102744 Federal Register / Vol. 89, No. 243 / Wednesday, December 18, 2024 / Rules and Regulations 

(kk) Limited Liability Company Krona 

Bank 

(ll) National Standard Bank Joint Stock 

Company 

(mm) New Moscow Bank 

(nn) NK Bank Joint Stock Company 

(oo) Primorsky Territorial Commercial 

Bank Society with Limited Liability 

(pp) Public Joint Stock Commercial 

Bank Derzhava 

(qq) Public Joint Stock Company Bank 

Alexandrovsky 

(rr) Public Joint Stock Company Bank 

Sinara 

(ss) Public Joint Stock Company Finstar 

Bank 

(tt) Public Joint Stock Company 

Metkombank 

(uu) Public Joint Stock Company 

National Bank Trust 

(vv) Public Joint Stock Social 

Commercial Bank of Primorye 

Primsotsbank 

(ww) Rossita Bank 

(xx) Russian Public Joint Stock 

Commercial Roads Bank 

(yy) Russian Universal Bank 

(zz) Vitabank PJSC 

(aaa) Waybank JSC 

OFFICE OF FOREIGN ASSETS 

CONTROL 

Russian Harmful Foreign Activities 

Sanctions Regulations 31 CFR Part 587 

GENERAL LICENSE NO. 114 

Authorizing Certain Transactions 

Related to Debt or Equity of, or 

Derivative Contracts Involving, Certain 

Entities Blocked on November 21, 2024 

(a) Except as provided in paragraphs 

(d) and (e) of this general license, all 

transactions prohibited by Executive 

Order (E.O.) 14024 that are ordinarily 

incident and necessary to the 

divestment or transfer, or the facilitation 

of the divestment or transfer, of debt or 

equity issued or guaranteed by the 

following blocked entities (‘‘Covered 

Debt or Equity’’) to a non-U.S. person 

are authorized through 12:01 a.m. 

eastern standard time, December 20, 

2024: 

(1) Gazprombank Joint Stock 

Company; 

(2) Interstate Bank; or 

(3) Any entity in which one or more 

of the above persons own, directly or 

indirectly, individually or in the 

aggregate, a 50 percent or greater 

interest. 

(b) Except as provided in paragraph 

(e) of this general license, all 

transactions prohibited by E.O. 14024 

that are ordinarily incident and 

necessary to facilitating, clearing, and 

settling trades of Covered Debt or Equity 

that were placed prior to 4:00 p.m. 

eastern standard time, November 21, 

2024 are authorized through 12:01 a.m. 

eastern standard time, December 20, 

2024. 

(c) Except as provided in paragraph 

(e) of this general license, all 

transactions prohibited by E.O. 14024 

that are ordinarily incident and 

necessary to the wind down of 

derivative contracts entered into prior to 

4:00 p.m. eastern standard time, 

November 21, 2024 that (i) include a 

blocked person described in paragraph 

(a) of this general license as a 

counterparty or (ii) are linked to 

Covered Debt or Equity are authorized 

through 12:01 a.m. eastern standard 

time, December 20, 2024, provided that 

any payments to a blocked person are 

made into a blocked account in 

accordance with the Russian Harmful 

Foreign Activities Sanctions 

Regulations, 31 CFR part 587 (RuHSR). 

(d) Paragraph (a) of this general 

license does not authorize: 

(1) U.S. persons to sell, or to facilitate 

the sale of, Covered Debt or Equity to, 

directly or indirectly, any person whose 

property and interests in property are 

blocked; or 

(2) U.S. persons to purchase or invest 

in, or to facilitate the purchase of or 

investment in, directly or indirectly, 

Covered Debt or Equity, other than 

purchases of or investments in Covered 

Debt or Equity ordinarily incident and 

necessary to the divestment or transfer 

of Covered Debt or Equity as described 

in paragraph (a) of this general license. 

(e) This general license does not 

authorize: 

(1) Any transactions prohibited by 

Directive 2 under E.O. 14024, 

Prohibitions Related to Correspondent 

or Payable-Through Accounts and 

Processing of Transactions Involving 

Certain Foreign Financial Institutions; 

(2) Any transactions prohibited by 

Directive 4 under E.O. 14024, 

Prohibitions Related to Transactions 

Involving the Central Bank of the 

Russian Federation, the National 

Wealth Fund of the Russian Federation, 

and the Ministry of Finance of the 

Russian Federation; or 

(3) Any transactions otherwise 

prohibited by the RuHSR, including 

transactions involving any person 

blocked pursuant to the RuHSR other 

than the blocked persons described in 

paragraph (a) of this general license, 

unless separately authorized. 

Lisa M. Palluconi, 

Acting Director, Office of Foreign Assets 

Control 

Dated: November 21, 2024 

Lisa M. Palluconi, 

Acting Director, Office of Foreign Assets 

Control. 

[FR Doc. 2024–29676 Filed 12–17–24; 8:45 am] 

BILLING CODE 4810–AL–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R09–OAR–2024–0005; FRL–11919– 

02–R9] 

Partial Approval and Disapproval of Air 

Quality Implementation Plans; Arizona; 

Regional Haze State Implementation 

Plan for the Second Implementation 

Period and Prong 4 (Visibility) for the 

2015 Ozone and 2012 Particulate 

Matter Standards 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Final rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is partially approving and 

partially disapproving the regional haze 

state implementation plan (SIP) revision 

submitted by Arizona on August 15, 

2022 (‘‘2022 Arizona Regional Haze 

Plan’’), under the Clean Air Act (CAA) 

and the EPA’s Regional Haze Rule 

(RHR) for the program’s second 

implementation period. Arizona’s SIP 

submission was developed to address 

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. Within this action, the 

EPA is also disapproving the visibility 

transport prong of Arizona’s 

infrastructure SIP submittals for the 

2012 annual fine particulate matter 

(PM2.5) and 2015 ozone National 

Ambient Air Quality Standards 

(NAAQS). The EPA is taking this action 

pursuant to CAA sections 110 and 

169A. 

DATES: This rule is effective on January 

17, 2025. 

ADDRESSES: The EPA has established a 

docket for this action under Docket ID 

No. EPA–R09–OAR–2024–0005. All 

documents in the docket are listed on 

the https://www.regulations.gov 

website. Although listed in the index, 

some information is not publicly 


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Federal Register / Vol. 89, No. 243 / Wednesday, December 18, 2024 / Rules and Regulations 102745 

1Letter dated August 15, 2022, from Daniel 

Czecholinski, Director, Arizona Department of 

Environmental Quality Air Quality Division, to 

Martha Guzman, Regional Administrator, EPA 

Region IX (submitted electronically August 15, 

2022). On August 16, 2022, the EPA determined 

that the SIP submittal met the completeness criteria 

outlined in 40 CFR part 51, Appendix V. Letter 

dated August 16, 2022, from Elizabeth Adams, 

Director, Air and Radiation Division, EPA Region 

IX, to Daniel Czecholinski, Director, Arizona 

Department of Environmental Quality Air Quality 

Division. 

2Letter dated August 21, 2023, from Daniel 

Czecholinski, Director, Arizona Department of 

Environmental Quality Air Quality Division, to 

Martha Guzman, Regional Administrator, EPA 

Region IX (submitted electronically August 25, 

2023). 

3 89 FR 47398. 

4Letter dated December 11, 2015, from Eric 

Massey, Director, Air Quality Division, ADEQ, to 

Jared Blumenfeld, Regional Administrator, EPA 

Region IX. 

5Letter dated September 24, 2018, from Timothy 

S. Franquist, Director, Air Quality Division, ADEQ, 

to Michael Stoker, Regional Administrator, EPA 

Region IX (submitted electronically September 24, 

2018). 

6 89 FR 53372. 

7Available at https://www.regulations.gov/ 

comment/EPA-R09-OAR-2024-0005-0014. 

8Available at https://www.regulations.gov/ 

comment/EPA-R09-OAR-2024-0005-0015 and 

https://www.regulations.gov/comment/EPA-R09- 

OAR-2024-0005-0019. 

9Available at https://www.regulations.gov/ 

comment/EPA-R09-OAR-2024-0005-0016. 

10ADEQ submitted its comment letter twice. The 

letter is available at both https://

www.regulations.gov/comment/EPA-R09-OAR2024-0005-0017 and https://www.regulations.gov/ 

comment/EPA-R09-OAR-2024-0005-0018. 

11Available at https://www.regulations.gov/ 

comment/EPA-R09-OAR-2024-0005-0020. 

12Available at https://www.regulations.gov/ 

comment/EPA-R09-OAR-2024-0005-0021. 

13Available at https://www.regulations.gov/ 

comment/EPA-R09-OAR-2024-0005-0023. 

14Available at https://www.regulations.gov/ 

comment/EPA-R09-OAR-2024-0005-0022. 

15The comment letter and all Exhibits except for 

Exhibits 24 and 60 are available at https://

www.regulations.gov/comment/EPA-R09-OAR2024-0005-0024. Exhibits 24 and 60, including an 

emailed copy of the NPCA et al.’s comment letter, 

are available at https://www.regulations.gov/ 

comment/EPA-R09-OAR-2024-0005-0025. 

available, e.g., Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Certain other material, such as 

copyrighted material, is not placed on 

the internet and will be publicly 

available only in hard copy form. 

Publicly available docket materials are 

available through https://

www.regulations.gov, or please contact 

the person identified in the FOR FURTHER

INFORMATION CONTACT section for 

additional availability information. 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: 

Michael Dorantes, Geographic Strategies 

& Modeling Section (AIR–2–2), Planning 

& Analysis Branch, Air and Radiation 

Division, EPA Region IX, 75 Hawthorne 

Street, San Francisco, CA 94105; phone: 

(415) 972–3934; email: 

dorantes.michael@epa.gov. 

SUPPLEMENTARY INFORMATION: 

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

and ‘‘our’’ refer to the EPA. 

Table of Contents 

I. Background 

A. Regional Haze Plan for the Second 

Implementation Period 

B. Prong 4 (Visibility) of the 2012 PM2.5

NAAQS and 2015 Ozone NAAQS 

Infrastructure SIPs 

II. Public Comments and EPA Responses 

A. Comment Letter From Tri-State 

B. Comment Letter From ADEQ 

C. Comment Letter From the Chamber and 

AMC 

D. Comment Letter From TEP 

E. Comment Letter From SRP 

F. Community Sign-On Letter 

G. Comment Letter From NPCA et al. 

III. Final Action 

IV. Statutory and Executive Order Reviews 

I. Background 

A. Regional Haze Plan for the Second 

Implementation Period 

On August 15, 2022,1 the Arizona 

Department of Environmental Quality 

(ADEQ) submitted the 2022 Arizona 

Regional Haze Plan. ADEQ 

supplemented its SIP revision on 

August 25, 2023, with nonpoint source 

rules (‘‘2023 Arizona Regional Haze 

Rules Supplement’’).2 ADEQ made these 

SIP submissions to address 

requirements of the CAA’s regional haze 

program pursuant to CAA sections 169A 

and 169B and 40 CFR 51.308. 

On May 31, 2024, the EPA published 

a notice of proposed rulemaking 

proposing partial approval and partial 

disapproval of the 2022 Arizona 

Regional Haze Plan SIP submission as 

partially satisfying the regional haze 

requirements for the second 

implementation period contained in the 

CAA and 40 CFR 51.308.3 We did not 

propose to act on the 2023 Arizona 

Regional Haze Rules Supplement. 

The EPA is now approving the 

elements of the 2022 Arizona Regional 

Haze Plan related to requirements 

contained in 40 CFR 51.308(f)(1), (f)(4)– 

(6), and (g)(1)–(5). The EPA is 

disapproving the elements of the 2022 

Arizona Regional Haze Plan related to 

requirements contained in 40 CFR 

51.308(f)(2), (f)(3), and (i)(2)–(4). Our 

proposed action and our responses to 

comments in section II of this document 

contain more information on the basis 

for this rulemaking and on our 

evaluation of the submittal. 

B. Prong 4 (Visibility) of the 2012 PM2.5

NAAQS and 2015 Ozone NAAQS 

Infrastructure SIPs 

Arizona submitted its infrastructure 

SIP submission for the 2012 PM2.5

NAAQS on December 11, 2015 (‘‘2015 

PM2.5 I–SIP submittal’’).4 Arizona also 

submitted its infrastructure SIP 

submission for the 2015 ozone NAAQS 

on September 24, 2018 (‘‘2018 Ozone I– 

SIP submittal’’).5

Our May 31, 2024 proposed 

rulemaking action proposed to 

disapprove the prong 4 portions of 

Arizona’s 2018 Ozone I–SIP submittal 

and 2015 PM2.5 I–SIP submittal. The 

EPA is now disapproving the Prong 4 

elements of Arizona’s 2018 Ozone I–SIP 

submittal and 2015 PM2.5 I–SIP 

submittal. Our proposed action contains 

more information on the basis for this 

rulemaking and on our evaluation of the 

submittals. 

II. Public Comments and EPA 

Responses 

The EPA’s May 31, 2024 proposed 

rulemaking action provided a 30-day 

public comment period that would have 

ended on July 1, 2024. We received four 

comments requesting an extension of 

the comment period. On June 26, 2024,6

the EPA extended the comment period 

for the proposed rulemaking action by 

14 days in response to requests from 

commenters. This action extended the 

close of the comment period to July 15, 

2024. 

The EPA received an additional ten 

unique comments, including one 

anonymous comment,7 two comments 

from private individuals,8 and comment 

letters from Tri-State Generation and 

Transmission Association, Inc. (‘‘TriState’’),9 ADEQ,10 the Arizona Chamber 

of Commerce and Industry and the 

Arizona Manufacturers Council (‘‘the 

Chamber and AMC’’),11 Tuscon Electric 

Power (TEP),12 the Salt River 

Agricultural Improvement and Power 

District (SRP),13 12 community 

organizations (‘‘Community Sign-on 

Letter’’),14 and Earthjustice on behalf of 

the National Parks Conservation 

Association, Sierra Club, and the 

Coalition to Protect America’s National 

Parks (‘‘NPCA et al.’’).15 The 

anonymous comment and the comments 

from the private individuals were 

unrelated to our proposed rulemaking. 

These three comments do not require a 

response. We respond to the issues 

raised in the seven remaining comment 


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16 89 FR 47398, 47428–47432. 

17 Id. 

18 Id. at 47432–47433 and 47435–47436. 

19See CAA section 110(k)(3) (‘‘the Administrator 

shall approve [a SIP] submittal as a whole if it 

meets all of the applicable requirements of [the 

CAA]. If a portion of the plan revision meets all the 

applicable requirements of [the CAA], the 

Administrator may approve the plan revision in 

part and disapprove the plan revision in part’’). 

20Consistent with their labeling in the Plan, 

Appendix C.1, Table 147, these rationales appear 

under the heading of ‘‘Comments.’’ 

letters received on our proposed 

rulemaking in this action. 

A. Comment Letter From Tri-State 

Sections I (‘‘Introduction’’), II 

(‘‘Background Information on TriState’’), and III (‘‘Tri-State Supports the 

Provisions of the Arizona Department of 

Environmental Quality’s State 

Implementation Plan Submittal for 

which EPA has Proposed Approval’’) of 

Tri-State’s comment letter either 

provide background information or are 

supportive of the EPA’s proposal and 

therefore do not require a response in 

our final action. We respond to sections 

IV (‘‘The Partial Disapproval is Overly 

Vague and Should Be Reproposed with 

a Fulsome and Specific Explanation of 

What EPA Finds Inconsistent with the 

Clean Air Act and the Implementing 

Regulations’’), V (‘‘Additional Emission 

Reductions Are Inappropriate for 

Springerville Unit 3’’), and VI (‘‘EPA’s 

Reliance on the July 8, 2021, 

Clarifications Memorandum Is 

Inappropriate Because It Was Issued 

Only Days Prior to the Regional Haze 

State Implementation Plans Being Due’’) 

of Tri-State’s comment letter below. 

Comment A.1. Tri-State comments 

that the proposed rule, specifically the 

partial disapproval, is overly vague and 

does not lend itself to the general public 

being able to adequately understand 

what the EPA finds objectionable 

regarding the SIP submission. Tri-State 

asserts that the EPA made broad 

statements about divergences from the 

Control Cost Manual and inadequacies 

in four-factor analyses and that ‘‘it [is] 

impossible to understand with certainty 

the sources to which these overly broad 

statements apply.’’ The commenter also 

notes that the proposed rulemaking 

action only gives limited examples of 

what the EPA is referring to and asserts 

that the EPA needs to clearly provide 

where it has issues with the SIP revision 

as it was submitted not just examples of 

what it is concerned about. Specifically, 

Tri-State states that the proposed 

rulemaking action makes general 

comments about ADEQ conducting 

analyses for well-controlled sources to 

further reduce emissions but makes no 

reference to which sources that the EPA 

finds to be lacking in this area. Tri-State 

also comments that the vagueness of the 

proposal is not consistent with the 

cooperative nature of the CAA in the 

EPA working with states. 

Response A.1. We do not agree that 

the proposal was overly vague or that 

the basis for our proposed partial 

disapproval was unclear. The proposal 

provided a detailed summary of the 

2022 Arizona Regional Haze Plan and 

the EPA’s evaluation of the Plan with 

regard to each of the applicable 

requirements of the CAA and the RHR. 

With respect to the EPA’s partial 

disapproval specifically, the proposal 

laid out multiple reasons for the EPA’s 

determination that the long-term 

strategy did not fully meet the 

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

related to source selection, four-factor 

analyses (specifically, controlled 

emissions rates and deviations from the 

Control Cost Manual), and control 

determinations (specifically, the 

application of cost thresholds, the use of 

visibility as a factor to avoid controls, 

and the mass-based emissions caps at 

Springerville Generating Station 

(SGS)).16 In each instance, we provided 

at least one example of a unit to which 

this reason applied.17 We also explained 

why the disapproval of the long-term 

strategy also necessitated disapproval of 

the RPG and FLM consultation 

elements.18

We disagree with the commenter’s 

suggestion that it was necessary for the 

EPA to specify the extent to which each 

of the flaws identified by the EPA 

applied to each unit considered by 

ADEQ. The EPA’s role in reviewing SIPs 

is to determine whether they meet all of 

the applicable CAA requirements.19 In 

evaluating whether a SIP revision (or a 

portion thereof) meets all of the 

applicable requirements, the EPA is not 

required to separately evaluate and 

discuss each of the thousands of pieces 

of information, analyses and 

determinations comprising the SIP 

submission. Rather, the EPA may focus 

on those specific elements of the SIP 

revision that form the basis for our 

determination that certain applicable 

requirements are met and certain 

applicable requirements are not met. 

Therefore, in this instance, it was 

reasonable for the EPA to summarize 

our evaluation and cite to examples of 

where the State’s documentation, 

analyses, and determinations did not 

meet CAA requirements, rather than 

separately evaluating and discussing 

every such instance throughout the SIP 

revision. 

For example, regarding source 

selection, our proposal stated that: 

ADEQ did not provide an adequate 

justification for screening out certain sources 

and units from conducting a four-factor 

analysis on the basis that they are ‘effectively 

controlled’ as part of its source selection 

process. Specifically, in some cases, ADEQ 

did not identify the controls for each 

pollutant at each unit or process, the 

associated limits, or where the controls/ 

limits currently exist in the Arizona SIP. In 

other cases, ADEQ listed the controls, but did 

not clearly explain why it is reasonable to 

assume, without conducting a four-factor 

analysis, that no additional controls would 

be reasonable. 

We then provided examples of 

specific sources to which these concerns 

applied. In addition, table 3 of the 

proposal listed all of the units that 

ADEQ screened out as ‘‘effectively 

controlled’’ and includes the entirety of 

ADEQ’s rationale for each unit.20 This 

table clearly shows that for many of the 

units, ADEQ did not list controls for one 

or more of the three relevant pollutants 

(NOX, SO2, and PM). Moreover, even for 

those units where ADEQ did list this 

information, it did not explain why it is 

reasonable to assume, without 

conducting a four-factor analysis, that 

no additional controls would be 

reasonable. Furthermore, our proposed 

rulemaking action clearly stated that 

ADEQ did not adequately explain 

whether any of the existing controls for 

facilities evaluated within the SIP 

submittal were necessary for reasonable 

progress and therefore a part of the 

state’s long-term strategy. Therefore, it 

was not necessary to specifically 

identify each source that was deficient 

in this respect because the deficiency 

applied to every source determined to 

be effectively controlled. 

Finally, regarding the cooperative 

nature of the CAA, we note that the EPA 

worked extensively with ADEQ during 

SIP development. EPA and ADEQ staff 

met on a monthly basis beginning in 

2019 and continuing through 2021 to 

discuss the development of the Plan. 

The EPA also provided informal written 

feedback on various elements of the 

Plan between 2019 and 2022. In these 

communications, the EPA identified 

many of the flaws that are the basis for 

the partial disapproval, so ADEQ was 

aware of the EPA’s concerns prior to the 

EPA’s proposal. 

In conclusion, based on the findings 

discussed in our proposal and 

elsewhere in this document, we find 

that the long-term strategy in the 2022 

Arizona Regional Haze Plan does not 

meet the requirements of 51.308(f)(2) 

and we are disapproving the Plan with 

respect to this requirement. Therefore, 

pursuant to CAA section 110(c), the 

EPA will be required to develop a new 


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Federal Register / Vol. 89, No. 243 / Wednesday, December 18, 2024 / Rules and Regulations 102747 

21 Guidance on Regional Haze State 

Implementation Plans for the Second 

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

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

Standards, Research Triangle Park (August 20, 

2019). 

22 2022 Arizona Regional Haze Plan, p. 219. 

23See CAA 169A(a)(1) ‘‘Congress hereby declares 

as a national goal the prevention of any future, and 

the remedying of any existing, impairment of 

visibility in [Class I areas.]’’ (emphasis added). 

24See 64 FR 35714 (July 1, 1999), 35721–35722 

for additional explanation as to the EPA’s 

determination that emissions from all States 

reasonably contribute to visibility impairment and 

thus are subject to the regional haze regulations. 

Additionally, in the 2017 RHR, the EPA 

‘‘reiterat[ed] that the CAA requires States to 

consider the four statutory factors . . . in each 

implementation period to determine the rate of 

progress towards natural visibility conditions that 

is reasonable for each Class I area.’’ 82 FR 3078 

(January 10, 2017), 3080. 

25 40 CFR 51.308(f)(2)(i). 

26Plan Appendix C, p. 21, Table 1. Q is 

calculated as the total 2018 annual facility-wide 

NOX, SO2, and PM10 emissions in tpy, excluding 

processes determined by ADEQ to be effectively 

controlled. 

27 Id. 

28 79 FR 9318, 9360, Table 50 (February 18, 2014). 

long-term strategy as part of a FIP, 

unless the EPA approves a subsequent 

SIP submission that fully meets these 

requirements. That long-term strategy 

would necessarily include updated 

source selection, four factor analyses, 

and control determinations that address 

the deficiencies we identified in the 

Plan. We are available to work with 

ADEQ following this final action to 

develop a SIP revision, including these 

elements. 

Comment A.2. Tri-State asserted that 

additional emissions reductions are 

‘‘inappropriate’’ for Springerville 

Generating Station (SGS) Unit 3. TriState made a few arguments in support 

of this contention. 

First, Tri-State noted that ADEQ 

evaluated the currently installed NOX

emissions controls against technically 

feasible emissions controls and 

concluded that the current NOX

emissions controls constitutes best 

available control technology (BACT) for 

coal-fired electric generating units 

(EGUs). For SO2, Tri-State indicated that 

ADEQ’s analysis for SGS Unit 3 clearly 

demonstrates that Unit 3’s emissions 

ranged from 0.069 to 0.090 lb/MMBtu 

on an annual basis and has 

continuously complied with the 

Mercury and Air Toxics Standard 

(MATS) SO2 emissions standard of 0.20 

lb/MMBtu, and therefore does not 

warrant further emissions controls. TriState also noted language in the EPA’s 

‘‘Guidance on Regional Haze State 

Implementation Plans for the Second 

Implementation Period’’ (‘‘2019 

Guidance’’) 21 that describes scenarios 

in which the EPA believes it may be 

reasonable for a state not to select a 

particular source for further analysis for 

EGUs that have add-on flue gas 

desulfurization (FGD) and that meets 

the applicable alternative SO2 emissions 

limit of the MATS rule for power plants. 

Second, Tri-State noted the visibility 

improvement at the Mount Baldy 

Wilderness Area in the first planning 

period, and that Arizona will have four 

additional 10-year planning periods to 

achieve the 1.3 deciview improvement 

needed to achieve natural conditions. 

Finally, Tri-State stated that its intent 

is to retire SGS Unit 3 by September 15, 

2031, and requested that the EPA 

include in the final rule a provision to 

allow sources to work with their state 

regulatory agencies to adopt an 

enforceable commitment to retire a unit, 

such as through a permit condition, to 

allow the source to forego any further 

emissions control or reduction 

requirements if a unit is retiring within 

ten years of the Regional Haze SIP 

approval. 

Response A.2. We partially agree with 

this comment. First, with respect to 

NOX emissions at SGS Unit 3, ADEQ 

noted in the Plan ‘‘[t]he current controls 

([low-NOX burners (LNB), overfire air 

(OFA) with selective catalytic reduction 

(SCR)] represent the most effective NOX

control technologies for coal fired EGUs 

and are estimated to achieve 85–95% 

removal efficiency.’’ 22 We agree that the 

existing LNB, OFA and SCR constitute 

effective controls for NOX at SGS Unit 

3. As described in our proposal and in 

response B.1 of this document, existing 

effective controls are generally 

necessary to make reasonable progress 

and must be included in the SIP, unless 

the state provides a weight-of-evidence 

demonstration to justify that the existing 

effective controls are not necessary to 

make reasonable progress. Because the 

Arizona SIP does not include a NOX

emissions limit corresponding to these 

controls for SGS Unit 3, the State should 

have provided such demonstration. 

Specifically, the State should have 

considered whether SGS Unit 3 is 

subject to an enforceable NOX emissions 

limit that ensures its NOX emissions rate 

will not increase. Without proper 

justification that emissions of visibility 

impairing pollutants will not increase, it 

is unclear how reasonable progress is 

being made within the State’s long-term 

strategy for the second planning 

period.23

Similarly, with respect to SO2

emissions at SGS Unit 3, we agree that, 

as described in the 2019 Guidance, an 

add-on FGD meeting the appliable 

alternative SO2 emissions standard 

under MATS may constitute an effective 

control for SO2. However, as noted in 

the previous paragraph, existing 

effective controls are generally 

necessary to make reasonable progress 

and must be included in the SIP, unless 

the state provides a weight-of-evidence 

demonstration to justify that the existing 

effective controls are not necessary to 

make reasonable progress. Because the 

Arizona SIP does not include a SO2

emissions limit corresponding to the 

existing SO2 controls at SGS Unit 3, the 

State should have provided such a 

demonstration, including consideration 

of whether SGS Unit 3 is subject to an 

enforceable SO2 emissions limit that 

ensures its SO2 emissions rate will not 

increase. 

Second, regarding the Mount Baldy 

Wilderness Area, although we commend 

the efforts in Arizona that contributed to 

the noted visibility improvement at the 

Mount Baldy Wilderness Area in the 

first planning period, previous and 

ongoing measures are not automatically 

sufficient to ensure ongoing reasonable 

progress. The regional haze 

requirements of CAA sections 169A and 

169B and 40 CFR 51.308 need to be 

satisfied.24 In particular, the increment 

of progress that is ‘‘reasonable progress’’ 

for a given implementation period is 

determined through the four statutory 

factors.25 While progress made in the 

first implementation period, ongoing 

emissions trends, and anticipated 

changes in emissions may inform a 

state’s regional haze planning process, 

these circumstances alone do not satisfy 

a state’s obligation to determine and 

include in its SIP the measures that are 

necessary to make reasonable progress 

in the second planning period. We also 

note that, while Mount Baldy is the 

closest Class I area to SGS and therefore 

has the highest Q/d (emissions in tons 

per year divided by distance to an 

affected Class I area in kilometers) value 

(339) with respect to SGS,26 this does 

not mean that Mount Baldy is the only 

Class I area affected by emissions from 

SGS. ADEQ did not specifically identify 

all the Class I areas that may be affected 

by emissions from each of the sources 

it evaluated. Nonetheless, given that 

SGS had a 2018 Q of 17,044 tons per 

year (tpy) 27 and is located within 300 

km of 15 different Class I areas,28 it is 

likely to contribute to visibility 

impairment at a number of Class I areas. 

Finally, with respect to Tri-State’s 

request regarding enforceable 

shutdowns, we note that the EPA’s role 

in acting on SIP submittals is to evaluate 

whether they meet applicable CAA 


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29See 2019 Guidance, pp. 20–21 (‘‘It may be more 

challenging for a state to reasonably use a shorter 

remaining useful life as the basis for not selecting 

sources the further away the enforceable shutdown 

date gets from 2028’’). 

30 2021 Clarifications Memo, p. 1. 

31 Id. 

32 2019 Guidance, p. 423. 

33 2021 Clarifications Memo, p. 2. 

requirement, not to establish new 

requirements. Tri-State may choose to 

work with ADEQ to establish 

enforceable shutdowns as part of a 

subsequent SIP revision. However, we 

note that even if there were an 

enforceable shutdown in 2031, this 

would not automatically preclude the 

unit from consideration under a fourfactor analysis.29

Comment A.3. Tri-State comments 

that it was unreasonable for the EPA to 

use the July 8, 2021 ‘‘Clarifications 

Regarding Regional Haze State 

Implementation Plans for the Second 

Implementation Period’’ (‘‘2021 

Clarifications Memo’’) as a basis for 

disapproval of the 2022 Arizona 

Regional Haze Plan. Tri-State indicated 

that although ADEQ submitted its plan 

over a year late on August 22, 2022, 

ADEQ was over three years into the 

process of developing the plan, working 

with the Western Regional Air 

Partnership, the EPA, other states, 

Federal Land Managers (FLMs) and 

members of the public, was nearly 

complete and ready to go through the 

Arizona rulemaking process when the 

EPA published the 2021 Clarifications 

Memo. Tri-State also noted that the 

rulemaking process can take over a year 

due to various tasks required. 

Response A.3. The EPA disagrees that 

it used the 2021 Clarifications Memo as 

a basis for disapproving portions of the 

2022 Arizona Regional Haze Plan. 

Contrary to the commenter’s suggestion, 

the EPA’s guidance, including the 2021 

Clarifications Memo, is not the basis for 

our disapproval. Rather, the partial 

disapproval is based on the Plan’s 

failure to satisfy the requirements of the 

relevant portions of the RHR and CAA 

sections 169A and 169B. We did cite the 

guidance documents because these 

documents provide helpful context 

explaining the EPA’s interpretations of 

the applicable statutory and regulatory 

requirements against which we are 

required to evaluate SIP submittals. 

Commenters are free to disagree and 

raise concerns with those 

interpretations as part of the notice and 

comment process on individual SIP 

actions. However, in this instance, the 

commenter does not appear to object to 

any of the interpretations in the 2021 

Clarifications Memo, only to the fact 

that they were provided shortly before 

the due date for the plans. 

With regard to timing, we note that 

the 2021 Clarifications Memo was 

developed in response to issues that 

EPA regions and other stakeholders had 

raised regarding draft regional haze SIP 

revisions that were already under 

development by states.30 The 2021 

Clarifications Memo therefore 

necessarily came during the SIP 

development process and, in 

comparison to the SIP-specific feedback 

previously provided by the EPA prior to 

its issuance, was intended to ‘‘offer 

feedback more broadly to help support 

SIP development, submittal, review, and 

action for the second planning 

period.’’ 31 With regard to Arizona’s 

Plan specifically, throughout the EPA’s 

collaboration with ADEQ during early 

engagement, EPA staff advised ADEQ of 

many of the interpretations that would 

be expressed in the 2021 Clarifications 

Memo. Therefore, we do not agree that 

it was improper for the EPA to cite to 

the 2021 Clarifications Memo as further 

explanation for why portions of the 

2022 Arizona Regional Haze Plan did 

not comply with the applicable 

statutory and regulatory requirements. 

B. Comment Letter From ADEQ 

Sections I (‘‘Background’’) and XI 

(‘‘Conclusion’’) of ADEQ’s comment 

letter are informational and therefore do 

not require a response. We respond to 

sections II–X of ADEQ’s comment letter 

below. 

Comment B.1. ADEQ asserts that the 

EPA’s changing guidance increased the 

burden of ADEQ’s planning efforts by 

introducing uncertainty and rework. 

ADEQ noted delays between final 

publication of the 2017 RHR and the 

2019 Guidance, as well as later changes 

to the EPA’s interpretation of the RHR 

that came close to the plan submittal 

deadline, including the 2021 

Clarifications Memo. ADEQ asserts that 

the state did not have the resources to 

undertake the evaluation of existing 

control measures, as noted in the 2021 

Clarifications Memo, a process that 

ADEQ states was unreasonably broadreaching and duplicative. 

Response B.1. We disagree with 

ADEQ’s assertions about the EPA’s 

additional guidance increasing the 

burden of ADEQ’s planning efforts by 

introducing uncertainty and rework. 

First and foremost, as stated previously 

and throughout this notice, the EPA did 

not rely on guidance as the basis for its 

partial disapprovals. Rather, the 2019 

Guidance and the 2021 Clarifications 

Memo merely provide additional 

context to the EPA’s interpretations of 

the statutory and regulatory 

requirements. Both the 2019 Guidance 

and the 2021 Clarifications Memo were 

drafted to be used as tools by States in 

the development of their second 

planning period regional haze plans. 

However, neither of these documents 

were necessary for States to develop and 

submit their SIP revisions. 

Regarding the contents of the 

guidance, we do not agree that the EPA 

significantly changed its interpretations 

in either the 2019 Guidance or the 2021 

Clarifications Memo. The commenter 

has not provided any examples of 

interpretations that it believes were 

changed under the 2019 Guidance and 

provided only a single example from the 

2021 Clarifications Memo, relating to 

the section entitled, ‘‘Determining When 

Existing Measures are Necessary for 

Reasonable Progress.’’ We do not agree 

that interpretations set forth in this 

section of the 2021 Clarifications Memo 

represented a significant change in 

interpretation. Rather, they were 

intended to clarify the following 

statement in the 2019 Guidance: 

If a state determines that an in-place 

emission control at a source is a measure that 

is necessary to make reasonable progress and 

there is not already an enforceable emission 

limit corresponding to that control in the SIP, 

the state is required to adopt emission limits 

based on those controls as part of its longterm strategy in the SIP via the regional haze 

second planning period plan submission.32

Many states and other stakeholders 

raised questions about this statement. In 

response, as part of the 2021 

Clarifications Memo, the EPA laid out in 

further detail our interpretation of the 

CAA and RHR regarding how to make 

such a determination. 

We also disagree, on multiple 

grounds, with the commenter’s assertion 

that the ‘‘EPA’s revised guidance 

requires an unreasonably broadreaching review of all existing control 

measures that are not separately 

included in the regional haze plan to 

evaluate whether those same measures 

should be duplicated in the regional 

plan to support reasonable visibility 

progress.’’ 

First, the 2021 Clarifications Memo 

did not establish any new requirements. 

On the contrary, it clearly states that 

‘‘[t]his memorandum does not change or 

substitute for provisions or 

requirements of the CAA or RHR, nor 

does it create any new requirements. 

Rather, this memorandum clarifies and 

provides further information on the 

existing statutory and regulatory 

requirements.’’ 33 One of the key 

requirements of the CAA and RHR is 

that all measures that are necessary to 

make reasonable progress must be 


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34CAA 169A(b)(2); 40 CFR 51.308(f)(2). 

35 2021 Clarifications Memo, pp. 8–9. 

36See 89 FR 47398, 47428 (‘‘ADEQ did not 

provide an adequate justification for screening out 

certain sources and units from conducting a fourfactor analysis on the basis that they are ‘‘effectively 

controlled’’ as part of its source selection process’’) 

and 47431 (‘‘ADEQ has not addressed whether any 

of the existing measures relied upon in its fourfactor analyses or its ‘effective controls’ 

determinations are necessary to make reasonable 

progress and thus should be a part of the State’s 

long-term strategy for the second planning 

period.’’). 

37 89 FR 47398, 47428. 

included the SIP.34 However, neither 

the CAA, the RHR, or the 2019 

Guidance explain how to determine 

whether an existing measure that results 

from a four-factor analysis (or is used as 

the basis to avoid such an analysis) is 

necessary to make reasonable progress. 

Based on questions received on this 

subject during SIP development, it was 

clear that further guidance on this 

question would be helpful. Accordingly, 

the EPA provided this guidance in the 

2021 Clarifications Memo.35

Regarding ‘‘existing measures,’’ the 

Memo explains: 

When the outcome of a four-factor analysis 

is that no new measures are reasonable for a 

source, the source’s existing measures are 

generally needed to prevent future visibility 

impairment (i.e., to prevent future emission 

increases) and thus necessary to make 

reasonable progress. Measures that are 

necessary to make reasonable progress must 

be included in the SIP. 

However, there may be circumstances in 

which a source’s existing measures are not 

necessary to make reasonable progress. 

Specifically, if a state can demonstrate that 

a source will continue to implement its 

existing measures and will not increase its 

emission rate, it may not be necessary to 

require those measures under the regional 

haze program in order to prevent future 

emission increases. 

Similarly, with regard to existing 

‘‘effective controls’’ used to screen out 

sources from a four-factor analysis: 

A decision to forgo a full four-factor 

analysis based on a source’s existing effective 

controls is equivalent to a determination that 

no new measures are necessary to make 

reasonable progress. In this scenario, existing 

effective controls are, therefore, generally 

necessary to make reasonable progress and 

thus must be adopted into the regulatory 

portion of the SIP. However, the state may 

provide a weight-of-evidence demonstration 

as described in Section 4.1 to justify that the 

existing effective control is not necessary for 

reasonable progress. 

Thus, the 2021 Clarifications Memo 

clarifies that, under the CAA and the 

RHR, there is a general presumption that 

existing measures resulting from a fourfactor analysis (or relied upon to avoid 

such an analysis) are necessary to 

prevent future visibility impairment and 

therefore necessary to make reasonable 

progress. Accordingly, states have the 

option to submit all such measures into 

the SIP (to the extent they are not 

already approved into the SIP) without 

further evaluation of whether the 

measures are necessary to make 

reasonable progress. Alternatively, 

states may choose to provide a weightof-evidence demonstration that such 

measures are not necessary to make 

reasonable progress. Importantly, 

however, such a demonstration is 

needed only where an enforceable 

emissions limitation corresponding to 

an existing measure has not already 

been approved into the SIP and is not 

being submitted for SIP approval as part 

of the regional haze plan. Therefore, we 

do not agree that a review of ‘‘all 

existing control measures that are not 

separately included in the regional haze 

plan’’ is required. 

Third, to the extent that a state 

chooses to undertake such a 

demonstration that existing measures 

are not necessary to make reasonable 

progress, we do not agree that it would 

be duplicative. On the contrary, because 

such a demonstration is necessary only 

for measures for which emissions 

limitations are not submitted into the 

SIP, the state and the EPA need to 

evaluate relevant evidence concerning 

whether the source will continue to 

implement its existing measures and 

maintain its emissions rate in the 

absence of SIP-approved requirements 

to do so, to ensure that visibility 

impairment does not increase. 

In sum, we disagree with ADEQ’s 

characterization of the contents of the 

2021 Clarifications Memo and its role in 

our partial approval and partial 

disapproval of the Plan. 

Comment B.2. ADEQ comments that 

the EPA should not issue binding 

decisions based on guidance alone 

where the bases for disapproval are not 

in the rule or statute. ADEQ cites to 

statements in the 2019 Guidance and 

2021 Clarifications Memo regarding 

screening out of effectively controlled 

sources and determinations of whether 

existing controls are necessary to make 

reasonable progress, as the examples of 

guidance. Specifically, ADEQ asserts 

that ‘‘[i]t was unreasonable for the EPA’s 

clarification memo to issue these 

additional specific barriers to a 

determination that existing measures 

were effective at a given source late in 

the development of second round 

regional haze plans through guidance, 

and without additional notice and 

comment.’’ 

Response B.2. We disagree that we 

issued our proposed decision based on 

guidance. Rather, the proposal action 

clearly indicates that the partial 

disapproval was based on failing to 

satisfy the requirements of the relevant 

portions of the RHR and CAA sections 

169A and 169B, with citations to our 

guidance as further explanation. See 

Response A.3 for more explanation. 

We also note that ADEQ’s comment 

appears to conflate two separate 

questions: first, whether its justification 

for screening out a unit based on 

existing effective emissions controls was 

sufficient, and second, whether such 

existing effective control measures are 

necessary to make reasonable progress. 

In our proposal, we discussed each of 

these issues as two separate grounds for 

our proposed partial disapproval with 

respect to 40 CFR 51.308(f)(2).36 While 

both questions apply to sources that are 

screened out from a four-factor analysis 

based on existing effective controls, they 

are distinct. The first issue is further 

addressed in Response B.3 of this 

document, while the second is 

addressed in Response B.1. Therefore, 

we do not agree that the 2021 

Clarifications Memo created any 

additional barriers to a determination 

that existing measures were effective at 

a given source. 

Comment B.3. ADEQ disagreed with 

the EPA’s proposed determination that 

Arizona failed to provide adequate 

justification for deferring certain 

emissions units from consideration. 

ADEQ indicated that the state has the 

flexibility to reasonably select a set of 

sources for an analysis of control 

measures, and that it did not exclude 

entire facilities from consideration or 

exempt sources that had previously 

adopted BART or reasonable progress 

controls, but rather excluded just the 

emissions processes or units that 

recently installed highly effective 

controls from the calculation of the Q/ 

d value for that facility. ADEQ also 

provided additional information 

regarding effective controls in 

Attachment A of its letter. 

Response B.3. We agree that states 

have flexibility to reasonably select a set 

of sources for analysis of controls 

measures. However, as described in our 

proposal, we find that ADEQ’s approach 

to screening out units from conducting 

a four-factor analysis on the basis that 

they are ‘‘effectively controlled’’ was not 

adequately documented.37 Specifically, 

in some cases, ADEQ did not identify 

the controls for each pollutant at each 

unit or process, the associated limits, or 

where the controls and/or limits 

currently exist in the Arizona SIP. In 

other cases, ADEQ listed the controls, 

but did not clearly explain why it is 


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38See 40 CFR 51.308(f)(2)(i) (‘‘. . . The State 

must include in its implementation plan a 

description of the criteria is used to determine 

which sources or groups of sources it evaluated and 

how the four factors were taken into consideration 

in selecting the measures for inclusion in its longterm strategy’’). See also 2021 Clarifications Memo, 

p. 5; 2019 Guidance, p. 23. 

39 2022 Arizona Regional Haze Plan, Appendix C, 

Table 147. 

40See 2019 Guidance, p. 24. 

41Ravi K. Srivastava, Robert E. Hall, Sikander 

Khan, Kevin Culligan & Bruce W. Lani (2005) 

Nitrogen Oxides Emission Control Options for CoalFired Electric Utility Boilers, Journal of the Air & 

Waste Management Association, 55:9, 1367–1388, 

DOI: 10.1080/10473289.2005.10464736. Available 

at: https://doi.org/10.1080/ 

10473289.2005.10464736. 

42Control Cost Manual, Section 4, Chapter 2 

Selective Catalytic Reduction (June 2019), section, 

2.2.1 Reduction Chemistry, Reagents, and Catalyst, 

available at https://www.epa.gov/sites/default/files/ 

2017-12/documents/ 

scrcostmanualchapter7thedition_

2016revisions2017.pdf. 

reasonable to assume, without 

conducting a four-factor analysis, that 

no additional controls would be 

reasonable.38 Accordingly, ADEQ 

should have identified where the 

existing limits are found in the SIP or 

FIP and clearly explained why no 

additional controls would likely be 

reasonable under a four-factor 

reasonable progress analysis for the 

second planning period. Without this 

analysis and explanation, it is not clear 

what is a part of Arizona’s long-term 

strategy for the second planning period. 

As noted in its comment, ADEQ 

conducted its effective controls 

screening on a unit-specific basis. 

However, it did not do so on a 

pollutant-specific basis. Rather, ADEQ 

screened out entire units from further 

evaluation for NOX, SO2, or PM10 if the 

units met ADEQ’s screening criteria for 

any one of these pollutants. We find that 

this approach was unreasonable because 

it resulted in the screening out of entire 

units without consideration of whether 

the unit had effective controls for all 

three of the pollutants covered in 

ADEQ’s long-term strategy. For 

example, ADEQ screened out AEPCO 

Apache Unit 3 and TEP Irvington 

Generating Station (IGS) Unit 4 from 

any further analysis because these units 

were converted from coal to natural gas 

under better-than-BART alternatives 

during the first planning period.39 The 

EPA acknowledges that fuel combustion 

units that are required to combust 

pipeline-quality natural gas are 

generally considered to be effectively 

controlled for SO2 and PM.40 However, 

they are not necessarily effectively 

controlled for NOX, based on burning 

natural gas alone. Therefore, we find 

that ADEQ has not provided adequate 

justification for screening these units 

out from an analysis of NOX controls. 

Additionally, we appreciate the 

documentation in Attachment A that 

ADEQ provided in its attachment letter. 

However, this information would need 

to be part of a SIP revision subject to 

review by the public and FLMs in order 

for the EPA to consider it as part of the 

long-term strategy. If ADEQ develops a 

new SIP revision intended to remedy 

the deficiencies discussed in our 

proposed and final actions on the Plan, 

it may be appropriate to include this 

information in that SIP revision. 

Comment B.4. ADEQ asserts that, 

despite indicating that flawed emissions 

rates were used for some of ADEQ’s 

analyses, the proposed action identified 

one example of differing achievable 

emissions rates for selective catalytic 

reduction (SCR) and selective noncatalytic reduction (SNCR) controls for 

SGS Units 1 and 2’s four factor analyses. 

In this example, ADEQ used 0.060 lb/ 

MMBtu and 0.15 lb/MMBtu as 

reasonable estimates of the achievable 

rates at TEP SGS Units 1 and 2 for SCR 

and SNCR, respectively. 

For SCR, ADEQ additionally states the 

study that the EPA cited for its 

justification that SCR has been 

demonstrated to achieve 0.05 lb/MMBtu 

(or up to 90 percent reduction) was 

published in 2005 and found that the 20 

SCR systems examined in 2003 

achieved NOX emissions rates between 

0.04 and 0.07 lb/MMBtu.41 In addition, 

ADEQ noted that EPA found 0.065 lb/ 

MMBtu as a ‘‘reasonable estimate of 

average SCR performance’’ in its 2016 

Regional Haze FIP action for the Salt 

River Project Coronado Generating 

Station Unit 1. 

For SNCR, ADEQ additionally states 

that the EPA did not provide a technical 

citation for disagreeing with ADEQ’s use 

of 0.15 lb/MMBtu for SNCR. ADEQ 

noted that the proposed rule indicated 

that ADEQ did not demonstrate why 

source specific conditions would cause 

SNCR on these units to achieve as little 

as a 15 percent reduction. ADEQ noted 

that Srivastava et al. found that while 

smaller boilers (e.g., 76–78 MW units) 

were able to achieve greater than 60 

percent NOX reductions, larger boilers 

(e.g., 500 MW units) ‘‘may be capable of 

achieving reductions of only ∼30%.’’ 

ADEQ indicates that SGS Units 1 and 2 

units have nameplate ratings of 425 MW 

and would be expected to achieve less 

reductions than smaller units. ADEQ 

also points to the inlet concentration as 

another consideration for achievable 

emissions rates with post combustion 

emissions control. Citing Srivastava et 

al., ADEQ notes that the study found 

that ‘‘in the absence of reliable SCR inlet 

NOX data, the SCR efficiencies are 

estimated using an inlet NOX level of 

0.5 lb/106 Btu.’’ However, in the case of 

SGS Units 1 and 2, the NOX

concentration in the exhaust from these 

units is less than 100 parts per million 

by volume (ppmv) with an assumed rate 

of 0.174 lb/MMBtu and 0.178 lb/MMBtu 

being used in ADEQ’s four factor 

analysis cost calculations for Unit 1 and 

Unit 2, respectively. Given the already 

low NOX inlet concentration, an 

achievable emissions rate of 0.15 lb/ 

MMBtu was determined to be 

reasonable. ADEQ further noted that 

additional information related to 

achievable emissions rates for SNCR for 

SGS Unit 1 and Unit 2 can be found in 

Appendix K, Section II(J), Comment 10 

of the 2022 Arizona Regional Haze Plan. 

Response B.4. We acknowledge that 

we only highlighted a single example of 

flawed emissions rates in our 

proposal—for NOX at SGS Units 1 and 

2. However, as explained in response 

A.1, in evaluating whether a SIP 

revision (or a portion thereof) meets 

each of these CAA requirements, the 

EPA is not required to separately 

evaluate and discuss each of the 

thousands of pieces of information, 

analyses and determinations comprising 

the SIP submission. Rather, the EPA 

may focus on those specific elements of 

the SIP revision that form the basis for 

our determination that certain 

applicable requirements are met and 

certain applicable requirements are not 

met. In this instance, we focused on 

these units because they are expected to 

have the highest NOX emissions of any 

units in the State (2,099 and 2,283 tpy 

respectively) by 2028, so it is important 

to carefully examine whether additional 

NOX reductions from these units are 

necessary to make reasonable progress. 

Given this context, and for the reasons 

outlined below, we do not agree with 

ADEQ that it has adequately 

documented the emissions rates 

assumed in this analysis, which are a 

critical component of a four-factor 

analysis. 

The emissions rate achievable by a 

unit equipped with SCR is determined 

by several parameters and technological 

limitations. There are periods of 

operation in which the SCR is not able 

to operate, particularly during periods 

of startup and shutdown.42 The SCR 

emissions rate (lb/MMBtu) achievable 

by a particular unit represents the 

combination of two primary elements: 

(1) the controlled NOX emissions rate 

during periods of normal unit operation 

when the SCR is able to operate, and (2) 

the uncontrolled NOX emissions rate 


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43See Docket Item F–16 ‘‘SCR Tangentially fired 

Coal.xlsx.’’ 

44 Id. 

45TEP has indicated that vendors have been 

unwilling to provide manufacturer guarantees of 

0.050 lb/MMBtu over the lifetime of the SCR 

system. Because manufacturer guarantees include 

contractual and financial considerations beyond 

technical performance of the SCR system, we do not 

consider an inability to secure a manufacturer 

guarantee to constitute a determination that an 

emission rate of 0.050 lb/MMBtu is not technically 

feasible, particularly with regard to periods of 

normal operation. 

46See Docket Item F–17 [SGS CAMPD 2021– 

23.xlsx]. To illustrate SCR control potential during 

periods of normal operation, this spreadsheet is 

based on the key assumption that emissions from 

any day a unit did not operate a full 24 hours would 

be attributable to startup/shutdown periods. An 

hourly analysis would provide a more refined and 

precise assessment, though we consider this 

assumption to overestimate the emissions 

attributable to startup/shutdown by including all 

emissions from partial operating days towards 

startup/shutdown. 

47See Docket Item EPA–R09–OAR–2012–0021– 

0204 for cost calculation details. More information 

related to establishing a 30 BOD limit relative to an 

annual emissions rate can be found in our March 

31, 2015 (80 FR 17010) proposed reconsideration, 

including Docket Items EPA–R09–OAR–2015– 

0165–0029 through –0033 for further details. We 

note that SRP identified an SCR design target 

during periods of normal operation as low as 0.03 

lb/MMBtu for Coronado Unit 1, though we 

acknowledge there are source specific differences 

with the SGS units. 

48 It is unclear to what extent a comparable 30– 

BOD limit may be appropriate for the SGS units, but 

we note that the SGS units appear to have 

historically had at least as many startup/shutdown 

events as Coronado Unit 1. 

49See Docket Item F–21, ‘‘SNCR Tangential Coal 

Units.xlsx.’’ 

50See Docket Item F–21. These units include 

Boswell Energy Center (MN) Unit 4, Will County 

(IL) Unit 4, and Jeffrey Energy Center (KS) Units 2 

and 3. 

during periods of startup and shutdown 

when the SCR system cannot operate, 

and result in unit emissions higher than 

the SCR controlled emissions rate that 

increase the unit’s overall emissions 

rate. 

With regard to the first element, the 

2005 study is not the sole basis for our 

finding that an overall emissions rate of 

0.050 lb/MMBtu is achievable with SCR 

on an annual average basis. There are 

multiple instances of coal-fired units 

installing SCR on a retrofit basis and 

achieving 0.050 lb/MMBtu in practice 

on an annual average basis.43 These 

units are typically able to achieve this 

overall level of control by being able to 

operate at NOX annual emissions rates 

at or below 0.050 lb/MMBtu based upon 

periods of normal operation. Even 

several of the units identified by ADEQ 

operating in the annual average 

emissions rate range of 0.055 to 0.065 

lb/MMBtu are still achieving emissions 

rates of 0.050 lb/MMBtu and lower 

based upon periods of normal 

operation.44 We consider this 

information sufficient to establish that 

an 0.050 lb/MMBtu emissions rate 

warrants consideration as technically 

feasible for coal fired units generally 

during periods of normal operation, 

absent source specific factors affecting 

feasibility. We are not aware of 

assertions by either ADEQ or TEP that 

the Springerville units specifically 

cannot achieve 0.050 lb/MMBtu when 

operating with SCR during periods of 

normal operation.45 Therefore, we find 

that ADEQ should have considered a 

controlled NOX emissions rate of 0.050 

lb/MMBtu for SGS Units 1 and 2 when 

operating with SCR during periods of 

normal operation. 

The majority of analysis performed by 

ADEQ is relevant to the second element 

and is intended to support a position 

that, when the annual emissions rate 

achievable during normal operations is 

combined with emissions from the 

number of startup/shutdown cycles 

exhibited by SGS Units 1 and 2, an 

annual average emissions rate of 0.06 lb/ 

MMBtu is what is reasonably achievable 

for these units. We consider it 

appropriate to account for the effect of 

startup/shutdown emissions on the 

emissions rate achievable by the unit, 

but disagree that the analysis provided 

by ADEQ supports an annual average 

emissions rate of 0.060 lb/MMBtu. 

TEP’s four factor analysis and ADEQ’s 

SIP submittal did not include startup/ 

shutdown history to support the 

assertion that Springerville has more 

startup/shutdown events than 

comparable tangentially-fired coal fired 

boilers. A review of Clean Air Markets 

Program Data (CAMPD) emissions and 

operating data over a 2021–2023 

timeframe indicate that SGS Units 1 and 

2 each experienced approximately 9 to 

14 startup events per year. While we 

acknowledge that some portion of SGS 

baseline emissions consist of startup/ 

shutdown emissions that cannot be 

controlled by an SCR system, the 

substantial majority of baseline 

emissions are attributable to emissions 

during normal operation. We estimate 

that approximately 97–98% of baseline 

emissions are attributable to normal 

operations that could be controlled by 

SCR.46 Given that the majority of unit 

emissions can be controlled by SCR to 

0.050 lb/MMBtu or lower and that the 

remaining 2–3 percent of operations are 

characterized by low inlet SCR 

emissions rates, we do not consider the 

historical startup/shutdown operating 

profile to support deviating to an 0.06 

lb/MMBtu emissions rate on an annual 

average basis. 

ADEQ cites a limit of 0.065 lb/MMBtu 

established for SRP Coronado Unit 1 in 

a 2016 Regional Haze FIP action as 

support for the use of an annual average 

emissions rate of 0.060 lb/MMBtu. We 

wish to clarify that the 0.065 lb/MMBtu 

value was not the annual average 

emissions rate used in cost calculations, 

but was the emissions limit established 

on a rolling 30-boiler operating day 

(BOD) average, for Coronado Unit 1. We 

relied upon an 0.050 lb/MMBtu annual 

average emissions rate in developing 

cost calculations for SCR,47 which is 

consistent with our action here. In 

establishing a rolling 30–BOD limit for 

Coronado Unit 1 in that action, we 

acknowledged that upward revisions to 

the SCR design rate achievable on an 

annual average basis would be 

appropriate in order to accommodate 

the effect that multiple startup/ 

shutdown events would have to overall 

unit emissions rates on an averaging 

period that could be as short as 30 days. 

Based upon startup/shutdown 

frequency and projected controlled 

emissions rate information provided by 

SRP, we finalized 0.065 lb/MMBtu as an 

appropriate emissions limit and 

reasonable estimate of SCR performance 

over a short-term period.48 Given that 

the 0.065 lb/MMBtu limit reference here 

corresponds to a different, shorter 

averaging period, and was itself based 

on an 0.05 lb/MMBtu annual average 

emissions rate, we do not consider it 

supportive of an 0.060 lb/MMBtu 

annual average emissions rate. 

For SNCR, we appreciate the 

additional analysis provided in the 

comment and citation to Appendix K 

summarizing ADEQ’s responses to 

public comments. We acknowledge that 

low inlet NOX concentrations are a 

general consideration in evaluating NOX

controls that can negatively impact 

control efficiencies and achievable 

controlled emissions rates. Therefore, in 

order to further evaluate whether a rate 

lower than 0.15 lb/MMBtu may be 

achievable with SNCR at SGS Units 1 

and 2 on an annual basis, we examined 

CAMPD emissions data over a 2019– 

2023 time period for SNCR-equipped 

units comparable to SGS Units 1 and 2, 

specifically filtering for tangentiallyfired coal units operating with SNCR on 

a retrofit basis.49 We identified four 

currently operating SNCR-equipped 

units achieving NOX emissions rates 

below 0.15 lb/MMBtu, ranging between 

0.10 to 0.12 lb/MMBtu.50 These values 

represent the highest performing SNCRequipped units, with the next best 

performing units operating at emissions 

rates of 0.15 lb/MMBtu and higher. At 

least one of the four units we identified 

has the capability to use natural gas, 


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102752 Federal Register / Vol. 89, No. 243 / Wednesday, December 18, 2024 / Rules and Regulations 

51Based on reported natural gas fuel usage, the 

Boswell Energy Center appears to use natural gas 

primarily as a startup fuel, but does periodically use 

quantities of natural gas that suggest co-firing with 

coal for electricity generation purposes. 

52 2022 Arizona Regional Haze Plan, Appendix C, 

Section C3.8.5.2, Page 146. 

53 2022 Arizona Regional Haze Plan, Appendix L, 

Section 4.2.4, Comment 14. 

54 2022 Arizona Regional Haze Plan, Appendix C, 

Section C3.7.6.2, page 129. 

55See, e.g., 2019 Guidance, p. 40. 

56Nat’l Parks Conservation Ass’n v. EPA, 788 

F.3d 1134, 1145 (9th Cir. 2015). 

which could have the effect of lowering 

emissions rates relative to units that do 

not have this capability, such as SGS 

Units 1 and 2.51 Based on the three 

remaining units, each unit had 

relatively low pre-SNCR emissions rates 

that are comparable to SGS Unit 1 and 

2, and each unit is able to achieve SNCR 

emissions rates below 0.15 lb/MMBtu 

and control efficiencies better than 15 

percent. Neither ADEQ or TEP has 

provided documentation to support a 

claim that SGS Units 1 and 2 

specifically cannot achieve an annual 

emissions rate lower than 0.15 lb/ 

MMBtu with SNCR. Therefore, we find 

that ADEQ should have considered a 

NOX emissions rate of lower than 0.15 

lb/MMBtu for SNCR at SGS Units 1 and 

2. 

We also note that this was one of 

multiple flaws that formed the basis of 

our determination that the State’s longterm strategy did not satisfy the 

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

including reasons related to source 

selection and control determinations, as 

detailed in our proposal and elsewhere 

in this document. Therefore, even 

assuming that a control efficiency of 15 

percent for SNCR at SGS Units 1 and 2 

was reasonable, it would not have 

changed our determination that the 

2022 Arizona Regional Haze Plan did 

not satisfy the requirements of 40 CFR 

51.308(f)(2). 

Comment B.5. ADEQ disagrees with 

the EPA’s determination that Arizona 

deviated from the Control Cost Manual 

without documentation as part of its 

four factor analyses with regards to 

remaining useful life calculations for the 

El Paso Natural Gas (EPNG) Williams 

facility and the use of source specific 

interest rates without providing 

adequate documentation in the control 

measure analyses for the EPNG 

Williams and Willcox facilities. 

ADEQ indicates that the EPA Control 

Cost Manual Section 4, Chapter 2, states 

that ‘‘. . . a representative value of the 

equipment life for SCR at power plants 

can be considered as 30 years . . . [f]or 

other sources, the equipment life can be 

between 20 and 30 years.’’ ADEQ noted 

that while it erroneously omitted this 

citation from the EPNG Williams 

Turbine analysis, the Control Cost 

Manual citation and justification for use 

of 25 years is the midpoint between the 

20–30 year range for non-EGU SCR 

systems and was included in the EPNG 

Willcox SCR analysis for Turbines 1 and 

2.52 ADEQ also noted that it received 

cost calculation spreadsheets utilizing a 

25-year useful life for SCR for the EPNG 

Williams Turbine 1 from the US Forest 

Service.53

ADEQ also explains that in its 

analysis of remaining useful life for 

compressor engines at the EPNG 

Williams facility, ADEQ documented 

the assumptions and basis for using 20 

years to amortize NOX controls in 

Appendix C, Section C3.7.6.5, which 

includes citations to the Control Cost 

Manual and the EPA’s 2016 technical 

support document for the Cross State 

Air Pollution Rule for the 2008 Ozone 

NAAQS. 

Response B.5. We appreciate the 

clarification regarding ADEQ’s 

reasoning for use of a 25-year remaining 

useful life for the EPNG Williams 

turbines and 20 years for the EPNG 

Williams engines. While there are 

instances of combustion turbines with 

operating lifetimes beyond 25 years 

(with or without retrofit controls), we 

acknowledge that EPA guidance such as 

the Control Cost Manual has not 

recommended a value beyond the 20–30 

year range. ADEQ’s use of a 25-year 

useful life represents the midpoint of 

Control Cost Manual recommendations, 

and therefore we agree that it is 

consistent with the Control Cost 

Manual. However, we note that the lack 

of documentation of remaining useful 

life for the units at Williams Compressor 

Station was one of the many flaws that 

we identified in the state’s long-term 

strategy including reasons related to 

source selection and control 

determinations, as detailed in our 

proposal and elsewhere in this 

document. Therefore, this clarification 

does not change our determination that 

the 2022 Arizona Regional Haze Plan 

did not satisfy the requirements of 40 

CFR 51.308(f)(2). 

Comment B.6. ADEQ disagrees with 

the EPA’s determination that ADEQ did 

not reasonably weigh the statutory 

factors in reaching its control 

determinations with regards to 

application of cost thresholds. ADEQ 

disagrees that Arizona’s consideration of 

incremental cost effectiveness in its four 

factor analyses were done in an 

unreasonable manner. ADEQ cites to its 

explanation that the incremental cost of 

requiring low-emission combustion 2 

(LEC 2) as opposed to Air-Fuel ratio 

adjustments is $5,034/ton, which ADEQ 

considered reasonable, and therefore 

ADEQ found that LEC 2 is a more 

appropriate control for Williams 

Reciprocating Engine 1 (RECIP–1).54

ADEQ also asserts that it also 

analyzed other determinations from the 

regional haze first implementation 

period besides the incremental cost 

effectiveness value for the Nelson Lime 

Plant action, and ADEQ provides this 

information in Table 1 of its comment 

letter. 

Response B.6. We appreciate ADEQ’s 

explanation about LEC 2 on RECIP–1, 

but we note that ADEQ also rejected 

LEC 3 on Williams RECIP–1, on the 

grounds that the incremental costs of 

these controls, relative to less stringent 

controls, were excessive. In addition, 

ADEQ did not provide or consider 

incremental cost effectiveness values for 

the same controls for the other units at 

the same source (RECIP–2 or RECIP–5). 

Although states may choose to consider 

incremental costs in a reasonable 

manner,55 we find it was unreasonable 

for ADEQ to do so only for specific units 

and controls, rather than in a consistent 

manner across all units and controls. 

Such inconsistent treatment of sources 

without explanation is the ‘‘the 

hallmark of arbitrary action.’’ 56

We also appreciate the addition of 

Table 1 identifying other first 

implementation period incremental cost 

effectiveness decisions. However, this 

information was not included in the 

Plan and therefore not subject to review 

by the public or FLMs. Accordingly, it 

cannot be relied upon to meet the 

requirement of 40 CFR 51.308(f)(2)(iii) 

for States to document the technical 

basis for their long-term strategy. 

Moreover, even if the information had 

been included in the Plan, it would not 

have justified ADEQ’s inconsistent 

consideration of incremental cost 

effectiveness, for the reasons described 

in our proposal and the preceding 

paragraph. 

Comment B.7. ADEQ states that, 

contrary to the EPA’s contention, ADEQ 

did not rely upon visibility benefits for 

its control determinations, but rather 

visibility impacts were reported for 

some sources to give reference to the 

reader as to the relative impact of these 

sources or controls on visibility. ADEQ 

also asserts that nothing in the CAA, 

RHR, or 2019 Guidance prevents the 

department from considering visibility 

benefits as part of its analysis and stated 

that ‘‘the ADEQ’s labeling of the 

visibility benefits associated with 

specific control scenarios as ‘small’ 


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57Citing e.g., ‘‘relatively small visibility benefits’’ 

in 79 FR 52419, 52439 (September 3, 2014). 58 Id., Appendix K, p. 9. 

59Plan, Appendix C, p. 221 (emphases added). 

60 Id. at 234 (‘‘The small visibility benefits 

associated with the modeled SO2 controls supports 

the determination that CDS and wet FGD control 

options are not necessary to make reasonable 

progress towards natural visibility at Class I areas 

during this implementation period.’’). 

61 Id. at 197 (‘‘The small modeled visibility 

benefits associated with additional controls support 

the determination that no additional controls are 

necessary to make reasonable progress towards 

natural visibility at Class I areas during this 

implementation period.’’). 

62 2021 Clarifications Memo, p. 12 (quoting 

Response to Comments on Protection of Visibility: 

Amendments to Requirements for State Plans; 

Proposed Rule at 186). 

63 79 FR 52420, 52439. 

64See, e.g., id. at 52442 (referring to ‘‘large 

visibility benefits) and 52458 (‘‘we consider this 

visibility benefit sufficient to support installation of 

controls.’’). 

65 89 FR 47398, 47430. 

66 89 FR 47398, 47428 (May 31, 2024). 67 79 FR 52420, 52460. 

comports with similar language used by 

the EPA in their regional haze 

actions.’’ 57

Response B.7. We agree with ADEQ 

that in its Response to Comments, 

ADEQ stated that ‘‘[v]isibility impacts 

were reported for some sources to give 

reference to the reader as to the relative 

impact of these sources or controls 

considered on visibility. However, this 

information was not considered in the 

Department’s emissions control measure 

determinations.’’ 58 However, this 

assertion is contradicted by the language 

of some of the control determinations in 

the Plan. For example, in the NOX fourfactor analysis for SGS, ADEQ stated 

that: 

ADEQ does find visibility impacts a useful 

consideration given the goal of the regional 

haze program is to improve visibility in Class 

I areas. As such, ADEQ reports modeled 

visibility impacts in this documentation. The 

small modeled visibility benefits associated 

with the modeled hypothetical NOX emission 

reduction supports the determination that no 

additional NOX controls are necessary to 

make reasonable progress towards natural 

visibility at Class I areas during this 

implementation period.59

Similar language appears following 

the SO2 four factor analysis for SGS 60

and in the summary of ADEQ’s NOX

reasonable progress determination for 

IGS Unit 3.61 This language indicates 

that ADEQ did consider visibility for 

these units, and specifically, that it 

weighed the ‘‘small modeled benefits’’ 

of controls in determining that no 

additional NOX controls were warranted 

at SGS Units 1 and 2 and IGS Unit 3, 

and no more stringent SO2 controls were 

warranted at SGS Units 1 and 2. 

While states have the option to 

consider visibility benefits, along with 

the four statutory factors, in making 

control determinations, if they choose to 

do so, they must do so ‘‘in a reasonable 

way that does not undermine or nullify 

the role of the four statutory factors in 

determining what controls are necessary 

to make reasonable progress.’’ 62 In this 

case, we find it was not reasonable for 

ADEQ to consider visibility benefits 

only for specific sources and without 

any explanation of what would 

constitute a significant visibility benefit. 

In the action cited by ADEQ where 

the EPA considered ‘‘relatively small 

visibility benefits,’’ 63 we were 

comparing the relatively small benefits 

of a control at one source to the 

relatively larger visibility benefits 

expected to result from controls at other 

sources.64 In contrast, in the 2022 

Arizona Regional Haze Plan, ADEQ did 

not find any visibility benefits at any 

source to be anything other than small. 

Thus, as explained in our proposal 

regarding SGS Units 1 and 2, ‘‘[i]n the 

absence of any opportunities for larger 

emissions reductions and corresponding 

visibility benefits, we find that ADEQ’s 

reliance on ‘small’ visibility benefits as 

an additional justification for not 

adopting more stringent controls at 

these units is not persuasive.’’ 65

Finally, we note that, even assuming 

that ADEQ did not consider visibility 

benefits as part of its control 

determinations for SGS Units 1 and 2, 

we would still conclude that the 

determinations were flawed for other 

reasons. In particular, for NOX, ADEQ 

did not adequately justify the control 

efficiency used for SCR and SNCR, as 

discussed in the proposal and response 

B.4.66 For SO2, ADEQ unreasonably 

rejected wet FGD on the basis of 

incremental cost, and set mass-based 

caps that will not ensure 

implementation of the emissions 

reduction measures that are necessary to 

make reasonable progress at these units, 

as discussed in the proposal and 

response B.8. Furthermore, the lack of 

clarity in the Plan regarding whether or 

not ADEQ considered visibility benefits 

in making its control determinations for 

SGS Units 3 and 4 and IGS Unit 3, 

indicates a lack of reasoned decision 

making that also supports our 

disapproval of the Plan’s long-term 

strategy. 

Comment B.8. ADEQ disagrees with 

the EPA’s determination that ADEQ did 

not reasonably weigh the statutory 

factors in reaching its control 

determinations with regards to three 

issues noted in the proposed rule 

concerning the mass-based emissions 

caps at SGS and IGS. 

First, ADEQ asserts that the EPA’s 

rationale is arbitrary and capricious in 

regard to the rejection of wet FGD for 

SGS Units 1 and 2. ADEQ states that the 

use of emissions limits in lieu of 

codifying specific control technologies 

is a flexibility that the EPA itself used 

in its reasonable progress determination 

for Phoenix Cement Clarkdale (PCC).67

ADEQ asserts that the EPA established 

an emissions limit for PCC that did not 

require the installation of a particular 

control technology but rather 

compliance through other means of 

meeting the limit. 

Second, regarding the EPA’s 

contention that spray dry absorber 

(SDA) upgrades may still be cost 

effective after the establishment of the 

mass-based emissions caps, ADEQ 

comments that this manner of analysis 

is not contemplated in the four-factor 

analysis as outlined in the RHR or the 

2019 Guidance. ADEQ asserts that the 

EPA has never applied this standard 

whereby after the establishment of an 

emissions limit based on the reductions 

achievable from a considered control 

technology that a State must revisit and 

update the baseline emissions of its 

four-factor analysis to reflect the new 

emissions limit. ADEQ claims that for 

its analysis of SGS, ADEQ did not select 

a control scenario in its four-factor 

analysis that included the imposition of 

both emissions limits and the 

installation of SDA upgrades, and 

therefore, the EPA should not substitute 

its judgment for ADEQ’s selection of 

SDA upgrades as the evaluated control 

measure for SGS Units 1 and 2 or reject 

ADEQ’s determination based on an 

arbitrary and circular four factor 

analysis standard. 

Third, ADEQ further disagrees with 

the EPA’s assertion that the mass-based 

emissions caps at SGS and IGS would 

not meaningfully constrain the 

emissions from one unit during periods 

when the other unit is not operating and 

argues that the rationale is arbitrary and 

capricious. ADEQ notes that the EPA 

referenced TEP’s 2023 Integrated 

Resources Plan (IRP) and highlighted 

TEP’s plans to retire SGS Unit 1 in 2027, 

but states that as the operating scenarios 

outlined in the IRP are not federally 

enforceable conditions, ADEQ has no 

basis for the consideration of these 

future scenarios as part of its control 

measure analysis and the establishment 

of the mass-based emissions limits. 

ADEQ states that the EPA should not 

rely upon unenforceable and 

hypothetical operating scenarios to 

reject ADEQ’s reasonable progress 

determinations. 

Lastly, ADEQ disagrees with the 

EPA’s rationale that IGS Unit 3’s massVerDate Sep<11>2014 15:22 Dec 17, 2024 Jkt 265001 PO 00000 Frm 00079 Fmt 4700 Sfmt 4700 E:\FR\FM\18DER1.SGM 18DER1

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68 81 FR 46852, 46860 (July 19, 2016). 

69 89 FR 47398, 47402–47403. 

70 89 FR 47398, 47430. 

71 40 CFR 51.308(d)(3) (emphasis added). 

72See 79 FR 9318, 9354 Table 41 (showing 

impacts on Arizona I class I areas). 

73 79 FR 52420, 52468–52469; FIP_RPG_

estimates.xlsx. 

74 2019 Guidance p. 44. 

75 Id. pp. 44–45. 

76 2021 Clarifications Memo, p. 11. 

77Plan Appendix C, p. 232. 

78 79 FR 9318, 9366 (‘‘An annual cap would allow 

SRPMIC to delay installation of controls until the 

Plant’s production returns to pre-recession levels 

and would thus help to address the Community’s 

concerns about the budgetary impacts of control 

requirements.’’) 

based emissions limits are not yet 

enforceable and therefore are not an 

appropriate basis for modifying the 

baseline control scenario for a fourfactor analysis. ADEQ cites that for the 

EPA’s BART determination for Arizona 

Public Service (APS) Cholla generating 

station, the EPA accepted a source 

specific permit revision for APS Cholla 

Unit 2 that included a trigger that was 

conditional on the EPA’s approval of the 

SIP revision that altered the remaining 

useful life of the unit in ADEQ’s four 

factor analysis.68 Therefore, ADEQ 

concludes that the EPA should approve 

ADEQ’s reasonable progress 

determination for IGS Unit 3. 

Response B.8. We disagree with 

ADEQ’s comments arguing that the 

EPA’s justification for disapproving the 

reasonable progress determinations for 

SGS and IGS as it relates to the massbased emissions caps at SGS and IGS 

was improper. 

First, we wish to clarify that we do 

not object to the use of numeric 

emissions limitations as a means to 

implement control determinations. 

Indeed, CAA section 169A(b)(2) 

specifically requires the long-term 

strategy to include ‘‘enforceable 

emissions limitations, compliance 

schedules, and other measures that are 

necessary to make reasonable progress.’’ 

As explained in our proposal: 

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 

emissions reduction measures that a 

particular source or group of sources needs 

to implement to make reasonable progress 

towards the national visibility goal. . . . 

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.69

We find that the mass-based 

emissions caps set for SGS do not 

represent the emissions reduction 

measures that were the outcome of the 

state’s four-factor analysis for the 

reasons described in our proposal 70 and 

herein. Therefore, these caps do not 

meet the requirements of 169A(b)(2) and 

(g)(1), or the corresponding provisions 

of the RHR. 

Regarding PCC, we agree that in the 

EPA’s reasonable progress 

determination for PCC in the first 

implementation period, the EPA 

established a mass-based emissions 

limitation for NOX. However, the 

circumstances between PCC and SGS 

Units 1 and 2 differ in important ways. 

The limit for PCC was set pursuant to 

40 CFR 51.308(d)(3), which required the 

long-term strategy for the first 

implementation period to ‘‘include 

enforceable emissions limitations, 

compliance schedules, and other 

measures as necessary to achieve the 

reasonable progress goals established by 

States having mandatory Class I Federal 

areas.’’ 71 In this instance, the Class I 

areas primarily affected by emissions 

from PCC were in Arizona,72 and the 

emissions reductions from PCC were 

reflected in the applicable RPGs for 

these areas by scaling of visibility 

extinction components in proportion to 

changes in total annual emissions.73

Under these circumstances, an annual 

mass-based emissions limit 

corresponding to the level of annual 

emissions reductions assumed in the 

RPG calculations was sufficient to meet 

the applicable requirement for an 

emissions limit ‘‘as necessary to 

achieve’’ the relevant RPGs. 

In contrast, for the second planning 

period, the EPA clarified in 40 CFR 

51.308(f)(2) that ‘‘the long-term strategy 

must include the enforceable emissions 

limitations, compliance schedules, and 

other measures that are necessary to 

make reasonable progress, as 

determined pursuant to (f)(2)(i) through 

(iv).’’ 40 CFR 51.308(f)(i) in turn 

requires the state to ‘‘evaluate and 

determine the emission reduction 

measures that are necessary to make 

reasonable progress by considering’’ the 

four statutory factors. Thus, the revised 

rule clarifies that the long-term strategy 

must include emissions limitations, 

compliance schedules, and other 

measures representing the emissions 

reduction measures that the state 

determined to be necessary to make 

reasonable progress, considering the 

four statutory factors. 

The EPA provided recommendations 

on the appropriate form of such 

emissions limitations and other 

measures in the 2019 Guidance and the 

Clarifications Memo. Specifically, the 

2019 Guidance recommends the use of 

throughput-based limits, rather than 

mass-based limits (i.e., ‘‘caps’’) for 

emissions limitations to implement 

measures necessary for reasonable 

progress in most instances.74 The 

Guidance notes that mass-based limits 

are allowed under the RHR, but explains 

that, ‘‘[i]f the state has determined, 

independent of the forecasted operating 

level, that operation of the emission 

control equipment . . . is necessary to 

make reasonable progress, a mass-based 

emission limit may not be 

appropriate.’’ 75 The Clarifications 

Memo also reaffirms that ‘‘whether for 

new or existing measures . . . an 

emission limit . . . should be in the 

form of the emission rate achieved when 

implementing those measures (e.g., 

pounds per million British thermal 

units or lbs/MMBtu, pounds per hour or 

lbs/hr, or pounds per ton or lbs/ton of 

produced material).’’ 76

With regard to SGS 1 and 2, ADEQ 

concluded, based on a four-factor 

analysis that, ‘‘it is reasonable to require 

TEP to upgrade the current SDA 

systems’’ 77 and did not indicate that 

this determination was conditioned on 

a particular level of operation. 

Therefore, ADEQ should have set limits 

in the form of the emissions rates 

achieved when implementing SDA 

upgrades, e.g., lb/MMBtu limits, or 

should have provided a rationale for 

why the mass-based limits, which could 

be met without any control upgrades, 

nonetheless represent SDA upgrades. 

We also note that the mass-based limit 

at PCC was for a single unit, meaning 

that it necessarily constrained the 

emissions from that unit on an annual 

basis. In contrast, the mass-based limit 

at SGS Units 1 and 2 were set across two 

units. Accordingly, if one unit ceases to 

operate, the limits would not 

meaningfully constrain emissions from 

the other unit. In addition, ADEQ 

rejected more stringent controls at SGS 

Units 1 and 2 based on its 

‘‘determination that another viable 

reasonable control exists to reduce SO2

emissions from Units 1 & 2 (upgraded 

SDA).’’ In contrast, the EPA did not 

reject any more stringent controls for 

PCC based on incremental cost 

effectiveness. Furthermore, the cap at 

PCC was intended, in part, to address 

concerns raised during consultation 

with the facility’s owner, the Salt River 

Pima Maricopa Indian Community 

(SRPMIC).78 No similar considerations 

exist with respect to SGS Units 1 and 2. 

Therefore, we find that the 

circumstances concerning the PCC 


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79 2022 Arizona Regional Haze Plan, Appendix C, 

p. 236. 

80 89 FR 47398, 47407, Table 1. 

81 77 FR 72511 (December 5, 2012). 

82 89 FR 47398, 47433. 

83 40 CFR 51.308(f)(ii)(A). 

84See Plan p. 106, footnote 112 (citing Plan 

Section 8 and Appendix C). 

85 2022 Arizona Regional Haze Plan, Appendix K. 

mass-based cap are distinguishable from 

those concerning SGS Units 1 and 2. 

Second, regarding our finding that 

SDA upgrades would be cost effective 

after the establishment of the massbased emissions caps, we disagree that 

we substituted our judgment for ADEQ’s 

by arbitrarily rejecting ADEQ’s 

determination based on a circular fourfactor analysis standard. Contrary to 

ADEQ’s suggestion, we did not state that 

ADEQ was required to revisit and 

update the baseline emissions of its 

four-factor analysis to reflect the new 

emissions limitation. However, we note 

that ADEQ did use this approach for IGS 

Unit 3 and determined that with the 

emissions reductions associated with 

the new Unit 3 emissions caps, no 

additional controls are necessary to 

make reasonable progress. ADEQ did 

not provide any rationale for why it 

used this approach for IGS Unit 3, but 

not for SGS Units 1 and 2. 

Furthermore, the fact that the SDA 

upgrades would still be cost effective 

following implementation of the massbased caps at SGS Units 1 and 2 is 

relevant to whether the use of caps (in 

lieu of throughput-based limits) is 

reasonable and appropriate in this 

particular case. The fact that 

throughput-based (e.g., lb/MMBtu) 

limits equivalent to SDA would still be 

cost-effective following implementation 

of the caps (i.e., if TEP complies with 

the caps by lowering its operating level) 

indicates that throughput limits based 

on the emissions rates achievable with 

SDA upgrades may be necessary to 

make reasonable progress, regardless of 

the future operating level. As previously 

noted, the 2019 Guidance explains that, 

under such circumstances, mass-based 

caps are generally not appropriate. 

Therefore, we believe this consideration 

is relevant to the evaluation of whether 

mass-based caps were reasonable and 

consistent with the requirements of the 

RHR in this case. 

Third, we agree with ADEQ’s 

statement that the operating scenarios 

outlined in the IRP are not federally 

enforceable conditions. However, 

ADEQ’s statement in its comment letter 

that it has ‘‘no basis for the 

consideration of these future scenarios 

as part of its control measure analysis 

and the establishment of the mass-based 

emission limits’’ is inconsistent with its 

stated rationale in the Plan for 

establishing caps instead of mass-based 

limits. Specifically, ADEQ stated that: 

As discussed in TEP’s 2020 IRP, Units 1 

will transition to seasonal operation in 2023 

and Unit 2 in 2024. TEP is planning to retire 

Unit 1 in 2027 and Unit 2 in 2032. TEP will 

be very likely to manage its operating level 

strategically instead of completing the 

upgrades to the SDA systems for meeting the 

RP requirements. Therefore, ADEQ 

determines that a mass-based emission limit 

is reasonable.79

In other words, ADEQ elected to 

establish caps specifically because it 

anticipated that TEP could comply with 

these caps by reducing its operating 

level consistent with its then-current 

IRP. Therefore, we do not agree that it 

was inappropriate for the EPA to 

consider information contained in TEP’s 

most recent (2023) IRP in evaluating 

whether the mass-based caps were 

reasonable and consistent with the RHR. 

Lastly, we agree that for APS Cholla 

Unit 2, the EPA accepted a sourcespecific permit revision that included a 

trigger that was conditional on the 

EPA’s approval of the SIP revision that 

altered the remaining useful life of the 

unit in ADEQ’s four factor analysis. 

However, the APS Cholla scenario was 

distinguishable because, as explained in 

the proposed rule,80 the SIP revision for 

APS Cholla replaced the FIP that was 

applicable to these units.81 Therefore, it 

would not have been reasonable to 

subject them to two inconsistent 

requirements, one State and one 

Federal, under the RHR at the same 

time. Thus, under these circumstances it 

was appropriate for ADEQ to make the 

effectiveness of the permit conditions 

contingent on EPA SIP approval. In the 

current case, there is no existing FIP in 

place applicable to IGS Unit 3, so no 

similar rationale exists for making the 

cap contingent upon approval by the 

EPA. 

Comment B.9. ADEQ asserts that the 

EPA should approve ADEQ’s reasonable 

progress goal (RPG) for the Sycamore 

Canyon Wilderness Area. The state 

indicates that it provided the required 

‘‘robust demonstration’’ by including a 

detailed analysis of visibility data at the 

Sycamore site to demonstrate that its 

slower rate of progress results from 

significant increases in light extinction 

from coarse mass. 

Response B.9. As ADEQ notes in its 

comment, its analysis regarding 

Sycamore Canyon focused on the 

substantial increase in coarse mass and 

soil impairment at the Sycamore 

Canyon site. However, as explained in 

our proposal, the rule requires a state 

with a Class I area whose RPG is above 

the glidepath to demonstrate, based on 

the source selection and four factor 

analyses required under 40 CFR 

51.308(f)(2)(i), that there are no 

additional emissions reduction 

measures for sources that may 

reasonably be anticipated to contribute 

to visibility impairment in the Class I 

area that would be reasonable to include 

in the long-term strategy.82 Although 

ADEQ provided a detailed analysis of 

monitoring data concerning Sycamore 

Canyon, it did not provide ‘‘a robust 

demonstration, including documenting 

the criteria used to determine which 

sources or groups or 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.’’ 83 Instead, it relied solely on 

monitoring data and the source 

selection and four-factor analyses 

contained elsewhere in the Plan.84 For 

the reasons described in our proposal 

and elsewhere in this document, we 

find that these analyses were inadequate 

to meet the requirements of 40 CFR 

51.308(f)(2). Therefore, the Plan also did 

not meet the requirements of 40 CFR 

51.308(f)(3)(ii)(A) with respect to 

Sycamore Canyon. 

Comment B.10. ADEQ indicates that 

the State intends to coordinate with 

EPNG to provide supporting 

documentation for the interest rate. 

ADEQ indicates that it intends to 

provide the interest rate documentation 

as confidential business information 

(CBI) to the EPA for review prior to 

publication of the final rule and 

requests that the EPA approve the cost 

calculation for EPNG Willcox and 

Williams based on the site-specific 

interest rate and supporting 

documentation. 

Response B.10. Although ADEQ 

referenced the existence of 

documentation and the possibility of 

sharing it with the EPA in its response 

to comments in the Plan,85 no 

supporting documentation for the 

interest rate was submitted as part of the 

Plan or prior to the close the public 

comment period on the EPA’s proposed 

partial approval and partial disapproval. 

Therefore, the EPA is unable consider 

the interest rate information as part of 

this action. 

Additionally, we note that the lack of 

documentation of EPNG’s firm-specific 

interest rate was one of several flaws 

that we identified in the state’s longterm strategy. Therefore, even if the 

appropriate documentation had been 

submitted and within the proper time 

frame, that alone would not have 

changed our determination that the 


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86CAA Section 307(d)(1). 

87Small Ref. Lead Phase-Down Task Force v. 

EPA, 705 F.2d 506, 518–19 (D.C. Cir. 1983), 

88 Id. at 549. 

89ADEQ SIP Revision: Nonpoint Rules to 

Supplement Arizona’s 2022 Regional Haze SIP, 

‘‘2023 Arizona Regional Haze Rule Supplement,’’ 

August 22, 2023. 

90 Id, at Chapter 4. 

91Sierra Club v. EPA (D.D.C. Case No. 1:23-cv01744–JDB), Consent Decree entered July 12, 2024. 

2022 Arizona Regional Haze Plan did 

not satisfy the long-term strategy 

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

Comment B.11. ADEQ voiced 

procedural concerns with the lack of 

specificity in the EPA’s proposed 

disapproval of the 2022 Arizona 

Regional Haze Plan. ADEQ cites CAA 

307(d)(3) as requiring a detailed notice 

of rulemaking and cites Small Ref. Lead 

Phase-Down Task Force v. EPA, 705 

F.2d 506, 518–19 (D.C. Cir. 1983), for 

the proposition that the notice provided 

in the proposal may be too general to be 

adequate and that ‘‘[a]gency notice must 

describe the range of alternatives being 

considered with reasonable specificity.’’ 

The commenter asserts that the EPA’s 

proposed rule does not provide 

‘‘detailed notice’’ of certain specific 

issues that form the basis for 

disapproval of entire sections of the 

2022 Arizona Regional Haze Plan, 

denying ADEQ the opportunity to 

specifically address those bases for 

disapproval during the comment period. 

Response B.11. We disagree that the 

EPA’s proposal provided inadequate 

notice. The EPA’s action on the 2022 

Arizona Regional Haze Plan is not 

subject to the requirements of CAA 

section 307(d). Those requirements 

apply only to specific enumerated types 

of actions under the CAA and to ‘‘such 

other actions as the Administrator may 

determine.’’ 86 Actions on SIPs are not 

one of the enumerated actions, and the 

Administrator had not determined that 

this action is subject to 307(d) pursuant 

to Section 307(d)(1)(V). Therefore, this 

action is subject to the procedural 

requirements of the Administrative 

Procedure Act (APA). 

Accordingly, pursuant to 5 U.S.C. 

553(b)(2) and (3), the EPA’s notice of 

proposed rulemaking regarding the Plan 

was required to include ‘‘reference to 

the legal authority under which the rule 

is proposed’’ and ‘‘either the terms or 

substance of the proposed rule or a 

description of the subjects and issues 

involved.’’ The proposal clearly met 

these requirements, as it stated the 

applicable legal authorities and 

provided the EPA’s review of the Plan 

in relation to those requirements. The 

comment provides no basis to conclude 

that the proposal failed to meet these 

requirements. Indeed, the opinion cited 

by the commenter contrasts these more 

general APA requirements to the more 

exacting requirements of CAA section 

307(d) concerning the contents of 

proposed rulemaking.87 While we agree 

with the commenter that ‘‘[a]gency 

notice must describe the range of 

alternatives being considered with 

reasonable specificity,’’ 88 we find that 

our proposal met this requirement, as it 

plainly stated that the EPA was 

considering partially approving and 

partially disapproving the 2022 Arizona 

Regional Haze Plan and detailed the 

reason for this proposed action. Please 

also see Responses A.1. 

Comment B.12. ADEQ acknowledges 

that further FLM consultation is 

required for a plan revision that will 

correct the deficiencies identified in the 

proposed rulemaking action, but 

contends that the inclusion of the 

nonpoint source selection analysis and 

selected controls for nonpoint sources 

in the FLM review draft of the plan 

provided FLMs adequate notice and 

review of Arizona’s nonpoint source 

rules that were codified after plan 

submission and submitted in the 2023 

Arizona Regional Haze Rules 

Supplement.89

Response B.12.The EPA disagrees 

with ADEQ’s contention that it provided 

the FLMs with adequate notice and 

review of Arizona’s nonpoint source 

rules. The information about FLM 

consultation regarding the rules 

specifically is not detailed in either the 

2023 Arizona Regional Haze Rules 

Supplement, or the 2022 Arizona 

Regional Haze Plan. The 2023 Arizona 

Regional Haze Rules Supplement 

indicated that further information on 

how this SIP revision complied with 40 

CFR 51.308(i) requirements for federal 

land manager consultation is section 2.4 

of the 2022 Arizona Regional Haze 

Plan.90 However, section 2.4 of the plan 

only describes the FLM review of the 

2022 Arizona Regional Haze Plan, and 

does not specify if ADEQ provided a 

draft of the three nonpoint source rules 

to the FLMs for review. The rules were 

not included in the 2022 Arizona 

Regional Haze Plan. Should Arizona 

choose to submit a SIP revision, 

clarification of the FLM review process 

of the nonpoint source rules that are 

listed in Table 1–1 of the 2023 Arizona 

Regional Haze Rules Supplement would 

be helpful for EPA review. 

C. Comment Letter From the Chamber 

and AMC 

Parts I (‘‘The Chamber and AMC are 

supportive of the goals of the Regional 

Haze Rule’’) and III (‘‘Conclusion’’) of 

the Chamber and AMC’s comment letter 

are informational and therefore do not 

require a response. We respond to part 

II, sections A–E of the Chamber and 

AMC’s comment letter below. 

Comment C.1. The Chamber and AMC 

note that the EPA’s delayed action and 

partial disapproval of Arizona’s 

Regional Haze Plan is an example of 

erosion of cooperative federalism. The 

commenter contends that the timeline of 

events leading up to the EPA’s partial 

disapproval of Arizona’s Regional Haze 

Plan is problematic and that the EPA 

seems to routinely miss statutory 

deadlines, only to get sued by thirdparty entities for failure to act, resulting 

in agreements to deadline extensions 

that delay action for years. In the 

meantime, the resources and analysis 

invested by states depreciate in value, 

often requiring states to reinvest in 

efforts to update an analysis with new 

information. The commenter also 

asserted that ‘‘[r]egularly, an even worse 

scenario plays out in which EPA denies 

a SIP because the information submitted 

in good faith by a state has since become 

dated and stale.’’ 

Response C.1. We do not agree that 

either the timing or substance of the 

EPA’s partial disapproval of Arizona’s 

Regional Haze Plan is an example of the 

erosion of cooperative federalism. We 

acknowledge that the EPA did not act 

on the 2022 Arizona Regional Haze Plan 

within the statutory deadline under 

CAA section 110(k)(3), and that we were 

subsequently sued for failing to meet 

that deadline. This resulted in a courtordered deadline for the EPA to take 

action on the Plan by March 30, 2025.91

However, we do not agree that this 

resulted in a ‘‘deadline extension’’ of 

any sort, or an erosion of cooperative 

federalism. On the contrary, in issuing 

a partial approval and partial 

disapproval of the Plan, the EPA is 

fulfilling our statutorily-mandated role 

to review SIPs for compliance with the 

requirements of the CAA and the RHR, 

as further described in Response D.3. 

We also disagree with the suggestion 

that the EPA is disapproving the 2022 

Arizona Regional Haze Plan, partially or 

entirely because information became 

‘‘dated or stale.’’ The comment did not 

provide examples of information 

becoming dated, resulting in 

disapproval; thus, we cannot comment 

on any specific concerns the commenter 

has with the information within the 

2022 Arizona Regional Haze Plan. 

Further, as explained in Responses 

A.1 EPA staff also discussed with ADEQ 

many of the concerns that became bases 

for our disapproval during the SIP 

development process. 


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92 89 FR 47398, 47428–47429. 

93 89 FR 47398, 47406. 

94See 82 FR 3078,3093 and 3099–3100. 

Comment C.2. The Chamber and AMC 

state that guidance should not be cited 

as grounds to disapprove the 2022 

Arizona Regional Haze Plan. The 

commenter asserts that guidance should 

be viewed only as a reference and not 

a legal requirement to be used to 

approve or disapprove a state’s plan. 

The Chamber and AMC also claim that 

the EPA published final guidance for 

Regional Haze Plans three weeks before 

the plans were due, making compliance 

with the guidance practically 

impossible before the deadline. The 

commenter concludes that relying on 

the guidance to partially disapprove the 

Plan was therefore arbitrary and 

capricious, and the EPA should 

withdraw all of the proposed 

disapprovals based upon the 2021 

Clarifications Memo. 

Response C.2. The EPA disagrees that 

it relied on guidance, including the 

2021 Clarifications Memo, as the basis 

for our partial disapproval. See 

responses A.5, B.1, and B.2. 

Comment C.3. The Chamber and AMC 

assert that Arizona’s source selection 

methodology was reasonable and that 

the EPA should give deference to the 

State on this matter. The commenter 

indicates that sources that applied 

controls in the first round of Regional 

Haze had recently made significant 

investments in the design, engineering, 

procurement, construction and 

operation of those air pollution control 

devices. They note that forcing facilities 

to consider improvement or 

replacement of these air pollution 

control devices long before they have 

depreciated is an unnecessary economic 

burden for the source and the State. The 

Chamber and AMC note that ADEQ 

chose not to force additional analysis 

from these sources and reasonably 

relied upon reductions from other 

emissions sources for visibility 

improvement, a method that resulted in 

all but one of Arizona’s Class I areas 

either meeting or exceeding the uniform 

rate of progress (URP) toward natural 

conditions. 

Response C.3. We disagree that it was 

reasonable for Arizona to screen out 

sources solely because they applied 

controls during the first planning 

period, for the reasons described in 

section IV.E.2.a. of our proposal and in 

response B.3 of this document. 

We also disagree that our disapproval 

will automatically force sources to 

consider improving or replacing any 

recently installed air pollution devices. 

Rather, ADEQ has the option to provide 

additional documentation and 

justification for its effective control 

determinations in a responsive SIP 

revision. We anticipate that for many 

units that recently installed controls, 

ADEQ will be able to provide an 

adequate demonstration of effective 

controls on a unit-specific and 

pollutant-specific basis, if it chooses to 

do so, which would preclude the need 

for a four-factor analysis for those units 

and pollutants. Any affected units and 

pollutants for which ADEQ is unable to 

make such demonstration would be 

subject to the four-factor analysis 

requirement as required by 40 CFR 

51.308(f)(2). 

Finally, we note that all states are 

subject to the requirements at 40 CFR 

51.308(f)(2) and (3) regardless of 

whether the 2028 RPGs for Class I Areas 

they affect are above or below URP. 

Comment C.4. The Chamber and AMC 

assert that the EPA should give 

deference to Arizona’s deviation from 

the EPA Control Cost Manual in 

developing cost estimates. The 

commenter notes that the Cost Control 

Manual is not accurate for all sources 

and cites examples such as variable 

interest and emissions rates. They 

conclude that the use of different 

interest rates and different control 

efficiencies for different projects should 

be viewed as reasonable. 

Response C.4. We do not agree that 

we should have deferred to Arizona’s 

deviation from the EPA Control Cost 

Manual in the absence of adequate 

justification. As discussed in Response 

D.3, Congress charged the EPA with 

independently evaluating and reviewing 

SIP submissions for compliance with 

the applicable requirements under the 

CAA. 40 CFR 51.308(f)(2)(iii) requires 

states 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.’’ 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. For the reasons 

noted in section IV.E.2.b.ii (‘‘Deviations 

from Cost Control Manual’’) of our 

proposed rule, we found that Arizona 

failed to adequately document the 

technical basis that it relied upon to 

determine emissions reduction 

measures, as required by 40 CFR 

51.308(f)(2)(iii). Specifically, as 

explained in our proposal, it is 

important to use consistent methods in 

order to allow for reasoned comparisons 

between different sources within a state, 

and cost analyses in other states.92

Therefore, while our regulations allow 

for flexibility among various 

methodologies, where a state deviates 

from these methods, it should explain 

how its alternative approach is 

reasonable, appropriate, and consistent 

with the regulations and the statutory 

requirement to make reasonable 

progress towards the national goal. 

Arizona did not do so. We therefore 

disagree that the EPA should give 

deference to Arizona’s approach in the 

Plan. 

Comment C.5. The Chamber and AMC 

indicate that Arizona’s plan should be 

viewed in the context that it results in 

all but one monitor having an RPG that 

provides for a greater rate of visibility 

improvement than the adjusted URP. 

The commenter asserts that Arizona has 

created a plan that meets or exceeds the 

URP at all monitors except for Sycamore 

Canyon, which was moved to an 

intersection of two dirt roads in 2014. 

The commenter concludes that the fact 

that visibility at Arizona’s Class I areas 

is improving at a pace to reach natural 

conditions prior to the RHR goal of 2064 

is important context in evaluating the 

source selection methodology and other 

decisions made by Arizona. 

Response C.5. We do not agree with 

the commenter’s characterization of the 

role of the URP. As explained in our 

proposal: 

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.’’ 93

Moreover, being on or below the URP 

does not exempt a state from any of the 

requirements of the CAA or the Regional 

Haze Rule.94

It should also be noted that the URP 

represents the amount of visibility 

improvement that would need to be 

achieved during each implementation 

period to achieve natural visibility 

conditions by the end of 2064. However, 

the 2064 date is used solely to calculate 

the URP as a tracking metric. The CAA 

and RHR do not contain any end dates 

for the regional haze program and do 

not have a ‘‘goal’’ or requirement to 

achieve natural conditions by 2064 

specifically. 

Please also see Response B.9 for more 

information on the robust 


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95 2022 Arizona Regional Haze Plan, Appendix 

C2.2, p. 26. 

96 79 FR 52420, 52422. 

97 89 FR 47481 (June 3, 2024). 

98Specifically, TEP quotes page 3 of the 2021 

Clarifications Memo (‘‘[t]he [Regional Haze Rule] 

does not explicitly list factors that states must or 

may not consider when selecting sources for 

analysis,’’) and cites page 5 of the 2021 

Clarifications Memo as supporting its assertion that 

‘‘EPA has recommended that states consider 

projected and actual emissions in evaluating 

existing emission reduction measures.’’ 

99TEP, Identification and Evaluation of Emission 

Control Measures for Units 3 and 4 at the 

Springerville Generating Station for Purposes of the 

Regional Haze Second Planning Period Under 40 

CFR 51.308(f)(2) (Mar. 2020), available at https://

static.azdeq.gov/aqd/haze/tep_spr_4fa_u34.pdf. 100See 40 CFR 52.145(j)(4). 101See 2019 Guidance, p. 24. 102 89 FR 47398, 47428. 103See 40 CFR 51.308(f)(2)(i) (‘‘. . .The State 

must include in its implementation plan a 

demonstration required for Sycamore 

Canyon under 40 CFR 51.308(f)(3)(ii), 

which is missing from Arizona’s 

submission. 

D. Comment Letter From TEP 

The ‘‘Background’’ section of TEP’s 

comment letter is informational and 

therefore does not require a response. 

We respond to the ‘‘Comments of 

Proposed Disapproval’’ section of TEP’s 

comment letter below. 

Comment D.1. TEP claims that 

ADEQ’s source selection methodology 

was reasonable and the EPA should 

approve the determination. First, TEP 

cites to the 2019 Guidance and 2021 

Clarifications Memo as providing states 

discretion for source selection and notes 

that ADEQ applied a Q/d screening 

threshold of 10 for each process at a 

source. TEP further describes ADEQ’s 

screening out processes where the 

facility recently adopted ‘‘effective 

controls,’’ which the Agency defined as 

controls installed to meet the 

requirements of the PSD program 

(BACT), the first regional haze planning 

period (BART), or other NAAQS 

requirements. Second, TEP further 

suggests that the EPA is proposing to 

approve ‘‘many aspects of ADEQ’s 

source selection process,’’ including 

ADEQ’s choice of screening threshold 

and focus on NOX, SO2, and PM10 in 

evaluating visibility impacts, but 

simultaneously proposing to find that 

the State did not adequately justify its 

determination of effective emissions 

reduction measures. 

Response D.1. First, we disagree with 

the commenter that ADEQ applied a Q/ 

d screening threshold of 10 for each 

process at a source. As noted in the 

2022 Arizona Regional Haze Plan, the Q 

value was calculated from facility-wide 

PM10, NOX, and SO2 annual emissions, 

not process-specific emissions.95

Second, we clarify that the EPA did 

not propose to approve ‘‘many aspects 

of ADEQ’s source selection process.’’ 

We found that ADEQ reasonably and 

adequately explained and documented 

many aspects of its source selection 

process, such as its focus on sulfate, 

nitrate, and coarse mass and its use of 

a Q/d value of 10 for point sources. 

However, we are not separately 

approving or disapproving specific 

elements of ADEQ’s long-term strategy, 

including any elements of the sourceselection process. Rather, we are 

disapproving the long-term strategy as a 

whole under 40 CFR 51.308(f)(2), for the 

reasons described in our proposal and 

in this document. 

Comment D.2. TEP asserts that ADEQ 

reasonably evaluated existing controls at 

IGS Unit 4 and SGS Units 3 and 4. 

First, the commenter states that ADEQ 

did not determine that sources were 

effectively controlled based on BART 

controls alone, but also evaluated 

additional emissions reduction 

measures at several units that were 

controlled during the first regional haze 

planning period, citing Table 8–2 in the 

2022 Arizona Regional Haze Plan. For 

IGS Unit 4 specifically, the commenter 

states that ADEQ evaluated existing 

emissions reduction measures at IGS 

Unit 4 from a source-specific 

perspective, and determined that further 

analysis would be futile. TEP cites to 

statements regarding post-combustion 

controls in the 2019 Guidance and states 

that, in a recent FIP action for Arizona, 

the EPA determined that eliminating 

coal combustion at Unit 4 would control 

emissions beyond the best available 

NOX and SO2 controls.96 TEP concludes 

that these emissions reduction measures 

remain the best available controls at this 

unit in the second planning period. TEP 

further notes that ADEQ’s determination 

that IGS Unit 4 is well-controlled is also 

consistent with recent decreasing 

emissions trends across BART-eligible 

EGUs, including IGS Unit 4, and 

between 2014 and 2019. TEP points to 

the recent proposed rule for Georgia’s 

Regional Haze SIP,97 and comments that 

the EPA cited to similar visibilityimpairing emissions trends as support 

for Georgia’s source-selection 

methodology. Citing to the 2021 

Clarifications Memo,98 TEP also 

indicates that ADEQ was not required to 

consider emissions trends and that the 

State has discretion to emphasize other 

considerations, such as the EPA’s prior 

FIP evaluation. 

Second, TEP states that the EPA’s 

proposed disapproval fails to engage 

with ADEQ’s analysis for SGS Unit 3 

and 4. TEP notes that ADEQ considered 

potential additional control measures 

that could be used to achieve emissions 

reductions at SGS Units 3 and 4 based 

on an initial control analysis submitted 

by TEP.99 In this analysis, TEP provided 

information on technically feasible 

control measures, as well as the actual 

and projected emissions rates at each 

unit. 

Response D.2. We disagree that 

ADEQ’s evaluations regarding effective 

controls at IGS Unit 4 and SGS Units 3 

and 4 were reasonable and justified. 

Contrary to TEP’s claim, ADEQ did not 

evaluate additional emissions reduction 

measures at several units that were 

controlled during the first regional haze 

planning period. Table 8–2 cited by TEP 

to support its claim that ADEQ 

evaluated additional emissions 

reduction measures at units that were 

controlled during the first regional haze 

planning period only depicts annual, 

source-level total emissions of NOX, SO2

and PM10 and does not include any 

information regarding unit-specific or 

pollutant specific emissions rates or 

controls. The commenter also provides 

no citation for its assertion that ADEQ 

evaluated existing emissions reduction 

measures at IGS Unit 4 from a sourcespecific perspective. Therefore, based 

on the contents of the 2022 Arizona 

Regional Haze Plan, it was reasonable 

for the EPA to determine that ADEQ did 

not evaluate additional emissions 

reduction measures at units that were 

controlled during the first regional haze 

planning period. 

Similarly, the commenter’s citation to 

the discussion of post-combustion 

controls in the 2019 Guidance is 

misleading because no such controls 

were installed at IGS Unit 4. Rather, the 

unit was converted from coal to gas as 

part of a ‘‘better-than-BART’’ 

determination pursuant to 40 CFR 

51.308(e)(2).100 Therefore, the actual 

relevant effective controls discussion in 

the 2019 Guidance is the discussion of 

fuel combustion units that are required 

to burn pipeline quality natural gas. 

Such units are generally considered to 

be effectively controlled for SO2 and 

PM.101 However, they are not 

necessarily effectively controlled for 

NOX. Therefore, we disagree with the 

commenter that, given TEP’s recent 

conversion of IGS Unit 4 from coal to 

natural gas, ADEQ’s conclusion that 

further analysis was not required was 

reasonable. As stated in the proposed 

rule,102 ADEQ should have explained 

why it is reasonable to assume, without 

conducting a four-factor analysis, that 

no additional NOX controls would be 

reasonable.103


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description of the criteria is used to determine 

which sources or groups of sources it evaluated and 

how the four factors were taken into consideration 

in selecting the measures for inclusion in its longterm strategy.’’). See also 2021 Clarifications Memo, 

p. 5; 2019 Guidance, p. 23. 

104 89 FR 47481, 47497–47498. 

105 2021 Clarifications Memo, p. 3. 

106 Id. (‘‘Source selection is a critical step in 

states’ analytical processes. All subsequent 

determinations of what constitutes reasonable 

progress flow from states’ initial decisions regarding 

the universe of pollutants and sources they will 

consider for the second planning period.’’) 

107 89 FR 47428. 

108 2021 Clarifications Memo, p. 3. 

109 Id., p. 5 (emphasis added). 

110 2022 Arizona Regional Haze Plan, Appendix 

C, Exhibit CI. 

111 Id., Chapter C3.13. 

112 89 FR 47431. 

113CAA section 110(a)(1), (k)(3), 42 U.S.C. 

7410(a)(1) and (k)(3). 

114CAA section 110(l), 42 U.S.C. 7410(l). 

115CAA sections 110(a)(2)(J), 169A and 169B 42 

U.S.C. 7410(a)(2)(J), 7491 and 7492. 

116Under the CAA, ‘‘applicable implementation 

plan’’ is defined as ‘‘the portion (or portions) of the 

implementation plan, or most recent revision 

thereof, which has been approved under [CAA 

section 110], or promulgated under [CAA section 

110](c) . . . and which implements the relevant 

requirements of [the CAA].’’ CAA section 302(q), 42 

U.S.C. 7602(q). In other words, an ‘‘applicable 

implementation plan’’ is an EPA-approved SIP or 

Tribal Implementation Plan, or an EPApromulgated FIP. 

The commenter’s discussion of 

emissions trends is also misleading on 

several grounds. First, the commenter 

mischaracterizes the EPA’s review of 

Georgia’s regional haze source selection 

methodology. In the section of the 

Georgia proposal cited by TEP, the EPA 

considered trends in total measured 

visibility impairment at three Class I 

areas affected by Georgia’s sources as 

supporting the reasonableness of the 

state’s overall source selection 

methodology.104 The EPA did not, 

however, consider trends in emissions 

from specific sources and did not 

indicate that such trends would be 

relevant either to the reasonableness of 

a state’s overall source selection 

methodology or especially to the 

question of a whether a particular 

source may be screened out on the 

grounds that it is ‘‘effectively 

controlled.’’ Furthermore, the trends 

cited by the commenter were for 

multiple BART-eligible EGUs, not just 

IGS. Therefore, we do not agree that 

decreasing SO2 and NOX emissions at 

BART-eligible EGUs in Arizona between 

2014 and 2019 are relevant to whether 

IGS Unit 4 is effectively controlled. 

Second, the commenter 

mischaracterizes the contents of the 

2021 Clarifications Memo as it relates to 

how to determine whether a source is 

effectively controlled. The first section 

cited by the commenter, regarding 

‘‘Factors to Consider for Source 

Selection’’ 105 relates to a State’s overall 

source selection methodology, which is 

generally considered to be the first step 

of determining what measures are 

necessary for reasonable progress.106

Whether and how to screen out 

particular sources on the grounds that 

they are effectively controlled is a 

subsequent step. As previously noted, 

we found that many aspects of ADEQ’s 

source selection process were 

reasonable and adequately explained 

and documented,107 consistent with the 

statement in the Clarifications Memo 

that, ‘‘whatever choices states make 

should be reasonably explained and 

produce a reasonable outcome.’’ 108

However, once the sources were 

initially selected for evaluation of 

additional control measures, we found 

that ADEQ did not provide an adequate 

justification for subsequently screening 

out certain sources and units from 

ultimately conducting a four-factor 

analysis on the basis that they are 

effectively controlled. 

The second section of the 2021 

Clarifications Memo mischaracterized 

by the commenter, ‘‘Sources that are Not 

Selected Based on Existing Effective 

Controls,’’ does address the screening 

out of particular sources on the grounds 

that they are effectively controlled. In 

particular, this section recommends 

that, ‘‘States should first assess whether 

the source in question already operates 

an ‘effective control’ as described in the 

August 2019 Guidance. They should 

further consider information specific to 

the source, including recent actual and 

projected emission rates, to determine if 

the source could reasonably attain a 

lower rate.’’ 109 For the reasons detailed 

in our proposal and elsewhere in this 

document, we find that ADEQ did not 

reasonably explain and support its 

determination at the first step that IGS 

Unit 4 already operates effective 

controls, particularly for NOX. 

Moreover, even if IGS Unit 4 does have 

effective controls, ADEQ should have 

considered recent actual and projected 

emissions rates for this particular unit, 

not for all BART-eligible units as a 

group, in order to determine whether 

these controls are necessary to make 

reasonable progress. 

Finally, we disagree that our proposed 

disapproval fails to engage with ADEQ’s 

analysis for SGS Unit 3 and 4. Contrary 

to the commenter’s suggestion, ADEQ 

did not screen out SGS Units 3 and 4 

at the source selection stage,110 but 

instead conducted four-factor analyses 

for these units.111 We summarized these 

analyses on pages 47422–47423 of our 

proposal. We did not note any particular 

flaws in these analyses or the resulting 

determinations that no additional 

controls were necessary to make 

reasonable progress in our proposal. 

However, we found that ADEQ had not 

addressed whether any of the existing 

measures relied upon in these fourfactor analyses were necessary to make 

reasonable progress and thus should be 

a part of the State’s long-term strategy 

for the second planning period.112 We 

also noted that, as part of its analysis of 

whether these existing measures are 

necessary to make reasonable progress, 

the State should have considered 

whether the relevant sources are subject 

to enforceable emissions limits that 

ensure their emissions rates will not 

increase. Without this information, it is 

not clear what measures are in the 

State’s long-term strategy for the second 

planning period and how controls on 

these units result in each of the affected 

Class I areas making reasonable progress 

towards the national goal. 

Comment D.3. TEP asserts that ADEQ 

reasonably evaluated additional control 

measures using a four-factor analysis for 

SGS Units 1 and 2. Citing Oklahoma v. 

EPA, 723 F.3d 1201, 1209 (10th Cir. 

2013), the commenter asserts that while 

the statute identifies the factors that 

must be considered, Congress left to 

states the determination as to how these 

factors should be weighed. 

Response D.3. While we agree that 

states have significant discretion in how 

they consider and apply the four 

statutory factors as part of a Regional 

Haze SIP, they do not have unlimited 

discretion. On the contrary, the EPA has 

a crucial role in reviewing such SIP 

submissions for compliance with the 

requirements of the CAA and the RHR. 

Pursuant to CAA section 110, states 

must submit SIP revisions to the EPA 

for review and the EPA must evaluate 

whether each SIP submission meets all 

of the applicable requirements of the 

Act.113 The EPA must disapprove any 

SIP revision that ‘‘would interfere with 

any applicable requirement’’ of the 

Act.114 CAA section 110(a)(2)(J) 

specifically requires that SIPs ‘‘meet the 

applicable requirements’’ of Part C of 

Title I of the CAA including the 

requirements for visibility protection set 

forth in sections 169A and 169B.115

Pursuant to section 169A(b), the EPA is 

required to promulgate visibility 

protection regulations that apply to 

‘‘each applicable implementation plan’’ 

(i.e., each SIP or FIP) 116 for each State 

containing one or more Class I areas and 

each State ‘‘emissions from which may 

reasonably be anticipated to cause or 

contribute to any impairment of 


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117 42 U.S.C. 7491(b)(2). 

118Arizona ex. rel. Darwin v. EPA, 815 F.3d 519, 

531 (9th Cir. 2016). 

119Oklahoma v. EPA, 723 F.3d 1201, 1209 (10th 

Cir. 2013). 

120 81 FR 296, 310 (January 5, 2016). 

121 89 FR 47494. 

122 89 FR 47429. 

123 2019 Guidance at 38 (citing NPCA v. EPA, 788 

F.3d 1134, 1142–43 (9th Cir. 2015)). 

124 89 FR 47398, 47429. 

125See 2022 Arizona Regional Plan, Appendix K, 

p. 7. 126 79 FR 9318. 

visibility in any [Class I area].’’ The 

CAA specifies that these regulations 

(including the RHR) must require each 

such SIP or FIP to ‘‘contain such 

emission limits, schedules of 

compliance and other measures as may 

be necessary to make reasonable 

progress toward meeting the national 

goal.’’ 117 Thus, the statute provides the 

EPA a key oversight role in reviewing 

SIPs, including regional haze SIPs, and 

the ‘‘EPA has substantive authority to 

assure that a state’s proposals comply 

with the Act, not simply the ministerial 

authority to assure that the state has 

made some determination.’’ 118

Nothing in the Oklahoma case cited 

by the commenter undermines this 

authority. On the contrary, the 

Oklahoma court upheld the EPA’s 

disapproval of BART determinations 

that were part of a regional haze SIP, 

noting BART ‘‘does not differ from other 

parts of the CAA—states have the ability 

to create SIPs, but they are subject to 

EPA review.’’ 119 Likewise, all regional 

haze SIPs are subject to EPA review, as 

described in the preceding paragraph. 

In our action on the Plan, we are 

exercising our substantive authority to 

review the state’s submittal for 

compliance with the applicable 

requirements of the CAA and RHR. 

Based on our review of the Plan, we 

find, among other things, that ADEQ 

had not reasonably evaluated and 

weighed the four statutory factors for 

SGS Units 1 and 2 for the reasons noted 

in section IV.E.2 of our proposal and 

responses B.4., B.6, B.7 and B.8 of this 

document. 

Comment D.4. TEP states that ADEQ’s 

choice of cost-effectiveness threshold 

was reasonable, and that the EPA’s 

proposed rule did not afford appropriate 

deference to ADEQ’s assessment of 

reasonable cost-effectiveness values. 

TEP also cites a previous EPA action 

stating that ‘‘Congress did not provide 

any direction as to how states should 

consider ‘the costs of compliance’ when 

determining reasonable progress.’’ 120

TEP also provides the following reasons 

for why it believes ADEQ’s choice of 

cost-effectiveness threshold was 

reasonable. 

First, TEP states that ADEQ selected 

a threshold based on the State’s 

evaluation of the highest cost controls 

during the first planning period. TEP 

notes that this threshold is nearly 

$1,000/ton higher than the 98th 

percentile value for EGU boilers during 

the first planning period and $1,500/ton 

higher than costs rejected by Georgia in 

evaluating additional emissions 

reduction measures in its SIP 

submission.121

Second, TEP claims that ADEQ’s 

bright-line approach to analyzing 

available controls above its costeffectiveness threshold was also 

reasonable. TEP disagrees with the 

EPA’s concern about the average cost of 

installing SNCR at SGS Unit 2 being 

$269/ton above ADEQ’s $6,500/ton 

threshold.122 TEP states that the 2019 

Guidance emphasized that the RHR 

does not prevent states from 

implementing ‘‘bright line’’ costeffectiveness thresholds when 

considering additional control 

measures, consistent with the Ninth 

Circuit’s decision in NPCA v. EPA.123

TEP asserts that this threshold sets an 

amount above which a state would 

reject control options as too expensive, 

and that for controls falling below this 

threshold, it is reasonable for ADEQ to 

evaluate additional factors, such as 

incremental costs, visibility impacts, 

and the other statutory factors, in 

determining whether these controls are 

necessary for reasonable progress. 

Response D.4. As TEP describes, the 

EPA noted in prior rulemakings that 

‘‘Congress did not provide any direction 

as to how states should consider ‘the 

costs of compliance’ when determining 

reasonable progress.’’ However, 

consistent with our prescribed statutory 

role, as described in Response D.3, the 

EPA is required to evaluate whether 

each State exercised its flexibility and 

conducted the required analyses in a 

reasonable way and in accordance with 

the applicable requirements. As 

described throughout our proposal and 

this final action, we determined that 

Arizona did not do so. 

For example, contrary to TEP’s claim, 

the EPA did not find that ADEQ’s 

average cost-effectiveness thresholds of 

$6,500/ton for point sources and $5,000/ 

ton for nonpoint sources were 

unreasonable. Rather, as explained in 

our proposal, we found that the State 

inconsistently and unreasonably 

applied these cost thresholds to the 

control determinations.124

In particular, we found that ADEQ 

incorrectly characterized its average cost 

effectiveness threshold for points 

sources as a bright-line threshold,125

given that ADEQ, in fact, rejected 

controls that were below this threshold. 

In these instances, ADEQ relied on 

incremental cost effectiveness as a basis 

to find the cost of control excessive, but, 

again, did not do so consistently, as 

described in Response B.6 of this 

document. Thus, ADEQ did not 

consistently apply either its chosen 

average cost effectiveness threshold or 

any defined incremental cost 

effectiveness threshold as a basis to 

choose whether to adopt or reject 

control measures, nor did it explain its 

reasoning for these inconsistencies. The 

EPA finds this to be unreasonable. 

Based on this and other flaws in the 

long-term strategy described in the 

proposal and elsewhere in this 

document, we find that the long-term 

strategy in the Plan did not meet the 

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

We also note that, while our proposed 

rule recommended that ADEQ revisit 

control determinations with controls 

that were slightly above the cost 

thresholds, given the flaws in the costeffectiveness analyses, we did not 

indicate that, in the absence of such 

flaws, use of a bright line threshold 

would have been improper, as long it 

was appropriately justified and 

consistently applied. Finally, we note 

that the fact that other states have 

applied lower or similar thresholds does 

not automatically make Arizona’s 

threshold reasonable. 

Comment D.5. TEP states that ADEQ’s 

evaluation of control costs is 

conservative and results in projected 

costs that are lower than what TEP 

would incur. TEP asserts that ADEQ 

selected baseline assumptions 

consistent with the EPA’s Control Cost 

Manual. In particular, TEP indicates 

that ADEQ calculated control costs 

using an assumed interest rate of 4.75 

percent and a maximum equipment life 

of 30 years, but that these assumptions 

resulted in unrealistically low control 

cost estimates. TEP noted that the EPA 

previously used 20-year equipment life 

and 7 percent interest rate for both NOX

and SO2 candidate emissions reduction 

measures for IGS as part of a previous 

regional haze FIP,126 and that these 

assumed values of 7 percent and 20 

years better reflect actual control costs. 

TEP also asserted that ADEQ is not 

required to treat the guidance provided 

by the Control Cost Manual as 

dispositive, and, citing Wyoming v. 

EPA, 78 F.4th 1171, 1180 (10th Cir. 

2023), TEP asserted that the EPA cannot 

treat nonbinding guidelines as 

mandatory in evaluating a SIP 

submission.88


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127Control Cost Manual, Section 4, Chapter 2 

Selective Catalytic Reduction (June 2019), section, 

2.4.2 Total Annual Costs, Indirect costs, available 

at https://www.epa.gov/sites/default/files/2017-12/ 

documents/scrcostmanualchapter7thedition_

2016revisions2017.pdf. 

128 Id. at page 87 of 107 (PDF document 

pagination), (‘‘a representative value of the 

equipment life for SCR at power plants can be 

considered as 30 years’’). 

129 Id., Appendix C, p. 219 (‘‘The estimated life 

for SCR and SNCR were set at 30 and 20 years 

respectively to match current EPA guidance for 

these control technologies on utility boilers.’’) The 

commenter’s citation to page 146 of the Plan 

appears to be in error, as there is no such page in 

the main body of the Plan, and page 146 of 

Appendix C discusses the Willcox compressor 

station. 

130Control Cost Manual, Section 4, Chapters 1 

and 2, available at https://www.epa.gov/economicand-cost-analysis-air-pollution-regulations/costreports-and-guidance-air-pollution. 

131 2022 Arizona Regional Haze Plan, Chapter 

8.3.2. 

132 Id. 

133 89 FR 47398, 47428. 

134 87 FR 31798 (May 25, 2022) and Docket Item 

EPA–R03–OAR–2022–0347–0059 for further 

details. 

135 Docket Items EPA–HQ–OAR–2021–0668–0115 

and EPA–HQ–OAR–2021–0668–0096 examine 

ozone season data from several mid-atlantic states 

and identifies best performing months for several 

units. An examination of operating data on a 

monthly or daily basis over the course of a calendar 

year indicates that several units, such as Pleasants 

Power Station 1 and 2 (WV), Conemaugh 2 (PA), 

and DB Wilson W1 (KY) operate at much lower 

NOX emission rates during ozone season months. 

Response D.5 We do not agree that 

ADEQ’s evaluation of costs was 

conservative and results in projected 

costs that are lower than what TEP 

would incur. Regarding the EPA’s 

previous analyses for IGS, first, we note 

that the EPA has revised several 

chapters of the Control Cost Manual, 

since the 2014 regional haze FIP cited 

by TEP in the comment letter. In 

particular, the chapter concerning SCR 

was updated in 2019.127 As part of that 

update, the remaining useful life for 

SCR was revised from 20 years to 30 

years.128 Consistent with this change, 

ADEQ used a remaining useful life of 30 

years for SCR, but used 20 years for 

SNCR.129

Second, as explained in the Control 

Cost Manual,130 interest rates change 

with time due to changes in prices over 

time for all relevant goods and services 

such as capital equipment, engineering 

services, other materials and reagents 

used in the construction and operation 

of control equipment. In the absence of 

source-specific information, ADEQ 

relied on a 4.75 percent interest rate 

developed by analyzing and averaging 

historical bank prime rate data. ADEQ 

looked at 3-year average bank prime 

rates for the periods of 2017–2019 (4.83 

percent) and April 2018–March 2020 

(4.78 percent). These dates were chosen 

as they were the most recent data at the 

time of the analysis.131 In contrast, 

ADEQ also explained in its SIP 

submittal that the 7 percent interest rate 

from the first planning period FIP cited 

by TEP was the 3-year average bank 

prime rate during 2005–2007.132

Therefore, the 7 percent rate used by the 

EPA in our previous FIP was not 

appropriate for the cost analysis for the 

Plan, which was developed in 2020– 

2022. 

Finally, we disagree with the 

commenter’s suggestion that we treated 

the Control Cost Manual, or any other 

guidance, as binding. As discussed in 

Responses A.3 and C.4, the EPA’s 

citations to guidance documents were 

intended to provide further context on 

what is generally considered to be a 

reasonable approach to fulfill the 

statutory and regulatory requirements. 

We acknowledge that the suggestions in 

those guidance documents are not 

binding, but are generally assumed to be 

reasonable. States can deviate from the 

suggestions within EPA guidance 

documents. However, they must do so 

in a reasonable way, accompanied by 

sufficient justification. The Plan did not 

do so for the reasons described in our 

proposal and elsewhere in this 

document. 

Comment D.6. TEP asserts that 

ADEQ’s analysis of SCR and SNCR 

reasonably approximated emissions 

limits achievable at SGS Units 1 and 2. 

TEP explains that the emissions rate 

used in the analysis was unit-specific, 

and that ADEQ considered baseline 

NOX emissions, inlet concentrations, 

and the frequency of startup/shutdown 

cycles at SGS Units 1 and 2. TEP 

reiterates that ADEQ explained that a 

higher number of startup/shutdown 

cycles results in higher average NOX

emissions rates with SCR, and that SGS 

Units 1 and 2 experience a higher 

frequency of startup/shutdown cycles 

than average EGUs. 

TEP further disagrees that SGS Units 

1 and 2 are able to achieve an emissions 

rate of 0.05 lb/MMBtu. TEP notes that 

ADEQ further explained in its response 

to public comments that it was 

inappropriate to use an annual 

emissions limit of 0.05 lb/MMBtu 

because the CAMPD database only 

contains three comparable units, out of 

fifty-eight units, which are operating 

below this emissions limit in 2019– 

2021. The CAMPD database shows that 

approximately 20% of the units 

achieved emissions below 0.06 lb/ 

MMBtu in 2019–2021, which ADEQ 

believed was a reasonable estimate of 

the rate achievable with SCR for SGS 

Units 1 and 2. TEP also notes that based 

on their extensive industry experience, 

vendors will not guarantee a rate of 0.05 

lb/MMBtu due to concerns about 

degradation over time. 

TEP also states that even if ADEQ 

adopted the EPA’s preferred emissions 

rate of 0.05 lb/MMBtu, ADEQ’s analysis 

of control measures for SGS Units 1 and 

2 would remain substantially the same. 

Table 3 of TEP’s comment letter 

provides the updated cost-effectiveness 

value using a 0.05 lb/MMBtu rate for 

SGS Units 1 and 2, assuming a 4.75 

percent interest rate and a remaining 

useful life of 30 years. 

Response D.6. We do not agree that 

ADEQ’s analysis of SCR and SNCR 

reasonably approximated emissions 

limits achievable at SGS Units 1 and 2. 

Our proposed rule acknowledged the 

startup/shutdown considerations noted 

by ADEQ.133 However, the proposed 

rule also explains that ADEQ has not 

demonstrated why these startup/ 

shutdown considerations would be 

significant enough at SGS Units 1 and 

2 on an annual average basis, which is 

the averaging period used to calculate 

ton/year emissions reductions for cost 

effectiveness calculations, to preclude 

them from achieving this emissions 

reduction level with SCR. As discussed 

in more detail in Response B.4, we 

would consider it appropriate for an 

emissions limitation established on a 

shorter averaging period to have a 

higher value to account for startup/ 

shutdown emissions, which have a 

greater effect on overall unit emissions 

rates over shorter averaging periods. 

We also disagree with TEP that 

ADEQ’s review of emissions rates for 

other tangentially fired coal units in 

CAMPD should be determinative of the 

SCR emissions rate achievable for the 

SGS units. We do not necessarily 

consider the inventory of unit emissions 

data in CAMPD to be representative of 

what is achievable with SCR technology 

because units whose emissions are 

included in CAMPD have been required 

to install SCR as a result of a variety of 

regulatory programs. Not all of these 

programs may have fully considered 

technological factors in establishing 

emissions requirements or allowable 

emissions limits, which would have the 

effect of elevating reported emissions 

rates. For example, several units in the 

eastern U.S. have installed SCR but have 

not been required to operate in a 

manner that fully accounts for periods 

of startup operations,134 while other 

units may only operate their SCR 

systems seasonally.135 Other SCR 

systems may have been required by a 

Consent Decree, which involves a 


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136 77 FR 61478 (October 9, 2012). 

137 79 FR 52420. 

138 89 FR 47398, 47430–47431. 

139 Id. 

140A limit based on boiler operating days would 

effectively exclude days with zero emissions from 

the calculation of the 30-day average whereas a 

limit based on calendar days does not. 

141Plan, appendix C, p. 213, Table 83. 

142Emissions information can be publicly 

accessed through the EPA Clean Air Markets 

Program data, available at https://campd.epa.gov/. 

143As part of its preferred alternative in its 2023 

Integrated Resources Plan, p. 56, TEP states that 

‘‘Initially, the units will alternate idling between 

spring and fall (both seasons include the adjacent 

winter months). TEP plans to transition Unit 1 to 

summer-only operations prior to full retirement at 

the end of 2027.’’ 144Plan, Appendix C, pp. 212. 

negotiated settlement in which 

allowable emissions limits may be 

established as part of injunctive relief, 

and may not necessarily be 

representative of SCR technical 

capabilities. Therefore, we find that 

ADEQ’s analysis of other tangentially 

fired coal units in CAMPD is not 

determinative of the SCR emissions rate 

achievable for the SGS units. 

Finally, though we appreciate the 

summary provided in Table 3 of the 

comment letter, the analysis is new 

information not included in the Plan. 

This information would need to be part 

of a SIP revision subject to review by the 

public and FLMs in order for the EPA 

to consider it as part of the long-term 

strategy. 

Comment D.7. TEP asserts that ADEQ 

reasonably determined that SO2

emissions limits were an appropriate 

and equivalent control measure 

compared to SDA upgrades. TEP notes 

that while the EPA suggests that TEP 

should also be required to install the 

SDA upgrades in addition to the massbased limits, the EPA does not explain 

why SDA upgrades would achieve 

emissions reductions beyond the massbased limits adopted by TEP, which are 

equivalent to SDA upgrades. 

Further, TEP states that the selection 

of emissions limits is consistent with 

the CAA and is entitled to deference. 

First, TEP reasons that the CAA does 

not require the installation of specific 

control technologies, and that the EPA 

has recognized in the 2019 Guidance 

that mass-based limits may be a 

reasonable alternative to specific control 

technologies, particularly where fixed 

capital costs are high, so long as such 

limits do not enable a source to cease 

operating an existing control 

technology. Second, TEP asserts that the 

emissions limits are equally or more 

protective than control technologies 

because the total SO2 emitted cannot 

exceed the caps, and whether one or 

both units is operating is irrelevant, and 

because it provides the flexibility for 

greater total emissions reductions to 

occur, should TEP ultimately retire SGS 

Unit 1 in 2027. The commenter specifies 

that if TEP elects to achieve compliance 

with the proposed caps by shutting 

down Unit 1, it is projected to reduce 

SO2 emissions by 2,982 tpy and achieve 

significant reductions in NOX and PM 

emissions, whereas the installation of 

SDA upgrades at both units is projected 

to reduce SO2 emissions by 2,122 tpy. 

Third, TEP asserts that the emissions 

limits are consistent with EPA 

precedent. TEP listed previous 

examples of EPA-approved mass-based 

emissions limits, such as the Hawaii 

Regional Haze FIP for three Hawaiian 

Electric facilities 136 and the Regional 

Haze FIP for PCC.137

Response D.7. We disagree with TEP’s 

assertions that the selection of massbased SO2 emissions limits for SGS 

Units 1 and 2 was reasonable for the 

reasons described in Section IV.E.2.c.iii 

of our proposal,138 and Response B.8 of 

this document. 

We also disagree with TEP’s assertion 

that the EPA did not explain why SDA 

upgrades would achieve emissions 

reductions beyond the mass-based 

limits adopted by ADEQ. As stated in 

the proposed rule,139 because the limits 

are set across two units and the ton per 

day (tpd) limit is based on a 30- 

calendar-day average (rather than a 30- 

day-boiler-operating day average),140

they would not meaningfully constrain 

the emissions from one unit during 

periods when the other unit is not 

operating. In particular, the annual SO2

cap of 3,739 tpy is significantly higher 

than ADEQ’s projected 2028 SO2

emissions for either Unit 1 or Unit 2 

(2,869 and 2,982 tpy, respectively) 141

and nearly double each unit’s recent 

emissions (1,980 and 1,988 tpy 

respectively on average 2021–2023).142

Accordingly, if TEP shuts down SGS 

Unit 1 by 2028, as it has stated it intends 

to do,143 Unit 2 would be able to emit 

3,739 tpy SO2 in 2028, nearly double 

what it emitted on average in 2021–2023 

and significantly more than the 2,982 

tpy it is projected to emit in the absence 

of a cap and closure of Unit 1. In 

contrast, a lb/MMBtu limit representing 

SDA upgrades on each unit would 

ensure emissions from Unit 2 would be 

reduced by approximately 1⁄3 from 

recent emissions levels (i.e., a reduction 

of roughly 663 tpy) even if Unit 1 ceases 

operation. Therefore, under the scenario 

projected by TEP to occur in 2028 (i.e., 

closure of SGS Unit 1), implementation 

of SDA upgrades at Unit 2 would 

achieve significant emissions reductions 

beyond the mass-based limits adopted 

by ADEQ. 

We also note that, if SGS Unit 1 does 

not close and both units continue 

operation at roughly the same level as 

2021–2023, a lb/MMBtu limit 

representing SDA upgrades on each unit 

would ensure emissions from both Unit 

1 and Unit 2 would be reduced by 

approximately 1⁄3 (i.e., a reduction of 

roughly 1,323 tpy based on 2021–2023 

emissions), whereas ADEQ’s annual cap 

of 3,739 tpy would only ensure 

reductions of 229 tpy (i.e., compared to 

total 2021–2023 annual average 

emissions of 3,968). Therefore, we 

expect that lb/MMBtu limits 

representing SDA upgrades on each unit 

would achieve significantly greater 

emissions reductions than the two-unit 

mass-based limits adopted by ADEQ. 

For similar reasons, we also do not 

agree with TEP’s statements that ‘‘the 

proposed form of the limit is potentially 

more environmentally protective than 

the installation of controls because it 

provides the flexibility for greater total 

emission reductions to occur, should 

TEP ultimately retire SGS Unit 1 in 

2027’’ and that ‘‘[r]equiring the use of 

air pollution control technology at each 

unit individually would foreclose a 

more environmentally beneficial 

compliance option.’’ Specifically, TEP 

incorrectly cites Table 83 as supporting 

its assertion that if it ‘‘elects to achieve 

compliance with the proposed caps by 

shutting down Unit 1, it is projected to 

reduce SO2 emissions by 2,982 tpy and 

also to achieve significant reductions in 

NOX and PM emissions.’’ This 

mischaracterizes the content of Table 

83, which reflects ADEQ’s baseline 

projection of emissions at the TEP units, 

based on emissions and throughput data 

for 2016, 2018 and 2019.144 These 

values were the starting point for 

ADEQ’s four-factor analysis and do not 

represent the projected emissions of 

these units following implementation of 

the emissions caps and/or the closure of 

Unit 1. No such projection is included 

in the Plan. However, as noted in the 

preceding paragraph, if TEP shuts down 

SGS Unit 1 by 2028, as it has stated it 

intends to do, Unit 2 could emit as 

much as 3,739 tpy SO2 in 2028, nearly 

double what it emitted on average in 

2021–2023 and significantly more than 

the 2,982 tpy it is projected to emit in 

the absence of a cap and closure of Unit 

1. 

Third, in response to TEP’s claim 

about EPA precedent, both FIP actions 

cited by TEP apply to first planning 

period requirements and thus preceded 

the 2017 revisions to the RHR, which 

added 40 CFR 51.308(f). Please see 

Response B.8 for more information 


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145 77 FR 31692, 31712 (May 29, 2012) (‘‘without 

further control, emissions of SO2 on the Big Island 

are projected to increase by nearly 4% between 

2005 and 2018. Therefore, additional, federally 

enforceable SO2 reductions are needed on the Big 

Island to ensure reasonable progress.’’) 

146 Id. at 31708. 

147 2021 Clarifications Memo, p. 12. 

148 2019 Guidance, p. 34 (citing 40 CFR 

51.308(f)(2)); Clarifications Memo, p. 10. 

149 79 FR 9318, 9341, Table 24 (rejecting DSI 

based on incremental costs of $8,576/ton compared 

to lower sulfur fuel blend). 

150American Corn Growers Association v. EPA, 

291 F.3d 1, 6–7 (D.C. Cir. 2002). 

151 89 FR 47398, 47429. 152 Id. (interpreting CAA section 169A(g)(2)). 153CAA 169A(g)(1). 154 2022 Arizona Regional Haze Plan, Appendix 

K, p. 9. 

155See 2022 Arizona Regional Haze Plan, 

Appendix C, p. 234 (‘‘small visibility benefits 

associated with the modeled SO2 controls supports 

the determination that CDS and wet FGD control 

options are not necessary to make reasonable 

progress towards natural visibility at Class I areas 

during this implementation period’’). 

156 Id. 

about PCC. The other precedent cited by 

ADEQ, a cap on the Hawaiian Electric 

sources, was not based solely on a 

determination that a particular control 

measure was necessary to make 

reasonable progress under the four 

statutory factors. Rather, the cap was 

intended primarily to ensure that no 

degradation in visibility conditions 

would occur at the affected Class I area 

during the first or subsequent planning 

periods, as required under the RHR.145

This was based on circumstances that 

were specific to Hawaii in the first 

planning period, namely, that no 

photochemical modeling had been 

performed for Hawaii’s Class I areas and 

the EPA set the RPGs for these areas 

based on island-specific emissions 

inventories.146 None of these 

circumstances apply to Arizona 

generally, or to SGS Units 1 and 2 

specifically, in the second regional haze 

planning period and thus are 

inappropriate to rely upon. 

Comment D.8. TEP comments that 

ADEQ reasonably rejected additional 

control measures based on the four 

factors. For remaining useful life 

specifically, TEP indicates that a 20-year 

remaining useful life is more 

appropriate for SGS Units 1 and 2 

because the shutdowns are publicly 

documented in the 2023 IRP. TEP cites 

the 2021 Clarifications Memo as stating, 

‘‘reasonable bases for projecting that 

future emissions will be significantly 

different than past emissions are 

enforceable requirements and energy 

efficiency, renewable energy, or other 

similar programs, where there is a 

documented commitment to participate 

and a verifiable basis for quantifying 

changes in future emissions.’’ 147 TEP 

noted that consistent with this 

guidance, TEP’s planned retirement of 

these units significantly shortens the 

remaining useful life of any controls and 

projected emissions reductions, and a 

20-year remaining useful life is a 

reasonable, conservative basis to 

analyze cost-effectiveness of additional 

controls. 

Response D.8. We disagree that 20 

years is a reasonable remaining useful 

life for SGS Units 1 and 2. The portion 

of the 2021 Clarifications Memo cited by 

TEP concerns setting emissions limits 

for control measures found necessary to 

make reasonable progress, not 

remaining useful life. Therefore, this 

citation does not support TEP’s 

assertion. Additionally, the 2019 

Guidance and Clarifications Memo 

clearly indicate that, under the RHR, 

where a shutdown date is used to 

shorten a source’s remaining useful life 

as part of a reasonable progress 

determination, an enforceable 

requirement to shutdown must be 

included in the SIP and/or be federally 

enforceable.148 The potential shutdowns 

of SGS Units 1 and 2 are not federally 

enforceable. Therefore, they cannot be 

relied upon to shorten the remaining 

useful life of these units. In the absence 

of an enforceable requirement for SGS 

Units 1 and 2 to retire, we do not agree 

that a 20-year remaining useful life is 

reasonable. 

Comment D.9. TEP comments that 

ADEQ reasonably rejected additional 

control measures in part by considering 

incremental costs. TEP noted that ADEQ 

determined incremental costs for 

additional controls would range from 

$9,400–13,500/ton, and that even the 

low end of this range exceeded similar 

incremental costs that the EPA 

determined to be excessive for sources 

in Arizona as part of the 2014 BART 

FIP.149

TEP further states that ADEQ 

reasonably considered incremental costeffectiveness where the cost impacts 

were not clear due to uncertainty in the 

remaining useful life of the additional 

controls. Citing American Corn Growers 

Association vs. EPA, TEP states that it 

is reasonable for a state to consider 

incremental visibility improvements 

and other incremental metrics to inform 

its assessment of whether a particular 

control is ‘‘too costly . . . for a 

particular source.’’ 150 TEP notes that 

such an assessment does not give 

‘‘controlling weight’’ to the cost factor, 

but rather considers whether, on 

balance, it would be unreasonable to 

require installation of a control, 

consistent with the language of CAA 

section 169A. 

Lastly, TEP asserts that ADEQ 

reasonably compared the costs of and 

emissions reductions achievable with 

wet FGD and circulating dry scrubbers 

(CDS) to the costs of and emissions 

reductions achievable with SDA 

upgrades, even where such upgrades 

were not required to be installed. The 

commenter argues that ADEQ 

reasonably used SDA upgrades as a 

proxy for its mass-based emissions 

limits, since these limits were 

developed based on equivalence with 

SDA upgrades and the EPA’s approach 

for Hawaiian Electric. 

Response D.9. We disagree that 

ADEQ’s use of incremental cost 

effectiveness was reasonable for the 

reasons explained in Section IV.E.2.C.IX 

of our proposal 151 and Response B.6 of 

this document. We also note that, while 

the commenter refers to ‘‘similar 

incremental costs that the EPA 

determined to be excessive for sources 

in Arizona as part of the 2014 BART 

FIP,’’ the accompanying citation refers 

to only to a single source, i.e., Nelson 

Lime Kiln, which is the same source 

cited by ADEQ in the Plan. 

We also find that the commenter’s 

citation to American Corn Growers is 

inapposite. That decision concerned the 

EPA’s interpretation of the BART 

provisions of the CAA and turned on 

the fact that the CAA includes the ‘‘the 

degree in improvement in visibility that 

would be expected at each Class I area 

as a result of imposing BART’’ as one of 

five factors to be considered in BART 

determinations.152 In contrast, the Act 

does not mandate visibility 

improvement as one of the four factors 

to be considered in determining 

reasonable progress.153 As discussed in 

Response B.7, ADEQ indicated in its 

Response to Comments that it did not 

consider this factor in its 

determinations.154 Furthermore, even if 

ADEQ did consider visibility 

improvement in making control 

determinations for SO2 at SGS Units 1 

and 2,155 it is evident that ADEQ did not 

consider incremental visibility 

improvement associated with Wet FGD 

compared to SDA upgrades. Rather, 

ADEQ considered only ‘‘a hypothetical 

SO2 emission reduction of 3,236 tpy, 

which is approximately equivalent to 

0.08 lb/MMBtu for SGS Units 1 and 

2.’’ 156 This level of reductions does not 

correspond either to SDA upgrades or 

wet FGD, so ADEQ could not possibly 

have considered the incremental 

visibility benefit between the levels of 

control. Accordingly, American Corn 

Growers has no bearing on our 

assessment of whether ADEQ’s 

approach to its four factor analyses and 


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102764 Federal Register / Vol. 89, No. 243 / Wednesday, December 18, 2024 / Rules and Regulations 

157 2022 Arizona Regional Haze Plan, Appendix 

K at 9 (explaining that visibility information ‘‘was 

not considered in the Department’s emission 

control measure determination’’). 

158Citing 89 FR 47481, 47498. 

159 89 FR 47398, 47432, Table 21. 

160 89 FR 47398, 47430 (citing 40 CFR 

51.308(f)(2)(i)). 

161 Id. 

162 2021 Clarifications Memo, pp. 10, 12. 

163 Id. p. 10. 

164 2019 Guidance p. 29 (emphases added). 

determinations for SGS Units 1 and 2 

were reasonable. 

In addition, we also disagree that 

there is uncertainty in the remaining 

useful life of SGS Units 1 and 2, because 

the potential shutdowns at these units 

are not federally enforceable. See 

Response D.8. 

Finally, we disagree that ADEQ 

reasonably used SDA upgrades as a 

proxy for its mass-based emissions 

limits. See Responses B.8 and D.7. 

Comment D.10. TEP states that the 

EPA incorrectly implies that ADEQ 

based its control determinations on 

visibility benefits, when ADEQ stated 

otherwise in its SIP submission.157

Second, TEP notes that any 

consideration of visibility would be 

consistent with recent EPA actions on 

regional haze and the text of the statute. 

Citing the EPA’s recent proposed action 

on the Georgia Regional Haze SIP, TEP 

states that the EPA emphasized 

incremental visibility improvements 

and that ‘‘Georgia is also not 

contributing to visibility impairment at 

any Class I areas above the URP.’’ 158

TEP claims that because Arizona has 

similarly de minimis contributions to 

visibility impairment at Class I areas,159

the EPA cannot apply inconsistent 

criteria to its review of SIP submissions 

by different states. Finally, citing Loper 

Bright Enterprises v. Raimondo, 144 S. 

Ct. 2244, 2263 (2024), TEP argues that 

‘‘EPA’s suggestion that visibility should 

play little-to-no role in a state’s 

assessment of reasonable progress is 

unreasonable and counter to the text of 

the statute.’’ 

Response D.10. Regarding whether 

ADEQ considered visibility benefits, in 

its control determinations, please see 

Response B.7. 

We disagree that the EPA is applying 

inconsistent criteria to review of SIP 

submissions by different states. As 

explained in Response D.2, in the 

section of the Georgia action cited by 

the commenter, the EPA considered 

overall trends in visibility impairment 

in evaluating the reasonableness of 

Georgia’s source selection methodology. 

This is entirely different from weighing 

the potential visibility benefits of 

specific controls at specific units, which 

is what the commenter appears to be 

advocating for. Additionally, the quoted 

section of the Georgia proposal simply 

states as a fact that Georgia is not 

contributing to visibility impairment at 

any Class I areas above the URP. That 

information is not used and should not 

be used as a ‘‘safe harbor’’ argument to 

exclude contributing sources from a 

four-factor analysis and potentially 

including cost-effective controls in the 

long-term strategy. 

Moreover, we do not agree that 

Arizona has de minimis contributions to 

visibility impairment at Class I areas. In 

support of this assertion, TEP cites 

Table 21 on page 47432 of the proposal. 

This table shows Baseline Conditions, 

Adjusted URP and 2028 RPGs at 

Arizona’s Class I areas. However, the 

table provides no indication of which 

sources contribute to visibility 

impairment at these Class I areas, or 

whether these sources are located in 

Arizona or elsewhere. This table also 

does not address any Class I areas 

outside of Arizona. Furthermore, there 

is no other information in the Plan that 

suggests that emissions from Arizona 

have de minimis contributions to 

visibility impairment at all potentially 

affected Class I areas. Therefore, we do 

not agree that the EPA is applying 

inconsistent criteria to review of SIP 

submissions by different states. 

Finally, we disagree that we suggested 

that ‘‘visibility should play little-to-no 

role in a state’s assessment of reasonable 

progress.’’ Rather, we stated that 

‘‘[w]hether a particular visibility impact 

is meaningful should be assessed in 

context and cannot be used to 

undermine the four statutory factors that 

are to be analyzed in order to determine 

what measures are necessary for 

reasonable progress.’’ 160 Applying these 

considerations to ADEQ’s discussion of 

visibility benefits at SGS Units 1 and 2, 

we found that ‘‘[i]n the absence of any 

opportunities for larger emissions 

reductions and corresponding visibility 

benefits, we find that ADEQ’s reliance 

on ‘small’ visibility benefits as an 

additional justification for not adopting 

more stringent controls at these units is 

not persuasive.’’ 161 Therefore, we do 

not agree with the commenter’s 

characterization of our proposal. 

Comment D.11. TEP asserts that 

ADEQ appropriately incorporated ‘‘onthe-way’’ measures in assessing baseline 

conditions at IGS Unit 3. TEP cites the 

2021 Clarifications Memo and states 

that the EPA has explicitly recognized 

‘‘on-the-way’’ measures that ‘‘have not 

yet been implemented and the 

associated emissions reductions have 

not yet occurred as of the SIP 

submission date,’’ and that the EPA 

indicated that these measures may 

impact a state’s choice of baseline for a 

four-factor analysis at a particular 

source (‘‘reasonable bases for projecting 

that future emissions will be 

significantly different than past 

emissions are enforceable requirements 

and energy efficiency, renewable 

energy, or other similar programs, where 

there is a documented commitment to 

participate and a verifiable basis for 

quantifying changes in future 

emissions’’).162 TEP claims that the 

operational conditions at IGS Unit 3 

have been incorporated in an 

enforceable permit, and will become 

effective upon approval of Arizona’s SIP 

submission. TEP also claims that it has 

a documented commitment to 

complying with these limits by 

requesting these permit limits. 

Response D.11. TEP mischaracterizes 

the contents of the 2021 Clarifications 

Memo. The first section of the memo 

cited by the commenter, entitled ‘‘Onthe-Way’’ Measures and Shutdowns, 

states that ‘‘on-the-way measures . . . 

are necessary to make reasonable 

progress and must be included in a 

SIP.’’ 163 In this case, because the IGS 

Unit 3 limits have not taken effect under 

State law, their inclusion as part of the 

SIP revision is not meaningful, and they 

are not an appropriate basis for 

modifying the baseline control scenario 

for a four-factor analysis. 

The second portion of the 2021 

Clarifications Memo cited by TEP 

concerns setting emissions limits for 

control measures that have been found 

necessary to make reasonable progress. 

It is not relevant to the question of the 

extent to which existing measures may 

be considered as part of the baseline for 

a control analysis. Regarding this latter 

question, the 2019 Guidance states that: 

Enforceable requirements are one 

reasonable basis for projecting a change in 

operating parameters and thus emissions; 

energy efficiency, renewable energy, or other 

such programs where there is a documented 

commitment to participate and a verifiable 

basis for quantifying any change in future 

emissions due to operational changes may be 

another. A state considering using 

assumptions about future operating 

parameters that are significantly different 

than historical operating parameters should 

consult with its EPA Regional office.164

Again, the emissions limits at IGS 

Unit 3 are not enforceable by the State 

or the EPA unless and until the 

resulting reasonable progress 

determination is approved into the SIP. 

Moreover, the permit conditions that 

would implement the caps were 

adopted specifically to meet regional 


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165See, e.g., 2022 Arizona Regional Haze Plan, 

Appendix C, p. 197 (describing TEP’s submittal of 

permit application for NOX caps in response to 

ADEQ’s initial regional haze control determination); 

Appendix G, p. 58 (‘‘The purpose of the proposed 

SIP and significant permit revision is to support 

ADEQ’s forthcoming periodic comprehensive 

regional haze SIP submittal to EPA.’’). 

166See 568 F.2d 284 (3d Cir.1977), cert. denied, 

435 U.S. 914, 98 S.Ct. 1467, 55 L.Ed.2d 505 (1978). 

167See CAA section 110(l), 40 CFR 40 CFR 

51.102, and 5 U.S.C. 553. 

168SRP cited in the comment letter, but we note 

that the correct citation is 82 FR 46903 (October 10, 

2017). 

haze requirements and were not part of 

‘‘energy efficiency, renewable energy, or 

other such programs.’’ 165 Therefore, we 

find that they are not a reasonable basis 

for projecting a change in operating 

parameters. 

Comment D.12. TEP asserts that 

ADEQ reasonably evaluated additional 

control measures using a four-factor 

analysis for IGS Unit 3 based on 

excessive costs. TEP explains that each 

of the NOX controls available for IGS 

Unit 3 exceed Arizona’s cost threshold 

of $6,500/ton, and ADEQ therefore 

determined that no additional controls 

were reasonable for the second planning 

period. TEP also noted that while the 

average cost of installing combustion 

control retrofits at IGS Unit 3 was only 

$230/ton above ADEQ’s $6,500/ton 

threshold, the RHR does not prevent 

states from implementing ‘‘bright line’’ 

cost-effectiveness thresholds when 

considering additional control 

measures. 

Response D.12. We partly agree with 

this comment. We agree that the NOX

controls analyzed for IGS Unit 3 exceed 

the cost threshold of $6,500, when the 

emissions limits in the permit (which 

are not yet in effect) are considered as 

part of the baseline control scenario. 

However, as described in section 

IV.E.2.c.iii of our proposal, and 

Response D.11, we do not agree that 

these limits are an appropriate basis for 

modifying the baseline control scenario 

for a four-factor analysis. We also agree 

the RHR does not prevent states from 

implementing ‘‘bright line’’ costeffectiveness thresholds, but we find 

that ADEQ did not do so in a reasonable 

or consistent manner in the Plan, as 

discussed in Response D.4. 

E. Comment Letter From SRP 

Sections I (‘‘Introduction’’), II 

(‘‘Background’’), III (‘‘SRP Facilities 

Subject to the Proposed Rule’’) and IV 

(‘‘EPA Has Appropriately Proposed 

Approval of Several Aspects of 

Arizona’s Regional Haze SIP’’) of SRP’s 

comment letter either provide 

background information or are 

supportive and therefore do not require 

a response. We respond to sections V– 

XI of SRP’s comment letter below. 

Comment E.1. SRP comments that the 

proposed rule is vague and deprives the 

public of an adequate opportunity for 

comment. Citing American Iron & Steel 

Institute v. EPA, SRP notes that the EPA 

is obligated to provide the public with 

information sufficient to facilitate 

public comment on the proposal, and 

that it is not clear which grounds for the 

proposed partial disapproval of the SIP 

submission apply to which sources. SRP 

provides a few examples of allegedly 

vague language in the proposed rule, for 

example, noting ‘‘some’’ of Arizona’s 

four-factor analyses were affected in a 

few instances. SRP asserts that because 

it is not clear which aspects of the EPA’s 

analysis apply to which facilities, the 

public cannot reasonably evaluate the 

grounds for the proposed disapproval 

actions, and therefore the EPA needs to 

issue a new proposed rule that provides 

additional necessary detail in support of 

the proposed actions. 

Response E.1. We disagree with this 

comment. In American Iron & Steel 

Institute,166 the court denied, in part, 

review of an EPA interim final rule due 

to a lack of proper notice. However, as 

described in Response A.1, we do not 

agree that the proposed rule deprives 

the public of an adequate opportunity 

for comment. 

We also note that, in acting on the 

2022 Arizona Regional Haze Plan, the 

EPA is not issuing new requirements 

applicable to any emissions sources. 

Rather, this final partial disapproval 

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. Accordingly, 

Arizona can develop and submit a SIP 

revision addressing the disapproved 

elements of the Plan. Both the state’s 

adoption of that SIP revision and the 

EPA’s subsequent action on that SIP 

revision would be subject to public 

notice and comment requirements.167

Similarly, if the EPA does not fully 

approve a SIP submission addressing 

the disapproved elements of the Plan, 

any FIP promulgated by the EPA would 

be subject to public notice and 

comment. Accordingly, there will be 

ample additional opportunities for the 

public, including potentially regulated 

entities, to engage in the rulemaking 

process before any additional 

requirements take effect. 

Comment E.2. SRP asserts that the 

EPA should approve Arizona’s 

determination that Coronado Generating 

Station and SGS Unit 4 are effectively 

controlled because they are consistent 

with the law and EPA guidance. SRP 

states that the 2019 Guidance indicates 

that sources that have recently installed 

effective controls are the prime example 

of sources that do not require evaluation 

during the current planning period. 

Specifically, SRP notes that the 2019 

Guidance states that BART-eligible units 

that installed and began operating 

controls to meet BART emissions limits 

for the first implementation period, 

including sources that installed controls 

to comply with a better-than-BART 

alternative, may be considered to be 

effectively controlled. 

For Coronado, SRP states that the 

source is subject to a better-then-BART 

alternative that the EPA approved in 

October 2017, and that there have been 

no intervening changes in technology 

since that time. SRP states that 

Coronado will also install new controls 

(SCR) to comply with the BART 

alternative by January 2026.168 SRP 

noted that the first planning period 

regional haze SIP submission for 

Coronado also includes two additional 

requirements for SO2: an SO2 emissions 

limit of 0.060 lb/MMBtu, calculated on 

a 30-boiler-operating-day rolling average 

and an annual plant-wide SO2

emissions cap of 1,970 tons per year. 

SRP further asserts that SGS Unit 4 is 

similarly well-controlled. ADEQ 

determined that Unit 4’s existing 

controls of combustion controls 

(LNB+OFA) and SCR is the most 

effective control technology available 

for NOX for coal fired EGUs, and thus, 

no further analysis for other control 

technologies was needed. For SO2, Unit 

4 is equipped with SDA systems subject 

to the MATS rule and has been 

achieving an SO2 emissions rate over 

the most recent five years ranging from 

0.076 to 0.10 lb/MMBtu on an annual 

basis. For PM, Unit 4 is equipped with 

a baghouse, which ADEQ found to have 

the highest PM control efficiency of any 

PM control considered for Unit 4. 

Response E.2. Regarding Coronado 

Generating Station, we agree that the 

source was subject to a better-than 

BART alternative. However, we note 

that the commenter mischaracterizes the 

contents of the 2019 Guidance regarding 

effective control determinations for 

BART-eligible sources. The relevant 

portion of the Guidance includes as an 

example of potentially effective 

controls, ‘‘BART-eligible units that 

installed and began operating controls 

to meet BART emission limits for the 

first implementation period, on a 


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169See 2019 Guidance, p. 25 (emphasis added). 

170 Id., n. 54. 171 89 FR 47398, 47404. 

pollutant-specific basis.’’ 169 The 

Guidance further explains that: 

Although the Regional Haze Rule 

anticipates the re-assessment of BARTeligible sources under the reasonable 

progress Rule provisions, if a source 

installed and is currently operating 

controls to meet BART emission limits, 

it may be unlikely that there will be 

further available reasonable controls for 

such sources. However, states may not 

categorically exclude all BART-eligible 

sources, or all sources that installed 

BART controls, as candidates for 

selection for analysis of control 

measures. 

The associated footnote clarifies that 

this consideration is not applicable to 

BART-subject units for which the BART 

requirement was met in whole or in part 

by emissions reductions at other units 

as part of a better-than-BART alternative 

or trading program.170

As discussed in our proposal and 

Response B.3 of this document, ADEQ 

excluded all units that installed BART 

(or better-than-BART) controls between 

2014 and 2028 for any pollutant. We 

therefore disagree that Arizona followed 

the 2019 Guidance in evaluating 

effective controls because it 

categorically excluded all such units 

without considering whether the unit in 

question installed effective controls for 

NOX, SO2 and PM10, or whether the 

BART requirement was met in part by 

reductions at other units as part of a 

better-than-BART alternative. 

Regarding SGS Unit 4, see Response 

D.2. 

Comment E.3. SRP states that the 

EPA’s assumed emissions rate for SCR 

controls of 0.05 lb/MMBtu is not 

feasible at coal-fired EGUs. SRP asserts 

that the EPA cannot assume all coalfired units are capable of the same 

efficiencies following pollution control 

installation or that these controls incur 

the same costs for each unit nationwide, 

irrespective of the local conditions and 

operations impacting individual units. 

SRP further notes that the EPA’s 

conclusion that all SCR retrofitted units 

can uniformly meet a NOX emissions 

limit of 0.05 lb/MMBtu without proper 

evaluation and consideration of 

individual units is arbitrary and 

capricious and may unlawfully impose 

limits on EGUs that are unachievable. 

SRP further points out that the cited 

Srivastava et al. study notes units that 

achieved NOX emissions rates between 

0.04 and 0.07 lb/106 Btu, and that this 

range illustrates the variability 

associated with SCR-controlled coalfired unit NOX emissions rates and the 

importance of considering unit-specific 

factors when identifying a controlled 

emissions rate. 

Citing Appendix K of the Plan, SRP 

further asserts that ADEQ specifically 

addressed unit-specific considerations 

when setting the SGS Unit 1 and 2 NOX

emissions rates by reviewing CAMPD 

data. By assuming an SCR controlled 

NOX emissions rate of 0.06 lb/MMBtu, 

ADEQ is assuming that SGS Units 1 and 

2 will achieve a controlled emissions 

rate within the top 21 percent of 

tangentially-fired EGUs. SRP indicates 

that without acknowledging ADEQ’s 

evaluation, the EPA states that ADEQ 

did not provide adequate justification 

and unreasonably assumes an emissions 

rate within the top 5 percent of SCR 

controlled tangentially-fired EGUs is 

appropriate for the SGS Unit 1 and 2. 

SRP concludes that while the state made 

reasonable conclusions as to the 

emissions rates achievable by SCR at 

specific facilities, the EPA has not. 

Response E.3. We disagree that the 

EPA has assumed that all coal-fired 

units are capable of the same 

efficiencies following pollution control 

installation or that these controls incur 

the same costs for each unit. As 

described in Responses B.4 and D.6, we 

have considered unit-specific factors in 

evaluating the emissions rates 

achievable with SCR at SGS Units 1 and 

2, and we are not aware of any 

assertions that SGS specifically cannot 

achieve 0.050 lb/MMBtu when 

operating with SCR during periods of 

normal operation. Therefore, we find 

that ADEQ should have considered a 

controlled NOX emissions rate of 0.050 

lb/MMBtu for SGS Units 1 and 2 when 

operating with SCR during periods of 

normal operation. As further explained 

in Response B.4, this does not mean that 

0.050 lb/MMBtu would be an 

appropriate 30–BOD limit for these 

units, but rather that it should be 

considered as annual emissions rate for 

purposes of the control cost analysis. 

Comment E.4. SRP comments that it 

is not necessary to include control 

requirements for Coronado Generating 

Station in Arizona’s Regional Haze SIP. 

SRP states that under CAA section 

169A, a state (or the EPA) may only 

require a long-term strategy to include 

those control measures that are found to 

be necessary to make reasonable 

progress through the evaluation of the 

four statutory reasonable progress 

factors. SRP claims that the EPA’s 

position that in the absence of a fourfactor analysis supporting new controls, 

existing controls should generally be 

deemed necessary to make reasonable 

progress and be included in the regional 

haze SIP is not a valid reading of the 

CAA’s visibility provisions. Further, 

SRP claims that the CAA framework ties 

reasonable progress controls to the fourfactor analysis, and does not leave room 

for the EPA’s presumption that existing 

controls must be included in a SIP even 

whenever a four-factor analysis failed to 

identify new controls that should be 

implemented. Such existing controls 

may only be deemed necessary 

components of a regional haze SIP if a 

four-factor analysis independently 

identifies such controls as necessary for 

reasonable progress. 

SRP further cites both the 2021 

Clarifications Memo (‘‘There may be 

other cases where, after having 

conducted robust source selection and 

rigorous analysis of the four factors, 

states have not identified any new 

measures that are reasonable to require 

for a source. In such cases, states will 

have to address whether the source’s 

existing measures are necessary to make 

reasonable progress’’) and 2019 

Guidance: (‘‘[i]f a state determines that 

an in-place emission control at a source 

is a measure that is necessary to make 

reasonable progress and there is not 

already an enforceable emission limit 

corresponding to that control in the SIP, 

the state is required to adopt emission 

limits based on those controls as part of 

its long-term strategy in the SIP via the 

regional haze second planning period 

plan submission’’). SRP claims that the 

EPA therefore acknowledged that there 

should be no presumption that existing 

measures are needed for reasonable 

progress. 

Lastly, SRP states that Coronado 

Generating Station is already subject to 

a source-specific SIP revision that was 

designed to implement the better-thanBART alternative during the first 

planning period of the regional haze 

program. SRP asserts that because these 

requirements are already binding and 

enforceable, there is no need for any 

additional action to address Coronado. 

Response E.4. First, we disagree that 

existing controls being necessary for 

reasonable progress does not have a 

basis in the statute for two reasons. 

First, under CAA 169A(a)(1), the 

national visibility goal is generally 

seperated into two parts: (1) the 

prevention of any future, and (2) the 

remedying of any existing 

anthropogenic visibility impairment. As 

noted in the proposed rule,171 and in 

response B.1, continued implementation 

of the source’s existing measures is 

generally necessary to prevent future 

emissions increases and thus necessary 


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172See Committee for a Better Arvin v. EPA, 786 

F.3d 1169, 1175–77 (9th Cir. 2015). 

173CAA 169A(b)(2). 

174CAA 169A(b)(2)(B). 

175 2021 Clarifications Memo, pp. 8–9 (emphasis 

added). 

176See, e.g., 79 FR 9318, 9342 (rejecting controls 

based on incremental costs of $8,803 and $8,576/ 

ton); 76 FR 80754, 80756 (December 27, 2011) 

(rejecting controls based on incremental costs of 

$5,367/ton). 

to make reasonable progress towards the 

national goal. 

Second, control measures used to 

fulfill a CAA requirement must be in the 

SIP.172 In this instance, in order to make 

reasonable progress toward the national 

goal, the CAA requires every regional 

haze SIP to contain ‘‘such emission 

limits, schedules of compliance, and 

other measures as may be necessary for 

reasonable progress.’’ 173 The CAA also 

requires each regional haze SIP 

submission to include a long-term 

strategy ‘‘for making reasonable progress 

toward meeting the national goal.’’ 174

Finally, reasonable progress is defined 

in the CAA as a consideration of the 

four factors outlined in CAA 169A(g)(1). 

If the State opts to avoid conducting the 

required consideration of the four 

statutory factors on a source or group of 

sources based solely on the source’s 

existing measures, then, in order to 

fulfill its long-term strategy 

requirements, those existing measures 

must also be in the SIP, or else the state 

must demonstrate that the existing 

measures are not necessary to make 

reasonable progress. This ensures that 

this source’s contribution to visibility 

impairment will not increase, and also 

ensures that all measures being relied 

upon to fulfill the regional haze 

requirements are in the SIP. Therefore, 

if Arizona is relying on existing 

measures to avoid the statutorily 

required four factor analysis, then those 

existing measures must be in the SIP 

and thus a part of its long-term strategy 

for the second planning period, unless 

the State demonstrates that they are not 

necessary to make reasonable progress. 

Additionally, we disagree that the 

EPA’s guidance documents 

acknowledged that there should be no 

presumption that existing measures are 

needed for reasonable progress. The 

2021 Clarifications Memo is clear that, 

under the CAA and the RHR, ‘‘when the 

outcome of a four-factor analysis is that 

no new measures are reasonable for a 

source, the source’s existing measures 

are generally needed to prevent future 

visibility impairment (i.e., to prevent 

future emission increases) and thus 

necessary to make reasonable 

progress.’’ 175 ADEQ did not provide 

this analysis of whether existing 

measures are necessary to make 

reasonable progress. 

Finally, while we agree that Coronado 

Generating Station is already subject to 

a source-specific SIP that was designed 

to implement a better-than-BART 

alternative for the first implementation 

period, we do not agree that this 

automatically means, without further 

justification, that there is no need for 

any additional action to Coronado in the 

second implementation period for the 

reasons described in E.2. 

Comment E.5. SRP asserts that the 

EPA should approve Arizona’s control 

determinations and four-factor analyses 

with respect to cost-effectiveness 

thresholds, incremental costs, 

compliance with the Control Cost 

Manual, and consideration of visibility. 

First, regarding cost-effectiveness 

thresholds, SRP indicates that Arizona’s 

cost-effectiveness threshold of $6,500/ 

ton is reasonable and should be 

approved, along with the control 

determinations the state made in 

reliance on that threshold. SRP noted 

other examples of cost-effectiveness 

thresholds in other states (Georgia and 

Arkansas) that are lower than the values 

Arizona adopted. SRP also cites the 

EPA’s recent proposal for Missouri that 

cites a $6,060 to $7,600/ton threshold 

from the Central Regional Air Planning 

Association and Texas BART FIP 

threshold range of $5,300/ton to $6,500/ 

ton that is consistent with the $6,500/ 

ton threshold adopted by Arizona. 

Therefore, SRP concludes that ADEQ’s 

threshold is reasonable and represents a 

conservatively high threshold from a 

historical perspective. 

Second, regarding incremental costs, 

SRP asserts that the EPA provided no 

rationale for finding ADEQ’s approach 

unreasonable, and that it was 

appropriate to only consider 

incremental costs if a simple dollar-perton analysis suggests a control might be 

cost-effective in the absence of more 

nuanced information. SRP notes that 

suggesting that states cannot reasonably 

take incremental costs into account to 

reject control requirements far exceeds 

the EPA’s statutory authority, citing the 

court decision in American Corn 

Growers Association vs. EPA as stating 

that ‘‘[t]he Haze Rule calls for states to 

play the lead role in designing and 

implementing regional haze program to 

clear the air in national parks and 

wilderness areas.’’ SRP further states 

that the EPA states that Arizona 

considered only a single BART 

determination in finding that 

incremental costs of $9,400–13,500/ton 

were excessive, but this value is in line 

with past EPA actions finding 

incremental costs excessive.176

Third, regarding compliance with the 

Control Cost Manual, SRP states that the 

EPA did not provide enough 

information for the public to tell what 

it considers to be the full range of the 

deviations from the Cost Control 

Manual, except for some of the State’s 

remaining useful life values. SRP asserts 

that the EPA’s rules specifically allow 

for deviations from the Manual’s 

methodology and sample calculations 

and values whenever site-specific 

information is more accurate. 

Lastly, regarding consideration of 

visibility, SRP asserts that the EPA 

appears to place inappropriate limits on 

Arizona’s consideration of visibility 

impacts as part of its assessment of 

reasonable progress, and that the State 

took visibility into account as additional 

confirmation that controls were not 

reasonable. SRP also states that the EPA 

has provided no context or analysis for 

stating that visibility impacts must be 

assessed in context to determine if they 

are truly meaningful and justify 

expensive control requirements. SRP 

points out that Table 10–5 of the 2022 

Arizona Regional Haze Plan shows that 

natural visibility is projected to occur at 

all statewide sites between 2028 and 

2056, well ahead 2064 natural 

conditions. SRP concludes that Arizona 

appropriately determined that controls 

were not reasonable for SGS when 

visibility is rapidly improving, costs are 

over or very near a reasonable cost 

threshold, and where visibility 

improvements from potential controls 

would be relatively small. 

Response E.5. The EPA disagrees with 

this comment for a number of reasons. 

First, with respect to cost-effectiveness 

thresholds, the EPA clarifies that we are 

not disapproving Arizona’s average costeffectiveness threshold specifically, but 

rather, finds that the State 

inconsistently applied the threshold and 

did not adequately justify how this 

approach resulted in a reasonable set of 

control measures in the long-term 

strategy for the second planning period. 

We also note that the fact that other 

states have applied lower or similar 

thresholds does not automatically make 

Arizona’s threshold reasonable. For 

further explanation on this point, see 

Response D.4. 

Second, with respect to incremental 

costs, contrary to the commenter’s 

assertion, our proposed rule did not 

suggest that Arizona cannot consider 

incremental costs. However, we reiterate 

that, if a state chooses to consider 

incremental costs, it must do so in a 

reasonable and consistent manner and 


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102768 Federal Register / Vol. 89, No. 243 / Wednesday, December 18, 2024 / Rules and Regulations 

177 89 FR 47398, 47429. 

178 2019 Guidance, pp. 33–34. See also 40 CFR 

51.308(f)(2)(iii) (‘‘The State must 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’’). 

179 89 FR 47398, 47430. 

180 Id. 

181 Id. at 47405. 

182CAA 169A(b)(2) (‘‘. . . each applicable 

implementation plan for a State . . . which may 

reasonably be anticipated to cause or contribute to 

any impairment of visibility . . . [must] contain 

such emissions limits, schedules of compliance and 

other measures as may be necessary to make 

reasonable progress[.]’’); 40 CFR 51.308(f)(2) (‘‘Each 

State must submit a long-term strategy that 

addresses regional haze visibility impairment . . . 

the long-term strategy must include the enforceable 

emissions limitations . . . that are necessary to 

make reasonable progress.’’); see also 2021 

Clarifications Memo, pp. 8–9. 

183See 89 FR 47398, 47433 (‘‘ADEQ provided a 

discussion in its submission that explains how the 

monitor was relocated in 2015 and experienced 

increases in soil and coarse mass extinction.’’) 

that Arizona did not do so in the Plan. 

See Responses B.6, B.8, and D.9. 

Third, with respect to compliance 

with the Control Cost Manual, we note 

that, in addition to discussing remaining 

useful life values, we cited an example 

of where the State used an interest rate 

that was above the then-current prime 

rate without adequate 

documentation.177 While we agree with 

the commenter that States can deviate 

from the Cost Control Manual’s 

methodology and sample calculations 

and values whenever site-specific 

information is more accurate, ADEQ did 

not provide such relevant site-specific 

documentation. In situations where an 

enforceable shutdown date does not 

exist, the remaining useful life of a 

control under consideration should be 

the full period of the useful life of that 

control as recommended by the EPA’s 

Control Cost Manual.178 See Responses 

A.1 and C.4. 

With respect to consideration of 

visibility, we disagree that the EPA has 

provided no context or analysis for 

stating that visibility impacts must be 

assessed in context. On the contrary, in 

our proposed notice, we explained why 

the evaluation and control of smaller 

and better-controlled sources in Arizona 

may be necessary to achieve the 

national goal.179 However, we also 

noted that SGS specifically is by far the 

largest emissions source analyzed by 

ADEQ in the 2022 Arizona Regional 

Haze Plan and ADEQ found that Units 

3 and 4, as well as Units 1 and 2 for 

PM10, were effectively controlled, 

leaving only NOX and SO2 at Units 1 

and 2 as providing an opportunity for 

further control at this source.180 In 

addition, we cited to portions of the 

2019 Guidance and Clarifications Memo 

that provide additional 

recommendations to states that visibility 

improvements could reasonably be 

considered in conjunction with a fourfactor analysis. To the extent that the 

commenter is arguing that the EPA 

should have provided our own analysis 

of visibility impacts, we disagree. The 

EPA’s role in reviewing SIP submittals 

is to assess their compliance with 

applicable requirements, not to address 

those requirements ourselves, as we 

would be obligated to do in a FIP. 

Regarding Table 10–5, we note that 

this table is based on Arizona’s RPGs, 

and that contrary to SRP’s suggestion, 

ADEQ did not cite or discuss this table 

or otherwise reference its RPGs in 

making its control determinations. 

Furthermore, as explained in our 

proposal ‘‘[b]ecause 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.’’ 181 Accordingly, we do not 

agree that Arizona did or should have 

considered the information in Table 10– 

5 in making its control determinations. 

We also note that the commenter 

mischaracterizes the contents of this 

table, insofar as the ‘‘projected date of 

natural visibility for SYCA’’ is 2089, 

which is well after 2064. See also 

response C.5. 

In sum, we disagree that Arizona 

appropriately determined that controls 

were not reasonable for SGS for the 

reasons described in this response, 

elsewhere in this document and in our 

proposal. 

Comment E.6. SRP claims that the 

EPA improperly asserts that Arizona’s 

SIP must require installation of specific 

control technologies, specifically with 

regards to SDA upgrades at SGS Units 

1 and 2. SRP states that the regional 

haze program has not been used to 

impose requirements to install and 

operate specific technologies, and that 

some states have made use of emissions 

caps rather than emissions rates and 

other creative tools to address regional 

haze requirements, including Coronado 

Generating Station during the first 

planning period. 

Response E.6. We agree with the 

commenter that ADEQ was not 

obligated to require installation of a 

particular control. However, the State is 

obligated to set emissions limitations or 

establish other measures corresponding 

to the controls that it determined to be 

necessary to make reasonable 

progress.182 See also Response B.8 

where we note issues with ADEQ’s 

provided rationale in justifying the 

mass-based emissions caps at SGS and 

IGS. Finally, we note that the example 

of Coronado Generating Station was 

under the better-than-BART provisions 

of 40 CFR 51.308(e)(2), rather than the 

provisions of 40 CFR 51.308(f), which 

govern regional haze plans for the 

second implementation period. 

Comment E.7. SRP comments that the 

EPA’s disapproval of 40 CFR 

51.308(f)(3)(ii) for the Sycamore Canyon 

monitor fails to acknowledge or address 

critical monitoring deficiencies. SRP 

noted that ADEQ’s determination that 

monitor irregularities should preclude 

the site from 40 CFR 51.308(f)(3)(ii)(A) 

requirements, and that the EPA cannot 

ignore the issues. SRP states that ADEQ 

has shown that the site would have 

experienced drastic visibility 

improvements if not for the impact of 

PM, and that the increases of coarse 

mass and soil that occurred after the 

monitor was relocated in 2015 shows 

that the increasing trends of dust at the 

monitor originate from local sources. 

SRP further notes that the current 

monitor location is not within the Class 

I area, so it is unreasonable to assume 

the local dust impacts experienced at 

the monitor result in visibility 

degradation within the Class I area. SRP 

asserts that the EPA’s current 

disapproval deprives the public of an 

adequate opportunity to comment as the 

EPA fails to discuss the monitoring 

irregularities at the monitor. SRP claims 

that the EPA’s disapproval of 40 CFR 

51.308(f)(3)(ii) is arbitrary and 

capricious because the action ignores 

the facts presented by ADEQ, ADEQ’s 

recommendation that the SYCA monitor 

should not be used for long-term 

progress analysis, and instead relies on 

questionable monitoring data without 

any discussion of its merits. 

Response E.7. Please see Response 

B.9. 

Further, we do not agree that we 

ignored ADEQ’s monitoring analysis. 

On the contrary, we specifically 

acknowledged this analysis in our 

proposal.183 However, we found this 

analysis was insufficient to meet the 

requirements of 40 CFR 

51.308(f)(3)(ii)(A), given the flaws in 

ADEQ’s long-term strategy. 

We also disagree with the 

commenter’s assertion that ADEQ 

determined that monitor irregularities 

should preclude the site from 40 CFR 

51.308(f)(3)(ii)(A) requirements. Rather, 

ADEQ asserted that the Plan complied 


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Federal Register / Vol. 89, No. 243 / Wednesday, December 18, 2024 / Rules and Regulations 102769 

184Plan p. 106 (‘‘In accordance with 40 CFR 

51.308(f)(3)(ii)(A), Arizona has provided robust 

documentation in support of the state’s source 

selection criteria and reasonable progress 

determinations for selecting measures for inclusion 

in its long-term strategy.’’) 

186See EPA Legal Tools to Advance 

Environmental Justice, May 2022, available at 

www.epa.gov/system/files/documents/2022-05/ 

EJ%20Legal%20Tools%20May

%202022%20FINAL.pdf at 35–36. 

with these requirements.184 We do not 

agree with this assertion for the reasons 

stated in our proposal and Response B.9 

of this document. ADEQ also noted that 

it will continue to monitor and 

investigate the source of coarse mass 

impacts at the monitor site during 

subsequent progress reports and 

periodic comprehensive Regional Haze 

SIP revisions.185 We will work with 

ADEQ and other stakeholders on the 

consideration of this issue in the 

development of future SIP revisions. 

F. Community Sign-On Letter 

The Community Sign-On Letter is 

supportive with three suggestions for 

improvement. The supportive portions 

of the letter do not require a response. 

Comment F.1. The commenter 

requests that the EPA confirm the 

polluting facilities that ADEQ 

improperly excluded from analysis in 

the state’s plan. 

Response F.1. Please see Response 

A.1, which describes the EPA’s 

approach to reviewing the Plan 

generally and source selection 

specifically. 

Comment F.2. The commenter 

requests that the EPA confirm the 

specific errors in each of the selected 

source’s review of pollution controls. 

Response F.2. We have explained the 

bases for our partial disapproval with 

respect to 40 CFR 51.308(f)(2) in our 

proposal and elsewhere in this 

document. Therefore, the EPA’s 

disapproval of 51.308(f)(2) is justified. 

Comment F.3. The commenter 

requests that the EPA consider the 

equity and environmental justice 

impacts of the state’s plan and 

maximize the environmental justice cobenefits of haze pollution reduction 

opportunities. 

Response F.3. The regional haze 

statutory provisions do not explicitly 

address considerations of environmental 

justice, and neither do the regulatory 

requirements of the second planning 

period in 40 CFR 51.308(f), (g), and (i). 

As explained in ‘‘EPA Legal Tools to 

Advance Environmental Justice,’’ 186 the 

CAA provides states with the discretion 

to consider environmental justice in 

developing rules and measures related 

to regional haze. While a State may 

consider environmental justice under 

the reasonable progress factors, neither 

the statute nor the RHR requires states 

to conduct an environmental justice 

analysis for the EPA to approve a SIP 

submission. Furthermore, the CAA and 

applicable implementing regulations 

neither prohibit nor require such an 

evaluation of environmental justice with 

regard to a regional haze SIP 

submission. The EPA is not identifying 

environmental justice as a basis for its 

decision to partially approve and 

partially disapprove Arizona’s SIP 

revision. 

G. Comment Letter From NPCA et al. 

Sections I (‘‘Background’’) and II 

(‘‘EPA’s Proposed Rule Correctly 

Disapproves ADEQ’s Approach To 

Source Selection, Four-Factor Analyses, 

Control Determinations, and Reasonable 

Progress Goals’’) of the NPCA et al.’s 

comment letter either provide 

background information or are 

supportive and therefore do not require 

a response. We respond to sections III– 

VI of the NPCA et al.’s comment letter 

below. 

Comment G.1. NPCA et al. request the 

EPA to be more specific about the point 

sources of concern. First, the commenter 

states that in the final rule, the EPA 

should list the sources that ADEQ 

improperly screened out and failed to 

conduct a four-factor reasonable 

progress analysis for, namely Apache 

Unit 3. Cholla Units 1, 3–4, Coronado, 

ASARCO Hayden Smelter, LhoistNelson Lime Plant, Apache Nitrogen, 

Freeport-McMoRan Miami Smelter. 

Second, the commenter states that the 

EPA should list each point source for 

which the EPA is disapproving ADEQ’s 

control determinations, namely SGS 

Units 1 and 2 NOX and SO2 analyses, 

SGS 3 and 4 SO2 analyses, IGS 3 and 4 

NOX analyses, Williams Compressor 

Station NOX analysis, Wilcox 

Compressor Station NOX analysis, Drake 

Cement Plant NOX and SO2 analyses, 

and Phoenix Cement-Clarkdale Plant, 

NOX and PM10 analyses. 

Response G.1. See Response A.1. The 

EPA is disapproving long-term strategy 

as a whole. Any subsequent SIP revision 

developed by the State, or FIP 

developed by EPA, will need to 

establish a long-term strategy in 

accordance with the regulatory 

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

Comment G.2. NPCA et al. comment 

that the EPA must consider the equity 

and environmental justice impacts of its 

action on Arizona’s Regional Haze SIP. 

The commenter indicates that the EPA 

guidance documents direct states to 

consider the broader environmental 

implications of their regional haze 

plans, by requiring an analysis of the 

‘‘non-air quality environmental impacts 

of compliance,’’ including 

environmental justice, and that 

meaningful outreach and engagement to 

environmental justice communities is 

crucial. NPCA et al. request ADEQ and 

the EPA to conduct meaningful 

outreach, substantively incorporate 

equity and environmental justice into 

the SIP revision and the supporting 

technical documents, such as preparing 

maps that detail the location of 

environmental justice communities in 

Arizona and the location of nearby 

visibility-impairing sources. The 

commenters specify that a number of 

visibility-impairing sources in Arizona 

are located near vulnerable 

communities, yet ADEQ did not 

conduct a four-factor analysis for many 

of these sources. 

Response G.2. See Response F.3. 

NPCA et al. provided additional 

demographic information for 

communities near several sources in 

Arizona. Without agreeing with the 

particular relevance or accuracy of this 

information, the EPA acknowledges the 

demographic information provided as 

part of the comment. As discussed in 

our proposal and in this document, the 

EPA has evaluated Arizona’s SIP 

submission against the statutory and 

regulatory regional haze requirements 

and determined that it has not satisfied 

certain minimum requirements. 

Comment G.3. NPCA et al. note that 

the EPA must disapprove ADEQ’s 

adjustments to the URP glidepath for 

each Class I area. The commenter asserts 

that the EPA can only approve these 

URP glidepath adjustments if it 

determines ADEQ used ‘‘scientifically 

valid data and methods’’ per 40 CFR 

51.308(f)(1)(vi)(B), and they request the 

EPA to disapprove ADEQ’s URP 

glidepath adjustments for two reasons. 

First, NPCA et al. state that the EPA 

incorrectly suggests that ADEQ’s 

adjustments were de minimis and had 

no effect on whether the RPGs for each 

Class I area are above or below the URP 

glidepath. However, ADEQ’s decision to 

adjust the default URP glidepaths 

significantly affected whether the RPG 

for several Class I areas are above or 

below the glidepath, such as Chiricahua 

Wilderness, Saguaro National Park, and 

Superstition Wilderness. 

Second, NPCA et al. state that the 

EPA’s determination that ADEQ’s 

glidepath adjustments used 

scientifically valid data and methods is 

unsound given that the EPA previously 

expressed concerns with these data and 

methods. The commenter further states 

that the EPA highlighted substantial 

problems in its 2019 Modeling 


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102770 Federal Register / Vol. 89, No. 243 / Wednesday, December 18, 2024 / Rules and Regulations 

187Memorandum 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. 

188 2019 Modeling TSD, p. 37. 

189 2019 Modeling TSD, p. 67. 

190 89 FR 47398, 47402, n. 52. 

191See, e.g., 82 FR 3078, 3093 and 89 FR 47398, 

47402, n. 52. 

192 89 FR 47398, 47411 (emphasis added). 

193 89 FR 47398, 47432–47433. 

194 2022 Arizona Regional Haze Plan, p. D–24 and 

Figure D–39. 

195 2019 modeling TSD, p. 55. 

196 2019 modeling TSD, p. 56, Table 5–2. 

197 89 FR 47398, 47411. 

198 89 FR 47398, 47403; 2021 Clarifications 

Memo, Sections 2 and 2.1. 

199See 40 CFR 51.308(f)(2)(i) (‘‘. . . The State 

must include in its implementation plan a 

description of the criteria is used to determine 

which sources or groups of sources it evaluated and 

how the four factors were taken into consideration 

Technical Support Document (TSD) 187

with available data and methods for 

adjusting Class I glidepaths based on 

both international and prescribed 

wildland fire emissions, including 

international emissions data from just a 

single year,188 and uncertainty in many 

of the calculations and modeling and 

ambient data.189

Response G.3. As noted in our 

proposal and in our response to 

Comment C.5, being on or below the 

URP does not relieve a state from 

considering the four statutory factors to 

determine what level of control is 

needed to achieve reasonable 

progress.190 The URP is used in later 

steps of the reasonable progress analysis 

for informational purposes and to 

provide a non-enforceable benchmark 

against which to assess a Class I area’s 

rate of visibility improvement. 

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.191

We also find that the specific points 

raised by NPCA are overstated, and we 

therefore disagree that we should 

disapprove ADEQ’s glidepath 

adjustments. First, the EPA’s proposal 

stated, ‘‘[t]he choice of adjustment 

option made no difference in whether 

the RPG for each area was above or 

below its URP glidepath,’’ 192 not that an 

adjustment, in general, made no 

difference. That is, the glidepath 

adjustment results were nearly the same 

between the option that adjusted for 

international anthropogenic impacts 

alone, and the option that adjusted for 

international impacts together with 

wildland prescribed fire impacts. The 

commenter is correct that for several 

Class I areas, the adjustment itself does 

make a difference in the assessment of 

whether projected visibility impacts are 

above or below the glidepath. Our 

assessment of the URP and RPGs took 

that into account, as noted in our 

proposal.193 If the adjustment were 

rejected altogether, that would 

strengthen the case for the need for the 

State to make a ‘‘robust demonstration’’ 

that there are no reasonable additional 

emissions reduction measures, although 

in this case that need is already 

established because Sycamore Canyon 

Wilderness impacts are above its 

glidepath with or without 

adjustment.194

Second, the EPA disagrees that the 

glidepath adjustments were not based 

on scientifically valid data and 

methods. The 2019 Modeling TSD 

acknowledges various limitations and 

uncertainties in various model inputs 

and calculation approaches, which is 

always the case in modeling. That 

acknowledgement was not intended as 

an assertion by the EPA that its own 

data and methods were scientifically 

invalid. Similarly, it was not intended 

that a glidepath adjustment made using 

the same or similar methods would not 

be based on scientifically valid data and 

methods. Rather, the data and methods 

used were the best available to the EPA 

at the time of the modeling in that TSD, 

and presented as a reasonable and valid 

approach for glidepath adjustment that 

states could consider in developing 

their SIPs, without precluding the use of 

better data and methods that a state 

might develop. The EPA’s specific 

statement about ‘‘uncertainty in many of 

the calculations and modeling and 

ambient data’’ was in the context of 

alternative approaches to adjusting the 

glidepath, for which the 2019 Modeling 

TSD provided five,195 including the 

default. Those approaches differed in 

whether international impacts and 

prescribed fire should be combined with 

the baseline model run on an absolute 

or relative basis (i.e., simply added in or 

applied as a percent difference), and 

whether natural conditions should be 

estimated from monitored data or from 

modeling. There is not one clearly best 

approach that would be most 

appropriate for all Class I areas in the 

country, but the EPA chose one as the 

default and provided a range of 

adjustment results. For Arizona Class I 

areas, the glidepath adjustment in the 

default approach was nearly the same as 

the maximum among the approaches 

examined, except for the Grand Canyon 

and Sycamore Canyon Wilderness, 

where it gave closer to the minimum 

adjustment among the approaches 

considered.196 As noted in the EPA’s 

proposal, the WRAP results used by 

ADEQ were fairly close to default 

approach values estimated by the EPA 

and were determined to be based on 

scientifically valid data and methods.197

The EPA does not find any reason, and 

the commenters do not provide any 

additional reasons to determine 

otherwise. 

Comment G.4. NPCA et al. indicate 

that the EPA must disapprove 

additional aspects of ADEQ’s source 

selection process, noting that ADEQ’s 

Q/d threshold of 10 is arbitrarily high, 

ADEQ should not have eliminated the 

totality of ‘‘effectively-controlled’’ 

process emissions from its Q/d analysis, 

and ADEQ’s ‘‘de minimis point source 

process determination’’ is arbitrary and 

capricious. 

Response G.4. As explained in our 

proposal and the 2021 Clarifications 

Memo, the RHR does not require states 

to consider controls for all sources, all 

source categories, or any or all sources 

in a particular source category.198

Rather, the states have discretion to 

choose any source selection 

methodology or threshold that is 

reasonable, but the choices they make 

must be explained and should be 

designed to result in a set of sources 

which capture a meaningful portion of 

the state’s total contribution to visibility 

impairment. To this end, 40 CFR 

51.308(f)(2)(i) requires that a state’s SIP 

submission must 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). 

Overall, in this particular instance, 

the EPA finds that that many aspects of 

ADEQ’s source selection process, such 

as its focus on sulfate, nitrate, and 

coarse mass and its use of a Q/d value 

of 10 for point sources, were reasonable 

and adequately explained and 

documented. However, we also find that 

ADEQ did not provide an adequate 

justification for screening out certain 

sources and units from conducting a 

four-factor analysis on the basis that 

they are ‘‘effectively controlled’’ as part 

of its source selection process.199 As the 


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in selecting the measures for inclusion in its longterm strategy’’). 

200 2021 Clarifications Memo, p. 3. 

201 89 FR 47398, 47429. 

EPA has previously stated, ‘‘[s]ource 

selection is a critical step in states’ 

analytical processes. All subsequent 

determinations of what constitutes 

reasonable progress flow from states’ 

initial decisions regarding the universe 

of pollutants and sources they will 

consider for the second planning 

period.’’ 200 Therefore, Arizona’s source 

selection methodology, including 

unjustified effectively controlled 

determinations, supports the EPA’s 

determination that Arizona’s long-term 

strategy did not include all measures 

necessary to make reasonable progress. 

Therefore, EPA’s disapproval of 40 CFR 

51.308(f)(2), as a whole, is reasonable. 

Comment G.5. NPCA et al. state that 

ADEQ’s average cost-effectiveness 

threshold is too low, and requests the 

EPA to further clarify that ADEQ’s 

$6,500 per ton cost threshold is too low 

and unreasonably excludes costeffective control measures. 

Response G.5. While the EPA is not 

disapproving ADEQ’s cost threshold, we 

nonetheless find that the State did not 

apply this threshold in a consistent and 

reasonable manner, as described in our 

proposal 201 and Response D.4 of this 

document. 

Comment G.6. NPCA et al. comment 

that the EPA must promptly issue a 

Regional Haze FIP for Arizona. The 

commenter recommends that to provide 

sufficient time for sources to implement 

control measures before the second 

implementation period ends in 2028, 

the EPA should issue a proposed FIP in 

2024 and finalize the FIP by the end of 

2025. 

Response G.6. Disapproving a SIP 

submission 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. The EPA is not proposing 

a FIP for the disapproved requirements 

of the 2022 Arizona Regional Haze Plan 

at this time. 

III. Final Action 

Under CAA section 110(k)(3), and 

based on the evaluation and rationale 

presented in the proposed rule and this 

final rule, the EPA is partially approving 

and partially disapproving the 2022 

Arizona Regional Haze Plan. 

Specifically, the EPA is approving the 

elements of the 2022 Arizona Regional 

Haze Plan related to requirements 

contained in 40 CFR 51.308(f)(1), (f)(4)– 

(6), and (g)(1)–(5). The EPA is 

disapproving the elements of the 2022 

Arizona Regional Haze Plan related to 

requirements contained in 40 CFR 

51.308(f)(2), (f)(3), and (i)(2)–(4). 

Further, the EPA is disapproving the 

interstate transport requirements of 

CAA section 110(a)(2)(D)(i)(II) prong 4 

(visibility) for the 2018 Ozone I–SIP 

submittal and 2015 PM2.5 I–SIP 

submittal. 

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) 

starts a sanctions clock. Arizona’s 2022 

Regional Haze Plan, 2018 Ozone I–SIP 

submittal, and 2015 PM2.5 I–SIP 

submittal were not submitted to meet 

any of these requirements. Therefore, 

the disapprovals noted in section III.B 

will 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. We anticipate that any 

SIP or FIP that remedies the 

disapprovals with respect to Regional 

Haze requirements, would also, in 

conjunction with the existing Arizona 

Regional Haze FIP, remedy the 

disapproval for the interstate transport 

visibility requirement of CAA section 

110(a)(2)(D)(i)(II) for the 2018 Ozone I– 

SIP submittal and 2015 PM2.5 I–SIP 

submittal. 

IV. 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. 

42 U.S.C. 7410(k); 40 CFR 52.02(a). 

Thus, in reviewing SIP submissions, the 

EPA’s role is to review state choices, 

and approve those choices if they meet 

the minimum criteria of the Act. 

Accordingly, this final action partially 

approves and partially disapproves 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 


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102772 Federal Register / Vol. 89, No. 243 / Wednesday, December 18, 2024 / Rules and Regulations 

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 partially approves and 

partially disapproves 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. 

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, 

Feb. 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 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. 

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. 

K. Congressional Review Act (CRA) 

This action is subject to the CRA, and 

the EPA will submit a rule report to 

each House of the Congress and to the 

Comptroller General of the United 

States. This action is not a ‘‘major rule’’ 

as defined by 5 U.S.C. 804(2). 

L. Petitions for Judicial Review 

Under section 307(b)(1) of the CAA, 

petitions for judicial review of this 

action must be filed in the United States 

Court of Appeals for the appropriate 

circuit by February 18, 2025. Filing a 

petition for reconsideration by the 

Administrator of this final rule does not 

affect the finality of this rule for the 

purposes of judicial review nor does it 

extend the time within which a petition 

for judicial review may be filed, and 

shall not postpone the effectiveness of 

such rule or action. This action may not 

be challenged later in proceedings to 

enforce its requirements (see section 

307(b)(2)). 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Incorporation by 

reference, Intergovernmental relations, 

Nitrogen oxides, Ozone, Particulate 

matter, Reporting and recordkeeping 

requirements, Sulfur Oxides, Volatile 

organic compounds. 

Dated: December 10, 2024. 

Martha Guzman Aceves, 

Regional Administrator, Region IX. 

For the reasons stated in the 

preamble, the EPA amends chapter I, 

title 40 of the Code of Federal 

Regulations as follows: 

PART 52—APPROVAL AND 

PROMULGATION OF 

IMPLEMENTATION PLANS 

■ 1. The authority citation for part 52 

continues to read as follows: 

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

Subpart D—Arizona 

■ 2. In § 52.120(e), amend Table 1 by 

adding an entry for ‘‘State 

Implementation Plan Revision: Regional 

Haze Program (2018–2028)’’ before the 

entry for ‘‘Arizona State Implementation 

Plan Revision under Clean Air Act 

Section 110(a)(1) and (2); 

Implementation of the 2008 Lead 

National Ambient Air Quality 

Standards, excluding the appendices.’’ 

The addition reads as follows: 

§ 52.120 Identification of plan. 

* * * * * 

(e) * * * 

TABLE 1—EPA-APPROVED NON-REGULATORY AND QUASI-REGULATORY MEASURES

[Excluding certain resolutions and statutes, which are listed in tables 2 and 3, respectively] 1

Name of SIP provision 

Applicable geographic 

or nonattainment area 

or title/subject 

State submittal date EPA approval date Explanation 

The State of Arizona Air Pollution Control Implementation Plan 

Clean Air Act Section 110(a)(2) State Implementation Plan Elements (Excluding Part D Elements and Plans) 

*******

State Implementation Plan Revision: Regional Haze Program (2018–2028), excluding Chapters 2, 6.1, 6.2, 6.3, 

7, 8, 9, and 10 and Appendices B, C, D, E, F, G, H, I, 

J, and L.

State-wide ................... August 15, 2022 .... January 17, 2025.


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Federal Register / Vol. 89, No. 243 / Wednesday, December 18, 2024 / Rules and Regulations 102773 

TABLE 1—EPA-APPROVED NON-REGULATORY AND QUASI-REGULATORY MEASURES—Continued 

[Excluding certain resolutions and statutes, which are listed in tables 2 and 3, respectively] 1

Name of SIP provision 

Applicable geographic 

or nonattainment area 

or title/subject 

State submittal date EPA approval date Explanation 

*******

1Table 1 is divided into three parts: Clean Air Act Section 110(a)(2) State Implementation Plan Elements (excluding Part D Elements and 

Plans), Part D Elements and Plans (other than for the Metropolitan Phoenix or Tucson Areas), and Part D Elements and Plans for the Metropolitan Phoenix and Tucson Areas. 

* * * * * 

■ 3. Section 52.145 is amended by 

adding paragraph (o) to read as follows: 

§ 52.145 Visibility protection. 

* * * * * 

(o) Disapproval. On August 15, 2022, 

the Arizona Department of 

Environmental Quality submitted the 

‘‘State Implementation Plan Revision: 

Regional Haze Program (2018–2028).’’ 

(1) The following portions of the 

‘‘State Implementation Plan Revision: 

Regional Haze Program (2018–2028)’’ 

are disapproved because they do not 

meet the applicable requirements of 

Clean Air Act sections 169A and 169B 

and the Regional Haze Rule in 40 CFR 

51.301 through 51.308. 

(i) Chapters 2, 6.1, 6.2, 6.3, 7, 8, 9, and 

10; 

(ii) Appendices B, C, D, E, F, G, H, I, 

J, and L. 

■ 4. Section 52.147 is amended by 

adding paragraph (f) to read as follows: 

§ 52.147 Interstate transport. 

* * * * * 

(f) Disapproval. The SIPs submitted 

on December 11, 2015 and September 

24, 2018 do not meet the requirements 

of Clean Air Act section 

110(a)(2)(D)(i)(II) (interfere with 

measures in any other state to protect 

visibility, only) for the 2012 PM2.5

NAAQS and the 2015 ozone NAAQS, 

respectively. 

[FR Doc. 2024–29508 Filed 12–17–24; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Parts 68, 372, 703, 720, 721, 

723, 725, and 761 

[EPA–HQ–OPPT–2022–0902; FRL–7906–02– 

OCSPP] 

RIN 2070–AK65 

Updates to New Chemicals 

Regulations Under the Toxic 

Substances Control Act (TSCA) 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Final rule. 

SUMMARY: The Environmental Protection 

Agency (EPA or the Agency) is 

amending the new chemicals procedural 

regulations under the Toxic Substances 

Control Act (TSCA). These amendments 

align the regulatory text with the 

amendments to TSCA’s new chemicals 

review provisions contained in the 

Frank R. Lautenberg Chemical Safety for 

the 21st Century Act, enacted on June 

22, 2016, will improve the efficiency of 

EPA’s review processes, and update the 

regulations based on existing policies 

and experience implementing the New 

Chemicals Program. This final rule 

includes amendments that will increase 

the quality of information initially 

submitted in new chemicals notices and 

improve the Agency’s processes for 

timely, effective completion of 

individual risk assessments and the new 

chemicals review process overall. EPA 

is also finalizing several amendments to 

the regulations for low volume 

exemptions (LVEs) and low release and 

exposure exemptions (LoREXs), which 

will require EPA approval of an 

exemption notice prior to 

commencement of manufacture, make 

per- and polyfluoroalkyl substances 

(PFAS) categorically ineligible for these 

exemptions, and provide that certain 

persistent, bioaccumulative, toxic (PBT) 

chemical substances are ineligible for 

these exemptions. 

DATES: This final rule is effective 

January 17, 2025. 

ADDRESSES: The docket for this action, 

identified by docket identification (ID) 

number EPA–HQ–OPPT–2022–0902, is 

available online at https://

www.regulations.gov. Additional 

instructions for visiting the docket, 

along with more information about 

dockets generally, is available at https:// 

www.epa.gov/dockets. 

FOR FURTHER INFORMATION CONTACT: For 

technical information contact: Tyler 

Lloyd, New Chemicals Division 

(7405M), Office of Pollution Prevention 

and Toxics, Environmental Protection 

Agency, 1200 Pennsylvania Ave. NW, 

Washington, DC 20460–0001; telephone 

number: (202) 564–4016; e-mail address: 

lloyd.tyler@epa.gov. 

For general information contact: The 

TSCA-Hotline, ABVI-Goodwill, 422 

South Clinton Ave., Rochester, NY 

14620; telephone number: (202) 554– 

1404; e-mail address: TSCA-Hotline@

epa.gov. 

SUPPLEMENTARY INFORMATION: 

I. Executive Summary 

A. Does this action apply to me? 

You may be potentially affected by 

this action if you intend to manufacture 

a new chemical substance, or 

manufacture or process a chemical 

substance for a significant new use. The 

following list of North American 

Industrial Classification System 

(NAICS) codes is not intended to be 

exhaustive, but rather provides a guide 

to help readers determine whether this 

document applies to them. Potentially 

affected entities may include: 

• Chemical Manufacturers (NAICS 

code 325). 

• Petroleum and Coal Products 

(NAICS code 324). 

• Merchant Wholesalers, Nondurable 

Goods (NAICS code 424). 

This list details the types of entities 

that EPA is aware could potentially be 

regulated by this action. Other types of 

entities not listed could also be 

regulated. To determine whether your 

entity is regulated by this action, you 

should carefully examine the 

applicability criteria found in 40 CFR 

720.22, 721.5, 723.50, and 725.1. If you 

have questions regarding the 

applicability of this action, please 

consult the technical person listed 

under FOR FURTHER INFORMATION

CONTACT. 

B. What is the Agency’s authority for 

taking this action? 

EPA is promulgating this rule 

pursuant to its authority in TSCA 

section 5 (15 U.S.C. 2604). Section 

5(a)(1) of the Toxic Substances Control 

Act (TSCA), 15 U.S.C. 2604(a)(1), as 

amended by the Frank R. Lautenberg 

Chemical Safety for the 21st Century 

Act of 2016 (Pub. L. 114–182) (herein 

referred to as the ‘‘2016 Lautenberg 


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