Document ID: s3://data.kl3m.ai/documents/govinfo/USCOURTS/USCOURTS-caDC-22-01302/USCOURTS-caDC-22-01302-0/pdf.json

Parties Involved:
American Forest & Paper Association
Petitioner
American Wood Council
Petitioner
Council of Industrial Boiler Owners
Petitioner
Environmental Protection Agency
Respondent

Document Text:

United States Court of Appeals

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued March 21, 2024 Decided September 3, 2024

No. 22-1271

UNITED STATES SUGAR CORPORATION,

PETITIONER

v.

ENVIRONMENTAL PROTECTION AGENCY,

RESPONDENT

SIERRA CLUB,

INTERVENOR

Consolidated with 22-1302, 22-1303

On Petitions for Review of a Final Administrative

Action of the Environmental Protection Agency

Timothy S. Bishop argued the cause for Industry 

Petitioners. With him on the briefs were Shannon S. Broome

and Charles H. Knauss. Avi Kupfer entered an appearance. 

James S. Pew argued the cause and filed the briefs for 

Environmental Petitioners.

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Perry M. Rosen, Attorney, U.S. Department of Justice, 

argued the cause for respondent. With him on the brief were 

Todd Kim, Assistant Attorney General, and Lucas May, 

Attorney, U.S. Environmental Protection Agency. 

James S. Pew argued the cause and filed the brief for 

respondent-intervenor Sierra Club.

Charles H. Knauss, Shannon S. Broome, Elliott Zenick, 

Kevin M. Dempsey, and Lisa M. Jaeger were on the brief for 

intervenor-respondents American Forest and Paper 

Association, et al. 

Before: WILKINS, KATSAS, and WALKER, Circuit Judges.

Opinion for the Court filed PER CURIAM.

The Clean Air Act directs the Environmental Protection 

Agency to establish emission standards for new and existing 

sources of hazardous air pollutants. See 42 U.S.C. §§ 7401, 

7412; Michigan v. EPA, 576 U.S. 743, 747 (2015). 

The Act says a source is “new” if it is built after EPA 

proposes an applicable emission standard for that source. 42 

U.S.C. § 7412(a)(4). A source is “existing” if it is built before 

then. Id. § 7412(a)(10). This distinction matters because the 

required standards for new sources are generally stricter than 

the required standards for existing sources. See id. 

§ 7412(d)(3). 

In a 2022 rule, EPA classified some industrial boilers as 

“new” sources of hazardous air pollutants even though they 

were built before the applicable emission standards were 

proposed in 2020. See National Emission Standards for 

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Hazardous Air Pollutants for Major Sources: Industrial, 

Commercial, and Institutional Boilers and Process Heaters, 87 

Fed. Reg. 60816, 60830, 60841 (Oct. 6, 2022). Because that 

classification conflicts with the Clean Air Act’s definitions of 

“new” and “existing” sources, we grant the petitions brought 

by the U.S. Sugar Corporation and trade groups representing 

other operators of industrial boilers. 

In the same 2022 rule, EPA drew its data from the same

2013-era dataset it had used for other, still-valid emission 

standards promulgated for industrial boilers back in 2013. See 

87 Fed. Reg. at 60820–21. It intentionally excluded more 

recent data because it wanted to regulate similar sources 

similarly, so these new 2022 standards would be consistent 

with the still-valid 2013 standards. Id. Because that decision 

did not violate the Clean Air Act, we deny the petition brought 

by four environmental organizations. 

I

Boilers burn materials like coal, paper, and agricultural 

waste to create heat, electricity, and other forms of energy. 

U.S. Sugar Corp. v. EPA, 830 F.3d 579, 592, 597 (D.C. Cir. 

2016) (per curiam) (“U.S. Sugar Corp. I”). In doing so, they 

emit hazardous air pollutants like mercury, carbon monoxide, 

hydrogen chloride, and particulate matter. Those hazardous air 

pollutants can cause adverse health effects. Id. 

The emission of hazardous air pollutants by boilers is 

regulated by EPA at the direction of the Clean Air Act. See 

generally 42 U.S.C. § 7412. 

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A 

Section 112 of the Clean Air Act requires EPA to create 

technology-based emission standards for stationary sources of 

hazardous air pollutants. See generally id. Because these 

standards generally require sources to be at least as clean as 

their peers—and so must often use technology that is the same 

as, or better than, the technology of comparable sources—these 

emission limits are called the “maximum achievable control 

technology” or “MACT.” See U.S. Sugar Corp. I, 830 F.3d at 

594 (cleaned up). See also id. (Congress wanted sources to 

pollute no worse than “their best performing peers”) (cleaned 

up). 

To set MACT standards, “EPA’s first task is to create ...

categories and subcategories” of sources. Id. at 593. Once 

EPA has created those categories and subcategories, the Clean 

Air Act requires that it draw “one final dividing line—between 

‘new’ sources and ‘existing’ sources.” Id. at 594 (citing 42 

U.S.C. § 7412(d)(3)). A “new” source is “a stationary source 

the construction or reconstruction of which is commenced after 

the Administrator first proposes regulations under this section 

establishing an emission standard applicable to such source.” 

42 U.S.C. § 7412(a)(4). An “existing” source is “any 

stationary source other than a new source.” Id. § 7412(a)(10).1

1 The Clean Air Act also separates boilers based on the amount 

of hazardous air pollutants they emit. A boiler is a “major” boiler if 

it annually emits (a) more than 10 tons of any single hazardous air 

pollutant, or (b) more than 25 tons of any combination of hazardous 

pollutants. 42 U.S.C. § 7412(a)(1). If a boiler does neither, it is an 

“area” boiler. Id. at § 7412(a)(2). This case concerns only major 

boilers. 

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Once EPA has identified categories and subcategories and 

drawn the necessary distinctions between new and existing 

sources, EPA must set emission standards applicable to each 

category and subcategory. See id. § 7412(c)(2), (d)(3). A 

“new” source in a given category or subcategory must meet a 

standard at least as strict as “the emission control that is 

achieved in practice by the best controlled similar source.” Id.

§ 7412(d)(3). For an “existing” source in a given category or 

subcategory, the MACT standard must be at least as stringent 

as “the average emission limitation achieved by the best 

performing 12 percent of the existing sources (for which the 

Administrator has emissions information).” Id.

§ 7412(d)(3)(A).2

 Though this statutory text is somewhat 

technical, it means at least this—the standard for a “new” 

source is stricter than the standard for an “existing” source. 

In addition, new and existing sources have different 

deadlines for compliance. See id. § 7412(i). An existing 

source has three years to comply with a stricter new standard 

for existing sources. See id. § 7412(i)(3). In contrast, a new 

source must immediately comply with a stricter new standard 

for new sources, unless EPA promulgates the standard while 

the new source is under construction and the promulgated 

standard is more onerous than the proposed one. See id.

§ 7412(i)(1), (2). In that case, the new source has three years 

to comply. See id. § 7412(i)(2). 

2 Or, if the subcategory is so small that it has fewer than thirty 

sources, the standard for existing sources must be at least as stringent 

as “the average emission limitation achieved by the best performing 

5 sources (for which the Administrator has or could reasonably 

obtain emissions information).” Id. § 7412(d)(3)(B).

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B

EPA promulgated MACT emission standards for boilers 

in 2004. See 69 Fed. Reg. 55218 (Sept. 13, 2004). But for 

reasons that are not relevant to today’s case, this Court vacated 

EPA’s rule. See NRDC v. EPA, 489 F.3d 1250, 1257, 1261 

(D.C. Cir. 2007). 

In 2010, EPA tried again. It proposed new standards for 

boilers, based on data drawn from a new dataset. Then, in 

2011, it promulgated a final rule. See 76 Fed. Reg. 15608 (Mar. 

21, 2011). This rule, as amended on reconsideration in 

subsequent years, resulted in 202 emission standards for new 

and existing major boilers. 

Industry and environmental groups challenged the new 

standards on a variety of grounds. See U.S. Sugar Corp. I, 830 

F.3d at 591. Most of those challenges failed. See id. at 667. 

But, as relevant here, one succeeded—we held that when EPA 

based new standards on the practices and technologies of 

existing boilers, EPA had sometimes excluded certain boilers 

in violation of the law. See id. at 631–32. That mistake did not 

affect most of the 202 standards, but it did render 34 of the 

standards invalid. 

In U.S. Sugar Corp. I, the Court vacated the invalid 

standards. See id. at 667. But on rehearing, we reconsidered 

that remedy and instead remanded without vacatur, thus 

allowing the invalid standards from the 2011 Rule to remain in 

place while EPA “revise[d]” the invalid standards “consistent 

with ... [the] opinion in [that] case.” U.S. Sugar Corp. v. EPA, 

844 F.3d 268, 270 (D.C. Cir. 2016) (per curiam) (“U.S. Sugar 

Corp. II”). We “expect[ed] the EPA to complete this 

rulemaking promptly.” Id.

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C

In response to U.S. Sugar Corp. I and U.S. Sugar Corp. II, 

EPA proposed a new rule on August 24, 2020, and promulgated 

it as a final rule in 2022. See 87 Fed. Reg. at 60819–21. The 

rule replaced the 34 invalid MACT standards. See id. at 60817. 

It included two decisions that today’s petitioners challenge.3

 

First, the Industry Petitioners. Leading a group of industry 

trade groups, the U.S. Sugar Corporation challenges the 2022 

Rule’s definition of “new” boilers. In the 2022 Rule, EPA 

classified boilers built after June 4, 2010 as “new” boilers—

even if the applicable standards for those boilers were not 

proposed until 2020.4 Id. at 60830. 

One such boiler is Boiler No. 9 at a sugar facility owned 

by the U.S. Sugar Corporation and located in Clewiston, 

Florida. By burning bagasse—the pulp that remains after juice 

is extracted from sugarcane—this boiler creates steam and heat 

to help power the facility. 

The U.S. Sugar Corporation began building Boiler No. 9 

in 2016 at a cost of $65 million to replace three older and 

higher-polluting boilers. Upon its completion in 2019, it 

complied with the strictest standards in effect at the time—the 

3 There is an additional argument raised by the Industry 

Petitioners regarding the new-source MACT standard for Hydrogen 

Chloride. But we decline to address that argument because it is not 

necessary to our resolution of the petitions. See infra Section II. 

4 The Industry Petitioners have standing because the challenged 

rule imposes direct costs on their businesses. See Chamber of Com. 

of U.S. v. EPA, 642 F.3d 192, 199–200 (D.C. Cir. 2011).

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standards for “new” boilers that were enacted by EPA in 2011. 

The Industry Petitioners say that because Boiler No. 9 was 

constructed “with state-of-the-art control technology,” it is “the 

best-controlled bagasse-fueled boiler in the country.” Industry 

Petitioners Br. at 10. 

When EPA proposed 34 revised standards in 2020, Boiler 

No. 9 already surpassed the revised standards for “existing” 

boilers. 

But EPA’s redefinition of “new” boilers treats Boiler No. 

9 as a “new” boiler, subject to the standards for “new” boilers 

proposed in 2020—even though construction on Boiler No. 9 

began and ended before 2020. Under this regime—whose 

logic suggests that boilers built after June 4, 2010 are forever 

“new”—the U.S. Sugar Corporation must spend tens of 

millions of dollars retrofitting Boiler No. 9.5

 

Second, the Environmental Petitioners. When EPA 

calculated the 34 new MACT standards proposed in 2020, EPA 

decided not to use additional data it had collected after 2013. 

See 87 Fed. Reg. at 60820–22. Instead, it relied on data from 

the 2013-era dataset, which still serves as the basis for the 168

standards that were left undisturbed by U.S. Sugar Corp. I and 

U.S. Sugar Corp. II. See id. EPA believed this approach would 

treat similar sources similarly and ensure consistency across all 

202 standards, regardless of when the standards were proposed. 

5 The other Industry Petitioners—the American Forest & Paper 

Association, the American Wood Council, and the Council of 

Industrial Boiler Owners—represent members who also built boilers 

between 2010 and 2020. These boilers also already satisfy the 

revised standards if they are treated as “existing” boilers, but will 

also require expensive retrofitting if treated as “new” boilers. 

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See id. According to EPA, that approach avoided a “potentially 

inequitable outcome,” conserved agency resources, and 

demonstrated fidelity to the “limited nature” of this Court’s 

remand in U.S. Sugar Corp. II. Id. at 60822. 

EPA’s exclusion of post-2013 data made some of the 34 

new standards less strict than they might have otherwise been 

had EPA been relying on data from 2020. In its petition for 

review, a group of environmentalists says the exclusion of this 

newer data both “contravenes the statute” and was “arbitrary 

and capricious.”6

 Environmentalists Br. at 16–17.

* * *

In 2023, the U.S. Sugar Corporation filed a motion to stay 

enforcement of the 2022 Rule with regard to Boiler No. 9. A 

special panel of this Court granted the motion because it 

“satisfied the stringent requirements for a stay pending court 

review,” see Order, U.S. Sugar Corp. v. EPA, No. 22-1271, at 

*1–2 (March 10, 2023), including “a strong showing that” the 

U.S. Sugar Corporation was “likely to succeed on the merits,” 

Nken v. Holder, 556 U.S. 418, 434 (2009). 

For the reasons explained below, we now grant the 

Industry Petitioners’ petitions and deny the Environmental 

Petitioners’ petition. 

6 The Environmental Petitioners are the California 

Communities Against Toxics, the Coalition For A Safe 

Environment, the Sierra Club, and the Utah Physicians for a Healthy 

Environment. Under Supreme Court precedent, these groups have 

standing because the challenged rule exposes their members to 

higher levels of pollution than their interpretation of the Clean Air 

Act allows. See Friends of the Earth v. Laidlaw Env’t. Servs., 528 

U.S. 167, 180–83 (2000).

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II

The Industry Petitioners present an issue of statutory 

interpretation that we review de novo. See Loper Bright Enters. 

v. Raimondo, 144 S. Ct. 2244, 2261 & n.4, 2273 (2024). 

Instead of deferring to EPA’s interpretation of the Clean Air 

Act, we must apply what we regard as the statute’s “best” 

reading. See id. at 2266.

7

A

Before interpreting the statute, however, we begin with

EPA’s argument that the Industry Petitioners’ challenge to its

interpretation of the new-source definition is untimely. In 

2011, EPA adopted regulations defining a “new source” in the 

boiler context as ones built after June 4, 2010. According to 

EPA, that was the time for challenging its view of which boilers 

are “new.”

EPA is mistaken. Regardless of whether the Industry 

Petitioners could and should have challenged the 2011 

regulation, the “reopening” doctrine applies here and allows us 

to hear their current challenge. See Pub. Emps. for Env’t Resp. 

v. EPA, 77 F.4th 899, 911 (D.C. Cir. 2023). That doctrine 

provides that when an agency explicitly or implicitly revisits a 

7

 Loper Bright held that the Administrative Procedure Act 

requires courts to construe statutes de novo, without deference to the 

views of agencies entrusted to administer the statutes. See 144 S. Ct. 

at 2261 & n.4. That analysis controls EPA interpretations of the 

Clean Air Act reviewed under its judicial-review provision, 42 

U.S.C. § 7607(d)(9), because judicial review under the Clean Air Act 

is “essentially the same” as judicial review under the APA, see Ethyl 

Corp. v. EPA, 51 F.3d 1053, 1064 (D.C. Cir. 1995).

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prior position, “its renewed adherence is substantively 

reviewable.” Id. (cleaned up). In applying the doctrine, we 

examine the “entire context” of the rulemaking, including 

“relevant proposals and reactions of the agency,” to determine

whether the agency undertook a “serious, substantive 

reconsideration” of an existing rule. Growth Energy v. EPA, 5 

F.4th 1, 21 (D.C. Cir. 2021) (per curiam) (cleaned up). 

Here, EPA clearly took a serious look at what date to use 

when classifying boilers as “new” or “existing.” It spent over 

a full page in the Federal Register defending its decision to 

retain the June 4, 2010 cutoff date. See 87 Fed. Reg. at 60830–

31. EPA first explained its view that the Clean Air Act and 

existing regulations permitted use of that date in this 

rulemaking. Id. at 60830. Then, EPA detailed its policy 

rationale for using that date, including the fact that the emission 

standards here were based on the same dataset as those used to 

support the 2011 regulation. Id. at 60830–31. The dataset 

justification was not (and could not have been) given when 

EPA promulgated the 2011 regulation, and its choice to provide 

a new rationale for the old date confirms its serious 

reconsideration of the question. Given that reconsideration, the 

Industry Petitioners’ challenge can go forward.

8

8

 EPA further contends that the Industry Petitioners waived 

their argument by not citing 40 C.F.R. § 63.7490(b), which sets forth 

the June 4, 2010 cutoff date for classifying boilers as new or existing. 

But the entire thrust of their argument was that EPA had to update its 

definition of what counts as a “new source.” Indeed, the Industry 

Petitioners’ first argument heading asserts that “the 2022 rule 

unlawfully applies revised new source standards to boilers that 

commenced construction before the rule was first proposed in 2020.” 

Industry Pet. Br. at 19 (cleaned up). The Industry Petitioners were 

clearly arguing that the existing cutoff date was no longer valid, so

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B

On the merits, the question presented by the Industry 

Petitioners is whether Section 112 of the Clean Air Act allowed

EPA, in promulgating the 2022 emission standards for boilers, 

to categorize all boilers constructed after June 4, 2010 as new 

sources of pollution. Recall that the minimum emission 

standard for “new” boilers “shall not be less stringent than the 

emission control that is achieved in practice by the best 

controlled similar source.” 42 U.S.C. § 7412(d)(3). In simple 

terms, all “new” boilers must meet an exacting standard pegged 

to the cleanest similar model on the market. On the other hand, 

“existing” boilers need only meet the “average emission 

limitation achieved by the best performing 12 percent of the 

existing sources.” Id. § 7412(d)(3)(A). In sum, new boilers 

must satisfy more stringent emissions requirements than 

existing ones.

Section 112 defines a “new source” as “a stationary source

the construction or reconstruction of which is commenced after 

the Administrator first proposes regulations under this section 

establishing an emission standard applicable to such source.” 

Id. § 7412(a)(4). EPA concluded that the “regulations” under 

Section 112 “establishing an emission standard” were “first 

propose[d]” in the 2011 rulemaking, id., so any boiler 

constructed after June 4, 2010 meets the definition of a “new 

source,” 87 Fed. Reg. at 60830; EPA Br. at 25. The Industry 

Petitioners counter that “an emission standard” is “first 

propose[d]” when EPA first proposes each consecutive 

standard, not when EPA first proposes any emission standard 

EPA cannot claim any unfair “surprise.” See NRDC v. EPA, 25 F.3d 

1063, 1071–72 n.4 (D.C. Cir. 1994).

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for entire categories of sources. 42 U.S.C. § 7412(a)(4); 

Industry Pet. Br. at 19–20. On this view, the proper date to 

determine whether a boiler is “new” is August 24, 2020, when 

this rulemaking proposed new emission standards for boilers.

Despite their differences, the parties agree on one key 

point: Each thinks that the other’s reading of the statute is 

semantically plausible. As EPA explained, the new-source 

definition “could refer to ... the first time the agency proposes 

any standards for the source category ... or the first time the 

Agency proposes a particular standard.” EPA Br. at 29

(cleaned up). The agency had good reason to admit as much 

because it repeatedly has adopted the Industry Petitioners’ 

proposed interpretation in setting Section 112 emission 

standards for sources other than boilers. See, e.g., National 

Emission Standards for Coke Oven Batteries, 70 Fed. Reg. 

19992, 20009–10 (Apr. 15, 2005) (defining “new sources” as 

“those constructed after the date of proposal” of regulatory

“amendments”); National Emission Standards for Hazardous 

Air Pollutants: Carbon Black Production and Cyanide 

Chemicals Manufacturing Residual Risk and Technology 

Reviews, and Carbon Black Production Area Source 

Technology Review, 86 Fed. Reg. 66096, 66102–03 (Nov. 19, 

2021) (similar).

We agree that the phrase “after the Administrator first 

proposes ... an emission standard,” read in a vacuum, can be 

interpreted either way. This provision is indeterminant because 

it uses the indefinite article “an,” which refers to a standard that 

is “unidentified or not immediately identifiable.” See 

Indefinite, Webster’s Third New International Dictionary: 

Unabridged 1147 (1993). As the Supreme Court just 

reiterated, Congress’s choice between a definite and indefinite 

article matters when determining statutory meaning. See 

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Corner Post, Inc. v. Bd. of Governors of Fed. Res. Sys., 144

S. Ct. 2440, 2455 (2024).

It is true, as EPA points out, that the standard must be the 

one “first propose[d],” but that requirement does not tell us 

whether the provision means “first propose[d]” for the original 

emission standard or for the updated one. 42 U.S.C. 

§ 7412(a)(4). Given this semantic ambiguity, we turn to “the 

remainder of the statutory scheme” to determine who has the

better reading of the new-source definition. United Sav. Ass’n 

of Tex. v. Timbers of Inwood Forest Assocs., 484 U.S. 365, 371 

(1988); see also Pulsifer v. United States, 144 S. Ct. 718, 731–

35 (2024).

C

Statutory structure and context persuade us that the 

Industry Petitioners’ interpretation is correct. When Section 

112 references the date “an emission standard” is “first 

propose[d],” it means the first proposal of each consecutive 

standard. 42 U.S.C. § 7412(a)(4). This reading allows all parts 

of Section 112 to function as a “harmonious whole,” Roberts v. 

Sea-Land Servs., Inc., 566 U.S. 93, 100 (2012) (cleaned up), 

whereas EPA’s contrary reading does not. 

Start with how the definition of “new source” works with 

other provisions of Section 112. Subsection (i) establishes 

compliance deadlines that make sense only on the Industry 

Petitioners’ proposed reading. It requires all new sources to 

comply with emission standards immediately upon their

“effective date,” 42 U.S.C. § 7412(i)(3)(A), which is the date 

when the standard is “promulgat[ed],” id. § 7412(d)(10). In 

contrast, existing sources have up to three years to comply with 

their lower emission standards. Id. § 7412(i)(3)(A). As EPA 

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explained in a different Section 112 rulemaking, “new sources 

know from the beginning of the construction effort what

[emission] controls will be required, and do not have to incur 

the higher costs and the time-consuming disruptions normally 

associated with control retrofits.” National Emission 

Standards for Hazardous Air Pollutants from the Portland 

Cement Manufacturing Industry, 71 Fed. Reg. 76518, 76541 & 

n.16 (Dec. 20, 2006) (Portland Cement Rule).

If the proper date to determine whether a source is “new” 

is when EPA first proposed the specific “emission standards” 

under review, the statute’s pieces work in harmony. Sources 

built before the amended standards were first proposed must 

meet less-stringent standards tied to the emissions from other 

already-operating sources, and they have some time to retrofit 

their boilers. 42 U.S.C. § 7412(d)(3)(A), (i)(3)(A). This makes 

sense because it is more difficult to retrofit old boilers to meet 

modern, state-of-the-art standards than it is to construct new 

boilers to meet those standards from the beginning. See 

Portland Cement Rule, 71 Fed. Reg. at 76541 & n.16. EPA 

itself has explained that retrofitting older sources to comply 

with increasingly stringent modern standards may be 

“draconian” if not “impossible.” Id. And we should not lightly 

assume that a statute is “draconian,” Snyder v. United States, 

144 S. Ct. 1947, 1957 (2024), or “demands the impossible,” 

Anniston Mfg. Co. v. Davis, 301 U.S. 337, 350–52 (1937).

A special statutory compliance rule confirms that alreadyconstructed boilers need not meet the new-source standards. 

Under the special rule, if construction of a source begins after

an emission standard is proposed but before it is finalized, and 

if the final rule requires a “more stringent” standard than the 

proposed one, a new source need not comply with the final rule

“until the date 3 years after the date of promulgation.” 42 

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U.S.C. § 7412(i)(2). In essence, if a company starts building a 

source in reliance on a proposed standard and then EPA makes 

the actual standard stricter, the company gets a grace period to 

retrofit the source, just like existing sources get. Id.

EPA’s interpretation of the new-source definition would 

render the “special rule” almost nonsensical. Companies that 

build emission sources right after a new standard has been

proposed would be entitled to a grace period to retrofit their 

sources if the final standard turns out to be stricter than the 

proposed one, but companies that built sources much earlier

would be required to comply immediately with the updated 

standard. EPA does not explain why a statute that takes pains 

to give regulated parties enough time to meet changing 

emission standards would create this type of inconsistency.

The rule under review attempts to make up for the 

harshness of treating decade-old boilers as “new source[s]” by 

granting them a three-year grace period to comply with the 

new-source emission standards. See 87 Fed. Reg. at 60832. 

But Section 112(d) states that “[e]mission standards or other 

regulations promulgated under this subsection shall be 

effective upon promulgation.” 42 U.S.C. § 7412(d)(10). 

Section 112(i) prohibits any person from operating a “new” 

emissions source “in violation of” an emission standard after 

its “effective date.” Id. § 7412(i)(3)(A). And it further permits 

EPA to establish a delayed “compliance date” for any existingsource emission standard, which may fall up to “3 years after 

the effective date of such standard.” Id. In sum, “new” sources 

must comply with emission standards immediately, but 

“existing” sources may be afforded a three-year grace period to 

bring themselves into compliance. In other words, EPA 

adopted a sweepingly broad understanding of what counts 

definitionally as a “new” source, then proceeded to treat the 

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sources at issue here similar to “existing” ones for purposes of 

delayed compliance dates. This need to mix-and-match in 

addressing different parts of the statute castsfurther doubt upon 

EPA’s broad interpretation of the definition itself. See Util. Air 

Regul. Grp. v. EPA, 573 U.S. 302, 319–20 (2014).

Classifying boilers constructed after June 4, 2010 as 

eternally “new” also does not accord with the Clean Air Act’s

iterative process for regulating pollution sources. Section 112

requires EPA to reevaluate existing emission standards—and 

promulgate new ones if facts on the ground have changed—

every eight years, as technology allows for cleaner-burning 

sources. 42 U.S.C. § 7412(d)(6); see Nat’l Ass’n for Surface 

Finishing v. EPA, 795 F.3d 1, 4 (D.C. Cir. 2015). Yet EPA’s 

interpretation of “new source” would short-circuit this process 

by locking in which sources are “new” for all time, rather than 

having the definition apply to each discrete rulemaking. For 

example, in the year 2034, a boiler constructed in 2011 would

be considered “new” and would have to comply with standards 

for the “best controlled” 2034 model. 42 U.S.C. § 7412(d)(3). 

Needless to say, a two-decade-old boiler is not “new” within 

any normal understanding of that term, and “it is not unusual 

to consider the ordinary meaning of a defined term” when 

interpreting an ambiguity in a definition. Bond v. United 

States, 572 U.S. 844, 861 (2014).

Finally, EPA’s interpretation of the “new source” 

definition is internally inconsistent. Under that interpretation, 

the proper time to determine whether a boiler is “new” should 

have been 2003, not 2010, because that was when EPA first 

proposed emission standards for boilers. See NRDC, 489 F.3d 

at 1261. EPA resiststhis conclusion because this Court vacated 

the 2003 standards. See id. at 1262. But Section 112 references 

the time when standards are “first propose[d],” and the fact that 

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a final, promulgated standard was later vacated does not 

change that date. 42 U.S.C. § 7412(a)(4). EPA’s own logic 

thus would require setting the date in 2003, which even EPA 

consistently has refused to do.

D

We are unmoved by EPA’s incantation that “first

proposed” means “first proposed.” As we have explained, the 

statutory reference to “an emission standard” (emphasis added) 

does not answer the question which emission standard—

original or amended—the definition is referring to. And in 

context, “first” references the first time EPA proposes each 

emission standard for the source at issue. Id. Each regulation 

“establish[es]” a new “emission standard applicable to such 

source,” so “an emission standard” refers to each of the 

increasingly stringent standards that EPA must propose over 

time. See id.

Under this interpretation, the word “first” still plays a

significant role in the statutory scheme. For example, if EPA 

proposes an emission standard and then decides, in response to 

comments, to revise the proposal and reopen the comment 

period, the date demarcating “new” and “existing” sources 

would still be the date the rule was first proposed, not the date 

of the re-proposal. Id. This is no fanciful possibility, as EPA 

sometimes “reproposes” regulations after an original proposal 

generates significant criticism. Ethyl Corp. v. EPA, 541 F.2d 

1, 49 (D.C. Cir. 1976) (en banc). In that circumstance, any reproposal containing the same standard—despite generating a 

new comment period and delaying the promulgation of a final 

standard—would not push back the date on which the standard 

was “first proposed.” In contrast, if the definition of “new 

source” omitted the word “first,” as it did before the 1990 

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amendments, then the date of the most-recent proposal would 

likely control the distinction between new and existing sources.

EPA invokes the definition of “new source” in Section 111

of the Clean Air Act, which is keyed to when regulations 

“prescribing a standard of performance under this section” 

were “proposed.” 42 U.S.C. § 7411(a)(2). Invoking the 

meaningful-variation canon, see, e.g., Southwest Airlines Co. 

v. Saxon, 596 U.S. 450, 457–58 (2022), EPA contends that 

“proposed” under Section 111 cannot mean the same thing as 

“first proposed” under Section 112. Fair enough, at least if we 

assume that the respective definitions are similar enough to 

trigger application of the canon. But as shown in the example 

above, the Industry Petitioners’ interpretation of Section 112

does not collapse “first proposed” into “proposed,” so neither 

the meaningful-variation canon, nor the related consideration 

of avoiding surplusage, cut in favor of EPA here.

E

EPA offers an alternative justification for labeling as 

“new” boilers constructed over a decade ago. According to 

EPA, because the standards under review here rely on the same 

dataset as did the 2013 standards, the date to determine whether 

boilers are “new” or “existing” should still be June 4, 2010.

Section 112 provides no support for the proposition that 

the vintage of the dataset is relevant to determining whether a 

source is “new” or “existing.” Under that provision, the critical 

date turns on when an “emission standard” is “first 

propose[d]”—not when supporting data for the standard was 

generated. 42 U.S.C. § 7412(a)(4). EPA points to no textual 

source for its argument. Nor is it clear how EPA could do so. 

An “emission standard” is a “requirement” placed on sources

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to “limit[] the[ir] quantity, rate, or concentration of emissions 

of air pollutants.” Id. § 7602(k). A dataset used to calculate 

the standard is not a standard itself. Under Section 112, when 

the dataset was compiled simply has no bearing on when the 

emission standard was “first propose[d].” Id. § 7412(a)(4).

Congress’s choice not to tie the definitions of “new” and 

“existing” sources to the underlying dataset makes sense given

the extent of EPA’s discretion to fashion standards out of 

underlying data. In particular, EPA could drastically increase 

the stringency of a standard based on the same underlying data. 

This case proves the point: Although EPA used the same data 

here as in the 2013 reconsideration, the HCl emission standard 

became 100 times more stringent based on EPA’s choice to 

designate a different boiler as the best-performing source. 87 

Fed. Reg. at 60823.

* * *

Despite the semantic possibility that “after the 

Administrator first proposes ... an emission standard” 

references when the original emission standard was first

proposed, we conclude that this clause refers to when each 

sequential emission standard was first proposed. The structure 

of the Clean Air Act makes clear that boilers constructed before 

each individual standard was first proposed are “existing,” and 

boilers constructed after each individual standard was first

proposed are “new.” We therefore set aside EPA’s 2022 Rule 

to the extent that it defines sources constructed or reconstructed 

before August 24, 2020—that is, the date the 2022 Rule was 

proposed by EPA—as “new source[s].”9

9

 The Industry Petitioners also ask us to rule that EPA arbitrarily 

set the HCl limit for new sources. Once their boilers are properly 

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III

We turn next to the Environmental Petitioners’ challenges 

to the 2022 Rule. Under the Clean Air Act, this Court “may 

reverse” the EPA’s 2022 Rule if it is “in excess of statutory 

jurisdiction, authority, or limitations,” or “arbitrary, capricious, 

an abuse of discretion, or otherwise not in accordance with 

law.” 42 U.S.C. § 7607(d)(9). To determine “whether an 

agency has acted within its statutory authority,” we use “the 

traditional tools of statutory construction.” Loper Bright 

Enters., 144 S. Ct. at 2268, 2273. 

As we have explained, when EPA recalculated the 

emission standards in the 2022 Rule in response to this Court’s 

remand, EPA chose to rely upon the same dataset that it had 

used to calculate the emission standards in the 2013 Rule. The 

Environmental Petitioners contend that EPA’s choice to use 

that original dataset, rather than updated data EPA had in its 

possession, was contrary to law. The Environmental 

Petitioners also argue that even if EPA’s decision not to use 

updated data was not unlawful, it was arbitrary and capricious. 

We disagree. We hold that EPA’s decision to rely upon 

the same dataset it used to calculate the emission standards in 

the 2011 and 2013 Rules was neither unlawful nor arbitrary or 

capricious. We accordingly deny the Environmental 

Petitioners’ petition for review.

classified, however, they will no longer be subjected to the newsource HCl limit. Therefore, we decline to reach that issue.

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A

The Environmental Petitioners contend that EPA’s 

decision to rely on the original dataset was unlawful because, 

under Environmental Petitioners’ reading of Section 112(d), 

Section 112 requires EPA to use any available data it has in 

making floor calculations. The Environmental Petitioners rely 

on two portions of the statutory text in support of their 

argument that EPA’s decision to rely on its original dataset 

violated Section 112(d). First, Section 112(d)(3)(A) provides 

that emission standards for existing sources cannot be less 

stringent than “the average emission limitation achieved by the 

best performing 12 percent of the existing sources (for which 

the Administrator has emissions information).” 42 U.S.C. 

§ 7412(3)(A) (emphasis added). Second, and similarly, 

Section 112(d)(3)(B) provides that emission standards for 

existing source subcategories with fewer than thirty sources 

cannot be less stringent than “the average emission limitation 

achieved by the best performing 5 sources (for which the 

Administrator has or could reasonably obtain emissions 

information).” Id. § 7412(d)(3)(B) (emphasis added). The 

Environmental Petitioners argue that Section 112(d)(3)’s 

references to the information the Administrator has in its 

possession or could reasonably obtain, see id. § 7412(d)(3)(A), 

(B), requires EPA to use whatever information it possesses 

when calculating emission standards. EPA is not, in other 

words, “free to exclude from its floor calculations emissions 

information that it has in its possession.” Environmental Pet.

Br. 25. The Environmental Petitioners explain that Section 

112’s statement that existing source standards must be based 

on the sources “for which the Administrator has emissions 

information” effectively identifies the group of sources EPA 

must consider when setting a standard for a given source 

category or subcategory. So, when EPA “has” information for 

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a given source in a category, Section 112 requires it to consider 

the available information for that source when setting the 

relevant category’s emission standards. 

The Environmental Petitioners thus argue that EPA ran 

afoul of Section 112 by choosing to ignore the post-2013 

emissions data in its possession when it promulgated the 

standards in the 2022 Rule. Because EPA chose not to use that 

post-2013 emissions data in calculating emission standards, the 

Environmental Petitioners contend that its standards do not 

reflect the “average emission limitation achieved by the best 

performing 12 percent of the existing sources (for which the 

Administrator has emissions information).” 42 U.S.C. 

§ 7412(d)(3)(A); see also id. § 7412(d)(3)(B).

EPA responds that the Environmental Petitioners have 

misunderstood the statutory text. Section 112’s language that 

emission standards must be based on the performance of the 

sources “for which the Administrator has emissions 

information” does not require EPA to take into account all 

information that it literally “has” in its possession. Rather, the 

statutory language’s location in a parenthetical clause shows 

that EPA has no obligation to “obtain emission data from 100 

percent of the source category or subcategory in order to 

identify the best performing 12 percent” of sources. 87 Fed. 

Reg. at 60821; see Becerra v. Empire Health Found., 597 U.S. 

424, 440 (2022) (“[A] parenthetical is typically used to convey 

an aside or afterthought.”) (cleaned up). In effect, then, the 

statutory language does not constrain EPA—to the contrary, it 

allows EPA to “prevent delay” in promulgating emission 

standards by moving forward with the emission standardsetting process, even where it does not have emissions data 

from every single source in a category. 87 Fed. Reg. at 60821.

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Whether and to what extent Section 112(d)(3) imposes 

restrictions on what data EPA must use when calculating 

emissions floors is a tricky question, but we think the 

Environmental Petitioners’ suggested answer to that question 

cannot possibly be correct. As we have explained, under the 

Environmental Petitioners’ expansive interpretation of the 

statutory text, whenever EPA “has” emissions information for 

a source, see 42 U.S.C. § 7412(d)(3)(A), (B) (or can reasonably 

obtain emissions information, see id. § 7412(d)(3)(B)), it must 

use that information in its calculations. Reading the statutory 

text this way gives rise to a natural question: At what point in 

the rulemaking process must EPA ensure that it has used the 

data it “has” in its possession? At oral argument, counsel for 

the Environmental Petitioners clarified that, in Environmental 

Petitioners’ view, EPA must use the data it “has” in its 

possession up until the promulgation of the final rule. Oral 

Argument Tr. at 47; see also Oral Argument Tr. at 48–50. 

Reading Section 112(d)(3) to require EPA to use the data 

it “has” in its possession until the moment a rule is promulgated 

would frustrate the statutory purposes of the Clean Air Act. See

42 U.S.C. § 7401(b) (noting that the purpose of the Clean Air 

Act is, among other things, to “protect and enhance the quality 

of the Nation’s air resources”). Calculating emission standards 

that satisfy the Section 112(d) statutory criteria is a 

complicated process: EPA must gather and analyze data for 

boilers in each given category and then arrive at an emissions 

floor for each category that has “maximum stringency” but is 

also “continuously achievable.” U.S. Sugar Corp. I, 830 F.3d 

at 632; see also, e.g., id. (promulgating emission standards that 

satisfy “the statutory criteria is no easy task”); Nat’l Ass’n of 

Clean Water Agencies v. EPA, 734 F.3d 1115, 1132–33 (D.C. 

Cir. 2013) (“[E]stablishing MACT floors is no simple task.”). 

Under the Environmental Petitioners’ interpretation, that 

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complicated process would seemingly have no end. Consider, 

for example, what would happen if, following years of 

calculations to establish emissions floors, EPA were to receive 

new emissions information from a source the day before the 

planned promulgation of a rule setting emissions floors. The 

Environmental Petitioners’ interpretation would require EPA 

to pause the rulemaking process and recalculate its standards to 

reflect the new information that EPA newly “has” in its 

possession. And that same issue would repeat itself if a single 

boiler sent EPA new information after it had completed that 

next round of emissions floor calculations. We do not think 

that Congress intended for Section 112(d) to force EPA into 

such a never-ending loop. Cf. U.S. Sugar Corp. I, 830 F.3d at 

647 (rejecting a proposed interpretation that would complicate 

EPA’s attempts to control pollutants and noting that “[n]othing 

in the CAA suggests that the Congress intended to so hamstring 

the Agency”). And we should not lightly read the statutory text 

to require EPA to act in a manner that is “self-defeating.” See 

Quarles v. United States, 587 U.S. 645, 654 (2019).

Moreover, this Court has generally acknowledged that 

EPA may exercise discretion and utilize its expertise when 

calculating emission standards for categories of sources. See, 

e.g., id. at 636. This Court has upheld, for example, EPA’s 

choice to set emission standards under Section 112(d)(3) by 

estimating the best performing twelve percent of sources based 

on the performance of the available technology, rather than 

solely on “the recorded performance” of sources in a category. 

See Nat’l Lime Ass’n v. EPA, 233 F.3d 625, 631–32 (D.C. Cir. 

2000). In doing so, we explained that Section 112 “says 

nothing about what data the Agency should use to calculate 

emission standards.” Id. at 632. Yet the Environmental 

Petitioners’ reading of Section 112(d)(3) would seemingly 

contradict this precedent by insisting that EPA has no 

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discretion in choosing what data to use when setting these 

standards. In fact, under the Environmental Petitioners’ 

interpretation, EPA would seemingly lack discretion to ignore 

data even when that data is unusable for some reason. Imagine, 

for example, that the only data EPA has for a particular source 

in a subcategory of sources is unusable or unreliable. So EPA, 

quite reasonably, chooses to ignore that data—and, effectively, 

that source—when establishing the MACT floor for the 

relevant subcategory. Under the Environmental Petitioners’ 

reading of Section 112(d)(3), EPA’s choice to ignore that 

unusable data would be unlawful: EPA literally “ha[d]” 

information for a source in a subcategory, so it was required to 

include that source in its calculations and use the unreliable 

data. We find it quite implausible that Congress intended for 

the language to which the Environmental Petitioners point to 

remove EPA’s widely accepted ability to use its expertise to 

craft sensible standards. 

The upshot of the Environmental Petitioners’ statutory 

argument is that if EPA “has” information about a source, it 

must include that source in its calculations—even if the only 

information it has is unusable or if EPA receives that 

information a week before a rule is to be proposed. Because 

that interpretation of Section 112(d) would substantially 

hamper EPA’s ability to effectively promulgate standards, we 

reject Environmental Petitioners’ interpretation and hold that 

EPA’s decision to rely on its original dataset was not 

unlawful.10

10 Environmental Petitioners contend that affirming EPA’s 

decision to rely on its original dataset effectively allows EPA 

unlimited discretion to “selectively exclude valid emissions data 

from its floor calculations,” thereby permitting EPA to tailor 

standards to meet its policy goals. Environmental Pet. Br. 31. But 

we do not hold that there are no statutory limitations on the data that 

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B

The Environmental Petitioners next contend that even if 

EPA’s decision to rely on its original dataset did not contravene 

Section 112, EPA’s action was arbitrary and capricious in two 

related ways. First, they contend that even if EPA was not 

under a statutory obligation to continue collecting newer data, 

it was still arbitrary for EPA to choose not to use the newer data 

already in its possession. Second, the Environmental 

Petitioners explain that as a result of EPA’s refusal to use that 

newer data, several of the 2022 Rule’s standards are less 

protective than the prior standards in the 2013 Rule that were 

remanded by this Court in U.S. Sugar Corp. II. Until the 

promulgation of the 2022 Rule, every boiler was required to 

comply with the 2013 standards remanded by this Court in U.S. 

Sugar Corp. I and U.S. Sugar Corp. II. That many of the 2022 

Rule’s standards are less stringent than the 2013 standards, 

Environmental Petitioners emphasize, effectively means that 

the 2022 standards are worse than the emissions level every 

boiler has been required to achieve for years. As we will 

explain, Environmental Petitioners’ arbitrary and capricious 

arguments are unpersuasive. 

In the 2022 Rule, EPA explained that it had chosen to rely 

on the original dataset underlying the 2013 Rule because of, 

among other reasons, the “limited nature” of this Court’s 

remand to EPA in U.S. Sugar Corp. II, 87 Fed. Reg. at 60822; 

EPA must take into account or that EPA can arbitrarily remove 

individual data points from its analysis. Rather, because we reject 

Environmental Petitioners’ proffered interpretation, we need not 

reach the question whether Section 112(d)(3) imposes restrictions on 

EPA’s choice of data (beyond, of course, the general constraint that 

EPA’s decision cannot be arbitrary and capricious). 

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EPA noted that the U.S. Sugar Corp. II Court had directed EPA 

to correct its prior standards, not to initiate a new standardsetting process altogether, id. at 60821. Further, EPA 

explained that if EPA were to revise the relevant standards 

using the updated emissions information in its possession, that 

could result in a “potentially inequitable outcome”—some 

units could be subject to “more stringent standards solely 

because of the EPA’s error” when it initially calculated the 

standards in the 2013 Rule. 87 Fed. Reg. at 60822. And, EPA 

explained, revising all of the standards in the 2013 Rule using 

the newer data would “require EPA to incur a significant 

resource burden.” Id. 

We do not think EPA’s decision to rely on the original data 

underlying the 2013 Rule when it promulgated the 2022 

standards was arbitrary and capricious. To begin with, EPA’s 

decision to rely on the original dataset was reasonable 

considering this Court’s instructions to EPA in U.S. Sugar

Corp. II. As EPA correctly recognized, this Court’s remand in 

U.S. Sugar Corp. II was limited: the Court ordered EPA to 

“identify those standards for which the MACT floor would 

have differed” if EPA had not made the error the Court 

identified in the case, and then to “revise those standards” 

consistent with this Court’s opinion in U.S. Sugar Corp. I. U.S. 

Sugar Corp. II, 844 F.3d at 270 (citing U.S. Sugar Corp. I, 830 

F.3d at 632). And the U.S. Sugar Corp. II Court also 

emphasized that EPA should not drag its feet on remand: the 

Court stated that it “expect[ed] the EPA to complete this 

rulemaking promptly.” Id. In light of the limited nature of this 

Court’s remand and the Court’s instruction to complete the 

rulemaking with haste, EPA’s decision to rely on its original 

dataset was sensible. So, too, was EPA’s explanation that 

relying on the original dataset would also allow the agency to 

ensure consistency across the full suite of standards. 

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In fact, this Court has previously upheld EPA’s decision to 

rely on a prior dataset, rather than updated data, in rather 

similar circumstances. In Board of Commissioners of Weld 

County, Colorado v. EPA, this Court addressed EPA’s actions 

in response to the Court’s prior remand of EPA’s 

determinations as to whether certain geographic areas were 

“attainment areas”—that is, whether pollutants in the relevant 

areas fell below the natural ambient air quality standards 

(“NAAQS”). 72 F.4th 284, 289 (D.C. Cir. 2023). When it 

reexamined its attainment determinations on remand, EPA 

chose to rely on the data it had used in making its original 

attainment determinations, rather than more recent data that 

was available to it. See id. at 288. Weld County, Colorado, 

petitioned for review of EPA’s revised attainment 

designations, arguing that EPA’s decision to rely on the 

original data was arbitrary and capricious. Id. at 289. EPA 

explained that using the original dataset would “standardize its 

analysis and thus facilitate consistent treatment of all affected” 

geographic areas. Id. Using the original dataset would also 

“streamline the process,” thus allowing EPA to better comply 

with the Court’s prior instruction that EPA should act “as 

expeditiously as practicable” on remand. Id. (cleaned up). 

This Court held that EPA had acted reasonably in declining to 

use the updated data on remand. The Court explained that EPA 

had “plausibly explained why the benefits of a matched 

dataset—greater parity among counties and faster 

turnaround—make the original data a better choice than partial 

updating.” Id. at 290.

Here, as in Weld County, this Court instructed EPA to 

complete its rulemaking on remand “promptly.” U.S. Sugar

Corp. II, 844 F.3d at 270 (instructing EPA to act “promptly”). 

And EPA has reasonably explained that relying on its original 

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dataset, rather than engaging in a full-blown data gathering and 

assessment process, better enabled it to promulgate revised 

standards quickly. We think EPA’s decision to rely on its 

original dataset, much like EPA’s decision in Weld County, 

was reasonable.

The Environmental Petitioners’ contrary arguments are 

unavailing. The Environmental Petitioners make much of the 

fact that some of the revised MACT floor standards in the 2022 

Rule are less stringent than the emissions limitations required 

by the 2013 Rule. But we note that, in the 2022 Rule, EPA 

explained that it had examined the post-2013 data and chosen 

to promulgate beyond-the-floor standards that require several 

subcategories to comply with the original 2013 limits. See 87 

Fed. Reg. at 60825–26. So, while the MACT floors are in some 

cases less stringent than the 2013 Rule standards, many of the 

ultimate standards with which sources must comply are just as 

stringent. We are similarly unpersuaded by the Environmental 

Petitioners’ arguments that EPA has, in this case, sought to 

advance its “policy goals” by “selectively including or 

excluding sources from its floor analysis.” Environmental Pet. 

Reply Br. at 25. For one thing, nothing in the record indicates 

that EPA’s decision to rely on the original dataset represents an 

EPA policy choice to have less stringent standards. The 

Environmental Petitioners argue to the contrary, repeatedly 

quoting from EPA’s statement in the 2022 Rule that using the 

newer data to revise the affected standards would result in 

“more stringent” standards. Id.; see also 87 Fed. Reg. at 60822. 

But the full context of the Environmental Petitioners’ chosen 

quote tells a different story. EPA did not state that it preferred, 

as a policy matter, not to have “more stringent” standards—it 

stated that it would be “potentially inequitable” for some units 

to be subject to “more stringent” standards than others simply 

because of EPA’s error in the calculations that led to the 

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standards in the 2013 Rule. See 87 Fed. Reg. at 60822. The 

Environmental Petitioners’ selective quotation from the record 

is therefore unpersuasive. And for another thing, the 

Environmental Petitioners offer no evidence that EPA has, in 

fact, “selectively” included or excluded sources. The 

Environmental Petitioners’ qualm with EPA is that EPA chose 

to use the 2013 dataset, as a whole—not that EPA has removed 

individual sources from categories in order to arrive at the 

standards it prefers.

IV

We hold that the 2022 Rule misinterpreted the definition 

of “new source” and accordingly grant the petitions for review 

filed by the Industry Petitioners, setting the Rule aside to the 

extent that it defines sources constructed or reconstructed 

before August 24, 2020 as new sources. We also hold that 

EPA’s decision to rely on its original dataset was neither a 

violation of Section 112(d) nor arbitrary and capricious, and we 

therefore deny the petition for review filed by the 

Environmental Petitioners.

So ordered.

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