Clean Air Implementation Project v. Environmental Protection Agency

United States Court of Appeals

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued April 21, 1998 Decided August 14, 1998

No. 97-1117

Clean Air Implementation Project, et al.,

Petitioners

v.

Environmental Protection Agency,

Respondent

Natural Resources Defense Council, Inc. and

Battery Council International,

Intervenors

Consolidated with Nos.

97-1125, 97-1130, 97-1142, 97-1169, 97-1173, 97-1179,

97-1190, 97-1195, 97-1226, 97-1241, 97-1242, 97-1253,

97-1254, 97-1259, 97-1261, 97-1266, 97-1269, 97-1273,

97-1278, 97-1281, 97-1282, 97-1283, 97-1286, 97-1289

On Petition for Review of an Order of the

Environmental Protection Agency

---------
 Henry V. Nickel and William H. Lewis, Jr., argued the
cause for petitioners. With them on the briefs were Mel S.
Schulze, Lauren E. Freeman, David E. Menotti, William F.
Pedersen, Joshua D. Sarnoff, Gene E. Godley, Robert N.
Steinwurtzel, Howard B. Myers, Roger Walker, Leslie Sue
Ritts, Chris S. Leason, Robert Brager, David Friedland,
Christina Franz, Alexandra Dapolito Dunn, Julie Hatcher,
Michael H. Levin, Michael McGovern, Lynn L. Bergeson,
Bethami Auerbach, Robert L. Brubaker, Janet J. Henry,
Paul G. Wallach, Kenneth R. Meade, Jerome H. Heckman,
Peter L. de la Cruz, William M. Bumpers, Debra J. Jezouit,
Jennifer S. Leete, John L. Wittenborn, Chet M. Thompson,
Edwin H. Seeger and Jane C. Luxton. David F. Zoll and
Richard A. Flye entered appearances.

Karen L. Egbert and Patricia Ross McCubbin, Attorneys,
U.S. Department of Justice, argued the cause for respondent.
With them on the brief were Lois J. Schiffer, Assistant
Attorney General, Robert G. Dreher and Gregory B. Foote,
Counsel, U.S. Environmental Protection Agency. Cecilia E.
Kim, Attorney, U.S. Department of Justice, entered an ap-
pearance.

William H. Lewis, Jr., Joshua D. Sarnoff and David B.
Weinberg were on the brief for intervenor Battery Council
International.

Gail Lewkowicz was on the brief for amici curiae State
and Territorial Air Pollution Program Administrators (STAP-
PA) and Association of Local Air Pollution Control Officials
(ALAPCO).

Before: Silberman, Williams, and Randolph, Circuit
Judges.

Opinion for the Court filed by Circuit Judge Randolph.

Randolph, Circuit Judge: Petitioners Clean Air Implemen-
tation Project and other trade associations 1 brought this

__________
1 The trade associations represent various industry groups,
including car manufacturers, lumber companies, steel producers,
petroleum companies, and mining companies.

action for judicial review of the Environmental Protection
Agency's rule permitting the use of "credible evidence" to
prove or disprove violations of the Clean Air Act, 42 U.S.C.
ss 7401 et seq. They allege that the rule is illegal for various
reasons, including lack of statutory authority and unlawful
revision of substantive standards. We hold that the issues
they raise are unripe and cannot be decided at this time.

I

The Clean Air Act directs the EPA Administrator to devel-
op and promulgate three types of air pollution standards.
National ambient air quality standards ("NAAQS"), issued
under s 109, 42 U.S.C. s 7409, specify the maximum permis-
sible concentrations of six criteria pollutants in the air. See
40 C.F.R. pt. 50. The Act makes states primarily responsible
for the attainment and maintenance of the NAAQS through
state-designed implementation plans, see 42 U.S.C. s 7410,
also called "SIPs," which EPA must approve and which
become federally enforceable once approved, see id.
s 7413(a). Performance standards issued pursuant to s 111,
42 U.S.C. s 7411, regulate emissions of air pollutants from
newly constructed or modified stationary sources. See 40
C.F.R. pt. 60. Emission standards for stationary sources of
hazardous air pollutants for which no ambient air quality
standard is applicable are issued pursuant to s 112, 42 U.S.C.
s 7412.2 See 40 C.F.R. pt. 61. EPA may enforce these
standards through administrative, civil, or, with the assistance
of the Attorney General, criminal actions. See 42 U.S.C.
s 7413.

Before EPA adopted its credible evidence rule in February
1997, 62 Fed. Reg. 8314, the agency's air pollution standards
specified not only the maximum permissible level of emis-
sions, but also the performance or reference test that should
be used as a means of sampling and analyzing air pollutants

__________
2 In the Clean Air Act Amendments of 1990, Congress rewrote
s 112 to include a list of 189 toxic air pollutants that EPA was
required to regulate. However, s 112(q) provides that standards in
effect before the date of enactment "shall remain in force and effect
after such date."

for the particular standard. See, e.g., 40 C.F.R. ss 60.2,
61.02. A reference test is any "generic multi-use test proto-
col[ ] that measure[s] whether a source's emissions comply
with numeric performance standards." Paul D. Hoburg, Use
of "Credible Evidence" to Prove Clean Air Act Violations, 25
B.C. Envtl. Aff. L. Rev. 771, 784-85 (1998). Subparts of
Title 40 prescribe reference tests for various emission
sources. Appendix A to 40 C.F.R. Part 60, for instance,
contains more than fifty different test methods for determin-
ing compliance with the new source performance standards.
See also 40 C.F.R. pt. 61, App. B (listing test methods for
hazardous air pollutant standards); 40 C.F.R. pt. 51, App. M
(listing recommended test methods for state implementation
plans). In all, there are approximately 130 reference tests,
although the same test may be "used in connection with many
different performance standards." Hoburg, supra, at 785.

In the rulemaking challenged here, EPA added nearly
identical language to five sections of its regulations, providing
that nothing in them "shall preclude the use, including the
exclusive use, of any credible evidence information, relevant
to whether a source would have been in compliance with
applicable requirements if the appropriate performance or
compliance test or procedure had been performed." 40
C.F.R. s 60.11(g); see also 40 C.F.R. ss 51.212(c), 52.12(c),
52.33(a), and 61.12(e). The agency based these revisions on
its "long-standing authority under the Act, and on amplified
authority provided by the 1990 [Clean Air Act Amendments],"
specifically s 113(a) and (e), 42 U.S.C. s 7413(a), (e). 62 Fed.
Reg. 8314. Section 113 deals with federal enforcement of
emission standards and, according to its legislative history,
was amended to enhance EPA's enforcement powers. See
S. Rep. No. 101-228, at 358 (1989), reprinted in 1990
U.S.C.C.A.N. 3385, 3741. EPA maintains that the "language,
history and intent" of the 1990 Amendments support its
credible evidence revisions. 62 Fed. Reg. 8314.

Nothing in the rule itself defines or limits the possible
kinds of evidence encompassed within the phrase "credible
evidence." EPA explained in the preamble to its final rule:

"today's rule will make it clear that various kinds of informa-
tion other than reference test data, much of which is already
available and utilized for other purposes, may be used to
determine compliance or noncompliance with emission stan-
dards." 62 Fed. Reg. at 8315. The preamble listed "engi-
neering calculations, indirect estimates of emissions, and di-
rect measurement of emissions by a variety of means" as
methods on which EPA, state agencies, and industry routine-
ly rely. Id. Also mentioned were "continuous emission
monitoring" and "parametric monitoring" data. Id. To illus-
trate, EPA discussed the use of a continuous opacity monitor
instead of Method 9, the reference test method for opacity.
Method 9 requires that a "trained visible emissions observer
(VEO) view a smoke plume with the sun at a certain angle to
the plume in order to properly illuminate it. In contrast, a
continuous opacity monitor (COM) contains a calibrated light
source that provides for accurate and precise measurement of
opacity at all times. Notably, EPA uses COM data to certify
and re-certify the credentials of VEOs under Method 9." Id.
at 8319. Thus, according to the agency, continuous opacity
monitoring data would be credible evidence in lieu of Method
9. The preamble also cited two citizen suits based on credible
evidence. Id. at 8318. In Sierra Club v. Public Service Co.,
894 F. Supp. 1455 (D.Colo. 1995), the court accepted opacity
monitoring data and reports as means of proving emissions
violations. In Unitek Environmental Servs. v. Hawaiian
Cement, No. 95-00723 (D.Haw.1996), the court upheld the use
of evidence that included EPA's notice of violation issued to
Hawaiian Cement several months before, Hawaiian Cement's
admission of noncompliance, and results of Hawaiian Ce-
ment's computerized modeling of its own particulate emis-
sions.

Petitioners argue that EPA promulgated the rule without
statutory authority, that the revisions are unlawful because
EPA failed to comply with proper rulemaking procedures,
and that EPA violated the Clean Air Act by forcing states to
rewrite their implementation plans. The heart of the argu-
ment is that the credible evidence rule, by altering the means
of determining compliance for the new source performance

standards and the hazardous air pollutant standards, increas-
es the stringency of the underlying standards. Since EPA
admittedly did not conduct a rulemaking for each of the
standards to which the credible evidence rule may be applied,
petitioners charge that it violated the procedures required by
the Act. See 42 U.S.C. s 7607(d). EPA's short answer is
that there was no need for such proceedings because the
standards have not been changed.

II

Petitioners' theory of the relationship between tests and
standards is this: the test method is an integral part of the
standard itself and the test method should not be changed
without a full evaluation of the impact such a change might
have on the standard. The theory proceeds from the fact
that in developing its standards, EPA relied on tests showing
the standards to be consistently achievable using the best
current technology. See Brief of Petitioners at 9-10. EPA
then used these same test methods to determine compliance
with the numerical standards it promulgated. Citing Port-
land Cement Ass'n v. Ruckelshaus, 486 F.2d 375 (D.C. Cir.
1973), petitioners argue that changing the means of testing
compliance amounts to changing the standard themselves. In
Portland Cement, the court stated that "a significant differ-
ence between techniques used by the agency in arriving at
standards, and requirements presently prescribed for deter-
mining compliance with standards, raises questions about the
validity of the standard." Id. at 396. There the court
required EPA to explain the discrepancy between the method
used to develop the standard and the method used to enforce
it. Id. at 397.

Petitioners' view of the interaction between tests and stan-
dards leads them to two contentions. First, they assert that
any change in compliance method or test is substantive
because "use of a different test method or procedure can lead
to fundamental differences in results, due to differences in
analytical method, data reduction, or measurement location."
Brief of Petitioners at 13-14. For example, a newer and

more sensitive test might detect emissions in excess of the
numerical limit at times when the original reference test
would show that emissions were below the regulatory ceiling.
Second, they claim that the credible evidence rule converts
"periodic" standards to "continuous" ones. See id. at 35-42.
That is, sources previously subject to standards based on
"snapshot" data from infrequent "short-term" tests may now
have their compliance monitored on an ongoing basis through
the use of credible evidence. Id. at 35-36. Converting a
periodic standard into a continuous one makes the standard
more rigorous because, petitioners assert, continuous moni-
toring will capture all the fluctuations and variability inherent
in emissions and thus increase each source's number of
"violations." (According to petitioners, variability in emis-
sions had previously been compensated for by means of
infrequent testing.) The issues raised by these contentions
are not, we hold, justiciable at this time.

In 1967, three Supreme Court cases, decided in tandem,
revolutionized judicial review of agency rulemaking. The
cases--Abbott Laboratories v. Gardner, 387 U.S. 136; Toilet
Goods Ass'n v. Gardner, 387 U.S. 158; and Gardner v. Toilet
Goods Ass'n, 387 U.S. 167--dealt with the then-unsettled
question when, if ever, courts may pass upon the validity of
an agency regulation prior to its enforcement. "Before Ab-
bott Laboratories the courts typically reviewed the lawfulness
of an agency's rule, not when it was promulgated, but when it
was enforced. After Abbott Laboratories reviewing practice
changed radically." Stephen G. Breyer & Richard B. Stew-
art, Administrative Law and Regulatory Policy 1136 (2d ed.
1985). In deciding whether judicial review must await appli-
cation of the rule in the concrete setting of an enforcement
action, the Supreme Court adopted Judge Friendly's formula-
tion in Toilet Goods Ass'n v. Gardner, 360 F.2d 677, 684 (2d
Cir. 1966) (quoting Joint Anti-Fascist Refugee Comm. v.
McGrath, 341 U.S. 123, 156 (1951) (Frankfurter, J., concur-
ring): there must be an evaluation of "both the fitness of the
issues for judicial decision and the hardship to the parties of
withholding court consideration." Abbott Labs., 387 U.S. at
149.

In the three decades since Abbott Laboratories, "preen-
forcement review of agency rules and regulations has become
the norm, not the exception," Breyer & Stewart, supra, at
1137, a trend accelerated by Congress' enactment of a host of
regulatory statutes specifically providing for this. The review
provision of the Clean Air Act, 42 U.S.C. s 7607(b), invoked
here, is typical. It provides that a petition for judicial review
must be filed within 60 days of publication of a rule in the
Federal Register, 42 U.S.C. s 7607(b)(1), and that action of
the EPA Administrator "with respect to which review could
have been obtained ... shall not be subject to judicial review
in civil or criminal proceedings for enforcement," 42 U.S.C.
s 7607(b)(2). We have not considered this provision, or like
provisions in other regulatory statutes, as requiring the court
to adjudicate issues raised in a preenforcement challenge to a
rule unless those issues are suitable for decision. If the
issues are not of that nature, we will dismiss the petition as
unripe. See Louisiana Environmental Action Network v.
Browner, 87 F.3d 1379, 1385 (D.C. Cir. 1996); Association of
American Railroads v. Surface Transportation Bd., No.
97-1020, 1998 WL 343436, *4 (D.C. Cir. June 30, 1998).3 A
necessary corollary is that if the issues later become justicia-
ble, as a result for instance of an enforcement action, the
petitioner may then raise those issues, notwithstanding the
portion of s 7607(b)(2) just quoted. See Louisiana Environ-
mental Action Network, 87 F.3d at 1381; Baltimore Gas &
Elec. Co. v. ICC, 672 F.2d 146 (D.C. Cir. 1982).

As to petitioners' first contention, neither element of the
Abbott Laboratories inquiry--fitness for judicial decision and
hardship of denying relief--has been satisfied. In determin-
ing the fitness of an issue for judicial review we look to see
whether the issue "is purely legal, whether consideration of

__________
3 The purpose of withholding judicial review "is to prevent the
courts, through avoidance of premature adjudication, from entan-
gling themselves in abstract disagreements over administrative
policies, and also to protect the agencies from judicial interference
until an administrative decision has been formalized and its effects
felt in a concrete way by the challenging parties." Abbott Labs.,
387 U.S. at 148-49.

the issue would benefit from a more concrete setting, and
whether the agency's action is sufficiently final." Natural
Resources Defense Council, Inc. v. EPA, 22 F.3d 1125, 1133
(D.C. Cir. 1994) (quoting Her Majesty the Queen ex rel.
Ontario v. EPA, 912 F.2d 1525, 1532 (D.C. Cir. 1990)).
EPA's credible evidence rule is final, but in contending that
the rule alters the standards, petitioners have raised issues
that are not purely legal, issues that are not suitable for
decision in the abstract. See Truckers United for Safety v.
Federal Highway Administration, 139 F.3d 934 (D.C. Cir.
1998). Judicial resolution of these issues would benefit signif-
icantly from having "the scope of the controversy ... reduced
to more manageable proportions, and its factual components
fleshed out, by some concrete action applying the regulation
to the [petitioners'] situation in a fashion that harms or
threatens to harm" them. Lujan v. National Wildlife Fed'n,
497 U.S. 871, 891 (1990).

As matters now stand, there are too many imponderables.
EPA insists that using credible evidence will not "change any
of the numeric emission limits with which sources must
comply" and that reference tests remain the benchmark
against which credible evidence is measured. Brief of Re-
spondent at 3, 11. In promulgating the rule, EPA stated that
credible evidence was "not intended to and will not serve to
affect the stringency of underlying emission standards by
amending the nature of the compliance obligation." 62 Fed.
Reg. at 8315. It explained:

Typically, reference test methods ... quantify the pres-
ence of particular physical attributes--for example, mass
or concentration of a chemical or group of chemicals--
over a specified period of time. As long as these two
elements, quantification and specified time period--are
retained and the data from the alternate method is
related to the reference test, information generated by
alternate methods yield data bearing on what the results
of a reference test would have been, and the use of such
information to establish compliance or noncompliance in

an enforcement action will not affect the stringency of
the standard.

62 Fed. Reg. at 8319. Petitioners dismiss EPA's assertions,
claiming that the agency "is in denial" about the conse-
quences of its own actions. Brief of Petitioners at 34.

Will each of the 130 or so reference tests truly be main-
tained as benchmarks against which credible evidence will be
measured? The tests themselves are described in "painstak-
ing technical detail in various appendices throughout Title 40
C.F.R. chapter I." Hoburg, supra, at 785. For all we know,
application of EPA's credible evidence rule in the place of a
reference test may potentially affect some standards but not
others. Moreover, credible evidence is not a closed set.
Given the universe of all possible evidence that might be
considered "credible," it is impossible for us to decide now
what impact the rule will have. EPA's representation that
credible evidence must be "related" to the results a reference
test would have shown is highly abstruse. See 62 Fed. Reg.
8314 (promulgation of credible evidence rule). An enforce-
ment action brought on the basis of credible evidence would,
we believe, provide the factual development necessary to
determine whether the new rule has affected whatever exist-
ing standard is involved. Until then, we have the "classic
institutional reason to postpone review: we need to wait for a
rule to be applied to see what its effect will be." Louisiana
Environmental Action Network, 87 F.3d at 1385 (quoting
Diamond Shamrock v. Costle, 580 F.2d 670, 674 (D.C. Cir.
1978)).

Petitioners cannot point to any great hardship they would
suffer by our deferring judicial review. EPA's rule does not
require them "to engage in, or to refrain from, any conduct."
Texas v. United States, 118 S. Ct. 1257, 1260 (1998). Unlike
the drug manufacturers in Abbott Laboratories, but like the
cosmetics companies in Toilet Goods Ass'n v. Gardner, 387
U.S. at 164, petitioners here need not change their behavior
or risk costly sanctions. Source owners and operators are
already under an obligation to comply with EPA's emission
standards. If the credible evidence rule has in fact altered
these standards, petitioners can raise that as a defense in an

enforcement action. The burden of participating in future
proceedings does not "constitute sufficient hardship for the
purposes of ripeness." Florida Power & Light Co. v. EPA,
No. 95-1093, 1998 WL 336520, *8 (D.C. Cir. June 26, 1998).
To be sure, it is easier and cheaper to mount a single
challenge now rather than defend a series of enforcement
actions. But "this kind of litigation cost-saving" does not
"justify review in a case that would otherwise be unripe."
Ohio Forestry Ass'n v. Sierra Club, 118 S. Ct. 1665, 1671
(1998).

This brings us to petitioners' contention that the credible
evidence rule illegally converts "periodic" standards to "con-
tinuous" ones. Owners and operators of emission sources are
required, according to petitioners, to meet emission limits
only when intermittent tests are conducted; at all other times
they are subject to no more than a "general duty" require-
ment to maintain good operating procedures. Brief of Peti-
tioners at 18.

Again, we find that it would be premature for us to decide
this issue now. EPA points to provisions of the Clean Air
Act and implementing regulations seeming to support its view
that compliance is required continuously, not periodically.
Still, the effect of the credible evidence rule on compliance
obligations is difficult to assess without any information or
experience showing how the rule operates in particular set-
tings. For some standards, measuring emission levels at
each and every instant--i.e., on a continuous basis--might
affect stringency in ways that are impossible at this moment
to foretell. We therefore find this issue unripe for review as
well.

Because the merits of petitioners' first set of contentions
are not justiciable, we do not reach their related assertion,
also raised by Battery Council International as intervenor,
that the Clean Air Act Amendments provide no basis for
promulgating the credible evidence rule. Petitioners argue
that s 113(a) of the Act addresses only the initiation of an
enforcement action.4 Although this is a purely legal question,

__________
4 Section 113(a) provides that an action to enforce compliance
may be brought "[w]henever, on the basis of any information

and thus presumably ripe, the need for statutory authority
depends in the first instance on what it is that the credible
evidence rule actually accomplishes. See Toilet Goods, 387
U.S. at 163-64.5

III

Petitioners also challenge EPA's credible evidence addi-
tions to 40 C.F.R. Part 51 (requirements for the preparation,
adoption, and submission of state implementation plans) and
Part 52 (requirements for the approval and promulgation of
implementation plans), claiming that EPA has "violate[d] the
Federal-State division of authority established by [s 110 of
the Act] by requiring States to revise SIPs that EPA has
found are already adequate to implement the Act." Brief of
Petitioners at 28. EPA's revisions inserted language to the
effect that the state plans "must not preclude the use, in-
cluding the exclusive use, of any credible evidence or infor-
mation...." 40 C.F.R. s 51.212; see also id. ss 52.12(c)
(federal enforcement of state plans), 52.33(a) (compliance
certifications). According to petitioners, these changes "ille-
gally invade" the authority of states under the Clean Air
Act. Brief of Petitioners at 48.

During the credible evidence rulemaking, the EPA re-
sponded to comments that these amendments were unautho-
rized by asserting that

__________
available to the Administrator, the Administrator finds that any
person has violated or is in violation of" an applicable standard.
Although s 113(a) is written in terms of finding a violation, the
procedure followed is that the Administrator issues a notice of
violation and then may either issue an administrative order,
s 113(d), or commence a civil action, s 113(b). See 42 U.S.C.
s 7413.

5 If, as EPA maintains, the rule really does not change the
standards, then it might be seen as a permissible exercise of the
agency's general rulemaking authority under s 301 of the Act, 42
U.S.C. s 7601(a)(1). (The agency itself does not rely exclusively on
ss 113(a) and (e), noting that the credible evidence rulemaking was
"based primarily on EPA's existing authority prior to the 1990 CAA
Amendments." 62 Fed. Reg. at 8320.)

EPA is not by this rulemaking revising any SIP; rather,
EPA is amending the rules governing SIPs. Such rules
are promulgated under EPA's authority to (1) require
SIPs to provide adequate enforcement authority (see
sections 110(a)(2)(A), (C), and (E)); (2) call for SIP
revisions to correct inadequacies (see section 110(k)(5));
and (3) "prescribe such regulations as are necessary to
carry out [the Administrator's] functions under this chap-
ter. 42 U.S.C. s 7601.

Response to Comments at 103. EPA's brief explains that it
derived its authority for the rule from s 110(a)(2)(H)(ii),
under which state plans shall "provide for revision" whenever
EPA finds that the plan is "substantially inadequate to ...
comply with any additional requirements established under
this chapter," 42 U.S.C. s 7410(a)(2)(H)(ii), and from the
statutory requirement that state plans must be "enforceable."
Brief of Respondent at 41. This is hard to follow. If state
plans approved by EPA met the enforceability requirement
prior to EPA's adoption of the credible evidence rule, one
may wonder why the state plans have now become "unen-
forceable" to the extent they do not permit the use of credible
evidence. The pre-existing test methods, after all, are still
available to determine compliance. In any event the merits
of this claim are not properly before us.

Regardless whether a state might be able to challenge
directly the revised regulations (no state has), petitioners
cannot do so. Nothing in the amended regulations requires
states to change their implementation plans. That can only
occur through an independent procedure known as a "SIP
call." Under s 110(k)(5), the EPA must notify a state of
inadequacies in its plan and request the submission of a
revised plan. 42 U.S.C. s 7410(k)(5). This begins an exten-
sive regulatory process that includes the publication of a
proposed plan in the Federal Register for notice and com-
ment before final approval by the agency. See Greater
Cincinnati Chamber of Commerce v. EPA, 879 F.2d 1379 (6th

Cir. 1989) (finding that SIP calls do not constitute final
agency action).

This process was set in motion before the promulgation of
the rule challenged here. See 62 Fed. Reg. at 8327. SIP
calls to various states were issued as early as 1994. EPA's
notice to states included draft credible evidence language
that, "if adopted by the State and submitted to EPA for
approval in the SIP, would satisfy the requirements of this
SIP call." 60 Fed. Reg. 46,222, 46,225 (1995) (approving
South Dakota's plan); see also 60 Fed. Reg. 36,361 (1995)
(Kansas); 62 Fed. Reg. 17,081, 17,082 (1997) (Minnesota).
When EPA published the credible evidence rule, it noted that
fifteen states had submitted new plans and several had
already been approved. Thus, the request that state plans be
revised and the submission and approval of revised plans
were not triggered by the amendments to Parts 51 and 52.
In this case, petitioners have challenged neither the SIP calls
nor any of the newly-approved state plans.

Even if we were to assume that revising the regulations
forced the states to submit new plans--something not sug-
gested by the record--we would find petitioners' challenge
unripe. It is not at all apparent that use of credible evidence
alters the emissions standards governing petitioners' activi-
ties. Although the question whether EPA had statutory
authority is a purely legal one, the effect of the credible
evidence rule on petitioners--that is, the effect of language in
state plans specifying that use of credible evidence is not
precluded--is highly uncertain for reasons already men-
tioned. In addition, an amicus brief submitted by state air
pollution authorities indicates that states have historically
used credible evidence and that some state and local air
agencies have relied on credible evidence as the exclusive
basis for enforcement actions. See Brief of Amici Curiae at
4-5. Like the Supreme Court in Toilet Goods, 387 U.S. at
162, we believe that our judicial appraisal "is likely to stand
on a much surer footing in the context of a specific application
of this regulation."

 IV

Battery Council International, as intervenor, claims that
EPA has "attempted unlawfully to revise" its permit shield
regulations in promulgating the credible evidence rule. Brief
of Intervenor at 27.

In the 1990 Amendments, Congress established an operat-
ing permit program for certain sources of air pollution,
including major stationary sources. See 42 U.S.C. ss 7661-
7661f. Under this program, each permit issued must include
all emissions limitations and standards applicable to the
source, as well as provisions concerning inspection, monitor-
ing, compliance certification, and reporting requirements.
The regulations implementing the permit program are con-
tained in 40 C.F.R. Part 70.

Battery Council thinks the following language in EPA's
preamble to the credible evidence rule "would undermine the
principal purpose" of the permits:

[although permits] can include a "permit shield" protect-
ing [a source] from allegations that it has failed to satisfy
CAA monitoring requirements, such shield does not re-
lieve the source of its obligation to comply with the
underlying emission limits or other applicable require-
ments being monitored.... In other words, ... the
source would not be shielded from allegations of noncom-
pliance with the underlying substantive requirements
(e.g., emission limits) being monitored even if the
source's required monitoring failed to detect the viola-
tion.

62 Fed. Reg. at 8320. Battery Council argues that, contrary
to EPA's interpretation, "permit shields also protect sources
from enforcement of 'underlying emission limits,' as long as
sources comply with their permits." Brief of Intervenor at
30.

We will not reach the merits of this argument. The
credible evidence rule did not change any language in Part

70. It is doubtful that the preamble alone is definite and
specific enough to be a binding statement of agency policy.
For one thing, the statements concerning the permit shield
were not published in the Code of Federal Regulations. See
Florida Power & Light, 1998 WL 336520, *4. For another,
EPA has claimed that its statements were no more than "an
interpretation" given "existing permit shield regulation,"
Brief of Respondent at 45, and Battery Council has presented
no evidence that the preamble has a direct and immediate
effect on it. In Kennecott Utah Copper Corp. v. Department
of the Interior, 88 F.3d 1191, 1222 (D.C. Cir. 1996), we held
that although a "preamble may under some circumstances be
reviewable," the preamble challenged there was nevertheless
not ripe because the issue presented was conjectural and "a
more complete understanding of its ramifications must await
a concrete application." The same holds true here. This
challenge is therefore unripe for review.

* * *

Petitioners and intervenor raise a number of other subsid-
iary issues which, while we have considered fully, present no
need for discussion. For the reasons stated above, we dis-
miss the petition for review.

So ordered.