United States Sugar Corporation v. Environmental Protection Agency

United States Court of Appeals
FOR THE DISTRICT OF COLUMBIA CIRCUIT
Argued March 21, 2024 Decided September 3, 2024
No. 22-1271
UNITED S TATES S UGAR C ORPORATION ,
P ETITIONER
v.
ENVIRONMENTAL P ROTECTION A GENCY,
R ESPONDENT
S IERRA C LUB ,
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: W ILKINS , 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 already-
constructed 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 existing-
source 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 casts further 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 resists this 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 re-
proposal 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 new-
source 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 standard-
setting 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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26
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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28
EPA noted that the U.S. Sugar Corp. II Court had directed EPA
to correct its prior standards, not to initiate a new standard-
setting 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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30
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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