ALASKA DEPARTMENT OF ENVIRONMENTAL CONSERVATION v. ENVIRONMENTAL PROTECTION AGENCY et al.

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
461 OCTOBER TERM, 2003
Syllabus
ALASKA DEPARTMENT OF ENVIRONMENTAL
CONSERVATION v. ENVIRONMENTAL
PROTECTION AGENCY et al.
certiorari to the united states court of appeals for
the ninth circuit
No. 02–658. Argued October 8, 2003—Decided January 21, 2004
The Clean Air Act’s (CAA or Act) Prevention of Significant Deterioration
(PSD) program, 42 U. S. C. § 7477, was designed to ensure that the air
quality in “attainment areas,” i. e., areas that are already “clean,” will
not degrade, see § 7470(1). The program bars construction of any major
air pollutant emitting facility not equipped with “the best available con-
trol technology” (BACT). § 7475(a)(4). The Act defines BACT as “an
emission limitation based on the maximum degree of [pollutant] reduc-
tion . . . which the [state] permitting authority, on a case-by-case basis,
taking into account energy, environmental, and economic impacts and
other costs, determines is achievable for [the] facility.” § 7479(3). Two
provisions of the Act vest enforcement authority in the Environmental
Protection Agency (EPA or Agency). Section 113(a)(5) generally au-
thorizes the EPA, when it finds that a State is not complying with a
CAA “requirement” governing construction of a pollutant source, to
pursue remedial action, including issuance of “an order prohibiting the
construction.” 42 U. S. C. § 7413(a). Directed specifically to the PSD
program, CAA § 167 instructs EPA to “take such measures, including
issuance of an order, . . . as necessary to prevent the construction” of a
major pollutant emitting facility that does not conform to the “require-
ments” of the program. Because EPA has classified northwest Alaska,
the region here at issue, as an attainment area for nitrogen dioxide, the
PSD program applies to emissions of that pollutant in the region. No
“major emitting facility,” including any source emitting more than 250
tons of nitrogen oxides per year, § 7479(1), may be constructed or modi-
fied unless a PSD permit has been issued for the facility, § 7475(a)(1).
A PSD permit may not issue unless the proposed facility is subject to
BACT for each CAA-regulated pollutant emitted from the facility.
§ 7475(a)(4).
In this case, “the permitting authority” under § 7479(3) is Alaska,
acting through petitioner, the Alaska Department of Environmental
Conservation (ADEC). In 1988, Teck Cominco Alaska Inc. (Cominco)
obtained authorization to operate a zinc concentrate mine in northwest
Alaska. The mine is a “major emitting facility” under § 7475. Its ini-

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
462 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Syllabus
tial PSD permit authorized five diesel electric generators, MG–1
through MG–5, subject to operating restrictions. Under a second PSD
permit issued in 1994, Cominco added a sixth generator, MG–6. In
1996, Cominco initiated a project to expand zinc production by 40% and
applied to ADEC for a PSD permit to allow, inter alia, increased elec-
tricity generation by MG–5. ADEC preliminarily proposed as BACT
for MG–5 an emission control technology known as selective catalytic
reduction (SCR), which reduces nitrogen oxide emissions by 90%.
Amending its application, Cominco added a seventh generator, MG–17,
and proposed, as BACT, an alternative control technology—Low NOx—
that achieves a 30% reduction in nitrogen oxide pollutants. In May
1999, ADEC issued a first draft PSD permit and preliminary technical
analysis report, concluding that Low NOx was BACT for MG–5 and
MG–17. ADEC identified SCR as the most stringent technology then
technically and economically feasible. ADEC nevertheless endorsed
Cominco’s proffered emissions-offsetting alternative of fitting MG–17
and all six existing generators with Low NOx, rather than fitting MG–5
and MG–17 with SCR. This proposal, ADEC submitted, would achieve
a maximum NOx reduction similar to the reduction SCR could achieve,
and was logistically and economically less onerous for Cominco. In July
1999, EPA objected that ADEC had identified SCR as the best control
technology, but failed to require it as BACT. ADEC responded with a
second draft PSD permit and technical analysis report in September
1999, again finding Low NOx to be BACT for MG–17. ADEC’s second
draft abandoned that agency’s May 1999 emissions-offsetting justifica-
tion. ADEC further conceded that, lacking data from Cominco, it could
make no judgment as to SCR’s impact on the mine’s operation, profit-
ability, and competitiveness. It nonetheless concluded, contradicting its
earlier finding that SCR was technically and economically feasible, that
SCR imposed “a disproportionate cost” on the mine. In support of this
conclusion, ADEC analogized the mine to a rural utility that would have
to increase prices were it required to use SCR. Protesting that Com-
inco had not adequately demonstrated site-specific factors supporting
the assertion of SCR’s economical infeasibility, EPA suggested that
ADEC include an analysis of SCR’s adverse economic impacts on Com-
inco. Expressing confidentiality concerns, Cominco declined to submit
financial data. In December 1999, ADEC issued a final permit and
technical analysis report approving Low NOx as BACT for MG–17.
Again conceding that it made no judgment as to SCR’s impact on the
mine’s operation, profitability, and competitiveness, ADEC advanced, as
cause for its decision, SCR’s adverse effect on the mine’s unique and
continuing impact on the region’s economic diversity and the venture’s
“world competitiveness.” ADEC reiterated its rural Alaska utility

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
463 Cite as: 540 U. S. 461 (2004)
Syllabus
analogy, and compared SCR’s cost to the costs of other, less stringent,
control technologies.
EPA then issued three orders to ADEC under §§ 113(a)(5) and 167 of
the Act. Those orders prohibited ADEC from issuing a PSD permit to
Cominco without satisfactorily documenting why SCR was not BACT
for MG–17. In addition, EPA prohibited Cominco from beginning con-
struction or modification activities at the mine, with limited exceptions.
Ruling on ADEC’s and Cominco’s challenges to these orders, the Ninth
Circuit held that EPA had authority under §§ 113(a)(5) and 167 to deter-
mine the reasonableness or adequacy of the State’s justification for its
BACT decision. The Court of Appeals emphasized that provision of a
reasoned justification for a BACT determination by a permitting author-
ity is undeniably a CAA “requirement.” EPA had properly exercised
its discretion in issuing the three orders, the Ninth Circuit held, because
(1) Cominco failed to demonstrate SCR’s economical infeasibility, and
(2) ADEC failed to provide a reasoned justification for its elimination of
SCR as a control option.
Held: CAA authorizes EPA to stop construction of a major pollutant emit-
ting facility permitted by a state authority when EPA finds that an
authority’s BACT determination is unreasonable in light of 42 U. S. C.
§ 7479(3)’s prescribed guides. Pp. 483–502.
(a) In holding that the EPA orders constituted reviewable “final ac-
tion” under § 7607(b)(1), the Ninth Circuit correctly applied Bennett v.
Spear, 520 U. S. 154: To be “final,” agency action must “mark the con-
summation of the agency’s decisionmaking process,” and must either
determine “rights or obligations” or occasion “legal consequences,” id.,
at 177–178. As the Ninth Circuit noted, EPA had asserted its final
position on the factual circumstances underpinning the orders. If the
orders survived judicial review, Cominco could not escape the practical
and legal consequences of any ADEC-permitted construction Cominco
endeavored. P. 483.
(b) EPA may issue a stop-construction order, under CAA §§ 113(a)(5)
and 167, if a state permitting authority’s BACT selection is not reason-
able. Pp. 484–496.
(1) EPA has rationally construed CAA’s BACT definition, 42
U. S. C. § 7479(3), and the statute’s listing of BACT as a “[p]recon-
struction requiremen[t]” for the PSD program, §§ 7475(a)(1) and (4), to
mandate a determination of BACT faithful to the statute’s definition.
EPA urges that state permitting authorities’ statutory discretion is con-
strained by § 7479(3)’s strong, normative terms “maximum” and “achiev-
able.” EPA accordingly reads §§ 113(a)(5) and 167 to empower the
federal Agency to check a state agency’s unreasonably lax BACT desig-

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
464 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Syllabus
nation. In support of this reading, EPA notes that Congress intended
the PSD program to prevent significant deterioration of air quality
in clean-air areas. Without a federal Agency surveillance role that ex-
tends to BACT determinations, EPA maintains, this goal is unlikely to
be realized. The Act’s legislative history suggests that, absent national
guidelines, a State deciding to set and enforce strict clean-air standards
may lose existing industrial plants to more permissive States. The leg-
islative history further suggests that without a federal check, new
plants will play one State off against another with threats to locate in
whichever State adopts the most permissive pollution controls. The
Court agrees with EPA’s reading of the statutory provisions. EPA’s
CAA construction is reflected in interpretive guides EPA has several
times published. Although an interpretation presented in internal
guidance memoranda does not qualify for dispositive force under Chev-
ron U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467 U. S.
837, 865–866, a cogent administrative interpretation nevertheless war-
rants respect, Washington State Dept. of Social and Health Servs. v.
Guardianship Estate of Keffeler, 537 U. S. 371, 385. Pp. 484–488.
(2) ADEC’s several arguments do not persuade the Court to reject
as impermissible EPA’s longstanding, consistently maintained interpre-
tation. ADEC argues that CAA’s BACT definition, § 7479(3), unambig-
uously assigns to “the permitting authority” alone the decision of the
control technology qualifying as “best available.” In ADEC’s view,
EPA’s enforcement role is restricted to assuring that the permit contain
a BACT limitation. CAA entrusts state authorities with initial respon-
sibility to make BACT determinations because they are best positioned
to adjust for local circumstances that might make a technology “unavail-
able” in a particular area. According state authorities initial responsi-
bility, however, does not signify that there can be no unreasonable state
agency BACT determinations. Congress vested EPA with explicit and
sweeping authority to enforce CAA “requirements” relating to the con-
struction and modification of sources under the PSD program, including
BACT. Having expressly endorsed an expansive surveillance role for
EPA in two independent CAA provisions, Congress would not have im-
plicitly precluded EPA from verifying a state authority’s substantive
compliance with the BACT requirement. Nor would Congress have
limited EPA to determining whether the state permitting authority had
uttered the key words “BACT.” The fact that § 7475(a)(8) expressly
requires EPA approval of a State’s BACT determination in a limited
category of cases does not mean EPA lacks supervisory authority in all
other cases. Sections 113(a)(5) and 167 sensibly do not require EPA
approval of all state BACT determinations. Those provisions simply
authorize EPA to act in the unusual case in which a state permit-

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
465 Cite as: 540 U. S. 461 (2004)
Syllabus
ting authority has determined BACT arbitrarily. Also unavailing is
ADEC’s argument that any reasoned justification requirement for a
BACT determination may be enforced only through state administrative
and judicial processes in order to allow development of an adequate
factual record, to ensure EPA carries the burdens of proof, and to pro-
mote certainty. The Court declines to read into CAA’s silence the un-
usual requirement that a federal agency’s decisions enforcing federal
law must be remitted solely to state court. EPA has rationally inter-
preted the BACT provisions and its own §§ 113(a)(5) and 167 enforce-
ment powers not to require recourse to state processes before stopping
a facility’s construction. Nor is the Court persuaded by ADEC’s practi-
cal concerns. There is no reason to conclude that an appropriate record
cannot be developed to allow informed federal-court review when EPA
disputes a BACT decision’s reasonableness. In this very case, the
Ninth Circuit ordered EPA to submit a complete administrative record.
After EPA did so, all the parties agreed to the record’s adequacy. As
to the burdens of production and persuasion, the Court holds that EPA
bears both burdens in a challenge to an EPA stop-construction order
as well as in an EPA-initiated civil action. The underlying question a
reviewing court must answer is the same in either case: Was the BACT
determination unreasonable given the statutory guides and the state
administrative record. Nor does the Court find compelling the sugges-
tion that, if state courts are not the exclusive judicial arbiters, EPA will
be free to invalidate a BACT determination months or years after a
permit issues. This case involves preconstruction orders issued by
EPA, not postconstruction federal directives. EPA itself regards it as
imperative to act on a timely basis. Courts are also less likely to re-
quire new sources to accept more stringent permit conditions the fur-
ther planning and construction have progressed. Pp. 488–495.
(c) In this case, EPA properly exercised its statutory authority under
§§ 113(a)(5) and 167 in finding that ADEC’s acceptance of Low NOx as
BACT for MG–17 lacked evidentiary support. EPA’s orders, therefore,
were neither arbitrary nor capricious. Pp. 496–502.
(1) The Court considers whether EPA’s finding was “arbitrary, ca-
pricious, an abuse of discretion, or otherwise not in accordance with law”
under the applicable review standard set forth in the Administrative
Procedure Act, 5 U. S. C. § 706(2)(A). While EPA’s three skeletal or-
ders were not composed with ideal clarity, they properly ground EPA’s
BACT determination when read together with EPA’s accompanying ex-
planatory correspondence. See Bowman Transp., Inc. v. Arkansas-
Best Freight System, Inc., 419 U. S. 281, 286. As the Ninth Circuit
determined, EPA validly issued stop orders because ADEC’s BACT des-
ignation did not qualify as reasonable in light of statutory guides. In

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
466 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Syllabus
the May 1999 draft permit, ADEC first concluded that SCR was the
most stringent emission-control technology that was both technically
and economically feasible. That technology should have been desig-
nated BACT absent considerations justifying a conclusion that SCR was
not achievable in this case. ADEC, however, selected Low NOx as
BACT based on Cominco’s emissions-offsetting suggestion. In Septem-
ber and December 1999, ADEC again rejected SCR as BACT but no
longer relied on that suggestion. Rather, ADEC candidly stated that
it aimed to support Cominco’s project and its contributions to the region.
ADEC’s selection of Low NOx thus rested squarely and solely on SCR’s
“disproportionate cost.” EPA rightly concluded that ADEC’s switch
from finding SCR economically feasible in May 1999 to finding SCR
economically infeasible in September 1999 had no factual basis in the
record. ADEC forthrightly conceded it was disarmed from reaching a
judgment on SCR’s economic impact on the mine by Cominco’s refusal
to provide relevant financial data. No record evidence suggests that
the mine, were it to use SCR, would be obliged to cut personnel or raise
zinc prices. Having acknowledged that it lacked information needed to
judge SCR’s impact on the mine’s operation, profitability, or competi-
tiveness, ADEC could not simultaneously proffer threats to the mine’s
operation and competitiveness as reasons for declaring SCR economi-
cally infeasible. Nor has ADEC otherwise justified its choice. To bol-
ster its assertion that SCR was too expensive, ADEC invoked cost fig-
ures discussed in four BACT determinations made in regard to diesel
generators used for primary power production. ADEC itself, however,
had previously found SCR’s per-ton cost to be well within what ADEC
and EPA consider economically feasible. No reasoned explanation for
ADEC’s retreat from this position appears in the permit ADEC issued.
ADEC’s basis for selecting Low NOx thus reduces to a readiness to
support Cominco’s project and its contributions to the region. This jus-
tification, however, hardly meets ADEC’s own standard of a source-
specific economic impact that demonstrates SCR to be inappropriate as
BACT. ADEC’s justification that lower aggregate emissions would re-
sult from Cominco’s agreement to install Low NOx on all its generators
is also unpersuasive. The final PSD permit did not offset MG–17’s emis-
sions against those of the mine’s six existing generators. As ADEC
recognized in September and December 1999, a State may treat emis-
sions from several pollutant sources as falling under one “bubble” for
PSD permit purposes only if every pollutant source so aggregated is
part of the permit action. In December 1999, however, only MG–17
figured in the permit action. Pp. 496–501.
(2) This decision does not impede ADEC from revisiting its BACT
determination. In letters and orders throughout the permitting proc-
ess and at oral argument, EPA repeatedly acknowledged that ADEC

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
467 Cite as: 540 U. S. 461 (2004)
Syllabus
may yet prepare an appropriate record supporting its selection of Low
NOx as BACT. There is no reason not to take EPA at its word.
Pp. 501–502.
298 F. 3d 814, affirmed.
Ginsburg, J., delivered the opinion of the Court, in which Stevens,
O’Connor, Souter, and Breyer, JJ., joined. Kennedy, J., filed a dis-
senting opinion, in which Rehnquist, C. J., and Scalia and Thomas, JJ.,
joined, post, p. 502.
Jonathan S. Franklin argued the cause for petitioner.
With him on the briefs were John G. Roberts, Jr., Lorane
F. Hebert, Gregg D. Renkes, Attorney General of Alaska, and
Cameron M. Leonard, Assistant Attorney General. Robert
J. Mahoney, Robert T. Connery, and Marcy G. Glenn filed
briefs in support of petitioner for Teck Cominco Alaska Inc.,
respondent under this Court’s Rule 12.6.
Deputy Solicitor General Hungar argued the cause for
respondents. With him on the brief were Solicitor General
Olson, Acting Assistant Attorney General Johnson, Deputy
Solicitor General Kneedler, James A. Feldman, Andrew
J. Doyle, Robert E. Fabricant, Carol S. Holmes, and Juliane
R. B. Matthews.*
*Briefs of amici curiae urging reversal were filed for the State of North
Dakota et al. by Wayne Stenehjem, Attorney General of North Dakota,
Lyle Witham, Assistant Attorney General, Patrick J. Crank, Attorney
General of Wyoming, and Theodore C. Preston, Assistant Attorney Gen-
eral, and by the Attorneys General for their respective States as follows:
William H. Pryor, Jr., of Alabama, M. Jane Brady of Delaware, Thomas
J. Miller of Iowa, Jon Bruning of Nebraska, Brian Sandoval of Nevada,
W. A. Drew Edmondson of Oklahoma, Larry Long of South Dakota, Mark
L. Shurtleff of Utah, and Jerry W. Kilgore of Virginia; for NANA Re-
gional Corp., Inc., by James E. Torgerson and Matthew Cohen; for the
National Environmental Development Association et al. by Janet Pitterle
Holt; and for the Pacific Legal Foundation by M. Reed Hopper and Robin
L. Rivett.
Briefs of amici curiae urging affirmance were filed for the State of
Vermont et al. by William H. Sorrell, Attorney General of Vermont, and
Kevin O. Leske and Erick Titrud, Assistant Attorneys General, and by
the Attorneys General for their respective States as follows: Bill Lockyer

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
468 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
Justice Ginsburg delivered the opinion of the Court.
This case concerns the authority of the Environmental
Protection Agency (EPA or Agency) to enforce the provi-
sions of the Clean Air Act’s (CAA or Act) Prevention of Sig-
nificant Deterioration (PSD) program. Under that program,
no major air pollutant emitting facility may be constructed
unless the facility is equipped with “the best available con-
trol technology” (BACT). As added by § 165, 91 Stat. 735,
and amended, 42 U. S. C. § 7475(a)(4). BACT, as defined in
the CAA, means, for any major air pollutant emitting facility,
“an emission limitation based on the maximum degree of
[pollutant] reduction . . . which the permitting authority, on
a case-by-case basis, taking into account energy, environmen-
tal, and economic impacts and other costs, determines is
achievable for [the] facility. . . .” § 7479(3).
Regarding EPA oversight, the Act includes a general in-
struction and one geared specifically to the PSD program.
The general prescription, § 113(a)(5) of the Act, authorizes
EPA, when it finds that a State is not complying with a CAA
requirement governing construction of a pollutant source,
to issue an order prohibiting construction, to prescribe an
administrative penalty, or to commence a civil action for in-
junctive relief. 42 U. S. C. § 7413(a). Directed specifically
to the PSD program, CAA § 167 instructs EPA to “take
such measures, including issuance of an order, or seeking in-
of California, Richard Blumenthal of Connecticut, G. Steven Rowe of
Maine, Thomas F. Reilly of Massachusetts, Michael A. Cox of Michigan,
Peter W. Heed of New Hampshire, Peter C. Harvey of New Jersey, Eliot
Spitzer of New York, Hardy Myers of Oregon, Patrick C. Lynch of Rhode
Island, and Peggy A. Lautenschlager of Wisconsin; for Environmental De-
fense et al. by Sean H. Donahue; and for the Native Village of Kivalina,
Alaska, by Michael J. Frank and Peter Van Tuyn.
Briefs of amici curiae were filed for the Center for Energy and Eco-
nomic Development by Paul M. Seby; and for the Northwest Environmen-
tal Defense Center by Donald B. Potter.

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
469 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
junctive relief, as necessary to prevent the construction” of
a major pollutant emitting facility that does not conform to
the PSD requirements of the Act. 42 U. S. C. § 7477.
In the case before us, “the permitting authority” under
§ 7479(3) is the State of Alaska, acting through Alaska’s
Department of Environmental Conservation (ADEC). The
question presented is what role EPA has with respect to
ADEC’s BACT determinations. Specifically, may EPA act
to block construction of a new major pollutant emitting fa-
cility permitted by ADEC when EPA finds ADEC’s BACT
determination unreasonable in light of the guides § 7479(3)
prescribes? We hold that the Act confers that checking au-
thority on EPA.
I
A
Congress enacted the Clean Air Amendments of 1970, 84
Stat. 1676, 42 U. S. C. § 7401 et seq., in response to “dissatis-
faction with the progress of existing air pollution programs.”
Union Elec. Co. v. EPA, 427 U. S. 246, 249 (1976). The
amendments aimed “to guarantee the prompt attainment
and maintenance of specified air quality standards.” Ibid.;
D. Currie, Air Pollution § 1.13, p. 1–16 (1981) (summary
of 1970 amendments). Added by the 1970 amendments,
§§ 108(a) and 109(a) of the Act require EPA to publish lists
of emissions that “cause or contribute to air pollution which
may reasonably be anticipated to endanger public health or
welfare,” and to promulgate primary and secondary national
ambient air quality standards (NAAQS) for such pollut-
ants. 42 U. S. C. §§ 7408(a) and 7409(a); Whitman v. Amer-
ican Trucking Assns., Inc., 531 U. S. 457, 462–463 (2001).
NAAQS “define [the] levels of air quality that must be
achieved to protect public health and welfare.” R. Bel-
den, Clean Air Act 6 (2001). The Agency published initial
NAAQS in 1971, Union Elec., 427 U. S., at 251 (citing 40

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
470 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
CFR pt. 50 (1975)), and in 1985, NAAQS for the pollutant at
issue in this case, nitrogen dioxide. 40 CFR § 50.11 (2002).1
Under § 110 of the Act, also added in 1970, each State must
submit for EPA approval “a plan which provides for imple-
mentation, maintenance, and enforcement of [NAAQS].” 42
U. S. C. § 7410(a)(1); cf. § 7410(c)(1) (EPA shall promulgate an
implementation plan if the State’s plan is inadequate). Rel-
evant to this case, EPA has approved Alaska’s implementa-
tion plan. 48 Fed. Reg. 30626 (1983), as amended, 56 Fed.
Reg. 19288 (1991); 40 CFR § 52.96(a) (2002). To gain EPA
approval, a “state implementation plan” (SIP) must “include
enforceable emission limitations and other control measures,
means, or techniques . . . as may be necessary or appropriate
to meet the applicable [CAA] requirements.” 42 U. S. C.
§ 7410(a)(2)(A). While States have “wide discretion” in for-
mulating their plans, Union Elec., 427 U. S., at 250, SIPs
must include certain measures Congress specified “to assure
that national ambient air quality standards are achieved,” 42
U. S. C. § 7410(a)(2)(C). Among those measures are permit
provisions, § 7475, basic to the administration of the program
involved in this case, CAA’s “Prevention of Significant Dete-
rioration of Air Quality” (PSD) program.
The PSD requirements, enacted as part of 1977 amend-
ments to the Act, Title I, § 160 et seq., 91 Stat. 731, “are
designed to ensure that the air quality in attainment areas
or areas that are already ‘clean’ will not degrade,” Belden,
supra, at 43. See 42 U. S. C. § 7470(1) (purpose of PSD pro-
1 Emissions levels for nitrogen dioxide, a regulated pollutant under the
Act, are defined in terms of quantities of all oxides of nitrogen. R. Bel-
den, Clean Air Act 47, n. 11 (2001). “The term nitrogen oxides refers to
a family of compounds of nitrogen and oxygen. The principal nitrogen
oxides component present in the atmosphere at any time is nitrogen diox-
ides. Combustion sources emit mostly nitric oxide, with some nitrogen
dioxide. Upon entering the atmosphere, the nitric oxide changes rapidly,
mostly to nitrogen dioxide.” EPA, Prevention of Significant Deteriora-
tion for Nitrogen Oxides, 53 Fed. Reg. 40656 (1988). Nitrogen oxides are
also termed “NOx.”

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
471 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
gram is to “protect public health and welfare from any actual
or potential adverse effect which in [EPA’s] judgment may
reasonably be anticipate[d] to occur from air pollution . . .
notwithstanding attainment and maintenance of all national
ambient air quality standards”). Before 1977, no CAA pro-
vision specifically addressed potential air quality deterior-
ation in areas where pollutant levels were lower than the
NAAQS. Alabama Power Co. v. Costle, 636 F. 2d 323, 346–
347 (CADC 1979). Responding to litigation initiated by an
environmental group,2 however, EPA issued regulations in
1974 requiring that SIPs include a PSD program. Id., at
347, and n. 18 (citing 39 Fed. Reg. 42510 (1974)). Three
years later, Congress adopted the current PSD program.
See S. Rep. No. 95–127, p. 11 (1977) (Congress itself has
“a responsibility to delineate a policy for protecting clean
air”).
The PSD program imposes on States a regime governing
areas “designated pursuant to [42 U. S. C. § 7407] as attain-
ment or unclassifiable.” § 7471.3 An attainment area is one
in which the air “meets the national primary or secondary
ambient air quality standard for [a regulated pollutant].”
§ 7407(d)(1)(A)(ii). Air in an unclassifiable area “cannot be
classified on the basis of available information as meeting or
not meeting the national primary or secondary ambient air
quality standard for the pollutant.” § 7407(d)(1)(A)(iii).
Northwest Alaska, the region this case concerns, is classified
as an attainment or unclassifiable area for nitrogen dioxide,
40 CFR § 81.302 (2002); therefore, the PSD program applies
to emissions of that pollutant in the region. In 2002, the
Agency reported that “[a]ll areas of the country that once
2 Sierra Club v. Ruckelshaus, 344 F. Supp. 253 (DC 1972), aff ’d per cu-
riam, 4 E. R. C. 1815, 2 Env. L. Rep. 20656 (CADC 1972), aff ’d by an
equally divided court sub nom. Fri v. Sierra Club, 412 U. S. 541 (1973)
(per curiam).
3 The PSD program also requires visibility control measures, 42 U. S. C.
§§ 7491–7492, not at issue in this case.

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
472 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
violated the NAAQS for [nitrogen dioxide] now meet that
standard.” EPA, Latest Findings on National Air Quality
7 (Aug. 2003).
Section 165 of the Act, 42 U. S. C. § 7475, installs a permit-
ting requirement for any “major emitting facility,” defined to
include any source emitting more than 250 tons of nitrogen
oxides per year, § 7479(1). No such facility may be con-
structed or modified unless a permit prescribing emission
limitations has been issued for the facility. § 7475(a)(1); see
§ 7479(2)(C) (defining “construction” to include “modifica-
tion”). Alaska’s SIP imposes an analogous requirement.
18 Alaska Admin. Code § 50.300(c)(1) (2003). Modifications
to major emitting facilities that increase nitrogen oxide emis-
sions in excess of 40 tons per year require a PSD permit.
40 CFR § 51.166(b)(23)(i) (2002); 18 Alaska Admin. Code
§ 50.300(h)(3)(B)(ii) (2003).
The Act sets out preconditions for the issuance of PSD
permits. Inter alia, no PSD permit may issue unless “the
proposed facility is subject to the best available control tech-
nology for each pollutant subject to [CAA] regulation . . .
emitted from . . . [the] facility.” 42 U. S. C. § 7475(a)(4). As
described in the Act’s definitional provisions, “best available
control technology” (BACT) means:
“an emission limitation based on the maximum degree
of reduction of each pollutant subject to regulation
under this chapter emitted from or which results from
any major emitting facility, which the permitting author-
ity, on a case-by-case basis, taking into account energy,
environmental, and economic impacts and other costs,
determines is achievable for such facility through appli-
cation of production processes and available methods,
systems, and techniques . . . . In no event shall applica-
tion of ‘best available control technology’ result in emis-
sions of any pollutants which will exceed the emissions
allowed by any applicable standard established pursuant

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
473 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
to section 7411 or 7412 of this title [emission standards
for new and existing stationary sources].” § 7479(3).
40 CFR § 51.166(b)(12) (2002) (repeating statutory defini-
tion). Alaska’s SIP contains provisions that track the statu-
tory BACT requirement and definition. 18 Alaska Admin.
Code §§ 50.310(d)(3) and 50.990(13) (2003). The State, with
slightly variant terminology, defines BACT as “the emission
limitation that represents the maximum reduction achiev-
able for each regulated air contaminant, taking into account
energy, environmental and economic impacts, and other
costs.” § 50.990(13). Under the federal Act, a limited class
of sources must gain advance EPA approval for the BACT
prescribed in the permit. 42 U. S. C. § 7475(a)(8).
CAA also provides that a PSD permit may issue only if
a source “will not cause, or contribute to, air pollution in
excess of any . . . maximum allowable increase or maximum
allowable concentration for any pollutant” or any NAAQS.
§ 7475(a)(3). Congress left to the Agency the determination
of most maximum allowable increases, or “increments,” in
pollutants. EPA regulations have defined increments for
nitrogen oxides. 40 CFR § 51.166(c) (2002). Typically, to
demonstrate that increments will not be exceeded, applicants
use mathematical models of pollutant plumes, their behavior,
and their dispersion. Westbrook, Air Dispersion Models:
Tools to Assess Impacts from Pollution Sources, 13 Natural
Resources & Env. 546, 547–548 (1999).
Among measures EPA may take to ensure compliance
with the PSD program, two have special relevance here.
The first prescription, § 113(a)(5) of the Act, provides that
“[w]henever, on the basis of any available information, [EPA]
finds that a State is not acting in compliance with any
requirement or prohibition of the chapter relating to the
construction of new sources or the modification of existing
sources,” 42 U. S. C. § 7413(a)(5), EPA may “issue an order
prohibiting the construction or modification of any major sta-
tionary source in any area to which such requirement ap-

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
474 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
plies,” § 7413(a)(5)(A).4 The second measure, § 167 of the
Act, trains on enforcement of the PSD program; it requires
EPA to “take such measures, including issuance of an order,
or seeking injunctive relief, as necessary to prevent the con-
struction or modification of a major emitting facility which
does not conform to the [PSD] requirements.” § 7477.
B
Teck Cominco Alaska Inc. (Cominco) operates a zinc con-
centrate mine, the Red Dog Mine, in northwest Alaska ap-
proximately 100 miles north of the Arctic Circle and close to
the native Alaskan villages of Kivalina and Noatak. App. to
Pet. for Cert. 3a; Brief for Petitioner 8; Brief for Respond-
ents 4. The mine is the region’s largest private employer.
Brief for Petitioner 9. It supplies a quarter of the area’s
wage base. Ibid. Cominco leases the land from the NANA
Regional Corporation, an Alaskan corporation formed pursu-
ant to the Alaska Native Claims Settlement Act, 85 Stat.
688, as amended, 43 U. S. C. § 1601 et seq. Brief for NANA
Regional Corporation, Inc., as Amicus Curiae 1–2, 4.
In 1988, Cominco obtained authorization to operate the
mine, a “major emitting facility” under the Act and Alaska’s
SIP. App. 106. The mine’s PSD permit authorized five
5,000 kilowatt Wartsila diesel electric generators, MG–1
through MG–5, subject to operating restrictions; two of the
five generators were permitted to operate only in standby
status. Ibid. Petitioner Alaska Department of Environ-
mental Conservation (ADEC) issued a second PSD permit in
1994 allowing addition of a sixth full-time generator (MG–6),
removing standby status from MG–2, and imposing a new
4 As enacted in 1977, § 113(a)(5) extended only to solid waste combustion
and sources in nonattainment areas. See Title I, § 111(a), 91 Stat. 685.
Congress extended § 113(a)(5) in 1990 amendments to the Act to cover
attainment areas, and thus to encompass enforcement of PSD permitting
requirements. Title VII, 104 Stat. 2672.

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
475 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
operational cap that allowed all but one generator to run full
time. Ibid.
In 1996, Cominco initiated a project, with funding from the
State, to expand zinc production by 40%. Brief for Peti-
tioner 10; Reply Brief for Petitioner 11, n. 9. Anticipating
that the project would increase nitrogen oxide emissions
by more than 40 tons per year, see supra, at 472, Cominco
applied to ADEC for a PSD permit to allow, inter alia,
increased electricity generation by its standby generator,
MG–5. App. 107–108; App. to Pet. for Cert. 33a. On March
3, 1999, ADEC preliminarily proposed as BACT for MG–5
the emission control technology known as selective catalytic
reduction (SCR),5 which reduces nitrogen oxide emissions by
90%. App. 72, 108. In response, Cominco amended its ap-
plication to add a seventh generator, MG–17, and to propose
as BACT an alternative control technology—Low NOx 6 —
that achieves a 30% reduction in nitrogen oxide pollutants.
Brief for Respondents 5, and n. 1; App. 84.
On May 4, 1999, ADEC, in conjunction with Cominco’s rep-
resentative, issued a first draft PSD permit and preliminary
technical analysis report that concluded Low NOx was
BACT for MG–5 and MG–17. Id., at 55–95. To determine
BACT, ADEC employed EPA’s recommended top-down
methodology, id., at 61:
“In brief, the top-down process provides that all avail-
able control technologies be ranked in descending order
of control effectiveness. The PSD applicant first exam-
ines the most stringent—or ‘top’—alternative. That al-
5 SCR requires injections of “ammonia or urea into the exhaust before
the exhaust enters a catalyst bed made with vanadium, titanium, or plati-
num. The reduction reaction occurs when the flue gas passes over the
catalyst bed where the NOx and ammonia combine to become nitrogen,
oxygen, and water . . . .” App. 71.
6 In Low NOx, changes are made to a generator to improve fuel atomiza-
tion and modify the combustion space to enhance the mixing of air and
fuel. Id., at 75.

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
476 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
ternative is established as BACT unless the applicant
demonstrates, and the permitting authority in its in-
formed judgment agrees, that technical considerations,
or energy, environmental, or economic impacts justify
a conclusion that the most stringent technology is not
‘achievable’ in that case. If the most stringent technol-
ogy is eliminated in this fashion, then the next most
stringent alternative is considered, and so on.” EPA,
New Source Review Workshop Manual B.2 (Draft Oct.
1990) (hereinafter New Source Review Manual); App.
61–62.7
Applying top-down methodology, ADEC first homed in on
SCR as BACT for MG–5, and the new generator, MG–17.
“[W]ith an estimated reduction of 90%,” ADEC stated, SCR
“is the most stringent” technology. Id., at 79. Finding
SCR “technically and economically feasible,” id., at 65,
ADEC characterized as “overstated” Cominco’s cost esti-
mate of $5,643 per ton of nitrogen oxide removed by SCR,
id., at 113. Using Cominco’s data, ADEC reached a cost
estimate running between $1,586 and $2,279 per ton. Id.,
at 83. Costs in that range, ADEC observed, “are well
within what ADEC and EPA conside[r] economically feasi-
ble.” Id., at 84. Responding to Cominco’s comments on the
preliminary permit, engineering staff in ADEC’s Air Per-
mits Program pointed out that, according to information
Cominco provided to ADEC, “SCR has been installed on sim-
ilar diesel-fired engines throughout the world.” Id., at 102.
Despite its staff ’s clear view “that SCR (the most effective
individual technology) [was] technologically, environmentally,
and economically feasible for the Red Dog power plant en-
gines,” id., at 103–104, ADEC endorsed the alternative prof-
7 Nothing in the Act or its implementing regulations mandates top-down
analysis. See 42 U. S. C. § 7479(3); 40 CFR § 52.21( j) (2002). EPA repre-
sents that permitting authorities “commonly” use top-down methodology.
Brief for Respondents 3.

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
477 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
fered by Cominco. To achieve nitrogen oxide emission re-
ductions commensurate with SCR’s 90% impact, Cominco
proposed fitting the new generator MG–17 and the six exist-
ing generators with Low NOx. Ibid.8 Cominco asserted
that it could lower net emissions by 396 tons per year if it
fitted all seven generators with Low NOx rather than fitting
two (MG–5 and MG–17) with SCR and choosing one of them
as the standby unit. Id., at 87. Cominco’s proposal hinged
on the “assumption . . . that under typical operating condi-
tions one or more engines will not be running due to mainte-
nance of standby-generation capacity.” Ibid. If all seven
generators ran continuously, however, Cominco’s alternative
would increase emissions by 79 tons per year. Ibid. Ac-
cepting Cominco’s submission, ADEC stated that Cominco’s
Low NOx solution “achieve[d] a similar maximum NOx re-
duction as the most stringent controls; [could] potentially
result in a greater NOx reduction; and is logistically and eco-
nomically less onerous to Cominco.” Id., at 87–88.
On the final day of the public comment period, June 2,
1999, the United States Department of the Interior, National
Parks Service (NPS), submitted comments to ADEC. App.
to Pet. for Cert. 33a; App. 97, 108. NPS objected to the
projected offset of new emissions from MG–5 and MG–17
against emissions from other existing generators that were
not subject to BACT. Letter from John Notar, NPS Air
Resources Division, to Jim Baumgartner, ADEC (June 2,
1999). Such an offset, NPS commented, “is neither allowed
by BACT, nor achieves the degree of reduction that would
result if all the generators that are subject to BACT were
equipped with SCR.” Id., at 3. NPS further observed that
the proposed production-increase project would remove
operating restrictions that the 1994 PSD permit had placed
on four of the existing generators—MG–1, MG–3, MG–4,
8 Two generators already were fitted with a technology called Fuel In-
jection Timing Retard that results in a 20% to 30% reduction in nitrogen
oxide emissions. App. 75–76, 86.

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
478 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
and MG–5. App. to Pet. for Cert. 34a. Due to that altera-
tion, NPS urged, those generators, too, became part of the
production-expansion project and would be subject to the
BACT requirement. Ibid.
Following NPS’ lead, EPA wrote to ADEC on July 29,
1999, commenting: “Although ADEC states in its analysis
that [SCR], the most stringent level of control, is economi-
cally and technologically feasible, ADEC did not propose to
require SCR. . . . [O]nce it is determined that an emission
unit is subject to BACT, the PSD program does not allow
the imposition of a limit that is less stringent than BACT.”
App. 96–97. A permitting authority, EPA agreed with NPS,
could not offset new emissions “by imposing new controls on
other emission units” that were not subject to BACT. Id.,
at 97. New emissions could be offset only against reduced
emissions from sources covered by the same BACT authori-
zation. Id., at 285–286. EPA further agreed with NPS
that, based on the existing information, BACT would be re-
quired for MG–1, MG–3, MG–4, and MG–5. Id., at 97.
After receiving EPA comments, ADEC issued a second
draft PSD permit and technical analysis report on Septem-
ber 1, 1999, again finding Low NOx to be BACT for MG–17.
Id., at 105–117. Abandoning the emissions-offsetting justi-
fication advanced in the May 4 draft permit, ADEC agreed
with NPS and EPA that “emission reductions from sources
that were not part of the permit action,” here MG–1, MG–2,
MG–3, MG–4, MG–5, and MG–6, could not be considered
in determining BACT for MG–17. Id., at 111; id., at 199
(same).9
9 Rather than subject MG–1, MG–3, MG–4, and MG–5 to BACT, ADEC
and Cominco “agreed to permit conditions that would require low NOx
controls on MG–1, MG–3, MG–4, and MG–5, and emission limits that reflect
the previous ‘bubbled’ limits. Under this approach, the permit would re-
sult in no increase in actual or allowable emissions from any of these en-
gines and the installation of BACT would not be necessary for these four

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
479 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
ADEC conceded that, lacking data from Cominco, it had
made “no judgment . . . as to the impact of . . . [SCR] on the
operation, profitability, and competitiveness of the Red Dog
Mine.” Id., at 116. Contradicting its May 1999 conclusion
that SCR was “technically and economically feasible,” see
supra, at 476, ADEC found in September 1999 that SCR im-
posed “a disproportionate cost” on the mine. App. 116.
ADEC concluded, on a “cursory review,” that requiring SCR
for a rural Alaska utility would lead to a 20% price increase,
and that in comparison with other BACT technologies, SCR
came at a “significantly higher” cost. Ibid. No economic
basis for a comparison between the mine and a rural utility
appeared in ADEC’s technical analysis.
EPA protested the revised permit. In a September 15,
1999, letter, the Agency stated: “Cominco has not adequately
demonstrated any site-specific factors to support their claim
that the installation of [SCR] is economically infeasible at
the Red Dog Mine. Therefore, elimination of SCR as BACT
based on cost-effectiveness grounds is not supported by the
record and is clearly erroneous.” Id., at 127; see id., at
138 (ADEC’s record does not support the departure from
ADEC’s initial view that the costs for SCR were economi-
cally feasible).
To justify the September 1, 1999, permit, EPA suggested,
ADEC could “include an analysis of whether requiring Com-
inco to install and operate [SCR] would have any adverse
economic impacts upon Cominco specifically.” Id., at 127.
Stating that such an inquiry was unnecessary and expressing
“concerns related to confidentiality,” Cominco declined to
submit financial data. Id., at 134. In this regard, Cominco
simply asserted, without detail, that the company’s “overall
debt remains quite high” despite continuing profits. Id., at
units.” Id., at 149. EPA found no cause to question this ADEC-Cominco
agreement. Ibid.

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
480 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
134–135. Cominco also invoked the need for “[i]ndustrial
development in rural Alaska.” Id., at 135.
On December 10, 1999, ADEC issued the final permit and
technical analysis report. Once again, ADEC approved
Low NOx as BACT for MG–17 “[t]o support Cominco’s Red
Dog Mine Production Rate Increase Project, and its contri-
butions to the region.” Id., at 208. ADEC did not include
the economic analysis EPA had suggested. Id., at 152–246.
Indeed, ADEC conceded again that it had made “no judg-
ment . . . as to the impact of . . . [SCR’s] cost on the operation,
profitability, and competitiveness of the Red Dog Mine.”
Id., at 207. Nonetheless, ADEC advanced, as cause for
its decision, SCR’s adverse effect on the mine’s “unique and
continuing impact on the economic diversity of th[e] region”
and on the venture’s “world competitiveness.” Id., at 208.
ADEC did not explain how its inferences of adverse effects
on the region’s economy or the mine’s “world competitive-
ness” could be made without financial information showing
SCR’s impact on the “operation, profitability, and competi-
tiveness” of the mine. Id., at 207, 299. Instead, ADEC re-
iterated its rural Alaska utility analogy, and again compared
SCR’s cost to the costs of other, less stringent, control tech-
nologies. Id., at 205–207.
The same day, December 10, 1999, EPA issued an order
to ADEC, under §§ 113(a)(5) and 167 of the Act, 42 U. S. C.
§§ 7413(a)(5) and 7477, prohibiting ADEC from issuing a PSD
permit to Cominco “unless ADEC satisfactorily documents
why SCR is not BACT for the Wartsila diesel generator
[MG–17].” App. to Pet. for Cert. 36a. In the letter accom-
panying the order, the Agency stated that “ADEC’s own
analysis supports the determination that BACT is [SCR], and
that ADEC’s decision in the proposed permit therefore is
both arbitrary and erroneous.” App. 149.
On February 8, 2000, EPA, again invoking its authority
under §§ 113(a)(5) and 167 of the Act, issued a second order,

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
481 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
this time prohibiting Cominco from beginning “construction
or modification activities at the Red Dog mine.” App. to
Pet. for Cert. 49a. A third order, issued on March 7, 2000,
superseding and vacating the February 8 order, generally
prohibited Cominco from acting on ADEC’s December 10
PSD permit but allowed limited summer construction. Id.,
at 62a–64a. On April 25, 2000, EPA withdrew its December
10 order. App. 300; App. to Pet. for Cert. 6a. Once ADEC
issued the permit, EPA explained, that order lacked utility.
On July 16, 2003, ADEC granted Cominco a PSD permit to
construct MG–17 with SCR as BACT. Letter from Theo-
dore B. Olson, Solicitor General, to William K. Suter, Clerk
of the Court (Aug. 21, 2003). Under the July 16, 2003, per-
mit, SCR ceases to be BACT “if and when the case currently
pending before the Supreme Court of the United States of
America is decided in favor of the State of Alaska.” ADEC,
Air Quality Control Construction Permit, Final Technical
Analysis Report, Permit No. 9932–AC005, Revision 2, p. 7.
The day EPA issued its first order against Cominco, Feb-
ruary 8, 2000, ADEC and Cominco petitioned the Court of
Appeals for the Ninth Circuit for review of EPA’s orders.
App. 11. The Agency initially moved to dismiss, urging
that the Court of Appeals lacked subject-matter jurisdiction.
In an order released March 27, 2001, the Ninth Circuit
concluded that it had adjudicatory authority pursuant to
42 U. S. C. § 7607(b)(1), which lodges jurisdiction over chal-
lenges to “any . . . final [EPA] action” in the Courts of
Appeals. Alaska v. United States EPA, 244 F. 3d 748,
750–751.10
The Court of Appeals resolved the merits in a judgment
released July 30, 2002. 298 F. 3d 814 (CA9). It held that
10 At oral argument, counsel for EPA confirmed that the Agency no
longer questions the Court of Appeals’ adjudicatory authority, satisfied
that the finality requirement was met because the stop-construction order
imposed “new legal obligations on Cominco.” Tr. of Oral Arg. 43–44
(punctuation omitted).

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
482 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
EPA had authority under §§ 113(a)(5) and 167 to issue the
contested orders, and that the Agency had properly exer-
cised its discretion in doing so. Id., at 820–823. Concern-
ing EPA’s authority under §§ 113(a)(5) and 167, the Court of
Appeals observed first that “the question presented is what
requirements the state must meet” under the Act to issue a
PSD permit, not what the correct BACT might be. Id., at
821 (emphasis in original). Concluding that EPA had “au-
thority to determine the reasonableness or adequacy of the
state’s justification for its decision,” the Court of Appeals
emphasized that the “provision of a reasoned justification”
by a permitting authority is undeniably a “requirement” of
the Act. Ibid. EPA had properly exercised its discretion
in issuing the three orders, the Ninth Circuit ultimately de-
termined, because (1) Cominco failed to “demonstrat[e] that
SCR was economically infeasible,” and (2) “ADEC failed to
provide a reasoned justification for its elimination of SCR as
a control option.” Id., at 823. We granted certiorari, 537
U. S. 1186 (2003), to resolve an important question of federal
law, i. e., the scope of EPA’s authority under §§ 113(a)(5) and
167, and now affirm the Ninth Circuit’s judgment.
II
ADEC contested EPA’s orders under 42 U. S. C. § 7607
(b)(1), which renders reviewable in the appropriate federal
court of appeals any EPA “final action.” Before the Ninth
Circuit, EPA unsuccessfully urged that its orders were “in-
terlocutory,” and therefore unreviewable in court unless and
until EPA chose to commence an enforcement action.11 A
preenforcement contest could be maintained in the Court
of Appeals under § 7607(b)(1), the Ninth Circuit held, for in
the circumstances presented, EPA’s actions had the requi-
site finality.
11 Such an action would lie in district court, under 42 U. S. C. § 7413(b).

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
483 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
It was undisputed, the Court of Appeals observed, that
EPA had spoken its “ ‘last word’ ” on whether ADEC had
adequately justified its conclusion that Low NOx was the
best available control technology for the MG–17 generator.
244 F. 3d, at 750. Further, EPA’s orders effectively halted
construction of the MG–17 generator, for Cominco would
risk civil and criminal penalties if it defied a valid EPA
directive.
In this Court, EPA agrees with the Ninth Circuit’s finality
determination. See Brief for Respondents 16–20; Tr. of Oral
Arg. 43–44. We are satisfied that the Court of Appeals cor-
rectly applied the guides we set out in Bennett v. Spear, 520
U. S. 154, 177–178 (1997) (to be “final,” agency action must
“mark the ‘consummation’ of the agency’s decisionmaking
process,” and must either determine “rights or obligations”
or occasion “legal consequences” (some internal quotation
marks omitted)). As the Court of Appeals stated, EPA had
“asserted its final position on the factual circumstances” un-
derpinning the Agency’s orders, 244 F. 3d, at 750, and if
EPA’s orders survived judicial review, Cominco could not es-
cape the practical and legal consequences (lost costs and vul-
nerability to penalties) of any ADEC-permitted construction
Cominco endeavored, ibid.
No question has been raised here, we note, about the ade-
quacy of EPA’s preorder procedures under the Due Process
Clause or the Administrative Procedure Act. Cf. Vermont
Yankee Nuclear Power Corp. v. Natural Resources Defense
Council, Inc., 435 U. S. 519, 544 (1978) (agencies have author-
ity to “fashion their own rules of procedure,” even when a
statute does not specify what process to use). Furthermore,
in response to ADEC’s initial contention that the record was
incomplete, the Ninth Circuit gave EPA an opportunity to
supplement the record, and thereafter obtained from all par-
ties agreement “that the record as it stood was adequate to
resolve [ADEC’s review petition].” 298 F. 3d, at 818.

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
484 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
III
A
Centrally at issue in this case is the question whether
EPA’s oversight role, described by Congress in CAA
§§ 113(a)(5) and 167, see supra, at 473–474, extends to ensur-
ing that a state permitting authority’s BACT determination
is reasonable in light of the statutory guides. Sections
113(a)(5) and 167 lodge in the Agency encompassing supervi-
sory responsibility over the construction and modification of
pollutant emitting facilities in areas covered by the PSD pro-
gram. 42 U. S. C. §§ 7413(a)(5) and 7477. In notably capa-
cious terms, Congress armed EPA with authority to issue
orders stopping construction when “a State is not acting in
compliance with any [CAA] requirement or prohibition . . .
relating to the construction of new sources or the modifica-
tion of existing sources,” § 7413(a)(5), or when “construction
or modification of a major emitting facility . . . does not con-
form to the requirements of [the PSD program],” § 7477.
The federal Act enumerates several “[p]reconstruction re-
quirements” for the PSD program. § 7475. Absent these,
“[n]o major emitting facility . . . may be constructed.” Ibid.
One express preconstruction requirement is inclusion of a
BACT determination in a facility’s PSD permit. §§ 7475(a)
(1) and (4). As earlier set out, see supra, at 472, the Act
defines BACT as “an emission limitation based on the max-
imum degree of reduction of [a] pollutant . . . which the
permitting authority, on a case-by-case basis, taking into
account energy, environmental, and economic impacts and
other costs, determines is achievable for [a] facility. ”
§ 7479(3). Under this formulation, the permitting author-
ity, ADEC here, exercises primary or initial responsibility
for identifying BACT in line with the Act’s definition of
that term.
All parties agree that one of the “many requirements in
the PSD provisions that the EPA may enforce” is “that a

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
485 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
[PSD] permit contain a BACT limitation.” Brief for Peti-
tioner 34; see id., at 22, 25 (same). See also Brief for Re-
spondents 23. It is therefore undisputed that the Agency
may issue an order to stop a facility’s construction if a PSD
permit contains no BACT designation.
EPA reads the Act’s definition of BACT, together with
CAA’s explicit listing of BACT as a “[p]reconstruction re-
quiremen[t],” to mandate not simply a BACT designation,
but a determination of BACT faithful to the statute’s defini-
tion. In keeping with the broad oversight role §§ 113(a)(5)
and 167 vest in EPA, the Agency maintains, it may review
permits to ensure that a State’s BACT determination is rea-
sonably moored to the Act’s provisions. See id., at 24. We
hold, as elaborated below, that the Agency has rationally con-
strued the Act’s text and that EPA’s construction warrants
our respect and approbation.
BACT’s statutory definition requires selection of an emis-
sion control technology that results in the “maximum” reduc-
tion of a pollutant “achievable for [a] facility” in view of “en-
ergy, environmental, and economic impacts and other costs.”
42 U. S. C. § 7479(3). This instruction, EPA submits, cabins
state permitting authorities’ discretion by granting only “au-
thority to make reasonable BACT determinations,” Brief for
Respondents 27 (emphasis in original), i. e., decisions made
with fidelity to the Act’s purpose “to insure that economic
growth will occur in a manner consistent with the preserva-
tion of existing clean air resources,” 42 U. S. C. § 7470(3).
Noting that state permitting authorities’ statutory discretion
is constrained by CAA’s strong, normative terms “maxi-
mum” and “achievable,” § 7479(3),12 EPA reads §§ 113(a)(5)
12 Formulations similar to the BACT definition’s “maximum degree of
[pollutant] reduction . . . achievable” appear in the Act’s standards for
new sources in nonattainment areas, 42 U. S. C. §§ 7501(3) and 7503(a)(2)
(“lowest achievable emission rate” (internal quotation marks omitted)),
and its technology-based standard for hazardous emissions, § 7412(d)(2)
(“maximum degree of reduction . . . achievable”).

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
486 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
and 167 to empower the federal Agency to check a state
agency’s unreasonably lax BACT designation. See Brief
for Respondents 27.
EPA stresses Congress’ reason for enacting the PSD pro-
gram—to prevent significant deterioration of air quality in
clean-air areas within a State and in neighboring States.
§§ 7470(3), (4); see id., at 33. That aim, EPA urges, is un-
likely to be realized absent an EPA surveillance role that
extends to BACT determinations. The Agency notes in this
regard a House Report observation:
“Without national guidelines for the prevention of sig-
nificant deterioration a State deciding to protect its
clean air resources will face a double threat. The pros-
pect is very real that such a State would lose existing
industrial plants to more permissive States. But ad-
ditionally the State will likely become the target of
‘economic-environmental blackmail’ from new industrial
plants that will play one State off against another with
threats to locate in whichever State adopts the most
permissive pollution controls.” H. R. Rep. No. 95–294,
p. 134 (1977).
The House Report further observed that “a community that
sets and enforces strict standards may still find its air pol-
luted from sources in another community or another State.”
Id., at 135 (quoting 116 Cong. Rec. 32909 (1970)). Federal
Agency surveillance of a State’s BACT designation is
needed, EPA asserts, to restrain the interjurisdictional pres-
sures to which Congress was alert. See Brief for Respond-
ents 33–34, 43; Brief for Vermont et al. as Amici Curiae
12 (“If EPA has authority to ensure a reasonable level of
consistency among BACT determinations nationwide, then
every State can feel more confident about maintaining strin-
gent standards without fear of losing its current industry or
alienating prospective industry.”).

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
487 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
The CAA construction EPA advances in this litigation is
reflected in interpretive guides the Agency has several times
published. See App. 268–269 (1983 EPA PSD guidance
memorandum noting the Agency’s “oversight function”); id.,
at 274 (1988 EPA guidance memorandum stating EPA may
find a BACT determination deficient if it is “not based on a
reasoned analysis”); id., at 281–282 (1993 guidance memoran-
dum stating that “EPA acts to ensure that the state exer-
cises its discretion within the bounds of the law” (internal
quotation marks omitted); as to BACT, EPA will not inter-
vene if the state agency has given “a reasoned justification
for the basis of its decision” (internal quotation marks omit-
ted)). See also Approval and Promulgation of Air Quality
Implementation Plans; Commonwealth of Virginia—Preven-
tion of Significant Deterioration Program, 63 Fed. Reg. 13797
(1998) (EPA will “review whether any determination by the
permitting authority was made on reasonable grounds prop-
erly supported on the record, described in enforceable terms,
and consistent with all applicable requirements”). We “nor-
mally accord particular deference to an agency interpreta-
tion of ‘longstanding’ duration,” Barnhart v. Walton, 535
U. S. 212, 220 (2002) (quoting North Haven Bd. of Ed. v. Bell,
456 U. S. 512, 522, n. 12 (1982)), recognizing that “well-
reasoned views” of an expert administrator rest on “ ‘a body
of experience and informed judgment to which courts and
litigants may properly resort for guidance,’ ” Bragdon v. Ab-
bott, 524 U. S. 624, 642 (1998) (quoting Skidmore v. Swift &
Co., 323 U. S. 134, 139–140 (1944)).
We have previously accorded dispositive effect to EPA’s
interpretation of an ambiguous CAA provision. See Chev-
ron U. S. A. Inc. v. Natural Resources Defense Council, Inc.,
467 U. S. 837, 865–866 (1984); Union Elec., 427 U. S., at 256.
The Agency’s interpretation in this case, presented in inter-
nal guidance memoranda, however, does not qualify for the
dispositive force described in Chevron. See Christensen v.
Harris County, 529 U. S. 576, 587 (2000) (“Interpretations

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
488 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
such as those in . . . policy statements, agency manuals, and
enforcement guidelines, all of which lack the force of law—
do not warrant Chevron-style deference.”); accord United
States v. Mead Corp., 533 U. S. 218, 234 (2001). Cogent “ad-
ministrative interpretations . . . not [the] products of formal
rulemaking . . . nevertheless warrant respect.” Washington
State Dept. of Social and Health Servs. v. Guardianship Es-
tate of Keffeler, 537 U. S. 371, 385 (2003). We accord EPA’s
reading of the relevant statutory provisions, §§ 7413(a)(5),
7470(3), 7470(4), 7475(a)(4), 7477, and 7479(3), that measure
of respect.
B
ADEC assails the Agency’s construction of the Act on sev-
eral grounds. Its arguments do not persuade us to reject
as impermissible EPA’s longstanding, consistently main-
tained interpretation.
ADEC argues that the statutory definition of BACT,
§ 7479(3), unambiguously assigns to “the permitting author-
ity” alone determination of the control technology qualifying
as “best available.” Brief for Petitioner 21–26. Because
the Act places responsibility for determining BACT with
“the permitting authority,” ADEC urges, CAA excludes fed-
eral Agency surveillance reaching the substance of the
BACT decision. Id., at 22–25. EPA’s enforcement role,
ADEC maintains, is restricted to the requirement “that the
permit contain a BACT limitation.” Id., at 34.
Understandably, Congress entrusted state permitting
authorities with initial responsibility to make BACT deter-
minations “case-by-case.” § 7479(3). A state agency, no
doubt, is best positioned to adjust for local differences in raw
materials or plant configurations, differences that might
make a technology “unavailable” in a particular area. But
the fact that the relevant statutory guides—“maximum” pol-
lution reduction, considerations of energy, environmental,
and economic impacts—may not yield a “single, objectively
‘correct’ BACT determination,” id., at 23, surely does not

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
489 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
signify that there can be no unreasonable determinations.
Nor does Congress’ sensitivity to site-specific factors neces-
sarily imply a design to preclude in this context meaningful
EPA oversight under §§ 113(a)(5) and 167. EPA claims no
prerogative to designate the correct BACT; the Agency as-
serts only the authority to guard against unreasonable desig-
nations. See 298 F. 3d, at 821 (“the question presented
is what requirements the state must meet,” not what final
substantive decision the State must make (emphasis in
original)).13
Under ADEC’s interpretation, EPA properly inquires
whether a BACT determination appears in a PSD permit,
13 The dissent admonishes that “a statute is to be read as a whole.”
Post, at 504 (quoting King v. St. Vincent’s Hospital, 502 U. S. 215, 221
(1991)). We give that unexceptional principle effect by attending both to
the unequivocal grant of supervisory authority to EPA in §§ 113(a)(5) and
167, and to the statutory control on permitting authorities’ discretion con-
tained in the BACT definition, 42 U. S. C. § 7479(3). It is, moreover,
“a cardinal principle of statutory construction’ that ‘a statute ought, upon
the whole, to be so construed that, if it can be prevented, no clause, sen-
tence, or word shall be superfluous, void, or insignificant.” TRW Inc. v.
Andrews, 534 U. S. 19, 31 (2001) (quoting Duncan v. Walker, 533 U. S.
167, 174 (2001)). The Act instructs permitting authorities to identify the
“best,” “maximum” emission reduction technique, taking account of costs.
42 U. S. C. § 7479(3). The dissent does not explain how that instruction
can be construed as something other than a constraint on permitting
authorities’ discretion. Ultimately, the dissent recognizes the essential
statutory requirement: selection of “the technology that can best reduce
pollution within practical constraints.” Post, at 505 (emphasis added).
Nor do we find enlightening Congress’ inclusion of the word “deter-
mines” in the BACT definition. Post, at 503–504. Even under the dis-
sent’s view of the Act, state permitting authorities’ BACT determinations
are not “conclusiv[e] and authoritativ[e].” Post, at 504 (internal quotation
marks and citation omitted). As the dissent develops at length, review of
such BACT determinations may be sought in state court. Post, at 509–
512; Alaska Stat. § 44.62.560 (2002). And EPA actions, of course, are sub-
ject to “the process of judicial review,” post, at 503, Congress empowered
federal courts to provide, here in 42 U. S. C. § 7607(b)(1). See supra, at
482–483.

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
490 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
Brief for Petitioner 34, but not whether that BACT determi-
nation “was made on reasonable grounds properly supported
on the record,” 63 Fed. Reg., at 13797. Congress, however,
vested EPA with explicit and sweeping authority to enforce
CAA “requirements” relating to the construction and modi-
fication of sources under the PSD program, including BACT.
We fail to see why Congress, having expressly endorsed an
expansive surveillance role for EPA in two independent
CAA provisions, would then implicitly preclude the Agency
from verifying substantive compliance with the BACT provi-
sions and, instead, limit EPA’s superintendence to the insub-
stantial question whether the state permitting authority had
uttered the key words “BACT.”
We emphasize, however, that EPA’s rendition of the Act’s
less than crystalline text leaves the “permitting authority”
considerable leeway. The Agency acknowledges “the need
to accord appropriate deference” to States’ BACT designa-
tions, Brief for Respondents 43, and disclaims any intention
to “ ‘second guess’ state decisions,” 63 Fed. Reg., at 13797.
Only when a state agency’s BACT determination is “not
based on a reasoned analysis,” App. 274, may EPA step in to
ensure that the statutory requirements are honored.14 EPA
14 According to the Agency, “[i]t has proven to be relatively rare that a
state agency has put EPA in the position of having to exercise [its] author-
ity,” noting that only two other reported judicial decisions concern EPA
orders occasioned by States’ faulty BACT determinations. Brief for Re-
spondents 30, and n. 9 (citing Allsteel, Inc. v. EPA, 25 F. 3d 312 (CA6
1994), and Solar Turbines Inc. v. Seif, 879 F. 2d 1073 (CA3 1989)). EPA’s
restrained and moderate use of its authority hardly supports the dissent’s
speculation that the federal Agency will “displac[e]” or “degrad[e]” state
agencies or relegate them to the performance of “ministerial” functions.
Post, at 516, 518. Nor has EPA ever asserted authority to override a
state-court judgment. Cf. post, at 511. Preclusion principles, we note in
this regard, unquestionably do apply against the United States, its agen-
cies and officers. See, e. g., Montana v. United States, 440 U. S. 147
(1979).

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
491 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
adhered to that limited role here, explaining why ADEC’s
BACT determination was “arbitrary” and contrary to
ADEC’s own findings. Id., at 149–150. EPA’s limited
but vital role in enforcing BACT is consistent with a scheme
that “places primary responsibilities and authority with
the States, backed by the Federal Government.” S. Rep.
No. 95–127, p. 29.
ADEC also points to 42 U. S. C. § 7475(a)(8), a provision of
the Act expressly requiring, in a limited category of cases,
EPA approval of a state permitting authority’s BACT deter-
mination before a facility may be constructed. See Brief for
Petitioner 25; Reply Brief for Petitioner 6. Had Congress
intended EPA superintendence of BACT determinations,
ADEC urges, Congress would have said so expressly by
mandating Agency approval of all, not merely some, BACT
determinations. Brief for Petitioner 25–26. ADEC’s argu-
ment overlooks the obvious difference between a statutory
requirement, e. g., § 7475(a)(8), and a statutory authoriza-
tion. Sections 113(a)(5) and 167 sensibly do not require
EPA approval of all state BACT determinations, they simply
authorize EPA to act in the unusual case in which a state
permitting authority has determined BACT arbitrarily.
EPA recognizes that its authorization to issue a stop order
may be exercised only when a state permitting authority’s
decision is unreasonable; in contrast, a required approval
may be withheld if EPA would come to a different determi-
nation on the merits. See, e. g., 57 Fed. Reg. 28095 (1992)
(“EPA acknowledges that states have the primary role in
administering and enforcing the various components of the
PSD program. States have been largely successful in this
effort, and EPA’s involvement in interpretative and enforce-
ment issues is limited to only a small number of cases.”).
Even if the Act imposes a requirement of reasoned justifi-
cation for a BACT determination, ADEC ultimately argues,
such a requirement may be enforced only through state ad-

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
492 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
ministrative and judicial processes. Brief for Petitioner 34–
38.15 State review of BACT decisions, according to ADEC,
allows development of an adequate factual record, properly
imposes the burden of persuasion on EPA when it challenges
a State’s BACT determination, and promotes certainty. Id.,
at 36–37. Unless EPA review of BACT determinations is
channeled into state administrative and judicial forums,
ADEC suggests, “there is nothing to prevent the EPA from
invalidating a BACT determination at any time—months,
even years, after a permit has been issued.” Id., at 35.
It would be unusual, to say the least, for Congress to remit
a federal agency enforcing federal law solely to state court.
We decline to read such an uncommon regime into the Act’s
silence. EPA, the expert federal agency charged with en-
forcing the Act, has interpreted the BACT provisions and its
own §§ 113(a)(5) and 167 enforcement powers not to require
recourse to state processes before stopping a facility’s con-
15 From the availability of state-court judicial review, the dissent con-
cludes, it necessarily “follows that EPA . . . must take the same procedural
steps,” of filing suit in state court, as any other person or entity seeking
to challenge the issuance of a PSD permit. Post, at 509. Interpreted
otherwise, the dissent asserts, the Act contains a “loophole” that allows
an EPA “end run around the State’s process.” Post, at 511. In designing
the Act, however, Congress often gave EPA a choice of enforcement meas-
ures. For example, EPA has three options to address a failure to comply
with new source requirements. Compare 42 U. S. C. § 7413(a)(5)(A) (EPA
may “issue an order prohibiting the construction or modification of any
major stationary source”) with § 7413(a)(5)(B) (EPA may “issue an admin-
istrative penalty order”) and § 7413(a)(5)(C) (EPA may “bring a civil ac-
tion”). Other sections of the Act provide EPA with similar options. See,
e. g., §§ 7413(a)(1)–(3). Following the dissent’s logic, EPA’s authority to
bring a civil action would rule out, as a “loophole,” its authority to issue
a stop-construction order.
Moreover, the existence of concurrent authority is hardly at odds with
the Act. As ADEC itself concedes, EPA can issue a checking order if a
PSD permit lacks a BACT determination, Brief for Petitioner 34, even if
state-court jurisdiction could be invoked instead.

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
493 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
struction. See supra, at 485–488. That rational interpre-
tation, we agree, is surely permissible.16
Nor are we persuaded by ADEC’s practical concerns. We
see no reason to conclude that an appropriate record gener-
ally cannot be developed to allow informed federal-court re-
view when EPA disputes a BACT decision’s reasonableness.
ADEC contends that, in this very case, “the State’s BACT
determination was reviewed by the Ninth Circuit on an in-
complete record.” Brief for Petitioner 37. ADEC, how-
ever, offers no particulars to back up its assertion that the
Court of Appeals proceeded on an inadequate evidentiary
record. We note again that the Ninth Circuit ordered EPA
to submit a complete administrative record. 298 F. 3d, at
818. After the Agency declared that the record was com-
plete, “all the parties effectively agreed that the record as it
stood was adequate to resolve the issues on appeal.” Ibid.
As to the burdens of production and persuasion, nothing
in the Act suggests that EPA gains a proof-related tactical
advantage by issuing a stop-construction order instead of
seeking relief through a civil action. But cf. post, at 510
(EPA authority to issue stop-construction orders creates
“the anomaly of shifting the burden of pleading and of ini-
tiating litigation from EPA to the State”). Correspondingly,
nothing in our decision today invites or permits EPA to
achieve an unfair advantage through its choice of litigation
forum. In granting EPA a choice between initiating a civil
action and exercising its stop-construction-order authority,
see supra, at 473–474, 492, n. 15, Congress nowhere sug-
gested that the allocation of proof burdens would differ de-
pending upon which enforcement route EPA selected. The
16 Experience, we have already noted, see supra, at 490, n. 14, affords
no grounding for the dissent’s predictions that EPA oversight, which is
undeniably subject to federal-court review, will “rewor[k] . . . the balance
between State and Federal Governments” and threaten state courts’ inde-
pendence. Post, at 511–512.

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
494 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
point ought not to be left in doubt. Accordingly, we hold
that in either an EPA-initiated civil action or a challenge to
an EPA stop-construction order filed in state or federal
court, the production and persuasion burdens remain with
EPA and the underlying question a reviewing court resolves
remains the same: Whether the state agency’s BACT deter-
mination was reasonable, in light of the statutory guides and
the state administrative record. See supra, at 485–486,
491.17
The Ninth Circuit’s review of EPA’s order is in keeping
with our holding that EPA may not reduce the burden it
must carry by electing to invoke its stop-construction-order
authority. Specifically, the Court of Appeals rested its judg-
ment on what EPA showed from ADEC’s own report: “(1)
Cominco failed to meet its burden of demonstrating [to
ADEC] that SCR was economically infeasible; and (2) ADEC
failed to provide a reasoned justification for its elimination
of SCR as a control option.” 298 F. 3d, at 823. EPA’s con-
clusions, and the basis for them, support the Court of Ap-
peals’ determination that the federal Agency’s grounds for
issuing the orders under review were not “arbitrar[y] and
capriciou[s].” Ibid. Our own analysis, infra, at 497–502,
similarly hinges on the question whether ADEC’s BACT de-
termination was a reasonable one. Our analysis would have
17 “[L]ooking for the burden of pleading is not a foolproof guide to the
allocation of the burdens of proof. The latter burdens do not invaria-
bly follow the pleadings.” 2 J. Strong, McCormick on Evidence § 337,
pp. 411–412 (5th ed. 1999). No “single principle or rule . . . solve[s] all
cases and afford[s] a general test for ascertaining the incidence” of proof
burdens. 9 J. Wigmore, Evidence § 2486, p. 288 (J. Chadbourn rev. ed.
1981) (emphasis deleted). “[I]n a case of first impression,” which we ad-
dress today, “reference to which party has pleaded a fact is no help at
all.” 2 McCormick, supra, § 337, at 412. Among other considerations,
allocations of burdens of production and persuasion may depend on which
party—plaintiff or defendant, petitioner or respondent—has made the “af-
firmative allegation” or “presumably has peculiar means of knowledge.”
9 Wigmore, supra, § 2486, at 288, 290 (emphases deleted); accord Campbell
v. United States, 365 U. S. 85, 96 (1961).

540US2 Unit: $U15 [10-27-05 21:21:54] PAGES PGT: OPIN
495 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
taken the same path had EPA initiated a civil action pursu-
ant to § 113(a)(5)(C), or if the suit under consideration had
been filed initially in state court.
Nor do we find compelling ADEC’s suggestion, reiterated
by the dissent, that, if state courts are not the exclusive judi-
cial arbiters, EPA would be free to invalidate a BACT deter-
mination “months, even years, after a permit has been is-
sued.” Brief for Petitioner 35; post, at 512–514. This case
threatens no such development. It involves preconstruction
orders issued by EPA, see supra, at 481, not postconstruc-
tion federal Agency directives. EPA itself regards it as
“imperative” to act on a timely basis, recognizing that courts
are “less likely to require new sources to accept more strin-
gent permit conditions the farther planning and construction
have progressed.” App. 273 (July 15, 1988, EPA guidance
memorandum). In the one instance of untimely EPA action
ADEC identifies, the federal courts declined to permit en-
forcement to proceed. See United States v. AM General
Corp., 34 F. 3d 472, 475 (CA7 1994) (affirming District Court’s
dismissal of an EPA-initiated enforcement action where EPA
did not act until well after the facility received a PSD permit
and completed plant modifications). EPA, we are confident,
could not indulge in the inequitable conduct ADEC and the
dissent hypothesize while the federal courts sit to review
EPA’s actions. Cf. Walz v. Tax Comm’n of City of New
York, 397 U. S. 664, 678–679 (1970); Panhandle Oil Co. v.
Mississippi ex rel. Knox, 277 U. S. 218, 223 (1928) (Holmes,
J., dissenting), overruled in part by Alabama v. King &
Boozer, 314 U. S. 1, 8–9 (1941).
In sum, EPA interprets the Act to allow substantive fed-
eral Agency surveillance of state permitting authorities’
BACT determinations subject to federal-court review. We
credit EPA’s longstanding construction of the Act and con-
firm EPA’s authority, pursuant to §§ 113(a)(5) and 167, to rule
on the reasonableness of BACT decisions by state permit-
ting authorities.

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
496 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
IV
A
We turn finally, and more particularly, to the reasons why
we conclude that EPA properly exercised its statutory au-
thority in this case. ADEC urges that, even if the Act
allows the Agency to issue stop-construction orders when a
state permitting authority unreasonably determines BACT,
EPA acted impermissibly in this instance. See Brief for
Petitioner 39–48. We note, first, EPA’s threshold objection.
ADEC’s petition to this Court questioned whether the Act
accorded EPA oversight authority with respect to a State’s
BACT determination. Pet. for Cert. 13–22. ADEC did not
present, as a discrete issue, the question whether EPA, as-
suming it had authority to review the substance of a state
BACT determination, nevertheless abused its authority by
countermanding ADEC’s permit for the Red Dog Mine
expansion. See Brief for Respondents 44–45; cf. Reply
Brief for Petitioner 15–16, n. 12 (“EPA asserts authority
to overturn only ‘arbitrary or unreasoned’ state BACT
determinations. . . . Thus, whether the State issued a rea-
soned justification is ‘fairly included’ within the question pre-
sented[.]”). Treating the case-specific issue as embraced
within the sole question presented, we are satisfied that EPA
did not act arbitrarily in finding that ADEC furnished no
tenable accounting for its determination that Low NOx was
BACT for MG–17.
Because the Act itself does not specify a standard for judi-
cial review in this instance,18 we apply the familiar default
standard of the Administrative Procedure Act, 5 U. S. C.
§ 706(2)(A), and ask whether the Agency’s action was “arbi-
18 The Court of Appeals referred to 42 U. S. C. § 7607(d)(9)(A) when it
considered whether EPA’s decision was “arbitrary, capricious, an abuse of
discretion, or otherwise not in accordance with law.” 298 F. 3d 814, 822
(CA9 2002). Section 7607(d)(9), however, applies only to the “subsection”
concerning rulemaking in which it is embedded.

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
497 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
trary, capricious, an abuse of discretion, or otherwise not in
accordance with law.” Even when an agency explains its
decision with “less than ideal clarity,” a reviewing court will
not upset the decision on that account “if the agency’s path
may reasonably be discerned.” Bowman Transp., Inc. v.
Arkansas-Best Freight System, Inc., 419 U. S. 281, 286
(1974). EPA’s three skeletal orders to ADEC and Cominco
surely are not composed with ideal clarity. These orders,
however, are properly read together with accompanying ex-
planatory correspondence from EPA; so read, the Agency’s
comments and orders adequately ground the determination
that ADEC’s acceptance of Low NOx for MG–17 was unrea-
sonable given the facts ADEC found.
In the two draft permits and the final permit, ADEC
formally followed the EPA-recommended top-down method-
ology to determine BACT, as Cominco had done in its appli-
cation. App. 61, 109, 175; see supra, at 475–476. Employ-
ing that methodology in the May 1999 draft permit, ADEC
first concluded that SCR was the most stringent emission-
control technology that was both “technically and economi-
cally feasible.” App. 65; see supra, at 476. That technol-
ogy should have been designated BACT absent “technical
considerations, or energy, environmental, or economic im-
pacts justif[ying] a conclusion that [SCR was] not ‘achiev-
able’ in [this] case.” New Source Review Manual, p. B.2;
App. 61–62. ADEC nevertheless selected Low NOx as
BACT; ADEC did so in May 1999 based on Cominco’s sugges-
tion that fitting all Red Dog Mine generators with Low NOx
would reduce aggregate emissions. Id., at 87, 111–112; see
supra, at 476–477.
In September and December 1999, ADEC again rejected
SCR as BACT but no longer relied on Cominco’s suggestion
that it could reduce aggregate emissions by equipping all
generators with Low NOx. See supra, at 478–480. ADEC
candidly stated that it aimed “[t]o support Cominco’s Red
Dog Mine Production Rate Increase Project, and its contri-

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
498 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
butions to the region.” App. 208. In these second and
third rounds, ADEC rested its selection of Low NOx
squarely and solely on SCR’s “disproportionate cost.” Id.,
at 116; id., at 112–117, 203–208; supra, at 478–480.
EPA concluded that ADEC’s switch from finding SCR eco-
nomically feasible in May 1999 to finding SCR economically
infeasible in September 1999 had no factual basis in the rec-
ord. See App. 138. In the September and December 1999
technical analyses, ADEC acknowledged that “no judgment
[could then] be made as to the impact of [SCR’s] cost on the
operation, profitability, and competitiveness of the Red Dog
Mine.” Id., at 116, 207. ADEC nevertheless concluded
that SCR would threaten both the Red Dog Mine’s “unique
and continuing impact on the economic diversity” of north-
west Alaska and the mine’s “world competitiveness.” Id., at
208. ADEC also stressed the mine’s role as employer in an
area with “historical high unemployment and limited perma-
nent year-round job opportunities.” Id., at 207.
We do not see how ADEC, having acknowledged that no
determination “[could] be made as to the impact of [SCR’s]
cost on the operation . . . and competitiveness of the [mine],”
ibid., could simultaneously proffer threats to the mine’s oper-
ation or competitiveness as reasons for declaring SCR eco-
nomically infeasible. ADEC, indeed, forthrightly explained
why it was disarmed from reaching any judgment on
whether, or to what extent, implementation of SCR would
adversely affect the mine’s operation or profitability: Com-
inco had declined to provide the relevant financial data, dis-
puting the need for such information and citing “confiden-
tiality” concerns, id., at 134; see supra, at 479–480; 298 F. 3d,
at 823 (“Cominco failed to meet its burden of demonstrating
that SCR was economically infeasible.”). No record evi-
dence suggests that the mine, were it to use SCR for its new
generator, would be obliged to cut personnel or raise zinc
prices. Absent evidence of that order, ADEC lacked cause

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
499 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
for selecting Low NOx as BACT based on the more stringent
control’s impact on the mine’s operation or competitiveness.
Nor has ADEC otherwise justified its choice of Low NOx.
To bolster its assertion that SCR was too expensive, ADEC
invoked four BACT determinations made in regard to diesel
generators used for primary power production; BACT’s cost,
in those instances, ranged from $0 to $936 per ton of nitrogen
oxide removed. App. 205–206; supra, at 480. ADEC itself,
however, had previously found SCR’s per-ton cost, then esti-
mated as $2,279, to be “well within what ADEC and EPA
considers economically feasible.” App. 84; cf. id., at 204 (es-
timating SCR’s per ton cost to be $2,100). No reasoned ex-
planation for ADEC’s retreat from this position appears in
the final permit. See id., at 138 (“[SCR’s cost falls] well
within the range of costs EPA has seen permitting authori-
ties nationwide accept as economically feasible for NOx con-
trol except where there are compelling site specific factors
that indicate otherwise.”). Tellingly, as to examples of low-
cost BACT urged by Cominco, ADEC acknowledged: “The
cited examples of engines permitted in Alaska without re-
quiring SCR are not valid examples as they either took place
over 18 months ago or were not used for similar purposes.”
Id., at 233–234 (footnote omitted). ADEC added that it has
indeed “permitted [Alaska] projects requiring SCR.” Id., at
234. Further, EPA rejected ADEC’s comparison between
the mine and a rural utility, see supra, at 479, because “no
facts exist to suggest that the ‘economic impact’ of the incre-
mentally higher cost of SCR on the world’s largest producer
of zinc concentrates would be anything like its impact on a
rural, non-profit utility that must pass costs on to a small
base of individual consumers,” Brief for Respondents 49;
App. 138–139 (similar observation in Nov. 10, 1999, EPA
letter).
ADEC’s basis for selecting Low NOx thus reduces to a
readiness “[t]o support Cominco’s Red Dog Mine Production
Rate Increase Project, and its contributions to the region.”

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
500 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Opinion of the Court
Id., at 208. This justification, however, hardly meets
ADEC’s own standard of a “source-specific . . . economic im-
pac[t] which demonstrate[s] [SCR] to be inappropriate as
BACT.” Id., at 177. In short, as the Ninth Circuit deter-
mined, EPA validly issued stop orders because ADEC’s
BACT designation simply did not qualify as reasonable in
light of the statutory guides.
In its briefs to this Court, ADEC nonetheless justifies its
selection of Low NOx as BACT for MG–17 on the ground
that lower aggregate emissions would result from Cominco’s
“agree[ment] to install Low NOx on all its generators.”
Brief for Petitioner 42, and n. 12 (emphasis added); id., at 29;
Reply Brief for Petitioner 19, n. 16. We need not dwell on
ADEC’s attempt to resurrect Cominco’s emissions-offsetting
suggestion, see supra, at 477, adopted in the initial May 1999
draft permit, but thereafter dropped. As ADEC acknowl-
edges, the final PSD permit did not offset MG–17’s emissions
against those of the mine’s six existing generators, installa-
tions that were not subject to BACT. Brief for Petitioner
42, n. 12; App. 149. ADEC recognized in September and
December 1999 that a State may treat emissions from sev-
eral pollutant sources as falling under one “bubble” 19 for
PSD permit purposes only if every pollutant source so aggre-
gated is “part of the permit action.” Id., at 111, 199. Off-
setting new emissions against those from any of the mine’s
other generators, ADEC agreed, “[was] not a consideration
of the BACT review provided for by the applicable law or
guidelines,” for those generators remained outside the per-
mit’s compass. Id., at 112, 199. ADEC plainly did not, and
could not, base its December 10, 1999, permit and technical
analysis on an emissions-offsetting rationale drawing in gen-
19 Cf. Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc.,
467 U. S. 837, 853–859 (1984) (upholding EPA regulations allowing States
to treat all pollutant-emitting devices within the same stationary source
in a nonattainment area as though encased in a single “bubble”).

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
501 Cite as: 540 U. S. 461 (2004)
Opinion of the Court
erators not subject to BACT. Id., at 111–112.20 By that
time, only MG–17 was “part of the permit action.” Id., at
111, 199.
B
We emphasize that today’s disposition does not impede
ADEC from revisiting the BACT determination in question.
In letters and orders throughout the permitting process,
EPA repeatedly commented that it was open to ADEC to
prepare “an appropriate record” supporting its selection of
Low NOx as BACT. Tr. of Oral Arg. 35; see App. 127 (at-
tachment to Sept. 28, 1999, EPA letter to ADEC, stating “an
analysis of whether requiring Cominco to install and operate
[SCR] would have any adverse economic impacts upon Com-
inco specifically” might demonstrate SCR’s economic infeasi-
bility); id., at 150 (letter accompanying EPA’s Dec. 10, 1999,
finding of noncompliance and order reiterating the Agency’s
willingness to “review and consider any additional informa-
tion or analyses provided by ADEC or Cominco” on Low
NOx as BACT); App. to Pet. for Cert. 36a (EPA Dec. 10,
1999, order inviting ADEC to justify its choice of Low NOx
by “document[ing] why SCR is not BACT [for MG–17]”); id.,
at 49a (similar statement in Feb. 8, 2000, order). At oral
argument, counsel for EPA reaffirmed that, “absolutely,”
ADEC could reconsider the matter and, on an “appropriate
20 The May 4, 1999, draft permit considered whether adding Low NOx
to seven generators would result in lower emissions than adding SCR to
only two and choosing one of the latter as a standby unit. App. 86–87.
Before December 10, 1999, however, Cominco agreed to install Low NOx
controls on four of the mine’s six existing generators—MG–1, MG–3,
MG–4, and MG–5—in order to increase use of those generators without
exceeding the 1994 PSD permit’s operating restriction. Id., at 149. Hav-
ing agreed to use Low NOx on four generators, Cominco could propose
in the December 10, 1999, permit only the addition of Low NOx to two
generators—MG–2 and MG–6—to offset increases in emissions from MG–
17. No facts in the record support any suggestion that addition of Low
NOx to three generators, MG–2, MG–6, and MG–17, would result in lower
aggregate emissions than the addition of SCR to MG–17 alone.

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
502 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Kennedy, J., dissenting
record,” endeavor to support Low NOx as BACT. Tr. of
Oral Arg. 35.21 We see no reason not to take EPA at its
word.
* * *
In sum, we conclude that EPA has supervisory authority
over the reasonableness of state permitting authorities’
BACT determinations and may issue a stop-construction
order, under §§ 113(a)(5) and 167, if a BACT selection is not
reasonable. We further conclude that, in exercising that au-
thority, the Agency did not act arbitrarily or capriciously in
finding that ADEC’s BACT decision in this instance lacked
evidentiary support. EPA’s orders, therefore, were neither
arbitrary nor capricious. The judgment of the Court of Ap-
peals is accordingly
Affirmed.
Justice Kennedy, with whom The Chief Justice, Jus-
tice Scalia, and Justice Thomas join, dissenting.
The majority, in my respectful view, rests its holding on
mistaken premises, for its reasoning conflicts with the ex-
press language of the Clean Air Act (CAA or Act), with
sound rules of administrative law, and with principles that
preserve the integrity of States in our federal system. The
State of Alaska had in place procedures that were in full
compliance with the governing statute and accompanying
regulations promulgated by the Environmental Protection
Agency (EPA). As I understand the opinion of the Court
and the parties’ submissions, there is no disagreement on
this point. Alaska followed these procedures to determine
the best available control technology (BACT). EPA, how-
21 The dissent is daunted by the hypothesis that “[b]ecause there can
always be an additional procedure to ensure that the preceding process
was followed,” the State “may never reach” the goal of issuing a permit.
Post, at 515 (“The majority creates a sort of Zeno’s paradox for state
agencies.”). Again, the dissent can point to no instance in which EPA has
indulged in any piling of process upon process. See supra, at 493, n. 16.

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
503 Cite as: 540 U. S. 461 (2004)
Kennedy, J., dissenting
ever, sought to overturn the State’s decision, not by the proc-
ess of judicial review, but by administrative fiat. The Court
errs, in my judgment, by failing to hold that EPA, based
on nothing more than its substantive disagreement with the
State’s discretionary judgment, exceeded its powers in set-
ting aside Alaska’s BACT determination.
I
As the majority explains, the case begins with §§ 113(a)(5)
and 167 of the Act. 42 U. S. C. §§ 7413(a)(5), 7477. These
provisions give EPA authority to enforce “requirements”
of the CAA. The meaning of the word “requiremen[t],”
though, is not defined in these provisions. Other provisions
of the Act must be consulted. All parties agree that the
requirement in this case is the “preconstruction require-
men[t]” that a “major emitting facility” be “subject to the
best available control technology [BACT] for each pollutant
subject to regulation under this chapter emitted from, or
which results from, such facility.” § 7475(a)(4). BACT, in
turn, is defined as
“an emission limitation based on the maximum degree
of reduction of each pollutant subject to regulation
under this chapter emitted from or which results from
any major emitting facility, which the permitting author-
ity, on a case-by-case basis, taking into account energy,
environmental, and economic impacts and other costs,
determines is achievable for such facility through appli-
cation of production processes and available methods,
systems, and techniques . . . .” § 7479(3).
The majority holds that, under the CAA, state agencies
are vested with “initial responsibility for identifying BACT
in line with the Act’s definition of that term” and that EPA
has a “broad oversight role” to ensure that a State’s BACT
determination is “reasonably moored to the Act’s provi-
sions.” Ante, at 484–485. The statute, however, contem-

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
504 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Kennedy, J., dissenting
plates no such arrangement. It directs the “permitting au-
thority”—here, the Alaska Department of Environmental
Conservation (ADEC)—to “determine” what constitutes
BACT. To “determine” is not simply to make an initial rec-
ommendation that can later be overturned. It is “[t]o decide
or settle . . . conclusively and authoritatively.” American
Heritage Dictionary 495 (4th ed. 2000). Cf. 5 U. S. C. § 554
(“to be determined on the record after opportunity for an
agency hearing”).
The BACT definition presumes that the permitting author-
ity will exercise discretion. It presumes, in addition, that
the BACT decision will accord full consideration to the statu-
tory factors and other relevant and necessary criteria. Con-
trary to the majority’s holding, the statute does not direct
the State to find as BACT the technology that results in the
“maximum reduction of a pollutant achievable for [a] facility”
in the abstract. Ante, at 485 (internal quotation marks
omitted). Indeed, for a State to do so without regard to the
other mandatory criteria would be to ignore the words of the
statute. The Act requires a more comprehensive judgment.
It provides that the permitting authority must “tak[e] into
account” a set of contextual considerations—“energy, envi-
ronmental, and economic impacts and other costs”—to iden-
tify the best control technology “on a case-by-case basis.”
42 U. S. C. § 7479(3). The majority reaches its narrow view
of the scope of the State’s discretion only by wresting two
adjectives, “maximum” and “achievable,” out of context. In
doing so, it ignores “the cardinal rule that a statute is to be
read as a whole.” King v. St. Vincent’s Hospital, 502 U. S.
215, 221 (1991).
To be sure, §§ 113(a)(5) and 167 authorize EPA to enforce
requirements of the Act. These provisions, however, do not
limit the States’ latitude and responsibility to balance all the
statutory factors in making their discretionary judgments.
If a State has complied with the Act’s requirements,
§§ 113(a)(5) and 167 are not implicated and can supply no sep-

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
505 Cite as: 540 U. S. 461 (2004)
Kennedy, J., dissenting
arate basis for EPA to exercise a supervisory role over a
State’s discretionary decision. The Court of Appeals for the
Ninth Circuit had it altogether backwards when it reasoned
that, “because neither Section 113(a)(5) nor Section 167 con-
tains any exemption for requirements that involve the state’s
exercise of discretion,” EPA had the authority to issue or-
ders countermanding the State’s BACT determination. 298
F. 3d 814, 820 (2002). The question is not whether the two
sections contain any exemption. Rather, it is about the na-
ture of the Act’s requirements and whether EPA has the
authority to set aside a BACT determination when no re-
quirement of the Act was violated in the first place. In af-
firming the judgment of the Court of Appeals, the majority
repeats the same analytical error. See ante, at 490 (“We fail
to see why Congress, having expressly endorsed an expan-
sive surveillance role for EPA in two independent CAA pro-
visions, would then implicitly preclude the Agency from veri-
fying substantive compliance with [BACT] . . .”). When the
statute is read as a whole, it is clear that the CAA com-
mits BACT determinations to the discretion of the relevant
permitting authorities. Unless an objecting party, includ-
ing EPA, prevails on judicial review, the determinations are
conclusive.
Here the state agency, ADEC, recognized it was required
to make a BACT determination. It issued two detailed re-
ports in response to comments by interested parties and con-
cluded that Low Nitrogen Oxide (NOx) was BACT. The re-
quirement that the agency weigh the list of statutory factors,
study all other relevant considerations, and decide the tech-
nology that can best reduce pollution within practical con-
straints was met in full. As even EPA acknowledged,
ADEC “provid[ed] a detailed accounting of the process.”
App. 286. This is not a case, then, where the state agency
failed to have a BACT review procedure in place or alto-
gether refused to apply the statute’s formal requirements.
EPA’s only quarrel is with ADEC’s substantive conclusion.

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
506 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Kennedy, J., dissenting
In disagreeing with ADEC, EPA’s sole contention, in the sec-
tion of its order titled “Findings of Fact,” is that “[selective
catalytic reduction] is BACT.” App. to Pet. for Cert. 30a,
34a (emphasis added). In addition, EPA does not allege that
using Low NOx would violate other CAA requirements, such
as the National Ambient Air Quality Standards, Alaska’s
Prevention of Significant Deterioration (PSD) increments,
or other applicable emission standards, see 42 U. S. C.
§ 7475(a)(3). On this state of the record there is no deviation
from any statutory “requirement.” As a result, EPA has
no statutory basis to invoke the enforcement authority of
§§ 113(a)(5) and 167.
When Congress intends to give EPA general supervisory
authority, it says so in clear terms. In addition to requiring
EPA’s advance approval of BACT determinations in some
instances, 42 U. S. C. § 7475(a)(8), the statute grants EPA
powers to block the construction or operation of polluting
sources in circumstances not at issue here, §§ 7426(b), (c)(1),
7410(a)(2)(D)(i). Outside the context of the CAA, Congress
likewise knows how to establish federal oversight in unam-
biguous language. See, e. g., 42 U. S. C. § 1396a(a)(13)(A)
(1994 ed.) (requiring, under the Medicaid Act, reimbursement
according to rates that a “State finds, and makes assurances
satisfactory to the Secretary [of Health and Human Serv-
ices], are reasonable and adequate to meet the costs which
must be incurred by efficiently and economically operated
facilities”); Wilder v. Virginia Hospital Assn., 496 U. S. 498
(1990). No analogous language is used in the statutory
definition of BACT.
EPA insists it needs oversight authority to prevent a “race
to the bottom,” where jurisdictions compete with each other
to lower environmental standards to attract new industries
and keep existing businesses within their borders. What-
ever the merits of these arguments as a general matter,
EPA’s distrust of state agencies is inconsistent with the Act’s
clear mandate that States bear the primary role in control-

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
507 Cite as: 540 U. S. 461 (2004)
Kennedy, J., dissenting
ling pollution and, here, the exclusive role in making BACT
determinations. In “cho[osing] not to dictate a Federal re-
sponse to balancing sometimes conflicting goals” at the ex-
pense of “[m]aximum flexibility and State discretion,” H. R.
Rep. No. 95–294, p. 146 (1977), Congress made the overriding
judgment that States are more responsive to local conditions
and can strike the right balance between preserving environ-
mental quality and advancing competing objectives. By as-
signing certain functions to the States, Congress assumed
they would have a stake in implementing the environmental
objectives of the Act. At the same time, Congress charged
EPA with setting ambient standards and enforcing emission
limits, 42 U. S. C. § 7475(a)(3), to ensure that the Nation takes
the necessary steps to reduce air pollution.
The presumption that state agencies are not to be trusted
to do their part is unwarranted in another respect: EPA it-
self said so. As EPA concedes, States, by and large, take
their statutory responsibility seriously, and EPA sees no rea-
son to intervene in the vast majority of cases. Brief for Re-
spondents 30, n. 9; 57 Fed. Reg. 28095 (1992) (“States have
been largely successful in [‘administering and enforcing the
various components of the PSD program’], and EPA’s in-
volvement in interpretative and enforcement issues is lim-
ited . . .”). In light of this concession, EPA and amici
not only fail to overcome the established presumption that
States act in good faith, see Alden v. Maine, 527 U. S. 706,
755 (1999) (“We are unwilling to assume the States will re-
fuse to honor . . . or obey the binding laws of the United
States”), but also admit that their fears about a race to the
bottom bear little relation to the real-world experience
under the statute. See ante, at 502 (“We see no reason not
to take EPA at its word”).
II
The statute contains safeguards to correct arbitrary and
capricious BACT decisions when they do occur. Before
EPA approves a State’s PSD permit program that allows a

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
508 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Kennedy, J., dissenting
state agency to make BACT determinations, EPA must be
satisfied that the State provides “an opportunity for state
judicial review.” 61 Fed. Reg. 1882 (1996). Furthermore,
before an individual permit may issue, the State must allow
all “interested persons,” including “representatives of the
[EPA] Administrator,” to submit comments on, among other
things, “control technology requirements.” 42 U. S. C.
§ 7475(a)(2). To facilitate EPA’s participation in the State’s
public comment process, the statute further provides that
specific procedures be followed to inform the EPA Adminis-
trator of “every action” taken in the course of the permit
approval process. § 7475(d) (“Each State shall transmit to
the Administrator a copy of each permit application relating
to a major emitting facility received by such State and pro-
vide notice to the Administrator of every action related to
the consideration of such permit”). Any person who partici-
pated in the comment process can pursue an administrative
appeal of the State’s decision, followed, as mentioned, by ju-
dicial review in state courts.
EPA followed none of the normal procedures here. Only
after the period for public comments expired did it intervene
and seek to overturn Alaska’s decision that Low NOx was
BACT. To justify its decision to opt out of the State’s ad-
ministrative and judicial review process and, instead, to issue
a unilateral order after everyone had spoken, EPA complains
that it has not before intervened in “any State administrative
review proceedings in State courts” and should not now be
forced to do so. Tr. of Oral Arg. 35. With scant analysis,
the majority agrees. Ante, at 492 (“It would be unusual, to
say the least, for Congress to remit a federal agency enforc-
ing federal law solely to state court. We decline to read
such an uncommon regime into the Act’s silence”). The
problem, of course, is that it is all the more unusual to allow a
federal agency to take unilateral action to set aside a State’s
administrative decision.

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
509 Cite as: 540 U. S. 461 (2004)
Kennedy, J., dissenting
Despite EPA’s protestations, the statute makes explicit
provision for EPA to challenge a state agency’s BACT
determination in state proceedings. The statute requires
States to set up an administrative process for “interested
persons” to submit comments. § 7475(a)(2). “[I]nterested
persons,” Congress took care to note, include “representa-
tives of the [EPA] Administrator.” Ibid.; see also Alaska
Stat. § 46.14.990(20) (2002) (defining “person” to include “an
agency of the United States”). Given that EPA itself re-
quires, as a condition of approving a State’s PSD program,
that this process culminate in judicial review in state courts,
61 Fed. Reg., at 1882, it follows that EPA, a subset of all
“interested persons,” must take the same procedural steps
and cannot evade the more painstaking state process by a
mere stroke of the pen under the agency’s letterhead.
On a more fundamental level, EPA and the majority con-
fuse a substantive environmental statute like the CAA with
a general administrative law statute like the Administrative
Procedure Act (APA). EPA, the federal agency charged
only with the CAA’s implementation, has no roving commis-
sion to ferret out arbitrary and capricious conduct by state
agencies under the state equivalent of the APA. That task
is left to state courts. See Idaho v. Coeur d’Alene Tribe of
Idaho, 521 U. S. 261, 276 (1997) (“[T]he elaboration of admin-
istrative law . . . is one of the primary responsibilities of the
state judiciary”).
Like federal courts, state courts are charged with review-
ing agency actions to ensure that they comport with princi-
ples of rationality and due process. See, e. g., 5 U. S. C.
§ 706(2)(A); Alaska Stat. § 44.62.570(b)(3) (2002). Counsel for
respondents were unable to identify, either in their briefs or
at oral argument, a single State that “does not have in its
law the requirement that its own agencies . . . act rationally.”
Tr. of Oral Arg. 30. Although it remains an open question
whether EPA can bypass the state judiciary and go directly
into federal district court under 28 U. S. C. § 1345, the avail-

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
510 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Kennedy, J., dissenting
ability of state judicial review defeats the Government’s ar-
gument that, absent EPA’s oversight, there is a legal vacuum
where BACT decisions are not subject to review.
Requiring EPA to seek administrative and judicial review
of a State’s BACT determination, instead of allowing it to be
overturned by fiat, avoids the anomaly of shifting the burden
of pleading and of initiating litigation from EPA to the State.
Whether the BACT decision is reviewed in state court, or in
federal district court if that option is available, see supra, at
509 and this page, EPA, as petitioner, bears the initial bur-
den and costs of filing a petition for review alleging that the
State acted arbitrarily. Under the scheme endorsed by the
majority today, the tables are turned. Once EPA has issued
an enforcement order, and the State seeks to invalidate that
order, the State bears the burden of alleging that EPA acted
arbitrarily. EPA and the majority concede that, because
States enjoy substantial discretion in making BACT deter-
minations, courts reviewing EPA’s order must ask not simply
whether EPA acted arbitrarily but the convoluted question
whether EPA acted arbitrarily in finding the State acted ar-
bitrarily. Even under this unwieldy standard of review, and
even if the burdens of persuasion and production remain
with EPA, see ante, at 493–494, the initial burden of pleading
and litigation now belongs to the State.
To make its decision more palatable, the majority holds
that EPA still bears the burdens of production and persua-
sion, but there is little authority for this. The Court pur-
ports to rely on McCormick on Evidence for the proposition
that “ ‘looking for the burden of pleading is not a foolproof
guide to the allocation of the burdens of proof.’ ” Ante, at
494, n. 17 (quoting 2 J. Strong, McCormick on Evidence § 337,
pp. 411–412 (5th ed. 1999)). The example—affirmative de-
fense—discussed in that passage of the treatise, however, is
far afield from the issues raised in this case. In fact, the
treatise instructs that “[i]n most cases, the party who has the
burden of pleading a fact will have the burdens of producing

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
511 Cite as: 540 U. S. 461 (2004)
Kennedy, J., dissenting
evidence and of persuading the jury of its existence as well.”
Id., at 411. This is because “[t]he burdens of pleading and
proof with regard to most facts have been and should be
assigned to the plaintiff who generally seeks to change the
present state of affairs and who therefore naturally should
be expected to bear the risk of failure of proof or persua-
sion.” Id., at 412. In this case, EPA changed the status
quo ante by issuing an order invalidating ADEC’s decision.
Without upsetting accepted evidentiary principles, the ma-
jority cannot explain why EPA, as respondent in federal
court—as opposed to the State, as petitioner alleging that
EPA’s fait accompli was arbitrary—should bear the burdens
of persuasion and production, or how this unusual realloca-
tion of burdens should work in practice.
In any event, even the majority accepts that, under its
reading of the statute, the State now bears the burden of
pleading. With this burden-shifting benefit alone, EPA is
most unlikely to follow the procedure, prescribed by federal
law, of participating in the State’s administrative process and
seeking judicial review in state courts. Instead, EPA can
simply issue a unilateral order invalidating the State’s BACT
determination and put the burden on the State to challenge
EPA’s order. This end run around the State’s process is
sure to undermine it. Unless Congress was on a fool’s er-
rand, the loophole the majority finds goes only to demon-
strate the inconsistency between its approach and the statu-
tory scheme.
There is a further, and serious, flaw in the Court’s ruling.
Suppose, before EPA issued its orders setting aside the
State’s BACT determination, an Alaska state court had re-
viewed the matter and found no error of law or abuse of
discretion in ADEC’s determination. The majority’s inter-
pretation of the statute would allow EPA to intervene at this
point for the first time, announce that ADEC’s determination
is unreasoned under the CAA, and issue its own orders nulli-
fying the state court’s ruling. This reworking of the bal-

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
512 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Kennedy, J., dissenting
ance between State and Federal Governments, not to men-
tion the reallocation of authority between the Executive and
Judicial Branches, shows the implausibility of the majority’s
reasoning.
If a federal agency were to exercise an analogous power
to review the decisions of federal courts, the arrangement
would violate the well-established rule that the judgments
of Article III courts cannot be revised by the Executive or
Legislative Branches. See Hayburn’s Case, 2 Dall. 409, 410,
n. (1792) (“ ‘[B]y the Constitution, neither the Secretary [of]
War, nor any other Executive officer, nor even the Legisla-
ture, are authorized to sit as a court of errors on . . . judicial
acts or opinions . . .’ ”); see also Plaut v. Spendthrift Farm,
Inc., 514 U. S. 211 (1995). The principle that judicial deci-
sions cannot be reopened at the whim of the Executive or
the Legislature is essential to preserving separation of pow-
ers and judicial independence. Judges cannot, without sac-
rificing the autonomy of their office, put onto the scales of
justice some predictive judgment about the probability that
an administrator might reverse their rulings.
The Court today denies state judicial systems the same
judicial independence it has long guarded for itself—only
that the injury here is worse. Under the majority’s holding,
decisions by state courts would be subject to being over-
turned, not just by any agency, but by an agency established
by a different sovereign. We should be reluctant to inter-
pret a congressional statute to deny to States the judicial
independence guaranteed by their own constitutions. See
Buckalew v. Holloway, 604 P. 2d 240, 245 (Alaska 1979)
(“There is no doubt that judicial independence was a para-
mount concern of the delegates [to the Alaska Constitutional
Convention]”); see also, e. g., Cal. Const., Art. 3, § 3 (“The
powers of state government are legislative, executive, and
judicial. Persons charged with the exercise of one power
may not exercise either of the others except as permitted
by this Constitution”); see also 7 B. Witkin, Summary of

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
513 Cite as: 540 U. S. 461 (2004)
Kennedy, J., dissenting
California Law § 107, pp. 159–160 (9th ed. 1988) (“[Under] the
principle of separation of powers . . . , one [department] can-
not exercise or interfere with the functions of either of the
others”). The Federal Government is free, within its vast
legislative authority, to impose federal standards. For
States to have a role, however, their own governing proc-
esses must be respected. New York v. United States, 505
U. S. 144 (1992). If, by some course of reasoning, state
courts must live with the insult that their judgments can be
revised by a federal agency, the Court should at least insist
upon a clear instruction from Congress. That directive can-
not be found here. Cf. Gregory v. Ashcroft, 501 U. S. 452,
460 (1991) (“[I]f Congress intends to alter the usual constitu-
tional balance between the States and the Federal Govern-
ment, it must make its intention to do so unmistakably clear
in the language of the statute” (internal quotation marks
omitted)).
There is a final deficiency in the scheme the majority finds
in the statute. Nothing in the Court’s analysis prevents
EPA from issuing an order setting aside a BACT determina-
tion months, or even years, later. Congress cannot have in-
tended this result. After all, when Congress provides for
EPA’s involvement, it directs the agency to act sooner rather
than later by establishing a preauthorization procedure. 42
U. S. C. § 7475(a)(8). The majority misses the point when it
faults ADEC for “overlook[ing] the obvious difference be-
tween a statutory requirement . . . and a statutory authoriza-
tion.” Ante, at 491 (emphasis deleted). ADEC does not
overlook the difference between approval before the fact and
oversight after the fact. Rather, ADEC, unlike the major-
ity, recognizes that the Act’s explicit provision for a preau-
thorization process underscores the need for finality in state
permitting decisions, making implausible an interpretation
of the statute that would allow a post hoc veto procedure
that upsets the same reliance and expectation interests.

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
514 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Kennedy, J., dissenting
The majority’s initial response that “[t]his case threatens
no such development [because] [i]t involves preconstruction
orders issued by EPA . . . , not postconstruction federal
Agency directives,” ante, at 495, provides no assurance that
the logic of its reasoning would not in the future allow EPA’s
belated interventions. When the majority confronts the
problem, it concludes that “EPA, we are confident, could not
indulge in the inequitable conduct ADEC and the dissent
hypothesize while the federal courts sit to review EPA’s ac-
tions.” Ibid. The authority it cites for this proposition,
however, consists of nothing more than a religious exemption
case that is far removed from the issues presented here and
a dissent from a case that has been overruled in part. Ibid.
State agencies rely on this dictum at their own risk.
The majority’s reassurance to the States will likely be to
no avail. “The principle that the United States are not
bound by any statute of limitations, nor barred by any laches
of their officers, however gross, in a suit brought by them as
a sovereign Government to enforce a public right, or to as-
sert a public interest, is established past all controversy or
doubt.” United States v. Beebe, 127 U. S. 338, 344 (1888);
see also United States v. Summerlin, 310 U. S. 414, 416
(1940) (“It is well settled that the United States is not bound
by state statutes of limitation or subject to the defense of
laches in enforcing its rights”); Utah Power & Light Co. v.
United States, 243 U. S. 389, 409 (1917) (“[L]aches or neglect
of duty on the part of officers of the Government is no de-
fense to a suit by it to enforce a public right or protect a
public interest. . . . A suit by the United States to enforce
and maintain its policy . . . stands upon a different plane in
this and some other respects from the ordinary private suit
. . .”). Section 167, moreover, is mandatory. Once a viola-
tion of a statutory “requirement” is found, “[t]he Adminis-
trator shall . . . take such measures, including issuance of
an order, or seeking injunctive relief, as necessary to pre-
vent the construction or modification of a major emitting fa-

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
515 Cite as: 540 U. S. 461 (2004)
Kennedy, J., dissenting
cility which does not conform to the requirements of this
part . . . .” 42 U. S. C. § 7477. In short, EPA’s enforcement
authority can—indeed, must—be exercised at any point. In
light of our precedents a court would be hard pressed to
hold otherwise.
The majority seeks to limit the consequence of its holding
by quoting the response by respondents’ counsel at oral ar-
gument that ADEC could “absolutely” arrive at the same
BACT determination if only it would pile on another layer of
procedure and justify its decision on an “ ‘appropriate rec-
ord.’ ” Ante, at 501–502 (quoting Tr. of Oral Arg. 35). As
the Court of Appeals recognized in a prior case, however,
this option gives no solace to the States:
“The hardship is the process itself. Process costs
money. If a federal licensee must spend years attempt-
ing to satisfy an elaborate, shifting array of state proce-
dural requirements, then he must borrow a fortune to
pay lawyers, economists, accountants, archaeologists,
historians, engineers, recreational consultants, environ-
mental consultants, biologists and others, with no reve-
nue, no near-term prospect of revenue, and no certainty
that there ever will be revenue. Meanwhile, politics,
laws, interest rates, construction costs, and costs of al-
ternatives change. Undue process may impose cost and
uncertainty sufficient to thwart the federal determina-
tion that a power project should proceed.” Sayles
Hydro Associates v. Maughan, 985 F. 2d 451, 454 (CA9
1993).
If there is to be a second look, notwithstanding the 18
months ADEC spent analyzing BACT, a third or fourth look
is just as permissible. The majority creates a sort of Zeno’s
paradox for state agencies. Because there can always be an
additional procedure to ensure that the preceding process
was followed, no matter how many steps States take toward
the objective, they may never reach it.

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
516 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Kennedy, J., dissenting
This is a most regrettable result. In the proper discharge
of their responsibilities to implement the CAA in different
conditions and localities nationwide, the States maintain per-
manent staffs within special agencies. These state employ-
ees, who no doubt take pride in their own resourcefulness,
expertise, and commitment to the law, are the officials di-
rected by Congress to make case-by-case, site-specific, deter-
minations under the Act. Regulated persons and entities
should be able to consult an agency staff with certainty and
confidence, giving due consideration to agency recommenda-
tions and guidance. After today’s decision, however, a state
agency can no longer represent itself as the real governing
body. No matter how much time was spent in consultation
and negotiation, a single federal administrator can in the
end set all aside by a unilateral order. This is a great step
backward in Congress’ design to grant States a significant
stake in developing and enforcing national environmental
objectives.
If EPA were to announce that permit applications subject
to BACT review must be submitted to it in the first instance
and can be forwarded to the State only with EPA’s advance
approval, I should assume even the majority would find the
basic structure of the BACT provisions undercut. In practi-
cal terms, however, the majority displaces state agencies,
and degrades their role, in much the same way. In the case
before us the applicant made elaborate submissions to
ADEC. For over a year and a half, there ensued the con-
structive discourse that is the very object of the agency proc-
ess, with both the ADEC staff and the applicant believing
the State’s decision would be dispositive. EPA did not par-
ticipate in the administrative process, but waited until after
the record was closed to intervene by issuing an order set-
ting aside the BACT determination.
We are advised that an applicant sometimes must spend
up to $500,000 on the permit process and that, for a com-
plex project, the time for approval can take from five to

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
517 Cite as: 540 U. S. 461 (2004)
Kennedy, J., dissenting
seven years. Brief for National Environmental Develop-
ment Association et al. as Amici Curiae 8. Under the new
multiple-tiered process, permit expenditures become less
justified, state officials less credible, reliance less certain.
The Court should be under no illusion that its decision re-
spects the State’s administrative process.
The federal balance is remitted, in many instances, to Con-
gress. Here the Court remits it to a single agency official.
This is inconsistent with the assurance Congress gave to reg-
ulated entities when it allowed state agencies to decide upon
the grant or denial of a permit under the BACT provisions
of the CAA.
III
In the end EPA appears to realize the weakness of its
arguments and asks us simply to defer to its expertise in
light of the purported statutory ambiguity. See Brief for
Respondents 41–43 (asking for deference under Chevron
U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467
U. S. 837 (1984)). To its credit, the majority holds Chevron
deference inapplicable. Deference is inappropriate for all
the reasons the majority recites, ante, at 487–488, plus one
more: The statute is not in any way ambiguous. As a result,
our inquiry should proceed no further.
Actions, however, speak louder than words, and the ma-
jority ends up giving EPA the very Chevron deference—and
more—it says should be denied. The Court’s opinion is
chock full of Chevron-like language. Compare 467 U. S., at
843 (“whether the agency’s answer is based on a permissible
construction of the statute”); id., at 845 (“whether the Ad-
ministrator’s view . . . is a reasonable one”), with ante, at 488
(“[EPA’s] arguments do not persuade us to reject [them] as
impermissible”); ante, at 493 (“That rational interpretation,
we agree, is surely permissible”). So deficient are its statu-
tory arguments that the majority must hide behind Chev-
ron’s vocabulary, despite its explicit holding that Chevron
does not apply. In applying Chevron de facto under these

540US2 Unit: $U15 [10-27-05 21:21:55] PAGES PGT: OPIN
518 ALASKA DEPT. OF ENVIRONMENTAL
CONSERVATION v. EPA
Kennedy, J., dissenting
circumstances, however, the majority undermines the well-
established distinction our precedents draw between Chev-
ron and less deferential forms of judicial review.
The broader implication of today’s decision is more unfor-
tunate still. The CAA is not the only statute that relies
on a close and equal partnership between federal and state
authorities to accomplish congressional objectives. See,
e. g., New York v. United States, 505 U. S., at 167 (listing
examples). Under the majority’s reasoning, these other
statutes, too, could be said to confer on federal agencies ulti-
mate decisionmaking authority, relegating States to the role
of mere provinces or political corporations, instead of coequal
sovereigns entitled to the same dignity and respect. Cf.
Alden v. Maine, 527 U. S. 706 (1999). If cooperative feder-
alism, Hodel v. Virginia Surface Mining & Reclamation
Assn., Inc., 452 U. S. 264, 289 (1981), is to achieve Con-
gress’ goal of allowing state governments to be accountable
to the democratic process in implementing environmental
policies, federal agencies cannot consign States to the minis-
terial tasks of information gathering and making initial rec-
ommendations, while reserving to themselves the authority
to make final judgments under the guise of surveillance and
oversight.
For these reasons, and with all respect, I dissent from the
opinion and the judgment of the Court.