S. D. Warren Co. v. Maine Board of Environmental Protection

(Slip Opinion) OCTOBER TERM, 2005 1

Syllabus

NOTE: Where it is feasible, a syllabus (headnote) will be released, as is
being done in connection with this case, at the time the opinion is issued.
The syllabus constitutes no part of the opinion of the Court but has been
prepared by the Reporter of Decisions for the convenience of the reader.
See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337.

SUPREME COURT OF THE UNITED STATES

Syllabus

S. D. WARREN CO. v. MAINE BOARD OF ENVIRON

MENTAL PROTECTION ET AL.

CERTIORARI TO THE SUPREME JUDICIAL COURT OF MAINE

No. 04–1527. Argued February 21, 2006—Decided May 15, 2006
Petitioner company (Warren) asked the Federal Energy Regulatory
Commission (FERC) to renew federal licenses for five of the hydroe
lectric dams it operates on a Maine river to generate power for its
paper mill. Each dam impounds water, which is then run through
turbines and returned to the riverbed, passing around a section of the
river. Under protest, Warren applied for water quality certifications
from respondent Maine Board of Environmental Protection pursuant
to §401 of the Clean Water Act, which requires state approval of “any
activity” “which may result in any discharge into the [Nation’s] navi
gable waters.” FERC licensed the dams subject to compliance with
those certifications, which require Warren to maintain a minimum
stream flow and to allow passage for certain fish and eels. After los
ing state administrative appeals, Warren filed suit in a state court,
which rejected Warren’s claim that its dams do not result in a “dis
charge” under §401. The State Supreme Judicial Court affirmed.
Held: Because a dam raises a potential for a discharge, §401 is trig
gered and state certification is required. Pp. 3–15.
(a) The Clean Water Act does not define “discharge,” but provides
that the term “when used without qualification includes a discharge
of a pollutant, and a discharge of pollutants,” 33 U. S. C. §1362(16).
But “discharge” is presumably broader, else superfluous, and since it
is neither defined nor a term of art, it should be construed “in accor
dance with its ordinary or natural meaning,” FDIC v. Meyer, 510
U. S. 471, 476. When applied to water, discharge commonly means
“flowing or issuing out,” Webster’s New International Dictionary 742.
This Court has consistently intended that meaning in prior water
cases, including the only case focused on §401, PUD No. 1 of Jefferson
Cty. v. Washington Dept. of Ecology, 511 U. S. 700, in which no one
2 S. D. WARREN CO. v. MAINE BD. OF ENVIRONMENTAL

PROTECTION

Syllabus

questioned that the discharge of water from a dam fell within §401’s
ambit. The Environmental Protection Agency and FERC have also
regularly read “discharge” to cover releases from hydroelectric dams.
Pp. 3–6.
(b) Warren’s three arguments for avoiding this common reading are
unavailing. The canon noscitur a sociis—“a word is known by the
company it keeps,” Gustafson v. Alloyd Co., 513 U. S. 561, 575—does
not apply here. Warren claims that since “discharge” is keeping
company with “discharge” defined as adding one or more pollutants,
see §1362(12), discharge standing alone must also require the addi
tion of something foreign to the water. This argument seems to as
sume that pairing a broad statutory term with a narrow one shrinks
the broad one, but there is no such general usage of language this
way. Warren also relies on South Fla. Water Management Dist. v.
Miccosukee Tribe, 541 U. S. 95, but that case is not on point. It ad
dressed §402, not §401, and the two sections are not interchangeable,
as they serve different purposes and use different language to reach
them. Thus, that something must be added in order to implicate
§402 does not explain what suffices for a discharge under §401. Fi
nally, the Clean Water Act’s legislative history, if it means anything,
goes against Warren’s reading of “discharge.” Pp. 6–12.
(c) Warren’s arguments against reading “discharge” in its common
sense also miss the forest for the trees. Congress passed the Clean
Water Act to “restore and maintain the chemical, physical, and bio
logical integrity of the Nation’s waters,” 33 U. S. C. §1251(a), the “na
tional goal” being to achieve “water quality [providing] for the protec
tion and propagation of fish . . . and . . . for recreation,” §1251(a)(2).
To do this, the Act deals with “pollution” generally, see §1251(b),
which it defines as “the man-made or man-induced alteration of the
[water’s] chemical, physical, biological, and radiological integrity,”
§1362(19). Because the alteration of water quality as thus defined is
a risk inherent in limiting river flow and releasing water through
turbines, changes in the river’s flow, movement, and circulation fall
within a State’s legitimate legislative business. State certifications
under §401 are essential in the scheme to preserve state authority to
address the broad range of pollution. Reading §401 to give “dis
charge” its common and ordinary meaning preserves the state au
thority apparently intended. Pp. 12–15.
2005 ME 27, 868 A. 2d 210, affirmed.

SOUTER, J., delivered the opinion of the Court, in which ROBERTS,
C. J., and STEVENS, KENNEDY, THOMAS, GINSBURG, BREYER, and ALITO,
JJ., joined, and in which SCALIA, J., joined as to all but Part III–C.
 Cite as: 547 U. S. ____ (2006) 1

Opinion of the Court

NOTICE: This opinion is subject to formal revision before publication in the
preliminary print of the United States Reports. Readers are requested to
notify the Reporter of Decisions, Supreme Court of the United States, Wash
ington, D. C. 20543, of any typographical or other formal errors, in order
that corrections may be made before the preliminary print goes to press.

SUPREME COURT OF THE UNITED STATES
_________________

No. 04–1527
_________________

S. D. WARREN COMPANY, PETITIONER v. MAINE

BOARD OF ENVIRONMENTAL PROTECTION ET AL.

ON WRIT OF CERTIORARI TO THE SUPREME JUDICIAL COURT
OF MAINE
[May 15, 2006]

JUSTICE SOUTER delivered the opinion of the Court.*
The issue in this case is whether operating a dam to
produce hydroelectricity “may result in any discharge into
the navigable waters” of the United States. If so, a federal
license under §401 of the Clean Water Act requires state
certification that water protection laws will not be vio
lated. We hold that a dam does raise a potential for a
discharge, and state approval is needed.
I
The Presumpscot River runs through southern Maine
from Sebago Lake to Casco Bay, and in the course of its 25
miles petitioner, S. D. Warren Company, operates several
hydropower dams to generate electricity for its paper mill.
Each dam creates a pond, from which water funnels into a
“power canal,” through turbines, and back to the riverbed,
passing around a section of the river just below the im
poundment.
It is undisputed that since 1935, Warren has needed a
license to operate the dams, currently within the authority
——————
* JUSTICE SCALIA joins all but Part III–C of this opinion.
2 S. D. WARREN CO. v. MAINE BD. OF ENVIRONMENTAL

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Opinion of the Court

of the Federal Energy Regulatory Commission (FERC)
under the Federal Power Act. 16 U. S. C. §§817(1), 792;
see also Public Utility Act of 1935, §210, 49 Stat. 846.
FERC grants these licenses for periods up to 50 years, 16
U. S. C. §799, after a review that looks to environmental
issues as well as the rising demand for power, §797(e).
Over 30 years ago, Congress enacted a specific provision
for licensing an activity that could cause a “discharge” into
navigable waters; a license is conditioned on a certification
from the State in which the discharge may originate that
it will not violate certain water quality standards, includ
ing those set by the State’s own laws. See Water Quality
Improvement Act of 1970, §103, 84 Stat. 108. Today, this
requirement can be found in §401 of the Clean Water Act,
86 Stat. 877, codified at 33 U. S. C. §1341: “Any applicant
for a Federal license or permit to conduct any activity . . .
which may result in any discharge into the navigable
water[s] shall provide the licensing or permitting agency a
certification from the State in which the discharge origi
nates . . . .” §1341(a)(1).
“Any certification provided under this section shall
set forth any effluent limitations and other limita
tions, and monitoring requirements necessary to as
sure that any applicant for a Federal license or permit
will comply with [§§1311, 1312, 1316, and 1317] and
with any other appropriate requirement of State law
set forth in such certification, and shall become a con
dition on any Federal license or permit subject to the
provisions of this section.”1 §1341(d).

——————
1 The statutes cross-referenced go to effluent limitations and other

limitations, 33 U. S. C. §§1311, 1312, standards of performance, §1316,
and toxic effluent standards, §1317. As we have explained before, “state
water quality standards adopted pursuant to §303 [of the Clean Water
Act, 33 U. S. C. §1313,] are among the ‘other limitations’ with which a
State may ensure compliance through the §401 certification process.”
 Cite as: 547 U. S. ____ (2006) 3

Opinion of the Court

In 1999, Warren sought to renew federal licenses for five
of its hydroelectric dams. It applied for water quality
certifications from the Maine Department of Environ
mental Protection (the state agency responsible for what
have come to be known as “401 state certifications”), but it
filed its application under protest, claiming that its dams
do not result in any “discharge into” the river triggering
application of §401.
The Maine agency issued certifications that required
Warren to maintain a minimum stream flow in the by
passed portions of the river and to allow passage for vari
ous migratory fish and eels. When FERC eventually
licensed the five dams, it did so subject to the Maine con
ditions, and Warren continued to deny any need of §401
state certification. After appealing unsuccessfully to
Maine’s administrative appeals tribunal, the Board of
Environmental Protection, Warren filed this suit in the
State’s Cumberland County Superior Court. That court
rejected Warren’s argument that its dams do not result in
discharges, and the Supreme Judicial Court of Maine
affirmed. S. D. Warren Co. v. Board of Environmental
Protection, 2005 ME 27, 868 A. 2d 210. We granted certio
rari, 546 U. S. ___ (2005), and now affirm as well.
II
The dispute turns on the meaning of the word “dis
charge,” the key to the state certification requirement
under §401.2 The Act has no definition of the term, but
provides that “[t]he term ‘discharge’ when used without
qualification includes a discharge of a pollutant, and a
discharge of pollutants.”3 33 U. S. C. §1362(16). It does
——————
PUD No. 1 of Jefferson Cty. v. Washington Dept. of Ecology, 511 U. S. 700,
713 (1994).
2 No one disputes that the Presumpscot River is a navigable water of

the United States.
3 The term “pollutant” is defined in the Act to mean “dredged spoil,
4 S. D. WARREN CO. v. MAINE BD. OF ENVIRONMENTAL
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Opinion of the Court

define “discharge of a pollutant” and “discharge of pollut
ants,” as meaning “any addition of any pollutant to navi
gable waters from any point source.” §1362(12). But
“discharge” presumably is broader, else superfluous, and
since it is neither defined in the statute nor a term of art,
we are left to construe it “in accordance with its ordinary
or natural meaning.” FDIC v. Meyer, 510 U. S. 471, 476
(1994).
When it applies to water, “discharge” commonly means
a “flowing or issuing out,” Webster’s New International
Dictionary 742 (2d ed. 1949); see also ibid. (“[t]o emit; to
give outlet to; to pour forth; as, the Hudson discharges its
waters into the bay”), and this ordinary sense has consis
tently been the meaning intended when this Court has
used the term in prior water cases. See, e.g., Marsh v.
Oregon Natural Resources Council, 490 U. S. 360, 364
(1989) (describing a dam’s “ ‘multiport’ structure, which
will permit discharge of water from any of five levels”);
Arizona v. California, 373 U. S. 546, 619, n. 25 (1963)
(Harlan, J., dissenting in part) (quoting congressional
testimony regarding those who “ ‘take . . . water out of the
stream which has been discharged from the reservoir’ ”);
United States v. Arizona, 295 U. S. 174, 181 (1935)
(“Parker Dam will intercept waters discharged at Boulder
Dam”).
In fact, this understanding of the word “discharge” was
accepted by all Members of the Court sitting in our only
other case focused on §401 of the Clean Water Act, PUD
No. 1 of Jefferson Cty. v. Washington Dept. of Ecology, 511
U. S. 700 (1994). At issue in PUD No. 1 was the State of

Washington’s authority to impose minimum stream flow

——————

solid waste, incinerator residue, sewage, garbage, sewage sludge,

munitions, chemical wastes, biological materials, radioactive materials,
heat, wrecked or discarded equipment, rock, sand, cellar dirt and
industrial, municipal, and agricultural waste discharged into water.”
33 U. S. C. §1362(6).
 Cite as: 547 U. S. ____ (2006) 5

Opinion of the Court

rates on a hydroelectric dam, and in posing the question
presented, the Court said this:
“There is no dispute that petitioners were required
to obtain a certification from the State pursuant to
§401. Petitioners concede that, at a minimum, the
project will result in two possible discharges—the re
lease of dredged and fill material during the construc
tion of the project, and the discharge of water at the
end of the tailrace after the water has been used to
generate electricity.” Id., at 711.
The Pud No. 1 petitioners claimed that a state condition
imposing a stream flow requirement on discharges of
water from a dam exceeded the State’s §401 authority to
prevent degradation of water quality, but neither the
parties nor the Court questioned that the “discharge of
water” from the dam was a discharge within the ambit of
§401. Ibid. And although the Court’s opinion made no
mention of the dam as adding anything to the water, the
majority’s use of the phrase “discharge of water” drew no
criticism from the dissent, which specifically noted that
“[t]he term ‘discharge’ is not defined in the [Clean Water
Act] but its plain and ordinary meaning suggests ‘a flow
ing or issuing out,’ or ‘something that is emitted.’ ” Id., at
725 (opinion of THOMAS, J.) (quoting Webster’s Ninth New
Collegiate Dictionary 360 (1991)).
In resort to common usage under §401, this Court has
not been alone, for the Environmental Protection Agency
(EPA) and FERC have each regularly read “discharge” as
having its plain meaning and thus covering releases from
hydroelectric dams. See, e.g., EPA, Water Quality Stan
dards Handbook §7.6.3, p. 7–10 (2d ed. 1994) (“EPA has
identified five Federal permits and/or licenses that author
ize activities that may result in a discharge to the waters[,
including] licenses required for hydroelectric projects
issued under the Federal Power Act”); FPL Energy Maine
6 S. D. WARREN CO. v. MAINE BD. OF ENVIRONMENTAL
PROTECTION
Opinion of the Court

Hydro LLC, 111 FERC ¶61,104, P. 61,505 (2005) (reject
ing, in a recent adjudication, the argument that Congress
“used the term ‘discharge’ as nothing more than a short
hand expression for ‘discharge of a pollutant or pollut
ants’ ”).4 Warren is, of course, entirely correct in caution
ing us that because neither the EPA nor FERC has
formally settled the definition, or even set out agency
reasoning, these expressions of agency understanding do
not command deference from this Court. See Gonzales v.
Oregon, 546 U. S. ___, ___ (2006) (slip op., at 11) (“Chevron
deference . . . is not accorded merely because the statute is
ambiguous and an administrative official is involved”);
Skidmore v. Swift & Co., 323 U. S. 134, 140 (1944). But
even so, the administrative usage of “discharge” in this
way confirms our understanding of the everyday sense of
the term.
III
Warren makes three principal arguments for reading
the term “discharge” differently from the ordinary way.
We find none availing.
A
The first involves an interpretive canon we think is out
of place here. The canon, noscitur a sociis, reminds us
——————
4 Warren relies on a document from the EPA as a counterexample of

the EPA’s position in this regard. See Memorandum from Ann R. Klee,
EPA General Counsel et al., to Regional Administrators, regarding
“Agency Interpretation on Applicability of Section 402 of the Clean
Water Act to Water Transfers” (Aug. 5, 2005), available at
http://www.epa.gov/ogc/documents/water_transfers.pdf (as visited Apr.
13, 2006, and available in Clerk of Court’s case file). The memorandum
does not help Warren, however; it interprets §402 of the Clean Water
Act, not §401, and construes the statutory phrase “discharge of a
pollutant,” which, as explained below, implies a meaning different
under the statute from the word “discharge” used alone. The memo
randum, in fact, declares that “[i]t does not address any . . . terms
under the statute other than ‘addition.’ ” Id., at 18.
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Opinion of the Court

that “a word is known by the company it keeps,” Gustafson
v. Alloyd Co., 513 U. S. 561, 575 (1995), and is invoked when
a string of statutory terms raises the implication that the
“words grouped in a list should be given related meaning,”
Dole v. Steelworkers, 494 U. S. 26, 36 (1990) (internal quota
tion marks omitted); see also Beecham v. United States, 511
U. S. 368, 371 (1994) (“That several items in a list share an
attribute counsels in favor of interpreting the other items as
possessing that attribute as well”).
Warren claims that the canon applies to §502(16) of the
Clean Water Act, which provides that “[t]he term ‘dis
charge’ when used without qualification includes a dis
charge of a pollutant, and a discharge of pollutants.” 33
U. S. C. §1362(16). Warren emphasizes that the “in
clude[d]” terms, pollutant discharges, are themselves
defined to require an “addition” of pollutants to water.
§1362(12). Since “discharge” pure and simple is keeping
company with “discharge” defined as adding one or more
pollutants, Warren says “discharge” standing alone must
require the addition of something foreign to the water into
which the discharge flows. And because the release of
water from the dams adds nothing to the river that was
not there above the dams, Warren concludes that water
flowing out of the turbines cannot be a discharge into the
river.5
——————
5 We note that the Supreme Judicial Court of Maine accepted the

assertion that “[a]n ‘addition’ is the fundamental characteristic of any
discharge.” 2005 Me 27, ¶11, 868 A. 2d 210, 215. It then held that
Warren’s dams add to the Presumpscot River because the water “los[es
its] status as waters of the United States” when diverted from its
natural course, and becomes an addition to the waters of the United
States when redeposited into the river. 868 A. 2d, at 216 (emphasis
deleted). We disagree that an addition is fundamental to any dis
charge, nor can we agree that one can denationalize national waters by
exerting private control over them. Cf. United States v. Chandler-
Dunbar Water Power Co., 229 U. S. 53, 69 (1913) (“[T]hat the running
water in a great navigable stream is capable of private ownership is
8 S. D. WARREN CO. v. MAINE BD. OF ENVIRONMENTAL

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Opinion of the Court

The problem with Warren’s argument is that it purports
to extrapolate a common feature from what amounts to a
single item (discharge of a pollutant plus the plural vari
ant involving more than one pollutant). See Beecham,
supra, at 371. The argument seems to assume that pair
ing a broad statutory term with a narrow one shrinks the
broad one, but there is no such general usage; giving one
example does not convert express inclusion into restrictive
equation, and noscitur a sociis is no help absent some sort
of gathering with a common feature to extrapolate. It
should also go without saying that uncritical use of inter
pretive rules is especially risky in making sense of a com
plicated statute like the Clean Water Act, where technical
definitions are worked out with great effort in the legisla
tive process. Cf. H. R. Rep. No. 92–911, p. 125 (1972) (“[I]t
is extremely important to an understanding of [§402] to
know the definition of the various terms used and a
careful reading of the definitions . . . is recommended.
Of particular significance [are] the words ‘discharge of
pollutants’ ”).
B
Regardless, Warren says the statute should, and even
must, be read its way, on the authority of South Fla. Water
Management Dist. v. Miccosukee Tribe, 541 U. S. 95 (2004).
But that case is not on point. Miccosukee addressed §402 of
the Clean Water Act, not §401, and the two sections are
not interchangeable, as they serve different purposes and
use different language to reach them. Section 401 recast
pre-existing law and was meant to “continu[e] the author
ity of the State . . . to act to deny a permit and thereby
prevent a Federal license or permit from issuing to a
discharge source within such State.” S. Rep. No. 92–414,

——————
inconceivable”). Thus, though we affirm the Maine judgment, we do so
on different reasoning.
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Opinion of the Court

p. 69 (1971). Its terms have a broad reach, requiring state
approval any time a federally licensed activity “may”
result in a discharge (“discharge” of course being without
any qualifiers here), 33 U. S. C. §1341(a)(1), and its object
comprehends maintaining state water quality standards,
see n. 1, supra.
Section 402 has a historical parallel with §401, for the
legislative record suggests that it, too, was enacted to
consolidate and ease the administration of some predeces
sor regulatory schemes, see H. R. Rep. No. 92–911, at 124–
125. But it contrasts with §401 in its more specific focus.
It establishes what Congress called the National Pollutant
Discharge Elimination System, requiring a permit for the
“discharge of any pollutant” into the navigable waters of
the United States, 33 U. S. C. §1342(a). The triggering
statutory term here is not the word “discharge” alone, but
“discharge of a pollutant,” a phrase made narrower by its
specific definition requiring an “addition” of a pollutant to
the water. §1362(12).
The question in Miccosukee was whether a pump be
tween a canal and an impoundment produced a “discharge
of a pollutant” within the meaning of §402, see 541 U. S.,
at 102–103, and the Court accepted the shared view of the
parties that if two identified volumes of water are “simply
two parts of the same water body, pumping water from
one into the other cannot constitute an ‘addition’ of pollut
ants,” id., at 109. Miccosukee was thus concerned only
with whether an “addition” had been made (phosphorous
being the substance in issue) as required by the definition
of the phrase “discharge of a pollutant”; it did not matter
under §402 whether pumping the water produced a dis
charge without any addition. In sum, the understanding
that something must be added in order to implicate §402
does not explain what suffices for a discharge under §401.6
——————
6 The fact that the parties in Miccosukee conceded that the water
10 S. D. WARREN CO. v. MAINE BD. OF ENVIRONMENTAL
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Opinion of the Court

C
Warren’s third argument for avoiding the common
meaning of “discharge” relies on the Act’s legislative his
tory, but we think that if the history means anything it
actually goes against Warren’s position. Warren suggests
that the word “includes” in the definition of “discharge”
should not be read with any spacious connotation, because
the word was simply left on the books inadvertently after
a failed attempt to deal specifically with “thermal dis
charges.” As Warren describes it, several Members of
Congress recognized that “heat is not as harmful as what
most of us view as ‘pollutants,’ because it dissipates
quickly in most bodies of receiving waters,” 1 Legislative
History of the Water Pollution Control Act Amendments of
1972 (Committee Print compiled for the Senate Committee
on Public Works by the Library of Congress), Ser. No. 93–
1, p. 273 (1973) (remarks of Cong. Clark), and they pro

——————
being pumped was polluted does not transform the Court’s analysis
from one centered on the word “addition” to one centered on the word
“discharge.” Before Miccosukee, one could have argued that transfer
ring polluted water from a canal to a connected impoundment consti
tuted an “addition.” Miccosukee is at odds with that construction of the
statute, but it says nothing about whether the transfer of polluted
water from the canal to the impoundment constitutes a “discharge.”
Likewise, we are not persuaded by Warren’s claim that the word
“into” somehow changes the meaning of the word “discharge” so as to
require an addition. See Reply Brief for Petitioner 1–2 (“However one
might read the lone word ‘discharge’ by itself, the complete statutory
phrase ‘discharge into the navigable waters’ entails the introduction of
something into the waters”). The force of this argument escapes us,
since one can easily refer to water being poured or discharged out of one
place into another without implying that an addition of some hitherto
unencountered mixture or quality of water is made. Indeed, the prepo
sition “into” was used without connoting an addition in the Miccosukee
analogy cited by Warren. See 541 U. S., at 110 (“[I]f one takes a ladle of
soup from a pot . . . and pours it back into the pot, one has not ‘added’
soup or anything else to the pot” (internal quotation marks and brack
ets omitted)).
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Opinion of the Court

posed to regulate thermal discharges less stringently than
others. They offered an amendment to exclude thermal
discharges from the requirements under §402, but they
also wanted to ensure that thermal discharges remained
within the scope of §401 and so sought to include them
expressly in the general provision covering “discharge.”
See id., at 1069–1070, 1071. The proposed definition read,
“[t]he term ‘discharge’ when used without qualification
includes a discharge of a pollutant, a discharge of pollut
ants, and a thermal discharge.” Id., at 1071.
Of course, Congress omitted the reference to “thermal
discharge,” and settled on the definition we have today.
See Federal Water Pollution Control Act Amendments of
1972, §502(16), 86 Stat. 887. Warren reasons that once
Congress abandoned the special treatment for thermal
pollutants, it merely struck the words “thermal discharge”
from 33 U. S. C. §1362(16) and carelessly left in the word
“includes.” Thus, Warren argues, there is no reason to
assume that describing “discharge” as including certain
acts was meant to extend the reach of §401 beyond acts of
the kind specifically mentioned;7 the terminology of §401
simply reflects a failed effort to narrow the scope of §402.
This is what might be called a lawyer’s argument. We
will assume that Warren is entirely correct about the
impetus behind the failed attempt to rework the scope of
pollutant discharge under §402. It is simply speculation,
though, to say that the word “includes” was left in the
description of a “discharge” by mere inattention, and for
reasons given in Part IV of this opinion it is implausible
speculation at that. But if we confine our view for a mo
ment strictly to the drafting history, the one thing clear is
that if Congress had left “thermal discharge” as an in
——————
7 Warren is hesitant to follow its own logic to completion by simply

claiming that §401 covers nothing but what §502(16) mentions, the
discharge of a pollutant or pollutants.
12 S. D. WARREN CO. v. MAINE BD. OF ENVIRONMENTAL
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Opinion of the Court

cluded subclass of a “discharge” under §502(16), Warren
would have a stronger noscitur a sociis argument. For a
thermal discharge adds something, the pollutant heat, see
n. 3, supra. Had the list of examples of discharge been
lengthened to include thermal discharges, there would
have been at least a short series with the common feature
of addition. As it stands, however, the only thing the
legislative history cited by Warren demonstrates is the
congressional rejection of language that would have cre
ated a short series of terms with a common implication of
an addition.
Warren’s theory, moreover, has the unintended conse
quence of underscoring that Congress probably distin
guished the terms “discharge” and “discharge of pollut
ants” deliberately, in order to use them in separate places
and to separate ends. Warren hypothesizes that Congress
attempted to tinker with the definition of “discharge”
because it wanted to subject thermal discharges to the
requirements of §401, but not §402. But this assumption
about Congress’s motives only confirms the point that
when Congress fine-tunes its statutory definitions, it
tends to do so with a purpose in mind. See Bates v. United
States, 522 U. S. 23, 29–30 (1997) (if “Congress includes
particular language in one section of a statute but omits it
in another section of the same Act, it is generally presumed
that Congress acts intentionally and purposely in the
disparate inclusion or exclusion” (internal quotation marks
omitted)).
IV
Warren’s arguments against reading the word “dis
charge” in its common sense fail on their own terms. 8
——————
8 Warren briefly makes another argument for disregarding the plain
meaning of the word “discharge,” relying on §511(c)(2) of the Clean
Water Act, 33 U. S. C. §1371(c)(2). This section addresses the intersec
tion of the Act with another statute, the National Environmental Policy
 Cite as: 547 U. S. ____ (2006) 13

Opinion of the Court

They also miss the forest for the trees.
Congress passed the Clean Water Act to “restore and
maintain the chemical, physical, and biological integrity of
the Nation’s waters,” 33 U. S. C. §1251(a); see also PUD
No. 1, 511 U. S., at 714, the “national goal” being to achieve
“water quality which provides for the protection and propa
gation of fish, shellfish, and wildlife and provides for recrea
tion in and on the water.” 33 U. S. C. §1251(a)(2). To do
this, the Act does not stop at controlling the “addition of
pollutants,” but deals with “pollution” generally, see
§1251(b), which Congress defined to mean “the man-made
or man-induced alteration of the chemical, physical, biologi
cal, and radiological integrity of water.” §1362(19).
——————
Act of 1969 (NEPA), 42 U. S. C. §4321 et seq. NEPA “imposes only
procedural requirements on federal agencies with a particular focus on
requiring agencies to undertake analyses of the environmental impact
of their proposals and actions.” Department of Transportation v. Public
Citizen, 541 U. S. 752, 756–757 (2004). Section 511(c)(2) makes the point
that nothing in NEPA authorizes any federal agency “authorized to
license or permit the conduct of any activity which may result in the
discharge of a pollutant” to review “any effluent limitation or other
requirement established pursuant to this chapter or the adequacy of
any certification under [§401] of this title.” 33 U. S. C. §1371(c)(2).
Warren argues that reading §401 to cover discharges generally would
preclude duplicative NEPA review of certifications involving pollutant
discharges, but allow such review of those involving nonpollutant
discharges.
But Warren overlooks the fact that “discharge of a pollutant” is used
in §511(c)(2) in the course of identifying the agency, not the activity to
be certified. Whether a §401 certification involves an activity that
discharges pollutants or one that simply discharges, FERC (as an
agency that may be described, always, as one with “author[ity] to
license or permit the conduct of any activity which may result in the
discharge of a pollutant,” ibid.) may not review it. Thus, nothing in
§511(c)(2) is disturbed by our holding that hydroelectric dams require
§401 state certifications. It is still the case that, when a State has
issued a certification covering a discharge that adds no pollutant, no
federal agency will be deemed to have authority under NEPA to “re
view” any limitations or the adequacy of the §401 certification.
14 S. D. WARREN CO. v. MAINE BD. OF ENVIRONMENTAL
PROTECTION
Opinion of the Court

The alteration of water quality as thus defined is a risk
inherent in limiting river flow and releasing water
through turbines. Warren itself admits that its dams “can
cause changes in the movement, flow, and circulation of a
river . . . caus[ing] a river to absorb less oxygen and to be
less passable by boaters and fish.” Brief for Petitioner 23.
And several amici alert us to the chemical modification
caused by the dams, with “immediate impact on aquatic
organisms, which of course rely on dissolved oxygen in
water to breathe.” Brief for Trout Unlimited et al. as
Amici Curiae 13; see also, e.g., Brief for National Wildlife
Federation et al. as Amici Curiae 6 (explaining that when
air and water mix in a turbine, nitrogen dissolves in the
water and can be potentially lethal to fish). Then there
are the findings of the Maine Department of Environ
mental Protection that led to this appeal:
“The record in this case demonstrates that Warren’s
dams have caused long stretches of the natural river
bed to be essentially dry and thus unavailable as
habitat for indigenous populations of fish and other
aquatic organisms; that the dams have blocked the
passage of eels and sea-run fish to their natural
spawning and nursery waters; that the dams have
eliminated the opportunity for fishing in long
stretches of river, and that the dams have prevented
recreational access to and use of the river.” In re S. D.
Warren Co., Maine Board of Environmental Protection
(2003), in App. to Pet. for Cert. A–49.
Changes in the river like these fall within a State’s
legitimate legislative business, and the Clean Water Act
provides for a system that respects the States’ concerns.
See 33 U. S. C. §1251(b) (“It is the policy of the Congress to
recognize, preserve, and protect the primary responsibilities
and rights of States to prevent, reduce, and eliminate pollu
tion”); §1256(a) (federal funds for state efforts to prevent
 Cite as: 547 U. S. ____ (2006) 15

Opinion of the Court

pollution); see also §1370 (States may impose standards on
the discharge of pollutants that are stricter than federal
ones).
State certifications under §401 are essential in the
scheme to preserve state authority to address the broad
range of pollution, as Senator Muskie explained on the
floor when what is now §401 was first proposed:
“No polluter will be able to hide behind a Federal li
cense or permit as an excuse for a violation of water
quality standard[s]. No polluter will be able to make
major investments in facilities under a Federal license
or permit without providing assurance that the facil
ity will comply with water quality standards. No
State water pollution control agency will be con
fronted with a fait accompli by an industry that has
built a plant without consideration of water quality
requirements.” 116 Cong. Rec. 8984 (1970).
These are the very reasons that Congress provided the
States with power to enforce “any other appropriate re
quirement of State law,” 33 U. S. C. §1341(d), by imposing
conditions on federal licenses for activities that may result
in a discharge, ibid.
Reading §401 to give “discharge” its common and ordi
nary meaning preserves the state authority apparently
intended. The judgment of the Supreme Judicial Court of
Maine is therefore affirmed.
It is so ordered.