Notice: This opinion is subject to formal revision before publication in the

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bound volumes go to press. 

United States Court of Appeals

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued October 19, 2007 Decided December 11, 2007

No. 06-1164

ENVIRONMENTAL DEFENSE, INC., ET AL.,

PETITIONERS

v.

ENVIRONMENTAL PROTECTION AGENCY AND

STEPHEN L. JOHNSON, ADMINISTRATOR,

RESPONDENTS

On Petition for Review of an Order of the

Environmental Protection Agency

Robert E. Yuhnke argued the cause for petitioners. With

him on the briefs was Joanne M. Spalding.

David J. Kaplan, Attorney, U.S. Department of Justice,

argued the cause for respondents. With him on the brief was

John C. Cruden, Deputy Assistant Attorney General.

Before: GINSBURG, Chief Judge, and ROGERS and BROWN,

Circuit Judges.
2

1

 The court severed Petitioners’ other challenges to the Final

Rule pursuant to a joint motion of the parties in light of settlement

discussions. Envtl. Def. v. EPA, No. 06-1164 (D.C. Cir. June 14,

2007).

Opinion for the Court filed by Circuit Judge ROGERS.

ROGERS, Circuit Judge: Environmental Defense, Inc., the

Natural Resources Defense Council, and the Sierra Club petition

for review of a final rule promulgated by the Environmental

Protection Agency to regulate “hot spot” analyses undertaken as

part of the transportation conformity determinations required by

the Clean Air Act (“CAA”). See PM2.5 and PM10 Hot Spot

Analyses in Project-Level Transportation Conformity

Determinations for the New PM2.5 and Existing PM10 National

Ambient Air Quality Standards (“Final Rule”), 71 Fed. Reg.

12,468, 12,470-74 (Mar. 10, 2006) (to be codified at 40 C.F.R.

pt. 93). Petitioners seek a remand of sections 93.116 and 123(b)

of the Final Rule on the ground that they fail to implement the

conformity conditions in CAA §§ 176(c)(1)(A) and (B)(iii). 

Petitioners also seek vacatur of EPA’s decision to withdraw a

previously announced emissions model from use in “hot spot”

analyses on the ground that EPA failed to give prior adequate

notice or opportunity for comment.1

 We grant the petition in

part and deny it in part. Because petitioners fail to show that

EPA’s interpretation of CAA § 176(c)(1)(A) is unreasonable or

that EPA failed to give adequate notice and opportunity for

comment prior to withdrawing the model, we deny the petition

as to those contentions. However, if “any area” properly means

“a local area” under CAA § 176(c)(1)(B)(i) and (B)(ii), then it

is arbitrary and capricious not to define the term similarly in

(B)(iii) or not to explain why the term there means something

different. We therefore grant the petition and remand the Final

Rule for EPA either to interpret (B)(iii) in harmony with (B)(i)

and (B)(ii) or to explain why it need not do so. 
3

2

 Thus, states must designate an MPO in each urban area with

a population over 50,000 persons. 23 U.S.C. § 134(d). The MPO, in

turn, must prepare a 20-year regional transportation plan, id. at §

134(I), and a transportation improvement program (“TIP”) with a

four-year horizon. Id. at § 134(j). These “plans” and “programs”

I.

Pursuant to the CAA, EPA has established National

Ambient Air Quality Standards (“NAAQS”) that regulate air

contaminants, including particulate matter measuring less than

ten micrometers (“PM10”) and less than 2.5 micrometers

(“PM2.5”). The states, in turn, have prepared State

Implementation Plans (“SIPs”) to “provide[] for

implementation, maintenance, and enforcement of [NAAQS] in

each air quality control region (or portion thereof) . . . .” CAA

§ 110(a)(1), 42 U.S.C. § 7410(a)(1). See generally Envtl. Def.

Fund v. EPA (“EDF II”), 167 F.3d 641, 643-46 (D.C. Cir.

1999); S. Coast Air Quality Mgmt. Dist. v. EPA, 472 F.3d 882,

886-87 (D.C. Cir. 2006). The CAA requires that states be

divided into specific areas, which are rated “nonattainment” if

air quality standards do not comply with the NAAQS,

“attainment” if they do, or “maintenance” if they have passed

from nonattainment to attainment status. CAA

§§ 107(d)(1)(A)(I)-(ii); 3(E), 42 U.S.C. §§ 7407(d)(1)(A)(I)-(ii);

(3)(E). 

The federal conformity rule, first adopted in 1977,

prohibited federal agencies from assisting, supporting, or

approving transportation activities that do not conform to a

state’s SIP. See Criteria and Procedures for Determining

Conformity to State or Federal Implementation Plans, 58 Fed.

Reg. 62,188, 62,189 (Nov. 24, 1993). State-designated

metropolitan planning organizations (“MPOs”) for certain urban

areas, as required by the federal highway law,2

 could not approve
4

identify transportation “projects” that the MPO wants to implement.

See generally 23 U.S.C. §§ 101 et seq.; 49 U.S.C. §§ 5301 et seq.

3

 Section 176(c)(1) provides, in part, that:

No department, agency, or instrumentality of the

Federal Government shall 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 or promulgated under section 7410 of this

title [addressing SIPs].

42 U.S.C. § 7506(c)(1). MPOs similarly may not approve any

“project, program, or plan which does not conform to a [SIP].” Id. 

transportation activities that did not conform to a SIP. Id. In the

years after adoption of the conformity rule, EPA and the U.S.

Department of Transportation (“DOT”) engaged in inconclusive

discussions about whether individual transportation projects that

were part of broader transportation plans implementing SIP

requirements could be approved without further assessments.

EPA argued for additional assessments to evaluate whether

individual projects would affect the attainment of NAAQS in SIP

areas. See, e.g., Letter from Jennifer Joy Wilson, Assistant

Adm’r for External Affairs, EPA & Don R. Clay, Acting

Assistant Adm’r for Air and Radiation, EPA, to Robert E. Farris,

Administrator, Federal Highway Administration, DOT (Nov. 8,

1988). 

In 1990, Congress amended the CAA’s conformity

provisions, requiring EPA and DOT jointly to promulgate

 transportation regulations. As amended, Section 176(c)(1)3

 sets

forth conformity requirements for all activities:
5

Conformity to an implementation plan means–

(A) conformity to an implementation plan’s purpose of

eliminating or reducing the severity and number of

violations of the national ambient air quality standards

and achieving expeditious attainment of such standards;

and

(B) that such activities will not –

(i) cause or contribute to any new violation of any

standard in any area;

(ii) increase the frequency or severity of any

existing violation 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. § 7506(c)(1) (emphases added).

The EPA first invoked its authority under § 176(c)(4), 42

U.S.C. § 7506(c)(4), to promulgate regulations applicable to

transportation projects, in 1993. In relevant part, those

regulations required federal agencies and MPOs to conduct an

analysis of the impact of a transportation project upon carbon

monoxide and PM10 pollution at the local level in nonattainment

and maintenance areas. See 40 C.F.R. § 93.101 (1993). Such an

analysis thus provides information concerning pollutant levels

“on a scale smaller than the entire nonattainment or maintenance

area, including, for example, congested roadway intersections .

. . .” Id. The rule required only a qualitative approach for PM10

“until EPA releases [quantitative] modeling guidance on this

subject and announces in the Federal Register that these

requirements are in effect.” Id. §§ 93.131(d), 51.454(d) (1993);

see also id. § 93.123(b)(4).
6

In November 2003 EPA proposed to amend these

conformity regulations by adopting criteria and procedures for

PM2.5 and revising the hot spot rule for PM10. Notice of

Proposed Rulemaking (“NPRM”), 68 Fed. Reg. 62,690, 62, 712

(Nov. 5, 2003). On December 13, 2004, EPA issued a

supplementary proposal setting forth a number of hot spot

options for PM2.5. Supplemental Notice of Proposed Rulemaking

(“Supplemental NPRM”), 69 Fed. Reg. 72,140, 72,144-45 (Dec.

13, 2004), and for PM10, id. at 72,149-50. EPA proposed to

require only a qualitative analysis for PM2.5 in the first instance,

as it had done for PM10. Id. at 72,145.

Ultimately EPA revised the existing hot spot regulation as

regards PM10 and imposed the same criteria for PM2.5. Final

Rule, 71 Fed. Reg. at 12,470-71 (amending 40 C.F.R. § 93.116).

The new hot spot regulation, which applies in nonattainment and

maintenance areas regardless of the SIP, 40 C.F.R. § 93.116,

now provides that a new transportation project: 

must not [1] cause or contribute to any new

localized CO, PM10, and/or PM2.5 violations or [2]

increase the frequency or severity of any existing

CO, PM10, and/or PM2.5 violations in CO, PM10

and PM2.5 nonattainment and maintenance areas.

This criterion is satisfied . . . if it is demonstrated

that . . . no new local violations will be created

and the severity or number of existing violations

will not be increased as a result of the project.

Final Rule, 71 Fed. Reg. at 12,510 (codified at 40 C.F.R. §

93.116(a)). 

During the rulemaking, Petitioners commented that

proposed § 93.116(a) violated CAA §§ 176(c)(1)(A) and (B)(iii).

They posited that by including only two of the four statutory
7

conformity conditions, the proposed rule failed to require any

finding that the project be consistent with the SIP’s aim of

eliminating all emissions violations and that the project’s

emissions not delay timely attainment and interim progress in

meeting emission milestones. EPA, in response, rejected the

view that the “hot spot” regulation supplants existing

transportation conformity regulations, maintaining instead that

the latter already require transportation projects to be “consistent

with the emissions projections and control measures in the SIP.”

Final Rule, 71 Fed. Reg. at 12,482. According to EPA, the

purpose of “hot spot” regulations is limited to preventing an

increase in the severity or frequency of local violations of

emissions standards, reflecting the mandate of CAA §§

176(c)(1)(B)(i) and B(iii); EPA rejected a construction of CAA

§§ 176(c)(1)(A) and (B)(iii) that would require new individual

projects to reduce emissions as opposed to preventing any new

violations or worsening of existing violations. See id. 

EPA also announced in the Final Rule that a previously

established quantitative emissions model, MOBILE6.2, while

potentially appropriate for quantitative analyses of PM2.5 at the

regional level, was not appropriate for PM2.5 or PM10 hot-spot

analyses. Id. at 12,500. Previously, EPA had stated that

MOBILE6.2 “must be used in all PM2.5 conformity analyses,

until [it is] replaced by newer approved methods or models.”

Notice of Availability (“NOA”), 69 Fed. Reg. 28,830, 28,832

(May 19, 2004). Upon releasing MOBILE6.2, EPA had

explained that the release did not trigger any requirement

quantitatively to analyze PM10 emissions under the hot spot rule.

Id. 

 

II.

Petitioners challenge EPA’s amendment to the “hot spot”

conformity regulation, 40 C.F.R. § 93.116, contending that it
8

unlawfully ignores the requirements of CAA §§ 176(c)(1)(A)

and (B)(iii). Petitioners also challenge EPA’s withdrawal of

MOBILE6.2 for PM2.5 hot spot analyses. 

A. 

As a threshold matter, we hold that insofar as EPA maintains

that Petitioners’ challenge to the Final Rule is time barred

because EPA did not reopen these issues in the rulemaking, its

position is untenable. The final rule applied existing regulatory

criteria to PM10 and PM2.5, and there is a limited period of time

within which an aggrieved party may obtain judicial review of an

EPA rule. In the instant case, however, the notices in the Federal

Register in November 2003 and December 2004 “create[d] the

opportunity for renewed comment [on] and objection” to the “hot

spot” regulation as applied to PM2.5 and PM10. See Ohio v. EPA,

838 F.2d 1325, 1328 (D.C. Cir. 1988). The NPRM “invite[d]

commenters [(sic)] to suggest additional options” for PM10 rules

beyond those EPA proposed. 68 Fed. Reg. at 62,713; see id. at

62,714. The Supplemental NPRM sought comment on the

application of Section 176(c)(1) to PM2.5, stating that “EPA

believes it is important to consider the full range of options for

addressing localized PM2.5 concentrations which may cause or

contribute to any new violation of the PM2.5 standard; increase

the frequency or severity of any existing violation; or delay

timely attainment of the standard.” 69 Fed. Reg. at 72,146. 

EPA’s proposed rulemaking, which discussed five different

options, thus explicitly invited comment on the 1993 conformity

rule and the statutory conformity requirements for projects.

Given its expansive call for comments on the “hot spot”

requirements, EPA cannot plausibly contend that Petitioners’

comments asking that the proposed rule be modified for PM2.5

and PM10 raised issues outside the scope of the rulemaking. Nor

did EPA take that position in responding to Petitioners’
9

comments during the rulemaking. Accordingly, the court may

entertain the petition. 

B.

When incorporating PM2.5 into the hot spot regulations, EPA

did not require that new projects contribute to reducing the

severity and number of local NAAQS violations, as Petitioners

contend CAA § 176(c)(1)(A) requires, and also did not require

that the new projects not delay the timely attainment of

emissions standards or milestones in any local area, as

Petitioners contend CAA § 176(c)(1)(B)(iii) requires. These

additional statutory conditions are important, Petitioners observe,

because “they add the requirement that the project must

contribute to NAAQS compliance by reducing or eliminating

violations, or that measures must be adopted to ensure that

emissions from the project will not interfere with attainment by

delaying the emission reductions needed for attainment beyond

the attainment deadline.” Petr.’s Br. 20. The two conditions in

the Final Rule “only go so far as to prevent projects that will

worsen existing air quality, either by causing new violations

where none currently exist or by contributing to the increased

frequency or severity of violations being caused by emissions

from an existing highway, terminal or other transportation

facility.” Id. at 20-21. Petitioners further contend that when

Congress amended the CAA in 1990 to prescribe conditions it

removed any agency discretion to define the essential conditions

relevant to making a conformity determination and,

consequently, EPA had no authority to waive its statutory duty

to prescribe criteria and procedures to be used by DOT when

making conformity determinations. Id. at 6-10, 23, 33.

EPA does not dispute that it cannot waive the requirements

of CAA §§ 176(c)(1)(A) and (B), see Final Rule, 71 Fed. Reg. at

12,481; Supplemental NOPR, 69 Fed. Reg. at 72,143, but

reiterates its position in the rulemaking that neither provision of
10

the CAA requires individual projects to reduce emissions, see

Final Rule, 71 Fed. Reg. at 12,481. As construed by EPA, these

provisions “only require air quality to not be worsened by an

individual project than what would have otherwise occurred.”

Id. at 12,482. 

We review Petitioners’ challenge to determine whether

EPA’s promulgation of the Final Rule was arbitrary or

capricious, an abuse of discretion, or otherwise not in accordance

with law. See CAA § 307(d)(9)(A), 42 U.S.C. § 7607(d)(9)(A);

see also 5 U.S.C. § 706. Challenges to EPA’s interpretation of

the CAA are governed by the familiar two-pronged test of

Chevron, U.S.A., Inc. v. Natural Resources Defense Council,

Inc., 467 U.S. 837 (1984). Under step one, the court asks

“whether Congress has directly spoken to the . . . issue;” if

Congress’ intent is clear, “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.” Id. at 842-43.

However, if the court determines that “Congress has not directly

addressed the precise question at issue,” id. at 843, then, under

step two, “if the statute is silent or ambiguous with respect to the

specific issue, the question for the court is whether the agency’s

answer is based on a permissible construction of the statute.” Id.

1.

Petitioners contend that CAA § 176(c)(1)(A) adds the

additional temporal condition that a project contributes to

attaining the NAAQS “as expeditiously as practicable.” Petr.’s

Br. 21. In support of their interpretation that subsection (A)

requires emissions reductions, Petitioners point to EDF II, 167

F.3d at 647, where the court stated that “a ‘conforming’ . . .

project is one that will contribute to ‘eliminating or reducing the

severity and number of violations of the [NAAQS] . . . .’” Id.

(citing 42 U.S.C. § 7506(c)(1)(A)). We conclude that Petitioners

have not shown that subsection (A) applies to “hot spots” or that
11

4 EDF I’s interpretation of CAA § 176(c)(1)(A) was recently

reaffirmed by Environmental Defense v. EPA (“EDF III”), 467 F.3d

1329, 1339 (D.C. Cir. 2006), although it too does not speak to the

antecedent question of whether subsection (A) requires a “hot spot”

analysis.

EPA’s contrary position is arbitrary or capricious or contrary to

the statute.

Subsection (A) provides that activities shall “conform[] to

an implementation plan’s purpose.” The statute defines an

implementation plan in regional terms by state, not as a localized

area. See CAA § 107(b), 42 U.S.C. § 7407(b). To the extent that

subsection (A), on its face, does not apply to the immediate “area

substantially affected by [a] project,” cf. 40 C.F.R. § 93.101, it

is unnecessary to reach the question of what subsection (A) may

require by way of emissions reduction. But to the extent that

subsection (A) is ambiguous because of the reference in CAA

§ 176(c)(1)’s introductory clause to “project, program, or plan,”

Petitioners fail to show that EPA’s interpretation is not “a

permissible construction of the statute.” Chevron, 467 U.S. at

843. 

EPA interprets the conditions in subsection (A) to be “met

if a transportation project is consistent with the emissions

projections and control measures in the SIP.” Final Rule, 71

Fed. Reg. at 12,482. In the preamble to the Final Rule, EPA

explained that “[a]lthough . . . transportation projects need to be

consistent with a SIP’s purpose of reducing violations, this can

be accomplished by simply not increasing violations . . . .” Id.

(citing Envtl. Def. Fund v. EPA (“EDF I”), 82 F.3d 451 (D.C.

Cir. 1996)).4

 According to EPA, so long as air quality

concentrations in the entire SIP area are not worsened as the

result of a transportation project, subsection (A) is satisfied.

Consistent with subsection (A)’s focus on the SIP as a whole by
12

contrast with the express attention to “any area” in

§ 176(c)(1)(B), EPA has never taken the position that subsection

(A) applies to a “hot spot.” For example, in the Supplemental

NPRM, EPA cited subsection (B) as the basis for requiring

conformity analysis at PM “hot spots.” See 69 Fed. Reg. at

72,146. 

Petitioners view CAA § 176(c)(2) as the statutory scheme

for regional emissions conformity based on the SIP and CAA

§ 176(c)(1) as the scheme for local “hot spot” conformity based

on the NAAQS. Petitioners accordingly assert that EPA has

violated the statute because subsection (A) requires something

different than subsection (B). But Petitioners presuppose that

subsection (A) applies locally without showing that it does.

Although Petitioners correctly note that subsection (A) applies

to ‘any project,’ that does not determine whether a project must

satisfy the conditions in subsection (A) at the local or the

regional level. EPA has taken the latter view, and Petitioners

have not established that its interpretation is contrary to the

statute or unreasonable. 

2.

More persuasive is Petitioners’ contention that EPA acted

arbitrarily and contrary to law by not requiring conformity

determinations for individual projects to meet the conditions of

CAA § 176(c)(1)(B)(iii) at the local level. CAA § 176(c)(1)

defines “conformity” as involving “activities” that occur “in any

area” — a phrase that appears in each of subsection (B)’s

subparts. EPA includes in the Final Rule the requirements for

individual projects to comply with the conditions in (B)(i) and

(B)(ii) at the local level, see 40 C.F.R. § 93.101, but does not do

so for (B)(iii)’s conditions. EPA provides no reason for

interpreting “any area” as meaning “a local area,” i.e., “hot

spots,” in (B)(i) and (B)(ii) but not in (B)(iii). 
13

 EPA maintains on appeal that the Final Rule, along with the

broader regulatory framework and the SIP process can satisfy the

requirements of (B)(iii). Because it interprets the statute not to

require each project to reduce emissions, EPA asserts that it is

not necessary to include (B)(iii)’s conditions in the Final Rule.

See Final Rule, 71 Fed. Reg. at 12,482. However, under EPA’s

revision of the “hot spot” regulations, an individual project’s

emissions could counterbalance mitigation measures already in

place, thereby delaying attainment of emissions standards and

violating the requirement of (B)(iii) without either increasing or

decreasing emissions. EPA’s position thus does not seem to

cover all circumstances where (B)(iii) is applicable. 

Even assuming (B)(iii) is ambiguous, EPA’s reliance on the

SIP process would appear to be arbitrary and capricious for

failure to establish “a rational connection between the facts

found and choice made.” Tourus Records, Inc. v. DEA, 259 F.3d

731, 736 (D.C. Cir. 2001) (quotations omitted). In the preamble

to the Final Rule EPA acknowledged that it “does not anticipate

requiring PM2.5 SIP modeling to be performed at a level of detail

that would identify all potential transportation hot spots” and

noted comments by State and Territorial Air Pollution Program

Administrators expressing “concerns regarding the ability of the

SIP to evaluate the local air quality impacts of all future projects

. . . .” Final Rule, 71 Fed. Reg at 12,476. So understood, and in

view of the generous time periods associated with the SIP

process as outlined in EPA’s brief, see Resp.’s Br. at 33, it is

likely that SIP-based enforcement of (B)(iii)’s conditions would

be post-hoc and subject to delays. See, e.g., CAA §§ 110(c) &

(k)(5), 42 U.S.C. §§ 7410(c) & (k)(5). The statutory prohibition

on projects that cause delays in attaining emissions standards

would effectively be stripped of almost any impact and be

inconsistent with Congress’s intent that pollution production be

prevented by forward planning. Thus, even were we to treat the

text as ambiguous, EPA has failed to create a rational link
14

between the requirements of (B)(iii) and the regulatory

framework or the SIP process. 

The fundamental problem, however, is that if, as EPA posits

in the Final Rule, “any area” in (B)(i) and (B)(ii) properly means

“a local area” under either Chevron step one or step two, then it

is arbitrary and capricious not to define the term similarly in

(B)(iii) or not to provide an explanation that satisfactorily

addresses the purpose and function of the condition. EPA’s

explanation, that individual projects are not required to reduce

emissions, does not address this inconsistency. A remand is

therefore required for EPA either to interpret (B)(iii) in harmony

with (B)(i) and (B)(ii) or to explain why it need not do so. 

3.

Petitioners also contend that EPA erred procedurally when,

without giving adequate notice or soliciting comments, it

declined to require that MPOs and federal agencies perform a

quantitative analysis of PM2.5 emissions at the local level using

MOBILE6.2, a previously approved emissions model.

Petitioners point to EPA’s prior approval of MOBILE6.2 for

such analysis in the 2004 NOA. See 69 Fed. Reg. at 28,832. 

EPA responds that judicial review of this procedural issue

is barred because Petitioners did not raise it with “reasonable

specificity” in their comments before the agency. See CAA

§ 307(d)(7)(B), 42 U.S.C. § 7607(d)(7)(B). Notwithstanding our

ordinarily “strict[]” application of CAA § 307(d)(7)(B), see

Motor & Equip. Mfrs. Ass’n v. Nichols, 142 F.3d 449, 462 (D.C.

Cir. 1998), it is inapplicable here. Pursuant to § 307(d)(1)(V), 42

U.S.C. § 7607(d)(1)(V), EPA acted to make CAA § 307(d)

applicable to this rulemaking only upon promulgation of the

Final Rule. See Final Rule, 71 Fed. Reg. at 12,509-10.

Petitioners had no prior notice that EPA would take this step; in

this circumstance CAA § 307(d)(7)(B) does not require that a
15

procedural issue first be presented to the agency. See also Nw.

Envtl. Def. Ctr. v. Bonneville Power Admin., 117 F.3d 1520,

1535 (9th Cir. 1997).

On the merits, however, Petitioners’ contention fails for we

find no procedural error. In the Supplemental NPRM, which

followed the NOA release of MOBILE6.2, EPA provided

sufficient notice and comment opportunities. EPA there

specifically “propose[d] to extend the current rule’s

§ 93.123(b)(3) and (b)(4) requirements with respect to PM2.5.”

Supplemental NPRM, 69 Fed. Reg. at 72,145. Section

93.123(b)(4) then provided that “[t]he requirements for

quantitative analysis [of PM10] will not take effect until EPA

releases modeling guidance on this subject and announces in the

FEDERAL REGISTER that these requirements are in effect.” The

Supplemental NPRM also advised that “[i]f EPA finalizes an

option that would require quantitative and/or qualitative PM2.5

hot spot analyses, we would provide guidance and appropriate

models for carrying out such analyses in a timely manner.” 69

Fed. Reg. at 72,146. Petitioners objected to this proposed delay

in quantitative analysis, noting the previously established

availability of MOBILE6.2 and EPA’s Technical Guidance on

the Use of MOBILE6.2 for Emission Inventory Preparation;

other commentators raised similar objections. EPA responded,

explaining in the preamble to the Final Rule that, in view of its

“technical limitations,” MOBILE6.2 was inappropriate for use in

performing local analyses because it “will produce inaccurate

results in some cases,” which EPA described. Final Rule, 71

Fed. Reg. at 12,499; see also id. at 12,498-502. This exchange

demonstrates that EPA complied with the requirements of notice

and comment rulemaking. 

Accordingly, we grant the petition in part and remand the

Final Rule to EPA either to interpret CAA § 176(c)(1)(B)(iii) in
16

harmony with (B)(i) and (B)(ii) or to explain why it need not do

so; we otherwise deny the petition.