# Air Plan Partial Approval and Partial Disapproval; Utah; Regional Haze State Implementation Plan for the Second Implementation Period; Air Plan Disapproval; Utah; Interstate Transport of Air Pollution for the 2015 8-Hour Ozone National Ambient Air Quality Standards

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2024-18462

## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** August 19, 2024
- **Citation:** 89 FR 67208

## Text

ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R08-OAR-2024-0389; FRL-12173-01-R8]
Air Plan Partial Approval and Partial Disapproval; Utah; Regional Haze State Implementation Plan for the Second Implementation Period; Air Plan Disapproval; Utah; Interstate Transport of Air Pollution for the 2015 8-Hour Ozone National Ambient Air Quality Standards

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

In this notice of proposed rulemaking, the Environmental Protection Agency (EPA) is proposing to act on two Utah State implementation plan (SIP) submissions related to visibility protection. First, we are proposing to partially approve and partially disapprove a regional haze SIP submission for the second implementation period that Utah submitted on August 2, 2022. The regional haze SIP submission addresses the requirement that states revise their long-term strategies every implementation period to make 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. Utah's regional haze SIP submission also addresses other applicable requirements for the second implementation period of the regional haze program. The EPA is taking this action on Utah's regional haze SIP submission pursuant to the Clean Air Act (CAA or the Act). Second, the EPA is proposing to disapprove a portion of Utah's infrastructure SIP submission submitted on January 9, 2020, to address the applicable requirements of CAA section 110(a)(2) for the 2015 Ozone National Ambient Air Quality Standards (NAAQS). Our proposed disapproval is based on CAA section 110(a)(2)(D)(i)(II)'s requirement that a state's SIP contain adequate provisions prohibiting emissions that will interfere with measures to protect visibility required to be included in any other state's SIP (known as interstate transport “prong 4”). The EPA is taking this action on Utah's infrastructure SIP submission pursuant to section 110 of the CAA.

DATES:

Written comments must be received on or before September 18, 2024.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-R08-OAR-2024-0389 at
https://www.regulations.gov.
Follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from
https://www.regulations.gov.
The EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission (
i.e.,
on the web, cloud, or other file sharing system). For additional submission methods, the full public comment policy of the EPA, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit
https://www.epa.gov/dockets/commenting-epa-dockets.

Docket:
All documents in the docket are listed in the
https://www.regulations.gov
index. Although listed in the index, some information is not publicly available,
e.g.,
CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly available docket materials are available electronically in
https://www.regulations.gov.
Please email or call the person listed in the
FOR FURTHER INFORMATION CONTACT
section if you need to make alternative arrangements for access to the docket.

FOR FURTHER INFORMATION CONTACT:

Clayton Bean, U.S. Environmental Protection Agency, Region 8, Air and Radiation Division; 1595 Wynkoop Street, Denver, Colorado 80202-1129; telephone: (303) 312-6143; email address:
bean.clayton@epa.gov.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. What action is the EPA proposing?

II. Background and Requirements for Regional Haze Plans

A. Regional Haze Background

B. Roles of Agencies in Addressing Regional Haze

C. Background on Utah's First Implementation Period SIP

D. Utah's Second Implementation Period SIP Submission

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

A. Identification of Class I Areas

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

C. Long-Term Strategy for Regional Haze

D. Reasonable Progress Goals

E. Monitoring Strategy and Other State Implementation Plan Requirements

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

G. Requirements for State and Federal Land Manager Coordination

IV. The EPA's Evaluation of Utah's Regional Haze Submission 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

D. Reasonable Progress Goals

E. Reasonably Attributable Visibility Impairment

F. Monitoring Strategy and Other State Implementation Plan Requirements

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

H. Requirements for State and Federal Land Manager Coordination

V. Interstate Transport Prong 4 (Visibility) for the 2015 Ozone NAAQS Infrastructure SIP

A. Infrastructure SIPs

B. Prong 4 Requirements

C. Utah's Prong 4 Elements

D. The EPA's Evaluation of Utah's Submittal

VI. Proposed Action

VII. Environmental Justice

VIII. Statutory and Executive Order Reviews

I. What action is the EPA proposing?

In this notice of proposed rulemaking, the EPA is proposing to take action on two Utah SIP submissions related to visibility protection. First, as detailed in section IV., the EPA's Evaluation of Utah's Regional Haze Submission for the Second Implementation Period, we are proposing to partially approve and partially disapprove Utah's regional haze second implementation period SIP submission. Second, as a consequence of our proposed partial disapproval of the regional haze SIP submission and as detailed in section V. of this document, we are proposing to disapprove a portion of Utah's infrastructure SIP for the 2015 ozone NAAQS.

On August 2, 2022, the Utah Department of Environmental Quality's Division of Air Quality (DAQ) submitted a SIP submission to the EPA to address regional haze for the second implementation period. Utah made this SIP submission to satisfy the requirements of the CAA's regional haze program pursuant to CAA sections 169A and 169B and 40 CFR 51.308(f). The EPA is proposing to approve the portions of Utah's Regional Haze SIP

submission relating to 40 CFR 51.308(f)(1): calculations of baseline, current, and natural visibility conditions, progress to date, and the uniform rate of progress; (f)(4): reasonably attributable visibility impairment; (f)(5) and (g): progress report requirements; and (f)(6): monitoring strategy and other implementation plan requirements. The EPA is proposing disapproval for the portions of Utah's regional haze SIP submission relating to 40 CFR 51.308(f)(2): long-term strategy; (f)(3): reasonable progress goals; and (i): FLM consultation. Consistent with section 110(k)(3) of the CAA, the EPA may partially approve portions of a SIP submittal if those elements meet all applicable requirements and may disapprove the remainder so long as the elements are fully separable.

Additionally, the EPA proposes to disapprove a portion of Utah's January 9, 2020 infrastructure SIP submission for the 2015 ozone NAAQS that addresses interstate transport of visibility impairing pollutants. Utah submitted this SIP submission to address the applicable requirements of CAA section 110(a)(2) for the 2015 ozone NAAQS. We propose to disapprove the portion of the infrastructure SIP submission addressing interstate transport of visibility impairing pollutants for not meeting the requirements of CAA section 110(a)(2)(D)(i)(II).

II. Background and Requirements for Regional Haze Plans

A. Regional Haze Background

In the 1977 CAA amendments, Congress created a program for protecting visibility in the nation's mandatory Class I Federal areas, which include certain national parks and wilderness areas.
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 and 51.309,
2

on July 1, 1999 (64 FR 35714, July 1, 1999). On January 10, 2017, the EPA promulgated additional regulations that address visibility impairment for the second and subsequent implementation periods (82 FR 3078, January 10, 2017). These regional haze regulations are a central component of the EPA's comprehensive visibility protection program for Class I areas.

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 requirements under 40 CFR 51.309(d)(4) contain general requirements pertaining to stationary sources and market trading and allow states to adopt alternatives to the point source application of BART.

Regional haze is visibility impairment that is produced by a multitude of anthropogenic sources and activities that 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 (SO
2
), nitrogen oxides (NO
X
), and, in some cases, volatile organic compounds (VOC) and ammonia (NH
3
)). Fine particle precursors react in the atmosphere to form fine particulate matter (PM
2.5
), which impairs visibility by scattering and absorbing light. Visibility impairment reduces the perception of clarity and color, as well as visible distance.
3

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.

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.

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).

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 implementation period
6

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).

6
The EPA uses the terms “implementation period” and “planning period” interchangeably.

States were also required to calculate baseline (using the five-year period of 2000-2004) and natural visibility conditions (
i.e.,
visibility conditions without anthropogenic visibility impairment) for each Class I area, and to calculate the linear rate of progress needed to attain natural visibility conditions, assuming a starting point of baseline visibility conditions in 2004 and ending with natural conditions in 2064. This linear interpolation is known as the uniform rate of progress (URP) and is used as a tracking metric to help states assess the amount of progress they are making towards the national visibility goal over time in each Class I area.
7

40 CFR 51.308(d)(1)(i)(B), (d)(2). The 1999 RHR also provided that states' long-term strategies must include the “enforceable emissions limitations, compliance schedules, and other measures as necessary to achieve the reasonable progress goals.” 40 CFR 51.308(d)(3). In establishing their long-term strategies, states are required to consult with other states that also contribute to visibility impairment in a given Class I area and include all measures necessary to obtain their shares of the emission reductions needed to meet the RPGs. 40 CFR 51.308(d)(3)(i), (ii). Section 51.308(d) also contains seven additional factors states must consider in formulating their long-term strategies (see 40 CFR 51.308(d)(3)(v)), as well as provisions governing monitoring and other implementation plan requirements. 40 CFR 51.308(d)(4). Finally, the 1999 RHR required states to submit periodic progress reports—SIP revisions due every five years that contain information on states' implementation of their regional haze plans and an assessment of whether anything additional is needed to make reasonable progress, see 40 CFR 51.308(g), (h)—and to consult with the Federal Land Manager(s)
8

(FLMs) responsible for each Class I area according to the requirements in CAA section 169A(d) and 40 CFR 51.308(i).

7
The EPA established the URP framework in the 1999 RHR to provide “an equitable analytical approach” to assessing the rate of visibility improvement at Class I areas across the country. The starting point for the URP analysis is 2004 and the endpoint was calculated based on the amount of visibility improvement that was anticipated to result from implementation of existing CAA programs over the period from the mid-1990s to approximately 2005. Assuming this rate of progress would continue into the future, the EPA determined that natural visibility conditions would be reached in 60 years, or 2064 (60 years from the baseline starting point of 2004). However, the EPA did not establish 2064 as the year by which the national goal
must
be reached. 64 FR 35731-32. That is, the URP and the 2064 date are not enforceable targets but are rather tools that “allow for analytical comparisons between the rate of progress that would be achieved by the state's chosen set of control measures and the URP. (82 FR 3078, 3084, January 10, 2017).

8
The EPA's regulations define “Federal Land Manager” as “the Secretary of the department with authority over the Federal Class I area (or the Secretary's designee) or, with respect to Roosevelt-Campobello International Park, the Chairman of the Roosevelt-Campobello International Park Commission.” 40 CFR 51.301.

On January 10, 2017, the EPA promulgated revisions to the RHR (82 FR 3078, January 10, 2017) that apply for the second and subsequent implementation periods. The 2017 rulemaking made several changes to the requirements for regional haze SIPs to clarify states' obligations and streamline certain regional haze requirements. The revisions to the regional haze program for the second and subsequent implementation periods focused on the requirement that states' SIPs contain long-term strategies for making reasonable progress towards the national visibility goal. The reasonable progress requirements as revised in the 2017 rulemaking (referred to here as the 2017 RHR Revisions) are codified at 40 CFR 51.308(f). Among other changes, the 2017 RHR Revisions adjusted the deadline for states to submit their second implementation period SIPs from July 31, 2018, to July 31, 2021, clarified the order of analysis and the relationship between RPGs and the long-term strategy, and focused on making visibility improvements on the days with the most
anthropogenic
visibility impairment, as opposed to the days with the most visibility impairment overall. The EPA also revised requirements of the visibility protection program related to periodic progress reports and FLM consultation. The specific requirements applicable to second implementation period regional haze SIP submissions are addressed in detail below.

The EPA provided guidance to the states for their second implementation period SIP submissions in the preamble to the 2017 RHR Revisions as well as in subsequent, stand-alone guidance documents. In August 2019, the EPA issued “Guidance on Regional Haze State Implementation Plans for the Second Implementation Period” (“2019 Guidance”).
9

On July 8, 2021, the EPA issued a memorandum containing “Clarifications Regarding Regional Haze State Implementation Plans for the Second Implementation Period” (“2021 Clarifications Memo”).
10

Additionally, the EPA further clarified the recommended procedures for processing ambient visibility data and optionally adjusting the URP to account for international anthropogenic and prescribed fire impacts in two technical guidance documents: the December 2018 “Technical Guidance on Tracking Visibility Progress for the Second Implementation Period of the Regional Haze Program” (“2018 Visibility Tracking Guidance”),
11

and the June 2020 “Recommendation for the Use of Patched and Substituted Data and Clarification of Data Completeness for Tracking Visibility Progress for the Second Implementation Period of the Regional Haze Program” and associated

Technical Addendum (“2020 Data Completeness Memo”).
12

9
Guidance on Regional Haze State Implementation Plans for the Second Implementation Period.
https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period.
The EPA Office of Air Quality Planning and Standards, Research Triangle Park (August 20, 2019).

10
Clarifications Regarding Regional Haze State Implementation Plans for the Second Implementation Period.
https://www.epa.gov/system/files/documents/2021-07/clarifications-regarding-regional-haze-state-implementation-plans-for-the-second-implementation-period.pdf.
The EPA Office of Air Quality Planning and Standards, Research Triangle Park (July 8, 2021).

11
Technical Guidance on Tracking Visibility Progress for the Second Implementation Period of the Regional Haze Program.
https://www.epa.gov/visibility/technical-guidance-tracking-visibility-progress-second-implementation-period-regional.
The EPA Office of Air Quality Planning and Standards, Research Triangle Park (December 20, 2018).

12
Recommendation for the Use of Patched and Substituted Data and Clarification of Data Completeness for Tracking Visibility Progress for the Second Implementation Period of the Regional Haze Program.
https://www.epa.gov/visibility/memo-and-technical-addendum-ambient-data-usage-and-completeness-regional-haze-program.
The EPA Office of Air Quality Planning and Standards, Research Triangle Park (June 3, 2020).

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.
13

13
See,
e.g.,
H.R. Rep. No. 95-294 at 205 (“In determining how to best remedy the growing visibility problem in these areas of great scenic importance, the committee realizes that as a matter of equity, the national ambient air quality standards cannot be revised to adequately protect visibility in all areas of the country.”) (“the mandatory Class I increments of [the PSD program] do not adequately protect visibility in Class I areas”).

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),
14

which include representation from state and Tribal governments, the EPA, and FLMs, were developed in the lead-up to the first implementation period to address regional haze. RPOs evaluate technical information to better understand how emissions from state and tribal land impact Class I areas across the country, pursue the development of regional strategies to reduce emissions of particulate matter and other pollutants leading to regional haze, and help states meet the consultation requirements of the RHR.

14
RPOs are sometimes also referred to as “multi-jurisdictional organizations,” or MJOs. For the purposes of this document, the terms RPO and MJO are synonymous.

The Western Regional Air Partnership (WRAP), one of the five RPOs described in the previous paragraph, is a collaborative effort of State governments, local air agencies, Tribal governments, and various Federal agencies established to initiate and coordinate activities associated with the management of regional haze, visibility, and other air quality issues in the western United States. Members include the States of Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, North Dakota, Oregon, South Dakota, Utah, Washington, Wyoming, and 28 Tribal governments.
15

The Federal partner members of WRAP are the EPA, U.S. National Parks Service (NPS), U.S. Fish and Wildlife Service (USFWS), U.S. Forest Service (USFS), and the U.S. Bureau of Land Management (BLM).

15
A full list of WRAP members is available at
https://www.westar.org/wrap-council-members/.

The WRAP membership formed a workgroup to develop a planning framework for state regional haze second implementation period SIPs. Based on emissions inventories and monitoring data supplied by its membership, WRAP produced a technical system to support regional modeling of visibility impacts at Class I areas across the West. The WRAP Technical Support System (TSS) consolidated air quality monitoring data, meteorological and receptor modeling data analyses, emissions inventories and projections, and gridded air quality/visibility regional modeling results. The WRAP TSS is accessible by member States and allows for the creation of maps, figures, and tables to export and use in SIP development. WRAP TSS also maintains the original source data for verification and further analysis. Utah relied on the WRAP TSS products and Interagency Monitoring of Protected Visual Environments (IMPROVE) data to determine visibility conditions and impacts at in-state and out-of-state Class I areas.

C. Background on Utah's First Implementation Period SIP

The CAA required that regional haze plans for the first implementation period include both a long-term strategy for making reasonable progress and BART requirements for certain older stationary sources, where applicable.
16

Utah submitted SIP revisions addressing regional haze for the first implementation period in September 2008 and May 2011. In 2012, the EPA partially approved and partially disapproved Utah's 2008 and 2011 SIP submissions, which included disapproval of NO
X
and PM BART for subject-to-BART sources.
17

16
Requirements for regional haze SIPs for the first implementation period are contained in Clean Air Act section 169A(b)(2). The RHR provided two paths for states to address regional haze in the first implementation period. Most states must follow 40 CFR 51.308(d) and (e), which require states to perform individual point source BART determinations and evaluate the need for other control strategies. The requirements for addressing regional haze visibility impairment in the sixteen Class I areas covered by the Grand Canyon Visibility Transport Commission are found in 40 CFR 51.309(d)(4), which contains general requirements pertaining to stationary sources and market trading and allows states to adopt alternatives to the point source application of BART. See also 40 CFR 51.308(b). States with Class I areas covered by the Grand Canyon Visibility Transport Commission could choose to submit a regional haze SIP under 40 CFR 51.308 or 51.309.

17
77 FR 74355, 74357 (Dec. 14, 2012).

In June 2015, Utah submitted a SIP revision to address the NO
X
and PM BART determinations we had previously disapproved. In 2016, the EPA partially approved and partially disapproved the June 2015 SIP submission and promulgated a Federal implementation plan (FIP) for NO
X
BART at Hunter Units 1, 2, and 3, and Huntington Units 1 and 2.
18

18
81 FR 43894, 43896, 43907 (July 5, 2016).

In 2019, Utah submitted a new SIP revision for NO
X
BART.
19

In November 2020, the EPA approved Utah's 2019 SIP submission and concurrently withdrew the 2016 FIP.
20

19
On December 3, 2019, Utah submitted a supplement to the July 3, 2019 SIP submission that included an amendment to the monitoring, recordkeeping, and reporting requirements.

20
85 FR 75860 (Nov. 27, 2020).

Utah submitted its first implementation period progress report in 2016 to meet the requirements of 40 CFR 51.308(g) and (h). The progress report described progress toward the reasonable progress goals and contained a determination of adequacy of Utah's regional haze SIP to achieve established goals for visibility improvement and

emissions reductions. The EPA approved the progress report in 2020.
21

21
85 FR 64050 (Oct. 9, 2020).

D. Utah's Second Implementation Period SIP Submission

In accordance with CAA section 169A and the RHR at 40 CFR 51.308(f), on August 2, 2022, Utah made a SIP submission to the EPA to address the State's regional haze obligations for the second implementation period.
22

Prior to submission, Utah made its draft regional haze SIP available for public comment from May 1, 2022, to May 31, 2022, and held a public hearing on May 26, 2022. The public comments and Utah's responses are contained in the State's regional haze SIP submission and are available in the docket for this action.

22
Utah's regional haze SIP submission comprises several documents that are available in the docket for this action. The document titled “Utah Regional Haze SIP Submittal 2022 v2” is a PDF totaling 491 pages that Utah submitted to the EPA on August 2, 2022. This document includes both Utah's final regional haze SIP narrative (titled “Utah State Implementation Plan, Regional Haze Second Implementation Period, Section XX.A” and dated August 1, 2022) and the draft regional haze SIP that Utah proposed for public comment in May 2022 during its State public comment process. The EPA is not evaluating Utah's draft public comment version of the regional haze SIP. Therefore, for the reader's convenience, we have included a standalone document in the docket for this action titled “Final SIP Only—Utah Regional Haze SIP Submittal 2022 v2.” This document contains only the submittal letter, Legal Authority, Public Comments, Final Effective Rule, Final Effective Plans, and Certification portions of Utah's August 2, 2022 SIP submission. We created this document to help the public avoid confusion between the State's public comment draft SIP and final SIP. In this notice of proposed rulemaking, our references to page numbers in Utah's regional haze SIP submission are based on the internal pagination of the “Utah State Implementation Plan, Regional Haze Second Implementation Period, Section XX.A” dated August 1, 2022.

As part of its SIP submission, Utah also submitted a 704-page PDF titled “Utah State Implementation Plan Appendices,” which contains a collection of technical documents and communications. This PDF is also available in the docket for this action. Because many portions of the PDF are illegible due to poor quality, we have included a legible version of each individual document contained within the larger “Utah State Implementation Plan Appendices” PDF in the docket for this action. In this notice of proposed rulemaking, our references to page numbers in appendices to Utah's regional haze SIP submission are based on the internal pagination of the legible individual documents.

Section IV of this document describes Utah's regional haze SIP submission, including the four-factor analyses conducted by certain sources that Utah identified as potential contributors to visibility impairment, and Utah's determinations of the emissions reduction measures necessary to make reasonable progress based on those analyses. The regional haze SIP submission also includes Utah's assessment of progress made since the first implementation period in reducing emissions of visibility impairing pollutants, as well as visibility progress at in-state and out-of-state Class I areas. Section IV also contains the EPA's evaluation of Utah's SIP submission against the requirements of the CAA and RHR (as described in section III. of this document). The entirety of Utah's regional haze SIP submission is included in the docket for this action.

We have also included a Technical Support Document (TSD) in the docket to provide technical information and analysis supporting our proposed action on the Utah regional haze SIP submission. The TSD includes our review of the WRAP analyses that Utah relied on during the State's regional haze second implementation period SIP development process.

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

Under the CAA and the EPA's regulations, all 50 states, the District of Columbia, and the U.S. Virgin Islands 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, 40 CFR 51.308(f) lays out the process by which states determine what constitutes their long-term strategies, with the order of the requirements in § 51.308(f)(1) through (3) generally mirroring the order of the steps in the reasonable progress analysis
23

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”
24

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).

23
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.

24
The five “additional factors” for consideration in § 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.

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 § 51.308(g)(1) through (5) pertaining to periodic reports describing progress towards the RPGs, 40 CFR 51.308(f)(5), as well as requirements for FLM consultation that apply to all visibility protection SIPs and SIP revisions. 40 CFR 51.308(i).

A state must submit its regional haze SIP and subsequent SIP revisions to the EPA according to the requirements applicable to all SIP revisions under the CAA and the EPA's regulations. See

CAA section 169A(b)(2); CAA section 110(a). Upon approval by the EPA, a SIP is enforceable by the Agency and the public under the CAA. If the EPA finds that a state fails to make a required SIP revision, or if the EPA finds that a state's SIP is incomplete or if it disapproves the SIP, the Agency must promulgate a 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 (see 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, the EPA's 2019 Guidance provides recommendations for how such an assessment might be accomplished, including by, where appropriate, using the determinations previously made for the first implementation period. 2019 Guidance at 8-9. In addition, the determination of which Class I areas may be affected by a state's emissions is subject to the requirement in 40 CFR 51.308(f)(2)(iii) to “document the technical basis, including modeling, monitoring, cost, engineering, and emissions information, on which the State is relying to determine the emission reduction measures that are necessary to make reasonable progress in each mandatory Class I Federal area it affects.”

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

As part of assessing whether a SIP submission for the second implementation period is providing for reasonable progress towards the national visibility goal, the RHR contains requirements in § 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. The EPA's 2018 Visibility Tracking Guidance
25

provides recommendations to assist states in satisfying their obligations under § 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.

25
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).
26

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,
27

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.

26
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.

27
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.
28

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.

28
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.

The EPA's 2018 Visibility Tracking Guidance can be used to help satisfy the 40 CFR 51.308(f)(1) requirements, including in developing information on baseline, current, and natural visibility conditions, and in making optional adjustments to the URP. In addition, the 2020 Data Completeness Memo provides recommendations on the data completeness language referenced in § 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 outside the state that may be affected by emissions from the state. The long-term strategy “must include the enforceable emissions limitations, compliance schedules, and

other measures that are necessary to make reasonable progress, as determined pursuant to (f)(2)(i) through (iv).” 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 the EPA previously explained, consistent with the first implementation period, the EPA generally expects that each state will analyze at least SO
2
and NO
X
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.

The EPA explained in the 2021 Clarifications Memo that each state has an obligation to submit a long-term strategy that addresses the regional haze visibility impairment that results from emissions from within that state. Thus, source selection should focus on the in-state contribution to visibility impairment and be designed to capture a meaningful portion of the state's total contribution to visibility impairment in Class I areas. A state should not decline to select its largest in-state sources on the basis that there are even larger out-of-state contributors. 2021 Clarifications Memo at 4.
29

29
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.
30

This is accomplished by considering the four factors—“the costs of compliance, the time necessary for compliance, and the energy and nonair quality environmental impacts of compliance, and the remaining useful life of any existing source subject to such requirements.” CAA section 169A(g)(1). The EPA has explained that the four-factor analysis is an assessment of potential emission reduction measures (
i.e.,
control options) for sources; “use of the terms `compliance' and `subject to such requirements' in section 169A(g)(1) strongly indicates that Congress intended the relevant determination to be the requirements with which sources would have to comply to satisfy the CAA's reasonable progress mandate.” 82 FR 3091. Thus, for each source it has selected for four-factor analysis,
31

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.

30
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 implementation period.

31
“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.

The EPA's 2021 Clarifications Memo provides further guidance on what constitutes a reasonable set of control options for consideration: “A reasonable four-factor analysis will consider the full range of potentially reasonable options for reducing emissions.” 2021 Clarifications Memo at 7. In addition to add-on controls and other retrofits (
i.e.,
new emissions reduction measures for sources), the EPA explained that states should generally analyze efficiency improvements for sources' existing

measures as control options in their four-factor analyses, as in many cases such improvements are reasonable given that they typically involve only additional operation and maintenance costs. Additionally, the 2021 Clarifications Memo provides that states that have assumed a higher emissions rate than a source has achieved or could potentially achieve using its existing measures should also consider lower emissions rates as potential control options. That is, a state should consider a source's recent actual and projected 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.
32

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, § 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.”

32

See, e.g.,
Responses to Comments on Protection of Visibility: Amendments to Requirements for State Plans; Proposed Rule (81 FR 26942, May 4, 2016), Docket ID No. EPA-HQ-OAR-2015-0531, U.S. Environmental Protection Agency at 186; 2019 Guidance at 36-37.

As explained above, § 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 § 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.
33

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.

33
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 § 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, § 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.
34

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.

34

See Arizona ex rel. Darwin
v.
U.S. EPA,
815 F.3d 519, 531 (9th Cir. 2016);
Nebraska
v.
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.
Nat'l Parks Conservation Ass'n
v.
EPA,
803 F.3d 151, 165 (3d Cir. 2015);
Alaska Dep't of Envtl. Conservation
v.
EPA,
540 U.S. 461, 485, 490 (2004).

The four statutory factors (and potentially visibility) are used to determine what emission reduction measures for selected sources must be included in a state's long-term strategy for making reasonable progress. Additionally, the RHR at 40 CFR 51.3108(f)(2)(iv) separately provides five “additional factors”
35

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 implementation 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.

35
The five “additional factors” for consideration in § 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, § 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 for Class I areas within the state. 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.
36

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.

36
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.

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, § 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 that show 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 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) and (iii). Section 51.308(f)(6)(v) further requires that all states' SIPs provide for a statewide inventory of emissions of pollutants that are reasonably anticipated to cause or contribute to visibility impairment in any Class I area; the inventory must include emissions for the most recent year for which data are available and estimates of future projected emissions. States must also include commitments to update their inventories periodically. The inventories themselves do not need to be included as elements in the SIP and are not subject to the EPA's review as part of the Agency's evaluation of a SIP revision.
37

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.
38

37
See “Step 8: Additional requirements for regional haze SIPs” in the 2019 Guidance at 55.

38

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 § 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.”
39

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.

39
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 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, § 51.308(g)(3) requires states with Class I areas within their borders to first determine current visibility conditions for each area on the most impaired and clearest days, 40 CFR 51.308(g)(3)(i), 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). 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), (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).

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

In section IV of this document, we summarize Utah's regional haze SIP submission and evaluate it against the requirements of the CAA and RHR for the second implementation period of the regional haze program.

A. 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 paragraph (f)(2), which requires each state's plan to include a long-term strategy that addresses regional haze in such Class I areas.

The EPA explained in the 1999 RHR preamble that the CAA section 169A(b)(2) requirement that states submit SIPs to address visibility impairment establishes “an `extremely low triggering threshold' in determining which States should submit SIPs for regional haze.” 64 FR 35721. In concluding that each of the contiguous 48 states and the District of Columbia meet this threshold,
40

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.

40
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.

Utah has five mandatory Federal Class I Federal areas within its borders: Arches National Park, Bryce Canyon National Park, Canyonlands National Park, Capitol Reef National Park, and Zion National Park. These five mandatory Class I areas are located within the physiographic region known as the Colorado Plateau.
41

41
National Park Service, “Colorado Plateaus Province,”
https://www.nps.gov/articles/coloradoplateaus.htm
(last accessed July 24, 2024); National Park Service, “Colorado Plateaus Province: U.S. Physiographic Province Map,”

https://www.nps.gov/common/uploads/photogallery/nri/park/geology/49177B13-1DD8-B71B-0BF120CC77B24F45/49177B13-1DD8-B71B-

0BF120CC77B24F45-large.jpg

(last accessed July 24, 2024).

Additionally, based on its review of WRAP's source apportionment modeling
42

and weighted emission potential (WEP) analysis,
43

Utah identified at least 45 Class I areas outside the State where visibility may be affected by Utah sources.
44

Those Class I areas are listed in tables 26 and 30 of the TSD for this action.

42
For its source apportionment modeling, WRAP used its emissions inventories, including projections of future emissions, as inputs to a photochemical model that assesses light extinction (
i.e.,
visibility impairment) at each Class I area. More detail on source apportionment modeling is provided in the EPA's TSD for this action.

43
WEP is a quantitative method of analyzing how pollutants from particular sources may be transported to Class I areas. More detail on WRAP's WEP analysis is provided in the EPA's TSD for this action.

44
Utah tabulated 30 IMPROVE receptor sites located in adjacent neighboring states in tables 21-22 of the Utah regional haze SIP submission at 77-78. These sites represent 45 Class I areas. We have identified numerous other Class I areas, beyond Utah's neighboring states, that are impacted by light extinction originating from the NO
X
and SO
2
emissions of Utah's sources. The forty-five out-of-state Class I areas identified for sulfate light extinction impacts represent 29% of all mandatory Class I areas, and the 45 out-of-state Class I areas identified for nitrate impacts also represent 29% of all mandatory Class I areas. At a minimum, the emissions sources identified by Utah impact visibility in more than a quarter of the 156 mandatory Class I areas nationwide.

B. 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).

Utah relied on WRAP TSS products and IMPROVE data to determine visibility conditions at its five in-state Class I areas.
45

Utah elected not to adjust the URP for those Class I areas for this implementation period.

45
Utah regional haze SIP submission, chapter 4 and section 8.C.

Visibility impairing particulate species at Class I areas are measured and analyzed through the IMPROVE network. The IMPROVE network uses identical sampling equipment and analysis protocols to ensure that IMPROVE sites and their respective data are directly comparable. Samples collected from IMPROVE monitors provide estimations of light extinction
46

to monitor visibility conditions and compare long-term visibility trends at Class I areas. IMPROVE monitoring data is also used to determine the 20% most anthropogenically impaired days (most impaired days) and the 20% clearest days every year at each Class I area and to track visibility impairment over time, as required by the RHR.

46
The primary cause of regional haze is light extinction by particulate matter (PM). For purposes of regional haze, light extinction is estimated from measurements of PM and its chemical components (sulfate, nitrate, organic mass by carbon (OMC), light absorbing carbon, fine soil, sea salt, and coarse material), assumptions about relative humidity at the monitoring site, and the use of a commonly accepted algorithm. These estimates of light extinction are logarithmically transformed to deciviews (dv). The PM measurements used in the regional haze program are collected by the IMPROVE monitoring network.

Due to their remote nature and/or close proximity to each other, several Class I areas throughout the United States share a common IMPROVE monitoring station.
47

Four IMPROVE monitors measure visibility conditions at the five Class I areas in Utah. The IMPROVE monitor at Canyonlands National Park has been determined to also be representative of the visibility conditions at Arches National Park.

47
Utah identified several Class I areas where visibility is affected by emissions from Utah sources, some of which share a single IMPROVE monitoring station. The IMPROVE Site IDs for these Class I areas are: BRID1 for Bridger Wilderness and Fitzpatrick Wilderness; CANY1 for Arches National Park and Canyonlands National Park; GUMO1 for Carlsbad Caverns National Park and Guadalupe Mountains National Park; NOAB1 for North Absaroka Wilderness and Washakie Wilderness; SULA1 for Anaconda-Pintler Wilderness and Selway-Bitterroot Wilderness; WEMI1 for Black Canyon of the Gunnison National Monument, La Garita Wilderness, and Weminuche Wilderness; WHPE1 for Pecos Wilderness and Wheeler Peak Wilderness; and WHRI1 for Eagles Nest Wilderness, Flat Tops Wilderness, Maroon Bells-Snowmass Wilderness, and West Elk Wilderness.

Utah determined that Arches National Park and Canyonlands National Park (CANY1) have 2000-2004 baseline visibility conditions of 3.75 deciviews on the 20% clearest days and 8.79 deciviews on the 20% most impaired days. Utah calculated an estimated natural background visibility of 1.05 deciviews on the 20% clearest days and 4.13 deciviews on the 20% most impaired days. The current visibility conditions, which are based on 2014-2018 monitoring data, were 2.20 deciviews on the clearest days and 6.76 deciviews on the most impaired days, which are 1.15 deciviews and 2.63 deciviews greater than natural conditions on the respective sets of days. The five-year rolling average IMPROVE data from 2014-2018 indicate that Arches National Park and Canyonlands National Park are 0.9 deciviews below the 2018 URP of 7.7 deciviews.
48

48
Utah regional haze SIP submission at 175 (figure 66).

Utah determined that Bryce Canyon National Park (BRCA1) has 2000-2004 baseline visibility conditions of 2.77 deciviews on the 20% clearest days and 8.42 deciviews on the 20% most impaired days. Utah calculated an estimated natural background visibility of 0.57 deciviews on the 20% clearest days and 4.08 deciviews on the 20% most impaired days. The current visibility conditions, which are based on 2014-2018 monitoring data, were 1.46 deciviews on the clearest days and 6.60 deciviews on the most impaired days, which are 0.89 deciviews and 2.52 deciviews greater than natural conditions on the respective sets of days. The five-year rolling average IMPROVE data from 2014-2018 indicates that Bryce Canyon National Park is 0.8 deciviews below the 2018 URP of 7.4 deciviews.
49

49

Id.
at 174 (figure 65).

Utah determined that Capitol Reef National Park (CAPI1) has 2000-2004 baseline visibility conditions of 4.10 deciviews on the 20% clearest days and 8.78 deciviews on the 20% most impaired days. Utah calculated an estimated natural background visibility of 1.28 deciviews on the 20% clearest days and 4.00 deciviews on the 20% most impaired days. The current visibility conditions, which are based on 2014-2018 monitoring data, were 2.38 deciviews on the clearest days and 7.18 deciviews on the most impaired days, which are 1.10 deciviews and 3.18 deciviews greater than natural conditions on the respective sets of days. The five-year rolling average IMPROVE data from 2014-2018 indicate that Capitol Reef National Park is 0.5 deciviews below the 2018 URP of 7.7 deciviews.
50

50

Id.
at 176 (figure 67).

Utah determined that Zion National Park (ZICA1) has 2000-2004 baseline visibility conditions of 4.48 deciviews on the 20% clearest days and 10.40 deciviews on the 20% most impaired days. Utah calculated an estimated natural background visibility of 1.83 deciviews on the 20% clearest days and 5.26 deciviews on the 20% most

impaired days. The current visibility conditions, which are based on 2014-2018 monitoring data, were 3.86 deciviews on the clearest days and 8.75 deciviews on the most impaired days, which are 2.03 deciviews and 3.49 deciviews greater than natural conditions on the respective sets of days. The five-year rolling average IMPROVE data from 2014-2018 indicate that Zion National Park is 0.5 deciviews below the 2018 URP of 9.2 deciviews.
51

51

Id.
at 177 (figure 68).

Based on this information, which is provided in chapter 4 and section 8.C. of Utah's regional haze SIP submission, the EPA finds that the visibility condition calculations for all five Utah Class I areas meet the requirements of 40 CFR 51.308(f)(1). For this reason, we propose to approve the portions of Utah's regional haze SIP submission relating to 40 CFR 51.308(f)(1): calculations of baseline, current, and natural visibility conditions; progress to date; and the URP.

C. Long-Term Strategy

Each state having a Class I area within its borders or emissions that may affect visibility in any Class I area outside the state must develop a long-term strategy for making reasonable progress towards the national visibility goal for each impacted Class I area. 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 40 CFR 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).

1. Summary of Utah's Four-Factor Analyses and Long-Term Strategy to Make Reasonable Progress

a. Selection of Sources for Four-Factor Analysis

Utah relied on Q/d analysis to identify sources for consideration of the four statutory factors.
52

Q/d analysis results in a value that represents the ratio of an individual source's annual emissions of light-impairing emission precursors (NO
X
, SO
2
, and PM
10
) in combined tons (“Q”) divided by the distance in kilometers (“d”) between the source and the nearest Class I area. The larger the Q/d value, the greater the source's expected effect on visibility impairment in each associated Class I area. Utah chose a Q/d source selection threshold of ≥ 6, meaning that any source with a Q/d value greater than or equal to 6 was “screened in” to the pool of sources Utah believed were appropriate for consideration of the four factors.
53

Following Q/d analysis, Utah then conducted a “secondary screening to review the initial pool of Q/d-qualifying sources to account for factors such as recent emissions controls required by other air quality programs, facility closures, federal preemptions on state controls, etc.”
54

52
Utah regional haze SIP submission at 14, 99.

53
Utah used 2014 NEI emissions data to select sources for four-factor analysis. Utah performed an additional analysis using 2017 NEI emissions data at the EPA's request; no additional sources were captured.

54
Utah regional haze SIP submission at 77.

Utah's Q/d analysis initially screened in ten sources: Ash Grove Leamington Cement Plant, CCI Paradox Lisbon Natural Gas Plant, Graymont Cricket Mountain Plant, Intermountain Power Authority Intermountain Power Plant,
55

Kennecott Utah Copper Mine & Copperton Concentrator, Kennecott Utah Copper Power Plant Lab Tailings Impoundment, PacifiCorp Hunter Power Plant, PacifiCorp Huntington Power Plant, Sunnyside Cogeneration Facility, and US Magnesium Rowley Plant. Utah determined that four of those sources, Intermountain Power Authority Intermountain Power Plant; CCI Paradox Lisbon Natural Gas Plant; Kennecott Utah Copper Mine & Copperton Concentrator; and Kennecott Utah Copper Power Plant Lab Tailings Impoundment, were not required to perform four-factor analyses based on current emissions, 2028 projected emissions, or plant closures or emission control measures that were put in place after the 2014 base year inventory (which was used to determine sources' Q in the Q/d analysis).
56

Table 1 lists Utah's reasoning for not requiring four-factor analyses for the four sources.

55
Intermountain Power Plant is also referred to as Intermountain Generation Station or Intermountain.

56
Utah regional haze SIP submission at 100, 102.

BILLING CODE 6560-50-P

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Figure 1 below shows the six sources Utah selected for four-factor analysis and their proximity to the State's Class I areas. We have also included CCI Paradox Lisbon Natural Gas Plant in figure 1 because, as detailed in section IV.C.2.b. of this document, we find that Utah unreasonably excluded this source from four-factor analysis.

57
Utah initially selected Intermountain power plant to perform a four-factor analysis based on the plant's combined Q/d value of 193.6 (based on 2014 NO
X
, SO
2
, and PM
10
emissions totaling 28,946 tpy). Utah regional haze SIP submission 100. However, due to the source's planned retirement, Intermountain power plant's emissions were not included in the 2028OTBa2 emissions inventory projection or in WRAP's source apportionment modeling. Intermountain power plant's combined NO
X
, SO
2
, and PM
10
emissions, in 2022, were 10,174 tpy. 2022 EPA Emission Inventory System. By magnitude of emissions, in 2022, Intermountain power plant was the sixth highest emitter of NO
X
(behind Hunter power plant, the fifth highest emitter) and the 127th highest emitter of SO
2
in the United States. EPA Clean Air Markets Program Data; TSD at 11-12, Table 7. Intermountain power plant is further discussed in sections IV.C.2.c and IV.C.2.f. of this document.

58
Utah regional haze SIP submission at 104-05 and appendix G.

Figure 1. Sources Required to Perform Four-Factor Analysis and CCI Paradox Lisbon Natural Gas Plant

EP19AU24.001

Table 2 tabulates the Q/d values associated with each source that Utah selected for four-factor analysis, as well as CCI Paradox Lisbon Natural Gas Plant. Q/d values were calculated by Utah and WRAP.
59

Q/d values are not listed for out-of-state Class I areas located more than 400 kilometers from a selected source, as those Class I areas fell outside WRAP's and Utah's analysis threshold.
60

59
See WRAP_Threshold_Analysis.xlsm in the docket.

60
The WRAP and Utah Q/d methodology did not calculate Q/d values for any source located at a distance greater than 400 kilometers from a Class I area.

EP19AU24.002

EP19AU24.003

BILLING CODE 6560-50-C

Utah also compared the sources it selected through Q/d analysis to WRAP's Weighted Emissions Potential (WEP) analysis, which was released after Utah selected its sources. WEP is a quantitative method of analyzing the contribution of visibility impairing pollutants from individual sources to visibility impairment at individual Class I areas. WEP values are calculated by overlaying extinction weighted residence time with the future projected emissions of light extinction precursors to predict which sources may have the highest contribution potential to affect visibility at Class I areas on the 20% most impaired days. In other words, WEP is an analytical method that can identify significant emission sources that are upwind from a particular Class I area.
61

Based on its review of WEP results, Utah determined that its selection of sources for four-factor analysis sufficiently captured point sources that have the potential to affect visibility at in-state and out-of-state Class I areas.
62

61
WEP is calculated by overlaying extinction weighted residence time results with 2028OTBa2 emissions of light extinction precursors (
i.e.,
NO
X
emissions for ammonium nitrate light extinction and SO
2
emissions for ammonium sulfate light extinction). Extinction weighted residence time is calculated by weighting Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) back trajectories by the actual observed light extinction at IMPROVE sites on each Most Impaired Day. The results are then normalized by the sum of the WEP for the total anthropogenic emissions. WEP results include percentages of the total for nitrates and sulfates and the rankings by Class I areas. WRAP, “WEP/AOI Analysis for western U.S. Class I Areas,”
https://views.cira.colostate.edu/tssv2/WEP-AOI/
(last accessed July 24, 2024).

62
Utah regional haze SIP submission at 108.

b. Four-Factor Analyses

Each of the six sources that Utah selected through Q/d analysis prepared and submitted a four-factor analysis to the State. Utah provided each source with the State's evaluation of its four-factor analysis and received responses and other information submittals from each source.
63

Chapter 7.C of Utah's regional haze SIP submission describes

the sources' four-factor analyses, Utah's evaluations, the sources' responses and corrections, and Utah's conclusions.

63

Id.
at 14.

i. Ash Grove Leamington Cement Plant
64

64
The four-factor analyses for this facility are contained in the Utah regional haze SIP submission at 132-34 and appendix C.1.A.

Ash Grove Leamington Cement Plant is a cement manufacturing plant in Leamington, Utah. The facility has a combined Q/d value of 6.9; the nearest Class I area is Capitol Reef National Park at 134 kilometers away. Existing controls at the Leamington Cement Plant are low-NO
X
burners (LNB), selective non-catalytic reduction (SNCR), and a federally enforceable NO
X
emission rate of 2.8 lbs/ton clinker (30-day rolling average). Ash Grove identified six potential emission control technologies. It determined four of them to be technically infeasible; the remaining two are already installed at the plant. The results of Ash Grove's analysis are shown in table 3.

EP19AU24.004

In its review of Ash Grove's submission, Utah noted that Ash Grove could have evaluated more efficient or upgraded versions of LNB or SNCR.
65

Ash Grove responded that it was “not aware of any changes that could be made to achieve a higher level of control with the system.”
66

65
Utah regional haze SIP submission, appendix C.1.B. at 7.

66
Utah regional haze SIP submission, appendix C.1.C at 2.

Utah concluded that the Leamington Cement Plant is adequately controlled and that no additional emission reduction measures are required in the regional haze second implementation period. The State determined that the source's existing SNCR controls and emissions limits are necessary for reasonable progress.
67

67
Utah regional haze SIP submission at 178.

ii. Graymont Cricket Mountain Plant
68

68
The four-factor analyses for this facility are contained in the Utah regional haze SIP submission at 134-138, 179, and appendices C.2.A and C.2.C.

The Graymont Cricket Mountain Plant is a lime processing plant with five rotary lime kilns located in rural Millard County, Utah. The facility has a combined Q/d value of 9; the nearest Class I area is Capitol Reef National Park at 130.8 kilometers away. Existing controls at the Cricket Mountain Plant are low-NO
X
burners and baghouses at each kiln.

Given Cricket Mountain's low SO
2
emissions, Utah did not require Graymont to conduct a four-factor analysis for SO
2
controls. The facility's SO
2
Q/d values at Capitol Reef National Park and SO
2
emissions data are shown in table 4.

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Graymont identified several potential NO
X
control technologies for the Cricket Mountain Plant. It conducted a four-factor analysis for SNCR, although it considered that technology to be infeasible at the facility. Utah requested that Graymont also consider two additional control options: fuel switching (use of alternative fuels instead of coal) and alternative production techniques (use of vertical lime kilns instead of long horizontal kilns). The results of Graymont's analysis are shown in table 5.

EP19AU24.006

Utah identified several errors with Graymont's analysis and requested that it further evaluate SNCR. Graymont submitted additional analyses to support its contention that SNCR is not cost-effective or technically feasible due to potential proprietary costs and associated cost per ton.
69

Graymont also found that fuel switching to natural gas would not be feasible, as natural gas with the Btu values required for lime production is not currently available to the facility and would require construction of extensive infrastructure and process modifications to connect to the nearest natural gas pipeline. Finally, Graymont found replacement of its existing kilns with vertical lime kilns to be infeasible because it would require demolition of the existing kilns and plant infrastructure and construction of a new plant.

69
Utah regional haze SIP submission at 137-48 and appendix C.2.C.

Utah ultimately concluded that additional controls are not required for reasonable progress at the Cricket Mountain Plant based on their cost/ton and the potential proprietary costs of SNCR technology for the kilns. The State determined that the facility's existing control measures and emissions limits are necessary for reasonable progress during the second implementation period.
70

70
Utah regional haze SIP submission at 179.

iii. PacifiCorp Hunter and PacifiCorp Huntington
71

71
The four-factor analyses for these facilities are contained in the Utah regional haze SIP submission at 138-164, 179, and appendices C.3.A, C.3.C, and C.3.D.

Utah selected two electric generating units (EGUs) operated by PacifiCorp for four-factor analysis: PacifiCorp Hunter and PacifiCorp Huntington. Hunter is a 1,455 megawatt (MW) coal-fired steam EGU consisting of three units. It is located near Castle Dale in Emery County, Utah. Hunter has a combined Q/d value of 216.1, and the nearest Class I area is Capitol Reef National Park at 74.9 kilometers away. Huntington is a 960 MW coal-fired steam EGU consisting of two units. It is located in

Huntington, Utah. Huntington has a combined Q/d value of 105.5, and the nearest Class I area is Capitol Reef National Park at 95.8 kilometers away. Although Hunter and Huntington are entirely separate facilities, Utah's regional haze SIP submission and PacifiCorp's supporting documentation analyzed Hunter and Huntington alongside each other. Therefore, we address these two facilities together in this document.

Both Hunter and Huntington operate existing emissions controls, although neither have post-combustion NO
X
controls. Hunter Units 1 and 2 are equipped with LNB/separated overfire air (SOFA) for NO
X
control, baghouses for PM control, and wet flue-gas desulfurization (FGD) scrubbers for SO
2
control. Hunter Unit 3 has LNB/SOFA for NO
X
control, baghouse for PM control, and FGD scrubber for SO
2
control. Huntington Units 1 and 2 have LNB/SOFA for NO
X
control, fabric filter baghouses for PM control, and FGD scrubbers for SO
2
control.

In its four-factor analyses for NO
X
controls
72

at the two facilities, PacifiCorp evaluated three options: SCR, SNCR, and “Reasonable Progress Emission Limits” (RPELs). PacifiCorp's proposed RPELs were plantwide (
i.e.,
not unit-specific) combined (NO
X
+SO
2
) annual emission limits that PacifiCorp proposed to replace the facilities' permitted existing plantwide applicability limits (PALs), which feature separate PALs for NO
X
and SO
2
. PacifiCorp proposed an RPEL of 17,773 tpy for Hunter and an RPEL of 10,491 tpy for Huntington. It asserted that these RPELs would reduce emissions compared to the plants' most restrictive existing permits.

72
Aside from the RPELs, PacifiCorp did not evaluate any additional SO
2
controls on the basis that the units are already effectively controlled. Utah ultimately agreed with that conclusion.

Based on its calculated cost/ton values for all three control options, PacifiCorp argued that SCR and SNCR at Hunter and Huntington were not cost-effective. It urged Utah to select the RPELs for inclusion in the State's long-term strategy based on a balance of the four statutory factors.

Utah identified several deficiencies in PacifiCorp's cost calculations and requested that PacifiCorp “expand its analysis of mitigating factors, excessive capital costs, alternative solutions, and other costs in order to justify the removal of either SNCR and/or SCR as viable control options.”
73

Utah also determined that PacifiCorp's proposed RPELs were “lacking” because they would not achieve any actual reductions in emissions given that the facilities have consistently operated well below their permitted PALs.
74

Following PacifiCorp's submission of additional information, Utah rejected the proposed RPELs, concluding they could not be effectively compared against the cost/ton values for physical controls (SNCR and SCR).

73
Utah regional haze SIP submission, appendix C.3.B. at 8.

74

Id.
at 9.

PacifiCorp provided updated cost/ton values for SCR and SNCR at Hunter and Huntington, which Utah accepted. Depending on the unit, those values ranged from $5,417/ton to $6,579/ton for SNCR and $4,401/ton to $6,533/ton for SCR,
75

as shown in tables 6 and 7. PacifiCorp's cost/ton calculations were based on the plants' average utilization levels (in the form of the units' heat input, expressed as million British thermal units (MMBtu)/year) during the 2015-2019 period.
76

To determine cost/ton values for SNCR and SCR, PacifiCorp first multiplied heat inputs for each unit by an emission rate (which varied based on the SCR, SNCR, and “no additional controls” scenarios) to calculate each unit's emission levels under the three control scenarios. Each control scenario yielded a different level of NO
X
emissions. The total annual cost of each control was then divided by its associated emission reductions (in tons/year) to arrive at a cost-effectiveness metric of dollars per ton of NO
X
emissions reduced for each unit at the plants. Tables 6 and 7 also show the NO
X
emissions reductions that SNCR and SCR post-combustion controls would achieve relative to the plants' average actual emissions during the 2015-2019 period.
77

75
Utah regional haze SIP submission at 147; appendix C.3.C., attachment B.

76
Utah regional haze SIP submission at 147.

77
To calculate the NO
X
emissions reductions, we consulted appendix C.3.C. of Utah's regional haze SIP submission. We determined the tons of NO
X
removed shown in tables 6 and 7 by subtracting each unit's NO
X
emissions (in tons per year) listed in the “SNCR Emissions” and “SCR Emissions” tables in Attachment B in appendix C.3.C. from the corresponding units' NO
X
emissions (in tons per year) listed in the “SNCR and SCR Baseline Emissions” table in Attachment B.

EP19AU24.007

EP19AU24.008

Although it accepted PacifiCorp's updated cost/ton calculations, Utah did not proceed to evaluate SCR and SNCR with reference to those costs of compliance and the other three statutory factors. Rather, Utah elected to further analyze the cost/ton values by predicting how changes in future plant utilization at Hunter and Huntington might affect the cost-effectiveness of SCR.
78

Utah developed a sensitivity analysis to assess cost/ton values under three alternative plant utilization scenarios relative to utilization during the baseline period of 2015-2019: 50%, 75%, and 125% of baseline utilization. The cost/ton values were calculated by scaling 2015-2019 average heat input by those percentages. Utah's analysis showed that, all else equal, higher plant utilization produced lower cost/ton values (meaning that SCR was relatively more cost-effective), while lower utilization produced higher cost/ton values (meaning that SCR was relatively less cost-effective).

78
Utah focused its analysis on SCR and did not analyze SNCR in detail. SCR would achieve greater emissions reductions at a lower cost/ton value compared to SNCR.

Utah observed that its sensitivity analysis “raises the question of how the units at both plants are likely to be utilized throughout the second regional haze planning period.”
79

To try to address that question, Utah consulted WRAP's projections of 2028 emissions for Hunter and Huntington that were developed through the WRAP planning process.
80

WRAP's projections of the plants' 2028 emissions were very similar to the 2015-2019 average actual emissions that PacifiCorp used in its cost/ton calculations.
81

WRAP's projections were based on 2016-2018 plant utilization levels.

79
Utah regional haze SIP submission at 149.

80

Id.
at 149-50. WRAP relied on the Center for the New Energy Economy (CNEE) at Colorado State University to project 2028 emissions for coal- and gas-fired EGUs in Western states. Projections for coal-fired EGUs such as Hunter and Huntington were based on 2016-2018 plant utilization (in the form of gross load), heat rates, and emission rates; they also incorporated “on-the-books” controls such as the installation of emissions controls or plant closures. CNEE's analysis is contained in the docket for this action. CNEE, “Project Report for WESTAR-WRAP: Analysis of EGU Emissions for Regional Haze Planning and Ozone Transport Contribution” (June 14, 2019).

81
Using the methodology developed by CNEE, WRAP projected 2028 NO
X
emissions for Hunter (10,001 tpy) and Huntington (6,091 tpy). Utah explained that these emission projections are “similar though not identical to PacifiCorp's recent actual emissions used in its four-factor analyses, with the differences stemming from the use of different averaging periods and methodologies.” Utah regional haze SIP submission at 150.

After considering WRAP's 2028 emissions projections, Utah asserted that the electrical generating sector “is experiencing significant change” due to increases in natural gas and renewable energy generation, enhanced grid coordination, greater transmission capacity and planning efforts, improvements in equipment efficiency, uncertainty regarding climate regulation, and customer preferences for renewable energy.
82

The State turned to PacifiCorp's 2021 Integrated Resource Plan (IRP)
83

to assess potential future operations at Hunter and Huntington. The IRP contains PacifiCorp's assessment of the “least-cost, least-risk portfolio” of resources while accounting for compliance with regulatory requirements and customer demand for clean energy. PacifiCorp completes the full IRP planning process every two years and reviews and updates it in the in-between years. While the IRP does not project future utilization at Hunter and Huntington (which PacifiCorp considers confidential information), Utah cited PacifiCorp's long-term (2021-2040) plans to increase renewable energy generation and energy storage capacity, retire certain coal-fired units or convert them to natural gas, and utilize remaining coal-fired units to support growth in renewable energy generation by providing power when renewable generation is not available. Utah concluded there would be a “likely reduction in utilization of Hunter and Huntington in future years,” which would reduce the cost-effectiveness of SCR.
84

82
Utah regional haze SIP submission at 150.

83
PacifiCorp, “2021 Integrated Resource Plan” Vol. I (Sept. 1, 2021), available in the docket for this action (hereinafter “PacifiCorp 2021 IRP”).

84
Utah regional haze SIP submission at 156.

Utah also highlighted several “affordability” considerations regarding the installation of SCR at Hunter and Huntington.
85

It

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2024-18462. Public record. Not legal advice.