Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 103737 

as it does not have applicable or related 

Tribal laws. 

G. Executive Order: 13045 Protection of 

Children From Environmental Health & 

Safety Risks 

The EPA interprets E.O. 13045 as 

applying only to those regulatory 

actions that concern environmental 

health or safety risks that the EPA has 

reason to believe may 

disproportionately affect children, per 

the definition of ‘‘covered regulatory 

action’’ in section 2–202 of the 

Executive Order. Therefore, this action 

is not subject to Executive Order 13045 

because it merely proposes to 

disapprove SIP revisions. Furthermore, 

the EPA’s Policy on Children’s Health 

does not apply to this action. 

H. Executive Order 13211: Actions That 

Significantly Affect Energy Supply, 

Distribution or Use 

This action is not subject to E.O. 

13211 (66 FR 28355, May 22, 2001), 

because it is not a significant regulatory 

action under E.O. 12866. 

I. National Technology Transfer and 

Advancement Act 

Section 12(d) of the NTTAA directs 

the EPA to use voluntary consensus 

standards in its regulatory activities 

unless to do so would be inconsistent 

with applicable law or otherwise 

impractical. This action is not subject to 

the requirements of section 12(d) of the 

NTTAA (15 U.S.C. 272 note) because 

application of those requirements would 

be inconsistent with the CAA. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations 

Executive Order 12898 (Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations, 59 FR 7629, 

February 16, 1994) directs Federal 

agencies to identify and address 

‘‘disproportionately high and adverse 

human health or environmental effects’’ 

of their actions on communities with 

environmental justice (EJ) concerns to 

the greatest extent practicable and 

permitted by law. Executive Order 

14096 (Revitalizing Our Nation’s 

Commitment to Environmental Justice 

for All, 88 FR 25251, April 26, 2023) 

builds on and supplements E.O. 12898 

and defines EJ as, among other things, 

‘‘the just treatment and meaningful 

involvement of all people, regardless of 

income, race, color, national origin, or 

Tribal affiliation, or disability in agency 

decision-making and other Federal 

activities that affect human health and 

the environment.’’ 

The air agency did not evaluate EJ 

considerations as part of its SIP 

submittal; the CAA and applicable 

implementing regulations neither 

prohibit nor require such an evaluation. 

EPA did not perform an EJ analysis and 

did not consider EJ in this action. Due 

to the nature of the action being taken 

here, this action is expected to have a 

neutral to positive impact on the air 

quality of the affected area. 

Consideration of EJ is not required as 

part of this action, and there is no 

information in the record inconsistent 

with the stated goal of E.O. 12898/14096 

of achieving EJ for communities with EJ 

concerns. 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Incorporation by 

reference, Intergovernmental relations, 

Nitrogen dioxide, Ozone, Reporting and 

recordkeeping requirements, Volatile 

organic compounds. 

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

Dated: December 12, 2024. 

Earthea Nance, 

Regional Administrator, Region 6. 

[FR Doc. 2024–29935 Filed 12–18–24; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R09–OAR–2024–0459; FRL–12287– 

01–R9] 

Partial Approval and Partial 

Disapproval of Air Quality 

Implementation Plans; California; 

Regional Haze State Implementation 

Plan for the Second Implementation 

Period 

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 California 

on August 9, 2022 (hereinafter the 

‘‘2022 California Regional Haze Plan’’ or 

‘‘the Plan’’), under the Clean Air Act 

(CAA) and the EPA’s Regional Haze 

Rule for the program’s second 

implementation period. California’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 CAA sections 110 

and 169A. 

DATES: Written comments must be 

received on or before February 3, 2025. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R09– 

OAR–2024–0459 at https://

www.regulations.gov. For comments 

submitted at Regulations.gov, follow the 

online instructions for submitting 

comments. Once submitted, comments 

cannot be edited or removed from 

Regulations.gov. The EPA may publish 

any comment received to its public 

docket. Do not submit electronically any 

information you consider to be 

confidential business information (CBI) 

or other information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. The EPA will generally not 

consider comments or comment 

contents located outside of the primary 

submission (i.e., on the web, cloud, or 

other file sharing system). For 

additional submission methods, please 

contact the person identified in the FOR

FURTHER INFORMATION CONTACT section. 

For the full EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

https://www.epa.gov/dockets/ 

commenting-epa-dockets. If you need 

assistance in a language other than 

English or if you are a person with a 

disability who needs a reasonable 

accommodation at no cost to you, please 

contact the person identified in the FOR

FURTHER INFORMATION CONTACT section. 

FOR FURTHER INFORMATION CONTACT: 

Laura Lawrence, Planning Section 

(ARD–2–1), Planning & Analysis 

Branch, EPA Region IX, 75 Hawthorne 

Street, San Francisco, CA 94105, 415– 

972–3407, or by email at 

lawrence.laura@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Throughout this document, ‘‘we,’’ ‘‘us,’’ 

and ‘‘our’’ refer to the EPA. 

Table of Contents 

I. What action is the EPA proposing? 

II. Background and Requirements for 

Regional Haze Plans 


lotter on DSK11XQN23PROD with PROPOSALS1
103738 Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 

1CAA 169A. 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. 

2CAA 169A(a)(1). 

3CAA 169A(a)(4). 

4 45 FR 80084 (December 2, 1980). 

5CAA 169B. 

6 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. 

7 64 FR 35714. 

8There 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 it being scattered and absorbed as 

it passes through the atmosphere. Atmospheric light 

extinction (bext) is a metric used for expressing 

visibility and is measured in inverse megameters 

(Mm¥1). The EPA’s August 20, 2019 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 because it is not 

a logarithmic function. See, e.g., 2019 Guidance at 

16, 19, https://www.epa.gov/visibility/guidanceregional-haze-state-implementation-plans-secondimplementation-period. The formula for the 

deciview is 10 ln (bext)/10 Mm¥1). 40 CFR 51.301. 

9CAA 169A(b)(2). 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). See also 40 

CFR 51.308(b), (f) (establishing submission dates for 

iterative regional haze SIP revisions). 

10CAA 169A(b)(2)(B). 

11CAA 169A(b)(2)(A); 40 CFR 51.308(d), (e). 

12 40 CFR 51.308(b). 

13 64 FR 35768 (July 1, 1999). 

14 Id. at 35721. In addition to each of the fifty 

states, the EPA also concluded that the Virgin 

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 California’s 

Regional Haze Submission for the 

Second Implementation Period 

A. Background on California’s First 

Implementation Period SIP Submission 

B. California’s Second Implementation 

Period SIP Submission 

C. Identification of Class I Areas 

D. Calculations of Baseline, Current, and 

Natural Visibility Conditions; Progress to 

Date; and the Uniform Rate of Progress 

E. Long-Term Strategy for Regional Haze 

F. Reasonable Progress Goals 

G. Additional Monitoring To Assess 

Reasonably Attributable Visibility 

Impairment 

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. Statutory and Executive Order Reviews 

I. What action is the EPA proposing? 

On August 9, 2022, the California Air 

Resources Board (CARB) submitted the 

2022 California Regional Haze Plan to 

address the requirements of the CAA’s 

regional haze program pursuant to CAA 

sections 169A and 169B and 40 CFR 

51.308. For the reasons described in this 

document, the EPA is proposing to 

approve the elements of the Plan related 

to requirements contained in 40 CFR 

51.308(f)(1), 40 CFR 51.308(f)(4)–(6), 

and 40 CFR 51.308(g)(1)–(5). The EPA is 

proposing to disapprove the elements of 

the Plan related to requirements 

contained in 40 CFR 51.308(f)(2), 40 

CFR 51.308(f)(3), and 40 CFR 

51.308(i)(2)–(4). 

II. Background and Requirements for 

Regional Haze Plans 

A. Regional Haze Background 

In the 1977 CAA Amendments, 

Congress created a program for 

protecting visibility in the nation’s 

mandatory Class I Federal areas, which 

include certain national parks and 

wilderness areas.1 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.’’ 2 The CAA further directs 

the EPA to promulgate regulations to 

assure reasonable progress toward 

meeting this national goal.3 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.4 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.5 The EPA promulgated the 

Regional Haze Rule (RHR), codified at 

40 CFR 51.308,6 on July 1, 1999.7 These 

regional haze regulations are a central 

component of the EPA’s comprehensive 

visibility protection program for Class I 

areas. 

Regional haze is visibility impairment 

that is produced by a multitude of 

anthropogenic sources and activities 

which are located across a broad 

geographic area and that emit pollutants 

that impair visibility. Visibility 

impairing pollutants include fine and 

coarse particulate matter (PM) (e.g., 

sulfates, nitrates, organic carbon, 

elemental carbon, and soil dust) and 

their precursors (e.g., sulfur dioxide 

(SO2), nitrogen oxides (NOX), and, in 

some cases, volatile organic compounds 

(VOC) and ammonia (NH3)). Fine 

particle precursors react in the 

atmosphere to form fine particulate 

matter (PM2.5), which impairs visibility 

by scattering and absorbing light. 

Visibility impairment reduces the 

perception of clarity and color, as well 

as visible distance.8

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.9

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.’’ 10 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).11

States’ first regional haze SIPs were due 

by December 17, 2007,12 with 

subsequent SIP submissions containing 

updated long-term strategies originally 

due July 31, 2018, and every ten years 

thereafter.13 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.14


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 103739 

Islands and District of Columbia must also submit 

regional haze plans 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). 

15CAA 169A(g)(1); 40 CFR 51.308(d)(1). 

16 40 CFR 51.308(d)(1)(i)(B), (d)(2). The EPA 

established the URP framework in the 1999 RHR to 

provide ‘‘an equitable analytical approach’’ to 

assessing the rate of visibility improvement at Class 

I areas across the country. The start point for the 

URP analysis is 2004 and the endpoint was 

calculated based on the amount of visibility 

improvement that was anticipated to result from 

implementation of existing CAA programs over the 

period from the mid-1990s to approximately 2005. 

Assuming this rate of progress would continue into 

the future, the EPA determined that natural 

visibility conditions would be reached in 60 years, 

or 2064 (60 years from the baseline starting point 

of 2004). However, the EPA did not establish 2064 

as the year by which the national goal must be 

reached. 64 FR at 35731–32. That is, the URP and 

the 2064 date are not enforceable targets but are 

rather tools that ‘‘allow for analytical comparisons 

between the rate of progress that would be achieved 

by the state’s chosen set of control measures and the 

URP.’’ 82 FR 3078, 3084 (January 10, 2017). 

17 40 CFR 51.308(d)(3). 18 40 CFR 51.308(d)(3)(i), (ii). 19 40 CFR 51.308(d)(4). 20See 40 CFR 51.308(g) and (h). 21The EPA’s regulation 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 RooseveltCampobello International Park, the Chairman of the 

Roosevelt-Campobello International Park 

Commission.’’ 40 CFR 51.301. 

22 82 FR 3078 (January 10, 2017). 

23 Guidance on Regional Haze State 

Implementation Plans for the Second 

Implementation Period, https://www.epa.gov/ 

visibility/guidance-regional-haze-stateimplementation-plans-second-implementationperiod, EPA Office of Air Quality Planning and 

Standards, Research Triangle Park (August 20, 

2019). 

24Clarifications Regarding Regional Haze State 

Implementation Plans for the Second 

Implementation Period, https://www.epa.gov/ 

system/files/documents/2021-07/clarificationsregarding-regional-haze-state-implementationplans-for-the-second-implementation-period.pdf, 

EPA Office of Air Quality Planning and Standards, 

Research Triangle Park (July 8, 2021). 

25Technical Guidance on Tracking Visibility 

Progress for the Second Implementation Period of 

the Regional Haze Program, https://www.epa.gov/ 

visibility/technical-guidance-tracking-visibilityprogress-second-implementation-period-regional, 

EPA Office of Air Quality Planning and Standards, 

Research Triangle Park (December 20, 2018). 

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.15

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.16 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.’’ 17 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.18 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.19 Finally, the 1999 RHR 

required states to submit periodic 

progress reports, which are 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,20 and to consult 

with the Federal Land Manager(s) 21

(FLMs) responsible for each Class I area 

according to the requirements in CAA 

169A(d) and 40 CFR 51.308(i). 

On January 10, 2017, the EPA 

promulgated revisions to the RHR that 

apply for the second and subsequent 

implementation periods.22 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’’).23 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’’).24 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’’),25 and the June 

2020 ‘‘Recommendation for the Use of 

Patched and Substituted Data and 


lotter on DSK11XQN23PROD with PROPOSALS1
103740 Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 

26Recommendation 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-datausage-and-completeness-regional-haze-program, 

EPA Office of Air Quality Planning and Standards, 

Research Triangle Park (June 3, 2020). 

27See generally 2021 Clarifications Memo. 

28See, e.g., H.R. Rep No. 95–294 p. 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’’). 

29RPOs are sometimes also referred to as ‘‘multijurisdictional organizations,’’ or MJOs. For the 

purposes of this notice, the terms RPO and MJO are 

synonymous. 30CAA 169A(b)(2)(B). 

31The 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). 32See 40 CFR 51.308(f), (f)(2). 33See 40 CFR 51.308(f)(1). 34The 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. 

35See 40 CFR 51.308(f)(2). 

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’’).26

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.27 This is 

consistent with Congress’s 

determination that a visibility 

protection program is needed in 

addition to the CAA’s National Ambient 

Air Quality Standards (NAAQS) and 

Prevention of Significant Deterioration 

programs, as further emission 

reductions may be necessary to 

adequately protect visibility in Class I 

areas throughout the country.28

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 longterm, 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),29 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. 

The Western Regional Air Partnership 

(WRAP), one of the five RPOs described 

above, is a collaborative effort of state 

governments, tribal governments, and 

various Federal agencies established to 

initiate and coordinate activities 

associated with the management of 

regional haze, visibility, and other air 

quality issues in the western corridor of 

the United States. Member states (listed 

alphabetically) include: Alaska, 

Arizona, California, Colorado, Idaho, 

Montana, Nevada, New Mexico, North 

Dakota, Oregon, South Dakota, Utah, 

Washington, and Wyoming. The Federal 

partner members of WRAP are the EPA, 

U.S. National Parks Service (NPS), U.S. 

Fish and Wildlife Service (FWS), and 

U.S. Forest Service (USFS). There are 

also 468 federally recognized Tribes 

within the WRAP region. 

III. Requirements for Regional Haze 

Plans for the Second Implementation 

Period 

Under the CAA and the EPA’s 

regulations, all 50 States, the District of 

Columbia, and the U.S. Virgin Islands 

are required to submit regional haze 

SIPs satisfying the applicable 

requirements for the second 

implementation period of the regional 

haze program by July 31, 2021. Each 

state’s SIP must contain a long-term 

strategy for making reasonable progress 

toward meeting the national goal of 

remedying any existing and preventing 

any future anthropogenic visibility 

impairment in Class I areas.30 To this 

end, section 51.308(f) lays out the 

process by which states determine what 

constitutes their long-term strategies, 

with the order of the requirements in 

section 51.308(f)(1) through (3) 

generally mirroring the order of the 

steps in the reasonable progress 

analysis 31 and (f)(4) through (6) 

containing additional, related 

requirements. Broadly speaking, a state 

first must identify the Class I areas 

within the state and determine the Class 

I areas outside the state in which 

visibility may be affected by emissions 

from the state. These are the Class I 

areas that must be addressed in the 

state’s long-term strategy.32 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.33 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’’ 34 that states must 

consider in developing their long-term 

strategies.35 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 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 103741 

36 40 CFR 51.308(f)(2)–(3). 

37 40 CFR 51.308(f)(5). 

38 40 CFR 51.308(i). 

39See CAA 169A(b)(2); CAA 110(a). 

40CAA 110(c)(1). 

41 64 FR 35720–35722. 

42 Id. at 35721. 

43 2019 Guidance, pp. 8–9. 

44The 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. 

45 40 CFR 51.301. This notice also refers to the 20 

percent clearest and 20 percent most 

anthropogenically impaired days as the ‘‘clearest’’ 

and ‘‘most impaired’’ or ‘‘most anthropogenically 

impaired’’ days, respectively. 

46 40 CFR 51.308(f)(1)(i), (iii). 

47The 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.’’ 

48 40 CFR 51.308(f)(1)(ii). 

49Being on or below the URP is not a ‘‘safe 

harbor’’; i.e., achieving the URP does not mean that 

a Class I area is making ‘‘reasonable progress’’ and 

does not relieve a state from using the four statutory 

factors to determine what level of control is needed 

to achieve such progress. See, e.g., 82 FR 3093. 

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.36

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 section 51.308(g)(1) 

through (5) pertaining to periodic 

reports describing progress towards the 

RPGs,37 as well as requirements for FLM 

consultation that apply to all visibility 

protection SIPs and SIP revisions.38

A state must submit its regional haze 

SIP and subsequent SIP revisions to the 

EPA according to the requirements 

applicable to all SIP revisions under the 

CAA and the EPA’s regulations.39 Upon 

EPA approval, a SIP is enforceable by 

the Agency and the public under the 

CAA. If the EPA finds that a state fails 

to make a required SIP revision, or if the 

EPA finds that a state’s SIP is 

incomplete or disapproves the SIP, the 

Agency must promulgate a federal 

implementation plan (FIP) that satisfies 

the applicable requirements.40

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,41

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.’’ 42

A state must determine which Class I 

areas must be addressed by its SIP by 

evaluating the total emissions of 

visibility impairing pollutants from all 

sources within the state. While the RHR 

does not require this evaluation to be 

conducted in any particular manner, the 

EPA’s 2019 Guidance provides 

recommendations for how such an 

assessment might be accomplished, 

including by, where appropriate, using 

the determinations previously made for 

the first implementation period.43 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 40 CFR 

51.308(f)(1) related to tracking visibility 

improvement over time. The 

requirements of this subsection apply 

only to states having Class I areas within 

their borders; the required calculations 

must be made for each such Class I area. 

The EPA’s 2018 Visibility Tracking 

Guidance 44 provides recommendations 

to assist states in satisfying their 

obligations under section 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. 

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 percent clearest (the 20 percent 

of monitored days in a calendar year 

with the lowest values of the deciview 

index) and 20 percent most impaired 

days (the 20 percent of monitored days 

in a calendar year with the highest 

amounts of anthropogenic visibility 

impairment).45 A state must calculate 

visibility conditions for both the 20 

percent clearest and 20 percent 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).46 States must also 

calculate natural visibility conditions 

for the clearest and most impaired 

days,47 by estimating the conditions that 

would exist on those two sets of days 

absent anthropogenic visibility 

impairment.48 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. 

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 nonenforceable benchmark against which to 

assess a Class I area’s rate of visibility 

improvement.49 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 


lotter on DSK11XQN23PROD with PROPOSALS1
103742 Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 

50 82 FR 3107 footnote 116. 

51 40 CFR 51.308(f)(2). 

52See 40 CFR 51.308(f)(2)(i). 

53See 2019 Guidance, p. 43; 2021 Clarifications 

Memo, pp. 8–10. 

54 40 CFR 51.308(f)(2). 

55 40 CFR 51.308(f)(2)(i). 

56 2019 Guidance p. 12, 2021 Clarifications Memo 

p. 4. 

57 2021 Clarifications Memo, p. 4. 

58 2019 Guidance, p. 9. 

59 2021 Clarifications Memo, p. 3. 

60 2021 Clarifications Memo, p. 4. 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), pp. 87–88. 

61The 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 emissions 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. 

62CAA 169A(g)(1). 

63 82 FR 3091. 

64 ‘‘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 

anthropogenic sources and to give states 

the flexibility to determine that limiting 

the use of wildland-prescribed fire is 

not necessary for reasonable progress.50

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 

section 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).’’ 51 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.52

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.53 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.54

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.55

A threshold question at this step is 

which visibility impairing pollutants 

will be analyzed. As the EPA previously 

explained, consistent with the first 

implementation period, the EPA 

generally expects that each state will 

analyze at least SO2 and NOX in 

selecting sources and determining 

control measures.56 A state that chooses 

not to consider at least these two 

pollutants should demonstrate why 

such consideration would be 

unreasonable.57

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.’’ 58 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.’’ 59

The EPA explained in the 2021 

Clarifications Memo that each state has 

an obligation to submit a long-term 

strategy that addresses the regional haze 

visibility impairment that results from 

emissions from within that state. Thus, 

source selection should focus on the instate 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 outof-state contributors.60

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.61 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.’’ 62 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.’’ 63

Thus, for each source it has selected for 

four-factor analysis,64 a state must 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 103743 

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. 

65 Id. at 3088. 

66 2019 Guidance, p. 29. 

67 2021 Clarifications Memo, p. 7. 

68 2021 Clarifications Memo, p. 7. 

69See 2021 Clarifications Memo pp. 5, 10. 

70See, 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, p. 186; 2019 Guidance, pp. 36–37. 71See 2019 Guidance, pp. 30–36. 72 2021 Clarifications Memo, pp. 12–15. 73 2021 Clarifications Memo, p. 13. 74States 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 EPA for inclusion 

in their SIPs but are not required to do so. See, e.g., 

82 FR at 3108–3109 (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). 

75See CAA 169A(a)(1). 

76See 2021 Clarifications Memo, pp. 8–10. 

consider a ‘‘meaningful set’’ of 

technically feasible control options for 

reducing emissions of visibility 

impairing pollutants.65 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.’’ 66

The EPA’s 2021 Clarifications Memo 

provides further guidance on what 

constitutes a reasonable set of control 

options for consideration: ‘‘A reasonable 

four-factor analysis will consider the 

full range of potentially reasonable 

options for reducing emissions.’’ 67 In 

addition to add-on controls and other 

retrofits (i.e., new emissions reduction 

measures for sources), the EPA 

explained that states should generally 

analyze efficiency improvements for 

sources’ existing measures as control 

options in their four-factor analyses, as 

in many cases such improvements are 

reasonable given that they typically 

involve only additional operation and 

maintenance costs. Additionally, the 

2021 Clarifications Memo provides that 

states that have assumed a higher 

emissions rate than a source has 

achieved or could potentially achieve 

using its existing measures should also 

consider lower emissions rates as 

potential control options. That is, a state 

should consider a source’s recent actual 

and projected emission rates to 

determine if it could reasonably attain 

lower emission rates with its existing 

measures. If so, the state should analyze 

the lower emission rate as a control 

option for reducing emissions.68 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.’’ 69

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.70 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.71 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.72

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.73 Ultimately, 

while states have discretion to 

reasonably weigh the factors and to 

determine what level of control is 

needed, section 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.’’ 

As explained above, section 

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 

section 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.74 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.75 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.76 If the state can make such a 

demonstration, it need not include a 

source’s existing measures in the longterm strategy or its SIP. 

As with source selection, the 

characterization of information on each 

of the factors is also subject to the 

documentation requirement in section 

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, section 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 


lotter on DSK11XQN23PROD with PROPOSALS1
103744 Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 

77See 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). 

78The 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. 

79See 2019 Guidance, p. 21. 

80 2021 Clarifications Memo, p. 13. 

81 40 CFR 51.308(f)(2)(ii)(A). 

82 40 CFR 51.308(f)(2)(ii)(B). 

83 40 CFR 51.308(f)(2)(ii)(C). 

84See id.; 2019 Guidance, p. 53. 

85 40 CFR 51.308(f)(2)(ii)(C). 

86 82 FR 3091. 

87See 40 CFR 51.308(f)(3)(iii)–(iv). 

88 40 CFR 51.308(f)(3)(i). 

89RPGs are intended to reflect the projected 

impacts of the measures all contributing states 

include in their long-term strategies. However, due 

to the timing of analyses, control determinations by 

other states, and other on-going emissions changes, 

a particular state’s RPGs may not reflect all control 

measures and emissions reductions that are 

expected to occur by the end of the implementation 

period. The 2019 Guidance provides 

recommendations for addressing the timing of RPG 

calculations when states are developing their longterm strategies on disparate schedules, as well as for 

adjusting RPGs using a post-modeling approach. 

2019 Guidance, pp. 47–48. 

90See 2021 Clarifications Memo p. 6. 

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.77 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. 

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’’ 78 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.79 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.80

Because the air pollution that causes 

regional haze crosses state boundaries, 

section 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.81 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.82 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.83 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.84

Under all circumstances, a state must 

document in its SIP submission all 

substantive consultations with other 

contributing states.85

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 fourfactor analysis.’’ 86 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.87 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.88 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.89 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.90

For the second implementation 

period, the RPGs are set for 2028. 

Reasonable progress goals are not 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 103745 

91 40 CFR 51.308(f)(3)(iii). 

92 2019 Guidance, p. 46. 

93See 40 CFR 51.308(f)(1)(i), 82 FR 3097–98. 

94 40 CFR 51.308(f)(3)(ii). 

95See 2019 Guidance, pp. 50–51. 

96See 82 FR 3093, 3099–3100; 2019 Guidance, p. 

22; 2021 Clarifications Memo, pp. 15–16. 

97 40 CFR 51.308(f)(6), (f)(6)(i), (f)(6)(iv). 

98 40 CFR 51.308(f)(6)(ii), (iii). 

99See ‘‘Step 8: Additional requirements for 

regional haze SIPs’’ in 2019 Guidance, p. 55. 

100 40 CFR 51.308(f)(6)(vi). 

101 Id. 

102The 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. 

enforceable targets; 91 rather, they 

‘‘provide a way for the states to check 

the projected outcome of the [long-term 

strategy] against the goals for visibility 

improvement.’’ 92 While states are not 

legally obligated to achieve the visibility 

conditions described in their RPGs, 

section 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 2000–2004.93

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.94 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.95

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-thebooks and/or on-the-way control 

measures (i.e., control measures already 

required or anticipated before the fourfactor 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.’’ 96

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.97 The 

Interagency Monitoring of Protected 

Visual Environments (IMPROVE) 

monitoring data is used to determine the 

20 percent most anthropogenically 

impaired and 20 percent 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.98 Section 51.308(f)(6)(v) further 

requires that all states’ SIPs provide for 

a statewide inventory of emissions of 

pollutants that are reasonably 

anticipated to cause or contribute to 

visibility impairment in any Class I area; 

the inventory must include emissions 

for the most recent year for which data 

are available and estimates of future 

projected emissions. States must also 

include commitments to update their 

inventories periodically. The 

inventories themselves do not need to 

be included as elements in the SIP and 

are not subject to the EPA review as part 

of the Agency’s evaluation of a SIP 

revision.99 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.100 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.101

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 40 

CFR 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.’’ 102 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 


lotter on DSK11XQN23PROD with PROPOSALS1
103746 Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 

103See 81 FR 26942, 26950 (May 4, 2016); 82 FR 

3119 (January 10, 2017). 

104 40 CFR 51.308(g)(1) and (2). 

105 40 CFR 51.308(g)(3)(i)(B). 

106See 40 CFR 51.308(g)(3)(ii)(B). 

107See 40 CFR 51.308(g)(3)(iii)(B), (f)(5). 

108See 40 CFR 51.308(g)(4), (f)(5). 

109 40 CFR 51.308(i)(2). 

110 40 CFR 51.308(i)(2). 

111 40 CFR 51.308(i)(3). 

112 40 CFR 51.308(i)(4). 

113 76 FR 34608. 

114 80 FR 17327. 

115Public comments and CARB responses are 

available on the CARB website at https://

ww2.arb.ca.gov/sites/default/files/2023-01/Regional

HazeResponseToPublicComments.pdf. 

impairment, the state must include in 

its SIP revision for the second 

implementation period an appropriate 

strategy for evaluating such impairment. 

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.103

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.104

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, section 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,105 and 

then to calculate the difference between 

those current conditions and baseline 

(2000–2004) visibility conditions to 

assess progress made to date.106 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.107 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.108 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 longterm 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.’’ 109 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.110 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.111

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.112

IV. The EPA’s Evaluation of California’s 

Regional Haze Submission for the 

Second Implementation Period 

A. Background on California’s First 

Implementation Period SIP Submission 

California submitted its initial 

regional haze plan under 40 CFR 51.308 

to the EPA on March 16, 2009 

(hereinafter ‘‘2009 Submittal’’). The EPA 

approved the 2009 Submittal on June 

14, 2011.113 On June 16, 2014, 

California submitted its Progress Report 

to meet the requirements of 40 CFR 

51.308(g) and (h). The EPA approved 

the Progress Report on April 1, 2015.114

B. California’s Second Implementation 

Period SIP Submission 

In accordance with CAA sections 

169A and the RHR at 40 CFR 51.308(f), 

on August 9, 2022, CARB submitted a 

revision to the California SIP to address 

its regional haze obligations for the 

second implementation period, which 

runs through 2028. California made its 

2022 Regional Haze Plan available for 

public comment on May 13, 2022. 

CARB received and responded to public 

comments.115

The following sections describe the 

Plan, including analyses conducted by 

the WRAP and CARB, CARB’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 the EPA’s evaluation of 

the Plan 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 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 103747 

116 64 FR at 35721. 117The EPA determined that ‘‘there is more than 

sufficient evidence to support our conclusion that 

emissions from each of the 48 contiguous states and 

the District of Columbia 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 plans because they 

contain Class I areas. 

118 Id. 119 Id. at 35722. 120 Id. at 35721. 

121 Id. at 35722. 

122 82 FR at 3094. 

123 2022 California Regional Haze Plan, pp. 64– 

68. 

124 Id. at 64. 

125 40 CFR 51.308(f)(1)(vi)(B). 

126Plan, p. 22. 

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.’’ 116 In concluding that 

each of the contiguous 48 states and the 

District of Columbia meet this 

threshold,117 the EPA relied on ‘‘a large 

body of evidence demonstrat[ing] that 

long-range transport of fine PM 

contributes to regional haze,’’ 118

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.’’ 119

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.’’ 120 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.’’ 121 The EPA’s 

2017 revisions to the RHR did not 

disturb this conclusion.122

California has 29 Class I areas within 

its borders: Redwood National Park; 

Marble Mountain Wilderness; Lava Beds 

National Monument; South Warner 

Wilderness; Thousand Lakes 

Wilderness; Lassen Volcanic National 

Park; Caribou Wilderness; Yolla BollyMiddle Eel Wilderness (includes land 

managed by the U.S. Bureau of Land 

Management); Point Reyes National 

Seashore; Ventana Wilderness; 

Pinnacles National Monument; 

Desolation Wilderness; Mokelumne 

Wilderness; Emigrant Wilderness; 

Hoover Wilderness; Yosemite National 

Park; Ansel Adams Wilderness; Kaiser 

Wilderness; John Muir Wilderness; 

Kings Canyon National Park; Sequoia 

National Park; Dome Lands Wilderness; 

San Rafael Wilderness; San Gabriel 

Wilderness; Cucamonga Wilderness; 

San Gorgonio Wilderness; San Jacinto 

Wilderness; Agua Tibia Wilderness; and 

Joshua Tree National Park. 

In its submission, CARB also briefly 

assessed the contribution of emissions 

from California to visibility impairment 

at Class I areas in three neighboring 

states: Oregon, Nevada, and Arizona.123

CARB noted that the projected share of 

ammonium nitrate and ammonium 

sulfate attributable to California sources 

ranges from 0.1 to 1.7 percent and 0.1 

to 1.0 percent, respectively, of the total 

light extinction budgets at Class I areas 

in neighboring states.124 These total 

light extinction budgets include 

international and natural emissions, 

which cannot be addressed by states, 

and therefore do not provide a 

meaningful assessment of the 

contribution of California’s sources 

relative to other U.S. anthropogenic 

sources. CARB also did not consider 

whether emissions from California may 

affect Class I areas in any states other 

than its three neighboring states.1

As discussed in further detail below, 

the EPA is proposing to find that the 

2022 California Regional Haze Plan does 

not fully meet the requirements of 40 

CFR 51.308(f)(2) related to the 

development of a long-term strategy. 

Relatedly, the State failed to identify 

specific out-of-state Class I areas may be 

affected by emissions from California. 

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.125

In the 2022 California Regional Haze 

Plan, CARB used visibility data from 

IMPROVE monitoring sites for 2000– 

2004 for baseline visibility.126 CARB 

also obtained visibility data from 

IMPROVE monitoring data for 2014– 

2018, which it used to represent current 

visibility conditions. CARB determined 

natural visibility by estimating the 

natural concentrations of visibilityimpairing pollutants and then 

calculating total light extinction with 

the IMPROVE algorithm. Comparison of 

baseline conditions to natural visibility 

conditions shows the improvement 

necessary to attain natural visibility by 

2064 measured in deciviews of 

improvement per year that represents 

the URP. The calculations of baseline, 

current, and natural visibility 

conditions, as well as the progress to 

date and differences between current 

visibility condition and natural 

visibility condition can be found in 

Chapter 2 of the 2022 California 

Regional Haze Plan and are summarized 

in tables 1 and 2 of this document. 


lotter on DSK11XQN23PROD with PROPOSALS1
103748 Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 

TABLE 1—VISIBILITY CONDITIONS FOR CLEAREST DAYS

[dv] 

IMPROVE site Class I areas Baseline Current Progress 

to date Natural Difference 

LABE1 .................................... Lava Beds National Monument .....................

South Warner Wilderness Area 

3.2 2.5 0.7 1.3 1.2 

REDW1 .................................. Redwood National Park ................................ 6.1 5.3 0.8 3.5 1.8 

TRIN1 ..................................... Marble Mountain Wilderness .........................

Yolla Bolly-Middle Eel Wilderness Area 

3.4 3.1 0.3 1.2 1.9 

LAVO1 ................................... Caribou Wilderness Area ..............................

Lassen Volcanic National Park 

Thousand Lakes Wilderness 

2.7 2.2 0.5 1.0 1.2 

BLIS1 ..................................... Desolation Wilderness Area ..........................

Mokelumne Wilderness Area 

2.5 1.8 0.7 0.4 1.4 

PORE1 ................................... Point Reyes National Seashore .................... 10.5 8.2 2.3 4.8 3.4 

YOSE1 ................................... Emigrant Wilderness Area .............................

Yosemite National Park 

3.4 2.9 0.5 1.0 1.9 

HOOV1 .................................. Hoover Wilderness Area ............................... 1.4 1.0 0.4 0.1 0.9 

KAIS1 ..................................... Ansel Adams Wilderness Area ......................

John Muir Wilderness Area 

Kaiser Wilderness Area 

2.3 1.5 0.8 0.0 1.5 

PINN1 .................................... Pinnacles National Park ................................

Ventana Wilderness Area 

8.9 7.7 1.2 3.5 4.2 

SEQU1 ................................... Kings Canyon National Park .........................

Sequoia National Park 

8.8 7.0 1.8 2.3 4.7 

RAFA1 ................................... San Rafael Wilderness Area ......................... 6.5 4.9 1.6 1.8 3.1 

DOME1 .................................. Domeland Wilderness Area ........................... 5.1 4.4 0.7 1.2 3.2 

SAGA1 ................................... Cucamonga Wilderness Area ........................

San Gabriel Wilderness Area 

4.8 2.8 2.0 0.4 2.4 

SAGO1 ................................... San Gorgonio Wilderness Area .....................

San Jacinto Wilderness Area 

5.4 3.3 2.1 1.2 2.1 

JOSH1 ................................... Joshua Tree National Park ............................ 6.1 4.7 1.4 1.7 3.0 

AGTI1 ..................................... Agua Tibia Wilderness Area .......................... 9.6 7.0 2.6 2.9 4.1 

Source: 2022 California Regional Haze Plan, 38, Tables 2–3, 2–4, 2–6, 2–7, 2–9 and 2–10. Baseline conditions are for 2000–2004. Current 

Conditions are for 2014–2018. Progress to date is Baseline Minus Current. Difference is Current minus Natural Conditions. 

TABLE 2—VISIBILITY CONDITIONS FOR MOST-IMPAIRED DAYS

[dv] 

IMPROVE site Class I areas Baseline Current Progress 

to date Natural Difference 

LABE1 .................................... Lava Beds National Monument .....................

South Warner Wilderness Area 

11.3 9.7 1.6 6.2 3.5 

REDW1 .................................. Redwood National Park ................................ 13.7 12.6 1.1 8.6 4.0 

TRIN1 ..................................... Marble Mountain Wilderness .........................

Yolla Bolly-Middle Eel Wild. Area 

11.9 10.4 1.5 6.5 3.9 

LAVO1 ................................... Caribou Wilderness Area ..............................

Lassen Volcanic National Park 

Thousand Lakes Wilderness 

11.5 10.2 1.3 6.1 4.1 

BLIS1 ..................................... Desolation Wilderness Area ..........................

Mokelumne Wilderness Area 

10.1 9.3 0.8 4.9 4.4 

PORE1 ................................... Point Reyes National Seashore .................... 19.4 15.3 4.1 9.7 5.6 

YOSE1 ................................... Emigrant Wilderness Area .............................

Yosemite National Park 

13.5 11.6 1.9 6.3 5.3 

HOOV1 .................................. Hoover Wilderness Area ............................... 8.9 7.8 1.1 4.9 2.9 

KAIS1 ..................................... Ansel Adams Wilderness Area ......................

John Muir Wilderness Area 

Kaiser Wilderness Area 

12.9 11.0 1.9 6.1 4.9 

PINN1 .................................... Pinnacles National Park ................................

Ventana Wilderness Area 

17.0 14.1 2.9 6.9 7.2 

SEQU1 ................................... Kings Canyon National Park .........................

Sequoia National Park 

23.2 18.4 4.8 6.3 12.1 

RAFA1 ................................... San Rafael Wilderness Area ......................... 17.3 14.1 3.2 6.8 7.3 

DOME1 .................................. Domeland Wilderness Area ........................... 17.2 15.1 2.1 6.2 8.9 

SAGA1 ................................... Cucamonga Wilderness Area ........................

San Gabriel Wilderness Area 

17.9 13.2 4.7 6.1 7.1 

SAGO1 ................................... San Gorgonio Wilderness Area .....................

San Jacinto Wilderness Area 

20.4 14.4 6.0 6.2 8.2 

JOSH1 ................................... Joshua Tree National Park ............................ 17.7 12.9 4.8 6.1 6.8 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 103749 

127Plan, pp. 51, 135–136. 128Memorandum from Richard A. Wayland, 

Director, Air Quality Assessment Division, EPA, to 

Regional Air Division Directors, Subject: 

‘‘Availability of Modeling Data and Associated 

Technical Support Document for the EPA’s 

Updated 2028 Visibility Air Quality Modeling,’’ 

September 19, 2019, available at https://

www.epa.gov/visibility/technical-supportdocument-epas-updated-2028-regional-hazemodeling. 129Memorandum from Richard A. Wayland, 

Director, Air Quality Assessment Division, EPA, to 

Regional Air Division Directors, Subject: ‘‘Technical 

Guidance on Tracking Visibility Progress for the 

Second Implementation Period of the Regional Haze 

Program,’’ December 20, 2018, available at https:// 

www.epa.gov/sites/default/files/2018-12/ 

documents/technical_guidance_tracking_visibility_

progress.pdf. 

130WRAP Technical Support System, http://

views.cira.colostate.edu/tssv2/. 

TABLE 2—VISIBILITY CONDITIONS FOR MOST-IMPAIRED DAYS—Continued 

[dv] 

IMPROVE site Class I areas Baseline Current Progress 

to date Natural Difference 

AGTI1 ..................................... Agua Tibia Wilderness Area .......................... 21.6 16.3 5.3 7.7 8.6 

Source: 2022 California Regional Haze Plan, Tables 2–3, 2–5, 2–6, 2–8, 2–9 and 2–11. Baseline conditions are for 2000–2004. Current Conditions are for 2014–2018. Progress to date is Baseline Minus Current. Difference is Current minus Natural Conditions. 

CARB chose to adjust its URP for 

international anthropogenic impacts 

and to account for the impacts of 

wildland prescribed fires using 

adjustments developed by the WRAP.127

The WRAP/WAQS Regional Haze 

modeling platform used scaled 2014 NEI 

wildland prescribed fire data for 

purposes of calculating the URP 

adjustments. WRAP used the results 

from the CAMx 2028OTBa2 High-Level 

Source Apportionment run to obtain 

concentrations due to international 

emissions and to prescribed fire. These 

concentrations were then used in a 

relative sense to estimate the 

contributions for use in adjusting the 

URP. That is, the modeled relative effect 

of removing their emissions (relative 

response factors) was applied to 

projections of 2028 concentrations. The 

resulting concentration decrease was 

taken as the contribution of these 

sources. The international and 

prescribed fire contributions were 

therefore calculated in a fashion 

consistent with each other and with the 

2028 projections. This approach is 

consistent with the default method 

described in the EPA’s September 2019 

regional haze modeling Technical 

Support Document (‘‘EPA 2019 

Modeling TSD’’) 128 and with the source 

apportionment approach described in 

the EPA’s 2018 Visibility Tracking 

Guidance.129 Two different adjusted 

glidepath options, ‘‘International 

Emissions Only (A)’’ and ‘‘International 

Emissions + Wildland Rx Fire (B)’’, 

were made available on the WRAP 

Technical Support System (TSS) 130 to 

adjust the URP glidepath end points 

projections at 2064 for Class I Federal 

areas on the most impaired days. 

TABLE 3—URP FOR MOST-IMPAIRED DAYS

[dv/year] 

IMPROVE site Class I area Unadjusted URP Adjusted URP 

LABE1 ...................................................... Lava Beds National Monument .................................................

South Warner Wilderness Area 

0.09 0.07 

REDW1 .................................................... Redwood National Park ............................................................ 0.09 0.07 

TRIN1 ....................................................... Marble Mountain Wilderness Area ............................................

Yolla Bolly-Middle Eel Wilderness Area 

0.09 0.05 

LAVO1 ...................................................... Thousand Lakes Wilderness Area ............................................

Lassen Volcanic National Park 

Caribou Wilderness Area 

0.09 0.06 

BLIS1 ....................................................... Desolation Wilderness Area ......................................................

Mokelumne Wilderness Area 

0.09 0.06 

PORE1 ..................................................... Point Reyes National Seashore ................................................ 0.16 0.14 

YOSE1 ..................................................... Emigrant Wilderness Area ........................................................

Yosemite National Park 

0.12 0.08 

HOOV1 ..................................................... Hoover Wilderness Area ........................................................... 0.07 0.03 

KAIS1 ....................................................... Ansel Adams Wilderness Area .................................................

John Muir Wilderness Area 

Kaiser Wilderness Area 

0.11 0.06 

PINN1 ....................................................... Pinnacles National Park ............................................................

Ventana Wilderness Area 

a 0.11 0.13 

SEQU1 ..................................................... Kings Canyon National Park .....................................................

Sequoia National Park 

0.28 0.21 

RAFA1 ...................................................... San Rafael Wilderness Area ..................................................... 0.18 0.14 

DOME1 .................................................... Domeland Wilderness Area ...................................................... 0.18 0.13 

SAGA1 ..................................................... San Gabriel Wilderness Area ...................................................

Cucamonga Wilderness Area 

0.20 0.17 

SAGO1 ..................................................... San Gorgonio Wilderness Area ................................................

San Jacinto Wilderness Area 

0.24 0.20 

JOSH1 ...................................................... Joshua Tree National Park ....................................................... 0.19 0.15 

AGTI1 ....................................................... Agua Tibia Wilderness Area ..................................................... 0.23 0.18 

Source: 2022 California Regional Haze Plan, Tables 8–3, 8–4, 8–5. 


lotter on DSK11XQN23PROD with PROPOSALS1
103750 Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 

131CAA 169A(b)(2)(B). 

132 40 CFR 51.308(f)(2)(i). 

133 40 CFR 51.308(f)(2). 134 40 CFR 51.308(f)(2)(iii). 

135 2022 California Regional Haze Plan, pp. 69– 

70. 

136 Id. at 72. 

137 2022 California Regional Haze Plan, p. 73, 

Figure 5–5. 

138 Id. 

aThe unadjusted URP for the PINN1 IMPROVE monitor reported in the Plan appears to have been incorrectly transcribed from its source. The 

reported value of 0.11 dv/year should actually be 0.17 dv/year, based on the 2004 and the 2024 natural conditions endpoint data reported in the 

WRAP TSS. This error does not affect other calculations or conclusions in the Plan. 

We propose to find that the 2022 

California Regional Haze Plan meets the 

requirements of 40 CFR 51.308(f)(1) 

related to the calculations of baseline, 

current, and natural visibility 

conditions; progress to date; differences 

between current visibility conditions 

and natural visibility conditions, and 

the uniform rate of progress for each of 

its Class I areas for the second 

implementation period. We also 

propose to find that CARB has estimated 

the impacts from anthropogenic sources 

outside the United States and wildland 

prescribed fires using scientifically 

valid data and methods. 

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.131 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.132 Each state’s long-term 

strategy must include the enforceable 

emission limitations, compliance 

schedules, and other measures that are 

necessary to make reasonable 

progress.133 All new (i.e., additional) 

measures that are the outcome of fourfactor 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 

section 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.134

The consultation requirements of 

section 51.308(f)(2)(ii) provide that 

states must consult with other states 

that are reasonably anticipated to 

contribute to visibility impairment in a 

Class I area to develop coordinated 

emission management strategies 

containing the emission reductions 

measures that are necessary to make 

reasonable progress. Section 

51.308(f)(2)(ii)(A) and (B) require states 

to consider the emission reduction 

measures identified by other states as 

necessary for reasonable progress and to 

include agreed upon measures in their 

SIPs, respectively. Section 

51.308(f)(2)(ii)(C) speaks to what 

happens if states cannot agree on what 

measures are necessary to make 

reasonable progress. 

Section 51.308(f)(2)(iii) requires that 

the emissions information considered to 

determine the measures that are 

necessary to make reasonable progress 

include information on emissions for 

the most recent year for which the state 

has submitted triennial emissions data 

to the EPA (or a more recent year), with 

a 12-month exemption period for newly 

submitted data. 

The following sections summarize 

how the 2022 California Regional Haze 

SIP addressed the requirements of 

section 51.308(f)(2) and the EPA’s 

evaluation with respect to these 

requirements. 

1. Determination of Which Pollutants To 

Consider 

To evaluate which pollutants had the 

largest impact at California’s Class I 

areas, CARB considered light extinction 

budgets that showed the relative 

contribution from different pollutants 

measured during 2014–2018 at 

IMPROVE monitors in the State. Overall 

(including both U.S. and non-U.S. 

sources) CARB found that, on the most 

impaired days, ammonium nitrate and 

ammonium sulfate comprised the 

largest portion of the light extinction 

budgets at sites near urban areas, while 

ammonium sulfate and organic mass 

formed the largest portion of light 

extinction budgets at sites further from 

urban areas.135 When looking only at 

U.S. anthropogenic sources, CARB 

concluded that ammonium nitrate was 

generally the dominant visibility 

reducing PM species, comprising an 

average of 49 percent of light extinction 

at Class I areas in California during 

2014–2018.136 CARB also noted that, in 

prospective light extinction budgets 

developed for 2028, ammonium nitrate 

comprises an average of 38 percent of 

light extinction at Class I areas in 

California. Based on these 

considerations, CARB chose to focus its 

long-term strategy solely on NOX, which 

is considered the limiting precursor for 

ammonium nitrate. 

While we support CARB’s focus on 

impacts from U.S. anthropogenic 

emissions, we find that its 

determination to focus its regional haze 

control strategy exclusively on NOX

during this planning period is not 

adequately supported. The conclusion 

that NOX is the dominant visibility 

reducing PM species is not true for all 

of California’s Class I areas, even when 

considering only U.S. anthropogenic 

sources. For example, prospective U.S. 

light extinction budgets for the most 

impaired days in 2028 indicate that at 

TRIN1 (representing Marble Mountain 

Wilderness and Yolla Bolly-Middle Eel 

Wilderness Area), BLIS1 (representing 

Desolation Wilderness Area and 

Mokelumne Wilderness Area), and 

JOSH1 (representing Joshua Tree 

National Park), the contribution from 

U.S. anthropogenic sources from organic 

mass will exceed the contribution from 

ammonium nitrate on the most impaired 

days.137 And, even for the monitors 

where ammonium nitrate is projected to 

have the largest contribution in 2028, 

contributions from other species, such 

as organic matter and ammonium 

sulfate, may be significant as well. For 

example, in the prospective U.S. 

anthropogenic light extinction budgets 

for the most impaired days in 2028, the 

contribution from organic matter 

exceeds 20% of total impairment at nine 

monitors, and the contribution from 

ammonium sulfate exceeds 20% at one 

monitor.138

In addition, CARB has not adequately 

considered whether anthropogenic 

emissions of other pollutants from 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 103751 

139See 40 CFR 51.308(f)(2). 

140 2022 California Regional Haze Plan, pp. 65– 

67. 

141WRAP Technical Support System, Modeling 

Express Tools, ‘‘WRAP State Source Group 

Contributions—U.S. Anthro’’, http://

views.cira.colostate.edu/tssv2/Express/ 

ModelingTools.aspx. 

142 Id. at 75–76. 

California may contribute significantly 

to visibility impairment at out-of-state 

Class I areas.139 For example, 

ammonium sulfate constitutes a greater 

share of the total extinction budget than 

ammonium nitrate at all of the Class I 

areas in neighboring states.140 In 

addition, modeling results available 

from the WRAP TSS 141 how that for 

ammonium sulfate from anthropogenic 

SO2 emissions, California industrial 

point sources (nonEGUs) have the 

largest contribution to impairment of 

any state/source category combination 

for three Class I areas in other States: 

Zion, Bryce Canyon, and Grand Canyon 

National Parks. Further, the California 

nonEGU contribution is comparable to 

that from Arizona nonEGUs for the 

Mazatzal, Sierra Ancha, and Sycamore 

Wilderness Areas in Arizona, and 

comparable to the EGU contribution at 

Capitol Reef National Park. 

For these reasons, it is not clear that 

ammonium nitrate is the dominant 

species resulting from U.S. 

anthropogenic emissions at all Class I 

areas affected by emissions from 

California and therefore, we determine 

that it was unreasonable for CARB not 

to conduct any evaluation of potential 

controls for the other pollutants. 

2. Source Selection 

In the Plan, CARB states that its 

source selection goal for this regional 

haze plan was to consider sources that 

accounted for at least 50 percent of the 

NOX emissions in the inventory, 

considering both 2014 and 2017 

emissions inventories. Noting the 

significant role of mobile source 

emissions in California and the State’s 

authority to establish emissions 

standards for certain mobile sources, 

CARB chose to focus its source-selection 

process on mobile sources, but also 

considered stationary sources. 

a. Mobile Sources 

CARB provided a summary of 2017 

and projected 2028 NOX emissions in 

tons per day (tpd) from various mobile 

source sectors in table 5–1 of the Plan, 

which is reproduced as table 4 of this 

document. Based on these data, CARB 

selected light and medium-duty 

vehicles, heavy-duty trucks, off-road 

equipment, trains, and ocean-going 

vessels for four-factor analysis, 

explaining that emissions from these 

five source groups account for 60 

percent of NOX emissions in the 2017 

inventory and are projected to account 

for 50 percent of NOX emissions in 

2028.142 CARB also noted that it did not 

select aircraft for analysis because 

Federal action would be needed to 

address this source category. 

TABLE 4—CARB MOBILE SOURCE SECTOR EMISSIONS

Sector description 2017 Emissions 

(tpd) 

Projected 2028 

emissions 

(tpd) 

On-Road: Heavy-Duty Trucks ......................................................................................................................... 409 227 

On-Road: Light & Medium-Duty Trucks .......................................................................................................... 111 31 

On-Road: Light-Duty Passenger ..................................................................................................................... 70 26 

On-Road: Other (Buses, Motorcycles, Motorhomes) ...................................................................................... 29 18 

Off-Road: Off-Road Equipment ....................................................................................................................... 222 132 

Off-Road: Trains .............................................................................................................................................. 78 37 

Off-Road: Aircraft ............................................................................................................................................. 46 59 

Off-Road: Ocean-Going Vessels ..................................................................................................................... 28 37 

Off-Road: Commercial Harbor Craft ................................................................................................................ 19 18 

Off-Road: Recreational Boats .......................................................................................................................... 16 13 

Off-Road: Recreational Vehicles ..................................................................................................................... 1 1 

With respect to NOX emissions from 

mobile sources specifically, we find that 

CARB selected a reasonable set of 

source categories for four-factor 

analysis. However, as discussed in 

section IV.E.3.a of this document, we 

find that CARB did not adequately 

analyze and consider the four factors in 

relation to these source categories. 

b. Stationary Sources 

CARB conducted a four-step process 

to select sources for four-factor analysis: 

• Step 1: Calculate NOX emissions (Q) 

in tons divided by distance (d) in km 

(Q/d) and screen in facilities with a NOX

Q/d greater than five for further 

consideration. 

• Step 2: Review device level 

emissions inventories and screen out 

sources if actual emissions or emissions 

under State or local jurisdiction resulted 

in a Q/d less than five. 

• Step 3: Review existing controls, 

planned controls, and proposed 

operational changes. Screen out sources 

if this information indicated that a full 

four factor analysis would likely result 

in the conclusion that reasonable 

controls are in place. 

• Step 4: Proceed with consideration 

and evaluation of four statutory factors. 

We evaluate steps 1–3 of CARB’s 

analysis in this section and step 4 in 

section IV.E.3.b of this document. 

In step 1 of its stationary source 

screening process, CARB calculated 

NOX-only Q/d values using 2017 NEI 

NOX emissions data and the distance 

between a stationary source and Class I 

areas and selected the sources with a 

Q/d value greater than 5. The results of 

this analysis are summarized in table G– 

1 of the Plan, which is reproduced as 

Table 5 of this document. 

TABLE 5—STATIONARY SOURCES SELECTED AT STEP 1 

Facility name Location with maximum Q/d Distance 

(km) 

2017 NEI 

(tpy) Q/d 

Chevron Products Company ................................ Point Reyes National Seashore ........................... 28 737 26.4 

Lehigh Southwest Cement Company ................... Point Reyes National Seashore ........................... 86 1208 14.0 

Oakland Metropolitan International Airport ........... Point Reyes National Seashore ........................... 50 1262 25.4 


lotter on DSK11XQN23PROD with PROPOSALS1
103752 Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 

143 Id. appendix G, p. 154. 

TABLE 5—STATIONARY SOURCES SELECTED AT STEP 1—Continued 

Facility name Location with maximum Q/d Distance 

(km) 

2017 NEI 

(tpy) Q/d 

Phillips 66 Carbon Plant ....................................... Point Reyes National Seashore ........................... 43 360 8.5 

Phillips 66 Company—San Francisco Refinery ... Point Reyes National Seashore ........................... 43 218 5.1 

San Francisco International Airport ...................... Point Reyes National Seashore ........................... 45 5105 113.4 

San Jose Airport—Norman Y Mineta ................... Point Reyes National Seashore ........................... 92 884 9.6 

Shell Martinez Refinery (now owned by PBF) ..... Point Reyes National Seashore ........................... 53 916 17.2 

Tesoro Refining & Marketing Company Llc ......... Point Reyes National Seashore ........................... 57 360 6.3 

Valero Refining Company ..................................... Point Reyes National Seashore ........................... 52 1013 19.3 

CalPortland Cement—Mojave Plant ..................... Domeland Wilderness Area ................................. 75 1531 20.5 

Granite Construction—Lee Vining ........................ Ansel Adams Wilderness Area ............................ 6 31 5.2 

Kirkwood Powerhouse .......................................... Mokelumne Wilderness Area ............................... 1 10 16.6 

Cal Portland Oro Grande (formerly Riverside) ..... Cucamonga Wilderness Area .............................. 41 1141 27.9 

Cemex—Black Mountain Quarry .......................... San Gorgonio Wilderness Area ........................... 53 5420 101.6 

Mitsubishi Cement ................................................ San Gorgonio Wilderness Area ........................... 33 1944 59.7 

Searles Valley Mineral .......................................... Domeland Wilderness Area ................................. 71 1517 21.3 

Arcata .................................................................... Redwood National Park ....................................... 17 163 9.7 

Collins Pine Co ..................................................... Caribou Wilderness Area ..................................... 12 129 10.4 

Sierra Pacific Industries—Quincy ......................... Caribou Wilderness Area ..................................... 59 392 6.6

Sacramento International Airport .......................... Desolation Wilderness Area ................................. 117 737 6.3 

San Diego International-Lindberg ......................... Agua Tibia Wilderness Area ................................ 74 1580 21.3

Burney Forest Products ........................................ Thousand Lakes Wilderness Area ....................... 17 190 11.2 

Lehigh Southwest Cement Company ................... Thousand Lakes Wilderness Area ....................... 56 603 10.7 

Sierra Pacific Industries—Burney ......................... Thousand Lakes Wilderness Area ....................... 18 157 8.9 

Wheelabrator Shasta E.C.I ................................... Yolla Bolly-Middle Eel Wilderness Area ............... 57 536 9.4 

Bob Hope Airport .................................................. San Gabriel Wilderness Area ............................... 31 375 12.0 

California Steel Industries Inc ............................... Cucamonga Wilderness Area .............................. 16 125 7.8

Chevron Products Co ........................................... San Gabriel Wilderness Area ............................... 52 729 14.0 

Desert View Power ............................................... Joshua Tree National Park .................................. 24 189 7.8 

John Wayne Airport .............................................. Cucamonga Wilderness Area .............................. 62 698 11.3 

Long Beach Daugherty Field Airport .................... San Gabriel Wilderness Area ............................... 49 308 6.3 

Los Angeles International Airport ......................... San Gabriel Wilderness Area ............................... 49 7836 159.0 

New-Indy Ontario, Llc ........................................... Cucamonga Wilderness Area .............................. 18 137 7.5 

Ontario International Airport ................................. Cucamonga Wilderness Area .............................. 17 679 40.2 

Palm Springs International Airport ........................ San Jacinto Wilderness Area ............................... 10 159 16.4

Phillips 66 Co/La Refinery Wilmington Pl ............. San Gabriel Wilderness Area ............................... 58 471 8.1 

Phillips 66 Company/Los Angeles Refinery ......... San Gabriel Wilderness Area ............................... 53 391 7.3 

Tamco ................................................................... Cucamonga Wilderness Area .............................. 13 108 8.3 

Tesoro Refining & Marketing (Carson) ................. San Gabriel Wilderness Area ............................... 51 661 13.0 

Tesoro Refining and Marketing (Wilmington) ....... San Gabriel Wilderness Area ............................... 54 749 13.8 

Torrance Refining (formerly Exxon Mobil) ............ San Gabriel Wilderness Area ............................... 52 924 17.6 

With respect to NOX emissions from 

point sources specifically, we find that 

CARB’s use of a Q/d threshold of 5 

resulted in the selection of a reasonable 

set of sources. However, the Plan only 

included the emissions data and 

distance values for the sources that were 

selected. Therefore, it was not possible 

for the EPA or the public to verify the 

emissions and distance values for 

sources that were not selected. 

In Step 2 of its Stationary Source 

Screening process, CARB screened out 

17 sources based on a ‘‘device-level 

inventory,’’ where ‘‘actual emissions or 

emissions under State or local 

jurisdiction led to a Q/d less than 

five.’’ 143 The sources screened out at 

this stage are summarized in table 6 of 

this document. 

TABLE 6—STATIONARY SOURCES SCREENED OUT AT STEP 2 

Facility name Rationale for screening out 

Oakland Metropolitan International Airport ......... Vast majority of emissions are from aircraft, for which state and local agencies do not have 

authority to set emissions limits. 

San Francisco International Airport .................... Vast majority of emissions are from aircraft, for which state and local agencies do not have 

authority to set emissions limits. 

San Jose Airport—Norman Y Mineta ................. Vast majority of emissions are from aircraft, for which state and local agencies do not have 

authority to set emissions limits. 

Tesoro Refining & Marketing Company Llc ....... The refinery has been idled since 2020 and owner is proposing to convert the refinery to a renewable fuels facility. 

Granite Construction—Lee Vining ...................... Per district staff, actual NOX emissions from this source in 2017 were 0.5 tpy and were consistent with emissions from a typical operating year. 

Kirkwood Powerhouse ........................................ In 2014, Kirkwood Meadows Public Utilities District transitioned to line power and all the generators were transitioned from prime to emergency back-up engines. Actual NOX emissions 

since 2014 have been less than 0.1 tpy. 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 103753 

144See 40 CFR 51.308(f)(2)(iii); Clarifications 

Memo, p. 5. 

145 Id. at 154. 

TABLE 6—STATIONARY SOURCES SCREENED OUT AT STEP 2—Continued 

Facility name Rationale for screening out 

Arcata .................................................................. Vast majority of emissions are from aircraft, for which state and local agencies do not have 

authority to set emissions limits. 

Sacramento International Airport ........................ Vast majority of emissions are from aircraft, for which state and local agencies do not have 

authority to set emissions limits. 

San Diego International-Lindberg ....................... Vast majority of emissions are from aircraft, for which state and local agencies do not have 

authority to set emissions limits. 

Bob Hope Airport ................................................ Vast majority of emissions are from aircraft, for which state and local agencies do not have 

authority to set emissions limits. 

Desert View Power ............................................. Facility is located on Cabazon Indian Reservation land. 

John Wayne Airport ............................................ Vast majority of emissions are from aircraft, for which state and local agencies do not have 

authority to set emissions limits 

Long Beach Daugherty Field Airport .................. Vast majority of emissions are from aircraft, for which state and local agencies do not have 

authority to set emissions limits. 

Los Angeles International Airport ....................... Vast majority of emissions are from aircraft, for which state and local agencies do not have 

authority to set emissions limits. 

Ontario International Airport ............................... Vast majority of emissions are from aircraft, for which state and local agencies do not have 

authority to set emissions limits. 

Palm Springs International Airport ...................... Vast majority of emissions are from aircraft, for which state and local agencies do not have 

authority to set emissions limits. 

Tamco ................................................................. Facility was permanently shut down in January 2021. 

As with step 1, we find that CARB’s 

determinations at step 2 were not 

adequately documented. In particular, 

CARB did not include in the Plan the 

device-level emissions inventory that it 

used to screen out sources. Thus, while 

we find that it was reasonable for the 

State to focus on emissions under State 

and/or local jurisdiction and to 

therefore screen out 12 airports and one 

source on tribal land, for the other 

screened-out sources, additional 

documentation is needed to verify the 

basis upon which the sources were 

screened out.144

In Step 3 of its screening process, 

CARB screened out 24 stationary 

sources based on its determination that 

‘‘information about existing controls, 

planned controls, or planned 

operational changes indicated that a full 

four factor analysis would likely result 

in the conclusion that, for the purposes 

of the regional haze program, reasonable 

controls are in place and no further 

reasonable controls are necessary at this 

time.’’ 145 The controls or measures 

cited by CARB in making this 

determination for the 24 sources include 

existing or anticipated controls required 

by currently applicable district rules, 

expected district rules, permit 

requirements, and/or consent decrees. 

The sources screened out at this step are 

shown in table 7. 

TABLE 7—STATIONARY SOURCES SCREENED OUT AT STEP 3 

Facility name Rationale for screening out 

Chevron Products Company .............................. Multiple furnaces have selective catalytic reduction (SCR) units and permit limits of 40 ppm 

NOX at 3% O2 (8-hour average). Cogeneration turbines have SCR units and emission limits 

of <10 ppm at 15% O2 (3-hour average) and 0.20 lb NOX per million British thermal units 

(MMBtu) as a 30-day rolling average. Facility’s operating permit includes the federal interim 

refinery-wide emissions limit (excluding CO boilers) of 0.20 lb NOX/MMBtu as well as the 

more stringent refinery-wide emissions limit (excluding CO boilers) of 0.033 lb NOX/MMBtu. 

Lehigh Southwest Cement Company ................. Emission limit of 2.0 lb NOX/ton of clinker under federal consent decree. 

Phillips 66 Carbon Plant ..................................... Planned decommissioning of the plant. 

Phillips 66 San Francisco Refinery .................... Planned conversion to facility that would process renewable feedstocks. 

Shell Martinez Refinery ...................................... Turbine boiler is equipped with an SCR system and has NOX emissions limits of less than or 

equal to 5 ppmv NOX at 15% O2. A 2001 EPA consent decree required optimization of NOX

emissions controls for other boilers. Boilers are also subject to Bay Area Air Quality Management District (BAAQMD) Regulation 9, Rule 10 which has been determined to meet Best 

Available Retrofit Control Technology (BARCT) stringency. 

Valero Refining Company ................................... NOX emissions are controlled through SCR systems and low NOX burners. BAAQMD Regulation 9, Rule 10 applies to heaters and boilers (except for CO boilers) at refineries and sets 

the refinery-wide NOX emissions limit at 0.033 lb NOX/MMBtu of heat input (daily average) 

and facility-wide federal limit of 0.20 lb NOX/MMBtu of heat input. 

Cal Portland Mojave Plant .................................. EPA consent decree required installation of selective non-catalytic reduction (SNCR) and established an emissions limit of 2.5 lb NOX/ton of clinker for kiln. Eastern Kern APCD Rule 

425.3 found to be meet BARCT stringency. 

Cemex—Black Mountain Quarry ........................ Federal consent decree established a NOX emission limit of 1.95 lb/ton of clinker. The kilns 

are also subject to Mojave Desert AQMD Rule 1161—Portland Cement Kilns, which was revised in 2018 to meet federal RACT stringency and California BARCT stringency. 

Mitsubishi Cement (Cushenberry Plant) ............. The NOX emissions limit for cement kiln in the Title V permit is 2.8 lb/ton of clinker. 

Cal Portland Oro Grande .................................... The NOX emissions limit for cement kiln is 2.45 lb/ton of clinker. 


lotter on DSK11XQN23PROD with PROPOSALS1
103754 Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 

146https://ww2.arb.ca.gov/our-work/programs/ 

california-state-implementation-plans/statewideefforts/regional-haze. 

147 2019 Guidance, p. 23. 148See, e.g., Memorandum dated May 18, 2006 

from William T. Harnett Director, Air Quality 

Policy Division, EPA, to Regional Air Division 

Directors, Subject: ‘‘Questions Related to RACT in 

8-hour ozone implementation,’’ answer A.1 (‘‘BACT 

requires that new or modified sources adopt the 

best available controls and, as such, the analysis is 

a ‘top-down’ analysis that first looks at the most 

stringent level of control available for a 

source. . . . RACT requires that sources adopt 

controls that are reasonably available and thus they 

may not be the most stringent controls that have 

been adopted for other similar sources.’’) 

149Eastern Kern APCD, ‘‘Final Staff Report, Rule 

425.3,’’ March 8, 2018, p. D–2; Mojave Desert 

AQMD ‘‘Staff Report, Amendments to Rule 1161’’, 

January 22, 2018, appendix F. 

TABLE 7—STATIONARY SOURCES SCREENED OUT AT STEP 3—Continued 

Facility name Rationale for screening out 

Searles Valley Mineral ........................................ The smallest boiler complies with a best available control technology (BACT) emissions limit of 

9 ppmv. All the boilers are subject to Rule 1157.1, which was adopted in 2019 to meet the 

AB 617 expedited BARCT requirements. 

Sierra Pacific Industries—Quincy ....................... NOX emissions are controlled by ammonia injection. 

Burney Forest Products ...................................... The boilers are equipped with an SNCR unit with anhydrous ammonia injection for NOX control. Title V permit includes BACT emissions limits for NOX.

Lehigh Southwest Cement Company ................. EPA Consent Decree limits NOX emissions to 1.95 lb/ton clinker with combustion controls or 

SNCR. 

Sierra Pacific Industries—Burney ....................... NOX emissions are controlled through ammonia injection, staged combustion controls, flue gas 

recirculation, and low NOX burners when combusting natural gas at start-up/shutdown. 

Wheelabrator Shasta E.C.I ................................. NOX emissions are controlled through ammonia injection, staged combustion controls, flue gas 

recirculation, and low NOX burners when combusting natural gas at start-up/shutdown. 

California Steel Industries ................................... By January 2022, the facility is planning to replace two existing 33 MMBtu/hr boilers with two 

new 32.54 MMBtu/hr boilers to comply with a 5 ppm NOX limit in South Coast AQMD Rule 

1146. 

Chevron Products Co ......................................... NOX control equipment includes low NOx burners in heaters/boilers, SCR units, and NOX reducing catalyst in the fluid catalytic cracking unit (FCCU). Recently, the facility replaced five 

heater burners with low NOX burners and the district recently received a proposal from the 

facility to install SCR on two large heaters. South Coast AQMD Rule 1109.1 is being developed for all NOX emitting sources at the refineries. 

New Indy Ontario LLC ........................................ New combined heat and power units placed in operation in the fall of 2019 with BACT limit of 

2 ppm NOX at 15% O2. Boiler required to meet a 5 ppm NOX and 5 ppm NH3 at 3% O2

under South Coast AQMD Rule 1146. 

Phillips 66 Co/Los Angeles Refinery—Carson ... In the last six years, equipment changes have included the installation of an SCR unit on boiler 11 and the reformer heater. South Coast AQMD Rule 1109.1 is being developed for all 

NOX emitting sources at the refineries. 

Phillips 66 Co/LA Refinery Wilmington ............... SCR was recently installed on the FCCU. Boilers and heaters are equipped with low NOX

burners. South Coast AQMD Rule 1109.1 is being developed for all NOX emitting sources at 

the refineries. 

Tesoro Refining and Marketing Co.—Carson 

and Wilmington.

FCCU shutdown at Wilmington completed in October 2018. South Coast AQMD Rule 1109.1 

is being developed for all NOX emitting sources at the refineries. 

Torrance Refining (formerly ExxonMobil) ........... NOX control equipment at the refinery includes low NOX burners in heaters/boilers, SCR units, 

and NOX reducing catalyst in the FCCU. South Coast AQMD Rule 1109.1 is being developed for all NOX emitting sources at the refineries. 

We find that step 3 of CARB’s source 

selection process was flawed in several 

respects. First, as with steps 1 and 2, 

step 3 of CARB’s source selection 

process was inadequately documented. 

In particular, the Plan did not include 

unit-specific emissions and control 

information for all of the sources that 

were screened out. In response to a 

request from NPS, CARB did post a 

device-level emissions inventory on its 

website.146 However, this inventory 

provided only total annual 2017 NOX

emissions and did not include 

information about existing controls or 

emissions limitations. Without this 

information, it is not possible to 

evaluate whether all the units with 

significant NOX emissions are 

effectively controlled. Moreover, the 

device-level inventory was not included 

in the SIP submittal. 

Second, for those units where 

emissions limits were provided, CARB 

did not adequately explain why it was 

reasonable to assume, without 

conducting a four-factor analysis, that 

no additional controls or more stringent 

emissions limitations would be 

reasonable. In particular, for most of the 

screened-out sources, CARB cited 

existing or expected determinations of 

best available retrofit control technology 

(BARCT) under California state law and/ 

or determinations of reasonably 

available control technology (RACT) for 

purposes of Federal ozone requirements 

and/or determinations as part of the 

basis for screening sources out. 

However, while the 2019 Guidance lists 

more stringent controls requirements, 

such as BACT and lowest achievable 

emissions rate (LAER) determinations 

issued since 2013, as examples of 

effective controls,147 it does not list 

RACT determinations as examples an 

effective control. RACT is a less 

stringent requirement than either BACT 

or LAER.148 In addition, some elements 

of BARCT and RACT analyses differ 

from Regional Haze four-factor analyses 

and different cost effectiveness 

thresholds may apply for purposes of 

BARCT and RACT as compared with 

regional haze. For example, Eastern 

Kern APCD Rule 425.3 and Mojave 

Desert AQMD Rule 1161 establish NOX

emissions limits for RACT and BARCT 

that correspond to the use of 

combustion controls, which are 

generally less stringent than postcombustion controls, such as SNCR. The 

Staff Reports for these two rules indicate 

that the cost effectiveness of more 

stringent limits, such as limits 

corresponding to the use of SNCR, 

would range from approximately 

$1,700/ton to $4,100/ton of NOX

removed.149 These $/ton figures are 

within the range of what has been 

considered cost-effective for regional 

haze reasonable progress measures by 

many western states, including 

California’s neighboring states of 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 103755 

150 89 FR 47398, 47415 (May 31, 2024). 

151Nevada Division of Environmental Protection, 

Nevada Regional Haze State Implementation Plan 

for the Second Planning Period at 5–6 (August 

2022), available at https://ndep.nv.gov/uploads/airplan_mod-docs/All_SIP_Chapters.pdf (‘‘NDEP is 

relying on a cost-effectiveness ($/ton reduced) 

threshold of $10,000.’’) 

152 89 FR 13622, 13638 (February 23, 2024). 

153 2019 Guidance pp. 22–23. 

154Averaging times for these emissions limits 

were not provided. 

155Permit 1128–V–2000 (Issued on 5/1/2024); 

Operational Condition 14. 

156Permit 11800001 (Issued on 6/18/20), 

Condition II.A.33. 

157See, e.g., EPA, Control Cost Manual, section 4, 

Chapter 1, Selective Noncatalytic Reduction, p. 1– 

5 (‘‘SNCR was designated as BART for 11 cement 

kilns’’). 

158Permit 223900003 (Issued on 1/8/2021); 

(Significant Permit Modification on 6/23/2021). 

159United States of America. v. CalPortland 

Company, E.D. Cal. Case 1:11-at-00790, Document 

2–1, filed 12/15/11. 

160See table 7 of this document. 

161Plan appendix G, p. 180. 

162Clarifications Memo, pp. 8–10. 

163CAA 169A(b)(2); 40 CFR 51.308(f)(2). 

164 2019 Guidance p.43; Clarifications Memo, 

pp.8–9. 

165Plan, appendix H, p. 185. See also Plan pp. 

83–105 and appendix H. 

166 Id. at 109. 

167See, e.g., id. at 82 (‘‘Integrated planning efforts 

focused on reducing emissions and improving air 

quality to meet California’s air quality, climate, and 

community health goals will yield meaningful 

progress in reducing visibility impairing PM.’’) 

168For the Heavy-Duty Omnibus Regulation, 

CARB estimated a total cost effectiveness of 

$38,788/ton of NOX in 2022–2032, and for the 

Heavy-Duty I/M program, CARB estimated the costeffectiveness to be $31,677/ton of NOX in 2024, 

$5,209/ton of NOX in 2031, and $4,428/ton of NOX

in 2037. CARB did not provide cost-effectiveness 

values for the other measures. 

Arizona,150 Nevada,151 and Oregon.152

Accordingly, it was not reasonable for 

CARB to assume that RACT and/or 

BARCT controls necessarily constitute 

effective controls for purposes of 

regional haze in all cases. 

Instead, under these circumstances, 

CARB should have evaluated such 

controls on a case-by-case basis to 

determine whether it is reasonable to 

assume that a full four-factor analysis 

would likely result in the conclusion 

that no further controls are necessary.153

CARB did not do so in the Plan. For 

example, for the Mitsubishi Cement 

Cushenbury Plant, the Cal Portland 

Mojave Plant, and the Cal Portland Oro 

Grande Cement Plant, CARB cited NOX

emissions limits of 2.8 lb/ton of clinker, 

2.5 lb/ton of clinker, and 2.45 lb/ton of 

clinker, respectively.154 These limits are 

significantly higher than the applicable 

limits at other cement kilns, such as 

National Cement Lebec Unit 042, which 

has a limit of 1.5 lb/ton of clinker (30- 

day) in its Title V Permit.155 The 

Mitsubishi Cement kiln does not have 

SNCR installed.156 Given that many 

other cement kilns have installed SNCR 

as a retrofit NOX control,157 we find that 

CARB did not adequately justify why a 

four-factor analysis would likely result 

in a determination that an emissions 

limit corresponding to SNCR is not 

necessary to make reasonable progress 

at this unit. The two kilns at Cal 

Portland Oro Grande Cement Plant have 

SNCR installed for ‘‘optional use,’’ 158

and the kiln at the Cal Portland Mojave 

Plant has SNCR installed under a 

Consent Decree.159 However, other 

cement kilns in California with SNCR 

are subject to significantly more 

stringent NOX emissions limits than the 

limits at these three kilns.160

Accordingly, we find that CARB did not 

adequately justify why four-factor 

analyses would likely result in a 

determination that no more stringent 

limits are necessary to make reasonable 

progress at these units. Similar 

considerations apply to other units that 

CARB screened out because they had 

installed controls constituting RACT 

and/or BARCT. Therefore, we find it 

was not reasonable for CARB to screen 

out units merely because they had 

installed controls constituting RACT 

and/or BARCT without further 

consideration of the stringency of these 

controls on a unit-specific basis. 

Third, in some instances, CARB relied 

on rules that had not yet been adopted 

at the time of its analysis. For example, 

for the refineries in South Coast, CARB 

stated that ‘‘Rule 1109.1 is being 

developed for all NOX emitting sources 

at the refineries.’’ 161 We find it was not 

reasonable for CARB to screen out 

sources based on the expected future 

applicability of rules that have not yet 

been adopted. 

Finally, for each source that was 

screened out based on existing effective 

measures, CARB should have 

determined whether those measures are 

necessary for reasonable progress. As 

noted in section III.C of this document 

and further explained in the 

Clarifications Memo, generally a source/ 

category’s existing measures are needed 

to prevent future emissions increases 

and are thus needed to make reasonable 

progress.162 If CARB concludes that the 

existing controls at a particular source 

are necessary to make reasonable 

progress, CARB must adopt emissions 

limits based on those controls as part of 

its long-term strategy for the second 

planning period and include those 

limits in its SIP (to the extent they do 

not already exist in the SIP).163

Alternatively, if CARB can demonstrate 

that the source/category will continue to 

implement its existing measures and 

will not increase its emissions rate, it 

may be reasonable for the State to 

conclude that the existing controls are 

not necessary to make reasonable 

progress. In this instance, the emissions 

limits may not need to be adopted into 

the long-term strategy and SIP.164

In sum, due to a lack of 

documentation for steps 1–3 and 

inadequate justification for its 

determinations under step 3, we find 

that CARB’s source selection process for 

stationary sources did not adequately 

address the requirement of 40 CFR 

51.308(f)(2)(i) to provide a description 

of the criteria used to select sources, or 

the requirement of 40 CFR 

51.308(f)(2)(iii) to provide 

documentation of the technical basis 

used to determine emission reduction 

measures. 

3. Four-Factor Analyses and Control 

Determinations 

a. Mobile Sources 

For each of the selected mobile source 

categories, CARB discussed control 

measures that had been identified in 

previous state plans and provided 

information related to the four 

reasonable progress factors in order ‘‘to 

highlight the consideration of the four 

reasonable progress factors embodied in 

CARB’s rule making process.’’ 165 CARB 

stated that, based on this information, it 

identified four control options as 

necessary to make reasonable progress: 

the Heavy-Duty Omnibus Regulation, 

the Heavy-Duty I/M Program 

Regulation, the Advanced Clean Trucks 

Regulation, and the Advanced Clean 

Cars II Regulation.166

We commend CARB’s ambitious ongoing program of mobile source 

emissions control measures, which has 

been developed to meet California’s air 

quality, climate, and community health 

goals.167 However, we find that, while 

CARB presented information about the 

four factors in relation to on-the-books/ 

on-the-way mobile source requirements, 

CARB did not describe if or how it 

weighed the statutory factors to 

determine which controls are necessary 

for reasonable progress. For example, 

while most states have primarily 

considered the cost effectiveness of 

controls in determining which controls 

are necessary to make reasonable 

progress, CARB did not provide costeffectiveness values for most of the 

control measures it considered,168 nor 

did it indicate what level of cost 

effectiveness it considers to be 

reasonable. In the absence of such 

analysis and explanation, we propose 

find that CARB’s consideration of 

mobile source control measures does 


lotter on DSK11XQN23PROD with PROPOSALS1
103756 Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 

169Plan, p. 108. 

170See also CAA 169A(b)(2), 169(b)(2)(B) (the 

CAA requires that each implementation plan for a 

State in which the emissions from may reasonably 

be anticipated to cause or contribute to visibility 

impairment in a Class I area ‘‘contain such emission 

limits, schedules of compliance and other measures 

as may be necessary to make reasonable progress 

toward meeting the national goal, . . . including 

. . . a long-term . . . strategy for making reasonable 

progress[.]’’ 

171The last column of Plan table 7–5, p.131 is 

headed ‘‘2028 Visibility Projections (dv) with 

Potential Additional Controls (PAC2 Emissions).’’ 

While it is not explicitly stated in the Plan, that was 

the WRAP model scenario mainly relied upon in 

the Plan. Unless otherwise indicated, all of the 

Plan’s 2028 projections and RPGs are identical to 

results from WRAP modeling scenario PAC2_

EPAwoF ‘‘PAC2 EPA w/o Fire Projection,’’ 

available in WRAP TSS modeling tools 4 and 5. The 

PAC2 scenario reflected ‘‘Potential Additional 

Controls,’’ including California mobile source 

control measures; the ‘‘woF’’ means ‘‘without fire’’ 

in the calculation of Relative Response Factors to 

apply to monitored or other modeled 

concentrations. 

not meet the requirement of 40 CFR 

52.308(2)(f)(i) to include a description of 

‘‘how the four factors were taken into 

consideration in selecting the measures 

for inclusion’’ in the LTS or the 

requirement of 40 CFR 52.308(2)(f)(iii) 

to provide documentation of the 

technical basis used to determine 

emission reduction measures. 

b. Stationary Sources 

CARB provided a four-factor analysis 

for a single unit: a Keeler Cogeneration 

Boiler at the Collins Pine Company 

wood products and cogeneration facility 

in Chester. As part of this analysis, 

CARB considered several potential 

control options, but concluded that the 

only technically feasible options were 

(1) good combustion practices, which 

are already in effect, and (2) SNCR. 

After evaluating the four factors for the 

SNCR option, CARB determined that 

retrofit of the existing boiler system 

with an SNCR system was not 

reasonable because ‘‘[t]he existing boiler 

configuration does not provide for 

adequate residence time without 

injection of excess reagent, which is 

likely to lead to high levels of ammonia 

slip.’’ 169

CARB found that the use of good 

combustion practices is necessary to 

ensure control of NOX emissions from 

the boiler at Collins Pine. CARB stated 

that good combustion practices are 

already in place at the facility and are 

enforceable as they are a condition of 

the facility’s Title V operating permit. 

However, CARB did not provide a 

demonstration that use of good 

combustion practices was not necessary 

to make reasonable progress. Therefore, 

as explained in section III.C of this 

document, CARB should have 

submitted this measure for SIP 

approval. 

4. Conclusions 

For the reasons described in the 

preceding sections, we propose to find 

that CARB failed to reasonably 

‘‘evaluate and determine the emission 

reduction measures that are necessary to 

make reasonable progress’’ by 

considering the four statutory factors as 

required by 40 CFR 51.308(f)(2)(i) and 

CAA section 169A(g)(1). We also 

propose to find that CARB failed to 

adequately document the technical basis 

that it relied upon to determine these 

emissions reduction measures, as 

required by 40 CFR 51.308(f)(2)(iii). 

In addition, 51.308(f)(2) requires the 

long-term strategy to ‘‘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).’’ As 

described in the preceding sections, 

with the exception of the four mobilesource measures that CARB deemed to 

be necessary for reasonable progress, 

CARB did not clearly identify which 

measures it has determined were 

necessary to make reasonable progress. 

Accordingly, CARB failed to submit to 

the EPA a long-term strategy that 

includes ‘‘the enforceable emissions 

limitations, compliance schedules, and 

other measures that are necessary to 

make reasonable progress’’ as required 

by 40 CFR 51.308(f)(2).170

Consequently, the EPA proposes to 

find that the 2022 California Regional 

Haze Plan does not satisfy the 

requirements of 40 CFR 51.308(f)(2). 

F. Reasonable Progress Goals 

Section 51.308(f)(3) contains the 

requirements pertaining to RPGs for 

each Class I area. Because California is 

host to multiple Class I areas, it is 

subject to both section 51.308(f)(3)(i) 

and, potentially, to (ii). Section 

51.308(f)(3)(i) requires a state in which 

a Class I area is located to establish 

RPGs—one each for the most impaired 

and clearest days for each Class I area— 

reflecting the visibility conditions that 

will be achieved at the end of the 

implementation period as a result of the 

emissions limitations, compliance 

schedules, and other measures required 

under paragraph (f)(2) to be in states’ 

long-term strategies, as well as 

implementation of other CAA 

requirements. The long-term strategies 

as reflected by the RPGs must provide 

for an improvement in visibility on the 

most impaired days relative to the 

baseline period and ensure no 

degradation on the clearest days relative 

to the baseline period. Section 

51.308(f)(3)(ii) applies in circumstances 

in which a Class I area’s RPG for the 

most impaired days represents a slower 

rate of visibility improvement than the 

URP calculated under 40 CFR 

51.308(f)(1)(vi). Under section 

51.308(f)(3)(ii)(A), if the state in which 

a mandatory Class I area is located 

establishes an RPG for the most 

impaired days that provides for a slower 

rate of visibility improvement than the 

URP, the state must demonstrate that 

there are no additional emissions 

reduction measures for anthropogenic 

sources or groups of sources in the state 

that would be reasonable to include in 

its long-term strategy. Section 

51.308(f)(3)(ii)(B) requires that if a state 

contains sources that are reasonably 

anticipated to contribute to visibility 

impairment in a Class I area in another 

state, and the RPG for the most impaired 

days in that Class I area is above the 

URP, the upwind state must provide the 

same demonstration. 

CARB’s RPGs are set out in table 

8–1 of the Plan, which is reproduced as 

table 8 of this document. In the Plan, 

CARB explains that the RPGs for the 

most impaired days are based on the 

emissions inputs that include 

implementation of control programs 

adopted at the time of the emissions 

inventory development and the 

additional aggregate emissions 

reduction commitment proposed in 

CARB’s long-term strategy,171 while the 

RPGs for the clearest days are equal to 

average visibility conditions on the 

clearest days during the 2000–2004 

baseline period. 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 103757 

172Those graphs have the unadjusted and 

adjusted URP glidepath lines crossing each other, 

instead of both starting at the 2004 baseline level 

and having just the 2064 end point adjusted. 

However, comparable graphs available from WRAP 

TSS modeling tool 5 show the same placement of 

2028 RPG with respected to the unadjusted and 

adjusted URP glidepath line as the Plan appendix 

C graphs do. All Class I areas are below the 

unadjusted URP glidepath, except that those 

corresponding to IMPROVE sites REDW1, LAVO1, 

BLIS1, DOME1 are above the unadjusted URP 

glidepath but below the glidepath adjusted for 

international sources and the glidepath adjusted for 

internationals sources and prescribed fire. 

TABLE 8—BASELINE CONDITIONS AND RPGS FOR CLEAREST AND MOST IMPAIRED DAYS

IMPROVE site Class I area 

Clearest 

baseline 

(dv) 

Clearest 

2028 RPG 

(dv) 

Most 

impaired 

baseline 

(dv) 

Most 

impaired 

2028 RPG 

(dv) 

LABE1 ............................................. Lava Beds National Monument ..................................

South Warner Wilderness Area 

3.2 3.2 11.3 8.9 

REDW1 ........................................... Redwood National Park ............................................. 6.1 6.1 13.7 11.9 

TRIN1 .............................................. Marble Mountain Wilderness Area .............................

Yolla Bolly-Middle Eel Wilderness Area 

3.4 3.4 11.9 9.5 

LAVO1 ............................................. Thousand Lakes Wilderness Area .............................

Lassen Volcanic National Park 

Caribou Wilderness Area 

2.7 2.7 11.5 9.4 

BLIS1 .............................................. Desolation Wilderness Area .......................................

Mokelumne Wilderness Area 

2.5 2.5 10.1 8.3 

PORE1 ............................................ Point Reyes National Seashore ................................. 10.5 10.5 19.4 14.4 

YOSE1 ............................................ Emigrant Wilderness Area .........................................

Yosemite National Park 

3.4 3.4 13.5 10.4 

HOOV1 ............................................ Hoover Wilderness Area ............................................ 1.4 1.4 8.9 7.1 

KAIS1 .............................................. Ansel Adams Wilderness Area ..................................

John Muir Wilderness Area 

Kaiser Wilderness Area 

2.3 2.3 12.9 9.8 

PINN1 .............................................. Pinnacles National Park .............................................

Ventana Wilderness Area 

8.9 8.9 17.0 13.0 

SEQU1 ............................................ Kings Canyon National Park ......................................

Sequoia National Park 

8.8 8.8 23.2 16.1 

RAFA1 ............................................. San Rafael Wilderness Area ...................................... 6.5 6.5 17.3 13.0 

DOME1 ........................................... Domeland Wilderness Area ....................................... 5.1 5.1 17.2 13.7 

SAGA1 ............................................ San Gabriel Wilderness Area .....................................

Cucamonga Wilderness Area 

4.8 4.8 17.9 11.5 

SAGO1 ............................................ San Gorgonio Wilderness Area .................................

San Jacinto Wilderness Area 

5.4 5.4 20.4 12.0 

JOSH1 ............................................. Joshua Tree Wilderness Area .................................... 6.1 6.1 17.7 11.3 

AGTI ................................................ Agua Tibia Wilderness Area ...................................... 9.6 9.6 21.6 14.5 

Source: 2022 California Regional Haze Plan Table 8–1: 2028 Reasonable Progress Goals for California Class I Areas. 

In Plan appendix C, CARB also 

provided graphs of observed visibility, 

unadjusted and adjusted URP, and 2028 

RPGs.172 From those CARB concluded 

that 2028 RPGs for all of California’s 

Class I areas are on or below the 

adjusted URP glidepath. 

TABLE 9—CURRENT RATE OF PROGRESS AND URP 

IMPROVE site Class I area 

Current rate 

of progress 

(dv/year) 

Unadjusted URP 

(dv/year) 

Adjusted URP 

(dv/year) 

LABE1 ............................................. Lava Beds National Monument ..................................

South Warner Wilderness Area 

0.11 0.09 0.07 

REDW1 ........................................... Redwood National Park ............................................. 0.08 0.09 0.07 

TRIN1 .............................................. Marble Mountain Wilderness Area .............................

Yolla Bolly-Middle Eel Wilderness Area 

0.11 0.09 0.05 

LAVO1 ............................................ Thousand Lakes Wilderness Area .............................

Lassen Volcanic National Park 

Caribou Wilderness Area 

0.09 0.09 0.06 

BLIS1 .............................................. Desolation Wilderness Area .......................................

Mokelumne Wilderness Area 

0.06 0.09 0.06 

PORE1 ............................................ Point Reyes National Seashore ................................. 0.29 0.16 0.14 

YOSE1 ............................................ Emigrant Wilderness Area .........................................

Yosemite National Park 

0.14 0.12 0.08 

HOOV1 ........................................... Hoover Wilderness Area ............................................ 0.08 0.07 0.03 

KAIS1 .............................................. Ansel Adams Wilderness Area ..................................

John Muir Wilderness Area 

Kaiser Wilderness Area 

0.14 0.11 0.06 

PINN1 ............................................. Pinnacles National Park .............................................

Ventana Wilderness Area 

0.21 0.11 0.13 


lotter on DSK11XQN23PROD with PROPOSALS1
103758 Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 

173Plan Chapter 4. 

TABLE 9—CURRENT RATE OF PROGRESS AND URP—Continued 

IMPROVE site Class I area 

Current rate 

of progress 

(dv/year) 

Unadjusted URP 

(dv/year) 

Adjusted URP 

(dv/year) 

SEQU1 ............................................ Kings Canyon National Park ......................................

Sequoia National Park 

0.34 0.28 0.21 

RAFA1 ............................................ San Rafael Wilderness Area ...................................... 0.23 0.18 0.14

DOME1 ........................................... Domeland Wilderness Area ....................................... 0.15 0.18 0.13 

SAGA1 ............................................ San Gabriel Wilderness Area .....................................

Cucamonga Wilderness Area 

0.34 0.20 0.17 

SAGO1 ............................................ San Gorgonio Wilderness Area .................................

San Jacinto Wilderness Area 

0.43 0.24 0.20 

JOSH1 ............................................ Joshua Tree National Park ........................................ 0.34 0.19 0.15 

AGTI1 .............................................. Agua Tibia Wilderness Area ...................................... 0.38 0.23 0.18 

Source: 2022 California Regional Haze Plan Tables 8–3, 8–4, and 8–5. 

As noted above, we find that CARB’s 

long-term strategy does not meet the 

requirements of section 51.308(f)(2). 

Section 51.308(f)(3)(i) specifies that 

RPGs must reflect ‘‘enforceable 

emissions limitations, compliance 

schedules, and other measures required 

under paragraph (f)(2) of this section.’’ 

In the absence of an approved long-term 

strategy, we cannot approve the 

associated RPGs. In addition, CARB’s 

RPGs for the clearest days are merely 

identical to baseline conditions, rather 

than estimated via a modeling-based 

analysis of the conditions that will be 

achieved at the end of the 

implementation period. We find that 

CARB’s approach is inconsistent with 

the requirement 51.308(f)(3)(i) for RPGs 

to ‘‘reflect the visibility conditions that 

are projected to be achieved by the end 

of the applicable implementation period 

. . .’’ Finally, we also note that CARB 

does not appear to have considered 

whether sources in California are 

reasonably anticipated to contribute to 

visibility impairment in a Class I area in 

another state, whose RPG for the most 

impaired days in that Class I area is 

above the URP, as required under 40 

CFR 51.308(f)(3)(ii)(B). Based on these 

findings, we propose to determine that 

CARB has not satisfied the applicable 

requirements of 40 CFR 51.308(f)(3) 

relating to RPGs and to disapprove 

Chapter 8 of the Plan. 

G. Additional Monitoring To Assess 

Reasonably Attributable Visibility 

Impairment 

Requirements under 40 CFR 

51.308(f)(4) for additional monitoring to 

assess reasonably attributable visibility 

impairment are not applicable to 

California. The EPA and FLMs have not 

previously advised California that 

additional monitoring is needed to 

assess reasonably attributable visibility 

impairment. Therefore, the 

requirements under 40 CFR 51.308(f)(4) 

are not applicable to California at this 

time. 

H. Monitoring Strategy and Other 

Implementation Plan Requirements 

Section 51.308(f)(6) specifies that 

each comprehensive revision of a state’s 

regional haze plan must contain or 

provide for certain elements, including 

monitoring strategies, emissions 

inventories, and any reporting, 

recordkeeping and other measures 

needed to assess and report on 

visibility. A main requirement of this 

subsection is for states with Class I areas 

to submit monitoring strategies for 

measuring, characterizing, and reporting 

on visibility impairment. Compliance 

with this requirement may be met 

through participation in the IMPROVE 

network. In Chapter 2 of the Plan, CARB 

noted that it relies on data from 17 

monitoring sites operated by the 

IMPROVE network to track visibility 

conditions in California’s Class I areas. 

Section 51.308(f)(6)(i) requires SIPs to 

provide for the establishment of any 

additional monitoring sites or 

equipment needed to assess whether 

RPGs to address regional haze for all 

mandatory Class I Federal areas within 

the state are being achieved. CARB 

stated that this requirement is ‘‘not 

applicable,’’ suggesting that CARB 

believes the current IMPROVE network 

is sufficient for this purpose. 

Section 51.308(f)(6)(ii) requires SIPs 

to provide for procedures by which 

monitoring data and other information 

are used in determining the contribution 

of emissions from within the state to 

regional haze visibility impairment at 

mandatory Class I Federal areas both 

within and outside the state. CARB 

relied on source-apportionment 

modeling performed by the WRAP to 

meet this requirement.173 Specifically, 

CARB pointed to both high-level source 

apportionment modeling, which was 

used to estimate how much of each haze 

pollutant was attributable to several 

broad source categories, and low-level 

source apportionment modeling, which 

was used to estimate how much 

ammonium nitrate and ammonium 

sulfate is attributable to regional humanmade sources. 

Section 51.308(f)(6)(iii) does not 

apply to California, as it has a Class I 

area. Section 51.308(f)(6)(iv) requires 

the SIP to provide for the reporting of 

all visibility monitoring data to the 

Administrator at least annually for each 

Class I area in the state. As noted above, 

CARB relies on data from 17 monitoring 

sites operated by the IMPROVE 

Network. 

Section 51.308(f)(6)(v) requires the 

SIP to provide for a statewide inventory 

of emissions of pollutants that are 

reasonably anticipated to cause or 

contribute to visibility impairment, 

including emissions for the most recent 

year for which data are available and 

estimates of future projected emissions. 

It also requires a commitment to update 

the inventory periodically. California 

provides for emissions inventories and 

estimates of future projected emissions 

by participating in WRAP and by 

complying with the EPA’s Air 

Emissions Reporting Rule (AERR). In 40 

CFR part 51, subpart A, the AERR 

requires states to submit updated 

emissions inventories for criteria 

pollutants to the EPA’s Emissions 

Inventory System (EIS) annually or 

triennially depending on the source 

type. The EPA uses the inventory data 

from the EIS to develop the NEI, which 

is a comprehensive estimate of air 

emissions of criteria pollutants, criteria 

precursors, and hazardous air pollutants 

from air emissions sources. The EPA 

releases an NEI every three years. In 

Chapter 3 and appendix E of the Plan, 

CARB provides high-level summaries of 

2014 and 2028 emissions inventories. 

The EPA proposes to find that CARB 

meets the requirements of 40 CFR 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 103759 

174 79 FR 58302, 58304 (September 29, 2014). 

175Letter dated August 23, 2023, from Michael 

Benjamin, Division Chief, Air Quality Planning and 

Science Division, to Matthew Lakin, Acting 

Director, Air and Radiation Division, Region 9 

(submitted electronically August 24, 2023). 

176Plan table 10–1 and Figure 10–1. 

177 Id. Tables 10–4 and 10–5. 

51.308(f)(6)(v) through its ongoing 

compliance with the AERR, its 

compilation of a statewide emissions 

inventories, and its use of WRAP 

modeling. 

Section 51.308(f)(6)(vi) requires the 

SIP to include other elements, including 

reporting, recordkeeping, and other 

measures, necessary to assess and report 

on visibility. The EPA proposes to find 

that CARB has met the requirements of 

40 CFR 51.308(f)(6) as described above, 

including through its continued 

participation in the IMPROVE network 

and the WRAP, and that no further 

elements are necessary at this time for 

CARB to assess and report on visibility 

pursuant to 40 CFR 51.308(f)(6)(vi). 

I. Requirements for Periodic Reports 

Describing Progress Towards the 

Reasonable Progress Goals 

Section 51.308(f)(5) requires that 

periodic comprehensive revisions of 

states’ regional haze plans also address 

the progress report requirements of 40 

CFR 51.308(g)(1) through (5). The 

purpose of these requirements is to 

evaluate progress towards the applicable 

RPGs for each Class I area within the 

state and each Class I area outside the 

state that may be affected by emissions 

from within that state. Sections 

51.308(g)(1) and (2) apply to all states 

and require a description of the status 

of implementation of all measures 

included in a state’s first 

implementation period regional haze 

plan and a summary of the emission 

reductions achieved through 

implementation of those measures. 

Section 51.308(g)(3) applies only to 

states with Class I areas within their 

borders and requires such states to 

assess current visibility conditions, 

changes in visibility relative to baseline 

(2000–2004) visibility conditions, and 

changes in visibility conditions relative 

to the period addressed in the first 

implementation period progress report. 

Section 51.308(g)(4) applies to all states 

and requires an analysis tracking 

changes in emissions of pollutants 

contributing to visibility impairment 

from all sources and sectors since the 

period addressed by the first 

implementation period progress report. 

This provision further specifies the year 

or years through which the analysis 

must extend depending on the type of 

source and the platform through which 

its emissions information is reported. 

Finally, section 51.308(g)(5), which also 

applies to all states, requires an 

assessment of any significant changes in 

anthropogenic emissions within or 

outside the state have occurred since the 

period addressed by the first 

implementation period progress report, 

including whether such changes were 

anticipated and whether they have 

limited or impeded expected progress 

towards reducing emissions and 

improving visibility. 

CARB’s most recent 5-year progress 

report was submitted to the EPA on June 

16, 2014 and presented data analysis for 

the period 2007–2011.174 Therefore, the 

current progress report is required to 

address the time period beginning in 

2012. 

CARB addressed the requirements of 

40 CFR 51.308(g) in Chapter 10 of the 

Plan and provided additional 

supporting information in a technical 

supplement submitted on August 24, 

2023 (‘‘2023 California Regional Haze 

Technical Supplement’’).175

Specifically, to address 51.308(g)(1) and 

(2), CARB provided a summary of 

control measures it adopted between 

2012 and 2018, and statewide emissions 

trends through 2018.176

The EPA proposes to find that the 

Plan meets the requirements of 40 CFR 

51.308(g)(1) and (2) because it describes 

the measures included in the long-term 

strategy from the first implementation 

period, as well as the status of their 

implementation and the emissions 

reductions achieved through such 

implementation. 

The Plan also provides the 5-year 

baseline (2000–2004) visibility 

conditions, the conditions covered in 

the previous progress report (2007– 

2011) and current conditions (2014– 

2018) for the clearest and most impaired 

days.177 The EPA therefore proposes to 

find that the Plan meets the 

requirements of 40 CFR 51.308(g)(3). 

In the 2023 California Regional Haze 

Technical Supplement, CARB provided 

additional supporting information to 

address the requirements of 40 CFR 

51.308(g)(4) and (5). Pursuant to section 

51.308(g)(4), CARB provided a summary 

of emissions of NOX, SO2, PM10, PM2.5, 

VOCs, and NH3 from all sources and 

activities, including from point, 

nonpoint, non-road mobile, and on-road 

mobile sources for the progress report 

period. CARB also provided 2012–2019 

clean air markets program data for all 

sources with emissions of visibility 

impairing pollutants. The EPA is 

therefore proposing to find that the Plan 

satisfies the requirements of section 

51.308(g)(4) by providing emissions 

information for NOX, SO2, PM10, PM2.5, 

VOCs, and NH3 broken down by type of 

sources and activities within the state. 

Pursuant to section 51.308(g)(5), 

CARB provided an assessment of any 

significant changes in anthropogenic 

emissions within or outside the state 

that have occurred since the period 

addressed in the most recent plan, 

including whether or not these changes 

in anthropogenic emissions were 

anticipated in that most recent plan, and 

whether they have limited or impeded 

progress in reducing pollutant 

emissions and improving visibility. 

CARB noted overall average emissions 

reductions of 36 percent for NOX, 45 

percent for SO2, 20 percent for ROG, 

and 28 percent for PM2.5 between the 

2007–2011 period and the 2014–2018 

period. The EPA proposes to find the 

Plan meets the requirements of section 

51.308(g)(5). 

J. Requirements for State and Federal 

Land Manager Coordination 

CAA section 169A(d) requires states 

to consult with FLMs before holding the 

public hearing on a proposed regional 

haze SIP, and to include a summary of 

the FLMs’ conclusions and 

recommendations in the notice to the 

public. In addition, the FLM 

consultation provision in section 

51.308(i)(2) requires a state to provide 

FLMs with an opportunity for 

consultation that is early enough in the 

state’s policy analyses of its emissions 

reduction obligation so that information 

and recommendations provided by the 

FLMs can meaningfully inform the 

state’s decisions on its long-term 

strategy. If the consultation has taken 

place at least 120 days before a public 

hearing or public comment period, the 

opportunity for consultation will be 

deemed early enough. Regardless, the 

opportunity for consultation must be 

provided at least sixty days before a 

public hearing or public comment 

period at the state level. Section 

51.308(i)(2) also provides two 

substantive topics on which FLMs must 

be provided an opportunity to discuss 

with states: assessment of visibility 

impairment in any Class I area and 

recommendations on the development 

and implementation of strategies to 

address visibility impairment. Section 

51.308(i)(3) requires states, in 

developing their implementation plans, 

to include a description of how they 

addressed FLM comments. Section 

51.308(i)(4) requires regional haze plans 

to provide procedures for continuing 

consultation between the State and 

FLMs on the implementation of the 

regional haze program, including 

development and review of SIP 

revisions and progress reports, and on 


lotter on DSK11XQN23PROD with PROPOSALS1
103760 Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 

178Plan, p. 141. 179 42 U.S.C. 7410(k); 40 CFR 52.02(a). 

the implementation of other programs 

having the potential to contribute to 

impairment of visibility in mandatory 

Class I Federal areas. 

In Chapter 9 of the Plan, CARB 

indicates that it held multiple informal 

consultation teleconferences with staff 

from the NPS and the USFS during 

development of its plan.178 CARB sent 

a draft of the Plan to the NPS, FWS, and 

the USFS on February 9, 2022. CARB 

requested that FLM agencies provide 

formal comments on the draft by April 

11, 2022. The comments received from 

Federal land managers and CARB’s 

responses to these comments are 

provided in appendix I of the Plan. 

Chapter 9 also includes a discussion of 

CARB’s procedures for continuing 

consultation with stakeholders, 

including FLMs. 

While CARB did take administrative 

steps to provide the FLMs the requisite 

opportunity to review and provide 

feedback on the state’s initial draft plan, 

the EPA cannot approve the 

requirements under 51.308(f)(i) because 

CARB’s consultation was based on a SIP 

revision that did not meet the required 

statutory and regulatory requirements of 

the CAA and the RHR, respectively. In 

addition, if the EPA finalizes the partial 

approval and partial disapproval of the 

Plan, as proposed in this document, in 

the process of correcting the 

deficiencies outlined above with respect 

to the RHR and statutory requirements, 

the State (or the EPA in the case of an 

eventual FIP) will be required to again 

satisfy the FLM consultation 

requirement under 51.308(i). 

V. Proposed Action 

For the reasons discussed in this 

notice, under CAA section 110(k)(3), the 

EPA is proposing to partially approve 

and partially disapprove the 2022 

California Regional Haze Plan. The EPA 

is proposing to approve the elements of 

the Plan related to requirements 

contained in 40 CFR 51.308(f)(1), 40 

CFR 51.308(f)(4)–(6), and 40 CFR 51.308 

(g)(1)–(5). The EPA is proposing to 

disapprove the elements of the Plan 

related to requirements contained in 40 

CFR 51.308(f)(2), 40 CFR 51.308(f)(3), 

and 40 CFR 51.308(i)(2)–(4). 

Under section 179(a) of the CAA, final 

disapproval of a submittal that 

addresses a requirement of part D, title 

I of the CAA or is required in response 

to a finding of substantial inadequacy as 

described in CAA section 110(k)(5) (SIP 

Call) starts a sanctions clock. The 2022 

California Regional Haze Plan was not 

submitted to meet any of these 

requirements. Therefore, if finalized, 

these disapprovals would not trigger 

any offset or highway sanctions clocks. 

Disapproving a SIP submission also 

establishes a two-year deadline for the 

EPA to promulgate a FIP to address the 

relevant requirements under CAA 

section 110(c), unless the EPA approves 

a subsequent SIP submission that meets 

these requirements. 

VI. Statutory and Executive Order 

Reviews 

Under the CAA, the Administrator is 

required to approve a SIP submission 

that complies with the provisions of the 

Act and applicable Federal 

regulations.179 Thus, in reviewing SIP 

submissions, the EPA’s role is to review 

state choices, and approve those choices 

if they meet the minimum criteria of the 

Act. Accordingly, this proposed 

rulemaking proposes to partially 

approve and partially disapprove state 

law as meeting Federal requirements 

and does not impose additional 

requirements beyond those imposed by 

state law. 

Additional information about these 

statutes and Executive Orders can be 

found at https://www.epa.gov/lawsregulations/laws-and-executive-orders. 

A. Executive Order 12866: Regulatory 

Planning and Review and Executive 

Order 13563: Improving Regulation and 

Regulatory Review 

This action is not a significant 

regulatory action and was therefore not 

submitted to the Office of Management 

and Budget (OMB) for review. 

B. Paperwork Reduction Act (PRA) 

This action does not impose an 

information collection burden under the 

PRA because this action does not 

impose additional requirements beyond 

those imposed by state law. 

C. Regulatory Flexibility Act (RFA) 

I certify that this action will not have 

a significant economic impact on a 

substantial number of small entities 

under the RFA. This action will not 

impose any requirements on small 

entities beyond those imposed by state 

law. 

D. Unfunded Mandates Reform Act 

(UMRA) 

This action does not contain any 

unfunded mandate as described in 

UMRA, 2 U.S.C. 1531–1538, and does 

not significantly or uniquely affect small 

governments. This action does not 

impose additional requirements beyond 

those imposed by state law. 

Accordingly, no additional costs to 

state, local, or Tribal governments, or to 

the private sector, will result from this 

action. 

E. Executive Order 13132: Federalism 

This action does not have federalism 

implications. It will not have substantial 

direct effects on the states, on the 

relationship between the national 

government and the states, or on the 

distribution of power and 

responsibilities among the various 

levels of government. 

F. Executive Order 13175: Coordination 

With Indian Tribal Governments 

This action does not have Tribal 

implications, as specified in Executive 

Order 13175, because the SIP is not 

approved to apply on any Indian 

reservation land or in any other area 

where the EPA or an Indian Tribe has 

demonstrated that a Tribe has 

jurisdiction, and will not impose 

substantial direct costs on Tribal 

governments or preempt Tribal law. 

Thus, Executive Order 13175 does not 

apply to this action. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

The EPA interprets Executive Order 

13045 as applying only to those 

regulatory actions that concern 

environmental health or safety risks that 

the EPA has reason to believe may 

disproportionately affect children, per 

the definition of ‘‘covered regulatory 

action’’ in section 2–202 of the 

Executive Order. Therefore, this action 

is not subject to Executive Order 13045 

because it merely proposes to partially 

approve and partially disapprove state 

law as meeting Federal requirements. 

Furthermore, the EPA’s Policy on 

Children’s Health does not apply to this 

action. 

H. Executive Order 13211: Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use 

This action is not subject to Executive 

Order 13211, because it is not a 

significant regulatory action under 

Executive Order 12866. 

I. National Technology Transfer and 

Advancement Act (NTTAA) 

Section 12(d) of the NTTAA directs 

the EPA to use voluntary consensus 

standards in its regulatory activities 

unless to do so would be inconsistent 

with applicable law or otherwise 

impractical. The EPA believes that this 

action is not subject to the requirements 

of section 12(d) of the NTTAA because 

application of those requirements would 

be inconsistent with the CAA. 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 89, No. 244 / Thursday, December 19, 2024 / Proposed Rules 103761 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Population 

Executive Order 12898 (Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations, 59 FR 7629, 

Feb. 16, 1994) directs Federal agencies 

to identify and address 

‘‘disproportionately high and adverse 

human health or environmental effects’’ 

of their actions on minority populations 

and low-income populations to the 

greatest extent practicable and 

permitted by law. Executive Order 

14096 (Revitalizing Our Nation’s 

Commitment to Environmental Justice 

for All, 88 FR 25251, April 26, 2023) 

builds on and supplements E.O. 12898 

and defines EJ as, among other things, 

‘‘the just treatment and meaningful 

involvement of all people, regardless of 

income, race, color, national origin, or 

Tribal affiliation, or disability in agency 

decision-making and other Federal 

activities that affect human health and 

the environment.’’ 

The State did not evaluate EJ 

considerations as part of its SIP 

submittal; the CAA and applicable 

implementing regulations neither 

prohibit nor require such an evaluation. 

The EPA did not perform an EJ analysis 

and did not consider EJ in this action. 

Due to the nature of the action being 

taken here, if finalized, this action is 

expected to have a neutral to positive 

impact on the air quality of the affected 

area. Consideration of EJ is not required 

as part of this action, and there is no 

information in the record inconsistent 

with the stated goal of E.O. 12898/14096 

of achieving environmental justice for 

communities with EJ concerns. 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Nitrogen dioxide, 

Ozone, Particulate matter, Sulfur oxides. 

Dated: December 10, 2024. 

Martha Guzman Aceves, 

Regional Administrator, Region IX. 

[FR Doc. 2024–29595 Filed 12–18–24; 8:45 am] 

BILLING CODE 6560–50–P 

DEPARTMENT OF THE INTERIOR 

Fish and Wildlife Service 

50 CFR Part 29 

[Docket No. FWS–HQ–NWRS–2022–0106; 

FXRS12610900000–256–FF09R20000] 

RIN 1018–BG78 

National Wildlife Refuge System; 

Biological Integrity, Diversity, and 

Environmental Health 

AGENCY: Fish and Wildlife Service, 

Interior. 

ACTION: Proposed rule; withdrawal. 

SUMMARY: We, the U.S. Fish and 

Wildlife Service (Service), withdraw the 

proposed rule (proposal) published on 

February 2, 2024, that proposed new 

regulations addressing the biological 

integrity, diversity, and environmental 

health (BIDEH) of the National Wildlife 

Refuge System (Refuge System) and 

updates to the existing BIDEH policy. 

The Service has determined that 

withdrawing the proposal is justified 

based on the significant number of 

public comments received, the 

complexity of the substantive comments 

received and the issues involved, as 

well as the requests from the public for 

further opportunities to review and 

engage with the Service on the 

substance of this proposal. With this 

action, the existing BIDEH policy 

remains in effect. 

DATES: The proposed rule that 

published on February 2, 2024 (89 FR 

7345), is withdrawn on December 19, 

2024. 

ADDRESSES: The February 2, 2024, 

proposed rule, proposed updates to the 

existing BIDEH policy, and the 

comments received are available at 

https://www.regulations.gov in Docket 

No. FWS–HQ–NWRS–2022–0106. 

FOR FURTHER INFORMATION CONTACT: 

Katherine Harrigan, (703) 358–2440, 

katherine_harrigan@fws.gov. 

Individuals in the United States who are 

deaf, deafblind, hard of hearing, or have 

a speech disability may dial 711 (TTY, 

TDD, or TeleBraille) to access 

telecommunications relay services. 

Individuals outside the United States 

should use the relay services offered 

within their country to make 

international calls to the point-ofcontact in the United States. 

SUPPLEMENTARY INFORMATION: 

Background 

On February 2, 2024, the Service 

published in the Federal Register (89 

FR 7345) a proposed rule to adopt new 

regulations to ensure that the biological 

integrity, diversity, and environmental 

health (BIDEH) of the Refuge System are 

maintained, and where appropriate, 

restored and enhanced, in accordance 

with the National Wildlife Refuge 

System Improvement Act of 1997 

(Improvement Act; Pub. L. 105–57). In 

addition, the Service proposed updates 

to the existing BIDEH policy, which was 

available for public comment in the 

proposed rule’s docket on https://

www.regulations.gov. These proposed 

regulations and policy revisions were 

intended to support conservation 

throughout the Refuge System in 

response to both longstanding and 

contemporary conservation challenges, 

including the universal and profound 

effects of climate change on refuge 

species and ecosystems. 

The National Wildlife Refuge System 

is the only network of Federal lands and 

waters in the United States dedicated to 

fish and wildlife conservation and, at 

more than 850 million acres, the largest 

system of its kind in the world. The 

National Wildlife Refuge System 

Administration Act of 1966 

(Administration Act; 16 U.S.C. 668dd– 

668ee), as amended by the Improvement 

Act, is the primary statutory authority 

under which the Secretary of the 

Interior, acting through the Service, 

administers the Refuge System. The 

Alaska National Interest Lands 

Conservation Act of 1980 (16 U.S.C. 

3111–3126), the Wilderness Act of 1964 

(16 U.S.C. 1131–1136), and various 

other statutes also provide direction and 

authority for refuge management. The 

implementing regulations for the 

Administration Act are found in title 50 

of the Code of Federal Regulations at 

subchapter C. 

The Improvement Act established the 

mission of the Refuge System to 

administer a national network of lands 

and waters for the conservation, 

management, and where appropriate, 

restoration of fish, wildlife, and plant 

resources and their habitats within the 

United States for the benefit of present 

and future generations of Americans (16 

U.S.C. 668dd(a)(2)). The Improvement 

Act sets forth policy direction, 

management standards, and 

stewardship requirements for 

administering the more than 570 

national wildlife refuges in the Refuge 

System; prioritizing conservation while 

ensuring public access to compatible, 

wildlife-dependent recreational 

opportunities; and ensuring effective 

coordination with adjacent landowners 

and State fish and wildlife agencies. The 

Improvement Act states that each refuge 

must be managed to fulfill both the 

Refuge System mission and the specific 


lotter on DSK11XQN23PROD with PROPOSALS1