                            PUBLISHED

UNITED STATES COURT OF APPEALS
                FOR THE FOURTH CIRCUIT


1000 FRIENDS OF MARYLAND,              
                       Petitioner,
                 v.
CAROL M. BROWNER, in her official
capacity as Administrator, U.S.
Environmental Protection Agency;
THE UNITED STATES ENVIRONMENTAL
PROTECTION AGENCY,                              No. 00-1489
                       Respondents,
BWI BUSINESS PARTNERSHIP,
INCORPORATED,
                       Intervenor,
ADVOCATES FOR SAFE AND EFFICIENT
TRANSPORTATION,
                   Amicus Curiae.
                                       
                On Petition for Review of an Order
             of the Environmental Protection Agency.

                         Argued: April 2, 2001

                      Decided: September 11, 2001

      Before LUTTIG and TRAXLER, Circuit Judges, and
   Lacy H. THORNBURG, United States District Judge for the
    Western District of North Carolina, sitting by designation.



Petition denied by published opinion. Judge Traxler wrote the opin-
ion, in which Judge Luttig and Judge Thornburg joined.
2              1000 FRIENDS OF MARYLAND v. BROWNER
                             COUNSEL

ARGUED: Jeffrey Herrema, Student Attorney, Wade Wilson, Stu-
dent Attorney, Environmental Law Clinic, UNIVERSITY OF
MARYLAND SCHOOL OF LAW, Baltimore, Maryland, for Peti-
tioner. David Jay Kaplan, Environment & Natural Resources Divi-
sion, Environmental Defense Section, UNITED STATES
DEPARTMENT OF JUSTICE, Washington, D.C., for Respondents.
ON BRIEF: Rena I. Steinzor, Brian Higgins, Student Attorney, Envi-
ronmental Law Clinic, UNIVERSITY OF MARYLAND SCHOOL
OF LAW, Baltimore, Maryland, for Petitioner. John Cruden, Acting
Assistant Attorney General, David Gualtieri, Environment & Natural
Resources Division, Environmental Defense Section, UNITED
STATES DEPARTMENT OF JUSTICE, Washington, D.C.; Sara
Schneeberg, Office of General Counsel, ENVIRONMENTAL PRO-
TECTION AGENCY, Washington, D.C.; Cecil A. Rodrigues, Office
of Regional Counsel-Region III, ENVIRONMENTAL PROTEC-
TION AGENCY, Philadelphia, Pennsylvania, for Respondents. Nor-
man W. Fichthorn, Allison D. Wood, Virginia S. Albrecht, HUNTON
& WILLIAMS, Washington, D.C.; Michael C. Powell, GORDON,
FEINBLATT, ROTHMAN, HOFFBERGER & HOLLANDER,
L.L.C., Baltimore, Maryland, for Intervenor. David M. Friedland, Gus
B. Bauman, David M. Williamson, BEVERIDGE & DIAMOND,
P.C., Washington, D.C., for Amicus Curiae.


                             OPINION

TRAXLER, Circuit Judge:

  1000 Friends of Maryland (the "Petitioner"), a citizens group "com-
mitted to the advocacy of wise land use policies that will abate envi-
ronmental problems throughout Maryland," Brief of Petitioner at 1,
seeks judicial review under the Clean Air Act of a final action taken
by the Environmental Protection Agency ("EPA") in connection with
Baltimore’s efforts to comply with the Clean Air Act’s ozone require-
ments. We deny the petition for review.1
    1
  Briefs in support of the EPA’s position have been filed by intervenor
BWI Business Partnership, Inc. ("BWI"), which "promot[es] economic
                1000 FRIENDS OF MARYLAND v. BROWNER                     3
                       I. Statutory Framework

   The Clean Air Act, 42 U.S.C.A. §§ 7401 et seq. (West 1995 &
Supp. 2001) (sometimes the "CAA" or the "Act"), is a comprehensive
program for controlling and improving the nation’s air quality. Under
the CAA, the EPA identifies air pollutants that endanger the public
health or welfare, determines what concentrations of those pollutants
are safe, and promulgates those determinations as national ambient air
quality standards ("NAAQS"). See 42 U.S.C.A. §§ 7408, 7409. Each
state bears responsibility for ensuring that its ambient air meets the
appropriate NAAQS. See 42 U.S.C.A. § 7407(a). Ozone is one of the
pollutants identified and regulated by the EPA.2 See 40 C.F.R. § 50.9
(2001).3

   States must establish a state implementation plan ("SIP") that pro-
vides "for implementation, maintenance, and enforcement" of the
EPA’s air quality standards. 42 U.S.C.A. § 7410(a)(1). The Clean Air
Act requires SIPs to include "enforceable emission limitations and
other control measures, means, or techniques, . . . as well as schedules

development and transportation management in the region surrounding
the Baltimore/Washington International Airport," Brief of Intervenor,
Disclosure Statement, and amicus curiae Advocates for Safe and Effi-
cient Transportation ("ASET"), "a coalition of national trade associations
representing the transportation building industry, home builders, builders
of roadways and public transit, designers and consultants, transportation
agency officials, suppliers of building materials, and labor," Brief of
Amicus Curiae at 1.
   2
     Upper atmospheric ozone is beneficial in that it forms a protective
layer in the stratosphere that blocks harmful forms of ultraviolet radia-
tion. See Final Rule on Ozone Transport Commission, 60 Fed. Reg.
4712, 4712 n.1 (Jan. 24, 1995). Ground level ozone, however, which
forms through the reaction of volatile organic compounds and oxides of
nitrogen in the presence of heat and sunlight, is very harmful to human
health. See id.; Virginia v. United States, 74 F.3d 517, 519 (4th Cir.
1996).
   3
     This case involves Maryland’s efforts to attain the "1-hour" ozone
standard. See 40 C.F.R. § 50.9(a). The EPA’s proposed "8-hour" ozone
standard, which the Supreme Court recently considered in Whitman v.
American Trucking Ass’ns, Inc., 121 S. Ct. 903 (2001), is not at issue
here.
4                 1000 FRIENDS OF MARYLAND v. BROWNER
and timetables for compliance" to meet the NAAQS. 42 U.S.C.A.
§ 7410(a)(2)(A). States submit their SIPs to the EPA for approval,
and the states must revise their plans "as may be necessary to take
account of [NAAQS] revisions," 42 U.S.C.A. § 7410(a)(2)(H)(i), or
whenever the EPA determines that a SIP is "substantially inadequate
to attain" the NAAQS. 42 U.S.C.A. § 7410(a)(2)(H)(ii).

   Areas that do not meet the relevant air quality standards are known
as "nonattainment areas." 42 U.S.C.A. § 7407(d)(1)(A)(i). As to
attainment of the ozone NAAQS, the CAA establishes five levels of
nonattainment classifications—marginal, moderate, serious, severe,
and extreme—based upon how close the area comes to meeting the
standard. See 42 U.S.C.A. § 7511(a)(1). The Act imposes progres-
sively stringent requirements on areas falling within each nonattain-
ment classification. Baltimore is classified as a severe ozone
nonattainment area and must attain the ozone NAAQS no later than
November 15, 2005.

   States with serious, severe, or extreme nonattainment areas must
submit to the EPA for approval certain revisions to their SIPs, includ-
ing "attainment demonstrations" which show how each nonattainment
area will achieve the ozone NAAQS by the appropriate date. See 42
U.S.C.A. §§ 7511a(c)(2)(A), 7511a(d). Attainment demonstrations
"must be based on photochemical grid modeling or any other analyti-
cal method determined by the Administrator, in the Administrator’s
discretion, to be at least as effective." 42 U.S.C.A. § 7511a(c)(2)(A).4

  To satisfy the statutory requirements, the EPA requires attainment
SIPs to

        contain an inventory of current NAAQS pollutant emissions,
    4
   Photochemical grid modeling is a form of computer air quality model-
ing that evaluates how emissions from various sources combine in the
atmosphere and predicts the concentration of pollutants that likely will
result. The modeling technique uses "complex computer models that
consider monitoring data, meteorology, projected growth in the area,
planned emissions reductions, and other factors to predict the ambient
level of ozone as of the relevant area’s attainment date." Brief of Respon-
dents at 6.
               1000 FRIENDS OF MARYLAND v. BROWNER                    5
    as well as air quality modeling which demonstrates that[,]
    given certain assumptions about population growth, eco-
    nomic growth, and growth in vehicle miles traveled (VMT),
    the SIP’s control measures will result by a certain date in a
    level of emissions which is in attainment with the NAAQS.

Criteria for Determining Conformity, 58 Fed. Reg. 3768, 3769 (pro-
posed Jan. 11, 1993). This level of emissions yielded after implemen-
tation of the SIP control strategies is referred to by the EPA as an
"emissions budget." Id.

   States with serious, severe, or extreme ozone nonattainment areas
must also submit SIP revisions that show the area is making "reason-
able further progress" towards reaching attainment. See 42 U.S.C.A.
§ 7511a(c)(2)(B). Section 7511a(c)(2)(B) requires that the states
"demonstrate in the SIP that emissions of volatile organic compounds
(VOC) will be reduced by 15% from 1990 baseline emissions by
1996," and that "in milestone years occurring every three years from
1996 until the attainment date, VOC will be reduced from baseline
emissions by an average of three percent per year." 58 Fed. Reg. at
3769. "The [reasonable further progress] requirements in effect create
an emissions budget for each milestone year, in addition to the budget
that applies for the attainment year." Id.

   Motor vehicle emissions are major contributors to ozone pollution.
See Virginia v. United States, 74 F.3d 517, 520 (4th Cir. 1996)
("[A]utomobile exhaust, as a source of both [volatile organic com-
pounds] and nitrogen oxides, is a major cause of increased ozone
levels."); Michael R. Yarne, Conformity as Catalyst: Environmental
Defense Fund v. Environmental Protection Agency, 27 Ecology L.Q.
841, 846 (2000) (noting that light- and heavy-duty vehicles emit a
large percentage of the precursors that form to create ozone). Thus,
effective control of ozone pollution requires consideration and regula-
tion of vehicle emissions.

   The EPA requires that the emissions budgets established in attain-
ment demonstrations and demonstrations of reasonable further prog-
ress include a quantitative motor vehicle emissions budget, which
establishes the "portion of the total allowable emissions defined in the
submitted or approved control strategy implementation plan revision
6                  1000 FRIENDS OF MARYLAND v. BROWNER
. . . allocated to highway and transit vehicle use and emissions." 40
C.F.R. § 93.101. According to the EPA, "[a] SIP cannot effectively
demonstrate attainment unless it identifies the level of motor vehicle
emissions that can be produced while still demonstrating attainment."
Approval and Promulgation of Air Quality Implementation Plans, 64
Fed. Reg. 70,397, 70,402 (proposed Dec. 16, 1999).

   Given the relationship between motor vehicle emissions and ozone
pollution, the Clean Air Act also includes certain "conformity" provi-
sions that "integrate[ ] the Clean Air Act with the transportation plan-
ning process by conditioning federal approval and funding of
transportation activities on their demonstrated compliance with appli-
cable SIPs." Sierra Club v. EPA, 129 F.3d 137, 138 (D.C. Cir. 1997).

   Pursuant to the conformity provisions, no federal "department,
agency, or instrumentality" may "engage in, support in any way or
provide financial assistance for, license or permit, or approve, any
activity which does not conform to an implementation plan after it has
been approved." 42 U.S.C.A. § 7506(c)(1). An activity "conforms" to
the applicable SIP only if the activity is consistent with the SIP’s
"purpose of eliminating or reducing the severity and number of viola-
tions of the [NAAQS] and achieving expeditious attainment of such
standards," 42 U.S.C.A. § 7506(c)(1)(A), and if the activity will not

          (i) cause or contribute to any new violation of any stan-
        dard in any area;

           (ii) increase the frequency or severity of any existing vio-
        lation of any standard in any area; or

          (iii) delay timely attainment of any standard or any
        required interim emission reductions or other milestones in
        any area.

42 U.S.C.A. § 7506(c)(1)(B).

  The Clean Air Act also requires a state’s transportation plans and
programs5 to be consistent with the applicable SIP by providing that
    5
   Federal law generally requires the designation of a metropolitan plan-
ning organization ("MPO") for each urban area with a population of
                 1000 FRIENDS OF MARYLAND v. BROWNER                        7
state officials may not adopt a transportation plan or program, nor
find such a plan or program to be in conformity, "until a final deter-
mination has been made that emissions expected from implementation
of such plans and programs are consistent with estimates of emissions
from motor vehicles and necessary emissions reductions contained in
the applicable implementation plan." 42 U.S.C.A. § 7506(c)(2)(A).
Federal agencies may not "approve, accept or fund any transportation
plan, program or project" unless it conforms to the applicable SIP. Id.
§ 7506(c)(2).

   As required by section 7506(c)(4), the EPA promulgated regula-
tions establishing criteria and procedures for determining conformity.
These regulations provide that the motor vehicle emissions budget
("MVEB") contained in the attainment and reasonable further prog-
ress SIPs will be used to make the conformity determination, and the
regulations set forth certain criteria against which an MVEB is mea-
sured. See 40 C.F.R. § 93.118(e)(4). If the EPA determines an MVEB
to be adequate under the regulations, the MVEB may be relied upon
by agency heads when determining whether a proposed transportation
project conforms to the relevant SIP, even though the SIP containing
the MVEB has yet to be approved by the EPA. The EPA’s use of
these adequacy regulations are at the heart of this dispute.

                         II. Procedural History

   In April 1998, Maryland submitted to the EPA its attainment dem-
onstration SIP revision for the Baltimore area (the "Attainment SIP")
to show that the area was on track to reduce its emissions and timely
attain the ozone NAAQS. The Attainment SIP included the required

more than 50,000. See 49 U.S.C.A. § 5303(c)(1). The MPO "develops a
long range transportation plan . . . which specifies the facilities, services,
financing techniques, and management policies that will comprise the
area’s transportation system over a 20-year period." Environmental Def.
Fund v. EPA, 167 F.3d 641, 644 (D.C. Cir. 1999); see 49 U.S.C.A.
§ 5303(f). The MPO must also develop a "short-term transportation
improvement program . . . which identifies and prioritizes the specific
transportation projects to be carried out over the next three years." Envi-
ronmental Def. Fund, 167 F.3d at 644; see 49 U.S.C.A. § 5304(b).
8                1000 FRIENDS OF MARYLAND v. BROWNER
photochemical    grid modeling, which showed that some peak ozone
concentrations   would exceed attainment levels. It also included a
motor vehicle    emissions budget (the "initial MVEB") for the year
2005, the year   Baltimore is required to attain the ozone NAAQS.

   On October 26, 1999, the EPA determined that the initial MVEB
was not adequate for conformity purposes. See 64 Fed. Reg. at
70,409. The EPA concluded that the budget was not adequate
because, among other things, it failed to account for certain emission
reductions that would be produced by various previously imple-
mented nationwide regulatory programs. As to the Attainment SIP,
the EPA proposed to approve it if, among other things, Maryland
committed to adopt additional control measures that the EPA believed
were necessary to reach attainment and if Maryland submitted a
revised, adequate MVEB. The EPA concluded, however, that Mary-
land’s submitted Attainment SIP contained modeling that satisfied the
statutory requirements and that new modeling would not be required
with the submission of the required revisions. See id. at 70,407.

   Shortly after the EPA found the initial MVEB inadequate, Mary-
land submitted a revised motor vehicle emissions budget for the Balti-
more area. The revised budget used updated fleet registration data
(information about the types and numbers of vehicles in use) that
showed more vehicles in use and higher emissions per vehicle mile
traveled. Therefore, even though the budget incorporated (as required
by the EPA) the expected emissions reductions produced by the previ-
ously implemented nationwide programs, the revised budget was
higher than the initial MVEB found inadequate by the EPA.

   The EPA posted information about Baltimore’s revised MVEB on
its website and requested public comment. The only comments
received were from the Petitioner. After considering the Petitioner’s
comments, the EPA determined that the revised MVEB, considered
with all other emissions budgets, was consistent with attainment, even
though it was higher than the initial budget. The EPA therefore con-
cluded that the revised budget was adequate for conformity purposes.

  The Petitioner then filed this action, seeking review of the EPA’s
determination that the revised MVEB was adequate for conformity
purposes. The Petitioner contends that the EPA violated the Clean Air
                1000 FRIENDS OF MARYLAND v. BROWNER                        9
Act by finding the revised MVEB adequate without requiring addi-
tional photochemical grid modeling. The Petitioner also contends that
the adequacy determination must be vacated because the EPA failed
to sufficiently explain why the revised budget was adequate.

                              III. Analysis

   Before considering the merits of the Petitioner’s claims, we must
first address the assertions of the EPA, BWI, and ASET that, for vari-
ous jurisdictional and prudential reasons, this action should be dis-
missed.

                                     A.

   The Clean Air Act establishes a rather complicated system of judi-
cial review. The Act provides that a petition for review of any "na-
tionally applicable regulations" is to be "filed only in the United
States Court of Appeals for the District of Columbia" within 60 days
of notice of promulgation, and that a petition for review of "any other
final action of the Administrator . . . which is locally or regionally
applicable may be filed only in the United States Court of Appeals for
the appropriate circuit." 42 U.S.C.A. § 7607(b)(1).

   The EPA contends that the Petitioner in reality is challenging the
legality of the MVEB adequacy regulations themselves, a challenge
that the Clean Air Act requires to have been brought in the Court of
Appeals for the D.C. Circuit within 60 days after promulgation of the
regulations. Because the adequacy regulations were promulgated sev-
eral years ago, the EPA claims that this court lacks jurisdiction over
the action because it was filed too late and in the wrong court. We dis-
agree.6
  6
   Given our disposition of this issue, it matters not whether section
7607(b) is properly viewed as a jurisdictional provision or merely one
establishing venue. Compare, e.g., Texas Mun. Power Agency v. EPA, 89
F.3d 858, 866-67 (D.C. Cir. 1996) (concluding that 60-day time limit of
section 7607(b) is jurisdictional, but that portion requiring certain actions
to be filed with the D.C. Circuit merely establishes venue), with Monon-
gahela Power Co. v. Reilly, 980 F.2d 272, 275 (4th Cir. 1993) (treating
section 7607(b)’s allocation between the D.C. Circuit and the "appropri-
ate circuit" as jurisdictional).
10             1000 FRIENDS OF MARYLAND v. BROWNER
   Contrary to the EPA’s argument, the Petitioner is not challenging
the legality of the adequacy regulations in a way that would affect
whether the petition for review is properly before us. Certainly the
Petitioner is unhappy with the EPA’s use of the regulations when
finding the revised MVEB to be adequate for conformity purposes.
But the Petitioner’s real argument is not that the adequacy regulations
are illegal in and of themselves, but that the EPA in this case acted
contrary to the dictates of the Clean Air Act when it found the revised
budget to be adequate without requiring what the Petitioner perceives
to be statutorily mandated additional photochemical grid modeling.
That the Petitioner might complain generally about the adequacy reg-
ulations when what it seeks is reversal of a final, locally applicable
agency action does not make this action one that must be brought in
the D.C. Circuit. See Illinois Envtl. Prot. Agency v. EPA, 947 F.2d
283, 288-89 (7th Cir. 1991) (concluding that state agency could chal-
lenge as a final action the EPA’s application of a set-aside regulation
to the state agency, notwithstanding the state agency’s failure to chal-
lenge the regulation in the D.C. Circuit when the regulation was pro-
mulgated). We therefore reject the EPA’s argument that we lack
jurisdiction over this petition for review.

                                  B.

  Intervenor BWI suggests that this petition for review is premature
because there has been no final agency action. We disagree.

   The Clean Air Act authorizes judicial review of final actions of the
Administrator. See 42 U.S.C.A. § 7607(b)(1). This grant of jurisdic-
tion incorporates the finality requirements of the Administrative Pro-
cedures Act. See Whitman v. American Trucking Ass’ns, Inc., 121
S. Ct. 903, 915 (2001).

   When determining whether an agency action is final for purposes
of judicial review, the focus is not on the label attached to the action
but on the nature of the action. To be final, "the action under review
[must] mark the consummation of the agency’s decisionmaking pro-
cess." Id. (internal quotation marks omitted). That standard is clearly
satisfied here. The EPA has reviewed the revised MVEB and found
it to be adequate for purposes of making conformity determinations,
thus opening the door to the approval, funding, and construction of
                1000 FRIENDS OF MARYLAND v. BROWNER                   11
transportation projects that conform to the budget. Although the EPA,
when determining whether to approve Maryland’s Attainment SIP,
will continue to consider the overall sufficiency of the SIP, it has ren-
dered its final decision as to the adequacy of the MVEB for confor-
mity purposes. The action is therefore final for purposes of review
under section 7607(b)(1). See id. ("Only if the EPA has rendered its
last word on the matter in question is its action final and thus review-
able." (citation and internal quotation marks omitted)); COMSAT
Corp. v. National Sci. Found., 190 F.3d 269, 274 (4th Cir. 1999)
("[A]n agency action may be considered ‘final’ only when the action
signals the consummation of an agency’s decisionmaking process and
gives rise to legal rights or consequences.").

   BWI, however, contends that if the Petitioner is not challenging the
legality of the adequacy regulations themselves, then the Petitioner
must really be complaining about the EPA’s announced intention to
approve Maryland’s Attainment SIP if Maryland complies with cer-
tain conditions, see 64 Fed. Reg. 70,397, which BWI contends is not
a final action. In our view, BWI’s characterization of the Petitioner’s
challenge is wide of the mark. As discussed above, the Petitioner
seeks a reversal of the EPA’s determination that the revised MVEB
was adequate, a determination that is final and ripe for judicial
review. While the Petitioner might also object to what appears to be
the impending approval of the Attainment SIP, that objection does not
prevent it from challenging the adequacy determination.

                                   C.

   Amicus ASET contends that this case should be dismissed because
the Petitioner lacks standing. We disagree.

   "[A]n association may have standing to sue in federal court either
based on an injury to the organization in its own right or as the repre-
sentative of its members who have been harmed." Friends of the
Earth, Inc. v. Gaston Copper Recycling Corp., 204 F.3d 149, 155 (4th
Cir. 2000) (en banc). Representational standing is established if "(1)
at least one of [the organization’s] members would have standing to
sue in his own right; (2) the organization seeks to protect interests
germane to the organization’s purpose; and (3) neither the claim
asserted nor the relief sought requires the participation of individual
12              1000 FRIENDS OF MARYLAND v. BROWNER
members in the lawsuit." Id.; see Hunt v. Washington State Apple
Adver. Comm’n, 432 U.S. 333, 343 (1977). The only real dispute in
this case centers around the first prong of the inquiry—whether an
individual member would have standing.

  To establish "the irreducible constitutional minimum of standing,"
Lujan v. Defenders of Wildlife, 504 U.S. 555, 560 (1992), an individ-
ual plaintiff must demonstrate that:

     (1) it has suffered an "injury in fact" that is (a) concrete and
     particularized and (b) actual or imminent, not conjectural or
     hypothetical; (2) the injury is fairly traceable to the chal-
     lenged action of the defendant; and (3) it is likely, as
     opposed to merely speculative, that the injury will be
     redressed by a favorable decision.

Friends of the Earth, Inc. v. Laidlaw Envtl. Servs. (TOC), Inc., 528
U.S. 167, 180-81 (2000).

   The Petitioner and its members have an interest in preventing ill-
conceived transportation projects from increasing the level of motor
vehicle emissions pollution to which the members are exposed.
According to the Petitioner, the EPA "approved" a motor vehicle
emissions budget that is too high to allow Baltimore to reach attain-
ment of the ozone NAAQS, thus opening the door to the construction
of transportation projects that will prevent Baltimore from attaining
the NAAQS and will subject the Petitioner’s members to continued
exposure to ozone above levels determined to be safe by the EPA.
Although the transportation projects will not be built by the EPA, the
EPA’s determination that the revised MVEB was adequate was the
act that was required before any transportation projects could be con-
sidered by other agencies, and it is the adequacy finding that will
allow the construction of transportation projects that, according to the
Petitioner, will prevent Baltimore from attaining the ozone NAAQS.
See Gaston Copper, 204 F.3d at 154 ("The traceability prong means
it must be likely that the injury was caused by the conduct complained
of and not by the independent action of some third party not before
the court."). And if the adequacy finding were to be set aside by this
court, new transportation projects could not proceed until the develop-
ment of a new and adequate MVEB, thus reducing the amount of
                1000 FRIENDS OF MARYLAND v. BROWNER                   13
ozone pollution to which the Petitioner’s members would be exposed.
See id. at 162 ("The redressability requirement ensures that a plaintiff
personally would benefit in a tangible way from the court’s interven-
tion" (internal quotation marks omitted)).

   Given these circumstances, we conclude that the Petitioner has
alleged a sufficiently concrete, imminent injury that is fairly traceable
to the EPA’s action and that can be redressed in this action. We there-
fore conclude that any one of the Petitioner’s individual members
would have standing to maintain an action in his own right and that
the Petitioner thus has standing to bring this action. See Natural Res.
Def. Council v. EPA, 25 F.3d 1063, 1067 (D.C. Cir. 1994) (conclud-
ing that environmental group with "members [who] live in communi-
ties subject to incidents resulting from mismanagement of used oil"
has standing to challenge "the EPA’s failure to list used oils as a haz-
ardous waste" (internal quotation marks omitted)).

   ASET, however, also contends that the doctrine of judicial estoppel
should prevent the Petitioner from asserting that it has standing. After
the Petitioner filed this petition for review, ASET sought permission
from this court to intervene in the action. The Petitioner opposed the
intervention, arguing, inter alia, that ASET lacked standing. From
there ASET constructs the following argument: the Petitioner previ-
ously argued that ASET’s interests were insufficient to confer stand-
ing; the Petitioner’s interests in the case are even less concrete than
ASET’s interest; therefore, the Petitioner should be judicially estop-
ped from arguing that its interests are sufficient to confer standing.
We find this argument to be wholly without merit.

   "Judicial estoppel precludes a party from adopting a position that
is inconsistent with a stance taken in prior litigation. The purpose of
the doctrine is to prevent a party from playing fast and loose with the
courts, and to protect the essential integrity of the judicial process."
Lowery v. Stovall, 92 F.3d 219, 223 (4th Cir. 1996) (internal quotation
marks omitted). "Because the rule is intended to prevent improper use
of judicial machinery, judicial estoppel is an equitable doctrine
invoked by a court at its discretion." New Hampshire v. Maine, 121
S. Ct. 1808, 1815 (2001) (citation, brackets, and internal quotation
marks omitted)).
14              1000 FRIENDS OF MARYLAND v. BROWNER
   Although "the circumstances under which judicial estoppel may
appropriately be invoked are probably not reducible to any general
formulation of principle, . . . several factors typically inform the deci-
sion whether to apply the doctrine in a particular case." Id. (citations
and internal quotation marks omitted). In this circuit, we generally
require the presence of the following elements before we will apply
the doctrine of judicial estoppel:

        First, the party sought to be estopped must be seeking to
     adopt a position that is inconsistent with a stance taken in
     prior litigation. And the position sought to be estopped must
     be one of fact rather than law or legal theory.

       Second, the prior inconsistent position must have been
     accepted by the court. . . .

        Finally, the party sought to be estopped must have inten-
     tionally misled the court to gain unfair advantage.

Lowery, 92 F.3d at 224 (citations and internal quotation marks omit-
ted); accord Local Union 93, United Mineworkers of Am. v. Marrow-
bone Dev. Co., 232 F.3d 383, 390 (4th Cir. 2000).

   Preliminarily, we note that the ultimate question of whether a party
has standing is one of law, not fact. See Fund for Animals v. Babbitt,
89 F.3d 128, 132 (2nd Cir. 1996). Moreover, while this court denied
ASET’s motion to intervene (but granted it permission to participate
as amicus curiae), the denial was not premised on a conclusion that
ASET lacked standing, but instead on questions about the timeliness
of the petition to intervene and a concern that allowing ASET to inter-
vene would interfere with ongoing (but ultimately unsuccessful) set-
tlement efforts. These factors demonstrate that the application of
judicial estoppel would not be appropriate in this case. See New
Hampshire, 121 S. Ct. at 1815 ("Absent success in a prior proceeding,
a party’s later inconsistent position introduces no risk of inconsistent
court determinations and thus poses little threat to judicial integrity."
(citation and internal quotation marks omitted)); Lowery, 92 F.3d at
224 ("The insistence upon a court having accepted the party’s prior
inconsistent position ensures that judicial estoppel is applied in the
narrowest of circumstances."). Even without regard to these factors,
                1000 FRIENDS OF MARYLAND v. BROWNER                   15
however, this case simply does not involve the type of inconsistent
positions that the doctrine contemplates.

   The Petitioner is an environmental group, while ASET is a coali-
tion of various industries and business groups that derive economic
benefit from the construction of transportation projects. To understate
the obvious, the interests of environmental and business groups on
opposite sides of environmental litigation generally are dissimilar;
this case is no exception. The Petitioner’s members claim injury from
the approval and construction of transportation projects that they
believe will cause an increase in the level of harmful ozone pollution
in the Baltimore area. ASET’s members, however, claim they will
suffer economic injury if the construction of transportation projects is
improperly delayed. There is nothing inconsistent or unfair about the
Petitioner arguing (unsuccessfully) that ASET’s interests are not suf-
ficient to confer standing while at the same time arguing (success-
fully) that its own very different interests are sufficient to confer
standing. Accordingly, we decline to apply the doctrine of judicial
estoppel to prohibit the Petitioner from arguing that it has standing to
bring this petition for review.

                                   D.

   The last of the threshold questions about whether this court should
entertain the petition for review is the EPA’s waiver argument. The
EPA insists that the Petitioner may not challenge the EPA’s failure to
require additional photochemical grid modeling because it did not
raise that issue in its comments to the EPA. The EPA thus argues that
the Petitioner has waived the right to raise the issue before this court.

   "As a general matter, it is inappropriate for courts reviewing
appeals of agency decisions to consider arguments not raised before
the administrative agency involved." Pleasant Valley Hosp., Inc. v.
Shalala, 32 F.3d 67, 70 (4th Cir. 1994); see also Michigan Dep’t of
Envtl. Quality v. Browner, 230 F.3d 181, 183 n.1 (6th Cir. 2000)
(concluding that issues not raised during notice and comment period
were waived for purposes of appellate review). Courts typically
decline to consider issues not raised before an administrative agency
because to do otherwise would "usurp[ ] the agency’s function" and
would "deprive the [agency] of an opportunity to consider the matter,
16                1000 FRIENDS OF MARYLAND v. BROWNER
make its ruling, and state the reasons for its action." Unemployment
Comp. Comm’n v. Aragan, 329 U.S. 143, 155 (1946); see also United
States v. L.A. Tucker Truck Lines, Inc., 344 U.S. 33, 37 (1952)
("Simple fairness . . . requires as a general rule that courts should not
topple over administrative decisions unless the administrative body
not only has erred but has erred against objection made at the time
appropriate under its practice."). Assuming this rule applies to this case,7
we conclude that it does not bar the Petitioner’s challenge.

   We conclude that the comments made by the Petitioner sufficiently
raised the question of whether additional modeling was required upon
the submission of the revised MVEB. While the Petitioner’s com-
ments do not include a separately delineated section devoted to a
claim that the revised MVEB cannot be approved without additional
modeling and perhaps are phrased somewhat generally, the comments
nonetheless refer (at least implicitly) to photochemical grid modeling
three times, twice mentioning the process by name.8 Although the
  7
   In City of Seabrook, Texas v. EPA, 659 F.2d 1349 (Former 5th Cir.
1981), the court rejected the EPA’s claim that the petitioner’s failure to
object to a conditional SIP approval during the notice-and-comment pro-
cedure prevented it from challenging the action in court:
      The rule urged by EPA would require everyone who wishes to
      protect himself from arbitrary agency action not only to become
      a faithful reader of the notices of proposed rulemaking published
      each day in the Federal Register, but a psychic able to predict
      the possible changes that could be made in the proposal when the
      rule is finally promulgated. This is a fate this court will impose
      on no one.
Id. at 1360-61 (footnote omitted). The court described as "badly mis-
placed" the EPA’s reliance on cases like L.A. Tucker Truck Lines, which
involved appeals by a party to an essentially adversarial administrative
proceeding, where a hearing was held and evidence was received. Id. at
1361 n.17; accord American Forest & Paper Ass’n v. EPA, 137 F.3d
291, 295-96 (5th Cir. 1998). The waiver rule, however, has been rather
routinely applied in cases similar to this one. See, e.g., Michigan Dep’t
of Envtl. Quality, 230 F.3d at 183 n.1; Military Toxics Project v. EPA,
146 F.3d 948, 956-57 (D.C. Cir. 1998); Natural Res. Def. Council, 25
F.3d at 1073-74.
  8
    See J.A. F-13 ("[T]he attainment year budget should be subjected to
a photochemical grid modeling analysis, as required by the CAA, before
                1000 FRIENDS OF MARYLAND v. BROWNER                     17
Petitioner stated in its comments that the modeling question would be
"addressed more comprehensively" in other comments directed to
another EPA action, this statement does not, as the EPA contends,
suggest that the Petitioner was expressly declining to raise the issue
in this action. Instead, the statement merely placed the EPA on notice
that the issue would also be raised in connection with the other action.
We therefore conclude that the Petitioner’s comments sufficiently
raised the question of whether additional modeling was required
before the revised MVEB could be deemed adequate, and we now
proceed to address the merits of this question.

                                   IV.

   The Petitioner’s primary argument is that various provisions of the
Clean Air Act unambiguously require a revision to a motor vehicle
emissions budget to be supported by photochemical grid modeling or
a similarly effective analytical method. The Petitioner therefore con-
tends that the EPA violated the Clean Air Act by finding Baltimore’s
revised MVEB to be adequate for conformity purposes without
requiring the performance of additional modeling. The EPA, how-
ever, contends that its actions were proper and not inconsistent with
the commands of the Clean Air Act.

   Final actions of the EPA under the Clean Air Act are reviewed
according to the familiar standards of the Administrative Procedures
Act, which requires us to uphold an agency action unless the action
was "arbitrary, capricious, an abuse of discretion, or otherwise not in
accordance with law." 5 U.S.C.A. § 706(2)(A) (West 1996); see Vir-
ginia v. Browner, 80 F.3d 869, 876 (4th Cir. 1996) (applying the APA
standard to the EPA’s disapproval of a state implementation plan); see
also Sierra Club v. EPA, 252 F.3d 943, 946-47 (8th Cir. 2001) (apply-
ing the APA standard to approval of a state implementation plan);

it is determined adequate for conformity purposes for the attainment year
and beyond."); J.A. F-26 ("[T]he 2005 budget . . . must be analyzed with
respect to the entire SIP in a photochemical grid modeling process, or its
equivalent."); Id. ("The point here is that [Maryland] cannot . . . plow
through the SIP revision process without fulfilling its legal obligation to
conduct the analyses necessary to determine whether the proposed
MVEBs will interfere with . . . attainment requirements.").
18              1000 FRIENDS OF MARYLAND v. BROWNER
Ober v. Whitman, 243 F.3d 1190, 1193 (9th Cir. 2001) (applying the
APA standard to the EPA’s exemption in a federal implementation
plan of certain "de minimis" sources of pollution). When determining
whether the agency action is "in accordance with law," we defer to
the agency’s reasonable interpretation of the statute it administers "if
the statute is silent or ambiguous with respect to the specific issue."
Chevron, U.S.A., Inc. v. Natural Res. Def. Council, Inc., 467 U.S.
837, 843 (1984).

                                    A.

   If the Petitioner is correct in asserting that EPA’s action violated
the plain language of the Clean Air Act, then the action of course
must be aside under section 706(2)(A) of the APA. See, e.g., Citizens
Awareness Network, Inc. v. United States Nuclear Regulatory
Comm’n, 59 F.3d 284, 290 (1st Cir. 1995) (noting that review under
the APA is narrow and that "agency decisions will be upheld so long
as they do not collide directly with substantive statutory commands"
(internal quotation marks omitted)); cf. Chevron, 467 U.S. at 842-43
(explaining that if "Congress has directly spoken to the precise ques-
tion at issue," then "that is the end of the matter; for the court, as well
as the agency, must give effect to the unambiguously expressed intent
of Congress"). It is to this question that we now turn.

                                   (1)

   The Petitioner first contends that, read together, sections
7410(a)(2)(I) and 7511a(c)(2)(A) of the Clean Air Act clearly require
new modeling to be performed upon the submission of a revised
MVEB. Section 7511a(c)(2)(A), which is found in "Part D" of the
Act, is the provision that requires states with certain nonattainment
areas to submit attainment demonstrations based on photochemical
grid modeling. Section 7410(a)(2)(I) requires SIPs and SIP revisions
for nonattainment areas to meet the requirements of Part D. See 42
U.S.C.A. § 7410(a)(2)(I) (stating that a "plan or plan revision for an
area designated as a nonattainment area" must "meet the applicable
requirements of part D of this subchapter (relating to nonattainment
areas)"). The Petitioner argues that the MVEB is a critical component
of an attainment demonstration and that, pursuant to section
               1000 FRIENDS OF MARYLAND v. BROWNER                   19
7410(a)(2)(I), the revision of the budget thus required new modeling
to be performed.

   Although we harbor some doubt, we will assume for purposes of
this opinion that the revision of the MVEB was a "plan revision"
within the meaning of section 7410(a)(2)(I). Accepting this argument,
however, does not require us to accept the Petitioner’s ultimate argu-
ment that the EPA’s adequacy determination in the absence of new
modeling violated the Clean Air Act.

   Section 7511a(c)(2)(A) requires attainment demonstrations to be
supported by sufficient computer modeling, but it does not establish
the time frame for that modeling. That is, the statute does not say that
modeling must be performed within a certain number of days from
the submission of the attainment SIP, nor does it say that new model-
ing must be performed in connection with every revision to an attain-
ment SIP. Instead, it simply requires that the modeling demonstrate
"that the plan, as revised, will provide for attainment of the ozone
national ambient air quality standard" and that the demonstration be
"based on photochemical grid modeling." 42 U.S.C.A.
§ 7511a(c)(2)(A). Nothing in this section prohibits the use of previ-
ously performed modeling if that modeling can show that the plan as
revised will allow the area to reach attainment. See, e.g., Carbon Fuel
Co. v. USX Corp., 100 F.3d 1124, 1133 (4th Cir. 1996) ("Under the
most basic canon of statutory construction, we begin interpreting a
statute by examining the literal and plain language of the statute.").

   Since section 7511a(c)(2)(A) does not, as a matter of statutory con-
struction, require the performance of new modeling upon the submis-
sion of any SIP revision (a requirement that is critical to the success
of the Petitioner’s claim), then section 7410(a)(2)(I) adds nothing to
the mix. Section 7410(a)(2)(I) simply requires SIP revisions to com-
ply with the applicable Part D requirements; it does not require that
each of the Part D requirements must be performed anew with each
SIP revision.

   We are thus left with the conclusion that while section
7511a(c)(2)(A) requires SIPs and SIP revisions in certain nonattain-
ment areas to demonstrate attainment through the use of photochemi-
cal grid modeling (or its equivalent), it does not prevent the use of
20             1000 FRIENDS OF MARYLAND v. BROWNER
previously performed modeling to show attainment. Whether any
such previously performed modeling in fact demonstrates attainment
in any given case would be a question for the EPA to determine in
the course of its review and approval (or disapproval) of the SIP or
SIP revision. The reasonableness of that determination, however, is
completely separate from the question of whether the Clean Air Act
requires new modeling upon the revision of a SIP or any of its com-
ponents.

                                  (2)

   The Petitioner also contends that its position is supported by the
provisions of the Act regarding what is known as a "SIP call," the
process by which the EPA notifies the states of deficiencies in sub-
mitted plans and directs the submission of revised plans. See 42
U.S.C.A. § 7410(k)(5); see generally Clean Air Implementation Proj-
ect v. EPA, 150 F.3d 1200, 1207 (D.C. Cir. 1998). Under the EPA’s
general SIP call authority, the EPA may decide the extent to which
the revision must satisfy the Act’s SIP requirements. See 42 U.S.C.A.
§ 7410(k)(5) ("Any finding [of plan inadequacy] under this paragraph
shall, to the extent the Administrator deems appropriate, subject the
State to the requirements of this chapter to which the State was sub-
ject when it developed and submitted the plan for which such finding
was made . . . ." (emphasis added)). Revisions submitted in response
to SIP calls in nonattainment areas, however, "must correct the plan
deficiency (or deficiencies) specified by the Administrator and meet
all other applicable plan requirements of section 7410 of this title and
this part." 42 U.S.C.A. § 7502(d).

   The Petitioner argues that since revisions to a plan in a nonattain-
ment area after a SIP call must meet all other applicable requirements,
including the Part D requirements, then the EPA’s requirement that
Maryland revise the MVEB must likewise be understood to trigger
the Part D requirements. This argument, however, does not help the
Petitioner, because, as we have explained, the Part D modeling provi-
sion does not require that new modeling be performed every time
there is a revision to a SIP.

                                  (3)

  The Petitioner also contends that the conformity provisions of the
Act require that conformity determinations be made by reference to
               1000 FRIENDS OF MARYLAND v. BROWNER                   21
an approved SIP. Because the revised MVEB is part of a submitted,
but not yet approved, SIP revision, the Petitioner contends that the
adequacy determination, which allows the budget to be used for con-
formity purposes, violates the requirement that conformity be based
on an approved SIP. We disagree.

   To be sure, the conformity provisions of the Clean Air Act do
appear to contemplate that conformity determinations will be made
with regard to approved plans. See 42 U.S.C.A. § 7506(c)(1) (prohib-
iting federal agency from approving or supporting "any activity which
does not conform to an implementation plan after it has been
approved"); id. § 7506(c)(2) ("No Federal agency may approve,
accept or fund any transportation plan, program or project unless such
plan, program or project has been found to conform to any applicable
implementation plan . . . ." (emphasis added)); id. § 7602(q) (defining
"applicable implementation plan" as "the portion (or portions) of the
implementation plan, or most recent revision thereof, which has been
approved under section 7410 of this title" (emphasis added)). That the
statute seems to contemplate the use of approved plans, however,
does not resolve the question.

   Although the phrase "motor vehicle emissions budget" is not used
in the conformity provisions, it is nonetheless clear that to comply
with section 7506(c), conformity determinations must be based on
those budgets. See 42 U.S.C.A. § 7506(c)(2)(A) (requiring consis-
tency with "estimates of emissions from motor vehicles and necessary
emissions reductions contained in the applicable implementation
plan"); id. § 7506(c)(2)(D) (explaining that certain transportation
projects will be found to conform only if, inter alia, the project
"do[es] not cause such plans and programs to exceed the emission
reduction projections and schedules assigned to such plans and pro-
grams in the applicable implementation plan"). Not all SIPs, however,
contain motor vehicle emissions budgets. Generally, only those SIPs
that the EPA refers to as "control strategy" SIPs—attainment demon-
stration SIPs and "reasonable further progress" SIPs—contain suffi-
ciently quantified MVEBs. See 40 C.F.R. § 93.101 (defining "motor
vehicle emissions budget" as "that portion of the total allowable emis-
sions defined in the submitted or approved control strategy implemen-
tation plan revision . . . for a certain date for the purpose of meeting
reasonable further progress milestones or demonstrating attainment
22              1000 FRIENDS OF MARYLAND v. BROWNER
. . . of the NAAQS for any criteria pollutant or its precursor, allocated
to highway and transit vehicle use and emissions"); id. (defining
"control strategy implementation plan revision" as "the implementa-
tion plan which contains specific strategies for controlling the emis-
sions of and reducing ambient levels of pollutants in order to satisfy
CAA requirements for demonstrations of reasonable further progress
and attainment").

   In addition, while the Clean Air Act required SIP revisions demon-
strating attainment and reasonable further progress to be submitted by
November 15, 1994, see 42 U.S.C.A. § 7511a(c)(2), many states were
unable to meet this deadline because of problems caused by "ozone
transport." See 64 Fed. Reg. at 70,398; see also Virginia v. EPA, 108
F.3d 1397, 1400 (D.C. Cir. 1997) (explaining that ozone transport is
a process through which precursor emissions and ozone-laden air
from one area move downwind, thus contributing to the ozone prob-
lems of another area). Because of these problems, the EPA ultimately
extended until April 1998 the deadline for serious and severe nonat-
tainment areas to submit their attainment demonstrations. See 64 Fed.
Reg. at 70,398.9

   Because not all SIPs contain MVEBs and because of the delay in
the submission and approval of attainment demonstrations that do
contain such budgets, it is entirely possible that some nonattainment
areas subject to the conformity requirements may not have in place
an approved SIP containing a MVEB. While the Clean Air Act gener-
ally contemplates that conformity determinations will be made by ref-
erence to approved SIPs, the Act simply does not address how
conformity determinations should be made in the absence of an
approved SIP with an adequate motor vehicle emissions budget. See
Environmental Def. Fund v. EPA, 167 F.3d 641, 650 (D.C. Cir. 1999)
(recognizing that section 7506 does not "dictate[ ] how conformity
should be determined" if "no approved SIP exists or [if] the approved
SIP contains no adequate motor vehicle emissions budget"). It there-
  9
    Maryland submitted its Attainment SIP for Baltimore in accordance
with this extended deadline, and it is this Attainment SIP that contains
the motor vehicle emissions budget at issue in this case. As of the time
of this writing, the EPA has yet to approve the Attainment SIP, although
it anticipates taking action by October 2001.
                1000 FRIENDS OF MARYLAND v. BROWNER                       23
fore cannot be said that the EPA’s reliance in this case upon a submit-
ted but not yet approved MVEB is inconsistent with the requirements
of section 7506(c).10

                                    (4)

   The Petitioner also contends that finding the revised MVEB to be
adequate without requiring additional modeling is inconsistent with
those portions of the Clean Air Act governing the EPA’s approval and
partial approval of SIP revisions. See 42 U.S.C.A. § 7410(l) ("The
Administrator shall not approve a revision of a plan if the revision
would interfere with any applicable requirement concerning attain-
ment and reasonable further progress . . ., or any other applicable
requirement of this chapter."); 42 U.S.C.A. § 7410(k)(3) (authorizing
the EPA to approve a portion of a plan revision if that portion "meets
all the applicable requirements of this chapter"). As we understand the
Petitioner’s argument, it suggests that the adequacy finding is the
functional equivalent of an approval (or perhaps a partial approval) of
a SIP revision, which requires compliance with all of the Act’s SIP
requirements, including the Part D photochemical grid modeling
requirement.

   Preliminarily, we note that sections 7410(k)(3) and 7410(l) refer to
approval of SIP revisions, and we question whether an adequacy find-
ing regarding a revised motor vehicle emissions budget amounts to
approval of a SIP revision. Nonetheless, even if the adequacy finding
should be treated as the functional equivalent of an approval, whether
such approval could be granted absent new photochemical grid mod-
eling is again dependent on the scope of section 7511a(c)(2)(A)’s
  10
    The Petitioner insists that it is not challenging the validity vel non of
the EPA’s regulations governing the use and adequacy of submitted
motor vehicle emissions budgets. Therefore, even if it would be proper
for us to consider the reasonableness of these regulations, see 42
U.S.C.A. § 7607(b)(1) (requiring challenges to nationally applicable reg-
ulations to be brought in the D.C. Circuit within 60 days after notice of
promulgation); but see Illinois Envtl. Prot. Agency, 947 F.2d at 289-92
(considering the validity of certain Clean Air Act regulations even
though the action was commenced several years after the regulations
were promulgated), we do not address the issue.
24             1000 FRIENDS OF MARYLAND v. BROWNER
modeling requirement. As discussed above, while section
7511a(c)(2)(A) requires an attainment demonstration to be supported
by modeling, the statute does not address whether new modeling must
be performed any time any portion of an attainment SIP is revised
while awaiting approval by the EPA. Thus, the EPA’s "approval" of
the revised MVEB without requiring new modeling is not inconsistent
with section 7410(k)(3) or section 7410(l).

                                 (5)

   In sum, we conclude that nothing in the Clean Air Act requires that
new photochemical grid modeling be performed when a motor vehicle
emissions budget in a submitted SIP is revised or before the revised
budget may be found adequate for conformity purposes. We therefore
cannot say that the EPA’s action was "not in accordance with law."
5 U.S.C.A. § 706(2)(A). The question, then, is whether the EPA’s
action can otherwise be considered arbitrary or capricious.

                                 B.

   The Petitioner appears to challenge as arbitrary and capricious the
EPA’s decision that new modeling was not necessary upon revision
of the MVEB, as well as the EPA’s determination that the revised
MVEB was adequate for conformity purposes. We address these
claims in turn.

                                 (1)

   We first consider whether the EPA acted arbitrarily or capriciously
when it concluded that new photochemical grid modeling was not
necessary upon the submission of the revised MVEB. To address this
argument we must explain the action taken by the EPA on Balti-
more’s submitted Attainment SIP.

   When reviewing the Attainment SIP, the EPA found the initial
MVEB inadequate, and the EPA proposed to approve the Attainment
SIP only if Maryland took certain actions. First, the EPA concluded
that "additional emission reductions beyond those provided by the SIP
submission are necessary for attainment." 64 Fed. Reg. at 70,403. Part
               1000 FRIENDS OF MARYLAND v. BROWNER                  25
of those emissions reductions would be realized through the imple-
mentation of the national "Tier 2/Sulphur" program, which was not
addressed in the SIP submission. The EPA therefore required Mary-
land to revise the Attainment SIP submission and MVEB to reflect
those reductions. See id. The EPA also stated that the revised MVEB
must reflect the effects of other control measures, such as the "low
emissions vehicle program," which were assumed in the modeling. Id.
at 70,409. Second, the EPA required Maryland to commit to revise its
MVEB within one year after the EPA’s release of "MOBILE6," a
model used for estimating mobile source emissions. See id. at 70,403,
70,410. Third, the EPA concluded that, even considering the Tier
2/Sulphur reductions, Baltimore would not achieve attainment with-
out the application of additional emission control measures. See id.
Thus, the EPA required Maryland to identify potential control mea-
sures and to submit an enforceable commitment to implement the
measures necessary to reduce emissions to a level consistent with
attainment. See id. at 70,404, 70,410. Fourth, the EPA required Mary-
land to submit "adopted control measures consistent with the [nitro-
gen oxides] reductions assumed in the attainment demonstration." Id.
at 70,409. Finally, the EPA required Maryland to commit to perform-
ing a "mid-course review," which is "a reassessment of modeling
analyses and more recent monitored data to determine if a prescribed
control strategy is resulting in emission reductions and air quality
improvements needed to attain the ambient air quality standard for
ozone as expeditiously as practicable but no later than the statutory
dates." Id. at 70,405.

   Notwithstanding these deficiencies in the submitted SIP, the EPA
did find that the computer modeling contained in the submitted SIP
was adequate, even though the modeling showed ozone concentration
levels in excess of attainment levels. The EPA has long recognized
that there are "uncertainties inherent in available models and in esti-
mating future emissions." EPA Guidance on Use of Modeled Results
to Demonstrate Attainment of the Ozone NAAQS, J.A. W7. The EPA
thus allows the use of supplemental analysis, including a "weight of
evidence" analysis, to demonstrate attainment in cases where the
modeling shows ozone levels exceeding the NAAQS. If the weight of
evidence approach "leads to compelling evidence that attainment is
likely," J.A. W7, then the EPA will conclude that attainment has been
demonstrated even if the modeled levels are too high. However, the
26                1000 FRIENDS OF MARYLAND v. BROWNER
EPA guidance notes that "the further [modeling] results are from
passing the test, the more difficult it is to develop compelling supple-
mentary evidence that attainment is likely." Id.

   As to the modeling for Baltimore, the EPA determined that the
modeling actually over-predicted ozone levels. See 64 Fed. Reg. at
70,407. After accounting for the over-prediction, the EPA concluded
that the modeling showed ozone levels that were "close enough to
attainment to warrant the consideration of weight-of-evidence argu-
ments that support the demonstration of attainment." Id. After apply-
ing the weight-of-evidence analysis, the EPA concluded that the
modeling demonstrated "that it is likely the Baltimore area will attain
the 1-hour ozone standard by the statutory date of 2005," id., so long
as Maryland committed to adopting additional control measures, as
previously discussed.

   Because the EPA considered the effects of the additional control
measures it was requiring when it analyzed the submitted modeling,
the EPA determined that new modeling was not needed:

       The EPA is not requesting that States11 perform new photo-
       chemical grid modeling to assess the full air quality impact
       of the additional measures that would be adopted. Rather, as
       described above, one of the factors that EPA can consider
       as part of the [weight of evidence] analysis of the attainment
       demonstration is whether there will be additional emission
       reductions anticipated that were not modeled. Therefore,
       EPA will consider the reductions from these additional mea-
       sures as part of the [weight of evidence] analysis if the State
       adopts the measures or, as appropriate, submits an enforce-
       able commitment to adopt the measures.

64 Fed. Reg. at 70,403-04.

  Except for the already rejected argument that the Clean Air Act
explicitly requires new modeling upon the revision of a SIP, the Peti-
  11
    Although the EPA in this document focused most specifically on
Baltimore’s submitted Attainment SIP, it also addressed the submissions
of other states.
                1000 FRIENDS OF MARYLAND v. BROWNER                    27
tioner offers no concrete argument as to why it was improper for the
EPA to conclude that new modeling was not necessary. While there
may be cases where previously performed modeling is inadequate to
demonstrate attainment such that the EPA’s failure to require new
modeling in those cases might be found to be arbitrary or capricious,
this is not such a case.

   As explained, the EPA factored into its analysis of the sufficiency
of the existing modeling the effects of the SIP revisions that it was
requiring. Because the modeling sufficiently demonstrated attainment
when those revisions were considered, the EPA rationally concluded
that new modeling was not necessary. See Chevron, 467 U.S. at 843
("The power of an administrative agency to administer a congressio-
nally created program necessarily requires the formulation of policy
and the making of rules to fill any gap left, implicitly or explicitly,
by Congress." (ellipsis and internal quotation marks omitted)). We
cannot say the EPA made a clear error of judgment when reaching
this conclusion. See Hughes River Watershed Conservancy v. John-
son, 165 F.3d 283, 287 (4th Cir. 1999) ("When reviewing an agency’s
decision to determine if that decision was arbitrary and capricious, . . .
we look only to see if there has been a clear error of judgment."
(internal quotation marks omitted)); Natural Res. Def. Council, Inc.
v. EPA, 16 F.3d 1395, 1401 (4th Cir. 1993) ("[T]his court’s task is to
scrutinize the EPA’s activity to determine whether the record reveals
that a rational basis exists for its decision." (internal quotation marks
omitted)).

                                   (2)

   The Petitioner also challenges the substantive adequacy finding,
contending that without new modeling, the EPA’s determination that
the revised MVEB was adequate for conformity purposes was pure
speculation, not grounded on any reliable information. We disagree.

  When the EPA found the revised MVEB adequate for conformity
purposes, it did so pursuant to the "adequacy criteria" contained in 40
C.F.R. § 93.118(e)(4)(i)-(vi). The adequacy criteria provide, in perti-
nent part, that:

     EPA will not find a motor vehicle emissions budget in a
     submitted control strategy implementation plan revision or
28               1000 FRIENDS OF MARYLAND v. BROWNER
       maintenance plan to be adequate for transportation confor-
       mity purposes unless the following minimum criteria are
       satisfied:

       ...

         (iii) The motor vehicle emissions budget(s) is clearly
       identified and precisely quantified;

          (iv) The motor vehicle emissions budget(s), when consid-
       ered together with all other emissions sources, is consistent
       with applicable requirements for reasonable further prog-
       ress, attainment, or maintenance (whichever is relevant to
       the given implementation plan submission);

         (v) The motor vehicle emissions budget(s) is consistent
       with and clearly related to the emissions inventory and the
       control measures in the submitted control strategy imple-
       mentation plan revision or maintenance plan . . . .

40 C.F.R. § 93.118(e)(4).12

   Even though the revised MVEB was higher than the one originally
found to be inadequate, the EPA determined that the revised budget,
when considered with the emissions reduction programs in place and
when considered with Maryland’s enforceable commitment to imple-
ment all other control measures necessary to reach attainment, was
consistent with attainment. The EPA considered whether the revised
MVEB was consistent with the targeted emissions levels for the mile-
stone years established by Baltimore’s "reasonable further progress"
demonstration. While the revised budget was consistent with the tar-
get levels for the year 2002, the EPA noted that it exceeded the 2005
target level for the emissions of volatile organic compounds
("VOCs"). However, because Baltimore’s SIP included control mea-
  12
    Certain portions of the EPA’s conformity regulations were found to
be inconsistent with the requirements of the Clean Air Act by the D.C.
Circuit and were remanded to the Agency. See Environmental Def. Fund,
167 F.3d at 651. No portion of the adequacy criteria quoted above were
affected by that decision.
               1000 FRIENDS OF MARYLAND v. BROWNER                  29
sures that would bring the levels of nitrogen oxides ("NOx") below
the target NOx level, Baltimore could use the surplus of NOx control
as a substitute for VOC control. Such substitution is permitted by the
Clean Air Act, see 42 U.S.C.A. § 7511a(c)(2)(C), and the EPA con-
cluded that with the substitution, the revised MVEB was consistent
with Baltimore’s 2005 "reasonable further progress" target. In addi-
tion, the EPA noted that when submitting the revised budget, Mary-
land reaffirmed its commitment to adopt all control measures
necessary to reach attainment, as required by the EPA, and Maryland
also committed to adopt any additional control measures necessary to
offset the increase in emissions caused by the use of the updated fleet
information. The EPA thus concluded that the revised budget satisfied
the requirements of the adequacy regulations, specifically finding that
the revised budget, when considered with all other emissions reduc-
tions, was consistent with attainment.

   The Petitioner again offers no concrete argument to show the fal-
lacy of this determination, except the conclusory assertion that new
modeling is the only way to effectively determine whether the revised
MVEB is consistent with attainment. As discussed above, the EPA
thoroughly analyzed the modeling performed in connection with the
submitted Attainment SIP, and the EPA carefully analyzed the effect
of the revised budget submitted by Maryland. After this careful analy-
sis, the EPA determined that the revised budget was consistent with
attainment, a determination that complied with the general require-
ments of the conformity provisions of the Clean Air Act and with the
requirements of the EPA’s adequacy regulations. See Natural Res.
Def. Council, 25 F.3d at 1073 ("An agency seldom acts arbitrarily
when it acts in conformity with its unchallenged rules."). In our view,
the conclusion that the revised budget was consistent with attainment
was not speculative but instead was based on a reasoned analysis of
the information before the EPA. Under these circumstances, we can-
not conclude that the EPA acted arbitrarily or capriciously when find-
ing the revised MVEB to be adequate for conformity purposes. See
Steel Mfrs. Ass’n v. EPA, 27 F.3d 642, 646 (D.C. Cir. 1994) (per
curiam) ("In assessing whether agency decisions are arbitrary and
capricious, we afford the agency significant leeway. We do not substi-
tute our judgment for that of the agency; we require only that the
agency’s decisions reflect reasoned decisionmaking based on evi-
dence in the record."); cf. Baltimore Gas & Elec. Co. v. Natural Res.
30             1000 FRIENDS OF MARYLAND v. BROWNER
Def. Council, Inc., 462 U.S. 87, 103 (1983) ("[A] reviewing court
must remember that the [agency] is making predictions, within its
area of special expertise, at the frontiers of science. When examining
this kind of scientific determination, as opposed to simple findings of
fact, a reviewing court must generally be at its most deferential.").

   The Petitioner, however, contends that the EPA erred by finding
the revised MVEB adequate since the revised budget was higher than
the previous budget found to be inadequate. The Petitioner claims that
any increases in motor vehicle emissions must be offset by reductions
in other mobile source emissions, so that the EPA’s reliance on Mary-
land’s commitment to adopt non-mobile source control measures was
improper. We find this argument to be without merit.

   The Petitioner’s argument is premised on 42 U.S.C.A. § 7511a(c)
(5)(A), which states:

     Beginning 6 years after November 15, 1990, and each third
     year thereafter, the State shall submit a demonstration as to
     whether current aggregate vehicle mileage, aggregate vehi-
     cle emissions, congestion levels, and other relevant parame-
     ters are consistent with those used for the area’s
     demonstration of attainment. Where such parameters and
     emissions levels exceed the levels projected for purposes of
     the area’s attainment demonstration, the State shall within
     18 months develop and submit a revision of the applicable
     implementation plan that includes a transportation control
     measures program consisting of measures from, but not lim-
     ited to, section 7408(f) of this title that will reduce emis-
     sions to levels that are consistent with emission levels
     projected in such demonstration. . . .

42 U.S.C.A. § 7511a(c)(5)(A) (West 1995) (emphasis added). Section
7511a(c)(5)(A) simply provides that once a state has established a
budget for motor vehicle emissions through an attainment demonstra-
tion, then the state must periodically monitor actual emissions. If the
actual emissions exceed the budgeted emissions, the state must offset
those exceedances with reductions from the transportation sector. In
this case, however, while the EPA has found the revised MVEB to be
adequate for conformity purposes, it has yet to formally approve Bal-
                1000 FRIENDS OF MARYLAND v. BROWNER                   31
timore’s attainment SIP. Once the Attainment SIP is approved, then
actual emissions can be measured against the attainment budget. If the
actual emissions exceed the budgeted level, only then does section
7511a(c)(5)(A) come into play and require the adoption of transporta-
tion control measures. Thus, the EPA’s failure to require transporta-
tion control measures does not serve as a basis to invalidate the
agency’s adequacy finding.

                                   C.

   After carefully considering the arguments raised by the Petitioner,
we cannot conclude that the EPA acted in a manner inconsistent with
the language of the Clean Air Act when it did not require the perfor-
mance of additional photochemical grid modeling upon submission of
the revised MVEB or when it allowed a submitted but not approved
budget to be used for conformity purposes. Likewise, we cannot con-
clude that the EPA otherwise acted arbitrarily or capriciously when
it decided that new modeling was not necessary or when it determined
that the revised budget was adequate for conformity purposes.

                                   V.

   The Petitioner’s final argument is that the EPA violated the APA
by not sufficiently explaining its basis and purpose when finding the
revised MVEB to be adequate. See 5 U.S.C.A. § 553(c) (requiring the
agency in certain proceedings to "incorporate in the rules adopted a
concise general statement of their basis and purpose"). The Petitioner
contends that this failure requires us to set aside the adequacy finding.
Although the EPA contends that the basis-and-purpose requirement
does not apply to the adequacy determination, which the EPA charac-
terizes as an "informal adjudication," we need not decide that ques-
tion. Assuming that the basis-and-purpose requirement applies to
adequacy determinations, we find that the EPA sufficiently explained
its actions.

  To satisfy the basis-and-purpose requirements of the APA, the
agency need not provide

    an exhaustive explanation of an administrator’s reasoning
    for adopting a rule. Required is a concise general statement
32              1000 FRIENDS OF MARYLAND v. BROWNER
     of the regulation’s basis and purpose. There is no obligation
     to make references in the agency explanation to all the spe-
     cific issues raised in comments. The agency’s explanation
     must simply enable a reviewing court to see what major
     issues of policy were ventilated by the informal proceedings
     and why the agency reacted to them the way it did.

South Carolina ex rel. Tindal v. Block, 717 F.2d 874, 886 (4th Cir.
1983) (citations, alterations, and internal quotation marks omitted).
While an "agency must examine the relevant data and articulate a sat-
isfactory explanation for its action[,] including a rational connection
between the facts found and the choice made," courts will "uphold a
decision of less than ideal clarity if the agency’s path may reasonably
be discerned." Motor Vehicle Mfrs. Ass’n v. State Farm Mut. Auto.
Ins. Co., 463 U.S. 29, 43 (1983) (internal quotation marks omitted).

   As discussed above, the EPA in the document finding Baltimore’s
initial MVEB to be inadequate explained why additional modeling
was not necessary. And in its "Technical Support Document," the
EPA explained why it believed the revised MVEB was adequate for
conformity purposes. Although the explanations may not have been
as detailed as the Petitioner would have liked, we nonetheless con-
clude that through these documents the EPA adequately addressed the
somewhat general comments of the Petitioner and sufficiently
explained the basis and purpose of its actions. See Reytblatt v. United
States Nuclear Regulatory Comm’n, 105 F.3d 715, 722-23 (D.C. Cir.
1997) ("Although the NRC did not directly respond to Dr. Reytblatt’s
suggested alternatives . . ., its explanation was adequate in light of the
general nature of Dr. Reytblatt’s comments . . . ."); National Recy-
cling Coalition, Inc. v. Browner, 984 F.2d 1243, 1252 (D.C. Cir.
1993) (holding that the EPA’s explanation in five different documents
of its interpretation of a specific statutory provision satisfied the
APA’s basis-and-purpose requirement).

                                   VI.

   To summarize, we conclude that nothing in the Clean Air Act
expressly requires the submission of new photochemical grid model-
ing upon the revision of a motor vehicle emissions budget contained
in a submitted attainment SIP. We also conclude that the EPA did not
               1000 FRIENDS OF MARYLAND v. BROWNER                 33
act arbitrarily or capriciously when it declined to require new model-
ing in conjunction with the revision of Baltimore’s motor vehicle
emissions budget or when it found the budget to be adequate for con-
formity purposes. And because the EPA sufficiently explained the
basis and purpose of its actions, we decline to set aside the adequacy
determination. Accordingly, the petition for review is hereby denied.

                                                 PETITION DENIED
