Federal Register / Vol. 89, No. 245 / Friday, December 20, 2024 / Rules and Regulations 104043 

1Specifically: 30 Texas Administrative Code 

(TAC) 111.111 (originally adopted as Texas Air 

Control Board (TACB) Regulation I, Rule 103), 

which limits opacity; and 30 TAC 111.153(b) 

(originally adopted as TACB Regulation I, Rule 

105.31), which limits particulate matter emissions 

from solid fuel fired-steam generators to 0.3 lbs/ 

million Btu averaged over a two-hour period. TACB 

Regulation I, Rules 103 and 105.31 were approved 

by EPA on May 31, 1972 (37 FR 10895); these rules 

were subsequently revised (amendments most 

recently approved May 8, 1996 (61 FR 20732), and 

April 28, 2009 (74 FR 19144)), which renumbered 

and recodified these rules to what they are today. 

■ 3. Amend § 4044.58 by revising table 

1 to § 4044.58 to read as follows: 

§ 4044.58 Tables used to determine 

expected retirement age. 

* * * * * 

TABLE 1 TO § 4044.58—TABLE I–25—SELECTION OF RETIREMENT RATE CATEGORY

[For valuation dates in 2025 1] 

If participant 

reaches URA in 

year— 

Participant’s retirement rate category is— 

Low 2 if monthly 

benefit at URA 

is less than— 

Medium 3 if monthly benefit 

at URA is— High 4 if monthly 

benefit at URA is 

greater than— From— To— 

2026 ......................................................................................... 825 825 3,486 3,486 

2027 ......................................................................................... 844 844 3,566 3,566 

2028 ......................................................................................... 864 864 3,648 3,648 

2029 ......................................................................................... 884 884 3,732 3,732 

2030 ......................................................................................... 904 904 3,818 3,818 

2031 ......................................................................................... 925 925 3,906 3,906 

2032 ......................................................................................... 946 946 3,996 3,996 

2033 ......................................................................................... 968 968 4,088 4,088 

2034 ......................................................................................... 990 990 4,182 4,182 

2035 or later ............................................................................ 1,013 1,013 4,278 4,278 

1Applicable tables for valuation dates before 2025 are available on PBGC’s website (www.pbgc.gov). 2Table II–A. 

3Table II–B. 

4Table II–C. 

* * * * * 

Issued in Washington, DC. 

Hilary Duke, 

Assistant General Counsel for Regulatory 

Affairs Pension Benefit Guaranty 

Corporation. 

[FR Doc. 2024–29105 Filed 12–19–24; 8:45 am] 

BILLING CODE 7709–02–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R06–OAR–2021–0029; FRL–12218– 

02–R6] 

Air Plan Disapproval; Texas; Control of 

Air Pollution From Visible Emissions 

and Particulate Matter 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Final rule. 

SUMMARY: Pursuant to the Federal Clean 

Air Act (CAA, the Act), the 

Environmental Protection Agency (EPA) 

is disapproving a revision to the Texas 

State Implementation Plan (SIP) 

submitted by the State of Texas through 

the Texas Commission on 

Environmental Quality (TCEQ) on 

August 20, 2020 (2020 SIP revision). 

The 2020 SIP revision addresses 

emissions during planned Maintenance, 

Startup and Shutdown (MSS) activities 

for certain Electric Generating Units 

(EGUs) and includes requirements 

intended to address visible emissions 

(opacity) and Particulate Matter (PM) 

emissions during planned MSS 

activities. The requirements are 

included in eight Agreed Orders (AOs) 

issued by TCEQ to the affected EGUs 

and provided in the 2020 SIP revision. 

EPA determined that the requirements 

contained in these AOs do not meet the 

CAA enforceability requirements or the 

CAA requirement that emission 

limitations must apply on a continuous 

basis. We are taking this action in 

accordance with section 110 of the Act. 

DATES: This rule is effective on January 

21, 2025. 

ADDRESSES: The EPA has established a 

docket for this action under Docket ID 

No. EPA–R06–OAR–2021–0029. All 

documents in the docket are listed on 

the https://www.regulations.gov 

website. Although listed in the index, 

some information is not publicly 

available, e.g., Confidential Business 

Information or other information whose 

disclosure is restricted by statute. 

Certain other material, such as 

copyrighted material, is not placed on 

the internet. Publicly available docket 

materials are available electronically 

through https://www.regulations.gov. 

FOR FURTHER INFORMATION CONTACT: 

Michael Feldman, Regional Haze and 

SO2 Section, EPA Region 6 Office, 1201 

Elm Street, Suite 500, Dallas, Texas 

75270, (214) 665–9793, 

Feldman.Michael@epa.gov. Please call 

or email the contact listed above if you 

need alternative access to material 

indexed but not provided in the docket. 

SUPPLEMENTARY INFORMATION: 

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

and ‘‘our’’ means the EPA. 

I. Background and Summary of Bases 

for Disapproval 

The background for this action is 

discussed in detail in our September 3, 

2024, proposal (89 FR 71237). In that 

document, we proposed to disapprove a 

revision to the SIP submitted by the 

State of Texas through the TCEQ on 

August 20, 2020, that addresses 

emissions during planned MSS 

activities for specified EGUs and 

includes requirements intended to 

address visible emissions (opacity) and 

PM emissions during planned MSS 

activities at these specified EGUs. 

The 2020 SIP revision and included 

AOs were intended to address concerns 

regarding the applicability of two long 

standing Texas rules during periods of 

MSS.1 Texas included in the 2020 SIP 

revision the State’s interpretation of 

these rules, taking the position that the 

numerical opacity and PM limits have 

never applied to coal fired EGUs using 

ESPs during periods of MSS because of 


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2See letter, from Steve Hagle, Deputy Director, 

Office of Air, TCEQ to Gina McCarthy, 

Administrator, EPA, dated December 2, 2015 

(setting forth TCEQ’s interpretation that the opacity 

and PM emission limitations in 30 TAC 111.111 

and 30 TAC 111.153(b) never applied to periods of 

planned MSS activities at coal-fired EGUs equipped 

with ESPs as a control device). 

the technical limitations on the control 

technology. This interpretation was first 

provided by TCEQ in 2015 as part of a 

Title V action; 2 this is the first time the 

interpretation has been included as part 

of a SIP revision. The State’s regulatory 

language contains no indication that the 

rules do not apply to this specific subset 

of sources during MSS. 

In the instant SIP revision, Texas 

provided Agreed Orders that contain 

operational requirements and work 

practices that would apply during 

periods of MSS at EGU’s equipped with 

ESPs. Texas also provided historic 

ambient particulate matter monitoring 

data, explaining that even though under 

its interpretation, these rules have never 

applied during MSS, there have not 

been any violations of PM NAAQS 

measured anywhere near these sources. 

EPA has considered three interrelated 

provisions of the Clean Air Act (CAA) 

in assessing the approvability of this SIP 

submission. First, the requirement 

under CAA section 110(a)(2)(A) which 

requires that SIPs include ‘‘enforceable 

emission limitations and other control 

measures, means, or techniques 

(including economic incentives such as 

fees, marketable permits, and auctions 

of emissions rights), as well as 

schedules and timetables for 

compliance, as may be necessary or 

appropriate to meet the applicable 

requirements of this chapter.’’ 

Second, under CAA section 302(k), 

‘‘emission limitation’’ and ‘‘emission 

standard’’ mean a requirement 

established by the State or the 

Administrator which limits the 

quantity, rate, or concentration of 

emissions of air pollutants on a 

continuous basis, including any 

requirement relating to the operation or 

maintenance of a source to assure 

continuous emission reduction, and any 

design, equipment, work practice or 

operational standard promulgated under 

this chapter. 

Finally, 110(l) provides that the 

Administrator shall not approve a 

revision of a plan if the revision would 

interfere with any applicable 

requirement concerning attainment and 

reasonable further progress (as defined 

in section 7501 of this title), or any 

other applicable requirement of this 

chapter. 

In our September 3, 2024, proposal 

(89 FR 71237), we proposed disapproval 

of this SIP revision because these AOs 

were not enforceable as required by 

CAA section 110 and did not provide 

for continuous limitation of emissions 

as required by CAA section 302(k). Our 

review under 302(k) in the proposed 

action was based on language in the SIP 

revision that seems to clearly indicate 

the reason Texas submitted these agreed 

orders was to make these MSS 

requirements federally enforceable so 

that emission limitations apply on a 

continuous basis as required under 

302(k). As discussed in detail in the 

response to comments, Texas provided 

comments on our proposed action 

indicating that it did not intend that 

these emission restrictions be 

considered emission limits as defined 

by Section 302. 

After careful review of all comments, 

we are finalizing our disapproval. We 

are finding that the agreed orders are not 

enforceable as required by 110(a)(2)(A). 

The rules are not enforceable because 

the requirements do not clearly demark 

as to when start up ends and 

compliance with the 30 TAC chapter 

111 numerical limits is required, and 

during startup and shutdown, the work 

practice requirements for when an ESP 

must be engaged or removed from 

service are overly vague and do not 

define specific conditions to identify 

when and what steps must be followed 

to engage and operate the ESPs during 

these events. For periods of 

maintenance, the only requirement is to 

follow good air pollution control 

practices and safe operating practices. 

We are also determining that it is 

necessary or appropriate for these 

measures to be considered emission 

limitations as defined by 302(k) and 

thus must be continuous. Clearly this is 

supported by the explanation 

accompanying the SIP submission that 

indicated this revision was provided to 

make the limits continuous under 

302(k). Texas commented, however, on 

our proposed action that it was not its 

intent that these agreed orders be 

considered as emission limitations. As 

discussed fully in our comment 

response on this matter, EPA disagrees. 

First, Texas indicates these limits are 

used in the permitting context to 

implement BACT which under the 

States and EPA definition of BACT must 

be continuous. Second, these AOs as 

written would allow for emissions that 

could threaten the State’s ability to 

comply with the requirements of the 

CAA, and the NAAQS in particular. 

Given that on a lbs/hour basis, these 

MSS emissions can be much higher than 

emissions during normal controlled 

operation, it is necessary and 

appropriate that measures be in place to 

provide for attainment and maintenance 

of the NAAQS. This conclusion is 

supported by modeling evidence 

provided by a commenter which 

suggests that, in fact, uncontrolled 

emissions during MSS could result in 

violations of the PM NAAQS. 

We are finding that the Agreed Orders 

do not provide for continuous emission 

limitation as required by 302(k). During 

MSS, the AOs have various 

requirements intended to limit the 

duration of the MSS though as 

discussed in our proposal and further in 

the response to comments, the limits on 

duration are often not clearly defined 

and thus not practical to enforce. 

Moreover, all of the AOs allow during 

this time period for coal to be burned for 

a time period which the ESP is not 

operating with no actual limitation on 

quantity, rate or concentration either 

through a numeric limit or clearly 

defined work practice that would affect 

emissions. Effectively, the emission 

limitation is not continuous. 

EPA is not basing its disapproval on 

110(l), but we do note that the modeling 

provided by one commenter 

convincingly indicates that the 

monitoring evidence provided in the 

SIP revision is not sufficient to show 

that the SIP revision does not interfere 

with attainment or maintenance of the 

NAAQS. It is clear from the modeling 

that potential impacts from MSS 

activities would occur much closer to 

the affected facilities than the monitors 

upon which Texas’ demonstration is 

based. A future SIP revision to address 

this disapproval would likely need to 

include modeling to provide evidence 

that the NAAQs is protected in areas in 

closer proximity to the affected 

facilities. 

Finally, EPA is cognizant of the 

technical issues with ESPs that impact 

their effectiveness at lower 

temperatures. Still, two commenters 

both indicated that to comply with 

EPA’s Mercury and Air Toxics 

Standards (MATS) rule, they do not fire 

coal until the ESP is energized. While 

these requirements are not in this SIP 

revision, EPA believes that there may be 

a solution that can be built, hopefully to 

avoid duplicative SIP and MATs 

requirements and ensuring both NAAQS 

and Air Toxics requirements are met. 

We look forward to discussions with the 

State and affected operators to resolve 

these long outstanding issues. 

II. Response to Comments 

The comment period for the proposed 

action closed on October 3, 2024. We 

received comments on our proposal 

from several commenters. This section 

contains the EPA’s response to the more 


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3EPA is only required to consider those 

comments that are received during the comment 

period; however, it is within EPA’s discretion to 

consider comments received after the close of the 

comment period. 

4Basic Information About Air Quality SIPs, 

https://www.epa.gov/air-quality-implementationplans/basic-information-about-air-quality-sips (last 

updated January 20, 2023). 

5Commenter’s reference to TACB Rule 12.2 is 

unavailing for similar reasons. As part of the 

preamble to EPA’s approval, the Agency 

specifically stated the following: ‘‘Several State 

plans include regulations under which an owner or 

operator could be exempt from compliance with an 

applicable emission limitation if he can show that 

emissions from the source will not interfere with 

the attainment or maintenance of the national 

standards. The Administrator neither approves nor 

disapproves such optional control features. States 

are advised, however, that action taken to allow any 

such exemptions will constitute revision of a State 

plan and therefore will be subject at that time to the 

Administrator’s approval.’’ 37 FR 10842, 10845 

(May 31, 1972). In other words, Rule 12.2 may have 

established a process for Texas and then EPA to 

approve exemption provisions that comply with the 

CAA (i.e. through the SIP submission process) but 

did not establish any exemptions from TAC 111 

limits on its own. 

significant comments regarding the 

EPA’s proposed action. For responses to 

all comments received see the Response 

to Comments Document (RTC) available 

in the docket for this action. We 

received two comments after the close 

of the comment period. We fully 

address those comments in the RTC 

document available in the docket for 

this action.3 After careful consideration 

of all comments received, we are 

finalizing this action as proposed. 

A. General Comments on EPA’s Bases 

for Disapproval 

Comment: Some commenters argue 

that the proposed disapproval by the 

EPA relies on principles that lack a 

valid basis in the Clean Air Act (CAA), 

specifically citing Sections 110(a)(2)(A) 

and 302(k) regarding enforceable 

emission limitations. Certain 

commenters, including NSSGA and 

Luminant, urge the EPA to withdraw its 

disapproval and approve the Texas SIP 

provisions, arguing that the proposal is 

inconsistent with CAA principles and 

relevant judicial decisions. One 

commenter (Sierra Club) supports EPA’s 

proposed disapproval and agrees that 

the 2020 SIP revision violates the CAA. 

Response: EPA disagrees with the 

comments that our proposed 

disapproval at issue here relies on 

principles that lack a valid basis in the 

CAA and is inconsistent with CAA 

principles and relevant judicial 

decisions. States have discretion 

regarding how best to meet their 

obligations to implement, attain, 

maintain, and enforce the NAAQS, as 

long as they meet applicable statutory 

and regulatory requirements. A State’s 

SIP submission to address attainment, 

maintenance, and enforcement of the 

NAAQS or other SIP requirements can 

include a wide variety of types of 

provisions, such as: source-specific 

emissions limitations and associated 

monitoring, recordkeeping, and 

reporting; applicable State or local rules 

(or State laws) regarding controls on 

sources or categories of sources; other 

local or State commitments to undertake 

certain activities; and non-regulatory 

supporting information.4 The EPA 

evaluates and acts on SIP submissions 

on a case-by-case basis through notice 

and comment rulemaking. The Agency 

reviews each submission against the 

applicable CAA requirements for that 

particular submission, which can vary 

based on program requirements and the 

relevant NAAQS. 

In the Supreme Court’s recent 

decision in Loper Bright, the Court 

recognized that Congress may delegate 

(and often has delegated) discretionary 

authority to agencies. See Loper Bright 

Enters. v. Raimondo, 144 S. Ct. 2244, 

2268 (2024). Applicable to this action, 

Congress has delegated to EPA the 

responsibility and authority to approve 

or deny SIP submittals. Section 

110(k)(3) of the Clean Air Act (CAA) 

states, in relevant part, that a ‘‘plan 

revision shall not be treated as meeting 

the requirements of this chapter until 

the Administrator approves the entire 

plan revision as complying with the 

applicable requirements of this 

chapter.’’ Further, section 110(l) of the 

CAA states that EPA ‘‘shall not approve 

a revision of a plan if the revision would 

interfere with any applicable 

requirement concerning attainment and 

reasonable further progress . . . , or any 

other applicable requirement of this 

chapter.’’ Here, the State submitted the 

AOs as site specific SIP requirements 

that the EPA evaluated for compliance 

with the CAA. For the reasons described 

at length in other responses, the 

proposal, and the final rulemaking, this 

SIP submission does not comply with 

the CAA, and thus EPA’s disapproval is 

appropriate. 

B. Comments on Applicability of the 

Rules in 30 TAC 111 

Comment: A number of commenters 

indicate that the limits in Title 30, 

Texas Administrative Code, Chapter 111 

(30 TAC 111) have never applied during 

MSS to EGUs controlled by electrostatic 

precipitators (ESPs). Some commenters 

point out that EPA acknowledged in the 

proposal preamble that the technical 

features of ESPs make it unlikely these 

sources can comply during MSS 

operations with the numerical limits 

laid out in 30 TAC 111. Commenters 

take issue with the fact that the proposal 

also points out that there is no textual 

indication in the language of the 

regulations that the rules do not apply 

to power plants controlled by ESPs 

during MSS. One commenter points out 

that the statement ignores parallel 

provisions establishing exemptions for 

MSS periods, such as Texas Air Control 

Board Rule 12.2 (1972), which TCEQ 

has consistently presented to EPA at 

each stage of the dialogue, and states 

that EPA’s observation about the 

immediate text of Chapter 111 at best 

elevates form over substance, and as a 

disapproval basis, such an approach is 

clearly impermissible. 

Response: The EPA disagrees with the 

commenters’ assertions that the 

applicability of the rules in 30 TAC 111 

has been clear. The first time that TCEQ 

explained with any clarity that these 

rules never applied to periods of 

planned MSS activities at coal-fired 

EGUs equipped with ESPs as a control 

device was in an interpretive letter 

dated December 2, 2015, from Steve 

Hagle, Deputy Director, Office of Air, 

TCEQ to Gina McCarthy, Administrator, 

EPA, (2015 interpretive letter). The 2015 

interpretive letter was developed as part 

of a Title V proceeding. The 2020 SIP 

revision is the first time that Texas 

presented its interpretation with clarity 

as part of a SIP revision and attempted 

to define the time period allowed for 

MSS in the SIP and, by extension, the 

time period for when the rules in 30 

TAC 111 do not apply. Although TCEQ 

issued these sources MSS permits to 

authorize these emissions during the 

time period of MSS and the permits 

have conditions addressing the length of 

time allowed for MSS, a permit cannot 

revise the SIP.5

In the proposal, EPA did not take a 

position on whether the rule previously 

applied during MSS to power plants 

controlled by ESPs. Instead, we 

evaluated the 2020 SIP revision as 

necessary, under the State’s 

interpretation and as described in the 

SIP revision, to make the emission 

limits continuous and federally 

enforceable. As discussed elsewhere, we 

do not believe the AOs are enforceable 

or provide for continuous limitations on 

emissions. We believe a SIP revision is 

necessary under TCEQ’s interpretation, 

to clearly define the time period of 

allowed MSS, to provide for continuous 

emission limitations, and to ensure the 

work practices or other limitations that 

apply during periods of MSS are 

enforceable. In addition, based on the 

modeling that was provided in 

comments on this action, it does not 

appear that an interpretation that 


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6See 80 FR. at 33877–33879 for a lengthier 

discussion of the Train v. Natural Resource Defense 

Council line of cases and how the Supreme Court 

views EPA’s role as more than ministerial in 

approving SIPs and also views CAA 110(a)(2)(A) as 

imposing more requirements than simply whether 

or not the SIP leads to NAAQS attainment and 

maintenance. 

7Environ. Comm. Fl. Elec. Power v. EPA, 94 F.4th 

at 101. The Supreme Court has affirmed that a 

measure of discretion is due to federal agencies 

when they are empowered to ‘‘regulate subject to 

the limits imposed by a term or phrase that leaves 

agencies with flexibility, such as ‘appropriate’ or 

‘reasonable.’ ’’ Loper Bright, 144 S. Ct. at 2263. The 

type of statutory language in CAA section 

110(a)(2)(A) (‘‘as may be necessary or appropriate 

to meet the applicable requirements of this chapter 

. . .’’) is squarely within the type of language the 

Supreme Court was referring to that allows EPA to 

take the ultimate discretionary role in determining 

what is ‘‘necessary or appropriate.’’ 

8Letter from Guy Donaldson, Associate Director, 

Air Branch, Air and Radiation Division, EPA to 

Steve Hagle, Deputy Director, Office of Air, TCEQ, 

dated March 13, 2017, and June 7, 2017 return letter 

from Steve Hagle. Included in the docket for this 

action. 

indicates the rules in 30 TAC 111 do not 

apply during MSS is protective of the 

NAAQS. A future SIP revision will need 

to demonstrate, consistent with CAA 

section 110(l), that the limitations or 

work practices included in the revision 

are protective of the NAAQS. 

C. Comments on EPA Authority 

Comment: A number of commenters 

claim that EPA exceeded its authority in 

evaluating the AOs as emission 

limitations in contradiction of the D.C. 

Circuit’s opinion in Environmental 

Committee of the Florida Electric Power 

Coordinating Group, Inc. v. EPA, 94 

F.4th 77 (D.C. Cir. 2024). The 

commenters point out that the Clean Air 

Act grants States primary responsibility 

for deciding what emission reductions 

will be required and from which source. 

The EPA’s responsibility is to ensure 

SIP revisions comply with the Act’s 

requirements. If a SIP revision meets the 

Act’s requirements, EPA must approve 

the revision. Commenters indicate that 

States have primary responsibility to 

craft SIPs, including the ‘‘emission 

limitations, control measures means or 

techniques . . . as may be necessary or 

appropriate to meet the applicable 

requirements’’ of the CAA. Commenters 

argue that EPA’s proposal not only 

inappropriately redefines section 

110(a)(2)(A) of the Act, but it also takes 

the discretion away from States to 

determine what constitutes enforceable, 

appropriate, or necessary emission 

limitations to be incorporated into a SIP. 

Response: The CAA grants States a 

central role in regulating air quality 

through the creation and 

implementation of SIPs, which outline 

state-specific strategies to meet the 

National Ambient Air Quality Standards 

(NAAQS) and other applicable CAA 

requirements. The States must ensure 

that SIPs include enforceable emission 

limitations, compliance schedules, and 

monitoring systems. EPA agrees that 

States have considerable flexibility in 

choosing how to meet Federal 

standards. However, the EPA must 

review the SIPs to ensure compliance 

with Federal law and other CAA 

requirements and approve SIP 

submittals that comply and disapprove 

those that do not. Congress established 

a framework of mandatory requirements 

within which States may exercise their 

considerable discretion to design SIPs to 

provide for attainment and maintenance 

of the NAAQS and to meet other CAA 

requirements.6 This view was affirmed 

in Environ. Comm. Fl. Elec. Power v. 

EPA, 94 F.4th at 93: 

[W]hile states generally have ‘‘the power to 

determine which sources w[ill] be burdened 

by regulation and to what extent,’’ Union 

Elec. Co. v. EPA, 427 U.S. 246, 269, 96 S. Ct. 

2518, 49 L. Ed. 2d 474 (1976), the Act 

‘‘ ‘subject[s] the states to strict minimum 

compliance requirements’ and gives EPA the 

authority to determine a state’s compliance 

with the requirements,’’ Michigan v. EPA, 

213 F.3d 663, 687, 341 U.S. App. DC 306 

(D.C. Cir. 2000) (quoting Union Elec. Co., 427 

U.S. at 256–57). 

While it is initially the State’s 

responsibility to determine which 

110(a)(2)(A) emission limitations and 

other control measures are necessary or 

appropriate to attain and maintain the 

NAAQS and meet other CAA 

requirements, the D.C. Circuit made it 

clear that the final determination of 

what is ‘‘necessary or appropriate’’ is 

EPA’s responsibility: 

To be sure, EPA could determine that the 

hypothetical state is wrong in concluding 

that its chosen mix of ‘‘other control 

measures’’ is ‘‘necessary or appropriate’’ to 

meet the NAAQS. If so, EPA might decide 

that, for the state to meet the NAAQS, at least 

one of the ‘‘other control measures’’ must be 

adjusted such that it satisfies the definition 

of an ‘‘emission limitation’’—including, for 

instance, by converting it from a 

discontinuous to a continuous measure.7

EPA agrees that States have the 

primary responsibility to determine 

what measures will be included in a SIP 

as necessary to meet the Act’s 

requirements and that EPA must 

approve a SIP revision if it meets the 

Act’s applicable requirements. In this 

instance, far from ignoring the State’s 

discretion, we read the 2020 SIP 

revision and took it at face value. The 

SIP revision stated: 

The proposed SIP revision would make 

certain operational limits and work practices 

for periods of planned MSS at the listed 

EGUs federally enforceable so that emission 

limitations apply on a continuous basis (at all 

times of operation) (see FCAA, 

§ 110(a)(2)(A)—SIP must contain emission 

limits, measures, etc. and § 302(k)—emission 

limits apply on a continuous basis to assure 

continuous emission reduction). 

This statement appears to indicate 

that Texas intended for the 2020 SIP 

revision to create emission limitations 

that apply on a continuous basis and are 

federally enforceable. Moreover, this is 

consistent with the understanding 

between Texas and EPA that is 

documented in the letter exchange 

between Guy Donaldson, Associate 

Director, Air Branch, Air and Radiation 

Division, EPA Region 6, dated March 

13, 2017, and Steve Hagle, Deputy 

Director, Office of Air, TCEQ, dated 

June 7, 2017 (Hagle letter). The Hagle 

letter stated the purpose of the AOs 

would be to include enforceable opacity 

and particulate emissions limitations for 

periods of planned startup and 

shutdown activities. 

As commenters have pointed out, 

TCEQ undertook this SIP revision to 

resolve a Title V problem after the EPA 

was petitioned under Title V to object 

to Texas using MSS permits issued 

under its NSR program to revise the SIP 

to provide exemptions from the rules in 

Chapter 111 during MSS. As is 

discussed in Section II.B, in its 2015 

interpretive letter, Texas put forward its 

explanation that the rules did not apply 

to coal fired boilers with ESPs during 

MSS. This interpretation left the SIP 

without clarity on the allowed time 

periods for MSS and when the Chapter 

111 rules would apply. Moreover, the 

understanding between TCEQ and EPA, 

as documented in the exchange of 

letters,8 makes clear EPA’s expectation 

that the SIP should provide for 

continuous emission limitations. 

In sum, the EPA has the authority to 

review the 2020 SIP revision as an 

emission limit subject to the 

requirements of 302(k) and we are only 

evaluating what is written in the SIP 

and our understanding from the 

discussions leading up to the 

development of the SIP revision. 

To the extent TCEQ no longer believes 

continuity is necessary or appropriate 

for the 30 TAC 111 provisions and the 

AOs, EPA disagrees, as is described in 

additional detail in Section II.D of this 

document. 

D. Comments on D.C. Circuit Decision 

and ‘‘Emission Limitations’’ 

Comment: Numerous commenters 

discuss the D.C. Circuit’s recent 

decision in Environmental Committee of 

Florida Electric Power Coordinating 


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9See State Implementation Plans: Response to 

Petition for Rulemaking; Restatement and Update of 

EPA’s SSM Policy Applicable to SIPs; Findings of 

Substantial Inadequacy; and SIP Calls To Amend 

Provisions Applying to Excess Emissions During 

Periods of Startup, Shutdown and Malfunction, 80 

FR 33840 (June 12, 2015). 

10 94 F.4th at 102. 11 Id. at 110. 12 Id. Some commenters state that certain SIP 

provisions that EPA SIP called in the 2015 SSM 

Action for which the SIP call was vacated are 

substantially similar to the AOs. Given that the D.C. 

Circuit did not find that those SIP provisions were 

appropriate or acceptable, their similarity to the 

AOs is irrelevant. 13Commenters frame the question as whether or 

not the AOs themselves need to meet the definition 

of ‘‘emission limitation.’’ The AOs are intended to 

cover only periods of MSS; as such, the question 

EPA needs to answer is whether it is necessary or 

appropriate for the AOs combined with the 

numerical limits in 30 TAC 111.111 and 30 TAC 

111.153 to be ‘‘emission limitations.’’ 14 2020 SIP revision at iv. 

15 94 F.4th at 107. 

16CAA section 169(3); 40 CFR 52.21(b)(12) 

(emphasis added). Texas’s definition of BACT 

incorporates EPA’s definition by reference. 30 

T.A.C. secs. 116.111(a)(2)(C), 116.160(c)(1)(A). 

17This has been EPA’s consistent interpretation 

of the CAA since at least 1993. See, e.g., In re 

Southwestern Electric Power Company, Order on 

Petition No. VI–2014–01 (February 3, 2016), at 8 

(stating that BACT limits apply at all times, 

including during periods of shutdown and 

malfunction events); In re Cash Creek Generation, 

LLC, Order on Petition No. IV–2010–4 (June 15, 

Continued 

Group v. EPA, 94 F.4th 77 (D.C. Cir. 

2024) and its implications for whether 

or not the emissions limits in the AOs 

should count as ‘‘emissions limitations’’ 

as defined in section 302(k) of the CAA. 

Commenters state that, per the court’s 

decision, not all emission limits in a SIP 

necessarily need to qualify as ‘‘emission 

limitations’’ under CAA 110(a)(2)(A), 

which requires that SIPs ‘‘include 

enforceable emission limitations and 

other control measures, means or 

techniques . . . as may be necessary or 

appropriate to meet the applicable 

requirements of this chapter’’ (emphasis 

added). Commenters argue that EPA has 

not determined whether it is necessary 

or appropriate for the AOs to qualify as 

emissions limitations, and that the 

Agency should not play ‘‘semantic 

gotcha games’’ to thus qualify them. 

Commenters claim that it is not 

necessary or appropriate for the AOs to 

qualify as emissions limitations, as they 

are work practices established as BACT. 

Commenters also claim that EPA’s 2015 

SSM policy 9 has been overruled and 

that the court found that exemption 

provisions in other State SIPs were 

acceptable. 

One commenter states that Texas 

admitted that the SIP provisions at issue 

were ‘‘emissions limitations’’ and thus 

need to be continuous. Commenter also 

argues that the SIP provisions are 

‘‘necessary or appropriate’’ to meet CAA 

requirements both because they were 

originally submitted in order to provide 

for attainment and maintenance of the 

NAAQS, and because commenter has 

modeled NAAQS violations. 

Response: It is important at the outset 

to be very clear about what is contained 

within the D.C. Circuit’s opinion in 

Florida Electric and what is not. EPA 

agrees with commenters that the D.C. 

Circuit held that section 110(a)(2)(A) of 

the CAA requires only that emission 

limitations (as defined in section 302(k)) 

be continuous and that a particular SIP 

provision is only required to be an 

‘‘emission limitation’’ if it is ‘‘necessary 

or appropriate to meet’’ applicable CAA 

requirements. In particular, the court 

held that EPA ‘‘would need to find that, 

to enable a State to meet the NAAQS or 

some other ‘applicable requirement,’ it 

is ‘necessary or appropriate’ that 

emissions restrictions subject to 

automatic exemptions satisfy the 

statutory definition of an ‘emission 

limitation.’ ’’ 10

Crucially, the court did not find that 

the emissions limits with automatic 

exemptions that EPA had SIP called 

were acceptable or appropriate. In fact, 

the court explicitly withheld judgment 

as to whether the ‘‘called SIPs’ relevant 

emission restrictions in fact amount to 

(or must amount to) ‘emission 

limitations’ per the statutory 

definition.’’ 11 The court stated that if 

EPA ‘‘were to determine that, for states 

to meet the CAA’s applicable 

requirements, it is ‘necessary or 

appropriate’ for their emission 

reduction measures to meet the 

statutory definition of ‘emission 

limitations’ and operate during SSM 

periods, the agency could explain and 

implement that rationale and its action 

would be subject to judicial review.’’ 12

That is precisely what EPA is doing in 

this final action: determining that it is 

necessary or appropriate for the 

emissions reduction measures 

submitted to the Agency by Texas, in 

conjunction with the existing measures, 

to meet the full definition of ‘‘emissions 

limitation’’ under 302(k), and thus they 

must be continuous.13

The EPA did not explicitly propose to 

make such a ‘‘necessary or appropriate’’ 

determination in the proposed 

disapproval action because the Agency 

determined that Texas agreed that the 

AOs were emissions limitations as 

defined under the CAA. The EPA’s 

conclusion was not based merely on the 

fact that Texas used the words 

‘‘emission limitation’’ in its submission, 

but rather the fact that the submission 

was explicitly intended to create 

continuous emissions limitations: 

The proposed SIP revision would make 

certain operational limits and work practices 

for periods of planned MSS at the listed 

EGUs federally enforceable so that emission 

limitations apply on a continuous basis (at all 

times of operation) (see FCAA, 

§ 110(a)(2)(A)—SIP must contain emission 

limits, measures, etc. and § 302(k)—emission 

limits apply on a continuous basis to assure 

continuous emission reduction).14

As the D.C. Circuit stated, ‘‘states are 

initially charged with determining 

whether an ‘emission limitation’ is 

‘necessary or appropriate’ to meet the 

CAA’s applicable requirements.’’ 15 It is 

true that Texas’s submission came 

before the D.C. Circuit’s opinion was 

released; however, EPA could only act 

on what had been submitted, and the 

only conclusion the Agency could draw 

was that Texas had initially determined 

that the AOs, in combination with the 

numerical limits in 30 TAC Chapter 

111, were in fact emissions limitations 

that should apply on a continuous basis. 

EPA agreed that continuity was 

required, as is discussed at length in the 

proposal, and thus had no need to make 

an additional determination. 

Regardless of Texas’s intentions, EPA 

agrees that the substance of the 

provisions at issue are more important 

than their label. As such, EPA has 

reviewed these provisions in detail and 

determined that it is ‘‘necessary or 

appropriate’’ for the emissions 

restrictions, including the submitted 

AOs, to meet the definition of ‘‘emission 

limitations’’ in CAA section 302(k). 

First, as is highlighted by the 

commenters, Texas has approved the 

emissions reduction measures included 

in the AOs in permits as ‘‘best available 

control technology’’ (BACT) for the 

sources at issue during MSS periods. 

Texas claims that the measures are 

continuous in part because they 

constitute BACT. BACT is explicitly 

defined in the CAA and EPA’s 

regulations as ‘‘an emission limitation 

based on the maximum degree of 

reduction of each pollutant subject to 

regulation. . . .’’ 16 In other words, 

Congress indicated that the combination 

of measures approved as BACT must be 

emission limitations. In contrast with 

section 110(a)(2)(A), there is no 

indication that measures approved as 

BACT can be anything other than 

emission limitations—if it constitutes 

BACT, it must be an emission 

limitation, and thus must meet the CAA 

definition of emission limitation in 

section 302(k). If the AOs are BACT, 

they must be emission limitations, and 

thus must be continuous.17


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2012), at 21 (same). TCEQ consistently claims in its 

comments that the precise combination of measures 

in the AOs are what constitutes BACT. However, it 

is not clear whether what has been approved as 

BACT also includes the lb/hr emission limits for 

PM that apply during MSS in the relevant permits. 

Those lb/hr limits were not included in the AOs 

submitted for approval into the SIP. 18 57 FR 13502 (Apr. 16, 1992). 

Second, these AOs as written would 

allow for emissions that could threaten 

the State’s ability to comply with the 

requirements of the CAA, and the 

NAAQS in particular. In general, SSM 

exemptions can threaten public health 

and welfare, particularly given that they 

can allow for dramatically higher 

amounts of emissions than the amount 

of pollutants emitted at other times. For 

the first time, Texas is attempting to 

clarify and make federally enforceable 

requirements that apply to the relevant 

sources specifically during MSS 

periods. However, rather than limits 

that appear on their face to apply at all 

times, the sources governed by the AOs 

would have periods where no 

enforceable standards apply at all. EPA 

highlighted the problematic features of 

the AO measures in the proposal. Two 

particular features could allow for 

essentially unlimited periods of high 

PM emissions: first, for startup and 

shutdown periods, there are no limits to 

the frequency of startup or shutdown 

events, and the requirements for when 

an ESP must be engaged are overly 

vague. Second, for maintenance periods, 

there are essentially no restrictions 

during certain time periods. As 

currently written, neither Texas nor 

commenters have shown that the 

requirements in the AOs are protective 

of the NAAQS. 

In fact, there is quantitative evidence 

in the record that demonstrates 

approving these AOs could result in 

NAAQS violations. During the public 

comment period, Sierra Club presented 

modeling showing that the emissions 

restrictions, or lack thereof, included in 

the AOs have the potential to cause 

NAAQS violations in the areas around 

the relevant sources. As is discussed in 

the modeling section, Section II.I, the 

modeling may actually be 

underestimating the ambient air quality 

in those areas given the overly 

conservative assumptions around 

background concentrations. As is also 

discussed in response in Section II.H, 

the modeling presents a more accurate 

view of the ambient air quality near the 

relevant sources than Texas has 

provided in its submission and 

comments, given the fact that the 

monitors cited to by Texas are not sited 

to characterize the air quality near 

theses sources, with the closest monitor 

being 17 kilometers (km) from the 

sources referenced in the modeling. 

It is true that some sources are 

currently choosing to be more protective 

than the SIP limits combined with the 

AOs would require. For example, NRG 

has chosen to burn sub-bituminous coal 

rather than lignite, which results in 

lower modeled PM concentrations. 

However, those choices are not 

specifically required under the AOs or 

the SIP. When assessing SIP 

submissions, Congress has directed EPA 

to review the ‘‘enforceable emission 

limitations and other control measures’’ 

that are required under CAA section 

110(a)(2)(A)—measures that are not in 

the SIP cannot displace those 

requirements. The modeling by Sierra 

Club presents a compelling case that, if 

the AOs are adopted and sources decide 

not to continue to overcomply (for 

whatever reason—an exogenous shock 

to the system, a change in strategy, court 

decisions affecting other Federal rules, 

etc.), the AOs as they are currently 

written are not protective of the NAAQS 

because, in conjunction with the PM 

and opacity limits in 30 TAC 111, they 

do not apply on a continuous basis. As 

such, EPA is determining that, in order 

to ensure NAAQS protection, it is 

necessary or appropriate for the AOs to 

apply continuously when incorporated 

with the 30 TAC 111 p.m. and opacity 

limits into the SIP, and thus the AOs, in 

conjunction with the limits that apply 

during non-MSS periods, must meet the 

definition of emission limitation. 

EPA agrees with the logic expressed 

in the comment from Sierra Club and, 

as such, is disapproving the SIP 

submission. EPA agrees in particular 

that modeling is not always necessary in 

order for the Agency to make a 

‘‘necessary or appropriate’’ 

determination, depending on the 

context of the SIP submission. EPA has 

multiple grounds to find that it is 

‘‘necessary or appropriate’’ for the SIP 

provisions at issue here to be emissions 

limitations, and thus continuous. 

E. Comments on Alternative Emissions 

Limitations (AEL) Criteria 

Comment: Commenters argue that 

EPA’s reliance on seven recommended 

criteria for assessing the AOs is 

inappropriate and lacks statutory basis, 

asserting that any standards for 

evaluating Texas’s plans must derive 

from the text of the CAA itself. One 

commenter also argues that ‘‘nonapplicability’’ is not the same as an 

‘‘exemption’’ provision and thus the 

AEL criteria should not even apply. 

Response: In the context of making 

recommendations to States for how to 

address emissions during startup and 

shutdown, the EPA has long 

recommended seven criteria for States 

to evaluate in establishing appropriate 

alternative emission limitations.18

Among the purposes for these 

recommendations was the need to take 

into account technological limitations 

that might prevent compliance with the 

otherwise applicable emission 

limitations, while ensuring that those 

alternative limitations complied with 

the continuity and enforceability 

requirements of the CAA. As a general 

matter, they provide a framework 

intended to assist States in developing 

emissions limitations that meet the 

requirements of the CAA. That 

framework also helps EPA assess 

whether the CAA’s requirements are 

met. These recommendations serve to 

assist in the development of enforceable 

and continuous requirements that 

would apply during periods when the 

limits in Chapter 111 for normal 

operation cannot be met due to the 

technological limitations of the ESPs. 

The recommended seven criteria were 

re-articulated in the 2015 SSM SIP 

Action, and read as follows: (1) The 

revision is limited to specific, narrowly 

defined source categories using specific 

control strategies; (2) Use of the control 

strategy for this source category is 

technically infeasible during startup or 

shutdown periods; (3) The AEL requires 

that the frequency and duration of 

operation in startup or shutdown mode 

are minimized to the greatest extent 

practicable; (4) As part of its 

justification of the SIP revision, the 

State analyzes the potential worst-case 

emissions that could occur during 

startup and shutdown based on the 

applicable AEL; (5) The AEL requires 

that all possible steps are taken to 

minimize the impact of emissions 

during startup and shutdown on 

ambient air quality; (6) The AEL 

requires that, at all times, the facility is 

operated in a manner consistent with 

good practice for minimizing emissions 

and the source uses best efforts 

regarding planning, design, and 

operating procedures; and (7) The AEL 

requires that the owner or operator’s 

actions during startup and shutdown 

periods are documented by properly 

signed, contemporaneous operating logs 

or other relevant evidence. 

Any SIP revision establishing an AEL 

that applies during startup and 

shutdown would be subject to the same 

procedural and substantive review 

requirements as any other SIP 

submission. While the EPA compared 

the AOs to these recommendations 

(specifically we discuss criteria 5 and 


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19See additional discussion on these 

recommendations in response to comments in 

Section II.F.3. It should also be noted that Texas did 

not give consideration to criteria 4, e.g. the State 

analyzes the potential worst-case emissions that 

could occur during startup and shutdown based on 

the applicable AEL. See Section II.H and.I 

discussing Sierra Club’s modeling evaluation of the 

potential impact of worst case emissions. 

20At various points in TCEQ’s comment letter, it 

makes what EPA interprets as drafting errors about 

its interpretation of the scope of the 30 TAC 

Chapter 111 limits. First, it states ‘‘as TCEQ 

explained in the proposed and adopted SIP 

narrative and the incorporated December 2, 2015, 

interpretive letter, the PM and opacity limits in 

§§ 111.111(a)(1) and 111.153(b) do not apply to 

plants equipped with electrostatic precipitators 

(ESPs) for particulate control.’’ Neither the 

proposed SIP nor the interpretive letter make such 

an extremely broad claim—that the 30 TAC Chapter 

111 limits don’t apply at all to plants equipped 

with ESPs. EPA’s interpretation is that TCEQ 

intended to state, as they did in those other 

documents, that the limits do not apply during MSS 

periods. 

Second, TCEQ states that ‘‘its SIP rules on opacity 

and PM do not apply during periods of SSM for 

these specific units.’’ Presumably TCEQ intended to 

state that those limits do not apply during periods 

of MSS, which covers maintenance periods rather 

than the malfunction periods covered by the 

acronym ‘‘SSM.’’ Otherwise, EPA would be 

required to disapprove the submission as it would 

be an admission by Texas that 30 TAC chapter 111 

limits do apply during maintenance periods and its 

new submission would be newly putting in place 

exemptions to those limits during those periods. 

21See 80 FR 33840, 33899–900, and 33903–904 

(June 12, 2015) for an extended discussion of why 

periods when only a ‘‘general duty’’ provision 

applies cannot constitute part of an enforceable, 

continuous emission limitation. 

22To be clear, emissions limitations need not be 

numerical at all times to be continuous, but it is 

easy to guarantee continuousness when a numerical 

limit applies at all times. 

criteria 6 in the proposed action), the 

failure to follow these criteria is not the 

basis of the EPA’s disapproval.19 The 

EPA reviewed whether the AOs could in 

practice be enforced as required by the 

CAA. The EPA found, as discussed in 

the proposal and in response to 

comments in Section II.F, that the 

emission limits were too subjective to 

provide for enforceability and are not 

continuous. 

The EPA’s disapproval of the Texas 

SIP submission stems from a statutorily 

derived authority conferred upon the 

agency through Congress and our 

disapproval is based on those 

authorities. 

TCEQ also commented that the 30 

TAC 111 rules do not apply to plants 

equipped with ESPs during MSS 

periods 20 and that ‘‘non-applicability is 

not the same as exemption’’ and thus 

the AEL framework is inapplicable. As 

we have noted, the AEL framework is 

simply a series of recommendations, 

and so EPA’s review of Texas’s 

submission under that framework is 

meant to provide a helpful lens through 

which to assess the submission for 

approvability. Nonetheless, ‘‘nonapplicability’’ and ‘‘exemption’’ are 

precisely the same thing in this context: 

limits that apply during normal 

operation and allegedly do not apply 

during periods of MSS. Any other 

conclusion would be nothing more than 

a ‘‘semantic ‘gotcha’ game.’’ Florida 

Electric, 94 F.4th at 109. 

F. Comments on Enforceability, 

Continuity, and Adequacy of the AO 

requirements 

1. Continuity 

Comment: Commenters argue that, 

even if the combination of 30 TAC 111 

limits and the work practice and 

operational standards contained within 

the AOs must meet the definition of 

‘‘emission limitation’’ and thus be 

continuous, the requirements do apply 

on a continuous basis and thus should 

be approved. In particular, TCEQ states 

that the durational limits do not allow 

for uncontrolled operation and are an 

integral part of the permit requirements 

for MSS that TCEQ determined to be 

BACT. Commenter asserts that time 

limits are controls because they are set 

at a level that will allow the plants to 

conduct startups and shutdowns up to 

an annual and daily amount of PM 

emissions associated with these 

activities. The permits include 

Maximum Allowable Emissions Table 

(MAERT) limits set at levels that are 

determined to be protective and not 

interfere with maintenance of the PM 

NAAQS. 

Response: EPA disagrees with 

commenter that the AOs operate 

alongside the PM and opacity standards 

in 30 TAC 111 to create a continuous 

emission limitation. It is true that 

emissions limitations do ‘‘not require 

that a singular rate or concentration 

apply on a continuous basis. Rather, the 

limitation can include ‘‘design, 

equipment, work practice, or 

operational standard[s].’’ However, the 

EPA finds that for the AO restrictions 

that apply during startup and shutdown 

periods, the requirements are overly 

vague and there are no limits to the 

frequency of startup or shutdown 

events, allowing for essentially 

unlimited periods of uncontrolled PM 

emissions. We discuss this in more 

depth in response to other comments. In 

addition, we find that the requirements 

during planned maintenance do not 

provide for continuous emission limits 

because there are no restrictions to 

emissions or work practices that apply 

other than a limit to the total annual 

time of maintenance activities. For these 

activities, the AOs ‘‘authorize’’ periods 

of opacity greater than 20% for a 

number of hours per year (e.g., 535 hrs/ 

year for each unit at Martin Lake). The 

only ostensible requirement during 

maintenance periods appears to be that 

the source operate the boiler and its ESP 

in accordance with good air pollution 

control practices, safe operating 

practices, and protection of the facility 

and associated air pollution control 

equipment. The generic general duty 

that an owner or operator shall operate 

a source consistent with safety and good 

air pollution control practices for 

minimizing emissions is not sufficient 

to identify what these specific practices 

might be across the range of 

maintenance activities to which the AOs 

apply. Therefore, such general duty 

clauses are not practically enforceable 

as a limitation on emissions during 

these activities.21

It is important to note that the 

relevant permits from which the AOs 

originate also include lb/hr PM limits 

during MSS periods that operate in the 

background of the combination of work 

practices that are contained in the AOs 

that were submitted to EPA. It is not 

clear from TCEQ’s submission or 

comments whether what has been 

approved by TCEQ as BACT also 

includes the lb/hr emission limits for 

PM that apply during MSS in the 

relevant permits. It is also unclear why 

TCEQ did not include those limits in 

the AOs. As such, we are not 

specifically evaluating those numerical 

limits as they are not included in the 

SIP submittal. EPA’s analysis of whether 

or not the limits in 30 TAC 111 

combined with the submission operate 

as a continuous emissions limitation 

might be different if there were 

additional lb/hr background limits that 

also applied.22 In response to comments 

in Section II.I of this document and in 

the RTC, we discuss modeling 

submitted by Sierra Club that evaluates 

the potential for emissions during MSS 

to result in violations of the NAAQS 

and compares the modeled emission 

rates to the permit limits. Texas did not 

provide modeling with this SIP revision. 

As we discuss elsewhere, there are no 

limits on frequency of MSS events in 

the AOs and therefore, the durational 

limits for individual startup and 

shutdown events are not protective of 

the ton/year requirements in the 

permits. Furthermore, the permit limits 

are not permanent because they are not 

incorporated into the SIP and can 

therefore be revised by the State without 

a SIP approval. 


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23See Section II.C and D 

24See Guidance an Enforceability Requirements 

for Limiting Potential to Emit through SIP and § 112 

Rules and General Permits, US EPA, January 25, 

1995. 

25See ‘‘Review of State Implementation Plans and 

Revisions for Enforceability and Legal Sufficiency,’’ 

from Michael Alushin, Alan Eckert, and John Seitz, 

September 3, 1987 (1997 SIP memo). 

26 Id. 

27See source specific AOs included in the docket 

for this action. 

28See 2020 SIP revision at Section 2.2.2: ‘‘Special 

conditions in the EGUs’ NSR permits were designed 

to provide a federally enforceable limit for 

emissions during planned MSS activities when the 

ESPs are operated outside the optimal range. The 

conditions define the startup and shutdown periods 

and establish durational limits for these activities 

in order to minimize emissions. The time limits in 

the special conditions reflect best management 

practices and promote the safe, effective operation 

of the respective boiler and ESP. Minimizing 

emissions using good air pollution control 

procedures and best management practices are 

considered BACT for the planned MSS activities. 

These conditions are specifically incorporated into 

the AOs for the respective EGUs.’’ We note that it 

2. Enforceability and Adequacy of AO 

Requirements 

Comment: A commenter (NRG) states 

that EPA fails to identify benchmarks 

against which to judge the adequacy of 

Limestone’s work practices for 

frequency or duration, or control-level 

for MSS emissions. Commenter also 

states that EPA fails to identify any CAA 

or other regulatory authority that 

suggests frequency, duration, or controllevel standards for SIP provisions on 

MSS emissions, nor does EPA identify 

a requirement in the Act or another 

regulation for which a longer duration, 

higher frequency, or lesser degree of 

control would raise a compliance 

concern. 

Commenter states that the AO 

provides clear and enforceable 

constraints and there is no deficiency as 

to the allowable frequency and duration 

or level of control. Commenter (TCEQ) 

disagrees with EPA that no discussion 

on the historical frequency of startup 

events is included in the SIP narrative 

and that periods of startup and 

shutdown have been and continue to be 

infrequent and intermittent. Commenter 

(NRG) claims that in the 50-year history 

of the MSS requirements and their 

predecessor provisions, no party has 

raised concerns with the frequency or 

duration of Limestone’s MSS emissions, 

the level of control of emissions, or the 

practical enforceability of constraints 

imposed on the facility, nor has any 

issue arisen as to any air quality issues 

associated with those emissions. 

Several commenters mention EPA’s 

use of the term ‘‘practical 

enforceability.’’ Some of these 

commenters argue that the 2020 SIP 

revision is practically enforceable, while 

others argue that ‘‘practical 

enforceability’’ is not a requirement in 

the Act. 

Commenters assert that the EPA 

disapproved the AOs because they do 

not impose standardized or identical 

requirements on all sources. 

One commenter (Sierra Club) states 

that the EPA correctly asserts that the 

CAA requires SIPs to include 

enforceable emission limits. The citizen 

suit provision in 42 U.S.C. 7604 further 

supports this by allowing citizens to 

take legal action over violations of SIP 

limits. The provisions in the AOs that 

allow for exemptions during MSS 

periods (referred to as ‘‘MSS 

provisions’’) violate this enforcement 

requirement by effectively eliminating 

public access to enforce SIP limits 

during these periods. The MSS 

provisions are also not practically 

enforceable, as they fail to provide clear 

standards for when equipment, like 

ESPs, is considered ‘‘in service’’ or 

functioning properly to control 

emissions. 

Response: The EPA disagrees with the 

commenters arguing that the AOs are 

adequate and enforceable. As an initial 

matter, the adequacy of all SIP 

submissions are judged against CAA 

requirements, including that they are 

enforceable and, if they are emission 

limitations or it is necessary or 

appropriate for them to be emission 

limitations, that they are continuous. 

Enforceable meaning that the SIP is 

subject to a legal means for ensuring 

that sources are in compliance with the 

control measure set out in the proposal. 

In the proposed action, we discuss at 

length the reasons why we find the 

requirements submitted by the State for 

incorporation into the SIP to not be 

enforceable. Second, an additional 

requirement for emission limitations in 

the SIP are that they are continuous. We 

address the determination that is 

necessary or appropriate for the AOs 

combined with the numerical limits in 

30 TAC 111.111 and 111.153 to be 

‘‘emission limitations’’ and therefore 

must be continuous in response to 

separate comments in this document.23

EPA has long used the term ‘‘practical 

enforceability’’ to refer to requirements 

for source specific permits to be 

federally enforceable.24 Use of the term 

‘‘practical’’ is not adding new 

enforceability requirements but seeks to 

provide clarity on the manner in which 

the source specific requirements are not 

federally enforceable. 

In 1987, EPA laid out enforceability 

criteria that SIP rules must meet.25 In 

general, practical enforceability for a 

source-specific permit term means that 

the provision must specify: (1) a 

technically accurate limitation and the 

portions of the source subject to the 

limitation; (2) the time period for the 

limitation (hourly, daily, monthly, 

annually); and (3) the method to 

determine compliance including 

appropriate monitoring, record keeping 

and reporting. For rules and general 

permits that apply to categories of 

sources, practical enforceability 

additionally requires that the provision 

(4) identify the categories of sources that 

are covered by the rule; (5) where 

coverage is optional, provide for notice 

to the permitting authority of the 

source’s election to be covered by the 

rule; and (6) recognize the enforcement 

consequences relevant to the rule.26

In the instant action, EPA proposed to 

find that the conditions contained 

within the source specific AOs do not 

meet the requirements for 

enforceability. The conditions that 

Texas submitted as part of their SIP 

revision are too subjective to provide 

EPA with clear methods and conditions 

to be able to practically enforce the 

limitations should the need arise. For 

example, the AOs submitted as part of 

the 2020 SIP revision include a 

requirement that ‘‘all the sources must 

comply with the boiler and ESP 

manufacturer’s operating procedures, or 

the owner/operator’s written Standard 

Operating Procedures (SOP) manual and 

to operate in a manner consistent with 

the procedures to minimum opacity.’’ 27

However, it is unclear from the 2020 SIP 

revision what procedures should be 

followed if the SOP is inconsistent with 

the manufacturer’s operating 

procedures. Further, as the SOP can be 

modified over time, the required work 

practices cannot be considered 

permanent and enforceable. For a 

measure to be relied on as an emission 

limitation, it must be permanent which 

means it cannot be revised absent 

following the SIP revision process. 

We disagree with the commenter that 

there are ‘‘clear and enforceable 

constraints’’ to the frequency or 

duration of events, as there is no limit 

to the frequency of normal startup or 

shutdown events. Furthermore, the 

definitions for when startup ends or 

shutdown begins lack clear and 

measurable requirements by which 

compliance can be determined. Just as 

limits on the duration of the MSS events 

were identified by TCEQ as BACT and 

necessary to minimize emissions and 

reflect best management practices and 

promote the safe, effective operation of 

the respective boiler and ESP, limits on 

frequency of MSS events are necessary 

to effectively limit the emissions.28


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is not clear whether what has been approved as 

BACT also includes the lb/hr emission limits for 

PM that apply during MSS in the relevant permits. 

Those lb/hr limits were not included in the AOs 

submitted for approval into the SIP. 

29 40 CFR part 50.20 and 40 CFR part 50 

Appendix N. 40 CFR part 50.20(b) ‘‘The primary 

annual PM2.5 standard is met when the annual 

arithmetic mean concentration, as determined in 

accordance with appendix N to this part, is less 

than or equal to 9.0 mg/m3.: 40 CFR part 50.20(c) 

‘‘The primary 24-hour PM2.5 standard is met when 

the 98th percentile 24-hour concentration, as 

determined in accordance with appendix N to this 

part, is less than or equal to 35 mg/m3.’’ 40 CFR part 

50 Appendix N clarifies the specific procedures for 

calculating the PM 2.5 design values. See Appendix 

N for details, but in general the PM 2.5 annual 

NAAQS design value is the average of three 

consecutive years annual arithmetic mean 

concentrations, and the PM 2.5 24-hour NAAQS 

design value is the average of three consecutive 

years of the annual 98th percentile of 24-hour 

values. 30See 2020 SIP submission at Section 2.2.1. 

31See 80 FR 33840, 33899–900, and 33903–904 

(June 12, 2015) for an extended discussion of why 

periods when only a ‘‘general duty’’ provision 

applies cannot constitute part of an enforceable, 

continuous emission limitation. 

Commenters state that they have strong 

financial incentives to minimize the 

frequency and duration of MSS periods, 

however an incentive is not the same as 

an enforceable requirement. 

Furthermore, while we understand that 

there is a strong economic incentive to 

avoid downtime or periods of MSS in 

order to provide for efficient generation 

of electricity and sale of product, there 

does not seem to be an economic 

incentive to bring the ESP up to full 

operation during MSS due to the 

operating costs required to run the ESP. 

This is why it is important to define in 

a clear and enforceable requirement for 

when operation of the ESP should be 

initiated, and more importantly, when 

compliance with the limits in TAC Ch. 

111 is required. As discussed elsewhere 

in this document, comments from Sierra 

Club (including modeling) confirm our 

concern with this level of emissions, 

showing that the emissions restrictions 

provided in the AOs could potentially 

threaten attainment and maintenance 

and cause NAAQS violations in the 

areas around the relevant sources. As 

we noted in the proposed action, this is 

of particular concern as utilization of 

coal-fired power generation has become 

more variable and planned startup and 

shutdown events may occur more 

frequently than they have in the past. 

Even intermittent or infrequent events 

can potentially impact the NAAQS, in 

particular the 24-hr PM NAAQS that is 

based on the very high end (98th 

percentile) of 24-hour average 

concentrations in a year, which would 

be equivalent to the 8th highest day in 

the year when evaluating modeling.29 In 

the 2020 SIP revision, TCEQ provides 

that data from Electric Reliability 

Council of Texas (ERCOT) for calendar 

year 2018 shows for the five sources in 

ERCOT there were 46 days during 

which a unit was in startup mode.30

Providing data from one year is not 

sufficient to identify any variability in 

frequency of MSS events from year to 

year or any recent trends of increased 

frequency that would indicate whether 

past performance is indicative of future 

expected practice. Regardless, there are 

no enforceable limitations on frequency 

in the AOs or SIP. 

We also disagree with the commenter 

(NRG) that the AOs provide ‘‘clear and 

enforceable constraints’’ with respect to 

the level of control required. The 

commenter does not specifically address 

any of the deficiencies in the 

requirements identified by EPA in the 

proposed action that make the 

requirements vague and unenforceable. 

For example, for NRG Limestone, the 

AO requires the ESP be placed into 

service as soon as practical after the air 

heater outlet temperature is between 

200 and 300 degrees Fahrenheit. It is 

unclear why a range is specified rather 

than a minimum temperature or if there 

are other measurable parameters, such 

as flow rate or drum metal temperature, 

that are being evaluated to determine 

when it would be ‘‘practical’’ to place 

the ESP into service. Once the air heater 

outlet temperature is within the 

specified range, there are no specific 

conditions identified to define when it 

is required to place the ESP in service 

beyond ‘‘as soon as practical,’’ and no 

way to independently verify if the ESP 

was in fact placed into service as soon 

as practical. The commenter simply 

restates the requirements in the AO and 

states that they are clear and 

enforceable. Similarly, for NRG 

Limestone, the AO states that one 

condition required to identify when a 

startup ends is when the ESP is ‘‘fully 

optimized’’ but there are no specific 

conditions identified to define when the 

ESP is to be considered fully optimized. 

As identified by commenters (Sierra 

Club), the requirements do not define 

what it means to place an ESP ‘‘into 

service’’ and do not specify how the ESP 

must be operated during the startup 

period. This allows the ESPs to be 

operated at widely varying performance 

levels during startup, with some or all 

ESPs operating at much lower 

efficiencies (e.g., by turning on one or 

two fields during startup) than the 

equipment is capable of achieving. 

We disagree with the commenter that 

there is no deficiency with respect to 

the required operating procedures 

during MSS events. It is unclear what 

procedures should be followed for 

startup and shutdown if requirements in 

the SOP are inconsistent with the 

manufacturer’s operating procedures. In 

addition, the owner/operator’s SOP can 

be modified over time, and therefore the 

required work practices cannot be 

considered permanent and enforceable. 

As discussed in the proposed notice, we 

also find that the general duty 

provisions that apply during 

maintenance activities in the AOs are 

not practically enforceable. The generic 

general duty that an owner or operator 

shall operate a source consistent with 

safety and good air pollution control 

practices for minimizing emissions is 

not sufficient to identify what these 

specific practices might be across the 

range of maintenance activities to which 

the AOs apply, and thus such general 

duty clauses are not practically 

enforceable as a limitation on emissions 

during these activities.31 The AOs do 

not include any work practices that the 

sources are required to apply during 

these maintenance periods. For these 

activities, the AO for NRG Limestone 

‘‘authorize’’ periods of opacity greater 

than 15% for 535 hrs/year for each unit. 

As we discuss elsewhere, because 

emission limitations must be 

continuous, they cannot include gaps or 

periods during which sources are not 

required to limit their emissions and 

thus, for example, cannot include 

exemptions for emissions during 

periods of operation such as MSS. We 

find that these requirements are neither 

enforceable nor continuous. 

Commenters raise issue with a lack of 

identified concerns with enforceability/ 

adequacy of these provisions or air 

quality over the history of Limestone’s 

MSS practices. However, for the first 

time, Texas is attempting to clarify and 

make federally enforceable SIP 

requirements through the submitted 

AOs that apply to the relevant sources 

specifically during MSS periods. These 

submitted AOs must be evaluated for 

compliance with the CAA requirements, 

including that they are enforceable and 

protective of the NAAQS. During these 

events, the only requirements that apply 

are the work standards concerning 

placing the ESP in service as soon as 

practicable during startup or keeping 

the ESP in service as late as practicable 

during shutdown. There is no 

requirement for the sources to limit 

emissions during such events in any 

other way. PM emissions during these 

events can be much higher than normal 

emissions and there is no limitation on 

the number of times during the year a 


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32Commenters raised the issue of replicability not 

being a valid basis for disapproval, citing Texas v. 

E.P.A., 690 F.3d 670, at 683 (5th Cir. 2012) which 

holds that replicability is not an independent 

authoritative standard and standards that the EPA 

uses must derive from the CAA itself. This case is 

not analogous to this disapproval as replicability is 

not used as a basis of disapproval. 

33See Sections II.G, H and I for additional 

discussions on interference with attainment or 

maintenance of the NAAQS and modeling of 

potential impacts from MSS emissions. 

boiler can go through a planned startup 

or shutdown. As discussed elsewhere in 

this document, the lack of limits to the 

frequency of startup events, and overly 

vague requirements for when an ESP 

must be engaged, work together to mean 

that there could be essentially unlimited 

periods of high PM emissions where no 

enforceable standards apply to limit 

emissions. Neither Texas in the 2020 

SIP revision nor commenters have 

shown that the requirements in the AOs 

are protective of the NAAQS. As 

discussed elsewhere in this document, 

comments from Sierra Club (including 

modeling) confirm our concern with 

this level of emissions, showing that the 

emissions restrictions provided in the 

AOs have the potential to cause NAAQS 

violations in the areas around the 

relevant sources. The historical record 

of air monitoring data is not sufficient 

to identify air quality concerns as the 

monitors are not located in the vicinity 

of the sources and therefore cannot be 

used to characterize air quality or 

impacts from these emissions near the 

sources. 

The EPA disagrees with commenters’ 

assertion that the EPA disapproved the 

AOs because they do not impose 

standardized or identical requirements 

on all sources.32 EPA’s disapproval is 

not based on a lack of identicality. In 

describing the issues with the AOs, EPA 

noted that the AOs vary in level of 

specificity and then provided an 

analysis of each AO, identifying the 

different approaches and lack of 

specificity in each approach that makes 

for an unenforceable requirement. At no 

point did EPA identify a concern with 

the lack of uniformity in the AOs. As 

explained in the proposed action, we 

are disapproving the 2020 SIP revision 

because the AOs lack specificity and are 

ambiguous and unenforceable because 

they are unclear as to the procedures an 

operator must follow to be in 

compliance and at what point in the 

startup or shutdown process the facility 

must switch from compliance with the 

AO to compliance with 30 TAC 

111.111(a)(1) and 30 TAC 111.153(b) as 

required for routine operation. 

One commenter agreed with EPA’s 

view that the AOs are unenforceable, 

stating that in addition to EPA’s own 

enforcement powers, the CAA 

guarantees citizens’ ability to directly 

enforce SIP limits. EPA agrees that the 

citizen suit provisions of the CAA 

further highlight the need for SIP limits 

like the AOs to be enforceable. 

In summary, we find that the AO 

restrictions are overly vague and 

unenforceable. We also find that the AO 

requirements, in combination with the 

requirements in 30 TAC 111, do not 

provide for continuous emission 

limitations. Finally, we find that the AO 

requirements have not been shown to be 

protective of the NAAQS.33

3. EPA’s Recommended Measures 

Comment: Commenter (NRG) states 

the EPA suggests several additional 

‘‘preferred features’’ such as use of 

natural gas, different control devices, or 

reliance on MATS controls for the 

Agreed Orders. Commenter states that 

these ‘‘preferred features’’ are not 

required to comply with the Act and 

would be redundant, ineffective or 

inappropriate. 

Response: The ‘‘preferred features’’ 

identified by the commenter were 

provided by EPA as examples of 

measures that, if taken, would be 

expected to minimize emissions during 

MSS, not as specifically required 

features of the AOs. They are provided 

in the context of the recommendations 

for AELs that serve as guidance and not 

requirements for developing emissions 

limits that apply at times like MSS 

when technological limitations require 

different limitations on emissions. As 

discussed elsewhere, the AOs as 

submitted do not provide for 

enforceable requirements during MSS. 

EPA provided a discussion of measures 

that could be considered to potentially 

address these enforceability 

deficiencies. For example, if the AOs 

included a requirement to startup using 

natural gas and only introduce coal once 

the ESP is fully energized, that would be 

a clear and enforceable requirement that 

would also minimize emissions during 

startup. Similarly, use of a baghouse 

would also alleviate concerns from 

emissions during MSS. We in no way 

are suggesting that these are the only 

options for addressing emissions during 

MSS but provided them as examples of 

options that could be considered in 

developing approvable emission limits 

that apply during MSS. To the extent 

that some of these specific measures are 

already available and taken at the 

facility to comply with MATS or other 

requirements, they would also address 

emissions during MSS, and these can 

and should be incorporated into the SIP 

to provide for permanent and 

enforceable requirements during these 

periods. EPA’s proposed disapproval 

was based on the determination that the 

AO requirements are unenforceable and 

not that they failed to include these 

‘‘preferred features.’’ 

We disagree that adoption of these 

measures into the SIP would be 

redundant as the MATS requirements 

were promulgated to address hazardous 

air pollutants, such as mercury, and are 

subject to revision and/or court 

decisions independent of the 

requirements in the Texas SIP. To rely 

on these requirements to address 

opacity and PM emissions from EGUs 

with ESPs during MSS in Texas, Texas 

should adopt the requirements into the 

SIP. 

4. Recordkeeping and Reporting 

Comment: Commenters restate the 

recordkeeping language in the AOs and 

state that these requirements are not 

deficient. TCEQ states that the AOs are 

all enforceable because each plant 

operator must maintain records 

demonstrating when the startup or 

shutdown periods occur, based on flue 

gas temperature at the ESP, and must 

comply with permitted allowable 

emissions for PM emissions during 

planned SSM activities. In addition, 

TCEQ comments that EPA’s claims are 

speculative and not based on evidence 

of noncompliance with the identical 

terms contained in the plants’ NSR 

permits that have been in place for over 

10 years. NRG comments that EPA 

identifies no basis in the Act for a 

standard against which to evaluate 

monitoring, recordkeeping, and 

reporting in an MSS provision. 

Commenters also claim that deviation 

reports required under the Title V 

operating permits provide information 

to determine compliance. 

Response: We disagree with the 

commenters. Typically, a primary 

mechanism for ensuring that a SIP 

provision is legally and practicably 

enforceable is for a State to impose 

sufficient monitoring, recordkeeping, 

and reporting (MRR) requirements on 

affected sources. CAA section 

110(a)(2)(F)(i) speaks more explicitly to 

the requirement for SIPs to provide for 

emissions monitoring by requiring ‘‘the 

installation, maintenance, and 

replacement of equipment, and the 

implementation of other necessary 

steps, by owner or operators of 

stationary sources to monitor emissions 

from such sources,’’ as may be 

prescribed by EPA. EPA has 

promulgated regulations implementing 

this requirement at 40 CFR 51.214, 

which requires State SIPs to contain 


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legally enforceable procedures to 

‘‘[r]equire stationary sources subject to 

emission standards as part of an 

applicable plan to install, calibrate, 

maintain, and operate equipment for 

continuously monitoring and recording 

emissions,’’ among other requirements. 

EPA notes that monitoring and 

recordkeeping requirements serve 

multiple purposes, including supporting 

effective enforcement of SIP 

requirements. A lack of adequate 

monitoring and recordkeeping 

requirements can undermine the ability 

of the State, the EPA, and citizens to 

evaluate or enforce a source’s 

compliance with applicable emissions 

limitations imposed by the SIP. 

The AOs require sources to keep 

records of periods of planned MSS, the 

opacity measured by the continuous 

opacity monitoring system (COMS) for 

the duration of the planned MSS 

activities, and the work practices 

followed during the planned MSS 

activities. As discussed in the proposed 

action, EPA finds that these AOs do not 

specifically require sources to keep 

records of the parameters used to 

identify when startup or shutdown 

periods actually occur, such as 

temperature or unit load, or ESP 

operating parameters. The AOs also do 

not specifically require sources to keep 

records of the parameters that are 

monitored (e.g., air heater outlet 

temperature, drum metal temperature, 

periods when solid fuel is burned) to 

determine whether the ESP should be 

placed into or removed from service 

during these MSS periods. These are the 

types of specific monitoring records that 

are necessary to provide adequate 

information to evaluate when startup 

and shutdown periods actually occur or 

whether Chapter 111 requirements 

apply and evaluate compliance with the 

AO requirements regarding when the 

ESPs are required to be placed into or 

removed from service. A requirement to 

‘‘identify periods of planned MSS’’ and 

the ‘‘work practices followed’’ does not 

provide sufficient information to 

evaluate whether the facility accurately 

recorded the end of a startup or 

beginning of a shutdown event, or 

whether the ESP was engaged at the 

appropriate time during the startup 

process. Thus, the monitoring and 

recordkeeping requirements do not 

provide adequate information to 

evaluate when a startup event ends, and 

thus whether the AO or Chapter 111 

requirements should apply at a given 

time. Therefore, because there is no way 

to evaluate which requirements apply, 

there is no way to evaluate compliance 

with the applicable requirements. 

The commenter further states that the 

AO requirements are ‘‘all enforceable 

because each plant operator must 

maintain records demonstrating when 

the startup or shutdown periods occur, 

based on flue gas temperature at the 

ESP.’’ However, there is no specific 

requirement in the AOs for sources to 

record or maintain records of flue gas 

temperature. Thus, there are no records 

available to evaluate when the startup or 

shutdown periods occurred based on 

the flue gas temperature. Furthermore, 

only Oklaunion’s AO specifies a specific 

temperature (once the outlet gas 

temperature to the ESP is greater than 

300 °F) when the ESP should be placed 

into service. The AOs for the other 

seven facilities lack this level of 

specificity and are not enforceable 

because they require the ESP to be 

placed into service ‘‘as soon as 

practical.’’ This requirement is 

subjective, and it is unclear how the 

required recordkeeping would provide 

the necessary information to allow for 

verification that this requirement has 

been met. 

With respect to the commenter’s 

suggestion that EPA’s claims are 

speculative and not based on evidence 

of noncompliance with the identical 

terms contained in the plants’ NSR 

permits that have been in place for over 

10 years, this is not relevant to EPA’s 

conclusion that the relevant 

requirements do not have sufficient 

MRR requirements to provide the 

information necessary to be able to 

evaluate compliance with and enforce 

the requirements in the future. As 

explained, sufficient MRR requirements 

are necessary to provide adequate 

information to be able to evaluate 

compliance with the Chapter 111 and 

AO SSM-related requirements. Whether 

there is evidence of noncompliance 

with the permit terms that have been in 

place for 10 years in the past has no 

bearing on the ability to evaluate and 

enforce compliance with the relevant 

requirements in the future. 

Finally, commenters also claim that 

deviation reports required under the 

title V operating permits provide 

adequate information to determine 

compliance. Regardless of whether there 

are reporting requirements in the title V 

permits as the commenter claims, this 

does not resolve the deficiencies in the 

monitoring and recordkeeping 

requirements. In other words, a 

requirement to report monitoring and 

recordkeeping information that is not 

sufficient to provide the information 

needed to evaluate compliance with the 

applicable requirements is deficient. 

For the reasons explained, the 

relevant MRR requirements do not meet 

CAA and regulatory requirements and 

do not provide sufficient information to 

evaluate compliance with and enforce 

the specified rules. As discussed in the 

proposal and in response to other 

comments in this section, we are 

disapproving the SIP revision because 

the requirements in the AOs are overly 

vague and too subjective to provide for 

enforceability. The insufficient MRR 

requirements further reinforce the 

conclusion that the AOs are not 

enforceable as written. 

G. Comments on Section 110(l) and 

Interference With Attainment or 

Maintenance of the NAAQS 

Comment: One commenter (Sierra 

Club) commented that the 2020 SIP 

revision would relax the existing SIP, 

resulting in interference with attainment 

and maintenance of the NAAQS under 

CAA section 110(l). Therefore, Sierra 

Club contends that EPA must 

disapprove the SIP revision under CAA 

section 110(l), in addition to the 

rationale EPA provided at proposal. 

Specifically, Sierra Club pointed to 

language in our proposal that 

acknowledged that there is not textual 

evidence in the language of the 

regulations that indicate that the rules 

do not apply continuously, and thus 

this SIP revision would relax the 

existing SIP. Sierra Club goes on to say 

that Texas provided no modeling or 

other evidence that this SIP revision 

would not interfere with attainment or 

maintenance of the NAAQS to show 

compliance with CAA section 110(l). To 

further support their comment, Sierra 

Club provides modeling suggesting that 

in areas in near proximity to two of the 

facilities, there could be violations of 

the PM NAAQS due to emissions 

allowed under the 2020 SIP revision. 

Contrary to Sierra Club’s CAA section 

110(l) comment, two commenters, TCEQ 

and the Texas MSS Working Group, 

indicated that the rules in 30 TAC 111 

have never applied to these facilities 

during MSS. Further, the Texas MSS 

Working Group contends that Texas 

provided a ‘‘robust’’ demonstration 

under CAA section 110(l) The MSS 

Working Group also noted that EPA did 

not comment in its proposal on TCEQ’s 

CAA section 110(l) demonstration. 

One commenter, NRG, provided late 

comments (received October 9, 2024) 

indicating that the Sierra Club modeling 

showing potential PM NAAQS 

violations at its Limestone Electric 

Generating Station did not reflect its 

current operations which utilized 

cleaner fuels such sub-bituminous coal 

instead of lignite and natural gas during 

startup. NRG also argued that EPA’s 

original rationale was not based on 


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34We fully address these late comments in the 

RTC document. 

35This AO was submitted to EPA for approval as 

part of the SO2 NAAQS attainment SIP revision. 

EPA has not taken final action on that submittal at 

this time. See EPA proposed actions 89 FR 63117 

(Aug. 2, 2024) and 89 FR 68378 (Aug. 26, 2024). 

36See Section I and the RTC document for 

additional discussion of EPA’s review of the 

modeling 

37Bldg. Indus. Ass’n v. Norton, 247 F.23d 1241, 

1246 (D.C. Cir. 2001) (internal citations omitted). 

38Chemical Mfrs. Ass’n. v. EPA, 870 F.2d 177, 

203 (5th Cir. 1989) (internal citations omitted). 

potential NAAQS violations and that to 

rely on Sierra Club’s modeling, the 

Agency must reopen the public 

comment period. Luminant also 

submitted late comments (received 

November 22, 2024) that were similar to 

NRG’s comments.34

Response: EPA agrees that CAA 

section 110(l) is relevant to all SIP 

revisions and that it makes clear that the 

Administrator may not approve a SIP 

revision if it would interfere with 

attainment or maintenance of the Act. 

EPA, however, did not base its proposed 

disapproval on CAA section 110(l). 

Instead, we based our proposed 

disapproval on concerns, discussed 

elsewhere, with the enforceability and 

continuousness of the AOs provided in 

the 2020 SIP revision. In this action, we 

are finalizing our determination that the 

AOs are (1) not enforceable and (2) it is 

necessary or appropriate for the AOs 

and provisions in 30 TAC 111 to be 

emissions limitations, and they are not 

continuous in violation of the CAA. 

While our disapproval is not based on 

failure to meet CAA section 110(l) 

requirements, we do believe that Sierra 

Club’s modeling provides ample 

evidence that the TCEQ 110(l) 

demonstration is not adequate to 

determine that the SIP revision does not 

interfere with attainment and 

maintenance of the NAAQS. In other 

words, Sierra Club’s modeling confirms 

that we are prohibited from approving 

this submission. TCEQ’s 110(l) 

demonstration is based on two 

arguments. First, TCEQ claims that MSS 

emissions have always been occurring 

from these facilities and never were 

controlled by the ESPs used by these 

facilities for control. Second, TCEQ 

states that there has never been 

evidence detected by Texas’s PM 

ambient monitoring network of any PM 

NAAQS violations. Sierra Club provides 

modeling for two of the facilities 

covered by the 2020 SIP revision that 

indicates that violations of the NAAQS 

are possible, both under the sources’ 

current practices, and to an even greater 

extent if emissions are uncontrolled 

during MSS to the extent allowed under 

the AOs in the 2020 SIP revision. It is 

worth pointing out that Texas did not 

provide modeling with this SIP revision. 

Sierra Club’s modeling makes clear that 

any potential violations of the PM 

standard as a result of MSS emissions 

would be much closer to the facilities 

than any of the monitors Texas points 

to in its 110(l) demonstration. In the 

absence of relevant monitoring data, 

modeling has long been utilized to 

estimate impacts of facilities on air 

quality. In this case, Sierra Club used 

EPA’s preferred model, AERMOD, and 

modeled the impact of two of the 

facilities at 25%, 50%, 75%, and 100% 

load assuming combustion of lignite and 

separately combustion of subbituminous coal and considering that 

the ESP would not be energized during 

MSS. The modeling indicates that PM2.5

MSS emissions could potentially result 

in modeled values above the 24-hour 

PM2.5 NAAQS and the annual PM2.5

NAAQS. This modeling also suggests 

that a similar modeling analysis of 

maximum MSS emissions from the 

other power plant facilities at issue here 

could potentially result in violations of 

the NAAQS. Violations of the standard 

were indicated at both facilities 

modeled, with higher concentrations 

modeled when burning lignite. See 

response to Comments on Air 

Dispersion Modeling Results in this 

document and the RTC Document for 

full evaluation and discussion of the 

model results. 

Although the Limestone facility has 

not burned lignite since December 2017, 

the Limestone units are not restricted by 

permit or rule from the types of fossil 

fuels that can be fired in its boilers. The 

Martin Lake facility entered into an AO 

in early 2022 that prohibits the facility 

from burning lignite, but that 

requirement is currently not federally 

enforceable.35 EPA’s review of the 

modeling did not detect any significant 

issues with the modeling techniques 

themselves or the conclusions, although 

refinements could be performed.36 NRG 

claimed that its Limestone facility uses 

natural gas during startup to comply 

with EPA’s MATS rules and that the 

ESPs are placed into service 

‘‘contemporaneous to solid fuel firing’’, 

which would certainly reduce PM 

emissions to very low levels during this 

period of operation. However, there is 

no SIP requirement or requirement in 

the submitted AO that NRG is required 

to burn only natural gas at startup or 

that would prohibit the burning of solid 

fuel prior to placing the ESP into 

service. Additionally, there is no 

requirement to burn only subbituminous coal rather than lignite in 

the SIP or the AOs. NRG could decide 

to change their practices if they are not 

required to take such emissionsreducing measures in the SIP. In 

addition, this further highlights the 

specific, enforceable measures available 

to the source such as prohibiting 

burning solid fuel until the ESP is in 

service, in contrast to the vague 

requirements actually included in the 

AOs such as ‘‘placing the ESP into 

service as soon as practical’’ or 

‘‘operating the facilities and associated 

air pollution control equipment in 

accordance with good air pollution 

control practices.’’ 

In sum, while Sierra Club’s modeling 

confirms that EPA is prohibited from 

approving this SIP revision, it is 

unnecessary for EPA to base its 

disapproval on failure to comply with 

section 110(l) requirements. An 

approvable SIP revision would need to 

confirm that the revision would not 

interfere with attainment or 

maintenance of the NAAQS or any other 

applicable CAA requirement. In the 

absence of monitoring data from 

monitors located closer to the facilities, 

such a demonstration would most likely 

need modeling. Sierra Club’s modeling 

makes clear that such a demonstration 

would depend on the type of coal or 

other fuel used during startup, and 

those fuel requirements would need to 

be made enforceable to ensure the SIP 

revision did not interfere with 

attainment or maintenance. 

In response to NRG’s late comment 

that EPA is not providing sufficient 

notice and must open a new public 

comment period, it is not required that 

the Agency repropose every time a 

comment raises new evidence to 

consider. ‘‘To avoid perpetual cycles of 

new notice and comment periods, a 

final rule that is a logical outgrowth of 

the proposal does not require an 

additional round of notice and comment 

even if the final rule relies on data 

submitted during the comment 

period.’’ 37 EPA’s final action here is in 

substance exactly the same as its 

proposal—as the Agency has made 

clear, these AO requirements are not 

enforceable or continuous and allow for 

periods of unlimited emissions. Sierra 

Club’s modeling is evidence that the 

emissions can interfere with attainment 

or maintenance of the NAAQS. EPA 

‘‘fairly apprise[d] interested persons of 

the subjects and issues’’ the Agency 

considered; ‘‘the notice need not 

specifically identify every precise 

proposal which the agency may 

ultimately adopt as final rule.’’ 38


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39There are PM2.5 monitors in Harrison, Potter 

and Atascosa Counties where the Southwestern 

Electric Power Company H.W. Pirkey, San Miguel 

Electric Cooperative, Inc. San Miguel and 

Southwestern Public Service Company Harrington 

Station are respective located. 

40 Guideline on Air Quality Models versions 

including 40 CFR part 51 Appendix W (current 

version published November 2024 (FR Vol. 89, No. 

230, November 29, 2024, 95034–95075). The EPA 

originally published the Guideline in April 1978 

(EPA–450/2–78–027). The EPA revised the 

Guideline in 1986 (51 FR 32176) and updated it 

with supplement A in 1987 (53 FR 32081), 

supplement B in July 1993 (58 FR 38816), and 

supplement C in August 1995 (60 FR 40465). The 

EPA published the Guideline as Appendix W to 40 

CFR part 51 when the EPA issued supplement B. 

The EPA republished the Guideline in August 1996 

(61 FR 41838) to adopt the CFR system for labeling 

paragraphs. The EPA also published updated 

Guideline in 2003, 2005, and 2017. 

41SO2 designations FR cities including Federal 

Register Vol. 81, No. 133, July 12, 2016, 45039– 

45055; Federal Register Vol. 81, No. 239, December 

13, 2016, 89870–89876; Federal Register Vol. 83, 

No. 6, January 9, 2018, 1098–1172. 

42Lead Designations FR Vol. 75, No. 244, 

November 22, 2010, and Texas Area Designations 

for the 2008 Lead National Ambient Air Quality 

Standards. 

43 40 CFR part 51 App. W Sections 1.0, 4.0 

(including 4.2.2.1 and 4.2.3.5), and Appendix A to 

Appendix W of Part 51 Summaries of Preferred Air 

Quality Models (Section A.1) 

44See also Galveston-Houston Assoc. for Smog 

Prevention v. EPA, 289 Fed. Appx. 745, 754 (5th 

Cir. 2008) (upholding use of modeling rather than 

monitoring data). 

45 Id. at 291 (citing to BCCA Appeal Grp. v. EPA, 

355 F.3d 817, 824 (5th Cir. 2003) and American 

Petroleum Inst. v. EPA, 787 F.2d 965, 983 (5th Cir. 

1986)); see also Huntsman Petrochemical LLC v. 

EPA, 114 F.4th 727 (D.C. Cir. 2024). 

46 Id. at 293. 

47We fully address these late comments from 

NRG and Luminant in the RTC document. 

H. Comments on the Use of Air 

Dispersion Modeling 

Comment: Sierra Club commented 

that air quality dispersion modeling is a 

technically appropriate, efficient, and 

readily available technique for 

evaluating air quality impacts associated 

with SIP submittals and revisions. 

Sierra Club pointed out that EPA has 

identified the AERMOD steady-state 

plume dispersion model as the Agency’s 

default model for the assessment of both 

primary and secondary particulate 

matter concentrations from large point 

sources. Sierra Club also indicated that 

EPA has recognized in analogous 

circumstances, monitoring alone is not 

generally adequate for identifying the 

maximum concentration of particulate 

matter impacts from large sources 

‘‘[d]ue to the generally localized 

impacts’’ from those sources, and the 

lack of nearby monitors. Sierra Club also 

cited to TCEQ’s air monitoring network 

plan, that indicates that there are no PM 

air quality monitors in the vicinity of 

any of the facilities at issue in this 

proposal, or even in the same county. 

Sierra Club continued that the use of air 

dispersion modeling is also consistent 

with the Agency’s historic use of such 

modeling for determining compliance 

with the NAAQS and the use of 

dispersion modeling to demonstrate 

attainment with the NAAQS is also 

court-validated. Sierra Club summarized 

that the use of scientifically and legally 

supported air quality dispersion 

modeling (AERMOD in this case) to 

characterize and evaluate the air quality 

impacts of Texas’s 2020 SIP revision, 

including the worst-case emissions from 

MSS operations at those facilities is not 

only consistent with EPA’s Appendix W 

guidance, but it is well supported by 

EPA’s lengthy and court-validated 

history of using AERMOD as a tool for 

evaluating individual source 

compliance with the NAAQS and is 

technically appropriate and supported 

by EPA regulations and guidance. 

Response: As discussed in more detail 

in the RTC document for this action, 

there are no PM2.5 monitors located 

within 50 km of either Luminant’s 

Martin Lake or NRG’s Limestone 

facility. We note that three of the eight 

facilities do have PM2.5 monitors located 

in the same county, but those monitors 

are not sited near the facilities, with the 

closest being 17 kilometers from the 

facility.39 Maximum modeled primary 

PM concentrations are usually within 

three kilometers of the source and then 

concentrations drop off quickly with 

increasing distance for these types of 

facilities in semi-flat terrain. Therefore, 

none of the PM2.5 monitors have been 

sited to pick up the maximum impacts 

near the sources covered by the 2020 

SIP revision; therefore, it is necessary to 

utilize area specific modeling to 

estimate PM2.5 air quality levels around 

these facilities. EPA has utilized 

modeling to assess air quality standards 

for single facilities in permitting actions, 

SIPs, enforcement cases, and 

designations since the 1970s.40 For 

example, EPA relied on modeling from 

States, industry, and third-party 

modeling performed by Sierra Club and 

others during the 1-hour SO2

designations for Round 2 and Round 3 

designations to assess areas should be 

designated nonattainment or attainment 

and also to assess the appropriate 

boundaries for the nonattainment 

areas.41 EPA also relied on modeling 

from States and industry in 2008 Lead 

NAAQS designations.42 Modeling 

provides the ability to assess the air 

quality in areas around facilities 

because it is impractical to site monitors 

everywhere. EPA concurs that modeling 

with AERMOD in this case is the 

appropriate model to use and is an 

appropriate technique, scientifically and 

legally, to analyze primary pollutant 

concentrations of PM2.5 in the areas 

around these facilities when they have 

MSS emissions.43

In addition to the citations provided 

by Sierra Club, EPA’s reliance on 

modeling rather than monitoring data 

was recently upheld by the 5th Circuit 

in Texas v. EPA, 91 F.4th 280 (5th Cir. 

2024).44 The court highlighted that 

review of an agency’s evaluation of 

complex scientific data within its 

technical expertise—such as the 

decision whether to use modeling or 

monitoring data in evaluating possible 

attainment issues—is extremely 

deferential, and that there is a 

‘presumption of regularity’ that is 

difficult for challenging parties to 

overcome.45 The court applied that 

standard and found that EPA did not act 

arbitrarily or capriciously in relying on 

modeling data despite the existence of 

monitoring data.46

I. Comments on Results of Air 

Dispersion Modeling 

Comment: Sierra Club indicated that 

EPA must consider credible third-party 

modeling. Sierra Club has submitted 

modeling of ‘‘worst case’’ MSS potential 

emissions rates for boilers at two of the 

facilities (Luminant’s Martin Lake 

facility and NRG’s Limestone facility) 

for multiple load levels spanning from 

10% load to 100% load. Sierra Club 

concludes that the modeling results 

credibly demonstrate that effectively 

uncontrolled PM emissions from Martin 

Lake and Limestone plants during MSS 

periods, as would be allowed under 

Texas’s proposed 2020 SIP revision and 

its Agreed Orders, could result in 

violations of the annual and 24-hour 

NAAQS for PM2.5 in areas surrounding 

these two facilities. Sierra Club did not 

model whether MSS emissions from the 

other power plant facilities at issue here 

could cause violations of the NAAQS, 

but the modeling results for Martin Lake 

and Limestone suggest that MSS 

emissions at the other facilities could 

result in violations of the NAAQS. 

NRG provided late comments 

(received October 9, 2024) indicating 

that the Sierra Club modeling showing 

potential PM NAAQS violations at its 

Limestone Electric Generating Station 

overstates Limestone’s emissions. 

Luminant also submitted late comments 

(received November 23, 2024) on the 

modeled emission rates and modeling 

results.47

Response: The EPA obtained the 

modeling files from Sierra Club (SC) and 

has reviewed both the reports from 

Wingra (Sierra Club’s contractor) and 


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48 40 CFR part 50.20 and 40 CFR part 50 

Appendix N. 40 CFR part 50.20(b) ‘‘The primary 

annual PM2.5 standard is met when the annual 

arithmetic mean concentration, as determined in 

accordance with appendix N to this part, is less 

than or equal to 9.0 mg/m3.: 40 CFR part 50.20(c) 

‘‘The primary 24-hour PM2.5 standard is met when 

the 98th percentile 24-hour concentration, as 

determined in accordance with appendix N to this 

part, is less than or equal to 35 mg/m3.’’ 40 CFR part 

50 Appendix N clarifies the specific procedures for 

calculating the PM2.5 design values. See Appendix 

N for details, but in general the PM2.5 annual 

NAAQS design value is the average of three 

consecutive years annual arithmetic mean 

concentrations, and the PM2.5 24-hour NAAQS 

design value is the average of three consecutive 

years of the annual 98th percentile of 24-hour 

values. 

49As discussed elsewhere, Texas issued permits 

to these facilities to address emissions during MSS. 

The permits were not submitted as part of this SIP 

revision. The permits include lb/hour and ton/year 

emission rate limits that are not included in the SIP 

revision and thus are not specifically being 

reviewed in this action but are discussed here as a 

reference point for the reasonableness of Sierra 

Club’s assumptions. 

50We also note that EPA’s guidance in assessing 

PM2.5 impacts is to also include the secondary 

formation of PM2.5 due to precursor emissions (i.e. 

NOX and SO2). Including the secondary formation 

of PM2.5 would be expected to have some increase 

in the overall maximum modeled concentration. 

See Guidance on the Development of Modeled 

Emission Rates for Precursors (MERPs) as a Tier 1 

Demonstration Tool for Ozone and PM2.5 under the 

PSD Permitting Program (pdf) (3.36 MB, 04/30/ 

2019, 454–R–19–003). Available for download at 

https://www.epa.gov/nsr/guidance-developmentmodeled-emission-rates-precursors-merps-tier-1- 

demonstration-tool-ozone 

51 Design Values for PM2.5 Annual and 24-Hour 

NAAQS are calculated in accordance with 40 CFR 

part 50 Appendix N using monitoring data collected 

and the Design Values are compared to the PM2.5

Annual and 24-Hour NAAQS (40 CFR part 50.20) 

to determine whether the design value meets or 

exceeds the applicable PM2.5 NAAQS. See 

Appendix N for details, but in general the PM2.5

annual NAAQS design value is the average of three 

consecutive years annual arithmetic mean 

concentrations, and the PM2.5 24-hour NAAQS 

design value is the average of three consecutive 

years of the annual 98th percentile of 24-hour 

values. 

the modeling files for modeling of MSS 

emissions from Luminant’s Martin Lake 

facility and NRG’s Limestone facility. 

EPA reviewed the different components 

of the modeling and found that overall, 

it is informative and does indicate that 

‘‘worst case’’ MSS emissions could 

result in modeled violations. EPA is 

including a summary of two key 

elements of our review related to the 

emission rates modeled and the 

representative background monitoring 

concentration added to modeled values 

here, and note that our full review of all 

the Sierra Club modeling and results are 

included in the RTC document available 

in the docket for this action. 

The SIP revision and the AOs for 

these two facilities do not include any 

numerical limits on the maximum 

pounds per hour (lb/hr) that could be 

emitted from each boiler during MSS. 

As discussed in Section II.F.2, the SIP 

revision with its AOs does not include 

limits on the frequency of startup and 

shutdown events so there is no 

restriction to the total number of hours 

per year that the boilers at a facility can 

be in a normal MSS operation situation; 

therefore, they could operate a large 

number of hours per year and the MSS 

emissions could potentially impact the 

24-hour PM2.5 NAAQS and the annual 

PM2.5 NAAQS. Sierra Club modeled 

MSS emissions for every hour of the 

year and based on the lack of limits on 

hours of operation per year in MSS 

mode, we find this assumption to be 

reasonable, especially when analyzing 

the 24-hour PM2.5 NAAQS, which is 

based on the very high end (98th 

percentile) of 24-hour average 

concentrations in a year.48 As a check 

on the reasonableness of Sierra Club’s 

assumptions, EPA reviewed Sierra 

Club’s modeled emission rates, 

compared that with the MSS emission 

limits included in the facilities’ MSS 

permits,49 and found the Sierra Club’s 

emission rates were similar or less than 

the PM2.5 lb/hr emission limits in the 

permits for NRG Limestone. As 

discussed in the RTC document, we also 

find that the modeled emission rates for 

Martin Lake are also reasonable. EPA 

has not fully reviewed the PM2.5 lb/hr 

emission limits and the underlying 

assumptions and calculations in the 

MSS permits for these two facilities to 

evaluate if they are representative of the 

maximum emissions that could occur 

during MSS but note that some of the 

other associated limits in the permits 

(i.e. ash content and sulfur content 

limits) indicate that the maximum 

emission rates could be larger/higher 

using EPA’s emission factors. If higher 

emission rates are possible during MSS, 

then Sierra Club’s maximum modeled 

concentrations would also be expected 

to be higher if appropriately adjusted 

and remodeled.50

Modeled ambient concentrations are 

estimated by adding the modeled values 

to a representative background 

concentration from a representative 

monitor which represents 

concentrations from non-modeled 

sources and general PM2.5 background 

levels in the area. EPA’s review found 

that Sierra Club used the lowest PM2.5

monitored design values 51 in the State 

of Texas, which are significantly lower 

than PM2.5 monitored design values at 

monitors located closer to these two 

facilities. Monitored design values from 

these closer monitors should have been 

added to the modeling because they 

would be more representative of 

regional PM2.5 background 

concentrations than the low values 

Sierra Club utilized. Using the more 

representative background monitored 

design value concentrations for 

Limestone and Martin Lake results in 

higher maximum modeled design values 

and more of Sierra Club’s operating 

scenarios having maximum design 

values that exceed the 24-hour and 

annual PM2.5 NAAQS. 

EPA notes that Sierra Club’s modeling 

scenarios were based on both boilers at 

Limestone or the three boilers at Martin 

Lake having MSS emissions at the same 

time. Those scenarios may not be 

expected to occur often, but the scenario 

is not limited by the current SIP 

revision or AOs, nor by the MSS 

permits. The modeling for some of the 

operating scenarios was sufficiently 

above the NAAQS such that additional 

modeling may show that not all the 

boilers at a facility must have MSS 

emissions at the same time for modeled 

violations to occur. 

Overall, EPA’s review indicates that 

while there are some uncertainties 

regarding what potential maximum 

(worst case) MSS emission rates should 

be modeled and that a higher 

background monitor DVs should have 

been used, the Sierra Club’s modeling is 

informative and indicates that PM2.5

MSS emissions allowed under the 2020 

SIP revision and AOs could result in 

modeled values above the 24-hour PM2.5

NAAQS and the annual PM2.5 NAAQS. 

This modeling also suggests that a 

similar modeling analysis of maximum 

MSS emissions from the other power 

plant facilities at issue here could 

possibly result in violations of the 

NAAQS because these other facilities 

are similar in the general magnitude of 

potential hourly MSS emissions and 

have somewhat similar stack parameters 

(stack velocity, temperature and height). 

J. Other 

1. Change in Facility Operations 

Comment: The commenter (TCEQ) 

states that four plants (Gibbons Creek 

Steam Electric Station, Pirkey Power 

Plant, Oklaunion Power Station, and 

Harrington Station) have either ceased 

burning coal, shut down, or converted 

to natural gas for power generation; 

therefore, making these AOs and their 

approval into the SIP unnecessary. The 

commenter also states that EPA should 

approve the other four AOs (Lower 

Colorado River Authority’s Sam 

Seymour Fayette Power Project (order 

no. 2020–0077–SIP); Luminant 

Generation Company, LLC’s Martin 

Lake Steam Electric Station (order no. 

2020–0076–SIP); NRG Texas Power 

LLC’s Limestone Electric Generation 


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52See https://www.epa.gov/air-qualitymanagement-process/managing-air-quality-humanhealth-environmental-and-economic#what 

(accessed dated 02/05/2024). 

Station (order no. 2020–0075–SIP); and 

San Miguel Electric Cooperative, Inc.’s 

San Miguel Electric Plant (order no. 

2020–0074–SIP) into the SIP. 

Response: TCEQ can formally 

withdraw the AOs (i.e., a partial 

withdrawal of its submitted SIP 

revision) that TCEQ believes are no 

longer necessary to be included as part 

of the Texas SIP. As long as the SIP 

revision is before us, we are legally 

obligated to act on that submission, 

either by approving or disapproving it. 

Moreover, we must act on the entire SIP 

revision and cannot parse out pieces 

and take no action. For the reasons 

described in this final rule and 

responses to other comments, EPA is 

disapproving Texas’s 2020 SIP revision, 

including the accompanying AOs. 

2. EPA Comments on the State’s 

Proposed SIP 

Comment: The commenter states that 

EPA failed to raise concerns regarding 

‘legal and practical enforceability,’ 

continuity of the limitations, or 

compliance with AEL guidance during 

the commission’s public comment 

period on the proposed AOs and the 

2020 SIP revision. The commenter then 

states that EPA’s failure to raise 

concerns about legal and practical 

enforceability, continuity of the limits, 

or failure to meet certain factors from 

their AEL guidance indicates EPA 

agreed with TCEQ’s assessment that the 

AOs should be incorporated into the 

SIP. 

Response: EPA disagrees with the 

commenter’s assertion that EPA not 

providing comments during TCEQ’s 

public comment period on its proposed 

SIP regarding concerns about legal and 

practical enforceability, continuity of 

the limits, or failure to consider certain 

factors from their AEL guidance 

indicates that EPA agreed with TCEQ’s 

assessment that the AOs should be 

incorporated into the SIP. EPA must 

follow CAA requirements and conduct a 

formal review of the submitted SIP 

revision, regardless of whether 

particular objections were raised during 

a proceeding before the SIP was 

submitted to the Agency. 

3. EPA Interpretation of 30 TAC 111 

Comment: The commenters state that 

EPA repeatedly acknowledged TCEQ’s 

interpretation and characterization of its 

rules in 30 TAC 111, including that 

limits on opacity and PM do not apply 

during periods of SSM for these specific 

units. 

Response: The commenters 

misconstrue EPA’s statements on 

TCEQ’s interpretation and 

characterization of its rules in 30 TAC 

111 as acceptance and agreement of its 

interpretation and characterization. 

While EPA acknowledged TCEQ’s 

interpretation in the proposal, we also 

acknowledged that there is no textual 

evidence in the rule to provide evidence 

of TCEQ’s interpretation. We also point 

out in other comments that this is the 

first time in a SIP revision that TCEQ 

has put forward this interpretation. The 

stated goal of this SIP revision was to 

provide continuous federally 

enforceable emission limitations under 

TCEQ’s interpretation that the rules in 

Chapter 111 do not apply during MSS 

for coal fired electric generating units 

using ESPs. Without adding provisions 

to the SIP to address time periods of 

MSS, the requirements during MSS and 

more importantly the duration of time 

when the chapter 111 rules would not 

apply under the TCEQ interpretation 

will continue to be unclear. 

4. Misconception of Action as a SIP Call 

Comment: The commenter states that 

the proposal indicates that Texas 

provisions were previously approved 

and incorporated into operating permits. 

The commenter cites to CAA section 

110(k), stating that the CAA imposes a 

heavy burden of proof for EPA 

disapproval of an already approved SIP 

revision. The commenter states that EPA 

has a heavy burden of proof to show 

that previously approved SIP provisions 

are ‘‘substantially inadequate’’ to meet 

the relevant provisions of the Act and 

must be revised, and EPA failed meet 

this burden and therefore must approve 

the provisions at issue here. 

Response: The commenter appears to 

mistakenly be stating that EPA is 

proposing disapproval of already 

approved provisions in the SIP or 

issuing a SIP call under CAA section 

110(k)(5). However, the commenter also 

states later that EPA must approve the 

provisions at issue here. EPA is 

clarifying that (1) EPA did not propose 

disapproval of an already approved SIP 

revision or propose to find an approved 

SIP provision to be ‘‘substantially 

inadequate’’ and (2) CAA section 

110(k)(5) is not applicable in this 

context, neither in the proposal or this 

final rule. TCEQ submitted a SIP 

revision and after our evaluation, we 

proposed disapproval of that SIP 

revision and its provisions as not 

meeting the requirements of the Act. 

III. Final Action 

We are disapproving a revision to the 

Texas SIP submitted by TCEQ on 

August 20, 2020 (concerning opacity 

and PM emissions during planned MSS 

activities for certain EGU sources 

equipped with ESPs as the PM control 

device). These EGUs are the 

Southwestern Electric Power Company 

(SWEPCO) H.W. Pirkey Power Plant; the 

Lower Colorado River Authority (LCRA) 

Sam Seymour Fayette Power Project; the 

Luminant Generation Company, LLC 

Martin Lake Steam Electric Station; the 

NRG Texas Power, LLC Limestone 

Electric Generating Station; the San 

Miguel Electric Cooperative, Inc. San 

Miguel Plant; the Southwestern Public 

Service Company (SPS) Harrington 

Station; the Texas Municipal Power 

Agency (TMPA) Gibbons Creek Steam 

Electric Station; and the Public Service 

Company of Oklahoma (PSCO) 

Oklaunion Power Station. 

The Agreed Orders will not be 

incorporated into the SIP. There will be 

no sanctions or FIP clocks as a result of 

this action. 

IV. Environmental Justice 

Considerations 

Information on Executive Order 12898 

(Federal Actions to Address 

Environmental Justice in Minority 

Populations and Low-Income 

Populations, 59 FR 7629, February 16, 

1994), Executive Order 14096 

(Revitalizing Our Nation’s Commitment 

to Environmental Justice for All, 88 FR 

25251, April 26, 2023), and how EPA 

defines environmental justice (EJ) can 

be found in the section below titled 

‘‘Statutory and Executive Order 

Reviews.’’ For informational and 

transparency purposes only, EPA 

included in its proposal additional 

analysis of EJ associated with this 

proposed action for the purpose of 

providing information to the public (89 

FR 71237). 

Communities in close proximity to 

and/or downwind of these EGUs may be 

subject to environmental impacts of 

emissions. Short- and/or long-term 

exposure to air pollution has been 

associated with a wide range of human 

health effects including increased 

respiratory symptoms, hospitalization 

for heart or lung diseases, and even 

premature death.52 Emissions during 

planned MSS may be higher than 

emissions under normal steady-state 

operations. The EPA believes that the 

human health or environmental risk 

addressed by this action will not likely 

have disproportionately high and 

adverse human health or environmental 

effects on communities with EJ 

concerns. This action merely 

disapproves a SIP revision as not 

meeting the CAA requirements. We 


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53 42 U.S.C. 7410(k); 40 CFR 52.02(a). 

therefore determine that this rulemaking 

action will not have disproportionately 

high or adverse human health or 

environmental effects on communities 

with EJ concerns. 

V. Statutory and Executive Order 

Reviews 

Under the Act, the Administrator is 

required to approve a SIP submission 

that complies with the provisions of the 

Act and applicable Federal 

regulations.53 Thus, in reviewing SIP 

submissions, EPA’s role is to approve 

State choices, provided that they meet 

the criteria of the Act. Accordingly, this 

action disapproves Texas’s 2020 SIP 

revision as not meeting applicable 

requirements of the CAA. 

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, Executive Order 

13563: Improving Regulation and 

Regulatory Review, and Executive Order 

14094: Modernizing Regulatory Review 

This action is not a significant 

regulatory action as defined in 

Executive Order 12866 (58 FR 51735, 

October 4, 1993), as amended by 

Executive Order 14094 (88 FR 21879, 

April 11, 2023), and was therefore not 

subject to a requirement for Executive 

Order 12866 review. 

B. Paperwork Reduction Act (PRA) 

This action does not impose an 

information collection burden under the 

PRA (44 U.S.C. 3501 et seq.) because it 

does not contain any information 

collection activities. 

C. Regulatory Flexibility Act (RFA) 

This action is certified to not have a 

significant economic impact on a 

substantial number of small entities 

under the RFA (5 U.S.C. 601 et seq.). 

This action will not impose any 

requirements on small entities. 

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 imposes no 

enforceable duty on any State, local, or 

Tribal governments or the private sector. 

E. Executive Order 13132: Federalism 

This action does not have federalism 

implications as specified in Executive 

Order 13132 (64 FR 43255, August 10, 

1999). 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 has no Tribal implications 

as specified in E.O. 13175 (65 FR 67249, 

November 9, 2000). This action will 

neither impose substantial direct 

compliance costs on federally 

recognized Tribal governments, nor 

preempt Tribal law. This action will not 

impose substantial direct compliance 

costs on federally recognized Tribal 

governments because no actions will be 

required of Tribal governments. This 

action will also not preempt Tribal law 

as it does not have applicable or related 

Tribal laws. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

EPA interprets Executive Order 13045 

(62 FR 19885, April 23, 1997) as 

applying only to those regulatory 

actions that concern environmental 

health or safety risks that EPA has 

reason to believe may 

disproportionately affect children, per 

the definitions 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 disapproves a SIP 

revision. 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 (66 FR 28355, May 22, 

2001), 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. This action is not subject to 

the requirements of section 12(d) of the 

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

application of those requirements would 

be inconsistent with the CAA. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Population 

Executive Order 12898 (Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations, 59 FR 7629, 

Feb. 16, 1994) directs Federal agencies 

to identify and address 

‘‘disproportionately high and adverse 

human health or environmental effects’’ 

of their actions on communities with 

environmental justice (EJ) concerns to 

the greatest extent practicable and 

permitted by law. Executive Order 

14096 (Revitalizing Our Nation’s 

Commitment to Environmental Justice 

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

builds on and supplements E.O. 12898 

and defines EJ as, among other things, 

‘‘the just treatment and meaningful 

involvement of all people, regardless of 

income, race, color, national origin, or 

Tribal affiliation, or disability in agency 

decision-making and other Federal 

activities that affect human health and 

the environment.’’ 

The air agency did not evaluate 

environmental justice considerations as 

part of its 2020 SIP revision; the CAA 

and applicable implementing 

regulations neither prohibit nor require 

such an evaluation. The EPA performed 

an environmental justice analysis, as is 

described above in the section titled, 

‘‘Environmental Justice 

Considerations.’’ The analysis was done 

for the purpose of providing additional 

context and information about this 

rulemaking to the public, not as a basis 

of the action. Due to the nature of the 

action being taken here, this action is 

expected to have no impact on the air 

quality of the affected area. In addition, 

there is no information in the record 

upon which this decision is based 

inconsistent with the stated goal of E.O. 

12898 of achieving environmental 

justice for communities with EJ 

concerns. 

This action is subject to the 

Congressional Review Act, 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). 

Under section 307(b)(1) of the Clean 

Air Act, 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 action for the purposes of judicial 

review nor does it extend the time 


ddrumheller on DSK120RN23PROD with RULES1
Federal Register / Vol. 89, No. 245 / Friday, December 20, 2024 / Rules and Regulations 104059 

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, Carbon monoxide, 

Hydrocarbons, Incorporation by 

reference, Intergovernmental relations, 

Lead, Nitrogen dioxide, Particulate 

matter, Sulfur dioxide, Reporting and 

recordkeeping requirements, Volatile 

organic compounds. 

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

Dated: December 12, 2024. 

Earthea Nance, 

Regional Administrator, Region 6. 

[FR Doc. 2024–29956 Filed 12–19–24; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R04–OAR–2023–0501; FRL–12273– 

01–R4] 

Air Plan Approval; Georgia; Update to 

Materials Incorporated by Reference 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Final rule; notification of 

administrative change. 

SUMMARY: The Environmental Protection 

Agency (EPA) is updating the materials 

that are incorporated by reference (IBR) 

into the Georgia State Implementation 

Plan (SIP). The regulations affected by 

this update have been previously 

submitted by Georgia and approved by 

EPA. In this notice, EPA is also 

notifying the public of corrections to the 

Code of Federal Regulations (CFR) 

tables that identify material 

incorporated by reference into the 

Georgia SIP. This update affects the 

materials that are available for public 

inspection at the National Archives and 

Records Administration (NARA) and the 

EPA Regional Office. 

DATES: This action is effective December 

20, 2024. 

ADDRESSES: The SIP materials whose 

incorporation by reference into 40 CFR 

part 52 is finalized through this action 

are available for inspection at the 

following locations: Environmental 

Protection Agency, Region 4, 61 Forsyth 

Street SW, Atlanta, GA 30303; and 

www.regulations.gov. To view the 

materials at the Region 4 Office, EPA 

requests that you email the contact 

listed in the FOR FURTHER INFORMATION

CONTACT section to schedule your 

inspection. The Regional Office’s 

official hours of business are Monday 

through Friday 8:30 a.m. to 4:30 p.m., 

excluding Federal holidays. 

FOR FURTHER INFORMATION CONTACT: 

Josue Ortiz Borrero, Air Regulatory 

Management Section, Air Planning and 

Implementation Branch, Air and 

Radiation Division, U.S. Environmental 

Protection Agency, Region 4, 61 Forsyth 

Street SW, Atlanta, Georgia 30303–8960. 

Mr. Josue Ortiz Borrero can be reached 

via telephone at (404) 562–8085 or via 

electronic mail at ortizborrero.josue@

epa.gov. 

SUPPLEMENTARY INFORMATION: 

I. Background 

Each State has a SIP containing the 

control measures and strategies used to 

attain and maintain the national 

ambient air quality standards (NAAQS). 

The SIP is extensive, containing such 

elements as air pollution control 

regulations, emission inventories, 

monitoring networks, attainment 

demonstrations, and enforcement 

mechanisms. 

Each State must formally adopt the 

control measures and strategies in the 

SIP after the public has had an 

opportunity to comment on them and 

then submit the proposed SIP revisions 

to EPA. Once these control measures 

and strategies are approved by EPA, and 

after notice and comment, they are 

incorporated into the federallyapproved SIP and are identified in part 

52, ‘‘Approval and Promulgation of 

Implementation Plans,’’ title 40 of the 

Code of Federal Regulations (40 CFR 

part 52). The full text of the State 

regulation approved by EPA is not 

reproduced in its entirety in 40 CFR part 

52 but is ‘‘incorporated by reference.’’ 

This means that EPA has approved a 

given State regulation or specified 

changes to the given regulation with a 

specific effective date. The public is 

referred to the location of the full text 

version should they want to know 

which measures are contained in a 

given SIP. The information provided 

allows EPA and the public to monitor 

the extent to which a State implements 

a SIP to attain and maintain the NAAQS 

and to take enforcement action for 

violations of the SIP. 

The SIP is a living document which 

the State can revise as necessary to 

address the unique air pollution 

problems in the State. Therefore, EPA 

from time to time must take action on 

proposed revisions containing new or 

revised State regulations. A submission 

from a State can revise one or more 

rules in their entirety or portions of 

rules. The State indicates the changes in 

the submission (such as by using 

redline/strikethrough text) and EPA 

then takes action on the requested 

changes. EPA establishes a docket for its 

actions using a unique Docket 

Identification Number, which is listed 

in each action. These dockets and the 

complete submission are available for 

viewing on www.regulations.gov. 

On May 22, 1997 (62 FR 27968), EPA 

revised the procedures for incorporating 

by reference, into the Code of Federal 

Regulations, materials approved by EPA 

into each SIP. These changes revised the 

format for the identification of the SIP 

in 40 CFR part 52, streamlined the 

mechanisms for announcing EPA 

approval of revisions to a SIP, and 

streamlined the mechanisms for EPA’s 

updating of the IBR information 

contained for each SIP in 40 CFR part 

52. The revised procedures also called 

for EPA to maintain ‘‘SIP Compilations’’ 

that contain the federally approved 

regulations and source-specific permits 

submitted by each State agency. 

EPA generally updates these SIP 

Compilations on an annual basis. Under 

the revised procedures, EPA must 

periodically publish an informational 

document in the rules section of the 

Federal Register notifying the public 

that updates have been made to a SIP 

Compilation for a particular State. EPA 

began applying the 1997 revised 

procedures to Georgia on May 21, 1999, 

see 64 FR 27699, and is providing this 

notification in accordance with such 

procedures. 

II. EPA Action 

In this action, EPA is providing notice 

of an update to the materials 

incorporated by reference into the 

Georgia SIP as of September 1, 2024, 

and identified in 40 CFR 52.570(c). This 

update includes SIP materials submitted 

by Georgia and approved by EPA since 

the last IBR update. See 88 FR 16564 

(March 20, 2023). In addition, EPA is 

providing notice of the following 

corrections to 40 CFR 52.570(c): 

Changes Applicable to Paragraph (c), 

Table (1), EPA-Approved Georgia 

Regulations 

A. Under 391–3–1–.02(7), ‘‘Prevention 

of Significant Deterioration of Air 

Quality (PSD),’’ the explanation column 

is reformatted to combine the two 

existing paragraphs into one cell. 

B. Under 391–3–1–.01, ‘‘Definitions,’’ 

the explanation column is revised to 

add the text ‘‘which were’’ before the 

text ‘‘approved on 12/4/2018’’ and 

before the text ‘‘approved on 2/2/1996,’’ 


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