# Air Quality State Implementation Plans; Partial Approval, Partial Disapproval and Promulgation; Texas; Regional Haze

> Briefs, arguments, decisions, and more.

URL: https://www.frixlaw.com/law-library/documents/fr%3A2024-23341

## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** October 15, 2024
- **Citation:** 89 FR 83338

## Text

ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R06-OAR-2021-0539; FRL-12282-01-R6]
Air Quality State Implementation Plans; Partial Approval, Partial Disapproval and Promulgation; Texas; Regional Haze

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The Environmental Protection Agency (EPA) is proposing to partially approve and partially disapprove the regional haze State implementation plan (SIP) revision submitted by Texas on July 20, 2021, under the Clean Air Act (CAA) and EPA's Regional Haze Rule (RHR) for the program's second implementation period. Texas's SIP submission addresses the requirement that states must periodically revise their long-term strategies for making reasonable progress towards the national goal of preventing any future, and remedying any existing, anthropogenic impairment of visibility, including regional haze, in mandatory Class I Federal areas. The SIP submission also addresses other applicable requirements for the second implementation period of the regional haze program. The EPA is taking this action pursuant to sections 110 and 169A of the Clean Air Act.

DATES:

Written comments must be received on or before November 14, 2024.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-R06-OAR-2021-0539 at
https://www.regulations.gov.
Follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from
Regulations.gov
. The EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission (
i.e.,
on the web, cloud, or other file sharing system). For additional submission methods, the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit
https://www.epa.gov/dockets/commenting-epa-dockets.
For additional submission methods, please contact the person identified in the
FOR FURTHER INFORMATION CONTACT
section. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit
https://www.epa.gov/dockets/commenting-epa-dockets.

Docket:
The index to the docket for this action is available electronically at
www.regulations.gov.
While all documents in the docket are listed in the index, some information may not be publicly available due to docket file size restrictions or content (
e.g.,
CBI).

FOR FURTHER INFORMATION CONTACT:

Jennifer Huser, U.S. Environmental Protection Agency, Region 6, 1201 Elm St., Suite 500, Dallas, Texas 75270, at (214) 665-7347, or by email at
Huser.Jennifer@epa.gov.

SUPPLEMENTARY INFORMATION:

Throughout this document wherever “we,” “us,” or “our” is used, we mean the EPA.

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

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 Texas's Regional Haze Submission for the Second Implementation Period

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

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

C. Identification of Class I Areas

1. Texas Class I Areas

2. Identification of Impacted Class I Areas Outside the State

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

E. Long-Term Strategy for Regional Haze

1. Source Selection

2. Four Factor Analysis

3. Additional Long-Term Strategy Requirements

F. Reasonable Progress Goals

G. Reasonably Attributable Visibility Impairment (RAVI)

H. Monitoring Strategy and Other Implementation Plan Requirements

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

J. Requirements for State and Federal Land Manager Coordination

V. Proposed Action

VI. Environmental Justice Considerations

VII. Statutory and Executive Order Reviews

I. What action is the EPA proposing?

On July 20, 2021, the Texas Commission on Environmental Quality (TCEQ) submitted a plan (“2021 Texas Regional Haze Plan” or “Texas RH SIP”) to the EPA to satisfy the regional haze program requirements pursuant to CAA sections 169A and 40 CFR 51.308. The EPA is proposing to partially approve and partially disapprove Texas's Regional Haze plan for the second planning (implementation) period. Consistent with section 110(k)(3) of the CAA, the EPA may partially approve portions of a submittal if those elements meet all applicable requirements and may disapprove the remainder so long as the elements are fully separable.
1

As required by section 169A of the CAA, the Federal RHR calls for State and Federal agencies to work together to improve visibility in 156 national parks and wilderness areas. The rule requires the states, in coordination with the EPA, National Park Service (NPS), U.S. Fish and Wildlife Service (FWS), Forest Service (FS), and other interested parties, to develop and implement air quality protection plans to reduce the pollution that causes visibility impairment. Visibility impairing pollutants include fine and coarse particulate matter (PM) (
e.g.,
sulfates, nitrates, organic carbon, elemental carbon, and soil dust) and their precursors (
e.g.,
sulfur dioxide (SO
2
), nitrogen oxides (NO
X
), and, in some cases, volatile organic compounds (VOC) and ammonia (NH
3
)). As discussed in further detail below, the EPA is proposing to find that Texas has submitted a Regional Haze plan that does not meet all the Regional Haze requirements for the second planning period. For the reasons described in this document, the EPA is proposing to approve the elements of Texas's plan related to requirements contained in 40

CFR 51.308(f)(1), (f)(4), (f)(5),
2

and (f)(6). The EPA is proposing to disapprove the elements of Texas's plan related to requirements contained in 40 CFR 51.308(f)(2), (f)(3), and (i). The State's submission can be found in the docket for this action.

1

See
CAA section 110(k)(3) and July 1992 EPA memorandum titled “Processing of State Implementation Plan (SIP) Submittals” from John Calcagni, at
https://www.epa.gov/sites/default/files/2015-07/documents/procsip.pdf.

2
40 CFR 51.308(f)(5) requires that the second planning period SIP revision address the requirements listed in (g)(1) through (g)(5).

II. Background and Requirements for Regional Haze Plans

A. Regional Haze Background

In the 1977 CAA Amendments, Congress created a program for protecting visibility in the nation's mandatory Class I Federal areas, which include certain national parks and wilderness areas.
3

CAA 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 169A(a)(1). The CAA further directs the EPA to promulgate regulations to assure reasonable progress toward meeting this national goal. CAA 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 169B. The EPA promulgated the RHR, codified at 40 CFR 51.308,
4

on July 1, 1999. (64 FR 35714, July 1, 1999). These regional haze regulations are a central component of the EPA's comprehensive visibility protection program for Class I areas.

3
Areas statutorily designated as mandatory Class I Federal areas consist of national parks exceeding 6,000 acres, wilderness areas and national memorial parks exceeding 5,000 acres, and all international parks that were in existence on August 7, 1977. CAA 162(a). There are 156 mandatory Class I areas. The list of areas to which the requirements of the visibility protection program apply is in 40 CFR part 81, subpart D.

4
In addition to the generally applicable regional haze provisions at 40 CFR 51.308, the EPA also promulgated regulations specific to addressing regional haze visibility impairment in Class I areas on the Colorado Plateau at 40 CFR 51.309. The latter regulations are applicable only for specific jurisdictions' regional haze plans submitted no later than December 17, 2007, and thus are not relevant here.

Regional haze is visibility impairment that is produced by a multitude of anthropogenic sources and activities which are located across a broad geographic area and that emit pollutants that impair visibility. Visibility impairing pollutants include fine and coarse particulate matter (PM) (
e.g.,
sulfates, nitrates, organic carbon, elemental carbon, and soil dust) and their precursors (
e.g.,
sulfur dioxide (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.
5

5
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 169A(b)(2);
6

see also 40 CFR 51.308(b), (f) (establishing submission dates for iterative regional haze SIP revisions); (64 FR at 35768, July 1, 1999). Under the CAA, each SIP submission must contain “a long-term (ten to fifteen years) strategy for making reasonable progress toward meeting the national goal,” CAA 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 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 at 35768, July 1, 1999). The EPA established in the 1999 RHR that all states either have Class I areas within their borders or “contain sources whose emissions are reasonably anticipated to contribute to regional haze in a Class I area”; therefore, all states must submit regional haze SIPs.
7

Id.
at 35721.

6
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).

7
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 planning period RPGs were required to provide for an improvement in visibility for the most impaired days over the period of the implementation plan and ensure no degradation in visibility for the least impaired days over the same period. In establishing the RPGs for any Class I area in a State, the State was required to consider four statutory factors: the costs of compliance, the time necessary for compliance, the energy and non-air quality environmental impacts of compliance, and the remaining useful life of any potentially affected sources. CAA 169A(g)(1); 40 CFR 51.308(d)(1).

States were also required to calculate baseline (using the five year period of 2000-2004) and natural visibility conditions (
i.e.,
visibility conditions without anthropogenic visibility

impairment) for each Class I area, and to calculate the linear rate of progress needed to attain natural visibility conditions, assuming a starting point of baseline visibility conditions in 2004 and ending with natural conditions in 2064. This linear interpolation is known as the uniform rate of progress (URP) and is used as a tracking metric to help states assess the amount of progress they are making towards the national visibility goal over time in each Class I area.
8

40 CFR 51.308(d)(1)(i)(B), (d)(2). The 1999 RHR also provided that States' long-term strategies must include the “enforceable emissions limitations, compliance, schedules, and other measures as necessary to achieve the reasonable progress goals.” 40 CFR 51.308(d)(3). In establishing their long-term strategies, states are required to consult with other states that also contribute to visibility impairment in a given Class I area and include all measures necessary to obtain their shares of the emission reductions needed to meet the RPGs. 40 CFR 51.308(d)(3)(i), (ii). Section 51.308(d) also contains seven additional factors states must consider in formulating their long-term strategies, 40 CFR 51.308(d)(3)(v), as well as provisions governing monitoring and other implementation plan requirements. 40 CFR 51.308(d)(4). Finally, the 1999 RHR required states to submit periodic progress reports—SIP revisions due every five years that contain information on states' implementation of their regional haze plans and an assessment of whether anything additional is needed to make reasonable progress, see 40 CFR 51.308(g), (h)—and to consult with the Federal Land Manager(s)
9

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

8
The EPA established the URP framework in the 1999 RHR to provide “an equitable analytical approach” to assessing the rate of visibility improvement at Class I areas across the country. The starting point for the URP analysis is 2004 and the endpoint was calculated based on the amount of visibility improvement that was anticipated to result from implementation of existing CAA programs over the period from the mid-1990s to approximately 2005. Assuming this rate of progress would continue into the future, the EPA determined that natural visibility conditions would be reached in 60 years, or 2064 (60 years from the baseline starting point of 2004). However, the EPA did not establish 2064 as the year by which the national goal
must
be reached. 64 FR at 35731-32. That is, the URP and the 2064 date are not enforceable targets but are rather tools that “allow for analytical comparisons between the rate of progress that would be achieved by the state's chosen set of control measures and the URP.” (82 FR 3078, 3084, January 10, 2017).

9
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”).
10

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”).
11

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”),
12

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”).
13

10
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).

11
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).

12
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).

13
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.
14

14
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),
15

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.

15
RPOs are sometimes also referred to as “multi-jurisdictional organizations,” or MJOs. For the purposes of this notice, the terms RPO and MJO are synonymous.

The Central Regional Air Planning Association (CenRAP), one of the five RPOs described above, that Texas was a member of during the first planning period, was a collaborative effort of State governments, Tribal governments, and Federal agencies established to initiate and coordinate activities associated with the management of regional haze, visibility, and other air quality issues in parts of the Great Plains, Midwest, Southwest, and South Regions of the United States.

After the first planning period SIPs were submitted, the planning was shifted to the Central State Air Resources Agencies (CenSARA). CenSARA was established to promote the exchange of air quality information, knowledge, experience, and data among and between participating organizations and other interested parties. It supports the membership with training and policy and technical projects. CenSARA supports and promotes collaborative efforts of State governments to initiate and coordinate activities associated with the management of regional haze and other air quality issues in parts of the Great Plains, Midwest, Southwest, and South Regions of the United States. Member states include: Arkansas, Iowa, Kansas, Louisiana, Missouri, Nebraska, Oklahoma, and Texas. Unlike CenRAP, CenSARA has solely State and local government members. However, CenSARA does reach out to Tribal and Federal partners. The Federal partners of CenSARA are the EPA, the NPS, the FWS, and FS.

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

Under the CAA and EPA's regulations, all 50 States, the District of Columbia, and the U.S. Virgin Islands are required to submit regional haze SIPs satisfying the applicable requirements for the second implementation period of the regional haze program by July 31, 2021. Each state's SIP must contain a long-term strategy for making reasonable progress toward meeting the national goal of remedying any existing and preventing any future anthropogenic visibility impairment in Class I areas. CAA 169A(b)(2)(B). To this end, § 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 (f)(3) generally mirroring the order of the steps in the reasonable progress analysis
16

and (f)(4) through (f)(6) containing additional, related requirements. Broadly speaking, a State first must identify the Class I areas within the State and determine the Class I areas outside the State in which visibility may be affected by emissions from the State. These are the Class I areas that must be addressed in the state's long-term strategy. See 40 CFR 51.308(f), (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”
17

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)-(3).

16
The EPA explained in the 2017 RHR Revisions that we were adopting new regulatory language in 40 CFR 51.308(f) that, unlike the structure in 51.308(d), “tracked the actual planning sequence.” (82 FR 3091, January 10, 2017).

17
The five “additional factors” for consideration in section 51.308(f)(2)(iv) are distinct from the four factors listed in CAA section 169A(g)(1) and 40 CFR 51.308(f)(2)(i) that states must consider and apply to sources in determining reasonable progress.

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 EPA's regulations. See CAA 169A(b)(2); CAA 110(a). Upon EPA approval, a SIP is enforceable by the Agency and the public under the CAA.

If EPA finds that a State fails to make a required SIP revision, or if the EPA finds that a state's SIP is incomplete or disapproves the SIP, the Agency must promulgate a federal implementation plan (FIP) that satisfies the applicable requirements. CAA 110(c)(1).

A. Identification of Class I Areas

The first step in developing a regional haze SIP is for a State to determine which Class I areas, in addition to those within its borders, “may be affected” by emissions from within the State. In the 1999 RHR, the EPA determined that all states contribute to visibility impairment in at least one Class I area, 64 FR at 35720-22, and explained that the statute and regulations lay out an “extremely low triggering threshold” for determining “whether States should be required to engage in air quality planning and analysis as a prerequisite to determining the need for control of emissions from sources within their State.”
Id.
at 35721.

A State must determine which Class I areas must be addressed by its SIP by evaluating the total emissions of visibility impairing pollutants from all sources within the State. While the RHR does not require this evaluation to be conducted in any particular manner, EPA's 2019 Guidance provides recommendations for how such an assessment might be accomplished, including by, where appropriate, using the determinations previously made for the first implementation period. 2019 Guidance at 8-9. In addition, the determination of which Class I areas may be affected by a state's emissions is subject to the requirement in 40 CFR 51.308(f)(2)(iii) to “document the technical basis, including modeling, monitoring, cost, engineering, and emissions information, on which the State is relying to determine the emission reduction measures that are necessary to make reasonable progress in each mandatory Class I Federal area it affects.”

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

As part of assessing whether a SIP submission for the second implementation period is providing for reasonable progress towards the national visibility goal, the RHR contains requirements in § 51.308(f)(1) related to tracking visibility improvement over time. The requirements of this subsection apply only to states having Class I areas within their borders; the required calculations must be made for each such Class I area. EPA's 2018 Visibility Tracking Guidance
18

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 at 3103-05.

18
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://www3.epa.gov/ttnamti1/files/ambient/visible/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).
19

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,
20

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.

19
This notice also refers to the 20% clearest and 20% most anthropogenically impaired days as the “clearest” and “most impaired” or “most anthropogenically impaired” days, respectively.

20
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.
21

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.

21
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 at 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 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 EPA previously explained, consistent with the first implementation period, 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.

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.
22

22
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.
23

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 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 at 3091. Thus, for each source it has selected for four-factor analysis,
24

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.

23
The CAA provides that, “[i]n determining reasonable progress there shall be taken into consideration” the four statutory factors. CAA 169A(g)(1). However, in addition to four-factor analyses for selected sources, groups of sources, or source categories, a state may also consider additional emission reduction measures for inclusion in its long-term strategy,
e.g.,
from other newly adopted, on-the-books, or on-the-way rules and measures for sources not selected for four-factor analysis for the second planning period.

24
“Each source” or “particular source” is used here as shorthand. While a source-specific analysis is one way of applying the four factors, neither the statute nor the RHR requires states to evaluate individual sources. Rather, states have “the flexibility to conduct four-factor analyses for specific sources, groups of sources or even entire source categories, depending on state policy preferences and the specific circumstances of each state.” 82 FR at 3088. However, not all approaches to grouping sources for four-factor analysis are necessarily reasonable; the reasonableness of grouping sources in any particular instance will depend on the circumstances and the manner in which grouping is conducted. If it is feasible to establish and enforce different requirements for sources or subgroups of sources, and if relevant factors can be quantified for those sources or subgroups, then states should make a separate reasonable progress determination for each source or subgroup. 2021 Clarifications Memo at 7-8.

EPA's 2021 Clarifications Memo provides further guidance on what constitutes a reasonable set of control options for consideration: “A reasonable four-factor analysis will consider the full range of potentially reasonable options for reducing emissions.” 2021 Clarifications Memo at 7. In addition to add-on controls and other retrofits (
i.e.,
new emissions reduction measures for sources), EPA explained that states should generally analyze efficiency improvements for sources' existing measures as control options in their four-factor analyses, as in many cases 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.
25

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.”

25
See,
e.g.,
Responses to Comments on Protection of Visibility: Amendments to Requirements for State Plans; Proposed Rule (81 FR 26942, May 4, 2016) (December 2016), Docket Number EPA-HQ-OAR-2015-0531, U.S. Environmental Protection Agency at 186; 2019 Guidance at 36-37.

As explained above, § 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.
26

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 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.

26
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 at 3108-09 (requirement to consider smoke management practices and smoke management programs under 40 CFR 51.308(f)(2)(iv) does not require states to adopt such practices or programs into their SIPs, although they may elect to do so).

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.
27

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.

27
See
Arizona ex rel. Darwin
v.
U.S. EPA
, 815 F.3d 519, 531 (9th Cir. 2016);
Nebraska
v.
U.S. EPA
, 812 F.3d 662, 668 (8th Cir. 2016);
North Dakota
v.
EPA
, 730 F.3d 750, 761 (8th Cir. 2013);
Oklahoma
v.
EPA
, 723 F.3d 1201, 1206, 1208-10 (10th Cir. 2013); cf. also
Nat'l Parks Conservation Ass'n
v.
EPA
, 803 F.3d 151, 165 (3d Cir. 2015);
Alaska Dep't of Envtl. Conservation
v.
EPA,
540 U.S. 461, 485, 490 (2004).

The four statutory factors (and potentially visibility) are used to determine what emission reduction measures for selected sources must be included in a state's long-term strategy

for making reasonable progress. Additionally, the RHR at 40 CFR 51.3108(f)(2)(iv) separately provides five “additional factors”
28

that states must consider in developing their long-term strategies: (1) Emission reductions due to ongoing air pollution control programs, including measures to address reasonably attributable visibility impairment; (2) measures to reduce the impacts of construction activities; (3) source retirement and replacement schedules; (4) basic smoke management practices for prescribed fire used for agricultural and wildland vegetation management purposes and smoke management programs; and (5) the anticipated net effect on visibility due to projected changes in point, area, and mobile source emissions over the period addressed by the long-term strategy. The 2019 Guidance provides that a State may satisfy this requirement by considering these additional factors in the process of selecting sources for four-factor analysis, when performing that analysis, or both, and that not every one of the additional factors needs to be considered at the same stage of the process. See 2019 Guidance at 21. The EPA provided further guidance on the five additional factors in the 2021 Clarifications Memo, explaining that a State should generally not reject cost-effective and otherwise reasonable controls merely because there have been emission reductions since the first planning period owing to other ongoing air pollution control programs or merely because visibility is otherwise projected to improve at Class I areas. Additionally, states generally should not rely on these additional factors to summarily assert that the State has already made sufficient progress and, therefore, no sources need to be selected or no new controls are needed regardless of the outcome of four-factor analyses. 2021 Clarifications Memo at 13.

28
The five “additional factors” for consideration in section 51.308(f)(2)(iv) are distinct from the four factors listed in CAA section 169A(g)(1) and 40 CFR 51.308(f)(2)(i) that states must consider and apply to sources in determining reasonable progress.

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 at 3091. Their primary purpose is to assist the public and the EPA in assessing the reasonableness of states' long-term strategies for making reasonable progress towards the national visibility goal. See 40 CFR 51.308(f)(3)(iii)-(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.
29

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.

29
RPGs are intended to reflect the projected impacts of the measures all contributing states include in their long-term strategies. However, due to the timing of analyses and of control determinations by other states, other on-going emissions changes, a particular state's RPGs may not reflect all control measures and emissions reductions that are expected to occur by the end of the implementation period. The 2019 Guidance provides recommendations for addressing the timing of RPG calculations when states are developing their long-term strategies on disparate schedules, as well as for adjusting RPGs using a post-modeling approach. 2019 Guidance at 47-48.

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 shows no degradation on the clearest days compared to the clearest days from the baseline period. The baseline period for the purpose of this comparison is the baseline visibility condition—the annual average visibility condition for the period 2000-2004. See 40 CFR 51.308(f)(1)(i), 82 FR at 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 at 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 subsection apply either to states with Class I areas within their borders, states with no Class I areas but that are reasonably anticipated to cause or contribute to visibility impairment in any Class I area, or both. A State with Class I areas within its borders must submit with its SIP revision a monitoring strategy for measuring, characterizing, and reporting regional haze visibility impairment that is representative of all Class I areas within the State. SIP revisions for such states must also provide for the establishment of any additional monitoring sites or equipment needed to assess visibility conditions in Class I areas, as well as reporting of all visibility monitoring data to the EPA at least annually. Compliance with the monitoring strategy requirement may be met through a state's participation in the Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring network, which is used to measure visibility impairment caused by air pollution at the 156 Class I areas covered by the visibility program. 40 CFR 51.308(f)(6), (f)(6)(i), (f)(6)(iv). The IMPROVE monitoring data is used to determine the 20% most anthropogenically impaired and 20% clearest sets of days every year at each Class I area and tracks visibility impairment over time.

All states' SIPs must provide for procedures by which monitoring data and other information are used to determine the contribution of emissions from within the State to regional haze visibility impairment in affected Class I areas. 40 CFR 51.308(f)(6)(ii), (iii). Section 51.308(f)(6)(v) further requires that all states' SIPs provide for a statewide inventory of emissions of pollutants that are reasonably anticipated to cause or contribute to visibility impairment in any Class I area; the inventory must include emissions for the most recent year for which data are available and estimates of future projected emissions. States must also include commitments to update their inventories periodically. The inventories themselves do not need to be included as elements in the SIP and are not subject to EPA review as part of the Agency's evaluation of a SIP revision.
30

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.
31

30
See “Step 8: Additional requirements for regional haze SIPs” in 2019 Guidance at 55.

31

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.”
32

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.

32
The EPA's visibility protection regulations define “reasonably attributable visibility impairment” as “visibility impairment that is caused by the emission of air pollutants from one, or a small number of sources.” 40 CFR 51.301.

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

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

A core component of the progress report requirements is an assessment of changes in visibility conditions on the clearest and most impaired days. For second implementation period progress reports, § 51.308(g)(3) requires states with Class I areas within their borders to first determine current visibility conditions for each area on the most impaired and clearest days, 40 CFR 51.308(g)(3)(i)(B), and then to calculate the difference between those current conditions and baseline (2000-2004) visibility conditions to assess progress made to date. See 40 CFR 51.308(g)(3)(ii)(B). States must also assess the changes in visibility impairment for the most impaired and clearest days since they submitted their first implementation period progress reports. See 40 CFR 51.308(g)(3)(iii)(B), (f)(5). Since different states submitted their first implementation period progress reports at different times, the starting point for this assessment will vary State by State.

Similarly, states must provide analyses tracking the change in emissions of pollutants contributing to visibility impairment from all sources and activities within the State over the period since they submitted their first implementation period progress reports. See 40 CFR 51.308(g)(4), (f)(5). Changes in emissions should be identified by the type of source or activity. Section 51.308(g)(5) also addresses changes in emissions since the period addressed by the previous progress report and requires states' SIP revisions to include an assessment of any significant changes in anthropogenic emissions within or outside the State. This assessment must explain whether these changes in emissions were anticipated and whether they have limited or impeded progress in reducing emissions and improving visibility relative to what the State projected based on its long-term strategy for the first implementation period.

G. Requirements for State and Federal Land Manager Coordination

Clean Air Act 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 Texas's Regional Haze Submission for the Second Implementation Period

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

Texas submitted its regional haze SIP for the first implementation period to the EPA on March 31, 2009. The EPA issued a limited disapproval of Texas's RH SIP on June 7, 2012, due to its reliance on the Clean Air Interstate Rule (CAIR) to address BART requirements for Texas electric generating units (EGUs).
33

The EPA proposed a rule to partially approve and partially disapprove Texas's SIP on December 16, 2014;
34

however, due to a related ruling from the United States Court of Appeals for the District of Columbia Circuit (D.C. Circuit),
35

the EPA could not finalize the December 2014 proposal in its entirety. As such, the EPA's obligations for the first implementation period for Texas's regional haze SIP were addressed in two separate actions. One action, finalized on January 5, 2016, addressed the regional haze requirements in Texas except for BART requirements for EGUs.
36

The second action, finalized on October 17, 2017, and affirmed on August 12, 2020, addressed BART requirements for Texas EGUs.
37

The EPA has convened separate reconsideration proceedings for both actions.
38

While these proceedings remain ongoing, they do not interfere with the EPA's statutory obligation to take action on Texas's SIP revision for the second implementation period.
39

33
77 FR 33642 (June 7, 2012).

34
79 FR 74818 (Dec. 16, 2014).

35

EME Homer City Generation, L.P
v.
EPA,
795 F.3d 118 (D.C. Cir. 2015).

36
81 FR 296 (Jan. 5, 2016). In July 2016, the 5th Circuit Court of Appeals issued a stay of the action.
Texas
v.
EPA,
829 F.3d 405 (5th Cir. 2016). Subsequent to the stay opinion, the EPA requested and the court granted EPA's motion for a partial voluntary remand.

37

See
82 FR 48324 (Oct. 17, 2017); 85 FR 49170 (Aug. 12, 2020).

38

See
88 FR 28918 (May 4, 2023); 88 FR 48152 (July 26, 2023).

39
EPA is not precluded from acting on a submitted second planning period SIP revision because reconsideration proceedings on first planning period actions remains ongoing. All states had an obligation to submit second planning period SIP revisions by July 31, 2021, regardless of the status of first planning period obligations. After a second planning period SIP revision is submitted to EPA for review, EPA is statutorily required to review and act on that plan within 12 months of the submittal being deemed complete.
See
CAA 110(k)(1); 42 U.S.C. 7410(k)(1). Even with ongoing work on the second planning period, EPA will continue to work to address first planning period obligations.

The requirements for regional haze SIPs for the first implementation period are contained in 40 CFR 51.308(d) and (e). Pursuant to 40 CFR 51.308(g), Texas was also responsible for submitting a five-year progress report as a SIP revision for the first implementation period, which it did in 2014.
40

40
The EPA has not yet taken action on the progress report SIP.

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

In accordance with CAA sections 169A and the RHR at 40 CFR 51.308(f) and (i), on July 20, 2021, Texas submitted a SIP revision to address its regional haze obligations for the second implementation period, which runs through 2028. Texas made its 2021 Regional Haze SIP submission available for public comment on October 9, 2020. Texas received and responded to public comments and included the comments and responses to those comments in their submission.

The following sections describe Texas's RH SIP submission, Texas's assessment of progress made since the first implementation period in reducing emissions of visibility impairing pollutants, and the visibility improvement progress at its Class I areas

and nearby Class I areas. This notice also contains EPA's evaluation of Texas's submission against the requirements of the CAA and RHR for the second implementation period of the regional haze program.

C. Identification of Class I Areas

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

The EPA explained in the 1999 RHR preamble that the CAA section 169A(b)(2) requirement that states submit SIPs to address visibility impairment establishes “an `extremely low triggering threshold' in determining which States should submit SIPs for regional haze.”
41

In concluding that each of the contiguous 48 States and the District of Columbia meet this threshold,
42

the EPA relied on “a large body of evidence demonstrat[ing] that long-range transport of fine PM contributes to regional haze,”
43

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.”
44

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.”
45

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.”
46

The EPA's 2017 revisions to the RHR did not disturb this conclusion.
47

41
64 FR at 35721.

42
The EPA determined that “there is more than sufficient evidence to support our conclusion that emissions from each of the 48 contiguous States may reasonably be anticipated to cause or contribute to visibility impairment in a Class I area.” 64 FR at 35721. Hawaii, Alaska, and the U.S. Virgin Islands must also submit regional haze SIPs because they contain Class I areas.

43

Id.

44

Id.
at 35722.

45

Id.
at 35721.

46

Id.
at 35722.

47

See
82 FR at 3094.

1. Texas Class I Areas

Texas has two mandatory Class I areas within its borders, both of which are located in west Texas. Big Bend National Park (Big Bend) is in Brewster County and borders the Rio Grande and Mexico. Guadalupe Mountains National Park (Guadalupe Mountains) is in Culberson County and borders New Mexico. Both are managed by the National Park Service.

Big Bend was authorized as a national park on June 20, 1935, and established and signed into law on June 12, 1944, as the nation's 27th national park. Big Bend encompasses an area of 801,163 acres, entirely within Brewster County, Texas. For more than 1,000 miles, the Rio Grande forms the boundary between Mexico and the U.S., with Big Bend administering approximately 118 miles along the international boundary. The park gets its name from the course of the Rio Grande, which makes a great bend from a southeasterly to northerly direction in the western portion of Texas. Big Bend has national significance as the largest protected area of Chihuahuan Desert in the continental U.S. The park contains river, desert, and mountain environments.

Guadalupe Mountains was established as a national park on September 30, 1972, and contains Guadalupe Peak, the highest point in Texas at 8,749 feet, and El Capitan, a 1,000 foot-high limestone cliff. Guadalupe Mountains are also part of a mostly buried 400-mile long U-shaped fossil reef complex, Capitan Reef. The park covers more than 86,000 acres and is in the same mountain range of Carlsbad Caverns National Park, which is located about 40 miles to the northeast in New Mexico. Guadalupe Mountains is also located in the Chihuahuan Desert. The park is surrounded by the South Plains to the east and north, Delaware Mountains to the south, and Sacramento Mountains to the west.

2. Identification of Impacted Class I Areas Outside the State

In addition to the two Class I areas in Texas, the TCEQ conducted area of influence analyses (AOIs) paired with emissions-over-distance (Q/d) analyses for 11 Class I areas in other states including Louisiana, Arkansas, Colorado, Missouri, Oklahoma, and New Mexico. The AOIs were generated using ammonium sulfate and ammonium nitrate extinction-weighted residence times (EWRT).
48

The Class I areas included in the analysis from Texas and neighboring states are presented in table 1, which is taken from table 7-3:
Class I Areas included in AOI Analyses
of the 2021 Texas Regional Haze Plan.
49

48
2021 Texas Regional Haze Plan at 7-6. Extinction-weighted residence time is calculated from the time that a particular back-trajectory from a Class I area spent in the grid square containing the individual emission source of interest (residence time) weighted by the extinction coefficient for the visibility precursor (sulfate and nitrate).

49
For the purposes of the AOI analysis, Carlsbad Caverns was represented by data from the Guadalupe Mountains National Park monitor.
See
2021 Texas Regional Haze Plan at 1-5.

Table 1—Class I Areas Included in AOI Analyses of the 2021 Texas Regional Haze Plan

Site
Code
State
County
Latitude
Longitude

Big Bend National Park
BIBE1
TX
48043
29.3027
−103.178

Breton Island
BRIS1
LA
22075
30.10863
−89.76168

Caney Creek
CACR1
AR
05113
34.4544
−94.1429

Great Sand Dunes
GRSA1
CO
08003
37.7249
−105.5185

Guadalupe Mountains National Park
GUMO
TX
48109
31.833
−104.8094

Hercules-Glades
HEG1
MO
29213
36.6138
−92.9221

Mingo
MING1
MO
29207
36.9717
−90.1432

Rocky Mountain National Park
ROMO1
CO
08069
40.2783
−105.5457

Salt Creek
SACR1
NM
35005
33.4598
−104.4042

Upper Buffalo Wilderness
UPBO1
AR
05101
35.8258
−93.203

Wheeler Peak
WHPE1
NM
35055
36.5854
−105.42

White Mountain
WHIT1
NM
35027
33.4687
−105.5349

Wichita Mountains
WIMO1
OK
40031
34.7323
−98.713

As explained above, the EPA concluded in the 1999 RHR that “all [s]tates contain sources whose emissions are reasonably anticipated to contribute to regional haze in a Class I area,” and this determination was not changed in the 2017 RHR.
50

Critically, the statute and regulation both require that the cause-or-contribute assessment consider all emissions of visibility impairing pollutants from a State, as opposed to emissions of a particular pollutant or emissions from a certain set of sources. Consistent with these requirements, the 2019 Guidance makes it clear that “all types of anthropogenic sources are to be included in the determination” of whether a state's emissions are reasonably anticipated to result in any visibility impairment.
51

50
64 FR at 35721.

51
2019 Guidance at 8.

While Texas identified Class I areas within and outside of the State that are potentially impacted by Texas sources, Texas did not conduct an AOI analysis for the Bosque del Apache Class I area.
52

Texas justifies this decision based on “past SIP and FIP documentation” but provides no additional context or explanation of why that decision remains appropriate for this planning period.
53

In contrast, Texas's CAMx PSAT
54

modeling identified Bosque del Apache as having impacts from Texas sources. According to Texas's PSAT modeling, Texas sources contribute over seven percent of the total visibility impairment at Bosque del Apache.
55

Specifically, the 2021 Texas Regional Haze Plan identifies that the influence due to particulate sulfate from Texas sources is more than five times the influence of New Mexico sources, and the influence due to particulate nitrate from Texas sources is nearly twice the influence of New Mexico sources.
56

Thus, Texas's PSAT modeling suggests that emissions from Texas sources are reasonably anticipated to contribute to visibility impairment at the Bosque del Apache Class I area given the low threshold for visibility impact on Class I areas discussed previously.
57

Therefore, Texas did not complete its obligation under 40 CFR 51.308(f), which provides that each state's plan “must address regional haze in each mandatory Class I Federal area located within the State and in each mandatory Class I Federal area located outside the State that may be affected by emissions from within the State,” and (f)(2), which requires each state's plan to include a long-term strategy that addresses regional haze in such Class I areas.

52
Texas also did not conduct an AOI analysis for the Bandelier Class I area for the same reasons provided for Bosque del Apache.

53
2021 Texas Regional Haze Plan, appendix A at 19 of 227; 2021 Texas Regional Haze Plan, Response to Comments at 460 of 653.

54
Comprehensive Air quality Model with extensions (CAMx) Particulate Source Apportionment Technique (PSAT). CAMx PSAT is capable of tracking source category emissions and separate source regions for certain PM species and precursor emissions. We discuss this further in the Technical Support Document (TSD) for this action, included in the docket.

55
2021 Texas Regional Haze Plan, appendix A at 26 of 227.

56

See
2021 Texas Regional Haze Plan, table 8-41 at 8-53; and 2021 Texas Regional Haze Plan, appendix F at F-59 to F-61.

57
2021 Texas Regional Haze Plan, appendix F at F-36.

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

Section 51.308(f)(1) requires states to determine the following for “each mandatory Class I Federal area located within the State”: baseline visibility conditions for the most impaired and clearest days, natural visibility conditions for the most impaired and clearest days, progress to date for the most impaired and clearest days, the differences between current visibility conditions and natural visibility conditions, and the URP. This section also provides the option for states to propose adjustments to the URP line for a Class I area to account for visibility impacts from anthropogenic sources outside the United States and/or the impacts from wildland prescribed fires that were conducted for certain, specified objectives.
58

58
40 CFR 51.308(f)(1)(vi)(B).

In Chapter 4 of the 2021 Texas Regional Haze Plan, Texas determines and presents the baseline, natural, and current visibility conditions for both the 20 percent most anthropogenically impaired days and the 20 percent clearest days for the State's two Class I Areas consistent with the EPA's RHR and guidance. In the 2021 Texas Regional Haze Plan, the TCEQ used visibility data from IMPROVE monitoring sites to calculate baseline visibility conditions. Consistent with the RHR, Texas calculated baseline visibility based on data from 2000-2004. For Big Bend specifically, baseline visibility conditions are based on valid data for 2001 through 2004 because 2000 did not meet completeness criteria.
59

Baseline visibility indices for Big Bend and Guadalupe Mountains are presented in the 2021 Texas Regional Haze Plan in table 4-4. In our review, we identified that the information provided by Texas in Chapter 4 of its 2021 Regional Haze Plan as to the baseline and current conditions on the 20 percent clearest days is inconsistent with the IMPROVE monitoring data and information presented in Chapter 8. Based on the information in table 8-42 of the 2021 Regional Haze Plan, Texas identifies the correct data set for where this information is located but presents the incorrect data in Chapter 4. Based on the data source that Texas identified in Chapter 8, we present information in tables 2 and 4 consistent with information in Chapter 8 of its Plan and the IMPROVE monitoring data.
60

59

See
2021 Texas Regional Haze Plan at 4-4.

60

https://views.cira.colostate.edu/fed/. See also
2020 Data Completeness Memo, table 1.

Table 2—Estimate of Baseline Visibility Conditions (2000-2004) for Class I Areas in Texas

Class I area

Most impaired haze index
(dv)

Clearest haze index
(dv)

Big Bend
15.57
5.78

Guadalupe Mountains
14.60
5.92

Using the revised IMPROVE algorithm
61

and the methodology described in the 2018 Visibility Tracking Guidance, the TCEQ determined natural visibility conditions for Big Bend and Guadalupe Mountains, presented in table 4-3 of the 2021 Texas Regional Haze Plan, and included in the following table 3.

61
Marc Pitchford et al.,
Revised Algorithm for Estimating Light Extinction from IMPROVE Particle Speciation Data
, j. Air & waste mgmt. Ass'n 1326, 1326-1336 (2007),
https://doi.org/10.3155/1047-3289.57.11.1326.

Table 3—Estimate of Natural Visibility Conditions for Class I Areas in Texas

Class I area

Most impaired haze index
(dv)

Clearest haze index
(dv)

Big Bend
5.33
1.62

Guadalupe Mountains
4.83
0.99

The current visibility conditions, which are based on 2014-2018 monitoring data, are presented in the 2021 Texas Regional Haze Plan in table 4-5 with corrected values included in the following table 4.

Table 4—Estimate of Current Visibility Conditions (2014-2018) for Class I Areas in Texas

Class I area

Most impaired haze index
(dv)

Clearest haze index
(dv)

Big Bend
14.06
5.17

Guadalupe Mountains
12.64
4.73

While the 2021 Texas Regional Haze Plan does not specifically present the differences between current visibility conditions and natural visibility conditions as well as the progress to date, we include these calculations using the corrected information in tables 5 and 6.

Table 5—Progress to Date
(Differences Between Baseline and Current Conditions)

Class I area

Most impaired
(dv)

Clearest haze
(dv)

Big Bend
1.51
0.61

Guadalupe Mountains
1.96
1.19

Table 6—Differences Between Current and Natural Conditions

Class I area

Most impaired
(dv)

Clearest haze
(dv)

Big Bend
8.73
3.55

Guadalupe Mountains
7.81
3.74

The Regional Haze Rule allows states the option to adjust the 2064 glidepath endpoint to account for both international anthropogenic and certain prescribed fire impacts at Class I areas. In the EPA's September 2019 Availability of Modeling Data and Associated Technical Support Document for the EPA's Updated 2028 Visibility Air Quality Modeling memorandum
62

(EPA 2019 Modeling TSD), the EPA used 2028 modeling results to quantify the international and prescribed fire impacts at Class I areas on the 20% most anthropogenically impaired days. Texas used its own CAMx modeling results to adjust the URP to account for international anthropogenic emissions consistent with the approach used by the EPA in the TSD associated with the EPA's Updated 2028 Visibility Air Quality Modeling memorandum. Texas's adjusted URP for Big Bend and Guadalupe Mountains are presented in Figures 8-28 and 8-29 of its 2021 Texas

Regional Haze Plan.
63

Texas's adjusted URP in 2028 on the 20% most impaired visibility days is 14.38 deciviews for Big Bend and 12.81 for Guadalupe Mountains.
64

These values for Big Bend and Guadalupe Mountains are within the range of 2028 adjusted glidepath values provided for in the EPA 2019 Modeling TSD.
65

62
Availability of Modeling Data and Associated Technical Support Document for the EPA's Updated 2028 Visibility Air Quality Modeling.
https://www.epa.gov/visibility/technical-support-document-epas-updated-2028-regional-haze-modeling.
The EPA Office of Air Quality Planning and Standards, Research Triangle Park (Sep. 19, 2019).

63
After Texas adjusted the glidepath endpoint to account for contributions from international anthropogenic emissions, one site (Salt Creek, NM) was projected to be above the adjusted URP. The EPA 2019 Modeling TSD also had Salt Creek above the adjusted glidepath.

64
2021 Texas Regional Haze Plan, table 8-43 at 8-59 and table 8-46 at 8-67.

65
EPA 2019 Modeling TSD at 54, 56, and table 5-2 at 59.

The EPA finds that the visibility condition calculations for the two Texas Class I Areas meet the requirements of 40 CFR 51.308(f)(1). Therefore, the EPA proposes to approve the portions of the 2021 Texas Regional Haze Plan relating to 40 CFR 51.308(f)(1).

E. Long-Term Strategy for Regional Haze

Each State having a Class I area within its borders or emissions that may affect visibility in a Class I area must develop a long-term strategy for making reasonable progress towards the national visibility goal.
66

As explained in the Background section of this notice, 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.
67

Each state's long-term strategy must include the enforceable emission limitations, compliance schedules, and other measures that are necessary to make reasonable progress.
68

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 § 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.
69

66
CAA 169A(b)(2)(B).

67
40 CFR 51.308(f)(2)(i).

68
40 CFR 51.308(f)(2).

69
40 CFR 51.308(f)(2)(i), (iii).

1. Source Selection

a. Overview of Texas's Source Selection

Under 40 CFR 51.308(f)(2)(i), states must evaluate and determine the emission reduction measures that are necessary to make reasonable progress by considering the costs of compliance, the time necessary for compliance, the energy and non-air quality environmental impacts of compliance, and the remaining useful life of any potentially affected anthropogenic source of visibility impairment.
70

In doing so, states should consider evaluating major and minor stationary sources or groups of sources, mobile sources, and area sources as part of their long-term strategy for regional haze. Furthermore, the State must include in its implementation plan a description of the criteria it used to determine which sources or groups of sources it evaluated. States may rely on technical information developed by the RPOs of which they are members to select sources for four-factor analysis and to conduct that analysis, as well as to satisfy the documentation requirements under 40 CFR 51.308(f)(2). Texas, however, conducted its own analysis separate from CenSARA's analysis to select sources for further evaluation using the four statutory factors.

70

See also
CAA 169A(g)(1).

Texas focused on sources of NO
X
and SO
2
emissions in its control strategy analysis for the second planning period. Texas explained these are the main anthropogenic pollutants that affect visibility at Class I areas in Texas and Class I areas in neighboring states. Texas further stated that, “on an individual basis, point sources are the largest contributors to SO
2
and NO
X
,” and thus Texas elected to focus on point sources in this planning period.
71

71
2021 Texas Regional Haze Plan at 7-3.

Texas's source selection methodology relied on a two-step approach. As the first step for source selection, Texas developed areas of influence (AOIs) for thirteen
72

Class I areas (in Texas and nearby states) to identify areas that may contain sources of NO
X
and SO
2
that were expected to contribute to visibility impairment at these areas. The AOIs are graphical representations of the extinction weighted residence time (EWRT), which combines air flow patterns with ammonium sulfate and ammonium nitrate extinction measured at IMPROVE monitors at the Class I areas on the 20% most impaired days. The TCEQ used the AOI of a Class I area as a brightline cutoff to define the boundaries within which to further evaluate sources located within that area. As the second step, Texas then applied a Q/d threshold for NO
X
and for SO
2
of greater than or equal to five to point sources located within the geographical area of the selected AOI threshold.
73

As a result, any source within the AOI boundaries with a Q/d less than five or any source, regardless of its Q/d, that fell outside of the AOI boundaries were eliminated from further consideration.

72
As discussed previously in section IV.C., the monitor for Guadalupe Mountains also serves as the monitor for Carlsbad Caverns in New Mexico.

73
To calculate the Q/d for point sources, the TCEQ used 2028 projected emissions (Q in tons per year) and distance from the Class I area monitor to the source (d in kilometers). For non-EGUs, Texas estimated 2028 future year emissions from 2016 reported emissions from the State of Texas Air Reporting System (STARS) coupled with growth factors developed by the consulting firm, Eastern Research Group, Inc. (ERG)
See
2021 Texas Regional Haze Plan at 7-9. For EGUs, the TCEQ used data from the Eastern Regional Technical Advisory Committee (ERTAC) to estimate EGU projections for 2028.
See
2021 Texas Regional Haze Plan at 7-9.

Although Texas determined AOIs for 13 Class I areas in Texas and nearby states, Texas's 2021 Regional Haze Plan focused only on those Class I areas where sources with a Q/d greater than or equal to five fell within the AOI boundary.
74

Following this methodology, Texas selected 18 sources for further analysis for only four Class I areas: Wichita Mountains, Caney Creek, Guadalupe Mountains, and Salt Creek.
75

74

See
2021 Texas Regional Haze Plan, Figure 7-1 at 7-4 and Figure 7-2 at 7-5. Texas stated that those additional AOIs not represented in those figures in the SIP did not add additional sources for consideration. 2021 Texas Regional Haze Plan at 7-6.

75

See
Texas 2021 Regional Haze Plan at 7-5 to 7-6. Presented Class I areas are: Caney Creek, Guadalupe Mountains, Salt Creek, and Wichita Mountains for the NO
X
analysis, and Caney Creek, Guadalupe Mountains, and Wichita Mountains for the SO
2
analysis.

Table 7—Texas'
s
Source Selection for Its 2021 Regional Haze Plan
76

Company/site name
Unit(s)
Class I area(s)
Pollutant(s)

Coleto Creek Power/Coleto Creek Power Station
(1) coal boiler
Wichita Mountains

SO
2
.

Southwestern Electric Power/Welsh Power Plant
(2) coal boilers
Caney Creek & Wichita Mountains

SO
2
.

AEP/Pirkey Power Plant
(1) coal boiler
Caney Creek & Wichita Mountains

SO
2
.

NRG Energy/Limestone Electric Generating Station
(2) coal boilers
Wichita Mountains

SO
2
.

Vistra Energy/Martin Lake Electric Station
(3) coal boilers
Caney Creek & Wichita Mountains

SO
2
.

San Miguel Electric Cooperative/San Miguel Elec. Plant
(1) coal boiler
Guadalupe Mountains & Wichita Mountains

SO
2
.

Public Service Co. of Oklahoma/Oklaunion Power Station
(1) coal boiler
Wichita Mountains

SO
2
& NO
X
.

Vistra Energy/Oak Grove Steam Electric Station
(2) coal boilers
Wichita Mountains

SO
2
.

Holcim Texas LP/Midlothian Plant
(2) cement kilns
Wichita Mountains

SO
2
.

Vitro Flat Glass/Works No. 4 Wichita Falls Plant
(2) glass melting furnaces
Wichita Mountains

SO
2
& NO
X
.

Graphic Packaging International/Texarkana Mill
(4) boilers: (2) black liquor solids & NG; (1) NG & fuel oil; (1) NG, fuel oil, & other materials
Caney Creek

NO
X
.

El Paso Natural Gas Co./Keystone Compressor Station
(15) reciprocating engines
Guadalupe Mountains & Salt Creek

NO
X
.

El Paso Natural Gas Co./Cornudas Plant
(6) turbines
Guadalupe Mountains

NO
X
.

El Paso Natural Gas Co./Guadalupe Compressor Station
(1) turbine
Guadalupe Mountains

NO
X
.

GCC Permian/Odessa Cement Plant
(2) cement kilns
Guadalupe Mountains

NO
X
.

Orion Engineered Carbons/Orange Carbon Black Plant
(1) incinerator; (4) dryers; (2) tail gas and NG boilers; (1) flare
Caney Creek

SO
2
.

Oxbow Calcining/Oxbow Calcining-Port Arthur
(4) coke calcining kilns
Caney Creek

SO
2
.

Trinity Lightweight Aggregate (TRNLWS)/Streetman Plant
(1) lightweight aggregate kiln
Wichita Mountains

SO
2
.

b. EPA's Evaluation of Texas's Source Selection Methodology

76
Texas 2021 Regional Haze Plan, table 7-5.

In identifying the required emission limits, schedules of compliance, and other measures as may be necessary to make reasonable progress toward meeting the national goal, States first select sources for consideration of the four statutory factors.
77

Under the RHR, States have flexibility in conducting their source selection; however, Texas's source selection methodology was neither well-reasoned nor adequately justified.
78

Notably, Texas did not select any sources for further analysis of control measures that may be necessary for inclusion as part of the long-term strategy to make reasonable progress for Big Bend National Park and did not select any SO
2
sources for consideration for Salt Creek. Moreover, the EPA finds the source selection methodology used by Texas was not adequately or accurately described. As such, the threshold Texas applied to define its AOIs was not justified. Without the proper justification, it is unclear how, despite these deficiencies, Texas makes reasonable progress at these Class I areas.

77

See
40 CFR 51.308(f)(2); CAA 169A(g)(1).

78
2019 Guidance at 9, 13. The 2019 Guidance explains that in selecting sources, states must reasonably choose factors and apply them in a reasonable way given the statutory requirement to make reasonable progress towards national goal of preventing future and remedying existing anthropogenic visibility impairment).
See
CAA 169A(b)(2). To that end, the 2019 Guidance recommends that states provide a detailed description of how the state used technical information to select a reasonable set of sources for an analysis of control measures including the basis for the visibility impact thresholds the state used (if applicable), and any other relevant information.
See also
2021 Clarifications Memo at 3 (“States cannot reasonably determine that they are making reasonable progress if they have not adequately considered the contributors to visibility impairment. Thus, while states have discretion to reasonably select sources, this analysis 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.”).

i. The TCEQ Failed To Adequately Describe the Criteria It Used To Select Sources

Under 40 CFR 51.308(f)(2)(i), States are required to include a “description of the criteria it used to determine which sources or groups of sources it evaluated.” Based on our review of the 2021 Texas Regional Haze Plan, the methodology Texas described in its SIP to develop its AOIs is inconsistent with, and would not result in, the AOIs presented in Texas's SIP. Texas states in its SIP that the AOIs were determined by dividing the EWRT for each cell by the sum total of all the EWRTs (
i.e.,
EWRT for each cell) across the entire domain.
79

However, based on the documentation the EPA obtained during early engagement in the Fall of 2020 and comparing it to what was in its 2021 Regional Haze Plan, Texas actually divided the EWRT for each cell by the
maximum
EWRT in the domain for each respective pollutant. There was thus an inconsistency between what Texas said its methodology was, and what was in its 2021 Regional Haze Plan submission. Specifically, in the 2020 early engagement document, Texas stated, “. . . prior to plotting the AOIs, the weighted probabilities were scaled to 1 by dividing the weighted probabilities in each cell by the maximum value in

79
2021 Texas Regional Haze Plan at 7-7.

a cell in the domain.”
80

The EPA compared the plotted AOIs Texas had submitted during the 2020 early engagement period with the plotted AOIs Texas submitted with its 2021 Regional Haze Plan. These AOIs are the same, confirming that, despite what Texas stated in its 2021 Regional Haze Plan, Texas was actually following its articulated methodology in the 2020 early engagement document.

80
See “
README.AOIdevelopmentFor2021RHSIP_Response_to_EPArequest.20Nov2020update.docx
” available in the docket for this action.

This early engagement information was not included in the proposed SIP Texas published during its state-level notice-and-comment process. Thus, Texas's SIP failed to accurately or adequately describe the criteria actually used in its 2021 Regional Haze Plan submission to determine which sources, or groups of sources, it chose to evaluate for additional control measures as required by 40 CFR 51.308(f)(2)(i). Without an accurate and adequate description of Texas's source selection methodology, it is not clear from its 2021 Texas Regional Haze Plan how Texas evaluated and determined the emission reduction measures that are necessary to make reasonable progress for its second planning period long-term strategy. We discuss the AOI methodologies and these inconsistencies further in the Technical Support Document (TSD) included in the docket for this action.

ii. Texas Failed To Adequately Justify Its AOI Threshold

As noted in the previous section and more fully explained in the EPA's TSD, Texas selected sources using AOIs it developed for each Class I area then followed with a Q/d analysis. The AOIs established a brightline geographic boundary within which Texas selected sources with a Q/d of greater than or equal to five. In other words, Texas did not consider a source, regardless of the size of its emissions, if it was not first within the geographic area defined by the chosen AOI threshold.

To define the brightline geographic boundaries of the AOIs, Texas applied a threshold of 0.1 or 10% of the maximum EWRT value for that AOI.
81

Texas did not provide any discussion or justification for its selection of this threshold, nor did Texas explain how this threshold resulted in evaluating a meaningful set of sources for possible controls measures to improve visibility impairment. Further, Texas did not evaluate whether the selected threshold provided for AOIs that included a sufficiently large area to capture the sources with the highest emissions, or Q/d values, that impact visibility at certain Class I areas. The need for a justification is crucial when a State is applying the threshold as a brightline when selecting sources to evaluate for additional control measures, such as what Texas did here. The AOIs generated from EWRTs represent the general location that air parcels are coming from when visibility extinction is high. However, unless an appropriate threshold value is applied, they do not necessarily capture the specific sources of emissions that are contributing to visibility impairment at the Class I area.
82

Texas's approach did not consider the size or location of point sources, despite articulating a specific focus on point sources,
83

or the total emissions captured to support that their approach and chosen threshold resulted in a reasonable identification of sources for analysis in development of the long term strategy. This problem is evident in Texas's 2021 Regional Haze Plan, where several AOIs contained no sources identified for further consideration and several large emission sources with Q/d values far exceeding Texas's Q/d threshold of five being excluded from further consideration because they were located outside of Texas's generated AOIs.

81
Texas discusses its AOI and Q/d analysis in section 7.2.1 of its 2021 Texas Regional Haze Plan.

82
The 2019 Guidance describes a source selection approach utilizing residence time analysis that selects sources for further analysis by giving each point source a score that takes into account the source's emissions, the daily values of light extinction at a Class I area, the distance between the source and a Class I area, and the relative frequency with which wind trajectories indicate that each source is upwind of the IMPROVE monitoring site. 2019 Guidance at 13. This is the general approach followed by CenSARA and WRAP.

83
Texas found that on an individual basis point sources are the largest contributors to visibility impairment in Class I areas. 2021 Texas Regional Haze Plan at 7-3.

For example, W A Parish is located just outside of Texas's ammonium sulfate AOIs for both Caney Creek and Wichita Mountains, and outside of Texas's ammonium sulfate AOI for Big Bend.
84

The SO
2
Q/d values for W A Parish are 32.2 for Caney Creek, 28.2 for Wichita Mountains, and 25.1 for Big Bend.
85

Tolk Generating Station is also located outside of Texas's ammonium sulfate AOI for Salt Creek; however, it has a Q/d value of over 84.
86

Ammonium sulfate is the largest contributor to observed light extinction at Salt Creek
87

but Texas did not identify
any
source of SO
2
emissions for further analysis due to the application of their AOI brightline test and selected EWRT threshold, despite the large SO
2
emissions from Tolk and the relative proximity of the facility to Salt Creek.
88

Given the large emissions from these facilities, these sources likely are meaningfully contributing to visibility impairment, even if they happen to fall outside of the chosen Texas AOIs. Based on its analysis of other coal-fired EGUs with no controls or underperforming controls, had Texas selected these sources for further evaluation under the four factors, Texas may have found cost-effective controls available, resulting in emission reductions that may have been necessary for inclusion in its long-term strategy to make reasonable progress toward meeting the national goal. Moreover, Texas did not explain how not evaluating these high-emitting sources nonetheless results in a long-term strategy that makes reasonable progress toward the national goal.

84

See
2021 Texas Regional Haze Plan, Figure 7-2 at 7-5; AOI for Big Bend located in Texas's EWRT AMDA spreadsheet on TCEQ's AMDA website at
https://www.tceq.texas.gov/assets/public/implementation/air/sip/haze/EWRT_AMDA_Pivot_final.xlsx.
This spreadsheet is also available in our docket as “Texas EWRT AMDA spreadsheet.xlsx”.

85

See
“EPA Q_d Spreadsheet.xlsx” available in the docket for this action. The information included in the EPA's spreadsheet used information available in our docket as “Texas EWRT AMDA spreadsheet.xlsx”.
See also
Letter from Arkansas Department of Energy and Environment to TCEQ requesting that TCEQ consider, among other sources, whether performing a four-factor analysis is appropriate for the W A Parish facility in accordance with 40 CFR 51.308(f)(2)(i) due to impacts on Caney Creek based on CenSARA's AOI study (Feb. 4, 2020). The letter is available in Appendix A of Texas's 2021 Regional Haze Plan at 84 of 227.
See also
Letter from Oklahoma Department of Environmental Quality to TCEQ requesting that TCEQ consider further evaluating the W A Parish facility based on its identification that the source is reasonably anticipated to contribute to visibility impairment at the Wichita Mountains Wilderness Area (July 17, 2020). The letter is available in Appendix A of Texas's 2021 Regional Haze Plan at 125 of 227.

86

See
AOI for Salt Creek located in “Texas EWRT AMDA spreadsheet.xlsx” available in the docket for this action.
See
“EPA Q_d Spreadsheet.xlsx” available in the docket for this action.
See also
Letter from New Mexico Environment Department to TCEQ requesting among other things that Texas specifically evaluate the Tolk facility for additional controls based on its impact to Class I areas in New Mexico, including Salt Creek (Feb. 2, 2021). The letter is available in Appendix A of Texas's 2021 Regional Haze Plan at 111 of 227.
See also,
information provided by the FLMs during consultation that Tolk and W A Parish merit further evaluation based on emissions and potential emission reductions available. The information provided by the FLMs is available in Appendix A of Texas's 2021 Regional Haze Plan at 205 of 227.

87

See
2021 Texas Regional Haze Plan, appendix F, Figure 1-60.

88
EPA used information from Texas's EWRT AMDA spreadsheet, also available in our docket as “Texas EWRT AMDA spreadsheet.xlsx”. We used the same information to calculate the SO
2
Q/d values for Tolk at White Mountain (56) and at Wheeler Peak (42.7).

We therefore find Texas's unjustified use of its selected threshold and resulting AOIs as a brightline cutoff in

source selection to be unreasonable. Texas's methodology resulted in several of the highest emitting SO
2
stationary point sources in the State of Texas not being selected for further evaluation of controls to improve visibility impairment at the Class I areas they likely impact, and in the case of some Class I areas, no sources selected at all for further analysis using the four statutory factors for those areas.

iii. PSAT Modeling Results Further Demonstrate Unreasonableness of Texas's Source Selection Methodology

The 2019 Guidance identifies photochemical modeling and the use of source apportionment modeling as possible methods to assess PM species impacts from sources or groups of sources for source selection.
89

Texas conducted photochemical source apportionment modeling (known as the Particulate Matter Source Apportionment Technology, or PSAT, function of CAMx modeling) as part of its 2021 Regional Haze Plan to evaluate the impact of emissions from source categories on visibility in Class I areas.
90

While Texas did not conduct PSAT modeling for the explicit purpose of source selection, Texas nevertheless included the results of the PSAT modeling in its SIP.
91

The EPA finds Texas's own PSAT modeling results illustrate the flaws in Texas's source selection methodology.

89
2019 Guidance at 14-15.

90
2021 Texas Regional Haze Plan at 8-2.

91
As explained in our 2019 Guidance, photochemical models are a more detailed and sophisticated technique for evaluating visibility impacts. Photochemical modeling considers the dispersion transformation and deposition processes. Source apportionment can “tag” and track emissions sources by any combination of region and sector, or by individual source. As evidenced in Appendix A of Texas's 2021 Regional Haze Plan, Texas had the results of the PSAT modeling at least by March 31, 2020, when Texas presented the results to the FLMs during a consultation meeting.

The TCEQ failed to address in its 2021 Regional Haze Plan how its source selection approach and resulting failure to select sources for further analysis to address visibility impairment at Big Bend are consistent with the CAA's statutory goal and Regional Haze Rule requirements.
92

TCEQ's source selection methodology did not identify any sources for further analysis of control measures that may be necessary to include in its long-term strategy to make reasonable progress at Big Bend. The TCEQ's PSAT model results indicate that emissions from Texas anthropogenic sources account for over 10% of the total light extinction at Big Bend, and 67% of the light extinction due to U.S. anthropogenic emissions.
93

The influence from Texas sources on light extinction at Big Bend is approximately double the influence from anthropogenic sources in the rest of the U.S. combined.
94

While Texas states that visibility at Big Bend is heavily influenced by international emissions, the TCEQ has already accounted for this by adjusting the glidepath for its Class I areas to remove visibility impairment from international emissions, consistent with the EPA's guidance, and thus should not be used as a rationale for not evaluating sources for additional control measures. CAA 169A(a)(1), (b)(2) and the RHR require states to make reasonable progress towards addressing anthropogenic impairment from U.S. sources in the second planning period in furtherance of Congress's national goal.

92
CAA 169A(a)(1), (b)(2); 40 CFR 51.308(f)(2).

93

See
2021 Texas Regional Haze Plan Figure 8-21 at 8-46.

94

See
2021 Texas Regional Haze Plan Figu

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2024-23341. Public record. Not legal advice.