52\ According to 2023 reported emissions available at https://campd.epa.gov/.
    \53\ 77 FR 38007, June 26, 2012 and 83 FR 48242, September 24, 
2018.
---------------------------------------------------------------------------

    As noted previously, the EPA agrees with FLM assertions that there 
is the potential for significant visibility improvement associated with 
the controls evaluated by Missouri at these sources. However, MoDNR 
argues in each four-factor analysis summary that additional controls 
are not needed. Among the reasons cited, MoDNR states that ``All Class 
I areas impacted by sources in Missouri have made steady and 
significant improvement in visibility, and modeling shows they are 
projected to be below, or well below, their uniform rate of progress 
(URP) glidepaths in 2028.'' \54\ Although the EPA agrees there has been 
improvement in the Class I areas impacted by Missouri sources, several 
of these Class I areas have the highest remaining anthropogenic 
visibility impairment in the country. In particular, based on the 
latest available IMPROVE data averaged over the five-year period of 
2018-2022, Mammoth Cave, Mingo, and Hercules-Glades are in the top 10 
of Class I areas with the greatest anthropogenic visibility 
impairment.\55\ Furthermore, the EPA's modeling shows that a 
significant amount of visibility impairment is projected to remain in 
these Class I areas in 2028.\56\ While not explicitly presented by the 
state as a reason for rejecting additional controls, the EPA has 
reiterated through regulation and guidance that the URP is not a safe 
harbor and an area's position with respect to the URP should not be a 
factor in determining whether a control measure is reasonable. See 2019 
Guidance at 22, 49, and 50 and 2021 Clarifications Memo at 2, 12, 13 
and 15.
---------------------------------------------------------------------------

    \54\ See Appendix C-1-7 to the state's submission.
    \55\ Based on ``Daily Impairment Values Including Patched 
Values'' IMPROVE data spreadsheet, 
sia_impairment_daily_budgets_10_23.csv, updated October 2023, 
obtained from https://vista.cira .colostate.edu/Improve/rhr-summary-
data/. For the 20% most impaired days from 2018-2022, Mammoth Cave 
is the 5th most anthropogenically impaired Class I area with a 5-
year average anthropogenic impairment of 10.4 dv, and Mingo is 6th 
on the list at 10.1 dv. Hercules-Glades is 10th on the list with a 
5-year average anthropogenic impairment of 8.9 dv.
    \56\ Technical Support Document for EPA's Updated 2028 Regional 
Haze Modeling, Office of Air Quality Planning and Standards, United 
States Environmental Protection Agency (September 2019). See Table 
3-2: Base and future year deciview values on the 20% clearest and 
20% most impaired days at each Class I area for the base model 
period (2014-2017) and future year (2028).
---------------------------------------------------------------------------

    The national goal set by Congress outlines both the remedying of 
any existing visibility impairment, and also preventing any future 
visibility impairment. CAA section 169A(a). Further, the EPA has stated 
that in order to accomplish the national goal set by Congress, 
cumulative progress must be made including relatively small reductions 
and visibility benefits from many sources over a wide area over time. 
To that end, visibility should not be used as the sole factor in 
rejecting an otherwise reasonable control measure. See 2021 
Clarifications Memo at 13.
    CAA section 169A(b)(2) requires states to include in their SIPs 
``emission limits, schedules of compliance and other measures as may be 
necessary to make reasonable progress.'' While these emission limits 
must apply to individual sources or units, CAA section 169A(g)(1) does 
not explicitly require states to consider the four factors on a source-
specific basis when determining what amount of emission reductions (and 
corresponding visibility improvement) constitutes ``reasonable 
progress.'' The EPA has consistently interpreted the CAA to provide 
states with 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. While the CAA and the RHR provide states with flexibility 
in evaluating the four reasonable progress factors, states must 
exercise reasoned judgment when choosing which sources, groups of 
sources, or source categories to analyze. Consistent with the state's 
obligation to exercise reasoned judgment in its analysis, the EPA's 
role in reviewing a SIP is not limited to accepting at face value a 
state's analysis in its own SIP submission and its determination that 
it has fully satisfied the requirements of the CAA. Rather, Congress 
tasked the EPA with the responsibility of ensuring that a SIP 
submission satisfies the requirements of the CAA. Abundant case law 
reflects an understanding that the EPA must evaluate SIP submissions 
under CAA section 110(k)(2) and (3).\57\ If a SIP submission is 
deficient in whole or in part, the EPA must so find, and if not 
corrected, implement the relevant requirements through a FIP under CAA 
section 110(c). Courts have held that the EPA's ability to ensure that 
a SIP submission satisfies the requirements of the CAA includes the 
ability to review a state's analysis to ensure that it is ``reasonably 
moored to the Act's provisions and . . . based on reasoned analysis.'' 
\58\ Thus, EPA's oversight role is ``more than the ministerial task of 
routinely approving SIP submissions.'' \59\ If the EPA's role were 
otherwise, Congress would not have expressly tasked the agency with 
both reviewing SIPs for completeness (CAA section 110(k)(1)(B)) and 
reviewing the substance of SIPs (CAA section 110(k)(2)-(4)).
---------------------------------------------------------------------------

    \57\ See e.g., Oklahoma v. EPA, 723 F.3d 1201, 1209 (10th Cir. 
2013) (upholding EPA's disapproval of ``best available retrofit 
technology'' (BART) SIP, noting BART ``does not differ from other 
parts of the CAA--states have the ability to create SIPs, but they 
are subject to EPA review''); see also Westar Energy v. EPA, 608 
Fed. App'x 1, 3 (D.C. Cir. 2015) (``EPA acted well within the bounds 
of its delegated authority when it disapproved of Kansas's proposed 
[good neighbor] SIP.'').
    \58\ North Dakota v. EPA, 730 F.3d 750, 761 (8th Cir. 2013).
    \59\ North Dakota v. EPA, 730 F.3d 750, 761 (8th Cir. 2013). See 
also Alaska Department of Environmental Conservation v. EPA, 540 
U.S. 461, (2004) (concluding that EPA was not limited to verifying 
that a BACT determination had been made, but rather EPA could 
examine the substance of the BACT determination).
---------------------------------------------------------------------------

    For these reasons, the EPA finds that Missouri does not 
sufficiently justify the use of the selected cost threshold to 
repeatedly reject otherwise reasonable control measures that would 
result in potentially meaningful visibility improvements and 
significant emissions reductions. And as explained later in this 
section, the EPA's revised cost analyses for many of the selected 
Missouri sources result in cost effective controls. For these reasons, 
the EPA finds that Missouri's rejection of new control measures is 
unreasonable and inconsistent with the goals of the RHR.

Deficiencies in Missouri's Cost Analyses

    The EPA thoroughly reviewed Missouri's cost analysis for each

[[Page 55157]]

selected source. During both the pre-proposal and formal public comment 
period, the EPA commented on the cost analysis presented in the state's 
plan. The EPA identified specific errors, over- or underestimations, 
inappropriate or unexplained assumptions, and inconsistencies with the 
EPA Air Pollution Control Cost Manual.\60\ In response, Missouri 
addressed many of the EPA's concerns by correcting certain identified 
errors or assumptions. For example, Missouri removed disallowed costs 
from the cost assumptions such as owner's costs and updated cost 
estimates to also include the default remaining useful life as 
recommended by the EPA. However, the EPA believes that Missouri did not 
correct all the deficiencies in the cost assumptions and proposes to 
find certain aspects of the cost analyses are not well supported. The 
EPA further explains these deficiencies in the state's cost analyses in 
the technical support document (TSD), contained in the docket for this 
action. For example, the EPA commented on Missouri's reliance on 
Ameren's four-factor analysis which included a non-default retrofit 
factor of 1.5 for wet FGD and SDA and 1.2 for SCR evaluated at the 
Ameren facilities (Labadie and Rush Island). Missouri and Ameren did 
provide additional documentation in response to the EPA's comment. 
However, Missouri's reliance on Ameren's non-default retrofit factors 
should include more detailed cost estimates related to the specific 
retrofit hardships at each facility. The EPA Air Pollution Control Cost 
Manual (CCM) includes a retrofit factor in the control cost 
calculations to account for the relative difficulty in installing a 
control device. The default value of 1 is associated with average 
difficulty in retrofitting an existing unit with a control device. A 
value of 0.77 is generally assumed for new units. Therefore, the 
default retrofit factor of 1 already includes a 30% increase in costs 
compared to new construction. A retrofit factor of 1.5 is the maximum 
value allowed in the Control Cost Manual spreadsheets and has the 
effect of inflating base cost estimates by 50%. The Control Cost Manual 
(CCM) specifically notes that the retrofit factor should be between 0.7 
and 1.3 for wet FGD systems and between 0.8 and 1.5 for dry FGD systems 
\61\ and documentation of site congestion, site access, complex 
ductwork construction and capacity of existing infrastructure is needed 
to determine the complexity of the retrofit and associated retrofit 
factor. Therefore, to support a retrofit factor above 1 a source should 
provide site specific documentation detailing the inflated costs 
associated with the CCM criteria (site congestion, site access, 
ductwork complexity as well as capacity of existing infrastructure that 
would lead to above average retrofit difficulty). The EPA commented on 
Missouri's reliance on Ameren's four-factor analysis which included a 
non-default retrofit factor of 1.5 for SDA and wet FGD and 1.2 for SCR 
evaluated at the two Ameren facilities (Labadie and Rush Island). 
Specifically, the EPA commented that the state and source needed to 
provide additional documentation to support the use of this non-default 
retrofit factor. In response to the EPA's comment, Missouri and Ameren 
provided additional documentation in the form of aerial imagery 
documenting the site congestion and site access as well as engineering 
plans and schematics of potential control device location, rerouted 
ductwork, and other construction projected as part of installation of 
wet FGD at Labadie. However, these do not appear to be accompanied by 
site-specific cost estimates for the various aspects of the retrofit 
hardship. Ameren also included cost estimates based on prior source 
specific studies for wet FGD and DSI at Labadie and Rush Island (See 
Table 3 in Appendices C-6 and C-7 of the state submittal, 
respectively). However, no specifics are provided about these prior 
studies nor are the underlying cost assumptions provided for comparison 
with the new CCM calculations provided. Ameren reasoned that a higher 
retrofit factor was needed because the prior source-specific studies 
resulted in cost estimates higher than the estimates using the CCM 
assumptions. However, this assumption is not well supported. The EPA 
does not have access to and therefore cannot review the necessary 
underlying cost assumptions from these prior studies to determine the 
reasonableness of those estimates. To support the retrofit factor of 
1.2 for SCR, the state points to the documentation provided for the wet 
FGD as supplied by Ameren but there is no documentation specific to the 
retrofit factor for SCR. Additionally, these higher retrofit factors 
are utilized in the cost calculations for both Ameren facilities 
(Labadie and Rush Island) but the documentation including imagery and 
schematics appear specific to Labadie. Therefore, there appears to be 
no site-specific documentation provided for the non-default retrofit 
factors used for Rush Island.
---------------------------------------------------------------------------

    \60\ EPA Air Pollution Control Cost Manual, https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution.
    \61\ Section 5--Chapter 1: Wet and Dry Scrubbers for Acid Gas 
Control, Section 1.2.3.5. https://www.epa.gov/sites/default/files/2021-05/documents/wet_and_dry_scrubbers_section_5_chapter_1_control_cost_manual_7th_edition.pdf.
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    Detailed, technical cost information and robust documentation is 
needed to justify the inflated costs resulting from the use of the 
maximum retrofit factor value for SO2 controls at each 
Ameren facility. Other electric generating units in the state (and 
outside the state) do not rely on such a non-default retrofit factor 
despite having similar limitations, such as physical space limitations, 
to accommodate control device retrofits.\62\ The EPA invites comment on 
the reasonableness of using a non-default retrofit factor and whether 
other cases of using such a factor may be instructive to the outcome of 
this specific scenario.
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    \62\ See the EPA's response to comment including comment on the 
range of retrofit factors for wet and dry FGD on EGUs. https://www.epa.gov/sites/default/files/2021-05/documents/rtcdocument_wet_and_dry_scrubbers_controlcostmanual_7thedition.pdf.
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    In addition to reviewing Missouri's cost analyses, the EPA 
performed independent cost calculations for certain control measures at 
the selected sources to compare with Missouri's cost calculations. 
These calculations are summarized below and further detailed in the TSD 
included in the docket for this action. The EPA updated certain aspects 
of the Missouri cost calculations to follow EPA guidance. For example, 
the EPA used the default retrofit factor of 1 in our calculations for 
all facilities evaluated. This change, along with the other corrections 
made in the EPA's cost analyses, result in cost effectiveness values of 
SO2 controls near or within the cost range established by 
Missouri. Further, the EPA calculated cost effectiveness numbers are 
similar to maximum control costs implemented in the first planning 
period for several states.
    The EPA's analysis also changed the emissions baseline used in 
determining the emission reduction for a given control to arrive at the 
cost effectiveness (or cost per ton) value. While Missouri relied on 
the average of reported annual emissions to define the reduction 
estimate, the EPA recommends using the maximum annual emissions for the 
analyzed time period when setting the baseline emissions to calculate 
the cost effectiveness. Similarly, the time period selected for the 
baseline emissions also influences the final cost effectiveness value. 
For this reason, the EPA performed the cost analyses using both the 
same time period used by Missouri

[[Page 55158]]

(2016-2020) for a direct comparison and the most recent time period 
(2018-2022) in order to fully evaluate the range of cost effectiveness 
values using all currently available data. The baseline emissions 
assumption alone makes a significant difference when comparing the 
EPA's cost effectiveness values with the state's values, but other 
updates to the cost analysis refine and generally reduce the overall 
costs. Further, when the calculations are corrected to be consistent 
with EPA guidance, there are control costs near and within the cost 
range as identified as reasonable by Missouri. For example, the EPA's 
calculations result in SO2 control costs as low as $2,688 
per ton. Therefore, we propose to find there are likely cost-effective 
control options at most, if not all, sources selected by Missouri. As 
noted previously, there are control costs that were previously found 
reasonable by states or the EPA, in the dataset used by Missouri to set 
a cost threshold, that are similar to the range of costs as calculated 
by Missouri and the EPA. States should provide a sufficient 
justification in order to reject measures that have been required at 
similarly situated facilities in a similar cost range.
    The Federal land managers commented on the state's use of an 
``unreasonably low threshold'' and the inappropriate assumptions 
utilized in the state's cost analyses. On page 54 of Appendix G-2 to 
the state's submittal, the National Park Service (NPS) references the 
aspects of Missouri's cost analyses that are inconsistent with the EPA 
rules or guidance and provides their own estimates of cost 
effectiveness for the selected sources, often significantly lower than 
the values presented by Missouri. The cost values provided by the NPS 
further corroborate the EPA's revised cost analyses, as contained in 
the TSD, that result in cost effective controls at most of the state's 
selected sources.
    In Table 21 of the TSD, the EPA identifies the cost effectiveness 
in 2021 dollars for SO2 control measures such as DSI, SDA 
and wet FGD. For NOX, the EPA evaluates SCR and SNCR. In 
Table 29 of the TSD, the EPA identifies the cost effectiveness in 2021 
dollars for SCR and SNCR. The spreadsheets included in the docket 
contain all the underlying data for the EPA's cost analyses including 
the cost effectiveness values in 2021 dollars using both baseline time 
periods as previously mentioned.\63\ For example, the EPA's estimated 
cost effectiveness values for DSI range from $2,688 per ton to $4,119 
per ton. The EPA's estimated cost effectiveness values for SDA range 
from $3,966 per ton to $7,846 per ton. The EPA's estimated cost 
effectiveness values for wet FGD range from $4,081 per ton to $9,201 
per ton. The EPA's estimated cost effectiveness values for SCR range 
from $795 per ton to $27,208 per ton. The lowest costs in this dataset 
are associated with the units that already have SCR installed. In this 
case, the control cost is entirely associated with operation of the 
existing SCR with no additional capital cost of installation since they 
are already installed on those units. The EPA's estimated cost 
effectiveness values for SNCR range from $7,429 per ton to $16,580 per 
ton. Consistent with Missouri's cost analyses, the EPA did not 
calculate the cost effectiveness of SNCR on units that already have SCR 
installed. Additionally, the EPA did not evaluate SNCR for Sikeston as 
a prior technical infeasibility determination was made by the 
source.\64\
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    \63\ The following values presented as minimum and maximum cost 
effectiveness values include the full range of values for both 
baseline emission time periods.
    \64\ In January 2009, Sikeston submitted an applicability 
determination request to install SNCR. However, after initial 
testing, Sikeston determined that SNCR was infeasible at the 
facility due to stalactite formation, dropping and damaging the 
boiler tubes. Based on that information, Missouri removed SNCR from 
further consideration in Sikeston's four-factor analysis. Similarly, 
the EPA did not evaluate SNCR at Sikeston. See Appendix C-5 to 
Missouri's submittal for more information.
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    Table 4 of this preamble below includes an abbreviated summary of 
the EPA's cost analyses for certain SO2 control devices. The 
EPA's methodology for the cost calculations is included in the TSD 
along with the full table of control cost results. In table 4 of this 
preamble below, we present only the values associated with wet FGD with 
an emissions limit of 0.06 lb/mmBTU. The TSD also presents costs 
associated with wet FGD with an emissions limit of 0.04 lb/mmBTU. Cost 
effectiveness values associated with the 0.04 lb/mmBTU emissions limit 
are lower due to the greater emissions reductions. To be conservative, 
this table presents only the highest cost per ton values (i.e., least 
cost-effective) from the two time periods evaluated by the EPA for each 
control type by unit. Values for both time periods are presented in the 
TSD. Generally, the EPA's resulting cost effectiveness values are lower 
(more cost effective) than the values presented by Missouri. The cost 
effectiveness of wet FGD is higher than SDA. However, wet FGD delivers 
significant improvements in cost effectiveness as the tonnage of 
SO2 removal increases due to the greater level of control. 
DSI appears the most cost effective given the lower capital cost 
compared with SDA and wet FGD, but also comes with lower control 
efficiency. For facilities with higher cost effectiveness values for 
SDA and wet FGD, DSI may be a reasonable option. The EPA notes that 
there are examples nationally of each of these control types being 
implemented at large electric generating units such that these types of 
controls are technically and economically feasible at such sources. 
Specifically, these types of SO2 controls were implemented 
at the sources included in the underlying data for Missouri's cost 
threshold, and in some cases, with cost effectiveness values higher 
than the threshold set by Missouri. As previously discussed, if 
Missouri would have set the cost threshold for this planning period 
nearer other states thresholds or near the maximum of costs from the 
first planning period (i.e., around $6,000/ton), both the cost 
effectiveness values presented by Missouri and the EPA's revised values 
would be below that threshold for most SO2 control types.

                                    Table 4--Summary of the EPA's Cost Effectiveness Values for DSI, SDA and Wet FGD
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                         2021$ Cost
                                                                                                               SO2 reduction (tons    effectiveness ($/
                                                                     Date range                                per year), based on   ton), based on CCM
               Facility                            Unit             with highest            Control               CCM/RCA cost      spreadsheet (for SDA/
                                                                    cost per ton                                   spreadsheet         WFGD) and 2023
                                                                                                                  calculations       version of RCA for
                                                                                                                                             DSI
--------------------------------------------------------------------------------------------------------------------------------------------------------
John Twitty...........................  1........................       2018-2022  DSI......................                  2392                  2928
                                                                        2018-2022  SDA......................                  2520                  7011
                                                                        2018-2022  WFGD.....................                  2520                  8205

[[Page 55159]]

 
Labadie...............................  1........................       2016-2020  DSI......................                  8177                  3609
                                                                        2016-2020  SDA......................                  9008                  4780
                                                                        2016-2020  WFGD.....................                  9008                  5038
                                        2........................       2016-2020  DSI......................                  8308                  3608
                                                                        2016-2020  SDA......................                  9023                  4774
                                                                        2016-2020  WFGD.....................                  9023                  5048
                                        3........................       2016-2020  DSI......................                  8497                  3606
                                                                        2016-2020  SDA......................                  9100                  4825
                                                                        2016-2020  WFGD.....................                  9100                  5010
                                        4........................       2016-2020  DSI......................                  8255                  3614
                                                                        2016-2020  SDA......................                  8692                  5019
                                                                        2016-2020  WFGD.....................                  8692                  5212
New Madrid............................  1........................       2018-2022  DSI......................                  5657                  3774
                                                                        2016-2020  SDA......................                  6104                  6444
                                                                        2016-2020  WFGD.....................                  6104                  6730
                                        2........................       2018-2022  DSI......................                  5953                  3739
                                                                        2018-2022  SDA......................                  6518                  6057
                                                                        2018-2022  WFGD.....................                  6518                  6322
Rush Island...........................  1........................       2018-2022  DSI......................                  7668                  3629
                                                                        2018-2022  SDA......................                  8264                  4732
                                                                        2018-2022  WFGD.....................                  8264                  5055
                                        2........................       2018-2022  DSI......................                  9159                  3580
                                                                        2018-2022  SDA......................                  9689                  4111
                                                                        2018-2022  WFGD.....................                 10114                  4209
Sikeston..............................  1........................       2018-2022  DSI......................                  5661                  3711
                                                                        2018-2022  SDA......................                  4809                  4292
                                                                        2018-2022  WFGD.....................                  4809                  4901
Thomas Hill...........................  1........................       2018-2022  DSI......................                  2006                  4119
                                                                        2018-2022  SDA......................                  2248                  7846
                                                                        2018-2022  WFGD.....................                  2248                  9201
                                        2........................       2016-2020  DSI......................                  2864                  3982
                                                                        2016-2020  SDA......................                  3210                  7559
                                                                        2016-2020  WFGD.....................                  3210                  8520
                                        3........................       2016-2020  DSI......................                  8316                  3658
                                                                        2016-2020  SDA......................                  9371                  5300
                                                                        2016-2020  WFGD.....................                  9371                  5338
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Table 5 below includes a summary of the EPA's cost effectiveness 
values for NOX controls.

                                        Table 5--Summary of the EPA's Cost Effectiveness Values for SCR and SNCR
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                         2021$ Cost
                                                                                                               NOX reduction (tons    effectiveness ($/
                                                                     Date range                                per year), based on   ton), based on CCM
               Facility                            Unit             with highest            Control               CCM/RCA cost       spreadsheet for SCR
                                                                    cost per ton                                   spreadsheet       and 2023 version of
                                                                                                                  calculations          RCA for SNCR
--------------------------------------------------------------------------------------------------------------------------------------------------------
John Twitty...........................  1........................       2018-2022  SCR......................                   359                 3,313
Labadie...............................  1........................       2018-2022  SCR......................                   948                24,483
                                                                        2018-2022  SNCR.....................                   302                 9,064
                                        2........................       2016-2020  SCR......................                   977                23,960
                                                                        2018-2022  SNCR.....................                   301                 9,130
                                        3........................       2018-2022  SCR......................                 1,106                21,747
                                                                        2018-2022  SNCR.....................                   359                 8,245
                                        4........................       2018-2022  SCR......................                   971                23,878
                                                                        2018-2022  SNCR.....................                   355                 8,306
New Madrid............................  1........................       2016-2020  SCR......................                10,691                   798
                                        2........................       2018-2022  SCR......................                 9,617                   832
Rush Island...........................  1........................       2016-2020  SCR......................                   869                23,960
                                                                        2018-2022  SNCR.....................                   208                11,181
                                        2........................       2018-2022  SCR......................                   763                26,659

[[Page 55160]]

 
                                                                        2018-2022  SNCR.....................                   130                15,427
Sikeston..............................  1........................       2016-2020  SCR......................                   598                15,520
Thomas Hill...........................  1........................       2016-2020  SCR......................                 3,237                   872
                                        2........................       2016-2020  SCR......................                 4,695                   876
                                        3........................       2016-2020  SCR......................                 4,999                 1,349
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The cost effectiveness of SCR is higher than SNCR for units that do 
not already have SCR installed. However, SCR delivers significant 
improvements in cost effectiveness as the tonnage of NOX 
removal increases due to the greater level of control of SCR over SNCR. 
The cost effectiveness of operating already installed SCR is extremely 
cost effective in comparison. As required in the Missouri source 
agreements submitted with the SIP, the EPA agrees that existing SCR 
should be required to be operated continuously on those units already 
equipped with SCR at the John Twitty, Thomas Hill, and New Madrid 
plants. Similar to the SO2 control summary, the EPA's 
revised cost effectiveness values for NOX controls are 
generally lower than the values presented by Missouri. For units that 
have relatively low inlet NOx values, post-combustion controls have 
lower removal efficiency and accordingly high cost effectiveness 
values. Similar to Missouri's assessment, the EPA finds the cost 
effectiveness values for installing new post combustion NOx controls 
are considerably higher than the highest cost effectiveness values 
found to be reasonable in the first planning period (the dataset 
underlying Missouri's cost threshold) and therefore may not be 
economically feasible for the second planning period.
    Importantly as part of this action, the EPA is not proposing that 
any given control technology or numeric emissions limit as evaluated in 
our TSD is necessary for a given unit. Rather, the EPA provided its own 
cost effectiveness calculations as evidence that Missouri's control 
decisions, that reject what may be otherwise reasonable control 
measures based solely on the state's selected cost threshold, are 
unreasonable.

Legal Deficiencies of Missouri's Consent Agreements

    To formalize the finding that existing measures are sufficient to 
make reasonable progress, Missouri entered into new consent agreements 
with each source selected and analyzed, with the exception of 
Mississippi Lime Company.\65\ The full source consent agreements are 
contained in Appendix E to the state's plan, available in the docket 
for this rulemaking.
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    \65\ For the Mississippi Lime Company, Missouri's plan appears 
to rely on current operational practices consistent with the 
parameters and limits in the Mississippi Lime Air Pollution Control 
Title V Permit to Operate instead of entering a new consent 
agreement. The EPA notes that Title V permit requirements are not 
permanent and therefore may not be relied upon for SIP requirements 
unless those components of the permit are submitted for inclusion 
into the SIP.
---------------------------------------------------------------------------

    In the new consent agreements, Missouri required that each 
facility's future fuel purchase be western sub-bituminous coal derived 
from the powder river basin. In addition, each facility agreed to 
operate any existing control devices at all times when burning coal in 
the boiler(s) except during periods of start-up, shutdown, or 
malfunction pursuant to 10 CSR 10-6.050. Through these consent 
agreements, the state required two facilities to run their existing 
selective catalytic reduction (SCR) technology when burning coal. The 
EPA reviewed the consent agreements and provided comment through the 
state's public process. The EPA commented on the significant 
approvability concerns related to the permanence and enforceability of 
the agreements. Specifically, the EPA commented that the agreements do 
not contain the necessary numerical emissions limitations associated 
with the operational requirements needed to be practically enforceable 
and, therefore, are not consistent with the relevant CAA and RHR 
requirements. For example, CAA section 110(a)(2)(A) states that each 
implementation plan submitted by a state shall ``include enforceable 
emission limitations and other control measures, means, or techniques . 
. . as well as schedules and timetables for compliance, as may be 
necessary or appropriate to meet the applicable requirements of this 
chapter.'' \66\ The EPA also commented that the sole requirement to 
burn western sub-bituminous coal still allows for a wide variability in 
the sulfur content of the coal and, therefore, emissions from the 
source. Similarly, the requirement to operate existing SCR technology 
without a particular numeric emissions limit or operating parameters 
allows for a wide variability in the control efficiency and operations 
of the SCR and, therefore, emissions from the source.\67\ Missouri did 
not amend the agreements in response to the EPA's formal comments.
---------------------------------------------------------------------------

    \66\ See CAA Section 110(a)(2) and section 110(a)(2)(A); see 
also Committee for a Better Arvin v. U.S. E.P.A., 786 F.3d 1169, 
1175 (9th Cir. 2015)
    \67\ The EPA provided variability analyses to demonstrate how 
these operational requirements without a numerical emissions limit 
do not practically limit emissions to an explicit level. See the 
EPA's comment letters on both the pre-hearing draft (dated September 
28, 2021) and the public notice draft (dated May 5, 2022) of 
Missouri's second planning period regional haze SIP.
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    The CAA requires that SIPs, including regional haze SIPs, contain 
elements sufficient to ensure emission limitations are practically 
enforceable. CAA section 110(a)(2) states that the monitoring, 
recordkeeping, and reporting provisions of states' SIPs must: ``(A) 
include enforceable emissions limitations and other control measures, 
means, or techniques (including economic incentives such as fees, 
marketable permits, and auctions of emissions rights), as well as 
schedules and timetables for compliance, as may be necessary or 
appropriate to meet the applicable requirements of this chapter; . . . 
(C) include a program to provide for the enforcement of the measures 
described in subparagraph (A), and regulation of the modification and 
construction of any stationary source within the areas covered by the 
plan as necessary to assure that national ambient air quality standards 
are achieved, including a permit program as required in parts C and D 
of this subchapter;. . . (F) require, as may be

[[Page 55161]]

prescribed by the Administrator--(i) the installation, maintenance, and 
replacement of equipment, and the implementation of other necessary 
steps, by owners or operators of stationary sources to monitor 
emissions from such sources, (ii) periodic reports on the nature and 
amounts of emissions and emissions-related data from such sources, and 
(iii) correlation of such reports by the State agency with any 
emissions limitations or standards established pursuant to this 
chapter, which reports shall be available at reasonable times for 
public inspection.'' \68\
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    \68\ 42 U.S.C. 7410(a)(2)(A), (C), and (F).
---------------------------------------------------------------------------

    Accordingly, 40 CFR part 51, subpart K, Source Surveillance, 
requires the SIP to provide for monitoring the status of compliance 
with the regulations in the SIP, including ``[p]eriodic testing and 
inspection of stationary sources,'' \69\ and ``legally enforceable 
procedures'' for recordkeeping and reporting.\70\ Furthermore, 40 CFR 
part 51, appendix V, Criteria for Determining the Completeness of Plan 
Submissions, states in section 2.2 that complete SIPs contain: ``(g) 
Evidence that the plan contains emission limitations, work practice 
standards and recordkeeping/reporting requirements, where necessary, to 
ensure emission levels''; and ``(h) Compliance/enforcement strategies, 
including how compliance will be determined in practice.'' \71\
---------------------------------------------------------------------------

    \69\ 40 CFR 51.212.
    \70\ Id. Sec.  51.214.
    \71\ 40 CFR part 51, appendix V.
---------------------------------------------------------------------------

    As previously mentioned, emission reduction measures that are 
necessary to make reasonable progress may be either new, additional 
control measures, or they may be the existing emission reduction 
measures that a source is already implementing. See 2019 Guidance at 
43; 2021 Clarifications Memo at 8-10. 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. 40 CFR 51.308(f)(2). The EPA proposes to find 
that the source agreements, submitted by Missouri to serve as the 
enforceable mechanism of the long-term strategy, do not meet the 
requirements of 40 CFR 51.308(f)(2) to include enforceable emissions 
limitations. Specifically, the source agreements do not contain the 
necessary numeric emissions limits to constitute a practically 
enforceable measure needed for reasonable progress as required by the 
RHR.
    The EPA also has concerns with the delayed compliance date in the 
agreements. Specifically, the consent agreements state that 
requirements of the agreements must be complied with ``Starting 180 
days after the approval of this agreement by the EPA as an attachment 
to Missouri's SIP for the second planning period of the RH program and 
consistent with the exemption and termination provisions set forth in 
the Consent Agreement.'' The EPA believes the agreements should include 
a reasonable compliance date based on the expected time necessary to 
implement controls or other operational requirements. The control 
requirements under the consent agreements are premised on operating 
existing installed emissions controls (for NOX) and for 
continued purchase and combustion of low sulfur coal (for 
SO2). The EPA has consistently found that such emissions 
control strategies are capable of being implemented in a matter of 
weeks, if not immediately given the nature of the requirements. E.g., 
88 FR 36654, 36720-22 (June 5, 2023); 86 FR 23054, 23088-89 (April 30, 
2021); and 81 FR 74504, 74561 (October 26, 2016). Instead, the state 
tied the effectiveness of these emissions reductions to an event that 
is irrelevant to substantive compliance with the regional haze program, 
i.e., the effective date of any final action by the EPA to approve the 
Consent Agreements into Missouri's SIP. This was improper; as a result 
of this provision, even at this point in time, Missouri has not imposed 
the requirements of the Consent Agreements on the affected sources and, 
under the plain terms of the Consent Agreements, to this day the 
covered sources are under no obligation to comply with them.
    The EPA further has concerns with certain other provisions 
(including but not limited to termination provisions) in the 
agreements. For example, the consent agreements contain provisions that 
allow for the state and the affected sources to modify them without 
following the statutorily-mandated process for SIP revisions and 
without requisite analysis by the EPA under CAA section 110(l). See CAA 
section 110(i); 110(l). While the EPA will allow for consent agreements 
or permitting requirements to be incorporated by reference into a 
state's SIP to meet SIP requirements, 50 CFR Pt. 51 App'x V, para. 
2.1.(b), it is important that the state provides that to the extent 
such provisions are approved and incorporated into the state's SIP, 
such provisions, as approved, cannot be modified by later changes made 
to the underlying agreements or permits outside of the SIP revision 
process. Once approved by the EPA into the SIP as meeting the 
applicable SIP requirements, only changes made through the statutory 
SIP revision process may modify the approved requirements of the 
state's SIP. In this instance, the terms of the Consent Agreements 
explicitly authorize the state and the affected sources to cancel the 
agreements in toto and without the EPA's approval of such a 
modification, which would in effect negate the emissions limitations in 
their entirety. This is antithetical to the requirement that SIP 
provisions be permanent and enforceable, and not changed except 
pursuant to the statutory and regulatory processes for SIP revisions.
    The consent agreements should not be unilaterally terminated by 
either the source or the state since the state has presented the 
consent agreements as necessary to achieve reasonable progress within 
the SIP revision submitted to the EPA for approval. Missouri is relying 
on Consent Agreements that include termination clauses that render the 
agreements and any contained requirements as not permanent and 
therefore not consistent with CAA and RHR requirements. Specifically, 
paragraph 12 of the consent agreements allows for termination of the 
agreement upon ``mutual written agreement of'' the source and the 
state. Paragraph 12 remains an unambiguous statement authorizing 
termination of the Agreements upon agreement of the parties to 
them.\72\ If the source and the MoDNR chose to exercise their rights in 
Paragraph 12, the Consent Agreements would be terminated without review 
or approval from the EPA and without input from the public, and the 
source would be under no obligation to comply. Therefore, the EPA 
concludes that paragraph 12 violates the CAA's prohibition on 
modification of SIPs outside the authorized SIP revision process 
pursuant to sections 110(i) and (l) of the CAA. SIP provisions cannot 
authorize a state to make changes in the EPA-approved and federally 
enforceable SIP requirements applicable to sources without going 
through the statutorily required SIP-revision process. The EPA refers 
to SIP provisions that purport to authorize states to make unilateral 
changes to existing SIP requirements as impermissible ``director's 
discretion'' provisions. See, e.g., 86 FR 15104, 15116 (March 22, 
2021). However, the EPA interprets the CAA to allow two

[[Page 55162]]

types of such provisions: (1) where the provision provides director's 
discretion for the state to make changes, but specifies that such 
changes have no effect for purposes of Federal law or alter SIP 
requirements unless and until the EPA approves the changes through a 
SIP revision pursuant to CAA requirements; or (2) where the provision 
provides director's discretion that is adequately bounded, such that at 
the time the EPA approves the SIP provision the Agency can evaluate it 
for compliance with applicable CAA requirements and evaluate the 
potential impacts of the state's exercise of that discretion. The EPA 
interprets CAA section 110(l) to allow SIP provisions with director's 
discretion of either type. In the case of an adequately bounded 
provision, the EPA considers such provisions consistent with section 
110(l) because, at the time of initial approval into the SIP, the 
Agency will already have evaluated the provision for compliance with 
applicable requirements and evaluated the potential impacts from 
exercise of the discretion. E.g., 86 FR 15116, March 22, 2021.
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    \72\ The courts would also likely interpret this language 
similarly to the EPA. See, e.g., New York v. U.S. EPA, 525 F.Supp.3d 
340, 356 (N.D.N.Y. 2021) (```[T]the scope of a consent decree must 
be discerned within its four corners . . . .''') (quoting 
Firefighters Local Union No. 1784 v. Stotts, 467 U.S. 561, 574 
(1984)).
---------------------------------------------------------------------------

    In Environ. Comm. Fl. Elec. Power v. EPA, 94 F.4th 77 (D.C. Cir. 
2024), the D.C. Circuit held that the EPA impermissibly issued a SIP 
call, under CAA section 110(k)(5), in its 2015 SSM SIP Action \73\ for 
certain SIP provisions applicable to emissions during SSM events, 
including certain director's discretion type provisions that the EPA 
had previously approved. However, the Court did not foreclose that some 
director's discretion provisions may be so unbounded as to interfere 
with the Agency's ability to predict the impact on compliance with the 
CAA's requirements. Id. At 111. Further, Enviro. Comm. Fl. Elec. Power 
concerns the EPA's authority to issue a SIP call for certain provisions 
that it previously approved and not the EPA's authority to approve or 
disapprove a SIP submission in the first instance. Compare CAA section 
110(k)(3) with (k)(5).
---------------------------------------------------------------------------

    \73\ See 80 FR 33840, June 12, 2015.
---------------------------------------------------------------------------

    Here, Paragraph 12 of the Consent Agreements in effect provides 
unbounded discretion to the state to eliminate the requirements, even 
though the MoDNR has submitted these Consent Agreements as necessary to 
satisfy Missouri's obligation to achieve reasonable progress in the 
regional haze program. Thus, Paragraph 12, which allows Missouri and 
its sources to agree between themselves to terminate these emissions 
control requirements at any time for any reason, is unacceptably too 
unbounded to meet regional haze obligations. Likewise, the EPA finds 
Paragraph 12 to be inconsistent with CAA section 110(i) and (l) because 
it permits the state not merely discretion to modify some provision 
within the overall operation of a broader regulatory scheme, but the 
ability to terminate the Agreements completely--i.e., the entirety of 
the emissions control program the state has put forward--at will. The 
EPA agrees that emissions controls on these sources are necessary 
(albeit not sufficient as discussed earlier in this section) for 
Missouri to achieve reasonable progress and it would be inappropriate 
for the EPA to approve as SIP provisions these Consent Agreements that 
the state could eliminate without undertaking the necessary SIP 
revision process mandated by the Act.
    Here, Paragraph 12 violates the anti-backsliding provisions of 
section 110(l) of the CAA, which requires that the EPA shall not 
approve any revision of a plan if the revision would interfere with any 
applicable requirement concerning attainment and reasonable further 
progress. 42 U.S.C. 7410(l). The termination provision would allow a 
unilateral amendment to the SIP, potentially removing emissions and 
pollution control limits without an evaluation of whether the removal 
would interfere with attainment or reasonable further progress or would 
interfere with any other applicable requirement of the Act.
    As mentioned above, the Consent Agreements include termination 
clauses that render them unenforceable depending on the nature of the 
action the EPA takes. Even if the EPA could have explored the 
possibility of a limited or partial approval of the consent agreements, 
it is not able to do this if doing so would render the emissions 
control measures established through the consent agreements 
unenforceable, by triggering the sources' ability to unilaterally 
withdraw from the agreements. Nor does the EPA have discretion to 
partially approve the consent agreements by not including within its 
approval those provisions of the Consent Agreements such as Paragraph 
13 (and others discussed in this section) that are not approvable. To 
do so would be to render the SIP revision more stringent than the state 
intended, which the EPA is not authorized to do. See Bethlehem Steel 
Corp. v. Gorsuch, 742 F.2d 1028 (7th Cir. 1984).
    Despite this, there remain multiple problematic provisions of the 
Consent Agreements that render them non-permanent and unenforceable. It 
is this language in the Agreements themselves, in addition to the 
possibility of a future modification to them, that renders them not 
approvable as a SIP revision for the purposes of ensuring reasonable 
progress under the regional haze program. However, because the consent 
agreements are otherwise not approvable, the EPA need not further 
evaluate the SSM, force majeure, or other exemption provisions of the 
agreements for compliance with the Act. Due to the identified flaws in 
the consent agreements as described above, the EPA cannot approve these 
consent agreements as a revision to Missouri's SIP nor as enforceable 
measures of the long-term strategy under 40 CFR 51.308(f)(2).
    For the reasons described in this section and in the TSD, the EPA 
proposes to find that Missouri failed to submit an approvable Long-Term 
Strategy because it (1) failed to reasonably ``evaluate and determine 
the emission reduction measures that are necessary to make reasonable 
progress by considering 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 
anthropogenic source of visibility impairment,'' as required by 40 CFR 
51.308(f)(2)(i); CAA section 169A(g)(1); (2) has not adequately 
supported its conclusions that existing measures satisfy the 
requirement to make reasonable progress; and (3) has not shown that 
further reductions of visibility impairing pollutants are not 
reasonable and has not adequately explained how its approach is 
consistent with the CAA's requirement to make reasonable progress. In 
addition, the state rejected otherwise reasonable control measures 
based primarily on the unreasonable justification and use of the 
selected cost threshold and on cost effectiveness calculations that do 
not fully align with EPA guidance. Further, Missouri has not included 
practically enforceable emissions limits to ensure that selected 
sources comply with the requirements constituting existing measures 
Missouri determined as needed to make reasonable progress. 
Specifically, the included source agreements do not contain explicit 
enforceable emissions limits associated with existing operations and 
include problematic termination or other exemption provisions, 
rendering them unenforceable and not permanent. Therefore, the EPA is 
proposing to disapprove Missouri's Long-Term Strategy as required by 40 
CFR 51.308(f)(2).

[[Page 55163]]

3. Additional Long-Term Strategy Requirements
    The consultation requirements of Sec.  51.308(f)(2)(ii) provides 
that states must consult with other states that are reasonably 
anticipated to contribute to visibility impairment in a Class I area to 
develop coordinated emission management strategies containing the 
emission reductions measures that are necessary to make reasonable 
progress. Section 51.308(f)(2)(ii)(A) and (B) require states to 
consider the emission 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.
    In Appendix G-3, Missouri included documentation of its 
consultation with other states and responses to requests from other 
states as it relates to the state's development of its long-term 
strategy. However, because these elements are not separable from the 
overall requirement at 40 CFR 51.308(f)(2) to develop an enforceable 
long-term strategy, the EPA accordingly proposes to disapprove all 
elements of Missouri's regional haze SIP submission as it relates to 
the 40 CFR 51.308(f)(2) rule requirements.
    The documentation requirement of Sec.  51.308(f)(2)(iii) provides 
that states may meet their obligations to document the technical bases 
on which they are relying to determine the emission reductions measures 
that are necessary to make reasonable progress through an RPO, as long 
as the process has been ``approved by all State participants.''
    Section 51.308(f)(2)(iii) also requires that the emissions 
information considered to determine the measures that are necessary to 
make reasonable progress include information on emissions for the most 
recent year for which the state has submitted triennial emissions data 
to the EPA (or a more recent year), with a 12-month exemption period 
for newly submitted data.
    Missouri included emissions information from the most recent 
national emissions inventory (NEI) reporting year in its submittal. 
Section 4.1.1 of Missouri's submittal details how the state meets the 
emissions inventory requirement. Missouri also includes additional 
information on the inventory development in Appendix A to the state's 
submittal. However, because these elements are not separable from the 
overall requirement of 40 CFR 51.308(f)(2) to develop an enforceable 
long-term strategy, the EPA accordingly proposes to disapprove all 
elements of Missouri's regional haze SIP submission as it relates to 
the 40 CFR 51.308(f)(2) rule requirements.

F. Reasonable Progress Goals

    Section 51.308(f)(3) contains the requirements pertaining to RPGs 
for each Class I area. 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 emission 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 RPG 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 Sec.  
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 emission 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 robust demonstration.
    In Chapters 5 and 6 of Missouri's SIP submission, the state 
describes the process followed to determine the RPGs for each of the 
state's Class I areas. Missouri relied on the EPA's modeling of 
projected 2028 visibility conditions as the basis for establishing the 
RPGs.\74\ Specifically, Missouri established an RPG of 17.44 dv for 
Hercules-Glades and 18.88 dv for Mingo. Each of these RPGs is slightly 
below the 2028 point on the uniform rate of progress line or glidepath 
(18.82 dv for Hercules-Glades and 19.48 dv for Mingo), meaning the 
state did not trigger the provision to provide a robust demonstration 
as just described.
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    \74\ See the EPA's September 2019 memorandum titled, 
``Availability of Modeling Data and Associated Technical Support 
Document for the EPA's Updated 2028 Visibility Air Quality 
Modeling.'' https://www.epa.gov/sites/default/files/2019-10/documents/updated_2028_regional_haze_modeling-tsd-2019_0.pdf.
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    At the time Missouri submitted its SIP, the provision triggering a 
robust demonstration did not apply because the states with Class I 
areas that are affected by Missouri sources did not submit any RPGs 
above the URP. Because we are proposing to disapprove certain elements 
of Missouri's SIP, if Missouri chooses to submit a revised SIP to the 
EPA, the state should re-evaluate whether the requirement of 40 CFR 
51.308(f)(3)(iii) applies to Missouri.
    The RPGs should reflect the visibility conditions as a result of 
the enforceable emissions limitations and other measures in the state's 
long-term strategy as required under 40 CFR 51.308(f)(2). Because the 
EPA is proposing to disapprove Missouri's long-term strategy under 40 
CFR 51.308(f)(2) through this proposed rulemaking, the EPA is also 
proposing to disapprove the RPGs under 40 CFR 51.308(f)(3). If Missouri 
elects to submit a new long-term strategy, the state will also need to 
provide new RPGs associated with the new long-term strategy.

G. 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 subsection 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 Interagency Monitoring of Protected Visual Environments (IMPROVE) 
network. As noted in Chapter 7 of Missouri's submittal, Missouri 
continues to rely on participation in the IMPROVE network for its two 
Class I areas monitoring strategies.
    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. In Chapter 7 of the state plan,

[[Page 55164]]

Missouri describes how the two IMPROVE program monitors in Missouri are 
sufficient for determining progress in reducing visibility in the 
Missouri Class I areas due to their locations.
    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. In Chapter 7 of the state plan, Missouri 
explains that the assessments of visibility impairment and progress in 
reducing visibility impairment at Missouri's two Class I areas, and at 
Class I areas in other states that Missouri's emissions may affect, in 
the future will use the revised IMPROVE algorithm (Pitchford, 2007) and 
will use data as prescribed in the EPA's RHR (40 CFR part 51, subpart 
P--Visibility Protection). The assessment will follow, as appropriate, 
EPA guidance including Guidance on Regional Haze State Implementation 
Plans for the Second Implementation Period (EPA, 2019) and Technical 
Guidance on Tracking Visibility Progress for the Second Implementation 
Period of the Regional Haze Program (EPA, 2018).
    Section 51.308(f)(6)(iii) does not apply to Missouri, as it has 
Class I areas.
    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. The monitoring 
strategy for Missouri relies upon the continued availability of the 
IMPROVE network. The IMPROVE monitor for the Hercules-Glades Wilderness 
Area (indicated as HEGL in the IMPROVE monitoring network database) is 
operated and maintained by the FS and is contained within the Mark 
Twain National Forest. The IMPROVE monitor for the Mingo National 
Wildlife Refuge (indicated as MING in the IMPROVE monitoring network 
database) is operated and maintained by the FWS. Since the state does 
not collect or handle IMPROVE data directly, the state commits to 
continue to participate in the IMPROVE Visibility Information Exchange 
Web System (VIEWS). The state considers VIEWS to be a core part of the 
overall IMPROVE program and will report IMPROVE data from the two Class 
I areas in Missouri to the EPA using the VIEWS web system.
    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. 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. In Chapter 4.1 of the 
state plan, Missouri notes that it complies with 40 CFR part 51, 
subpart A, Air Emissions Reporting Requirements (AERR) to develop and 
submit periodic emissions inventories to the EPA every three years. Per 
the AERR, the state submitted to the EPA's National Emissions Inventory 
(NEI) 2011, 2014, and 2017 periodic emissions inventories as a 
comprehensive and detailed estimate of statewide air emissions. The 
reported pollutants include NOX, VOC, carbon monoxide (CO), 
SO2, NH3, PM2.5, and PM10. 
The type of emissions sources, amount of each pollutant emitted, and 
the types of processes and control devices employed at each facility or 
source category are identified in the inventory. The AERR emissions 
inventories are derived from estimates developed for four general 
categories of anthropogenic emissions sources: point, area or nonpoint, 
nonroad mobile, and onroad mobile. Chapter 4.1 of the state plan 
discusses general emissions inventory development for each of the 
anthropogenic source categories. Appendix A to the state's plan 
describes how the state developed the most recent emissions inventory, 
2017, including compilation and submission to the NEI through the EPA's 
Emissions Inventory System (EIS). The EPA proposes to find that 
Missouri satisfies the requirements of 40 CFR 51.308(f)(6)(v) through 
compliance with the AERR.
    For the reasons described in this section, the EPA proposes to find 
Missouri's plan satisfies the requirements of 40 CFR 51.308(f)(6) and 
proposes to approve this element of the state plan.

H. 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) through (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 emission 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 emission information is reported. Finally, 
Sec.  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.
    Missouri addresses the requirements of 40 CFR 51.308(g)(1) through 
(5) in Chapter 8 of the state's submittal. To meet the requirement of 
40 CFR 51.308(g)(1), the state points to Chapter 4 of the submittal 
which details the existing measures that control emissions in the state 
including Federal, state, stationary, and mobile source emissions 
measures. To address 40 CFR 51.308(g)(2), the state refers to the 
emissions inventory included in Chapter 4, section 4.1.1.4, Tables 13 
and 14, which depict the NOX and SO2 emissions 
trends by source type and emission category for 2011, 2014, and 2017. 
To meet the requirement of 40 CFR 51.308(g)(3), the state evaluated the 
haze index and annual light extinction values for each IMPROVE site in 
Missouri between 2000 and 2018 and concluded that visibility conditions 
for the two Class I areas in Missouri have improved and are below the 
uniform rate of progress line. For 40 CFR 51.308(g)(4), the state 
refers to the emissions inventory in Chapter 4 of the submittal to show 
the change in emissions of pollutants contributing to

[[Page 55165]]

visibility impairment over time. To satisfy 40 CFR 51.308(g)(5), 
Missouri notes that most visibility impairing pollutants have decreased 
since the last planning period submittal with the exception of ammonia 
(NH3). Missouri refers to Chapter 4 of which details the 
existing measures that have resulted in those emissions decreases such 
as Federal, state or mobile source emissions programs.
    The EPA finds that Missouri satisfactorily refers to the included 
emissions inventory, describes the emissions trends or changes as well 
as the visibility trends for their two Class I Areas to meet the 
requirements contained in 40 CFR 51.308(g)(1) through (5). Therefore, 
the EPA proposes to approve Missouri's plan as meeting the requirements 
of 40 CFR 51.308(g)(1) through (5).

I. Requirements for State and Federal Land Manager Coordination

    Section 169A(d) of the CAA 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.''
    Section 51.308(i)(2)'s FLM consultation provision requires a state 
to provide FLMs with an opportunity for consultation that is early 
enough in the state's policy analyses of its emission 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. Section 51.308(i)(4) requires states to provide for 
ongoing consultation between the state and FLM's on the implementation 
of the given plan and on development of future plan revisions or 
progress reports.
    Missouri included summaries of their consultation with various FLMs 
as well as responses to their comments in Appendix G-2 to their 
submittal. On July 30, 2021, Missouri shared the pre-proposal draft of 
its second planning period regional haze plan with the FS, the FWS, the 
NPS, and the EPA. On September 21, 2021, Missouri held a formal 
consultation call with the three FLM agencies as well as the EPA.
    However, because the EPA is proposing to disapprove certain 
elements of Missouri's SIP, namely the long-term strategy under 40 CFR 
51.308(f)(2) and the reasonable progress goals under 40 CFR 
51.308(f)(3), the EPA is also proposing to disapprove the FLM 
consultation requirements under 40 CFR 51.308(i). The requirements 
contained in 40 CFR 51.308(i): (i)(2), (i)(3), and (i)(4) are not 
separable from one another. While Missouri did take administrative 
steps to provide the FLMs the requisite opportunity to review and 
provide feedback on the state's draft plan, the EPA cannot approve the 
requirements under 40 CFR 51.308(i) because Missouri'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. In 
addition, if the EPA were to finalize the partial approval and partial 
disapproval of Missouri's SIP, 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 requirements 
under 40 CFR 51.308(i). Therefore, the EPA proposes to disapprove the 
respective elements of Missouri's plan as not meeting the requirements 
of 40 CFR 51.308(i).

VI. What action is the EPA proposing to take?

    The EPA is proposing to partially approve and partially disapprove 
the Missouri SIP revision relating to Regional Haze for the second 
planning period received on August 26, 2022, pursuant to section 
110(k)(3) of the CAA and 40 CFR (f)(3)(iv). The EPA is proposing to 
approve the elements of Missouri's plan related to requirements 
contained in 40 CFR 51.308(f)(1), (f)(5), (f)(6), and (g)(1) through 
(g)(5). The EPA is proposing to disapprove the elements of Missouri's 
plan related to requirements contained in 40 CFR 51.308(f)(2) and 
(f)(3), and (i). The EPA is not proposing a Federal Implementation Plan 
(FIP) at this time. If the EPA finalizes the disapproval, that will 
start a two-year clock for the EPA to propose and finalize a FIP.\75\ 
However, the EPA is already on a two-year FIP clock that began 
September 29, 2022, when the EPA published a finding that Missouri 
failed to submit the required regional haze plan for the second 
planning period by the regulatory deadline.\76\ We are soliciting 
comments on this proposed action. Final rulemaking will occur after 
consideration of any comments.
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    \75\ The EPA is only stating this second FIP clock as a factual 
result that a disapproval leads to a FIP clock. The FIP clock from 
the finding of failure to submit is primary and the FIP clock from a 
future disapproval does not supersede or reset the FIP clock from 
the finding of failure to submit.
    \76\ See 87 FR 52856, August 30, 2022.
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VII. Environmental Justice Considerations

    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.'' \77\ Recognizing the 
importance of these considerations to local communities, the EPA 
conducted an environmental justice screening analysis around the 
location of the facilities associated with this action to identify 
potential environmental stressors on these communities and the 
potential impacts of this action. However, the EPA is providing the 
information associated with this analysis for informational purposes 
only. The information provided herein is not a basis of the proposed 
action. The EPA conducted the screening analyses using EJScreen, an EJ 
mapping and screening tool that provides the EPA with a nationally 
consistent dataset and approach for combining various environmental and 
demographic indicators.\78\ The EJScreen tool presents these indicators 
at a Census block group (CBG) level or a larger user specified 
``buffer'' area that covers multiple CBGs.\79\ An individual CBG is a 
cluster of contiguous blocks within the same census tract and generally 
contains

[[Page 55166]]

between 600 and 3,000 people. EJScreen is not a tool for performing in-
depth risk analysis, but is instead a screening tool that provides an 
initial representation of indicators related to EJ and is subject to 
uncertainty in some underlying data (e.g., some environmental 
indicators are based on monitoring data which are not uniformly 
available; others are based on self-reported data).\80\ For 
informational purposes, we have summarized EJScreen data within larger 
``buffer'' areas covering multiple block groups and representing the 
average resident within the buffer areas surrounding the facilities 
selected by Missouri for further control analysis. EJScreen 
environmental indicators help screen for locations where residents may 
experience a higher overall pollution burden than would be expected for 
a block group with the same total population in the U.S. These 
indicators of overall pollution burden include estimates of ambient 
PM2.5 and ozone concentration, a score for traffic proximity 
and volume, percentage of pre-1960 housing units (lead paint 
indicator), and scores for proximity to Superfund sites, risk 
management plan (RMP) sites, and hazardous waste facilities.\81\ 
EJScreen also provides information on demographic indicators, including 
percent low-income, communities of color, linguistic isolation, and 
less than high school education. The EPA prepared EJScreen reports 
covering buffer areas of approximately 6-mile radii around the 
facilities selected by Missouri for further analysis. For each 
facility, the EPA indicates in the following statements whether there 
is an environmental or socioeconomic indicator for the selected source 
area above the 80th percentile nationally. These indicators are 
displayed in the table on page 3 of each report. The report for New 
Madrid Power Plant showed socioeconomic indicators greater than the 
80th national percentile for low income.\82\ The report for Sikeston 
showed environmental and socioeconomic indicators greater than the 80th 
national percentiles for wastewater discharge and low life expectancy. 
The report for John Twitty showed environmental indicators greater than 
the 80th national percentiles for wastewater discharge and superfund 
proximity. The report for Thomas Hill showed environmental indicators 
greater than the 80th national percentiles for wastewater discharge. 
The report for Mississippi Lime showed environmental indicators greater 
than the 80th national percentiles for risk management plan facility 
proximity. Other facility reports not mentioned here do not include 
environmental or socioeconomic indicators greater than the 80th 
national percentiles. The full, detailed EJScreen reports for each 
facility selected by Missouri for further analysis are provided in the 
docket for this rulemaking. This action is proposing to disapprove 
certain elements of Missouri's second planning period regional haze 
plan as not meeting the requirements of the CAA or the EPA's RHR. 
Exposure to PM and SO2 is associated with significant public 
health effects. Short-term exposures to SO2 can harm the 
human respiratory system and make breathing difficult. People with 
asthma, particularly children, are sensitive to these effects of 
SO2.\83\ Exposure to PM can affect both the lungs and heart 
and is associated with: premature death in people with heart or lung 
disease, nonfatal heart attacks, irregular heartbeat, aggravated 
asthma, decreased lung function, and increased respiratory symptoms, 
such as irritation of the airways, coughing or difficulty breathing. 
People with heart or lung diseases or conditions, children, and older 
adults are the most likely to be affected by PM exposure.\84\ This 
action which proposes to partially disapprove Missouri's regional haze 
plan, if finalized, will not directly result in a change to emissions 
or air quality. There is nothing in the record which indicates that 
this proposed action, if finalized, would have disproportionately high 
or adverse human health or environmental effects on communities with 
environmental justice concerns.
---------------------------------------------------------------------------

    \77\ See https://www.epa.gov/environmentaljustice/learn-about-environmentaljustice.
    \78\ The EJSCREEN tool is available at https://www.epa.gov/ejscreen.
    \79\ See https://www.census.gov/programssurveys/geography/about/glossary.html.
    \80\ In addition, EJSCREEN relies on the five-year block group 
estimates from the U.S. Census American Community Survey. The 
advantage of using five-year over single-year estimates is increased 
statistical reliability of the data (i.e., lower sampling error), 
particularly for small geographic areas and population groups. For 
more information, see https://www.census.gov/content/dam/Census/library/publications/2020/acs/acs_general_handbook_2020.pdf.
    \81\ For additional information on environmental indicators and 
proximity scores in EJSCREEN, see ``EJSCREEN Environmental Justice 
Mapping and Screening Tool: EJSCREEN Technical Documentation,'' 
Chapter 3 and Appendix C (September 2019) at https://www.epa.gov/sites/default/files/2021-04/documents/ejscreen_technical_document.pdf.
    \82\ For a place at the 80th percentile nationwide, that means 
20% of the U.S. population has a higher value. The EPA identified 
the 80th percentile filter as an initial starting point for 
interpreting EJScreen results. The use of an initial filter promotes 
consistency for EPA programs and regions when interpreting screening 
results.
    \83\ See https://www.epa.gov/so2-pollution/sulfurdioxide-basics#effects.
    \84\ See https://www.epa.gov/pm-pollution/healthand-environmental-effects-particulate-matter-pm.
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VIII. Statutory and Executive Order Reviews

    Under the CAA, the Administrator is required to approve a SIP 
submission that complies with the provisions of the CAA and applicable 
Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in 
reviewing SIP submissions, the EPA's role is to review state choices, 
and approve those choices if they meet the minimum criteria of the CAA. 
Accordingly, this proposed action partially approves and partially 
disapproves state law as meeting Federal requirements and does not 
impose additional requirements beyond those imposed by state law.

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'' under the 
terms of Executive Order 12866 (58 FR 51735, October 4, 1993) and is 
therefore not subject to review under Executive Orders 12866, 13563 (76 
FR 3821, January 21, 2011) and 14094 (88 FR 21879, April 11, 2023).

B. Paperwork Reduction Act (PRA)

    This rule does not impose an information collection burden under 
the provisions of the Paperwork Reduction Act of 1995 (44 U.S.C. 3501 
et seq.).

C. Regulatory Flexibility Act (RFA)

    This action merely proposes to partially approve and partially 
disapprove state law as meeting or not meeting Federal requirements and 
imposes no additional requirements beyond those imposed by state law. 
Accordingly, the Administrator certifies that this rule will not have a 
significant economic impact on a substantial number of small entities 
under the Regulatory Flexibility Act (5 U.S.C. 601 et seq.).

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

[[Page 55167]]

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: Consultation and Coordination With Indian 
Tribal Governments

    This action does not have tribal implications as specified in 
Executive Order 13175. This action does not apply on any Indian 
reservation land, any other area where the EPA or an Indian tribe has 
demonstrated that a tribe has jurisdiction, or non-reservation areas of 
Indian country. This rule does not have tribal implications and will 
not impose substantial direct costs on tribal governments or preempt 
tribal law as specified by Executive Order 13175 (65 FR 67249, November 
9, 2000).

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. This action is not subject to 
Executive Order 13045 because it merely proposes to disapprove a SIP 
submission as not meeting the CAA.

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

    This rulemaking does not involve technical standards. Therefore, 
the EPA is not considering the use of any voluntary consensus 
standards.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations (59 FR 7629, 
February 16, 1994)

    Executive Order 12898 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 Missouri 
Department of Natural Resources did not evaluate environmental justice 
considerations as part of its SIP submittal; the CAA and applicable 
implementing regulations neither prohibit nor require such an 
evaluation. The EPA performed an environmental justice analysis, as is 
described above in the section titled, ``Environmental Justice 
Considerations.'' The analysis was done for the purpose of providing 
additional context and information about this rulemaking to the public, 
not as a basis of the action. Due to the nature of the action being 
taken here, merely proposing to partially approve and partially 
disapprove the state's plan as meeting requirements of the Act or EPA 
regulations, this action will not directly impact air quality or 
emissions in the affected areas. 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, Carbon monoxide, 
Incorporation by reference, Intergovernmental relations, Lead, Nitrogen 
dioxide, Ozone, Particulate matter, Reporting and recordkeeping 
requirements, Sulfur oxides, Volatile organic compounds.

    Dated: June 27, 2024.
Meghan A. McCollister,
Regional Administrator, Region 7.

    For the reasons stated in the preamble, the EPA proposes to amend 
40 CFR part 52 as set forth below:

PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

0
1. The authority citation for part 52 continues to read as follows:

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

Subpart AA--Missouri

0
2. In Sec.  52.1320, the table in paragraph (e) is amended by adding 
the entry ``(86)'' in numerical order to read as follows:


Sec.  52.1320  Identification of plan.

* * * * *
    (e) * * *

                               EPA-Approved Missouri Nonregulatory SIP Provisions
----------------------------------------------------------------------------------------------------------------
                                        Applicable
    Name of nonregulatory SIP         geographic or          State       EPA approval date       Explanation
             revision               nonattainment area  submittal date
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
(86) Missouri Regional Haze Plan   Statewide..........         8/26/22  [Date of             This action
 for the Second Implementation                                           publication of the   approves the plan
 Period.                                                                 final rule in the    as only meeting
                                                                         Federal Register],   the requirements
                                                                         [Federal Register    of 40 CFR
                                                                         citation of the      51.308(f)(1),
                                                                         final rule].         (f)(5), (f)(6),
                                                                                              and (g)(1) through
                                                                                              (g)(5). This
                                                                                              action disapproves
                                                                                              the plan as not
                                                                                              meeting the
                                                                                              requirements of 40
                                                                                              CFR 51.308(f)(2),
                                                                                              (f)(3), and (i).
----------------------------------------------------------------------------------------------------------------

0
3. Amend Sec.  52.1339 by adding paragraph (b) to read as follows:


Sec.  52.1339  Visibility protection.

* * * * *
    (b) The requirements of section 169A of the Clean Air Act are not 
fully met for the second implementation period

[[Page 55168]]

because the plan does not include approvable measures for meeting the 
requirements of 40 CFR 51.308(f)(2), (f)(3), and (i) for protection of 
visibility in mandatory Class I Federal areas. The plan does meet the 
requirements of 40 CFR 51.308(f)(1), (f)(5), (f)(6), and (g)(1) through 
(g)(5).

[FR Doc. 2024-14612 Filed 7-2-24; 8:45 am]
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