[Federal Register Volume 89, Number 149 (Friday, August 2, 2024)]
[Proposed Rules]
[Pages 63258-63279]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-16502]



[[Page 63257]]

Vol. 89

Friday,

No. 149

August 2, 2024

Part II





Environmental Protection Agency





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40 CFR Part 52





Air Plan Approval; IA; Regional Haze State Implementation Plan for the 
Second Implementation Period; Proposed Rule

  Federal Register / Vol. 89 , No. 149 / Friday, August 2, 2024 / 
Proposed Rules  

[[Page 63258]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R07-OAR-2024-0313; FRL-12096-01-R7]


Air Plan Approval; IA; Regional Haze State Implementation Plan 
for the Second Implementation Period

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve the regional haze state implementation plan (SIP) revision 
submitted by Iowa on August 15, 2023, as satisfying applicable 
requirements under the Clean Air Act (CAA) and EPA's Regional Haze Rule 
(RHR) for the program's second implementation period. Iowa's SIP 
submission addresses the requirement that states must periodically 
revise their long-term strategies for making reasonable progress 
towards the national goal of preventing any future, and remedying any 
existing, anthropogenic impairment of visibility, including regional 
haze, in mandatory Class I Federal areas. The SIP submission also 
addresses other applicable requirements for the second implementation 
period of the regional haze program. The EPA is taking this action 
pursuant to the CAA.

DATES: Written comments must be received on or before September 3, 
2024.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R07-
OAR-2024-0313 at https://www.regulations.gov. For comments submitted at 
Regulations.gov, follow the online instructions for submitting 
comments. Once submitted, comments cannot be edited or removed from 
Regulations.gov. For either manner of submission, the EPA may publish 
any comment received to its public docket. Do not submit electronically 
any information you consider to be confidential business information 
(CBI) or other information whose disclosure is restricted by statute. 
Multimedia submissions (audio, video, etc.) must be accompanied by a 
written comment. The written comment is considered the official comment 
and should include discussion of all points you wish to make. The EPA 
will generally not consider comments or comment contents located 
outside of the primary submission (i.e., on the web, cloud, or other 
file sharing system). For additional submission methods, please contact 
the person identified in the FOR FURTHER INFORMATION CONTACT section. 
For the full EPA public comment policy, information about CBI or 
multimedia submissions, and general guidance on making effective 
comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Bethany Olson, U.S. Environmental 
Protection Agency, Region 7 Office, Air Permitting and Planning Branch, 
11201 Renner Boulevard, Lenexa, Kansas 66219; telephone number: (913) 
551-7905; 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. Calculations of Baseline, Current, and Natural Visibility 
Conditions; Progress to Date; and the Uniform Rate of Progress
    C. Long-Term Strategy for Regional Haze
    D. Reasonable Progress Goals
    E. Monitoring Strategy and Other State Implementation Plan 
Requirements
    F. Requirements for Periodic Reports Describing Progress Towards 
the Reasonable Progress Goals
    G. Requirements for State and Federal Land Manager Coordination
V. The EPA's Evaluation of Iowa's Regional Haze Submission for the 
Second Implementation Period
    A. Background on Iowa's First Implementation Period SIP 
Submission
    B. Iowa'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
    a. Iowa's Source Selection and Four Factor Analysis
    b. The EPA's Evaluation of Iowa's Emissions Reduction Measures 
and Compliance With Sec.  51.308(f)(2)(i)
    c. 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?
VII. Incorporation by Reference
VIII. Environmental Justice Considerations
IX. Statutory and Executive Order Reviews

I. Written Comments

    Submit your comments, identified by Docket ID No. EPA-R07-OAR-2024-
0313, 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 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 15, 2023, the Iowa Department of Natural Resources (IDNR) 
submitted a plan to satisfy the regional haze program requirements 
pursuant to CAA sections 169A and 40 CFR 51.308. The EPA is proposing 
to approve Iowa's Regional Haze plan for the second planning period. 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, the National Parks Service (NPS), the U.S. 
Fish and Wildlife Service (FWS), the U.S. Forest Service (USFS), 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 and in the 
technical support document (TSD) included in this docket, the EPA is 
proposing to find that Iowa has submitted a Regional Haze plan that

[[Page 63259]]

meets the Regional Haze requirements for the second planning period. 
The State's submission can be found in the docket for this action.

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.\1\ 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 Regional Haze Rule (RHR), 
codified at 40 CFR 51.308,\2\ 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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    \1\ 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.
    \2\ 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 
particulate matter (PM) (e.g., sulfates, nitrates, organic carbon, 
elemental carbon, and soil dust) and their precursors (e.g., sulfur 
dioxide (SO2), nitrogen oxides (NOX), and, in 
some cases, volatile organic compounds (VOC) and ammonia 
(NH3)). Fine particle precursors react in the atmosphere to 
form 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.\3\
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    \3\ There are several ways to measure the amount of visibility 
impairment, i.e., haze. One such measurement is the deciview, which 
is the principal metric used by the RHR. Under many circumstances, a 
change in one deciview will be perceived by the human eye to be the 
same on both clear and hazy days. The deciview is unitless. It is 
proportional to the logarithm of the atmospheric extinction of 
light, which is the perceived dimming of light due to its being 
scattered and absorbed as it passes through the atmosphere. 
Atmospheric light extinction (b\ext\) is a metric used for 
expressing visibility and is measured in inverse megameters 
(Mm-1). The EPA's Guidance on Regional Haze State 
Implementation Plans for the Second Implementation Period (``2019 
Guidance'') offers the flexibility for the use of light extinction 
in certain cases. Light extinction can be simpler to use in 
calculations than deciviews, since it is not a logarithmic function. 
See, e.g., 2019 Guidance 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); \4\ see also 40 CFR 
51.308(b), (f) (establishing submission dates for iterative regional 
haze SIP revisions) (64 FR 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 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.\5\ Id. at 
35721.
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    \4\ 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).
    \5\ In addition to each of the fifty states, the EPA also 
concluded that the Virgin Islands and District of Columbia must also 
submit regional haze SIPs because they either contain a Class I area 
or contain sources whose emissions are reasonably anticipated to 
contribute regional haze in a Class I area. See 40 CFR 51.300(b), 
(d)(3).
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    Much of the focus in the first implementation period of the 
regional haze program, which ran from 2007 through 2018, was on 
satisfying states' BART obligations. First implementation period SIPs 
were additionally required to contain long-term strategies for making 
reasonable progress toward the national visibility goal, of which BART 
is one component. The core required elements for the first 
implementation period SIPs (other than BART) are laid out in 40 CFR 
51.308(d). Those provisions required that states containing Class I 
areas establish reasonable progress goals (RPGs) that are measured in 
deciviews and reflect the anticipated visibility conditions at the end 
of the implementation period including from implementation of states' 
long-term strategies. The first planning period RPGs were required to 
provide for an improvement in visibility for the most impaired days 
over the period of the implementation plan and ensure no degradation in 
visibility for the least impaired days over the same period. In 
establishing the RPGs for any Class I area in a state, the state was 
required to consider four statutory factors: the costs of compliance, 
the time necessary for compliance, the energy and non-air quality 
environmental impacts of compliance, and the remaining useful life of 
any potentially affected sources. 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

[[Page 63260]]

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.\6\ 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), (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) 
\7\ (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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    \6\ 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 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).
    \7\ 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'').\8\ 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'').\9\ 
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''),\10\ 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'').\11\
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    \8\ 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).
    \9\ 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).
    \10\ 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).
    \11\ Recommendation for the Use of Patched and Substituted Data 
and Clarification of Data Completeness for Tracking Visibility 
Progress for the Second Implementation Period of the Regional Haze 
Program. https://www.epa.gov/visibility/memo-and-technical-addendum-ambient-data-usage-and-completeness-regional-haze-program. The EPA 
Office of Air Quality Planning and Standards, Research Triangle Park 
(June 3, 2020).
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    As explained in the 2021 Clarifications Memo, the EPA intends the 
second implementation period of the regional haze program to secure 
meaningful reductions in visibility impairing pollutants that build on 
the significant progress states have achieved to date. The Agency also 
recognizes that analyses regarding reasonable progress are state-
specific and that, based on states' and sources' individual 
circumstances, what constitutes reasonable reductions in visibility 
impairing pollutants will vary from state-to-state. While there exist 
many opportunities for states to leverage both ongoing and upcoming 
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 and 
Prevention of Significant Deterioration programs, as further emission 
reductions may be necessary to adequately protect visibility in Class I 
areas throughout the country.\12\
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    \12\ 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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[[Page 63261]]

B. Roles of Agencies in Addressing Regional Haze

    Because the air pollutants and pollution affecting visibility in 
Class I areas can be transported over long distances, successful 
implementation of the regional haze program requires long-term, 
regional coordination among multiple jurisdictions and agencies that 
have responsibility for Class I areas and the emissions that impact 
visibility in those areas. To address regional haze, states need to 
develop strategies in coordination with one another, considering the 
effect of emissions from one jurisdiction on the air quality in 
another. Five regional planning organizations (RPOs),\13\ which include 
representation from state and Tribal governments, the EPA, and FLMs, 
were developed in the lead-up to the first implementation period to 
address regional haze. RPOs evaluate technical information to better 
understand how emissions from State and Tribal land impact Class I 
areas across the country, pursue the development of regional strategies 
to reduce emissions of particulate matter and other pollutants leading 
to regional haze, and help states meet the consultation requirements of 
the RHR.
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    \13\ 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 described above, that Iowa 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 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, Kansas, Louisiana, 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 USFS.
    Iowa also benefited from planning activities of the Lake Michigan 
Air Directors Consortium (LADCO). Like CenSARA, LADCO is a 
collaborative effort to improve air quality in the Great Lakes Region 
of the United States. Though Iowa is not a member State of LADCO, Iowa 
does impact LADCO State Class I Areas in Minnesota and Michigan, and 
utilized resources available through LADCO for the second planning 
period, as referenced throughout the submission.

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

    Under the CAA and 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 (3) generally mirroring the 
order of the steps in the reasonable progress analysis \14\ and (f)(4) 
through (6) containing additional, related requirements. Broadly 
speaking, a state first must identify the Class I areas within the 
state and determine the Class I areas outside the state in which 
visibility may be affected by emissions from the state. These are the 
Class I areas that must be addressed in the state's long-term strategy. 
See 40 CFR 51.308(f) introductory text, (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'' \15\ 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. 
Those measures are then incorporated into the state's long-term 
strategy. After a state has developed its long-term strategy, it then 
establishes RPGs for each Class I area within its borders by modeling 
the visibility impacts of all reasonable progress controls at the end 
of the second implementation period, i.e., in 2028, as well as the 
impacts of other requirements of the CAA. The RPGs include reasonable 
progress controls not only for sources in the state in which the Class 
I area is located, but also for sources in other states that contribute 
to visibility impairment in that area. The RPGs are then compared to 
the baseline visibility conditions and the URP to ensure that progress 
is being made towards the statutory goal of preventing any future and 
remedying any existing anthropogenic visibility impairment in Class I 
areas. 40 CFR 51.308(f)(2) and (3).
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    \14\ The EPA explained in the 2017 RHR Revisions that we were 
adopting new regulatory language in 40 CFR 51.308(f) that, unlike 
the structure in 51.308(d), ``tracked the actual planning 
sequence.'' (82 FR 3091, January 10, 2017).
    \15\ The five ``additional factors'' for consideration in Sec.  
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 EPA's regulations. See CAA

[[Page 63262]]

section 169A(b)(2); CAA section 110(a). Upon EPA approval, a SIP is 
enforceable by the Agency and the public under the CAA. If 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 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 35720-22, 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, 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 section apply only to states having Class I areas 
within their borders; the required calculations must be made for each 
such Class I area. EPA's 2018 Visibility Tracking Guidance \16\ 
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 3103-05.
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    \16\ The 2018 Visibility Tracking Guidance references and relies 
on parts of the 2003 Tracking Guidance: ``Guidance for Tracking 
Progress Under the Regional Haze Rule,'' which can be found at 
https://www.epa.gov/sites/default/files/2021-03/documents/tracking.pdf.
---------------------------------------------------------------------------

    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).\17\ 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), (iii). States must also 
calculate natural visibility conditions for the clearest and most 
impaired days,\18\ 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 to reach 
natural visibility conditions.
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    \17\ This document also refers to the 20% clearest and 20% most 
anthropogenically impaired days as the ``clearest'' and ``most 
impaired'' or ``most anthropogenically impaired'' days, 
respectively.
    \18\ The RHR at 40 CFR 51.308(f)(1)(ii) contains an error 
related to the requirement for calculating two sets of natural 
conditions values. The rule says ``most impaired days or the 
clearest days'' where it should say ``most impaired days and 
clearest days.'' This is an error that was intended to be corrected 
in the 2017 RHR Revisions but did not get corrected in the final 
rule language. This is supported by the preamble text at 82 FR 3098: 
``In the final version of 40 CFR 51.308(f)(1)(ii), an occurrence of 
``or'' has been corrected to ``and'' to indicate that natural 
visibility conditions for both the most impaired days and the 
clearest days must be based on available monitoring information.''
---------------------------------------------------------------------------

    Using the data for the set of most impaired days only, states must 
plot a line between visibility conditions in the baseline period and 
natural visibility conditions for each Class I area to determine the 
URP--the amount of visibility improvement, measured in deciviews, that 
would need to be achieved during each implementation period to achieve 
natural visibility conditions by the end of 2064. The URP is used in 
later steps of the reasonable progress analysis for informational 
purposes and to provide a non-enforceable benchmark against which to 
assess a Class I area's rate of visibility improvement.\19\ 
Additionally, in the 2017 RHR Revisions, the EPA provided states the 
option of proposing to adjust the endpoint of the URP to account for 
impacts of anthropogenic sources outside the United States and/or 
impacts of certain types of wildland prescribed fires. These 
adjustments, which must be approved by the EPA, are intended to avoid 
any perception that states should compensate for impacts from 
international anthropogenic sources and to give states the flexibility 
to determine that limiting the use of wildland-prescribed fire is not 
necessary for reasonable progress. 82 FR 3107 footnote 116.
---------------------------------------------------------------------------

    \19\ Being on or below the URP is not a ``safe harbor''; i.e., 
achieving the URP does not mean that a Class I area is making 
``reasonable progress'' and does not relieve a state from using the 
four statutory factors to determine what level of control is needed 
to achieve such progress. See, e.g., 82 FR 3093.
---------------------------------------------------------------------------

    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

[[Page 63263]]

measures that are necessary to make reasonable progress, as determined 
pursuant to (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 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 EPA 
previously explained, consistent with the first implementation period, 
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 Regional Haze Rule, 
which sets up an iterative planning process and anticipates that a 
state may not need to analyze control measures for all its sources in a 
given SIP revision.'' 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.
    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.\20\
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    \20\ Similarly, in responding to comments on the 2017 RHR 
Revisions the EPA explained that ``[a] state should not fail to 
address its many relatively low-impact sources merely because it 
only has such sources and another state has even more low-impact 
sources and/or some high impact sources.'' Responses to Comments on 
Protection of Visibility: Amendments to Requirements for State 
Plans; Proposed Rule (81 FR 26942, May 4, 2016) at 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.\21\ This is accomplished by considering the four factors--``the 
costs of compliance, the time necessary for compliance, and the energy 
and non-air quality environmental impacts of compliance, and the 
remaining useful life of any existing source subject to such 
requirements.'' 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 to satisfy 
the CAA's reasonable progress mandate.'' 82 FR 3091. Thus, for each 
source it has selected for four-factor analysis,\22\ a state 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.
---------------------------------------------------------------------------

    \21\ 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.
    \22\ ``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 
3088. However, not all approaches to grouping sources for four-
factor analysis are necessarily reasonable; the reasonableness of 
grouping sources in any particular instance will depend on the 
circumstances and the manner in which grouping is conducted. If it 
is feasible to establish and enforce different requirements for 
sources or subgroups of sources, and if relevant factors can be 
quantified for those sources or subgroups, then states should make a 
separate reasonable progress determination for each source or 
subgroup. 2021 Clarifications Memo at 7-8.
---------------------------------------------------------------------------

    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 emissions reduction measures for sources), 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

[[Page 63264]]

such improvements are reasonable given that they typically involve only 
additional operation and maintenance costs. Additionally, the 2021 
Clarifications Memo provides that states that have assumed a higher 
emissions rate than a source has achieved or could potentially achieve 
using its existing measures should also consider lower emissions rates 
as potential control options. That is, a state should consider a 
source's recent actual and projected 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.\23\ 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.''
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    \23\ See, e.g., Responses to Comments on Protection of 
Visibility: Amendments to Requirements for State Plans; Proposed 
Rule (81 FR 26942, May 4, 2016) (December 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.\24\ 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 emissions rate, it may not 
be necessary to have those measures in the long-term strategy to 
prevent future emissions increases and future visibility impairment. 
The EPA's 2021 Clarifications Memo provides further explanation and 
guidance on how states may demonstrate that a source's existing 
measures are not necessary to make reasonable progress. 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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    \24\ 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 3108-09 (requirement to consider smoke 
management practices and smoke management programs under 40 CFR 
51.308(f)(2)(iv) does not require states to adopt such practices or 
programs into their SIPs, although they may elect to do so).
---------------------------------------------------------------------------

    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, 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.\25\ 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.
---------------------------------------------------------------------------

    \25\ 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

[[Page 63265]]

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'' \26\ 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.
---------------------------------------------------------------------------

    \26\ The five ``additional factors'' for consideration in Sec.  
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.
---------------------------------------------------------------------------

    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 3091. 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.\27\ 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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    \27\ 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, control 
determinations by other states, and 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. 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-
2004. See 40 CFR 51.308(f)(1)(i), 82 FR 3097-98.
    So that RPGs may also serve as a metric for assessing the amount of 
progress a state is making towards the national visibility goal, the 
RHR requires states with Class I areas to compare the 2028 RPG for the 
most impaired days to the corresponding point on the URP line 
(representing visibility conditions in 2028 if visibility

[[Page 63266]]

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 3093, 3099-
3100; 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 section apply either to states with Class I 
areas within their borders, states with no Class I areas but that are 
reasonably anticipated to cause or contribute to visibility impairment 
in any Class I area, or both. A state with Class I areas within its 
borders must submit with its SIP revision a monitoring strategy for 
measuring, characterizing, and reporting regional haze visibility 
impairment that is representative of all Class I areas within the 
state. SIP revisions for such states must also provide for the 
establishment of any additional monitoring sites or equipment needed to 
assess visibility conditions in Class I areas, as well as reporting of 
all visibility monitoring data to the EPA at least annually. Compliance 
with the monitoring strategy requirement may be met through a state's 
participation in the Interagency Monitoring of Protected Visual 
Environments (IMPROVE) monitoring network, which is used to measure 
visibility impairment caused by air pollution at the 156 Class I areas 
covered by the visibility program. 40 CFR 51.308(f)(6) introductory 
text and (f)(6)(i) and (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), (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.\28\ 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.\29\
---------------------------------------------------------------------------

    \28\ See ``Step 8: Additional requirements for regional haze 
SIPs'' in 2019 Guidance at 55.
    \29\ Id.
---------------------------------------------------------------------------

    Separate from the requirements related to monitoring for regional 
haze purposes under 40 CFR 51.308(f)(6), the RHR also contains a 
requirement at 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.'' \30\ 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.
---------------------------------------------------------------------------

    \30\ The EPA's visibility protection regulations define 
``reasonably attributable visibility impairment'' as ``visibility 
impairment that is caused by the emission of air pollutants from 
one, or a small number of sources.'' 40 CFR 51.301.
---------------------------------------------------------------------------

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

    Section 51.308(f)(5) requires a state's regional haze SIP revision 
to address the requirements of paragraphs 40 CFR 51.308(g)(1) through 
(5) so that the plan revision due in 2021 will serve also as a progress 
report addressing the period since submission of the progress report 
for the first implementation period. The regional haze progress report 
requirement is designed to inform the public and the EPA about a 
state's implementation of its existing long-term strategy and whether 
such implementation is in fact resulting in the expected visibility 
improvement. See 81 FR 26942, 26950 (May 4, 2016), (82 FR 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

[[Page 63267]]

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 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(g)(3)(iii)(B), (f)(5). 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(g)(4), (f)(5). Changes in emissions should be identified by 
the type of source or activity. Section 51.308(g)(5) also addresses 
changes in emissions since the period addressed by the previous 
progress report and requires states' SIP revisions to include an 
assessment of any significant changes in anthropogenic emissions within 
or outside the state. This assessment must explain whether these 
changes in emissions were anticipated and whether they have limited or 
impeded progress in reducing emissions and improving visibility 
relative to what the state projected based on its long-term strategy 
for the first implementation period.

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). 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 Iowa's Regional Haze Submission for the 
Second Implementation Period

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

    IDNR submitted its regional haze SIP for the first implementation 
period to the EPA on March 25, 2008. Iowa relied on the Clean Air 
Interstate Rule (CAIR) to satisfy BART requirements. In July 2008, the 
CAIR rule was vacated by the District of Columbia Circuit Court.\31\ In 
response on August 8, 2011, the EPA replaced CAIR with the Cross-State 
Air Pollution Rule (CSAPR). On June 7, 2012, the EPA promulgated the 
CSAPR better than BART rule, allowing states to rely on CSAPR to 
satisfy BART requirements. In that same action, the EPA finalized the 
limited disapproval of Iowa's regional haze SIP and imposed a Federal 
Implementation Plan (FIP) for Iowa to replace reliance on CAIR for BART 
with reliance on CSAPR to satisfy BART requirements (77 FR 33642, June 
7, 2012). On June 26, 2012, the EPA finalized a limited approval for 
certain elements of Iowa's first implementation period regional haze 
SIP submission (77 FR 38006, June 26, 2012). On May 14, 2019, Iowa 
submitted a SIP revision to change their reliance on CAIR for BART to 
relying on CSAPR for BART. The EPA fully approved Iowa's regional haze 
SIP for the first implementation period on December 3, 2019 (84 FR 
66075, December 3, 2019). The requirements for regional haze SIPs for 
the first implementation period are contained in 40 CFR 51.308(d) and 
(e). Pursuant to 40 CFR 51.308(g), Iowa was also responsible for 
submitting a five-year progress report as a SIP revision for the first 
implementation period, which it did on July 19, 2013. The EPA approved 
the progress report into the Iowa SIP on August 15, 2016 (81 FR 53924, 
August 15, 2016).
---------------------------------------------------------------------------

    \31\ 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).
---------------------------------------------------------------------------

B. Iowa's Second Implementation Period SIP Submission and the EPA's 
Evaluation

    In accordance with CAA section 169A and the RHR at 40 CFR 
51.308(f), (g), and (i), on August 15, 2023, IDNR submitted a revision 
to the Iowa SIP to address its regional haze obligations for the second 
implementation period, which runs through 2028. Iowa made its 2023 
Regional Haze SIP submission available for public comment from February 
13, 2023, through March 16, 2023. The State held a public hearing for 
the plan on March 16, 2023. IDNR received and responded to public 
comments and included the comments and responses to those comments in 
its submission.
    The following sections describe Iowa's SIP submission. This 
document also contains the EPA's evaluation of Iowa's submission 
against the requirements of the CAA and RHR for the second 
implementation period of the regional haze program.

C. Identification of Class I Areas

    Section 169A(b)(2) of the CAA requires each state in which any 
Class I area is located or ``the emissions from which may reasonably be 
anticipated to cause or contribute to any impairment of visibility'' in 
a Class I area to have a plan for making reasonable progress toward the 
national visibility goal. The RHR implements this statutory requirement 
at 40 CFR 51.308(f) introductory text, which provides that each state's 
plan ``must address regional haze in each mandatory Class I Federal 
area located within the State and in each mandatory Class I Federal 
area located outside the State that may be affected by emissions from 
within the State,'' and (f)(2), which requires each state's plan to 
include a long-term strategy that addresses regional haze in such Class 
I areas.
    The EPA explained in the 1999 RHR preamble that the CAA section 
169A(b)(2) requirement that states submit SIPs to address visibility

[[Page 63268]]

impairment establishes ``an `extremely low triggering threshold' in 
determining which States should submit SIPs for regional haze.'' 64 FR 
35721. In concluding that each of the contiguous 48 states and the 
District of Columbia meet this threshold,\32\ 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 3094.
---------------------------------------------------------------------------

    \32\ 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 35721. Hawaii, Alaska, and the U.S. Virgin 
Islands must also submit regional haze SIPs because they contain 
Class I areas.
---------------------------------------------------------------------------

    Iowa contains no Class I Areas. In Iowa's Regional Haze plan for 
the first planning period, Iowa analyzed ten Class I areas: Boundary 
Waters Canoe Area, Minnesota; Voyageurs National Park, Minnesota; Seney 
Wilderness Area, Michigan; Isle Royale National Park, Michigan; 
Hercules Glades Wilderness Area, Missouri; Mingo Wilderness Area, 
Missouri; Caney Creek Wilderness, Arkansas; Upper Buffalo Wilderness, 
Arkansas; Badlands National Park, South Dakota; and Wind Cave National 
Park, South Dakota.\33\ In Iowa's Regional Haze plan for the second 
planning period, Iowa analyzed potential contributions to visibility 
impairment in twelve Class I areas: the ten Class I areas analyzed in 
the first planning period, plus Mammoth Cave, Kentucky and Wichita 
Mountains Wilderness Area, Oklahoma. To make this determination, Iowa 
used photochemical source apportionment modeling completed by LADCO and 
contained in appendix A-1 and appendix A-2 of the state submission. The 
2021 LADCO analysis used Particulate Matter Source Apportionment 
Technology (PSAT) results from the Comprehensive Air Quality Model with 
extensions (CAMx) to track state contributions to downwind Class I 
areas for the 2018 to 2028 Regional Haze planning period. Based on 
LADCO's analysis using 2028 projected emissions, the State compiled 
Iowa's modeled anthropogenic sulfate, nitrate, and primary particulate 
(elemental carbon, primary organic aerosols, fine soil and course mass) 
source contributions to visibility impairment in inverse megameters 
(Mm-1) on the 20% most impaired days at each of the twelve 
Class I areas in table 2-2 of the State submission. Iowa also included 
the results as a percentage of the total modeled impact (excluding 
Rayleigh and sea salt contributions) in table 2-3 of the State's plan.
---------------------------------------------------------------------------

    \33\ Iowa State Implementation Plan for Regional Haze--Final 
March 2008.
---------------------------------------------------------------------------

    In Iowa's regional haze plan for the first planning period, Iowa 
determined State emissions could contribute to visibility impairment in 
four Class I areas: Isle Royale, Michigan; Seney, Michigan; Boundary 
Waters Canoe Area, Minnesota; and Voyageurs, Minnesota. Based on the 
LADCO CAMx PSAT results provided in table 2-3 of the State submission, 
Iowa's projected 2028 anthropogenic contributions to visibility 
impairment for each of those Class I areas ranges from 3 percent 
(Voyageurs, Minnesota) to 3.9 percent (Isle Royale, Michigan). For 
consistency with the SIP-approved regional haze plan from the first 
period, Iowa determined it was reasonable to retain the same linkages 
in the second planning period and to include any additional Class I 
areas where State contributions were 3 percent or greater. Based on 
that approach, the State added one additional linkage for the second 
planning period to Hercules-Glades Wilderness Area, Missouri because 
Iowa's contribution was 3.9 percent. The State contributions did not 
exceed the 3 percent threshold for any of the other Class I areas 
modeled by LADCO. Table 1 summarizes Iowa's modeled contributions to 
the twelve Class I areas based on LADCO's 2028 CAMx PSAT analysis and 
identifies the five Class I areas linked to Iowa's emissions in the 
State's regional haze plan for the second implementation period using 
the State's chosen 3% contribution threshold.

  Table 1--Summary of Modeled Contributions on 20% Most Impaired Days From LADCO's 2028 CAMx PSAT Analysis and Determination of Class I Areas Linked to
                                                         Iowa's Emissions in 2nd Planning Period
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                     Total modeled    Iowa's modeled anthropogenic
                                                                                       extinction            contributions *            Class I areas
                                                                                       excluding    --------------------------------   linked to Iowa's
                     State                                  Class I area             Rayleigh & Sea                                    emissions in 2nd
                                                                                     Salt (Mm-\1\)       Mm-\1\             %          planning period
 
--------------------------------------------------------------------------------------------------------------------------------------------------------
Arkansas.......................................  Caney Creek......................            42.95            0.59             1.4  ...................
Arkansas.......................................  Upper Buffalo....................            42.96            0.90             2.1  ...................
Kentucky.......................................  Mammoth Cave.....................            62.89            1.81             2.9  ...................
Michigan.......................................  Isle Royale......................            36.36            1.42             3.9                   X
Michigan.......................................  Seney............................            45.12            1.49             3.3                   X
Minnesota......................................  Boundary Waters..................            29.31            0.94             3.2                   X
Minnesota......................................  Voyageurs........................            28.74            0.87             3.0                   X
Missouri.......................................  Hercules-Glades..................            48.13            1.86             3.9                   X
Missouri.......................................  Mingo............................            57.35            1.34             2.3  ...................
Oklahoma.......................................  Wichita Mountains................            44.82            0.56             1.2  ...................
South Dakota...................................  Badlands.........................            22.47            0.25             1.1  ...................
South Dakota...................................  Wind Cave........................            18.10            0.18             1.0  ...................
--------------------------------------------------------------------------------------------------------------------------------------------------------
* The anthropogenic contributions account for sulfates, nitrates, and primary particulates.


[[Page 63269]]

    We acknowledge that the 3 percent or greater State contribution 
threshold used to determine whether Iowa emissions contribute to 
visibility impairment at a particular Class I area may be higher than 
what EPA believes is an ``extremely low triggering threshold'' intended 
by the statute and regulations. However, we note that although Iowa did 
not establish formal linkages to Class I areas other than Isle Royale, 
Seney, Boundary Waters, Voyageurs, and Hercules-Glades, the State 
evaluated source impacts on all twelve of the Class I areas listed in 
table 1 in the source-selection process as discussed in section V.E.a. 
of this document. Furthermore, Iowa consulted with other states and 
FLMs regarding their long-term strategy for regional haze through 
regional calls organized by CenSARA and LADCO. At the time of 
submission, no other states requested additional emission reduction 
measures or evaluation of other Class I areas. As discussed in further 
detail below, the EPA is proposing to find that Iowa has submitted a 
regional haze plan that meets the requirements of 40 CFR 51.308(f)(2) 
related to the development of a long-term strategy. Thus, although the 
3 percent contribution threshold used in this analysis may be higher 
than intended by the statute and regulation, we propose to find that 
Iowa appropriately evaluated its visibility impact at twelve out of 
State Class I areas and has satisfied the applicable requirements for 
making reasonable progress towards natural visibility conditions in 
Class I areas that may be affected be emissions from the State.

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).
    These requirements only apply to states with Class I areas. These 
statutory requirements do not apply because Iowa does not have any 
Class I areas.

E. Long-Term Strategy for Regional Haze

a. Iowa's Source Selection and 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 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). 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 taken into 
consideration in selecting the emission reduction measures for 
inclusion in the long-term strategy. 40 CFR 51.308(f)(2)(iii).
    The following paragraphs summarize how Iowa's SIP submission 
addressed the requirements of Sec.  51.308(f)(2)(i). The EPA's 
evaluation of Iowa's SIP revision with regard to the same is contained 
in the following section V.E.b. and in the technical support document 
(TSD) in the docket for this action.
    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)(2)(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.
    Iowa is a member of the CenSARA RPO. CenSARA and its contractor 
provided member States with an area of influence (AOI) study for Class 
I areas throughout and near the CenSARA region. The AOI study provided 
by CenSARA is a technical analysis product to help assess source and 
State-level contributions to visibility impairment and the need for 
interstate consultation. Iowa relied upon the AOI study to conduct an 
analysis of emission sources and select sources for a four-factor 
analysis.
    The cumulative sulfate and nitrate extinction weighted residence 
time (EWRT) multiplied by Q/d (emissions divided by distance) analysis 
was performed by a CenSARA contractor using 2016 actual emissions data 
and 2028 emissions projections. It 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

[[Page 63270]]

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 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. The AOI study and analysis tool 
are included in appendix B and appendix C-1 of the State submission.
    For its own analysis, IDNR decided to sum the sulfate and nitrate 
contributions for each facility based on 2016 emissions. Rather than 
evaluating all sources with an individual impact greater than a given 
percentage, such as 1 percent, Iowa used the per-facility percentage 
contributions (ranked from largest to smallest) for Iowa facilities, as 
well as sources in other states, to compute a cumulative (rolling 
total) percentage of the total visibility impairment for a Class I 
area. The cumulative rankings for each of the 12 Class I areas 
evaluated by IDNR is provided in appendix C-2 of the State submission.
    Based on that analysis, Iowa decided to select sources for a four-
factor analysis based upon a cumulative percentage threshold of 50 
percent, or all sources contributing to a majority of the combined 
(sulfate plus nitrate) impacts in any Class I area. This approach of 
focusing on cumulative sulfate and nitrate impacts among all sources at 
each Class I area resulted in the selection of sources with fairly low 
individual contributions to those Class I areas. This analysis resulted 
in Iowa selecting two sources for four-factor analysis: Louisa 
Generating Station (LGS) and Walter Scott Jr. Energy Center (WSEC). The 
LGS and WSEC each contributed to a majority of the combined visibility 
impacts at Isle Royale, even though their individual sulfate plus 
nitrate impacts were 0.86% and 0.55%, respectively. No other Iowa 
source contributed above the 50 percent threshold chosen by IDNR in any 
other Class I area.
    To support the development of emissions reduction measures, Iowa 
gathered information on each of the four statutory factors for the two 
sources identified. Both sources are coal-fired EGUs operated by 
MidAmerican Energy Company. Source-specific data included explanations 
of source characteristics, existing controls for SO2 and 
NOX, unit-level emissions, projected boiler operations, and 
the identification of technically feasible control options for 
SO2 and NOX. In section 5 of Iowa's submittal, 
the State explains the four-factor analyses performed by the 
MidAmerican Energy Company for the two facilities. The analyses 
evaluated the costs of control options, potential time frames for 
compliance with control options, potential energy, and non-air quality 
environmental impacts of certain control options, and how the remaining 
useful lives of sources might be considered in a control analysis. The 
state also considered the visibility impacts of control options as an 
additional factor. Iowa's emission reduction measures were based on 
these analyses and looked to either optimize the use of existing 
controls or require the addition of new controls.
    LGS has one boiler that is currently equipped with dry lime flue 
gas desulfurization (FGD) system to reduce SO2 emissions and 
low NOX burners (LNB) with overfire air (OFA) to reduce 
NOX emissions. WSEC has two boilers, identified as Unit 3 
(WSEC-3) and Unit 4 (WSEC-4). Both units are equipped with dry lime FGD 
to reduce SO2 emissions and LNB with OFA to reduce 
NOX. Unit 4 additionally includes a selective catalytic 
reduction (SCR) system to further control NOX emissions. 
Based on the analysis of technically feasible control options, Iowa 
determined that WSEC-4 is currently equipped with all feasible control 
options.
    Four potential control options were identified for LGS and WSEC-3. 
The two evaluated SO2 controls were operational improvements 
to the existing dry FGD systems or replacement with new wet FGDs. The 
two evaluated NOX controls included the addition of either 
selective noncatalytic reduction (SNCR) or SCR systems.
    The source evaluated the cost of each identified control option for 
LGC and WSEC. The results for the SO2 control options are 
shown in table 2 and the results of the NOX control options 
are shown in table 3. The full cost control analysis was provided in 
appendix D-1 of the State submission and is included in the docket for 
this action.

                                 Table 2--Cost of Evaluated SO2 Control Options
----------------------------------------------------------------------------------------------------------------
                                                                          Total        Emission
                Facility                      Control technology       annualized      reduction      Effective
                                                                        cost ($)      (tons/year)   cost ($/ton)
----------------------------------------------------------------------------------------------------------------
LGS (Unit 101)..........................  Improve Existing Dry FGD..    $1,102,000           3,903          $282
                                          Wet FGD...................    42,122,000           4,722         8,920
WSEC-3..................................  Improve Existing Dry FGD..     1,248,000           5,785           216
                                          Wet FGD...................    41,163,000           6,687         6,160
----------------------------------------------------------------------------------------------------------------


                                 Table 3--Cost of Evaluated NOX Control Options
----------------------------------------------------------------------------------------------------------------
                                                                          Total        Emission
                Facility                      Control technology       annualized      reduction      Effective
                                                                        cost ($)      (tons/year)   cost ($/ton)
----------------------------------------------------------------------------------------------------------------
LGS (Unit 101)..........................  SNCR......................    $3,621,000             566        $6,398
                                          SCR.......................    24,271,942           2,739         8,862
WSEC-3..................................  SNCR......................     4,240,300             755         5,616
                                          SCR.......................    24,771,688           3,849         6,436
----------------------------------------------------------------------------------------------------------------


[[Page 63271]]

    MidAmerican evaluated the time necessary for compliance for each 
potential control option for the two sources. MidAmerican estimated 
that improvements to the existing dry FGD systems at both LGC and WSEC-
3 could be implemented within approximately six months. The company 
estimated that the time needed to install and implement new wet FGD 
systems would be approximately five years. The company estimated SNCR 
could be implemented within three years and SCR could be implemented 
within five years. Iowa determined these timeframes were appropriate 
for considering the time necessary for compliance, but this factor was 
not used to eliminate any potential control options.
    In the State submission, Iowa characterized the information 
provided by MidAmerican on the statutory factors of energy and non-air 
quality environmental impacts and the remaining useful life of the 
sources consistent with 2019 Guidance. MidAmerican evaluated energy and 
non-air quality environmental impacts for each technically feasible 
control option but this factor was not used to eliminate any potential 
control options. The remaining useful life of the two sources was also 
evaluated but was not a determining factor in selecting control 
measures because operation of these units is not limited. In completing 
the control cost analysis, the company considered the useful life of 
the control systems.
    Iowa also evaluated the visibility impacts of control measures as a 
fifth factor and presented this analysis in section 5.8 of the State's 
submission. As explained in section IV.C. of this proposed rule, states 
have flexibility under the CAA and RHR to reasonably consider 
visibility benefits as an optional additional factor alongside the four 
statutory factors. The 2019 Guidance and the 2021 Clarification Memo 
provide recommendations and guidance on how states can consider modeled 
visibility impacts or benefits in the context of a four-factor 
analysis. For its analysis, Iowa calculated a ratio of sulfate impacts 
relative to nitrate impacts from LGS and WSEC on the 20% most impaired 
days at the five linked Class I areas. Iowa first quantified the 
State's predicted anthropogenic sulfate and nitrate contributions to 
the 20% most impaired days at each of the Class I areas based on 
LADCO's 2028 CAMx PSAT modeling results. The results are presented as 
extinction values in Mm-1 and percent of total modeled visibility 
impairment in tables 5-7 and 5-8 of the State's submission. Iowa then 
chose the maximum predicted sulfate and nitrate contributions 
attributed to the State's anthropogenic emissions among the five linked 
Class I areas (Isle Royale, Seney, Boundary Waters, Voyageurs, and 
Hercules-Glades). The maximum sulfate impact is 1.000 Mm-1 at Hercules-
Glades, and the maximum nitrate impact is 0.798 Mm-1 at Seney. The 
maximum sulfate and nitrate extinction values were then apportioned to 
LGS and WSEC based on the 2028 projected anthropogenic emissions 
inventory for Iowa, which is summarized in table 5-9 and Figure 5-4 of 
the State's submission. EGUs are projected to emit 78.8% and 22.2% of 
Iowa's 2028 SO2 and NOX emissions, 
respectively.\34\ To calculate factors for apportioning sulfate and 
nitrate contributions to LGS and WSEC, Iowa assumed that LGS and WSEC 
emit the entirety of the State's projected 2028 EGU SO2 and 
NOX emissions totals. For each pollutant, the percentage of 
statewide EGU emissions was multiplied by the ratio of each facility's 
emissions to the sum of LGS and WSEC emissions.\35\ The resulting 
factors were then multiplied by the statewide maximum sulfate and 
nitrate impact values. LGS's estimated sulfate contribution is 0.285 
Mm-1 and its nitrate contribution is 0.064 Mm-1. The corresponding 
sulfate and nitrate impacts for WSEC are 0.503 Mm-1 and 0.133 Mm-1, 
respectively. For both LGS and WSEC, Iowa's analysis indicates that 
sulfate impacts are estimated to be 4.4 times the nitrate impacts. 
Table 4 summarizes Iowa's calculations and the resulting estimated 
sulfate and nitrate impacts from LGS and WSEC.
---------------------------------------------------------------------------

    \34\ Based on LADCO's 2028 emissions projections as summarized 
in table 5-9 of Iowa's regional haze plan submission, Iowa EGUs are 
projected to emit 28,002 tons/year of the total statewide 
SO2 emissions of 35,538 tons/year. For NOX, 
Iowa EGUs are projected to emit 21,442 tons/year of the state's 
total 96,398 tons/year.
    \35\ For example, the SO2 apportionment for LGS is 
calculated as follows: 78.8% * (5,605/(5,605 + 9,897)) = 28.5%. The 
NOX apportionment for LGS is: 22.2% * (3,403/(3,403 + 
6,025)) = 8.0%.

       Table 4--Estimated Sulfate and Nitrate Impacts Attributed to LGS and WSEC on the 20% Most Impaired Days at Iowa's Five Linked Class I Areas
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               2028 Projected emissions    Apportionment factor                                 Ratio
                                                              ----------------------------------------------------   Sulfate      Nitrate     (sulfate/
                           Facility                             SO2 (tpy)    NOX (tpy)                             impact (Mm-  impact (Mm-    nitrate
                                                                                           SO2 (%)      NOX (%)         1)           1)        impact)
--------------------------------------------------------------------------------------------------------------------------------------------------------
LGS..........................................................        5,605        3,403         28.5          8.0        0.285        0.064          4.4
WSEC.........................................................        9,897        6,025         50.3         14.2        0.503        0.113          4.4
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Based upon the four-factor analysis for LGS and WSEC, Iowa 
determined that implementing operational improvements to the existing 
dry FGD systems at LGS and WSEC-3 were necessary to make reasonable 
progress. The cost effectiveness of this control option at LGS is less 
than $300 per ton and results in an estimated reduction of actual 
SO2 emissions by 3,903 tons per year from this source. The 
cost effectiveness of this control option at WSEC is less than $300 per 
ton and results in an estimated reduction of actual SO2 
emissions by 5,785 tons per year from this source. The state determined 
the new wet FGD systems were not considered reasonable due to the cost 
and estimated incremental decrease in SO2 emissions being 
relatively small compared to improvements to the existing dry FGD 
systems (less than 14 percent versus baseline emissions at LGS and less 
than 11 percent versus baseline emissions at WSEC-3).\36\ Iowa decided 
not to require the addition of SNCR or SCR control systems to further 
control NOX emissions at either facility at this time due to 
the estimated cost effectiveness of both options exceeding $5,000 per 
ton and the lower visibility benefits than compared to SO2 
controls.
---------------------------------------------------------------------------

    \36\ See table 5.5 of the State submission, included in the 
docket for this action.
---------------------------------------------------------------------------

    Based on the conclusions from the four-factor analysis, Iowa 
modified the air construction permits for the main

[[Page 63272]]

boiler at LGS and WSEC-3 to implement operational improvements to the 
existing dry FGD systems. The permits include new SO2 
emissions limits and compliance schedules. The new SO2 
emission limit for the main boiler at LGS is 800 lb/hr based on a 30-
day rolling average. The new SO2 emission limit for WSEC-3 
is 770 lb/hr based on a 30-day rolling average. Iowa issued both 
permits on July 20, 2023, with compliance dates of December 31, 2023. 
Iowa determined that WSEC-4 is currently equipped with all feasible 
control options. The current permit restricts WSEC-4 to an enforceable 
best available control technology (BACT) SO2 emission limit 
of 0.1 lb/MMBtu and a NOX emission limit of 0.07 lb/MMBtu. 
To establish permanent emission limits for its long-term strategy for 
regional haze, Iowa submitted the air construction permits for LGS, 
WSEC-3, and WSEC-4 for incorporation into the SIP in 40 CFR 52.820(d), 
EPA approved state source-specific requirements. The State's SIP 
submission requested that the EPA not act on Condition 11 of the 
permits for LGS and WSEC-3 nor Condition 6 of the permit for WSEC-4, 
and accordingly those conditions are not included in this action. The 
full permits are included in appendix E of the State submission in the 
docket for this action.
b. The EPA's Evaluation of Iowa's Emissions Reduction Measures and 
Compliance With Sec.  51.308(f)(2)(i)
    The EPA is proposing to find that Iowa has satisfied the 
requirements of Sec.  51.308(f)(2)(i) related to evaluating sources and 
determining the emission reduction measures that are necessary to make 
reasonable progress by considering the four statutory factors. We are 
proposing to find that Iowa reasonably evaluated the two pollutants--
SO2 and NOX--that currently drive visibility 
impairment within the linked Class I areas and that it adequately 
explained and supported its decision to focus on these two pollutants 
through its technical analyses included in the state submission.\37\
---------------------------------------------------------------------------

    \37\ See section 3.3 of the State submission, included in the 
docket for this action.
---------------------------------------------------------------------------

    Section 51.308(f)(2)(i) requires states to evaluate and determine 
the emission reduction measures that are necessary to make reasonable 
progress by applying the four statutory factors to sources in a control 
analysis. 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 explained above, Iowa relied on the cumulative sulfate and 
nitrate emissions weighted residence time (EWRT) multiplied by Q/d 
(emissions divided by distance) analysis performed by a CenSARA 
contractor to compute a cumulative percentage of the total visibility 
impairment from major sources for each Class I area. Iowa used the per-
facility percentage contributions (ranked from largest to smallest) to 
compute a cumulative (rolling total) percentage of the total visibility 
impairment to each Class I area. Iowa selected sources for four-factor 
analysis based upon a cumulative impact threshold of 50 percent in any 
Class I area. Based on this analysis, Iowa selected two sources: Louisa 
Generating Station and Walter Scott Jr. Generating Station.
    Pursuant to the RHR, states must consider selecting sources 
identified by other states or by FLMs. A state receiving a request to 
select a particular source(s) should either perform a four-factor 
analysis on the source(s) or provide a well-reasoned explanation as to 
why it is choosing not to do so. See 2021 Clarifications Memo at 4. No 
other states identified additional sources for evaluation. During 
initial consultations with FLMs, Iowa received recommendations from 
FLMs to evaluate several sources. The U.S. Forest Service identified 
three sources based on its review of emission rate data (lb/MMBtu) and 
results from a LADCO Q/d analysis: University of Northern Iowa, 
Burlington Generating Station, and Muscatine Power and Water, Unit 8. 
The National Park Service identified eleven Iowa sources using a Q/
d(SO2 + NOX) threshold of 1.2 based on 2017 
National Emissions Inventory (NEI) emissions data for the non-EGUs and 
2019 Clean Air Markets Division (CAMD) data for EGUs: Walter Scott Jr. 
Energy Center (EGU), Louisa Generating Station (EGU), George Neal North 
(EGU), George Neal South (EGU), Burlington Generating Station (EGU), 
Muscatine Power and Water (EGU), Ottumwa Generating Station (EGU), ADM 
Corn Processing--Cedar Rapids (non-EGU), Continental Cement Company--
Davenport (non-EGU), Natural Gas Pipeline Co. Of America--Station 107 
(non-EGU), and Northern Natural Gas Co.--Ogden (non-EGU). However, Iowa 
chose to rely on a different source selection methodology based on 
CenSARA's AOI analysis, as explained above and in the State submission. 
While Iowa did not select additional sources identified by FLMs for 
four-factor analysis, it provided supplemental information supporting 
its decision to use CenSARA's AOI analysis because it resulted in more 
technical data.
    During the formal FLM consultation and public comment period, Iowa 
received several comments to broaden its source selection criteria by 
using a higher percent contribution threshold and expand its source 
selection to include two additional sources in Iowa: George Neal North 
and George Neal South. As explained in the 2021 Clarifications Memo, 
states have the discretion to choose any source selection threshold or 
methodology that is reasonable, as long as whatever choices states make 
are reasonably explained and produce a reasonable outcome. 2021 Memo at 
3. Iowa described its source selection criteria in the state submission 
and selected all sources that met the source selection threshold. In 
this case, the 50 percent cumulative impact threshold identified two 
sources in Iowa. We note that Iowa selected its two largest EGUs for 
four-factor analysis and that the evaluation of these sources had the 
potential to meaningfully reduce their contributions to visibility 
impairment. Furthermore, the 2019 Guidance explains that the Regional 
Haze Rule ``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. Thus, although the source 
selection threshold resulted in two sources being evaluated, Iowa 
reasonably chose factors to consider when selecting sources and applied 
these factors in a reasonable way. Therefore, we propose to find Iowa's 
source selection methodology and the sources selected for further 
analysis to be reasonable for the second planning period.
    As detailed above, Iowa included four-factor analyses performed by 
MidAmerican Energy Company for each of the two sources selected for 
further analysis. The state chose to evaluate visibility benefits of 
control measures along with the four statutory factors and described 
how each of the factors were considered in the SIP submission. In 
considering whether compliance costs for sources were reasonable, Iowa 
evaluated the cost estimates for each technically feasible control 
option for both SO2 and NOX completed by 
MidAmerican.
    Based on the EPA's review, we find that Iowa's control cost 
analysis was both reasonable and consistent with the EPA Air Pollution 
Control Cost

[[Page 63273]]

Manual.\38\ The State submission included details on the consideration 
of 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. EPA finds the consideration of these 
statutory factors was reasonable and consistent with the 2019 Guidance 
and 2021 Clarifications Memo. The EPA further reviews the control cost 
analyses in the TSD contained in the docket for this rulemaking.
---------------------------------------------------------------------------

    \38\ EPA Air Pollution Control Cost Manual, https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution.
---------------------------------------------------------------------------

    Iowa also included a visibility benefits analysis that estimated 
sulfate impacts relative to nitrate impacts from LGS and WSEC on the 
20% most impaired days at the five linked Class I areas, as described 
in section V.E.a. of this document. Based on that analysis, the State 
estimated that sulfate impacts to visibility in the linked Class I 
areas are 4.4 times greater than nitrate impacts for both LGS and WSEC. 
While visibility is not an explicitly listed factor to consider when 
determining whether additional controls are reasonable, the purpose of 
the four-factor analysis is to determine what degree of progress toward 
natural visibility conditions is reasonable. Therefore, the EPA has 
interpreted the CAA and the RHR as allowing states to consider 
visibility alongside the four statutory factors when comparing multiple 
emission reduction control options that may be necessary to make 
reasonable progress. See 2021 Clarifications Memo at 12. We find that 
Iowa's consideration of visibility improvements was reasonable and 
consistent with the requirements of the CAA.
    The State determined that operational improvements to the existing 
FGD systems at both LGS and WSEC-3 were the most cost-effective control 
option and showed reducing SO2 emissions increased 
visibility benefits in several Class I areas. Iowa stated that these 
emission reduction measures will reduce actual SO2 emissions 
by an estimated 9,688 tons per year. The State determined that WSEC-4 
is currently equipped with all feasible control options and that the 
existing measures are necessary to reasonable progress. Iowa submitted 
the air construction permits for LGS, WSEC-3, and WSEC-4 for inclusion 
in its long-term strategy. The permits are included in appendix E of 
the State submission in the docket for this action. Section 
51.308(f)(2) of the RHR requires that emission reduction 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 
permits for LGS and WSEC-3 include limits in lb/hour, with compliance 
determined on thirty-day rolling averages through the use of Continuous 
Emission Monitors (CEMs) to the EPA standards, necessary recordkeeping 
and reporting requirements, and cover all times of operation. The new 
limits are: 800 lb/hr for MidAmerican Energy Co.--Louisa Station Unit 
EU1, Louisa Boiler, and 770 lb/hr for MidAmerican Energy Co.--Walter 
Scott Jr. Energy Center, Unit 003, Boiler #3. WSEC-4 was subject to the 
prevention of significant deterioration (PSD) preconstruction 
permitting for SO2 and NOX emissions in 2003. As 
part of the PSD review process, BACT was required for SO2 
and NOX controls. The air construction permit includes a 
BACT SO2 emission limit of 0.1 lb/MMBtu (30-day rolling 
average) and an annual emission restriction of 3,362 tons per rolling 
12-month period. The BACT emission limit for NOX is 0.07 lb/
MMBtu (30-day rolling average) and an annual emission restriction of 
2,353 tons per rolling 12-month period. Compliance with SO2 
and NOX BACT limits is demonstrated using continuous 
emissions monitoring systems (CEMS). The EPA finds the air quality 
construction permits, submitted by Iowa to serve as the enforceable 
mechanism of the long-term strategy, meet the requirements of Sec.  
51.308(f)(2) to include enforceable emissions limitations. We propose 
to find Iowa's four-factor analysis and emission reduction measures to 
be reasonable for the second planning period.
    In sum, the EPA proposes to find that Iowa has satisfied the 
requirements that states determine the emission reduction measures that 
are necessary to make reasonable progress by considering the four 
factors, and that its long-term strategy includes the enforceable 
emission limitations, compliance schedules, and other measures 
necessary to make reasonable progress.
c. 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 coordinate 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.
    Iowa included documentation of its consultation with RPOs and 
individual states in its SIP submission. Specifically, Iowa consulted 
with three states containing the five Class I Areas that Iowa sources 
were expected to impact: Minnesota, Michigan, and Missouri. 
Documentation of consultation with each state is contained in appendix 
H to the State submittal. In addition, Iowa consulted with CenSARA and 
LADCO through its participation in regular planning calls each RPO. 
Iowa did not receive any requests from other states nor did it 
encounter any disagreements. We propose to determine that Iowa has 
satisfied the consultation requirements of Sec.  51.308(f)(2)(ii).
    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. Iowa's SIP submission included in section 7 
emissions information by sector and pollutant from LADCO's 2016 
modeling inventory and from the 2017 NEI. The state analysis included 
data from the 2016 base year and 2028 modeled emissions inventories for 
NOX, SO2, PM2.5, VOCs, and 
NH3. The State's four factor analysis relied on emission 
data from 2009-2021. The State also included emission data from 2009-
2021 for Iowa EGUs. Based on Iowa's consideration of the emission data 
in their SIP submittal, the EPA proposes to find that Iowa has 
satisfied the emissions information requirement in Sec.  
51.308(f)(2)(iii).
    We also propose to find that Iowa reasonably considered the five 
additional factors in Sec.  51.308(f)(2)(iv) in

[[Page 63274]]

developing its long-term strategy. Pursuant to Sec.  
51.308(f)(2)(iv)(A), Iowa noted that existing and ongoing state and 
Federal emission control programs that contribute to emission 
reductions through 2028 would impact emissions of visibility impairing 
pollutants from point and nonpoint sources in the second implementation 
period. Iowa included in its SIP submission details of control measures 
with their effective dates and pollutants addressed.
    Iowa's consideration of measures to mitigate the impacts of 
construction activities as required by Sec.  51.308(f)(2)(iv)(B) is 
included in section 6.2.2. of its SIP submission. Iowa described the 
minor NSR permit requirements for aggregate processing plants, concrete 
batch plants, and asphalt plants and its rules to reduce fugitive dust 
emissions from beyond the property line.\39\ Iowa noted that 
construction activities are unlikely to contribute to visibility 
impairment in Class I areas due to the extensive transport distances in 
combination with relatively low emissions and release heights for 
construction activities.
---------------------------------------------------------------------------

    \39\ 567 IAC 23.3(2)``c.''
---------------------------------------------------------------------------

    Pursuant to Sec.  51.308(f)(2)(iv)(C), source retirements and 
replacement schedules are addressed in section 6.2.3 of Iowa's 
submission. The LADCO modeling used by Iowa considered known source 
retirements and replacements in developing the 2028 emission 
projections. The Iowa EGU source retirements, refuelings, or 
replacements that occurred during or after the 2016 base year are 
identified in table 6-4 of the State submission.\40\
---------------------------------------------------------------------------

    \40\ See table 6-4 of the Iowa Regional Haze SIP--Final August 
2023.
---------------------------------------------------------------------------

    Iowa's consideration of smoke management as required in 40 CFR 
51.308(f)(2)(iv)(D) is included in section 6.2.4. of the SIP 
submission. Iowa explained that source apportionment modeling conducted 
by Central Regional Air Planning Association (CENRAP) for the first 
implementation period demonstrated that fires in Iowa do not 
significantly contribute to visibility in Class I areas. Iowa 
determined that conclusion is still valid since Iowa's total prescribed 
fire and agricultural fire emissions represent less than one percent of 
the U.S. totals in the 2017 NEI, as shown in tables 6-5 and 6-6 of the 
State submission.
    Iowa considered the anticipated net effect of projected changes in 
emissions as required by Sec.  51.308(f)(2)(iv)(E) by discussing, in 
section 8 of its submission, the photochemical modeling for the 2018-
2028 period it conducted by LADCO. Table 8-1 of the State submission 
summarizes the visibility improvements in linked Class I areas. The 
results show improvements of 0.71 to 1.24 deciviews on the 20 percent 
most impaired days and no visibility degredation on the clearest days. 
Iowa explained the results are conservative because they do not 
incorporate the scrubber improvements from its long term strategy 
(LTS), which will further improve visibility.
    Because Iowa has reasonably considered each of the five additional 
factors the EPA proposes to find that Iowa has satisfied the 
requirements of 40 CFR 51.308(f)(2)(iv).

F. Reasonable Progress Goals

    Section 51.308(f)(3) contains the requirements pertaining to RPGs 
for each Class I area. This provision does not apply to Iowa because it 
does not have a Class I Area. Section 51.308(f)(3)(ii)(B) requires that 
if a state contains sources that are reasonably anticipated to 
contribute to visibility impairment in a Class I area in another state, 
and the RPG for the most impaired days in that Class I area is above 
the URP, the upwind state must provide the same demonstration. This 
provision does not apply because the states with Class I areas that are 
affected by Iowa sources did not submit any RPGs that are above the 
URP.

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. 
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. As noted previously, most regulatory 
requirements in Sec.  51.308(f)(6) do not apply to states without Class 
I Areas.
    However, Sec.  51.308(f)(6)(iii) and (v) apply to all states that 
have emissions that contribute to a Class I Area, including Iowa. 
Section 51.308(f)(6)(iii) requires SIPs to provide 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 in other 
states.
    Iowa included details on the monitoring data the State used to 
estimate its visibility contribution to out-of-state Class I Areas, to 
address Sec.  51.308(f)(6)(iii). Iowa relies on the IMPROVE monitoring 
network for monitoring at the Class I areas Iowa selected. We note Iowa 
included details on two IMPROVE protocol monitors previously operated 
by the State in section 9 of the state plan. Iowa's 2023 Ambient Air 
Monitoring Network Plan included the removal of the IMPROVE protocol 
monitors and was separately reviewed and approved by EPA. The removal 
of the IMPROVE protocol monitors does not impact this action because 
IMPROVE protocol monitors are not located at and do not represent 
visibility at mandatory Class I Federal areas. Therefore, neither the 
presence nor lack of IMPROVE protocol monitors has any direct impact on 
``determining the contribution of emissions from within the state to 
out-of-state Class I areas''.
    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.
    To address Sec.  51.308(f)(6)(v), Iowa included emissions 
information by pollutant from LADCO's 2016 modeling inventory and from 
the 2017 NEI.\41\ The State's four factor analysis relied on emission 
data from 2009-2021. The State also included emission data from 2009-
2021 for Iowa EGUs. Iowa also included future projections for 2028. 
Iowa committed to update the inventory periodically and comply with the 
Air Emissions Reporting Requirements. Based on Iowa's consideration of 
the emission data in their SIP submittal, the EPA proposes to find that 
Iowa has satisfied the emissions information requirement in Sec.  
51.308(f)(6)(v).
---------------------------------------------------------------------------

    \41\ See section 7 and 11 of the Iowa Regional Haze SIP--Final 
August 2023, included in the docket for this action.

---------------------------------------------------------------------------

[[Page 63275]]

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. Section 
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.
    Iowa's submission describes the status of measures of the long-term 
strategy from the first implementation period. Iowa relied upon the 
Clean Air Interstate Rule (CAIR), later replaced by the Cross-State Air 
Pollution Rule (CSAPR), to satisfy long-term strategy obligations and 
Best Available Retrofit Technology (BART) requirements for EGUs. Iowa 
met all the identified reasonable measures during the first 
implementation period. Iowa's SIP submission includes EGU emission data 
demonstrating the reductions achieved throughout the State in table 10-
1. The included emission data demonstrates a decrease in SO2 
and NOX emissions since 2008, the year preceding CAIR 
implementation. Between 2008 and 2021, SO2 and 
NOX emissions declined by 81,258 and 30,078 tons, 
respectively.
    The EPA proposes to find that Iowa has met the requirements of 40 
CFR 51.308(g)(1) and (2) because its SIP submission describes the 
measures included in the long-term strategy from the first 
implementation period, as well as the status of their implementation 
and the emission reductions achieved through such implementation. 
Section 51.308(g)(3) does not apply to Iowa because it does not have a 
Class I Area.
    Pursuant to Sec.  51.308(g)(4), in section 10 of their submittal, 
Iowa provided a summary of NEI data for SO2, NOX, 
VOCs, PM10, PM2.5, and NH3 for the 
years 2008 and 2017. The summarized emissions data in tables 10-2 and 
10-3 of the state submission include anthropogenic emissions 
represented by point source EGU, point source non-EGU, nonpoint 
sources, on-road mobile sources and nonroad mobile sources; fire 
emissions including wildfire, prescribed fire and agriculture fire; and 
biogenic emissions from vegetation and soils. Iowa also included CAMD 
data in table 10-1 showing annual total EGU SO2 and 
NOX emissions for the time period from 2002 to 2021.
    The reductions achieved through Iowa emission control measures are 
seen in the emissions inventory. Based on Iowa's SIP submittal, 
NOX emissions have significantly declined in Iowa from 2008 
to 2017 based on decreased emissions in the point EGU, point non-EGU, 
on-road and non-road sectors. NOX emissions from the EGU 
sector decreased by 28,009 tpy, equating to a sector reduction of 55%. 
Total NOX reductions decreased by 103,080 tpy, or 34%.
    Emissions of SO2 have shown a significant decline in 
Iowa from 2008 to 2017, particularly in the point EGU sector. During 
that period, SO2 emissions from EGUs decreased by 86,091 
tpy, equating to a sector reduction of 73%. Overall, SO2 
emissions declined by 125,347 tpy, or 76%.
    Iowa's submission includes a summary of PM10 emissions 
from all NEI data categories point EGU, point non-EGU, nonpoint, on-
road, nonroad, and fire for 2008 and 2017 in Iowa. In Iowa, 
PM10 emissions decreased in all categories except fire 
during that period. The PM10 emissions decreased by more 
than 200,000 tpy, or 37%.
    Iowa's submission shows a summary of PM2.5 emissions 
from all NEI data categories for 2008 and 2017 in Iowa. 
PM2.5 emissions decreased all categories except the fire 
sector. Decreases in PM2.5 emissions are attributed to 
Federal new engine standards for nonroad vehicles and equipment, 
Federal and State regulations for on-road vehicles, and reductions in 
the nonpoint sector. The other large decrease in PM2.5 
emissions is primarily due to the decrease in emissions from fuel 
combustion at EGU and Industrial stationary sources.
    VOC emissions declined in Iowa from 477,959 tpy in 2008 to 141,289 
tpy in 2017. VOC decreases were achieved in all sectors except the fire 
sector.
    Overall, ammonia (NH3) emissions increased in Iowa from 
2008 to 2017, primarily driven by increased emissions from the nonpoint 
source category. Nonpoint increases are due to reporting, grouping and 
methodology changes, as well as estimated emissions increase from 
agricultural sources. Overall, ammonia emissions increased by 11% in 
Iowa from 2008 to 2017.
    The EPA is proposing to find that Iowa has satisfied the 
requirements of Sec.  51.308(g)(4) by providing emissions information 
for NOX, SO2, PM10, PM2.5, 
VOCs, and NH3 broken down by type of source.
    Iowa uses the emissions trend data in the SIP submission \42\ to 
support the assessment that anthropogenic haze-causing pollutant 
emissions in Iowa have decreased during the reporting period and that 
changes in emissions have not limited or impeded progress in reducing 
pollutant emissions and improving visibility. Overall, Iowa's 2017 
emission inventories for NOX, SO2, 
PM10, PM2.5, and VOCs were lower than their 2008 
emission inventories and the forecasted 2018 emissions from Iowa's 
regional haze SIP for the first planning period \43\ for those same 
pollutants emissions. The 2017 emission inventory for NH3 
were higher than the 2008 emission inventory and the forecasted 2018 
emissions. However, the slight increase did not impede progress towards 
improving visibility in Class I Areas. The EPA is proposing to find 
that Iowa has met the requirements of Sec.  51.308(g)(5).
---------------------------------------------------------------------------

    \42\ See section 10.5 ``Emissions Changes Assessment'' of the 
Iowa Region Haze SIP--Final August 2023, included in the docket for 
this action.
    \43\ See table 10-5 of the Iowa Regional Haze SIP--Final August 
2023, included in the docket for this action.
---------------------------------------------------------------------------

I. Requirements for State and Federal Land Manager Coordination

    Section 169A(d) of the CAA requires states to consult with FLMs 
before

[[Page 63276]]

holding the public hearing on a proposed regional haze SIP, and to 
include a summary of the FLMs' conclusions and recommendations in the 
notice to the public. In addition, Sec.  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.
    Iowa conducted informal FLM consultation early in the planning 
process to inform the state's decision-making process. As part of this 
early engagement with the FLMs, the U.S. Forest Service and the 
National Park Service each provided a recommendation to Iowa suggesting 
that it consider specific individual sources in its long-term 
strategies. In March 2020, the Forest Service identified three sources 
based on its review of emission rate data (lb/MMBtu) and results from a 
LADCO Q/d analysis. In June 2020, the National Park Service identified 
eleven Iowa sources using a Q/d(SO2 + NOX) 
threshold of 1.2 based on 2017 NEI emissions data for the non-EGUs and 
2019 CAMD data for EGUs. As part of the consultation, Iowa reviewed its 
source selection methods and results with FLMs on June 3, 2020. On 
January 20, 2022, the state met with FLMs to informally discuss Iowa's 
four-factor analysis.
    On October 11, 2022, Iowa submitted a draft Regional Haze SIP to 
the U.S. Forest Service, the U.S. Fish and Wildlife Service, and the 
National Park Service for a 60-day review and comment period pursuant 
to 40 CFR 51.308(i)(2).\44\ On November 3, 2022, Iowa held a virtual 
consultation meeting with the FLMs. Iowa received comments from the 
Forest Service and the National Park Service on December 8, 2022.\45\ 
Iowa responded to the FLM comments and included the responses in 
section 11.5 of its submission to EPA and their public notice, in 
accordance with the requirements in CAA section 169A(d) and Sec.  
51.308(i)(3). Notices of the proposed SIP, availability and the public 
hearing were published on IDNR's website, published in the Des Moines 
Register on February 13, 2023, and issued on the IDNR air quality 
listserv. A virtual public hearing on the proposed SIP revision was 
held on March 16, 2023. Written comments relevant to the proposal were 
accepted until the close of business March 16, 2023. Iowa's August 2023 
SIP includes a commitment to ongoing consultation with FLMs in 
accordance with Sec.  51.308(i)(4).
---------------------------------------------------------------------------

    \44\ Id.
    \45\ See appendix F of the State submission, included in the 
docket for this action.
---------------------------------------------------------------------------

    For the reasons stated above, the EPA proposes to find that Iowa 
has satisfied the requirements under 40 CFR 51.308(i) to consult with 
the FLMs on its regional haze SIP for the second implementation period.
    Iowa's August 2023 SIP submission includes a commitment to submit 
periodic progress reports in accordance with Sec.  51.308(f) and a 
commitment to evaluate progress towards the reasonable progress goal 
for each mandatory Class I Federal area located within the State and in 
each mandatory Class I Federal area located outside the State that may 
be affected by emissions from within the State in accordance with Sec.  
51.308(g).\46\
---------------------------------------------------------------------------

    \46\ See section 10.5 of the ``Iowa Regional Haze SIP--Final 
August 2023.''
---------------------------------------------------------------------------

VI. What action is the EPA proposing?

    The EPA is proposing to approve the Iowa SIP submission received on 
August 15, 2023, as satisfying the regional haze requirements for the 
second implementation period contained in 40 CFR 51.308(f). We are 
processing this as a proposed action because we are soliciting comments 
on this proposed action. Final rulemaking will occur after 
consideration of any comments.

VII. Incorporation by Reference

    In this document, the EPA is proposing to include regulatory text 
in an EPA final rule that includes incorporation by reference. In 
accordance with requirements of 1 CFR 51.5, the EPA is proposing to 
incorporate by reference ``Iowa Regional Haze Plan for the Second 
Implementation Period'' source specific requirements for MidAmerican 
Energy Company Louisa Station (Permit number 05-A-031-P6) and 
MidAmerican Energy Company Walter Scott Jr. Energy Center (Permit 
numbers 75-A-357-P9 and 03-A-425-P4), submitted on August 15, 2023. The 
EPA has made, and will continue to make, these materials generally 
available through https://www.regulations.gov and at the EPA Region 7 
Office (please contact the person identified in the FOR FURTHER 
INFORMATION CONTACT section of this preamble for more information).

VIII. 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.'' \47\
---------------------------------------------------------------------------

    \47\ See https://www.epa.gov/environmentaljustice/learn-about-environmentaljustice.
---------------------------------------------------------------------------

    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 Executive Order 12898 of achieving environmental justice for people 
of color, low-income populations, and Indigenous peoples. However, 
recognizing the importance of environmental justice 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. 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

[[Page 63277]]

indicators.\48\ The EJScreen tool presents these indicators at a Census 
block group (CBG) level or a larger user specified ``buffer'' area that 
covers multiple CBGs.\49\ An individual CBG is a cluster of contiguous 
blocks within the same census tract and generally contains 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).\50\ 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 Iowa 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.\51\ EJScreen also provides information on 
demographic indicators, including percent low-income, communities of 
color, linguistic isolation, and less than high school education.
---------------------------------------------------------------------------

    \48\ The EJSCREEN tool is available at https://www.epa.gov/ejscreen.
    \49\ See https://www.census.gov/programssurveys/geography/about/glossary.html.
    \50\ 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.
    \51\ 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.
---------------------------------------------------------------------------

    The EPA prepared EJScreen reports covering buffer areas of 
approximately 6-mile radius around the facilities selected by Iowa 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.\52\ 
These indicators are displayed in the table on page 3 of each report. 
The report for Walter Scott Jr. Energy Center showed environmental 
indicators greater than the 80th national percentiles superfund 
proximity and RMP facility proximity. The report for Louis Generating 
Station does not include environmental or socioeconomic indicators 
greater than the 80th national percentiles. The full, detailed EJScreen 
reports for the two facilities selected by Iowa for further analysis 
are provided in the docket for this rulemaking for informational 
purposes only.
---------------------------------------------------------------------------

    \52\ For a place at the 80th percentile nationwide, that means 
20% of the U.S. population has a higher value. 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.
---------------------------------------------------------------------------

    This action is proposing to approve Iowa's second planning period 
regional haze plan as meeting the requirements of the CAA and 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.\53\ 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.\54\ We expect 
that this action and resulting emissions reductions will generally be 
neutral or contribute to reduced environmental and health impacts on 
all populations near both Walter Scott Jr. Energy Center and Louisa 
Generating Station. 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.
---------------------------------------------------------------------------

    \53\ See https://www.epa.gov/so2-pollution/sulfurdioxide-basics#effects.
    \54\ See https://www.epa.gov/pm-pollution/healthand-environmental-effects-particulate-matter-pm.
---------------------------------------------------------------------------

    This action is proposing to approve Iowa's second planning period 
regional haze plan as meeting the requirements of the CAA and the EPA's 
RHR. However, as stated previously, the EPA is not required to, but has 
provided the information associated with the environmental justice 
analysis for informational purposes only. The information provided 
herein does not serve as a basis of the proposed action.

IX. 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, EPA's role is to approve state choices, 
provided that they meet the criteria of the CAA. Accordingly, this 
action merely approves state law as meeting Federal requirements and 
does not impose additional requirements beyond those imposed by state 
law. For that reason, this action:
     Is not a significant regulatory action subject to review 
by the Office of Management and Budget under Executive Orders 12866 (58 
FR 51735, October 4, 1993) and 14094 (88 FR 21879, April 11, 2023);
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not subject to Executive Order 13045 (62 FR 19885, 
April 23, 1997) because it approves a state program;
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001); and
     Is not subject to requirements of section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the CAA.
    Executive Order 12898 (Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations, 59 FR 7629, 
February 16, 1994) directs Federal agencies to identify and address 
``disproportionately high and adverse human health or environmental 
effects'' of their actions on minority populations

[[Page 63278]]

and low-income populations to the greatest extent practicable and 
permitted by law. 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.'' 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 Iowa 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, this action is expected to have a neutral to positive 
impact on the air quality of the affected area. In addition, there is 
no information in the record upon which this decision is based 
inconsistent with the stated goal of E.O. 12898 of achieving 
environmental justice for people of color, low-income populations, and 
Indigenous peoples.
    In addition, this proposed rulemaking action, pertaining to Iowa 
regional haze SIP submission for the second planning period, is not 
approved to apply on any Indian reservation land or in any other area 
where the EPA or an Indian tribe has demonstrated that a tribe has 
jurisdiction. In those areas of Indian country, the rule does not have 
Tribal implications and will not impose substantial direct costs on 
Tribal governments or preempt Tribal law as specified by Executive 
Order 13175 (65 FR 67249, November 9, 2000).

List of Subjects in 40 CFR Part 52

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

    Dated: July 22, 2024.
Meghan A. McCollister,
Regional Administrator, Region 7.

    Title 40, chapter I, of the Code of Federal Regulations is proposed 
to be amended as follows:

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 Q--Iowa

0
2. In Sec.  52.820:
0
a. The table in paragraph (d) is amended by adding the entries 
``(170)'', ``(171)'', and ``(172)'' in numerical order.
0
b. The table in paragraph (e) is amended by adding the entry ``(56)'' 
in numerical order.
    The additions read as follows:


Sec.  52.820  Identification of plan.

* * * * *
    (d) * * *

                                EPA-Approved Iowa Source-Specific Orders/Permits
----------------------------------------------------------------------------------------------------------------
                                     Order/ permit       State
          Name of source                  No.       effective date    EPA approval date         Explanation
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
(170) MidAmerican Energy Co.--         05-A-031-P6       7/20/2023  [Date of publication   Regional Haze Plan
 Louisa Station.                                                     of the final rule in   for the second
                                                                     the Federal            implementation
                                                                     Register], [Federal    period; condition 11
                                                                     Register citation of   of the permit is not
                                                                     the final rule].       part of the SIP.
(171) MidAmerican Energy Co--          75-A-357-P9       7/20/2023  [Date of publication   Regional Haze Plan
 Walter Scott Jr. Energy Center.                                     of the final rule in   for the second
                                                                     the Federal            implementation
                                                                     Register], [Federal    period; condition 11
                                                                     Register citation of   of the permit is not
                                                                     the final rule].       part of the SIP.
(172) MidAmerican Energy Company--     03-A-425-P4       12/5/2011  [Date of publication   Regional Haze Plan
 Walter Scott, Jr. Energy Center.                                    of the final rule in   for the second
                                                                     the Federal            implementation
                                                                     Register], [Federal    period; condition 6
                                                                     Register citation of   of the permit is not
                                                                     the final rule].       part of the SIP.
----------------------------------------------------------------------------------------------------------------

    (e) * * *

                                   EPA-Approved Iowa Nonregulatory Provisions
----------------------------------------------------------------------------------------------------------------
   Name of nonregulatory SIP      Applicable geographic or         State        EPA approval
           provision                 nonattainment area       submittal date        date           Explanation
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
(56) Iowa Regional Haze Plan    Statewide...................       8/15/2023  [Date of          [EPA-R07-OAR-202
 for the Second Implementation                                                 publication of    4-0313; FRL-
 Period.                                                                       the final rule    12096-01-R7].
                                                                               in the Federal
                                                                               Register],
                                                                               [Federal
                                                                               Register
                                                                               citation of the
                                                                               final rule].
----------------------------------------------------------------------------------------------------------------


[[Page 63279]]

0
3. Revise Sec.  52.842 to read as follows:


Sec.  52.842   Visibility protection.

    (a) The requirements of section 169A of the Clean Air Act are met 
because the Regional Haze plan submitted by Iowa on March 25, 2008, and 
supplemented on May 14, 2019, includes fully approvable measures for 
meeting the requirements of the Regional Haze Rule including 40 CFR 
51.308(d)(3) and (e) with respect to emissions of NOX and 
SO2 from electric generating units.
    (b) The requirements of section 169A of the Clean Air Act are met 
because the Regional Haze plan submitted by Iowa on August 15, 2023, 
includes fully approvable measures for meeting the requirements of the 
Regional Haze Rule in 40 CFR 51.308.

[FR Doc. 2024-16502 Filed 8-1-24; 8:45 am]
BILLING CODE 6560-50-P