                           In the
 United States Court of Appeals
               For the Seventh Circuit
                        ____________

Nos. 03-2839 & 03-3329
SIERRA CLUB,
                                                     Petitioner,
                               v.

ENVIRONMENTAL PROTECTION AGENCY,
                                                    Respondent.

Intervening Respondents:
       State of Illinois; State of Missouri

                        ____________
                Petitions to Review Orders of the
                Environmental Protection Agency
                        ____________
       ARGUED JUNE 1, 2004—DECIDED JULY 6, 2004
                    ____________



 Before EASTERBROOK, KANNE, and ROVNER, Circuit
Judges.
  EASTERBROOK, Circuit Judge. Changes to the environ-
mental laws in 1990 reduced the allowable levels of ozone
pollution and set deadlines for attainment. Clean Air Act
Title I, Part D, subpart 2, 42 U.S.C. §§ 7511 to 7511f. The
St. Louis metropolitan area, initially classified as a “moder-
ate” nonattainment zone, had until November 15, 1996, to
comply. 42 U.S.C. §7511(a)(1). A moderate jurisdiction that
missed this deadline was to be reclassified automatically as
2                                  Nos. 03-2839 & 03-3329

a “serious” nonattainment area, 42 U.S.C. §7511(b)(2)(A).
That change requires additional costly anti-pollution steps.
One of the principal differences between the 1990 legisla-
tion and its predecessor was this mandatory reclassifica-
tion; the legislation leaves the EPA less discretion with
respect to ozone than other pollutants. See Whitman v.
American Trucking Associations, Inc., 531 U.S. 457, 481-86
(2001). Nonetheless, when St. Louis failed to meet the
deadline, the EPA decided that it had done well enough
that its status should remain unchanged. In Sierra Club v.
EPA, 311 F.3d 853 (7th Cir. 2002), we held that dispensa-
tion unlawful and directed the EPA to apply the statute as
written. See also Sierra Club v. EPA, 294 F.3d 155 (D.C.
Cir. 2002). Delay in compliance required a turn of the screw
even though St. Louis was making progress.
  While the proceedings that led to our 2002 decision were
under way, St. Louis finally met the ozone standards. It
asked the EPA for a formal decision that it satisfies the
requirements for ozone. Before designating any area as in
compliance, the EPA must make five determinations:
    The Administrator may not promulgate a redes-
    ignation of a nonattainment area (or portion there-
    of) to attainment unless—
        (i) the Administrator determines that the
        area has attained the national ambient air
        quality standard;
        (ii) the Administrator has fully approved
        the applicable implementation plan for the
        area under section 7410(k) of this title;
        (iii) the Administrator determines that
        the improvement in air quality is due to
        permanent and enforceable reductions in
        emissions resulting from implementation of
        the applicable implementation plan and
        applicable Federal air pollutant control
Nos. 03-2839 & 03-3329                                     3

        regulations and other permanent and en-
        forceable reductions;
        (iv) the Administrator has fully approved a
        maintenance plan for the area as meeting
        the requirements of section 7505a of this
        title; and
        (v) the State containing such area has met
        all requirements applicable to the area un-
        der section 7410 of this title and part D of
        this subchapter.
42 U.S.C. §7407(d)(3)(E). The EPA made all of these find-
ings in 2003 for the St. Louis metropolitan area (which
spans the border between Missouri and Illinois, and hence
requires consideration of multiple state plans). See 68 Fed.
Reg. 25418 (May 12, 2003) (Missouri), 68 Fed. Reg. 25442
(May 12, 2003) (Illinois). The Sierra Club asks us to set
aside these decisions. It does not contest the agency’s find-
ing that the St. Louis area now meets the national ambient
air quality standard for ozone. Nor does it challenge the
vital third finding: that “the improvement in air quality
is due to permanent and enforceable reductions in emis-
sions”. But it insists that St. Louis lacks a proper “appli-
cable implementation plan for the area under section
7410(k)” (requirement (ii)) and that the area’s maintenance
plan (requirement (iv)) does not meet all requirements of
§7505a. We start with the challenge to the maintenance
plan.
  A maintenance plan must take into account the sort
of things, such as population growth and changes to the
industrial base, that might cause existing pollution-control
measures to become inadequate in the future even if they
served well in the past. Ozone at or near ground level comes
principally from chemical reactions involving its precursors,
nitrous oxides (NOx) and volatile organic compounds. Both
implementation plans and maintenance plans thus must
4                                     Nos. 03-2839 & 03-3329

provide for controls on the emission of these precursors. But
what emissions are likely in the future, and what steps
could reduce them by the required amount? Accurate
projections depend on supplying good data to good models.
All concrete requirements of §7505a, to which requirement
(iv) refers, have been satisfied. But a maintenance plan
serves as an amendment to the local implementation plan,
and 42 U.S.C. §7511a(c)(2)(A) and (j)(1) thus may affect it.
These subsections require both multi-state areas and
serious nonattainment areas to “use photochemical grid
modeling or any other analytical method determined [by the
EPA], in [its] discretion, to be at least as effective.” Missouri
and Illinois have not promised to use photochemical grid
modeling as part of their maintenance endeavors. The
Sierra Club insists that all multi-state areas must use
photochemical grid modeling as long as their maintenance
plans are in effect. The EPA thinks that other tools can
suffice—and the Sierra Club does not dispute this at the
factual level. It contends, rather, that photochemical grid
modeling is essential no matter how thorough and rigorous
the maintenance plan may be. Unless the EPA makes a
formal determination that some other modeling system is
“at least as effective”—and the EPA did not make such a
finding, even though it appears to believe that the St. Louis
region’s methods are at least as effective—then the method
named in the statute is indispensable.
   Thus we have a straightforward issue: must every mul-
ti-state area use photochemical grid modeling continually
(at least until a formal equivalence finding has been made)?
The EPA’s view does not contradict the statute: §7511a does
not refer to maintenance plans at all, and it is only through
the back door (because the maintenance plan amends the
implementation plan) that this section enters the picture.
What is more, §7511a deals with pre- attainment require-
ments. This is the foundation of the agency’s view that an
area need not use photochemical grid modeling as part of a
Nos. 03-2839 & 03-3329                                         5

maintenance plan. That is not an inevitable reading of the
statute, but the EPA receives the benefit of deference under
Chevron U.S.A. Inc. v. Natural Resources Defense Council,
Inc., 467 U.S. 837 (1984), which American Trucking held
applicable to the ozone subchapter. See 531 U.S at 481.
Congress required nonattainment areas to shoulder more
substantial burdens. St. Louis, like any other place that
wants to keep a valuable attainment designation, has every
incentive to choose adequate modeling tools. If it does not,
and as a result slips out of compliance as its population or
industry changes, then it must pay a steep price for back-
sliding. It is sensible for the federal agency to give localities
that must pay the piper some opportunity to call the tune.
Methods of projecting developments differ in accuracy and
cost; allowing the affected region to make a cost-benefit
comparison has much to recommend it. Recall that the
Sierra Club does not contend that Missouri and Illinois
have chosen irresponsibly, but only that the statute grants
them (and the EPA) no option. The EPA’s approach has
received the approbation of the Sixth Circuit. See Wall v.
EPA, 265 F.3d 426, 436 (6th Cir. 2001). We see no reason to
create a conflict.
  Nor are we persuaded by the Sierra Club’s argument that
the maintenance plans fail to describe all contingency
measures that may be applied if problems arise. The statute
does not call for any particular degree of precision in the
period after attainment (contrast §7502(c)(9), which de-
mands “specific measures” in the pre-attainment period), so
again the EPA (and the affected states) had choices to
make, choices that may be gainsaid only if obviously
misguided. Intelligent decisions may depend on the nature
of future developments. Missouri and Illinois have commit-
ted themselves to action; that they have reserved some
discretion about the means does not spoil their plans. See
Greenbaum v. EPA, 2004 U.S. App. Lexis 10785 *24-38 (6th
Cir. June 3, 2004). Cf. BCCA Appeal Group v. EPA, 355
F.3d 817 (5th Cir. 2003).
6                                   Nos. 03-2839 & 03-3329

  Let us turn, then, to requirement (ii): that “the Adminis-
trator has fully approved the applicable implementation
plan for the area under section 7410(k) of this title”. This
mentions §7410(k), but the cross-reference is unillum-
inating. It does not answer one vital question: what kind of
implementation plan is “applicable”? Although the parties
have disputed many technical issues, most of their disagree-
ment boils down to a single question: Is an “applicable” plan
the same as the area’s pre-attainment plan (as Sierra Club
contends), or is it limited to those measures that have
proved to be necessary to achieve compliance (the EPA’s
view)? The Sierra Club contends that every attainment plan
for an area at the serious level must specify the implemen-
tation of all reasonably available control measures (though
the D.C. Circuit disagrees, see Sierra Club, 294 F.3d at 162-
63), and must ensure a 15% reduction in the emission of
volatile organic compounds (though the Tenth Circuit
disagrees, see Sierra Club v. EPA, 99 F.3d 1551, 1555-56
(10th Cir. 1996)), but these are sidelights. The real dispute
is whether St. Louis, having been promoted to the serious
category by delay in meeting the national ozone standard,
must use control measures appropriate to a serious
nonattainment area as a condition of being designated as
an attainment area.
  In a nutshell, the EPA’s view is that the “applicable” plan
requires an area to continue doing whatever worked, and
nothing more. In other words, the EPA wants the plan to
contain all provisions that required some set of controls to
be in place before the date the area met the national
standard. Here’s a concrete example, and a principal bone
of contention between the parties. Moderate nonattainment
areas must ensure that every source of more than 100 tons
(annually) of precursor chemicals takes prescribed steps to
curtail their emission. For serious nonattainment areas, the
threshold falls to 50 tons. 42 U.S.C. §7511a(c). Our 2002
decision concluded that St. Louis must be treated as a
Nos. 03-2839 & 03-3329                                     7

serious nonattainment area—although it was classified as
a moderate area in 2000, when it filed the application to be
reclassified as an attainment area. Even the plan applicable
to a serious nonattainment area would allow newly covered
sources some lead time to limit their emissions. 42 U.S.C.
§7511(a)(1), (a)(5). Before that time arrived, St. Louis met
the national ozone standard. Sierra Club believes that
businesses in the 50 to 100-ton range still must implement
controls; the EPA believes that an “applicable” implementa-
tion plan need not require this. The Sierra Club’s definition
of “applicable,” by contrast, is “whatever should have been
in the plan at the time of attainment” rather than “what-
ever actually was in the plan and already implemented or
due at the time of attainment.”
  Because the statute does not define “applicable,” there is
no ineluctable basis for a choice between these options. See
Wall, supra, 265 F.3d at 438-40. Both are conceivable un-
derstandings of the law. Chevron therefore affords the EPA
leeway. (The St. Louis designation is the result of notice-
and-comment rulemaking under explicit statutory delega-
tion; this is the core of Chevron’s domain. See United States
v. Mead Corp., 533 U.S. 218 (2001).) The EPA’s view is at
least as sensible as the Sierra Club’s, likely more
so. Requirement (ii) reads: “the Administrator has fully
approved the applicable implementation plan for the area
under section 7410(k)”. That’s a curiously indirect way of
requiring a plan to continue without change, or become
more onerous. Why didn’t the statute say: “the
Administrator has determined that the area will continue
to abide by the implementation plan that was, or should
have been, in place”? A word such as “applicable” implies
that there may be differences between the contents of the
pre-attainment plan and those required for the post-at-
tainment period. Against this the Sierra Club points to the
way “applicable” is used in other parts of the Clean Air Act
(e.g., §7511a(i)), but that statute is too complex a compro-
8                                   Nos. 03-2839 & 03-3329

mise, and has been amended too many times, to indulge the
assumption that all of its words must be used consistently
in all of its subsections. “Applicable” is a protean word that
takes color from context; it lacks a single, enduring mean-
ing.
  Under the Sierra Club’s view, compliance does not have
a payoff: the residents and businesses of St. Louis must
take the same costly steps that would be required had the
area been less successful. As the reason to take additional
steps was to achieve an adequate reduction in ozone, it
would be odd to require them even when they turned out to
be unnecessary. Some parts of the Clean Air Act forbid
cost-benefit analysis, see Union Electric Co. v. EPA, 427
U.S. 246 (1976)—and subpart (2) on ozone is one of these,
to the extent it mandates the progression to more severe
controls until compliance has been achieved—but when the
statute is ambiguous the EPA is free to take costs into
account. That’s the upshot of Chevron. See also Cass R.
Sunstein, Risk and Reason: Safety, Law, and the
Environment (2002); Stephen Breyer, Breaking the Vicious
Circle: Toward Effective Risk Regulation (1993). The
agency’s approach strikes us as sensible.
   Much of the Sierra Club’s argument assumes that reclas-
sification of St. Louis to serious nonattainment was some
sort of punishment that its residents should not be allowed
to escape. Not at all. “The St. Louis region” is an abstrac-
tion, a convenient collective phrase for millions of people
whose own lives and fortunes are at issue. Reclassification
was a combination of (a) goad (clean up or suffer expensive
measures), and (b) palliative (sterner measures expedite
compliance). Once an area has meet the national air quality
standard, neither rationale calls for extra stringency;
indeed, the statutory system would not be much of a goad
if the tighter controls must continue even after attainment.
It is not as if neighborhood bakeries and other smallish
point sources were themselves blameworthy and in need of
20 lashes for transgressions.
Nos. 03-2839 & 03-3329                                     9

  One final subject requires brief comment. While the EPA
was considering St. Louis’s request for designation as an
attainment area for ozone, the D.C. Circuit vacated some
elements of the EPA’s national regulations for the control
of nitrous oxides (known as the NOx SIP Call). See
Michigan v. EPA, 213 F.3d 663, 685, 695 (D.C. Cir. 2000).
After redesignating St. Louis, the EPA revised the NOx SIP
Call. See 69 Fed. Reg. 21604 (Apr. 21, 2004). If the regula-
tion adopted in 2004 implies a revision of the implementa-
tion and maintenance plans for the St. Louis region, the
EPA will need to take action. But the Sierra Club’s petitions
for review do not raise any question about the implementa-
tion of the NOx SIP Call in St. Louis.
  The petitions for review are denied.

A true Copy:
      Teste:

                        ________________________________
                        Clerk of the United States Court of
                          Appeals for the Seventh Circuit




                    USCA-02-C-0072—7-6-04
