Catawba County v. EPA

No. 05-1064 Consolidated with 05-1065, 05-1067, 05-1068,

05-1069, 05-1071, 05-1072, 05-1073, 05-1075, 05-1076,

05-1077, 05-1078, 05-1184, 05-1190, 05-1196, 05-1200,

05-1202, 06-1049, 06-1052, 06-1083, 06-1088, 06-1102,

06-1172, 07-1412, 07-1417, 07-1418, 07-1428, 07-1465,

07-1467, 07-1530

UNITED STATES COURT OF APPEALS FOR THE DISTRICT OF COLUMBIA

CIRCUIT

571 F.3d 20; 387 U.S. App. D.C. 20; 2009 U.S. App. LEXIS

14948; 69 ERC (BNA) 1033; 39 ELR 20143

April 6, 2009, Argued

July 7, 2009, Decided

[*25] PER CURIAM: In these

consolidated petitions, several

states, counties, and industrial

entities challenge the Environmental

Protection Agency's promulgation of

area designations for the annual

national ambient air quality standard

applicable to fine particulate matter,

a category of air pollutants

consisting of miniscule airborne

particles known to present adverse

health risks. Insisting that EPA's

methodology for designating areas as

"nonattainment" for the fine

particulate matter standard violates

section 107(d) of the Clean Air Act,

which governs such designations, and

that this methodology and the

individual designations it produced

are otherwise arbitrary and

capricious, petitioners ask us to

vacate the nonattainment designations

and to send EPA back to the drawing

board. With one minor exception, we

deny the petitions for review. Faced

with the complex task of identifying

those geographic areas that contribute

to fine particulate matter pollution,

EPA both complied with the statute

and, for all but one of the 225

counties or partial counties it

designated as nonattainment,

satisfied--indeed, quite often

surpassed--its basic obligation of

reasoned decisionmaking.

I.

Title I of the Clean Air Act

charges EPA with formulating national

ambient air [*26] quality standards

(NAAQS) for air pollutants that may

reasonably be anticipated to endanger

public health and welfare. 42 U.S.C.

§§ 7408-09. NAAQS set maximum ambient

air concentrations for those

pollutants. Id. While each state has

"primary responsibility for assuring

air quality" within its borders and,

in particular, for developing a state

implementation plan (SIP) for

achieving and maintaining the NAAQS

for each air pollutant, 42 U.S.C. §

7407(a), the Act triggers more or less

stringent requirements depending on

the quality of an area's ambient air.

Thus, before a state can design an

appropriate SIP, it must know which

areas within its boundaries comply

with the NAAQS and which do not.

This is where CAA section 107(d)

comes in. It requires EPA to designate

areas as "attainment,"

"nonattainment," or "unclassifiable"

depending on their compliance with the

relevant NAAQS. "Attainment" areas are

those that meet the relevant standard;

"nonattainment" areas are those that

exceed the standard or that

"contribute[] to ambient air quality

Page 1
in a nearby area" that exceeds the

standard; "unclassifiable" areas are

those that permit no determination

given existing data. §

7407(d)(1)(A)(i)-(iii). In

nonattainment areas, the Act requires

stricter pollution controls. For

instance, states must implement

controls that will achieve attainment

"as expeditiously as practicable" in

nonattainment areas, id. § 7502(a),

(c)(1), whereas states need only

implement measures that will prevent

"significant deterioration of air

quality" for attainment and

unclassifiable areas, id. § 7471.

In addition to setting the criteria

for attainment and nonattainment,

section 107(d)(1) prescribes the

designation process. Upon promulgation

of new or revised NAAQS, states must

submit to EPA their own "initial

designations" of all areas within

their borders. § 7407(d)(1)(A). EPA

must then promulgate the submitted

designations or modify them as it

deems necessary. § 7407(d)(1)(B).

Specifically, CAA section

107(d)(1)(B)(ii) provides that:

In making the promulgations

required . . ., the

Administrator may make such

modifications as the

Administrator deems

necessary to the

designations of the areas

(or portions thereof)

submitted [by the states]

under subparagraph (A)

(including to the boundaries

of such areas or portions

thereof). Whenever the

Administrator intends to

make a modification, the

Administrator shall notify

the State and provide such

State with an opportunity to

demonstrate why any proposed

modification is

inappropriate. The

Administrator shall give

such notification no later

than 120 days before the

date the Administrator

promulgates the designation,

including any modification

thereto.

§ 7407(d)(1)(B)(ii).

This case involves the NAAQS for

fine particulate matter. Known as

PM[2.5], fine particulate matter

consists of airborne particles that

are 2.5 micrometers in diameter or

smaller--i.e., less than one-thirtieth

the thickness of a human hair. Air

Quality Designations and

Classifications for the Fine Particles

(PM2.5) National Ambient Air Quality

Standards ("PM[2.5] Designations

Rule"), 70 Fed. Reg. 944, 945 (Jan. 5,

2005) (codified at 40 C.F.R. pt. 81).

A "significant association" links

elevated levels of PM[2.5] with

adverse human health consequences such

as premature death, lung and

cardiovascular disease, and asthma.

Id. And significantly for the primary

issue before us--EPA's method for

identifying the geographic origins of

elevated ambient PM[2.5]

concentrations--PM[2.5] can travel

hundreds or thousands of miles.

In 1997, EPA abandoned its practice

of regulating all particulate matter,

both [*27] coarse and fine, under a

unified standard. Instead it

established specific PM[2.5] NAAQS for

the first time. National Ambient Air

Quality Standards for Particulate

Matter, 62 Fed. Reg. 38,652 (July 18,

1997). EPA promulgated annual and

24-hour PM[2.5] NAAQS, setting the

annual standard--the one at issue

here--at 15 micrograms per cubic

meter. Id. at 38,677; see also 40

C.F.R. § 50.7. Although section 107(d)

required EPA to promulgate area

designations for the new standard "as

expeditiously as possible," §

7407(d)(1)(B)(i), litigation here and

in the Supreme Court waylaid the

designation process until we finally

upheld the standard five years later.

See Am. Trucking Ass'ns v. EPA, 283

F.3d 355, 350 U.S. App. D.C. 254 (D.C.

Page 2

571 F.3d 20, *26; 387 U.S. App. D.C. 20;

2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
Cir. 2002), on remand from Whitman v.

Am. Trucking Ass'ns, 531 U.S. 457, 121

S. Ct. 903, 149 L. Ed. 2d 1 (2001),

aff'g in part and rev'g in part Am.

Trucking Ass'n v. EPA, 175 F.3d 1027,

336 U.S. App. D.C. 16 (D.C. Cir.

1999). In the meantime, Congress had

passed legislation requiring the

deployment of a nationwide PM[2.5]

monitoring network and extending the

deadline for the designations until

three years of monitoring data had

been collected. See Transportation

Equity Act for the 21st Century

("TEA-21"), Pub. L. No. 105-178, §§

6101-02, 112 Stat. 107, 463-65 (1998).

Then, following our decision upholding

the PM[2.5] NAAQS and EPA's initiation

of the designation process, Congress

amended the Clean Air Act to add

section 107(d)(6), which set a firm

deadline for the PM[2.5] area

designations. See Pub. L. No. 108-199,

§ 425(a), 118 Stat. 3, 417 (2004)

(codified at § 7407(d)(6)). Thus,

amended section 107(d)(6)(A) now

provides:

Notwithstanding any other

provision of law, not later

than February 15, 2004, the

Governor of each State shall

submit designations referred

in paragraph (1) for the

July 1997 PM[2.5] national

ambient air quality

standards for each area

within the State, based on

air quality monitoring data

collected in accordance with

any applicable Federal

reference methods for the

relevant area.

§ 7407(d)(6)(A). And section

107(d)(6)(B) provides:

Notwithstanding any other

provision of law, not later

than December 31, 2005, the

Administrator shall,

consistent with paragraph

(1), promulgate the

designations referred to in

subparagraph (A) for each

area of each State for the

July 1997 PM[2.5] national

ambient air quality

standards.

§ 7407(d)(6)(B).

In April 2003, EPA issued a

guidance document initiating the

PM[2.5] designation process. Known as

the Holmstead Memo, the document

explains the timeline for state

submissions and, more importantly, the

criteria EPA would employ in reviewing

those submissions. Memorandum from

Jeffrey R. Holmstead, Assistant

Administrator, to Regional

Administrators, Regions I-X (Apr. 1,

2003) ("Holmstead Memo"). Noting

"recent evidence that violations of

the PM[2.5] air quality standards

generally include a significant

urban-scale contribution," the

Holmstead Memo explains EPA's

"inten[t] to apply a presumption that

the boundaries for urban nonattainment

areas should be based on Metropolitan

Area boundaries." Id. at 2. In other

words, the Memo announces EPA's view

that if any area within a metropolitan

area exceeds the annual PM[2.5] NAAQS,

then all areas within the metropolitan

area presumptively "contribute" to

that violation within the meaning of

section 107(d)(1)(A) and therefore

warrant "nonattainment" designations.

The Holmstead Memo further explains

that EPA would define metropolitan

boundaries by reference to Office of

Management and Budget definitions of

metropolitan statistical areas (MSAs)

and consolidated metropolitan [*28]

statistical areas (CMSAs)

(interchangeably, "C/MSAs"). Id. Thus,

under this approach, a violation of

the PM[2.5] NAAQS in the District of

Columbia, for instance, would trigger

the presumption that seventeen

counties in northern Virginia and five

counties in Maryland--all inside the

applicable MSA, though only some are

contiguous with the

District--contribute to elevated

PM[2.5] levels in the city and warrant

"nonattainment" designations.

Page 3

571 F.3d 20, *27; 387 U.S. App. D.C. 20;

2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
An attachment to the Holmstead Memo

elaborates on EPA's basis for adopting

the presumption, as well as the

circumstances that would warrant a

departure. As to the rationale for the

presumption, the Holmstead Memo

explains that after "examin[ing] the

geographic distribution of total

PM[2.5] concentrations in and near

many metropolitan areas," the agency

had "found an association of higher

PM[2.5] concentrations with greater

levels of urban activity" such as

"motor vehicle use and home heating[,]

as well as industrial activities."

Holmstead Memo, Attach. 2, Guidance on

Nonattainment Area Designations for

PM[2.5], at 4-5 ("Holmstead Memo

Guidance"). Thus, "[the] presumption

reflects EPA's view that, in the

absence of evidence to the contrary,

violations of the PM[2.5] NAAQS in

urban areas may be presumed

attributable at least in part to

contributions from sources distributed

throughout the Metropolitan Area." Id.

at 5. That said, the Holmstead Memo

also recognizes that appropriate

boundaries of urban nonattainment

areas may well be smaller or larger

than the applicable C/MSA. EPA would

therefore "consider requests for urban

nonattainment area definitions that

deviate from OMB's metropolitan area

definitions on a case-by-case basis."

Id. at 6. The Holmstead Memo lists

nine factors to guide that

case-by-case analysis: (1) emissions

in the potentially contributing areas;

(2) air quality in those areas; (3)

population density and degree of

urbanization in those areas; (4)

traffic and commuting patterns; (5)

expected growth; (6) meteorology; (7)

geography and topography; (8)

jurisdictional boundaries; and (9)

level of control of emissions sources.

Id. at 7. The Memo encourages states

submitting designations that depart

from the metropolitan presumption to

justify such designations by reference

to all nine factors. Id.

With that, the designation process

was underway. The states submitted

their initial designations; EPA

responded with its proposed

modifications, as well as explanations

of its analysis under the nine-factor

test; the states then submitted any

responses; and EPA promulgated the

final area designations in December

2004. See PM[2.5] Designations Rule,

70 Fed. Reg. at 946. In a technical

support document accompanying the

Rule, EPA explained the basis for the

designations and the analytical tools

that it had developed and applied to

assess the nine factors. See EPA,

Office of Air Quality Planning and

Standards, Technical Support Document

for State and Tribal Air Quality Fine

Particle (PM2.5) Designations (2004)

("Technical Support Document").

Recognizing that 2004 monitoring data

would soon become available, EPA also

invited states to submit any new data

that might support an amended

designation. PM[2.5] Designations

Rule, 70 Fed. Reg. at 948. Based on

the new data, EPA then revised

designations for eight areas from

nonattainment to attainment and four

areas from unclassifiable to

attainment. See Air Quality

Designations for the Fine Particles

(PM2.5) National Ambient Air Quality

Standards--Supplemental Amendments, 70

Fed. Reg. 19,844, 19,844 (Apr. 14,

2005) (codified at 40 C.F.R. pt. 81).

In the end, EPA applied the C/MSA

presumption so that nonattainment

boundaries [*29] were coextensive

with metropolitan boundaries (and

unchanged by the nine-factor analysis)

in only seven of thirty-nine

metropolitan areas. See EPA Br. 54

(citing relevant portions of the

Technical Support Document). In every

other metropolitan area, applying the

nine-factor analysis and finding that

the presumption misjudged the nature

of the PM[2.5] problem, EPA designated

the urban nonattainment area as either

an area larger than the OMB-defined

metropolitan area (for instance, in

Chattanooga, Tennessee) or smaller

(for instance, in Washington, DC).

Page 4

571 F.3d 20, *28; 387 U.S. App. D.C. 20;

2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
Several states, local governments,

and industrial entities petitioned EPA

for reconsideration of the

designations; others filed petitions

for review directly in this court. We

stayed proceedings in this court while

EPA considered the petitions for

reconsideration. Once EPA resolved the

petitions for reconsideration, we

consolidated all petitions for review.

Petitioners' challenges fall into

four broad categories. First, they

raise procedural challenges to the

Holmstead Memo and to the Designations

Rule, arguing that EPA illegally

bypassed notice and comment for each.

Second, they raise various objections

to EPA's statutory authority to adopt

and implement the C/MSA presumption

and the nine-factor test. Third, they

argue that even if section 107(d)

permits EPA to adopt the C/MSA

presumption and the nine-factor test,

EPA's analysis nonetheless suffers

from such serious methodological

deficiencies and inconsistencies as to

render the entire Designations Rule

arbitrary and capricious. Finally, as

a last resort, petitioners request

that we vacate certain area

designations that affect them,

claiming that EPA at least acted

arbitrarily and capriciously in making

these particular nonattainment and

unclassifiable designations. We review

petitioners' challenges under section

307(d)(9) of the Clean Air Act, which

requires the court to set aside EPA's

final actions when they are in excess

of the agency's statutory authority or

otherwise arbitrary and capricious. 42

U.S.C. § 7607(d)(9)(A).

II.

Before addressing petitioners'

arguments, however, we think it

helpful to review some technical

background.

Fine particulate matter includes

both "primary" particles (e.g.,

carbonaceous particles and so-called

"crustal" particles like dust) that

pollution sources emit directly into

the atmosphere, as well as "secondary"

particles (e.g., sulfate and nitrate

particles) that form in the atmosphere

as a result of chemical reactions

between PM[2.5] precursors that

sources emit. PM[2.5] Designations

Rule, 70 Fed. Reg. at 945. Power

plants, diesel and gasoline powered

engines in mobile sources like cars

and trucks, and other industrial

sources produce most carbonaceous

particles; agriculture, mining, and

other activities that cause soil or

metals to be suspended in the

atmosphere account for the crustal

component. See Technical Support

Document § 3.1; EPA, Office of Air

Quality and Planning Standards, The

Particle Pollution Report 6 (2004),

available at

http://www.epa.gov/air/airtrends/aqtrnd0

4/pm. html. The chemical precursors to

secondary PM[2.5] include sulfur

dioxide (SO[2]), emitted in

substantial part by power plants;

nitrogen oxides (NO[x]), emitted in

substantial part by mobile sources,

power plants, and other industrial

sources; and ammonia, emitted from

agricultural sources, mobile sources,

and power plants. See PM[2.5]

Designations Rule, 70 Fed. Reg. at

945; Technical Support Document § 3.1.

Atmospheric chemical reactions between

these gases yield secondary PM[2.5] in

the form of sulfate and nitrate

particles. PM[2.5] Designations Rule,

70 Fed. Reg. at 945. [*30] The

PM[2.5] NAAQS set a 15 [mu] g/m<3>

annual limit for all fine particulate

matter without distinguishing among

the various kinds (or "species") of

PM[2.5]. Even so, "speciation data"

that breaks the total PM[2.5]

concentration into its constituent

components is quite useful for the

area designation process. Because such

data reveals the kinds of particles

(carbon, sulfate, nitrate, crustal

particles, etc.) that most account for

an area's PM [2.5] problem, it

suggests, by extrapolation, the kinds

of sources most responsible for the

problem as well.

Page 5

571 F.3d 20, *29; 387 U.S. App. D.C. 20;

2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
While the Holmstead Memo announced

EPA's methodology for determining

whether an area with passable PM[2.5]

concentrations nonetheless deserves a

"nonattainment" designation, EPA

regulations set forth the technical

procedures for measuring ambient

PM[2.5] concentrations in the first

place. Exhaustive technical

specifications regulate the states'

operation of a network of air monitors

that collect air quality data for any

given area. See 40 C.F.R. pt. 50,

Apps. L, N. These monitors measure

ambient PM[2.5] concentration, what's

called the "design value," on any

given day. The annual design

value--which determines whether an

area complies with the PM[2.5]

standard--is then computed by

averaging every quarter's worth of

daily design value samples (typically

collected every third or sixth day),

averaging those quarterly numbers to

obtain an annual average, and then

averaging three years of annual

numbers to yield the final annual

design value. See 40 C.F.R. pt. 50,

App. N. Samples from these monitors

can be further analyzed to yield the

speciation data described above.

The majority of the PM[2.5]

designations at issue here drew on

monitoring data collected from 2001 to

2003. Based on a judgment that no

petitioner challenges, EPA decided

that "the county boundary . . .

[would] determin[e] the extent of the

area reflected by [a violating]

PM[2.5] monitor." PM[2.5] Designations

Rule, 70 Fed. Reg. at 946; see also

id. at 946-47 ("[I]f a PM2.5 monitor

was violating the standard based on

the 2001-2003 data, at a minimum we

designated the county where that

monitor is located as nonattainment.

We made exceptions . . . in a few very

large western counties where a

significant geographic feature such as

a mountain range divided a county. . .

."). Thus, for instance, if a monitor

in an industrial area of downtown

Detroit registered a violation, all of

Wayne County would be designated as

nonattainment--including even its more

idyllic corners like the town of

Grosse Pointe. Cf. id. at 980

(designating Wayne County

nonattainment). To be clear, this

reflects quite a separate judgment

from that underlying the C/MSA

presumption. EPA's selection of the

county as the unit of analysis

resolved a problem inherent in the

monitoring process, namely, that a

monitor only measures air quality in

its immediate vicinity. Because of

this, EPA had to determine how much

compass to give any monitored

measurement, which it did by choosing

the county as the unit of analysis.

The C/MSA presumption, by contrast,

addresses a different problem, namely,

how to identify those areas that,

although deemed to be meeting the

standard themselves, are contributing

to nearby violations.

We've already described the nine

factors that EPA evaluated to

determine whether to depart from the

C/MSA presumption, see supra at 8, and

in the hundreds of pages that comprise

the Technical Support Document, EPA

explained its findings for each

metropolitan area on each of the nine

factors. EPA assessed these factors

with the help of several analytical

tools and models it had developed. See

Technical Support Document §§ 3.0-5.9

(explaining analytical tools). We

describe the most [*31] important

ones here in general fashion,

reserving additional elaboration for

those portions of the opinion that

require it.

To start, given the hundreds of

miles that PM[2.5] can travel in the

atmosphere, EPA thought it important

to isolate the portion of urban

PM[2.5] that originates from a

metropolitan area's local sources as

opposed to regional sources much

farther away. Thus, under its "urban

excess" analysis, EPA paired an urban

monitoring site with an upwind rural

monitoring site--i.e., a rural site

where prevailing winds move in the

Page 6

571 F.3d 20, *30; 387 U.S. App. D.C. 20;

2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
direction of the metropolitan

area--and "subtract[ed] the rural

concentration from the measured urban

concentration." Id. § 3.1. True to

name, this simple arithmetic allowed

EPA to estimate the portion of urban

PM[2.5] levels that arises from urban

activities by cancelling out the

"rural background" that would exist

regardless of those activities. Id.

EPA calculated the urban excess for

each PM[2.5] species and then summed

those numbers to yield a total urban

excess measure. Id. § 3.2.

EPA next used the urban excess

calculations to develop "weighted

emissions scores" for each county in a

C/MSA. Id. § 4.0. The notion

underlying these scores is intuitive:

if the urban excess numbers for the

District of Columbia, for instance,

reveal that all local PM[2.5]

pollution is in the form of carbon, it

would make little sense to think that

a C/MSA county plays a significant

part in the District's monitored

violation if the county has zero

carbon emissions. Thus, for purposes

of evaluating the first of the nine

factors--the "emissions in areas

potentially included versus excluded,"

Holmstead Memo Guidance at 7--EPA

determined that raw emissions data is

usually less suggestive of

contribution than data adjusted to

account for the PM[2.5] species that

actually comprise the urban excess.

Calculating weighted emissions

scores required a number of steps. See

Technical Support Document §§ 4.1-4.3.

First, EPA determined the total

metropolitan emissions of carbon,

SO[2], NO[x], and crustal particles by

summing the counties' individual

emissions of each pollutant. For those

pollutants, EPA then divided each

county's emissions by total C/MSA

emissions, calculating each county's

percentage share of total metropolitan

emissions. For example, if County A

emits 50 tons of carbon and total

C/MSA carbon emissions equal 100 tons,

then the ratio would be fifty percent.

Next EPA "weighted" these percentages

by multiplying them by the proportion

of urban excess attributable to the

relevant pollutant. To continue with

our hypothetical, then, if carbon

accounted for forty percent of urban

excess, EPA would multiply fifty

percent by four-tenths, and County A's

weighted carbon score would be twenty.

Having calculated a county's weighted

scores for each PM[2.5] species, EPA

then added these scores together to

derive a county's total weighted

emissions score. Importantly, because

these scores scale a county's raw

emissions based on attributes specific

to an individual C/MSA--i.e., the

urban excess number and the total

level of metropolitan emissions--they

only provide a measure for comparing

counties within the same C/MSA.

Finally, EPA developed so-called

"pollution roses" that depict

2001-2003 monitoring and

meteorological data for each PM[2.5]

air monitor. See, e.g., Technical

Support Document 6-11 to -12. Each

pollution rose consists of concentric

circles, with the circles' center

representing the location of the air

monitor. EPA then plotted dots around

the circles, with each dot

representing one monitored reading,

the dot's size representing the

magnitude of the reading, the dot's

spatial location representing the

prevailing wind direction on [*32]

the day of the reading, and the dot's

distance from the center of the circle

representing the average wind speed on

that day.

With this technical background in

mind, we turn to petitioners' four

primary arguments.

III.

Petitioners first lodge procedural

challenges against EPA's promulgation

of the final designations rule and the

Holmstead Memo. Petitioners argue that

EPA violated the Administrative

Procedure Act, 5 U.S.C. § 553, by

Page 7

571 F.3d 20, *31; 387 U.S. App. D.C. 20;

2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
failing to publish both the Rule and

the Holmstead Memo for notice and

comment. They are in error as to both.

A. Final Designations Rule

Designation of nonattainment areas

is governed by section 107(d) of the

Clean Air Act. § 7407(d). The parties

disagree as to which subsection of

section 107(d) provides EPA's

authority to promulgate designations.

Industry petitioners argue that

designations are promulgated under

section 107(d)(6), which states:

"Notwithstanding any other provision

of law, not later than December 31,

2004, the Administrator shall,

consistent with paragraph (1),

promulgate the designations referred

to in subparagraph (A) for each area

of each State for the July 1997

PM[2.5] national ambient air quality

standards." § 7407(d)(6)(B). By

contrast, EPA argues that the source

of its authority is a provision of

section 107(d)(1), entitled

"Promulgation by EPA of designations,"

which states in relevant part:

Upon promulgation or

revision of a national

ambient air quality

standard, the Administrator

shall promulgate the

designations of all areas

(or portions thereof)

submitted under subparagraph

(A) as expeditiously as

practicable, but in no case

later than 2 years from the

date of promulgation of the

new or revised national

ambient air quality

standard.

§ 7407(d)(1)(B)(i). The distinction

between these provisions is important

because the statute exempts

designations under section 107(d)(1),

among others, from the APA's section

553 notice-and-comment requirements;

it does not, however, exempt

designations under section 107(d)(6).

See § 7407(d)(2)(B) ("Promulgation or

announcement of a designation under

paragraph (1), (4) or (5) shall not be

subject to the provisions of sections

553 through 557 of title 5 of the

United States Code (relating to notice

and comment), except nothing herein

shall be construed as precluding such

public notice and comment whenever

possible.").

EPA is entrusted with administering

the Clean Air Act, of which section

107 is a part, and thus we review the

agency's construction of the statutory

provisions under the familiar two-step

framework set out in Chevron U.S.A.

Inc. v. Natural Resources Defense

Council, 467 U.S. 837, 104 S. Ct.

2778, 81 l. Ed. 2d 694 (1984). Under

Chevron step one, we ask "whether

Congress has directly spoken to the

precise question at issue." Id. at

842. If at that point we determine

that "the intent of Congress 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. We proceed to Chevron's second

step only "if the statute is silent or

ambiguous with respect to the specific

issue." Id. at 843. At the second

step, we determine "whether the

agency's answer is based on a

permissible construction of the

statute." Id.

Here we need go no further than the

first step because the intent of

Congress is clear. Petitioners'

reliance on section 107(d)(6) is

misplaced. Subparagraph (B) of section

107(d)(6) [*33] requires that, "not

later than December 31, 2004, the

Administrator shall . . . promulgate

the designations referred to in

subparagraph (A)." § 7407(d)(6)(B).

Subparagraph (A), in turn, states:

"Notwithstanding any other provision

of law, not later than February 15,

2004, the Governor of each State shall

submit designations referred to in

paragraph (1) [of § 7407(d)] for the

July 1997 PM[2.5] national ambient air

quality standards . . . ." §

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
7407(d)(6)(A) (emphasis added). Thus,

contrary to petitioners' claim,

section 107(d)(6)(B), when read in

conjunction with section 107(d)(6)(A),

shows that section 107(d)(6) does not

itself authorize the promulgation of

designations. Rather, section

107(d)(6) merely governs the timing of

PM[2.5] designations, which are made

under the authority contained in

section 107(d)(1)--a provision that

the statute expressly exempts from

notice-and-comment requirements. See §

7407(d)(2)(B).

B. Holmstead Memo

Petitioners' argument that the

Holmstead Memo had to undergo notice

and comment stems, in part, from their

erroneous belief that the final

designations were subject to notice

and comment. Our determination above,

that the statute exempts the

nonattainment designations from

notice-and-comment procedures,

suggests that the Holmstead

Memo--which was simply the first step

in the promulgation of

designations--is also exempt.

Petitioners' further argument, that

the Holmstead Memo is a legislative

rule that must undergo notice and

comment independent of the final rule

to which it relates, is also

unavailing. For support, petitioners

point to General Electric Co. v. EPA,

290 F.3d 377, 351 U.S. App. D.C. 291

(D.C. Cir. 2002), in which we

explained that whether an agency

action is the type of action that must

undergo notice and comment depends on

"whether the agency action binds

private parties or the agency itself

with the 'force of law,'" id. at

382--that is, whether "a document

expresses a change in substantive law

or policy (that is not an

interpretation) which the agency

intends to make binding, or

administers with binding effect," id.

at 382-83 (quoting Robert A. Anthony,

Interpretive Rules, Policy Statements,

Guidances, Manuals, and the

Like--Should Federal Agencies Use Them

to Bind the Public?, 41 DUKE L.J.

1311, 1355 (1992)). General Electric

further explained that "an agency

pronouncement will be considered

binding as a practical matter if it

either appears on its face to be

binding . . . or is applied by the

agency in a way that indicates it is

binding." Id. at 383 (internal

citation omitted).

In response, EPA argues that the

Holmstead Memo is merely a policy

statement, not a legislative rule,

because it does not create or modify

legally binding rights or obligations.

As EPA correctly notes, the APA

expressly exempts policy statements

from notice-and-comment requirements.

See 5 U.S.C. § 553(b)(A) (specifying

that, except when required by statute,

the section 553 requirements for

notice and comment do not apply "to

interpretative rules, general

statements of policy, or rules of

agency organization, procedure, or

practice").

EPA has the better of this dispute.

First, the Holmstead Memo is not

binding on its face. It specifies that

it merely "provides guidance to State

and local air pollution control

agencies . . . on the process for

designating areas for the purpose of

implementing the fine particle

national ambient air quality

standards." Holmstead Memo at 1. It

then explicitly states that it is "not

binding" on the states or EPA and

notes that it provides only EPA's

"current views" on the designation

process, [*34] suggesting that

those views are open to revision. Id.

at 2. Unlike the agency documents at

issue in General Electric and CropLife

America v. EPA, 329 F.3d 876, 356 U.S.

App. D.C. 192 (D.C. Cir. 2003), which

petitioners also cite, the Holmstead

Memo does not impose binding duties on

states or the agency. It merely

clarifies the states' existing duties

under the Clean Air Act and explains

the process EPA suggests for states to

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
follow in providing their initial

designations. As we explained above,

see supra at 7-8, the Memo establishes

a rebuttable C/MSA presumption and

outlines nine factors for EPA to

consider in its final designations,

see Holmstead Memo Guidance at 5-7.

Petitioners point to language in

the Holmstead Memo that they view as

evidence of its binding character

vis-a-vis the states: "A demonstration

supporting the designation of

boundaries that are less than the full

metropolitan area must show both that

violations are not occurring in the

excluded portions of the metropolitan

area and that the excluded portions

are not source areas that contribute

to the observed violations." Id. at 7.

But this language does not create a

new burden on the states; it merely

reiterates the statutory requirements.

See § 7407(d)(1)(A)(i) (requiring

Governors to designate as

nonattainment "any area that does not

meet (or that contributes to ambient

air quality in a nearby area that does

not meet)" the NAAQS).

Nor does the Holmstead Memo bind

EPA. The Memo announces the C/MSA

presumption as a rebuttable

presumption, which preserves the

agency's discretion to deviate from

the boundaries of a C/MSA in the final

designations. See Panhandle Producers

& Royalty Owners Ass'n v. Econ.

Regulatory Admin., 822 F.2d 1105,

1110, 262 U.S. App. D.C. 43 (D.C. Cir.

1987) ("'An agency pronouncement is

not deemed a binding regulation merely

because it may have some substantive

impact, as long as it leave[s] the

administrator free to exercise his

informed discretion.' . . .

Presumptions, so long as rebuttable,

leave such freedom." (quoting Brock v.

Cathedral Bluffs Shale Oil Co., 796

F.2d 533, 537, 254 U.S. App. D.C. 242

(D.C. Cir. 1986) (internal quotation

marks omitted))).

Further, EPA has not applied the

Holmstead Memo in a binding manner.

Petitioners again cite General

Electric for the proposition that an

agency document will be considered

binding if "the affected private

parties are reasonably led to believe

that failure to conform will bring

adverse consequences." Gen. Elec., 290

F.3d at 383 (quoting Anthony, supra,

at 1328). The Memo "encouraged" states

to address all nine factors EPA

identified, but did not require them

to do so. Holmstead Memo Guidance at

7. Some states did not address all or

even any of the factors. See, e.g.,

Letter from Robert G. Burnley, Dep't

of Envtl. Quality, Commonwealth of

Virginia, to Donald S. Welsh, U.S. EPA

Region III (Feb. 13, 2004)

(recommending that all of Virginia be

designated attainment without

addressing any of the nine factors);

Letter from Stephanie R. Timmermeyer,

West Virginia Dep't of Envtl. Prot.,

to Donald S. Welsh, U.S. EPA Region

III (Feb. 13, 2004) (recommending

PM[2.5] nonattainment areas to match

the existing ozone nonattainment areas

without addressing any of EPA's other

eight factors). EPA considered such

submissions and did not impose

"adverse consequences,"

notwithstanding the states' failure to

address the factors listed in the

Holmstead Memo. Compare State of West

Virginia PM[2.5]

Designations--Preliminary

Recommendations, with PM[2.5]

Designations Rule, 70 Fed. Reg. at

1014-15 (showing that EPA designated

as attainment an area that West

Virginia had proposed be designated

nonattainment, despite the fact that

West Virginia [*35] did not address

eight of EPA's nine factors).

In sum, we deny petitioners'

procedural claims because EPA was not

required to submit either the final

designations rule or the Holmstead

Memo for notice and comment.

IV.

Petitioners next claim that EPA

violated section 107(d) of the Clean

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
Air Act by applying the C/MSA

presumption and nine-factor test to

identify areas that contribute to

nearby PM[2.5] violations. As we

explained above, we review EPA's

interpretation of the Clean Air Act

under Chevron, asking whether Congress

has "directly spoken to the precise

question at issue," 467 U. S. at 842,

and if so, whether it has

unambiguously foreclosed the agency's

statutory interpretation, e.g., Sierra

Club v. EPA, 536 F.3d 673, 677, 383

U.S. App. D.C. 109 (D.C. Cir. 2008).

But if the statute is either silent or

ambiguous on the specific question at

issue, we defer to EPA's statutory

interpretation so long as it is

reasonable. Id.

At the outset we observe that

section 107(d) is replete with the

kinds of words that suggest a

congressional intent to leave

unanswered questions to an agency's

discretion and expertise, see Nat'l

Cable & Telecomms. Ass'n v. Brand X

Internet Servs., 545 U.S. 967, 980,

125 S. Ct. 2688, 162 L. Ed. 2d 820

(2005) (statutory ambiguity is

delegation to the agency "to fill the

statutory gap in reasonable fashion").

Section 107(d) requires EPA to

designate an area as nonattainment if

it "contributes to ambient air quality

in a nearby area" that exceeds the

relevant standard, § 7407(d)(1)(A)(i),

yet the statute defines neither

"contributes" nor "nearby"--words that

we have expressly found ambiguous as

used in other sections of the Act. See

Envtl. Def. Fund v. EPA, 82 F.3d 451,

459, 317 U.S. App. D.C. 207 (D.C. Cir.

1996) ("contributes to" ambiguous in

another section of the Clean Air Act);

Sierra Club v. EPA, 719 F.2d 436,

443-44, 231 U.S. App. D.C. 192 (D.C.

Cir. 1983) (same, as to "nearby"). It

authorizes EPA to revise

state-submitted designations whenever

it "deems" such modifications

"necessary," yet it says nothing of

what precisely will render a

modification "necessary." §

7407(d)(1)(B)(ii). And section 107(d)

requires states to submit PM[2.5]

designations "based on air quality

monitoring data collected in

accordance with any applicable Federal

reference methods," § 7407(d)(6)(A),

yet it fails to define "based on" and

"[t]here is no question that the

phrase 'based on' is ambiguous,"

Sierra Club v. EPA, 356 F.3d 296,

305-06, 360 U.S. App. D.C. 1 (D.C.

Cir. 2004); accord. Nuclear Energy

Inst., Inc. v. EPA, 373 F.3d 1251,

1269, 362 U.S. App. D.C. 204 (D.C.

Cir. 2004). "[A]mbiguities in statutes

within an agency's jurisdiction to

administer are delegations of

authority to the agency to fill the

statutory gap in reasonable fashion."

Brand X, 545 U.S. at 980. Because it

conveys no clear-cut approach for

determining whether an area

contributes to a nearby PM[2.5]

violation, section 107(d)'s text is

consistent with such a delegation.

To be sure, a statute may foreclose

an agency's preferred interpretation

despite such textual ambiguities if

its structure, legislative history, or

purpose makes clear what its text

leaves opaque. Cf. Ariz. Pub. Serv.

Co. v. EPA, 211 F.3d 1280, 1287, 341

U.S. App. D.C. 222 (D.C. Cir. 2000)

(court must "exhaust[] traditional

tools of statutory construction" at

Chevron step one). Notwithstanding

petitioners' torrent of arguments to

the contrary, this is not such a

case--indeed, it isn't even close.

We start with the argument that

petitioners judge to be their best.

See Oral Arg. at 1:16-3:00. Pointing

to section 107(d)(4), petitioners

insist that the [*36] statute's

express mandate that EPA apply the

C/MSA presumption in other contexts

conclusively proves that Congress

intended to preclude its use here.

Enacted as part of the 1990 Amendments

to the Clean Air Act, section

107(d)(4) "revise[s] . . . by

operation of law" the boundaries of

certain urban ozone or carbon monoxide

nonattainment areas "to include the

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
entire metropolitan statistical or

consolidated metropolitan statistical

area," unless EPA determined that some

portions "do not contribute

significantly to the violation of the

national ambient air quality

standard." § 7407(d)(4)(A)(iv)-(v). In

contrast, section 107(d)(6) says

nothing about the C/MSA presumption.

Instead it provides that the PM[2.5]

area designations must be "based on

air quality monitoring data" and

promulgated in accordance with section

107(d)(1)'s general provisions for

area designations. § 7407(d)(6)(A).

Citing the familiar canon of statutory

interpretation that "[w]here Congress

includes particular language in one

section of a statute but omits it from

another section of the same Act, it is

generally presumed that Congress acts

intentionally and purposely in the

disparate inclusion or exclusion,"

Russello v. United States, 464 U.S.

16, 23, 104 S. Ct. 296, 78 L. Ed. 2d

17 (1983) (internal quotation marks

and brackets omitted), petitioners

insist that the statute's exclusive

inclusion of the C/MSA presumption for

the ozone and carbon monoxide

designations demonstrates Congress'

unambiguous intent to preclude EPA

from adopting the presumption here.

Although petitioners are correct

that we construe statutes to give

meaning to the disparate inclusion of

particular language, that principle

hardly compels the interpretation they

favor. When interpreting statutes that

govern agency action, we have

consistently recognized that a

congressional mandate in one section

and silence in another often "suggests

not a prohibition but simply a

decision not to mandate any solution

in the second context, i.e., to leave

the question to agency discretion."

Cheney R. Co. v. ICC, 902 F.2d 66, 69,

284 U.S. App. D.C. 101 (D.C. Cir.

1990); see also Clinchfield Coal Co.

v. Fed. Mine Safety & Health Review

Comm'n, 895 F.2d 773, 779, 282 U.S.

App. D.C. 368 (D.C. Cir. 1990)

("[W]here an agency is empowered to

administer the statute, Congress may

have meant that in the second context

the choice should be up to the

agency."). Silence, in other words,

may signal permission rather than

proscription. For that reason, that

Congress spoke in one place but

remained silent in another, as it did

here, "rarely if ever" suffices for

the "direct answer" that Chevron step

one requires. Cheney, 902 F.2d at 69

(internal quotation marks omitted);

see also Am. Forest & Paper Ass'n v.

FERC, 550 F.3d 1179, 1181, 384 U.S.

App. D.C. 73 (D.C. Cir. 2008)

(statute's discrepant inclusion of the

modifier "competitive" to describe

"markets" renders statutory provision

lacking the modifier ambiguous).

Undaunted, petitioners insist that

the silence here is unambiguously

prohibitive. They point out that

Congress not only refused to treat

PM[2.5] like ozone and carbon monoxide

but chose an altogether different

scheme in subsection (d)(6)--one

"based on air quality monitoring

data," § 7407(d)(6)(A), rather than

OMB-drawn metropolitan boundaries and

a multi-factor test. As indicated

above, however, Congress's mere choice

of different standards in subsections

(d)(4) and (d)(6) tells us nothing

about whether Congress wanted to

mandate different approaches or to

permit them. Thus, for this argument

to succeed, subsection (d)(6) must

itself preclude EPA from adopting a

test for PM[2.5] like the one that

Congress mandated for ozone and carbon

monoxide in subsection (d)(4). But

nothing in subsection (d)(6) even

hints at [*37] such a prohibition.

Subsection (d)(6)(A) requires states

to submit PM[2.5] designations "based

on air quality monitoring data

collected in accordance with any

applicable Federal Reference methods";

subsection (d)(6)(B) in turn requires

EPA to promulgate those designations

in accordance with subsection (d)(1)'s

general provisions. For the sake of

argument, we shall assume that

subsection (d)(6)'s "based on"

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
language unambiguously applies to EPA

even though it appears only in the

particular provision governing states.

We shall also assume that the language

substantively constrains EPA's

discretion in determining

nonattainment boundaries. But even

given these assumptions, binding

precedent, the statute's purpose, and

basic common sense foreclose

petitioners' argument that section

107(d)(6) itself precludes EPA from

adopting the C/MSA presumption and

nine-factor test.

First, as noted above, we have

repeatedly held that the words "based

on" are unquestionably ambiguous: they

neither compel the agency to rest its

decisions "solely on" the specified

factor nor indicate the extent to

which the agency may rely on

additional factors. Sierra Club, 356

F.3d at 305-06; accord. Nuclear Energy

Inst., 373 F.3d at 1269. Instead, they

simply constrain the agency from

"abandon[ing]" or "supplant[ing]" the

specified factor altogether. Sierra

Club, 356 F.3d at 306. We need ask

only whether EPA's PM[2.5]

designations "can still reasonably be

described as 'based on'" air quality

monitoring data, id., and we have no

doubt that the contribution

designations meet this modest

standard. If nothing else, the

contribution designations are "based

on" the air quality monitoring data

that demonstrate a nearby violation of

the NAAQS. Even were this

insufficient, EPA's use of air quality

monitoring data as part of its

nine-factor analysis--for instance,

its use of urban excess and weighted

emissions scores based on speciation

data--would surely suffice.

Second, because subsection d(1)

directs EPA to designate some areas as

nonattainment despite monitoring data

that provides no basis, on its own, to

do so, see § 7407(d)(1)(A)(i), we

think it quite clear that the statute

contemplates reliance on factors other

than monitoring data to determine

contribution. How could EPA possibly

fulfill its statutory duty to

determine, for instance, whether

emissions in Indiana contribute to

monitored violations in Chicago

without considering wind and emissions

data from Indiana? Obviously it

couldn't. That the statute fails to

set forth the additional criteria for

EPA to consider in evaluating

contribution hardly forecloses EPA

from developing such criteria in order

to accomplish Congress's objectives.

See e.g., Entergy Corp. v.

Riverkeeper, Inc., 129 S. Ct. 1498,

1508, 173 L. Ed. 2d 369 (2009).

Indeed, when a statute is "silent . .

. with respect to all potentially

relevant factors, it is eminently

reasonable to conclude that [the]

silence is meant to convey nothing

more than a refusal to tie the

agency's hands." Id. (emphasis added).

Still undaunted, petitioners advert

to section 107(d)(3)--which permits

EPA to require a revision to an area

designation "on the basis of air

quality data, planning and control

considerations, or any other air

quality-related considerations the

Administrator deems appropriate," §

7407(d)(3)--as evidence that Congress

"knew how to authorize a flexible,

'multi-factor' approach to attainment

decisions when it so intended."

Counties' Opening Br. 20. But the

Supreme Court rejected just this kind

of argument in Entergy Corp. v.

Riverkeeper, Inc., which asked whether

EPA may engage in cost-benefit

analysis under section 316(b) of the

Clean [*38] Water Act given that it

says nothing of cost-benefit analysis

while other sections expressly

authorize it. 129 S. Ct. at 1508.

Pointing out that section 316(b) "is

silent not only with respect to

cost-benefit analysis but with respect

to all potentially relevant factors,"

the Court rejected the claim that the

silence reflected a prohibition, for

if it did, "then the EPA could not

consider any factors in implementing

[section 316(b)]--an obvious logical

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
impossibility." Id. Here we face just

this kind of overwhelming statutory

silence. Although logic dictates that

EPA must evaluate some factors in

addition to monitoring data to

determine contribution, the statute

says nothing about which factors it

should consider. We thus have no

difficulty rejecting the claim that

the statute unambiguously forecloses

EPA from adopting the C/MSA

presumption or considering its nine

factors in applying it.

The legislative history petitioners

cite fails to rehabilitate their claim

that section 107(d)(6) unambiguously

requires EPA to base all PM[2.5]

designations--including nonattainment

designations for contribution--"on air

quality monitoring data" alone.

Although petitioners are correct that

in the Transportation Equity Act for

the 21st Century, Congress provided

for the deployment of a PM[2.5]

monitoring network to produce adequate

monitoring data for these

designations, that does nothing to

dispel the ambiguity over what

criteria EPA should rely on to assess

contribution. Indeed, the particular

provision of TEA-21 that petitioners

emphasize actually reinforces that

ambiguity rather than resolves it. See

TEA-21 § 6102(c)(1) ("Only data from

the monitoring network . . . shall be

considered for such designations.

Nothing in the previous sentence shall

be construed as affecting . . . the

Administrator's authority to

promulgate the designation of an area

as nonattainment, under section

107(d)(1) of the Clean Air Act, based

on its contribution to ambient air

quality in a nearby nonattainment

area.").

In sum, we conclude that neither

section 107(d)'s requirement that

PM[2.5] designations be "based on air

quality monitoring data" nor its

mandate that EPA apply the C/MSA

presumption and a multi-factor test

for pollutants other than PM[2.5]

unambiguously reveals Congress's

intent to prevent EPA from using the

presumption and the nine-factor test

to determine contribution here. Our

rejection of petitioners' purportedly

strongest argument is a fair harbinger

of the fate of their remaining

statutory complaints.

To begin with, petitioners waived

two of their statutory arguments by

failing to raise them in their opening

briefs. See New York v. EPA, 413 F.3d

3, 20, 367 U.S. App. D.C. 3 (D.C. Cir.

2005) (petitioners waive those

arguments that they fail to raise in

their opening briefs). Specifically,

not until their reply briefs did they

present a statutory challenge to EPA's

interpretation that a "nearby" area

under section 107(d)(1)(A) may include

noncontiguous areas, or to its

conclusion that an area's future

reductions in emissions qualifies as a

relevant factor for assessing

contribution. This leaves just two

general challenges: petitioners' claim

that the C/MSA presumption and the

nine-factor test run afoul of the

statutory term "contribute"; and their

claim that the presumption

impermissibly encroaches on states'

statutory prerogative to have

first-say on area designations within

their borders.

As to the textual claim,

petitioners insist that the verb

"contribute" necessarily connotes a

significant causal relationship,

meaning that EPA may not designate a

county as contributing to

nonattainment if "corrective measures

in [the county] will do nothing to

address the problem or help achieve

compliance in the nonattainment [*39]

area." Counties' Opening Br. 25. We

reject both the major and the minor

premise. Although petitioners cite one

dictionary that supports the claim

that the adverb "significantly" is

implicit in the verb "contribute," EPA

cites other dictionaries that define

"contribute" without reference to any

threshold level of significance. This

alone suggests an ambiguity that

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
fatally undermines petitioners'

Chevron step one argument. See

Cellular Telecomms. & Internet Ass'n

v. FCC, 330 F.3d 502, 509, 356 U.S.

App. D.C. 238 (D.C. Cir. 2003)

("[D]ueling over dictionary

definitions is pointless, for it fails

to produce any plain meaning of the

disputed word."). But even were we to

think that "contribute" unambiguously

means "significantly contribute," we

still disagree that "significantly

contribute" unambiguously means

"strictly cause." Cf. Michigan v. EPA,

213 F.3d 663, 667-68, 341 U.S. App.

D.C. 306 (D.C. Cir. 2000)

("significant" is ambiguous). Given

that the statute uses the word

"contribute" and that a contribution

may simply exacerbate a problem rather

than cause it, we see no reason why

the statute precludes EPA from

determining that a county's addition

of PM[2.5] into the atmosphere is

significant even though a nearby

county's nonattainment problem would

still persist in its absence. In fact,

a contrary interpretation of

"contribute" would effectively

preclude a nonattainment designation

for any attaining county when the

cause of the violation is

metropolitan-wide. We may not

interpret "contribute" in a way that

does such violence to section 107(d)'s

very purpose.

We also reject petitioners'

argument that EPA violated the statute

by failing to articulate a quantified

amount of contribution that would

trigger a nonattainment designation.

Petitioners apparently prefer a

bright-line, "objective" test of

contribution, see, e.g., Counties'

Opening Br. 28, but it is the statute,

not petitioners' preferences, that

constrains EPA's discretion. And

nothing in the statute compels EPA to

quantify a uniform amount of

contribution below which counties will

automatically escape nonattainment

designations or to quantify similar

thresholds for the nine factors EPA

evaluated in making those

determinations. Section 107(d) is

ambiguous as to how EPA should measure

contribution and what degree of

contribution is sufficient to deem an

area nonattainment, as even

petitioners seem to concede, see

Counties' Reply Br. 13 ("EPA was

supposed to be defining and deciding

'contributes.'"). Thus, reasonably

exercising the discretion that

Congress delegated to it, EPA

interpreted "contribute" to mean

"sufficiently contribute," and then

applied the C/MSA presumption and

nine-factor test precisely to identify

those areas that meet that definition.

Petitioners offer no plausible reason

to think that the statute forecloses

this approach.

Nor do we agree with petitioners

that EPA's failure to quantify its

analysis somehow rendered its

interpretation of "contribute"

arbitrary and capricious and therefore

unreasonable under Chevron step two.

Cf. Northpoint Tech., Ltd. v. FCC, 412

F.3d 145, 151, 366 U.S. App. D.C. 363

(D.C. Cir. 2005) (statutory

interpretation that is arbitrary and

capricious is unreasonable under

Chevron step two). An agency is free

to adopt a

totality-of-the-circumstances test to

implement a statute that confers broad

discretionary authority, even if that

test lacks a definite "threshold" or

"clear line of demarcation to define

an open-ended term." PDK Labs., Inc.

v. DEA, 438 F.3d 1184, 1195, 370 U.S.

App. D.C. 47 (D.C. Cir. 2006)

(internal quotation marks omitted). To

be reasonable, such an

"all-things-considered standard" must

simply define and explain the criteria

the agency is applying, id. at 1194,

something the Holmstead Memo and

certainly the Technical Support

Document did in spades. Of course, EPA

may have applied [*40] its

nine-factor test inconsistently,

resulting in similar counties being

treated dissimilarly--a question we

address in Part V. EPA may also have

applied it so erroneously in a

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
particular case that it could not have

reasonably concluded that a county was

contributing to nearby violations--an

issue we consider in Part VI. But

EPA's use of a flexible multi-factor

analysis is not in and of itself

unreasonable just because it lacks

quantitative standards. See id. at

1194-95.

We are equally unimpressed by

petitioners' last general argument:

that the C/MSA presumption unlawfully

"deprived states of the deference to

which their designations were

entitled" under section 107(d).

States' Opening Br. 1. To the extent

petitioners are claiming that EPA owes

the states a measure of procedural

deference under section 107(d), we

agree that EPA must wait its turn

before it makes any individual county

designations. Indeed, in contrast to

its many ambiguities, section

107(d)(1) clearly provides that states

submit their "initial designations"

first, § 7407(d)(1)(A), and only then

does EPA promulgate or modify the

designations as it "deems necessary,"

§ 7407(d)(1)(B)(ii). Not only is that

precisely what happened here, but

nothing in section 107(d)(1) prevents

EPA from developing general principles

to govern its exercise of discretion

when the time comes, or from

announcing those general principles

before the states submit their initial

designations. To the extent

petitioners think that EPA owes the

states a measure of substantive

deference under section 107(d)(1)--a

claim that seems implicit in their

objection that the C/MSA presumption

somehow alters states' "burden" in the

designation process, see States'

Opening Br. 24--we disagree. Though

EPA may, of course, go along with

states' initial designations, it has

no obligation to give any quantum of

deference to a designation that it

"deems necessary" to change. See,

e.g., Pa. Dep't of Envtl. Prot. v.

EPA, 429 F.3d 1125, 1129, 368 U.S.

App. D.C. 324 (D.C. Cir. 2005)

(recognizing that section 107(d) gives

"deference" to states' initial

designations provided EPA deems no

modification necessary). In short, EPA

had authority to apply the C/MSA

presumption at the time it rejected

the states' submissions. We see no

reason why section 107(d)(1) would

force EPA to bite its tongue until

then.

Having rejected petitioners'

arguments that section 107(d)

unambiguously precludes EPA from

adopting the C/MSA presumption and

nine-factor test, we can easily

conclude that EPA reasonably

interpreted the statute as permitting

it to do so. Even if we read section

107(d) favorably to petitioners, it

requires only that EPA designate,

based on air quality monitoring data,

nonattainment areas that either

violate or contribute to violations of

the PM[2.5] NAAQS. Acting evidence

that urban PM[2.5] violations usually

stem from metropolitan-wide

activities, EPA adopted a presumption

that designates all metropolitan areas

as nonattainment when at least one

metropolitan area registers a PM[2.5]

violation, as well as a specifically

defined multi-factor analysis to

assess when that presumption fails to

reflect the realities of a given

metropolitan area. Petitioners give us

every reason to think they would

prefer another system of

analysis-specifically, one that would

allow them to escape certain

nonattainment designations-but they

give us no reason to think the system

EPA selected is unreasonable.

V.

Petitioners next argue that the

Designations Rule is arbitrary and

capricious because it is riddled with

methodological flaws and

inconsistencies. They challenge the

Rule in four regards: EPA's

designation [*41] of noncontiguous

townships as nonattainment, the

agency's refusal to account for some

potential emissions reductions, the

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
so-called carbon error in some

weighted emissions scores, and the way

EPA applied the nine-factor test.

"[W]e apply the same standard of

review under the Clean Air Act as we

do under the Administrative Procedure

Act (APA), 5 U.S.C. § 706(2)(A),"

Allied Local & Reg'l Mfrs. Caucus v.

EPA, 215 F.3d 61, 68, 342 U.S. App.

D.C. 61 (D.C. Cir. 2000), and will set

aside the Designations Rule only if it

is "arbitrary, capricious, an abuse of

discretion, or otherwise not in

accordance with law," § 7607(d)(9)(A).

We must affirm the Rule if the record

shows EPA considered all relevant

factors and articulated a "rational

connection between the facts found and

the choice made." Burlington Truck

Lines v. United States, 371 U.S. 156,

168, 83 S. Ct. 239, 9 L. Ed. 2d 207

(1962). Of particular note in this

challenge, we give an "extreme degree

of deference to [EPA] when it is

evaluating scientific data within its

technical expertise," City of Waukesha

v. EPA, 320 F.3d 228, 247, 355 U.S.

App. D.C. 100 (D.C. Cir. 2003)

(internal quotation marks omitted).

Such deference is especially

appropriate in our review of EPA's

administration of the complicated

provisions of the Clean Air Act. See

Nat'l Ass'n of Clean Air Agencies v.

EPA, 489 F.3d 1221, 1229, 376 U.S.

App. D.C. 385 (D.C. Cir. 2007).

In basing its designation decisions

on a rigorous analysis of each

county's particular attributes, EPA

satisfied the requirements of reasoned

decisionmaking. Given our highly

deferential standard of review, these

four challenges provide no basis to

question EPA's general analysis or to

upset the entire Designations Rule.

A. Designation of Noncontiguous

Townships

As we have described above, EPA's

designation analysis starts with two

presumptions. See supra at 12-13.

First, "if a PM[2.5] monitor [is]

violating" the NAAQS, "at a minimum

[EPA will] designate the entire county

where that monitor is located as

nonattainment" because the "county

boundary" is "the basic jurisdictional

boundary for determining the extent of

the area reflected by the PM[2.5]

monitor." PM[2.5] Designations Rule,

70 Fed. Reg. at 946-47. Second, all

counties within the C/MSA contribute

to that violation. See id. at 947;

Holmstead Memo Guidance at 4. When

these presumptions operate in tandem,

a violating monitor within a C/MSA

will result in a single contiguous

block of nonattainment counties that

includes both the county with the

violating monitor and the other C/MSA

counties that are deemed to contribute

to that violation. Likewise, when EPA

includes out-of-C/MSA counties in a

nonattainment block, those counties

typically adjoin violating counties.

But EPA also invites states to

recommend smaller PM[2.5] designation

areas on a "case-by-case basis" if

they "provide an adequate

justification demonstrating that a

smaller area would include the full

area that is violating the standards

and all nearby source areas that

contribute to the violation."

Holmstead Memo Guidance at 6. Some

states took up EPA's offer and asked

that a township rather than a county

be designated as nonattainment when a

power plant in the township was the

overwhelming source of the county's

contribution to a nearby PM[2.5]

violation. See PM[2.5] Designations

Rule, 70 Fed. Reg. at 947; Technical

Support Document § 6.5.4.4

(Discussion).

To borrow petitioners' imagery,

this approach created an island of

nonattainment--the

township--surrounded by a sea of

attainment throughout the remainder of

the county. Industry petitioners argue

that creating such islands of

nonattainment arbitrarily deviates

from the presumption [*42] that

designations should be made at the

county level. Because emissions from a

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
power plant in a township do not skip

over all other parts of the

surrounding county and come to rest in

a nearby area with a violating

monitor, petitioners argue that

violating areas designated

nonattainment should be contiguous to

those areas contributing to the

violation.

We find no fault in EPA's

conclusion that it would be

unreasonable to designate as

nonattainment those areas that do not,

in fact, contribute to violations. EPA

designated as nonattainment a township

with an emitting source--rather than

the entire county--because "it would

be inappropriate to include other

portions of a county, merely because

those portions lay between the large

stationary source and the remainder of

the designated nonattainment area."

PM[2.5] Designations Rule, 70 Fed.

Reg. at 947. Although contiguity of

nonattainment areas may follow from

the operation of the Rule's twin

presumptions, the designations process

does not mandate that result when the

scientific data show that a source

contributing to a violation is not in

an area contiguous to the county with

the violating monitor. According to

the Technical Support Document, EPA

designated townships rather than

entire counties as nonattainment only

when a power plant in the township was

responsible for the vast majority of

the county's PM[2.5] emissions. For

example, the Conesville Plant in

Franklin Township emitted 99% of the

SO[2], 90% of the NO[x], 78% of the

carbon, and 87% of the crustal

emissions for all of Coshocton County.

See Technical Support Document §

6.5.4.4 (Factor 1). By designating

only Franklin Township as

nonattainment, EPA accounted for the

lion's share of Coshocton County's

emissions that "are contributing to

the violation in the Columbus

Metropolitan Area," id. (Discussion).

EPA presented comparable statistics

for the townships designated

nonattainment in Adams and Gallia

Counties. Id. § 6.5.4.6 (Factor 1)

(providing a similar rationale for

designating Monroe and Sprigg

Townships in Adams County and Cheshire

Township in Gallia County). EPA

reasonably concluded there was no need

to designate as nonattainment any

other part of these counties.

Industry petitioners also argue

that EPA failed to use monitoring or

modeling data in designating townships

as nonattainment. But petitioners fail

to identify any township designations

lacking such support. And although we

have no obligation to comb through the

voluminous record in this case to

determine the merits of an argument

for which petitioners offer no

support, see FED. R. APP. P.

28(a)(9)(A) (requiring briefs to

contain "citations to the authorities

and parts of the record on which the

appellant relies"), we note at least

one instance in which we easily found

that the record contradicts their

assertion. EPA used air quality

modeling to determine that the power

plant in Franklin Township was

responsible for the vast majority of

Coshocton County's contribution to

PM[2.5] violations in the Columbus

Metropolitan Area. See Memorandum from

Brian Timin & Richard Damberg, EPA

Office of Air Quality Planning &

Standards, Air Quality Modeling To

Assess Power Plant Impacts 2 (Jan. 20,

2006); Technical Support Document §

6.5.4.4 (Discussion, Factor 1, Factor

2); see also PM[2.5] Designations

Rule, 70 Fed. Reg. at 947 (explaining

that EPA uses speciation data from

monitors to determine which sources

contribute to violations).

Finally, industry petitioners

contend that because EPA designated

only contiguous areas as nonattainment

for excessive levels of ozone, it

acted arbitrarily in not doing so for

PM[2.5]. But ozone was the subject of

a different designations process

[*43] and a separate rulemaking, and

nothing compels EPA to use the same

approach for PM[2.5]. Petitioners

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
emphasize that PM[2.5] and ozone are

both pollutants that can travel long

distances. That similarity alone,

however, is not enough to force EPA to

treat the two pollutants as if they

pose the same threat to public health

and welfare. When EPA set forth the

criteria it would use during the

PM[2.5] designations process, it

explained that "unlike ozone," PM[2.5]

"can arise on a very localized basis.

For example, violations can be caused

by the emissions from a single major

source or set of sources." Holmstead

Memo Guidance at 6. Given this

critical difference, EPA was well

within its discretion to consider

state recommendations for smaller

PM[2.5] designations on a

"case-by-case basis," id.

B. Future Reductions in Emissions

When it is evident that federally

enforceable pollution controls will

yield significant near-term reductions

in emissions, EPA accounts for those

forecasted reductions in estimating an

area's emissions levels for the

purpose of evaluating contribution.

See Letter from Stephen L. Johnson,

Adm'r, EPA, to David M. Flannery,

Counsel For Midwest Ozone Group et

al., Attach. at 13 (Aug. 16, 2007)

("Johnson Attach."). Industry

petitioners argue that EPA

overestimated emissions levels and

thus made mistaken designations by

failing to account for future

reductions from two federal programs:

the Clean Air Interstate Rule (CAIR)

and the NO[x] State Implementation

Plan (also known as the "NO[x] SIP

Call"). See generally North Carolina

v. EPA, 531 F.3d 896, 902-03, 382 U.S.

App. D.C. 167 (D.C. Cir.) (describing

programs), modified, 550 F.3d 1176,

384 U.S. App. D.C. 70 (D.C. Cir.

2008). We find no error in EPA's

refusal to consider estimates of lower

emissions levels that might result

from these two programs.

EPA promulgated CAIR to reduce

SO[2] and NO[x] emissions from upwind

sources in 28 states and the District

of Columbia that contribute to

nonattainment levels for ozone and

PM[2.5] in downwind states. Id. at

903. When EPA made its PM[2.5]

designations, it reasonably decided

emissions reductions from CAIR were,

at the time, uncertain and should not

be a factor in estimating emissions

levels for the designations process.

See Johnson Attach. at 13 (explaining

that EPA would include projected

emissions reductions only for

federally enforceable agreements that

were "in place by the time that EPA

was required to promulgate the

designations in December 2004"). As

discussed above, designations for

C/MSAs, counties, and townships turn

in part on contributions from

identifiable sources. When EPA made

its designation decisions in December

2004, there was no assurance that a

state's compliance with CAIR, which

did not become effective until March

2005, would result in reduced PM[2.5]

emissions for specific sources.

Indeed, CAIR did not require states to

submit to EPA their recommendations as

to which power plants would reduce

SO[2] and NO[x] emissions and how they

would do so until September

2006--nearly two years after the

agency had designated areas under the

PM[2.5] NAAQS. See Rule To Reduce

Interstate Transport of Fine

Particulate Matter and Ozone (Clean

Air Interstate Rule), 70 Fed. Reg.

25,162, 25,162 (May 12, 2005); Rule To

Reduce Interstate Transport of Fine

Particulate Matter and Ozone (Clean

Air Interstate Rule): Reconsideration,

71 Fed. Reg. 25,304, 25,305 (Apr. 28,

2006) ("Each State covered by CAIR may

independently determine which emission

sources to control, and which control

measures to adopt."). Even EPA's

provisional compliance

regime--designed to start reductions

in emissions levels before states were

required to file their plans--did not

take [*44] effect until more than a

year after the agency had completed

designating areas. See Rulemaking on

Section 126 Petition from North

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
Carolina To Reduce Interstate

Transport of Fine Particulate Matter

and Ozone, 71 Fed. Reg. 25,328, 25,328

(Apr. 28, 2006); see also North

Carolina, 531 F.3d at 903 (describing

program). It was therefore reasonable

for EPA to disregard as too

speculative any claimed emissions

reductions that might come from CAIR

when it promulgated the PM[2.5]

designations in December 2004. See

Johnson Attach. at 8 n.11.

It was likewise reasonable for EPA

to disregard forecasted reductions

from the NO[x] SIP Call. Created to

reduce ozone pollution, this program

requires 22 upwind states and the

District of Columbia to decrease NO[x]

emissions, a significant precursor to

PM[2.5], but it has nothing to do with

reducing SO[2] , another significant

PM[2.5] precursor. See Finding of

Significant Contribution and

Rulemaking for Certain States in the

Ozone Transport Assessment Group

Region for Purposes of Reducing

Regional Transport of Ozone, 63 Fed.

Reg. 57,356, 57,356 (Oct. 27, 1998).

The power plants in question are often

among the largest sources of SO[2] in

their respective areas. See Johnson

Attach. at 8. EPA concluded that

reducing NO[x] but not SO[2] was a

step in the right direction for

reducing PM[2.5], but it fell short of

what EPA required to consider

forecasted reductions in its

designations. See id. at 14. Lacking

evidence of significant near-term

reductions in SO[2], EPA reasonably

decided not to alter nonattainment

designations based only on forecasted

reductions in NO[x]. See, e.g.,

Technical Support Document § 6.4.4.1

(Factor 9) (showing EPA designated as

attainment Stokes County, North

Carolina, because a power plant there

installed controls certain to reduce

significantly both NO[x] and SO[2]).

C. Carbon Error

In making nonattainment

designations, EPA relied upon a

mistaken estimate of carbon emissions

by power plants that burn bituminous

coal. Industry petitioners seize on

this error as evidence that the

Designations Rule is arbitrary and

capricious. We disagree. EPA used the

best available information, and the

mistaken estimate of carbon had no

effect on the reasonableness of the

challenged designations.

Among the analytical tools EPA uses

to make designation determinations is

a county's weighted emissions score,

which allows the agency to compare

SO[2], NO[x], carbon, and crustal

emissions across counties within a

C/MSA. See PM[2.5] Designations Rule,

70 Fed. Reg. at 947. This score is not

based on measurements of actual

emissions by a particular source.

Instead, EPA uses emissions estimates

from the National Emissions Inventory

(NEI) to calculate total PM[2.5]

emissions, as well as SO[2], NO[x],

carbon, and crustal emissions for each

county. See What Is the National

Emissions Inventory (NEI)?,

http://www.epa.gov/ttn/chief/net/neiwhat

is. html (last visited June 11, 2009).

The NEI is a database assembled by

EPA's Emission Inventory and Analysis

Group that houses estimates of the

kinds and amounts of substances

emitted by particular sources,

including point sources like power

plants and mobile sources like

automobiles. Based on these estimates,

EPA creates "speciation profiles,"

which describe the chemicals that make

up the emissions associated with a

particular type of source. See

Speciation: Emissions Modeling

Clearinghouse,

http://www.epa.gov/ttn/chief/emch/specia

tion/ (last visited June 11, 2009).

The speciation profile EPA used for

large electric generating units (EGUs)

estimated [*45] that carbon makes up

21% of their PM[2.5] emissions. As it

turns out, that estimate was wrong for

plants that burn bituminous coal.

Carbon accounts for only 2.9% of their

PM[2.5] emissions. See J.A. at

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
2848-49. EPA updated the speciation

profile for these plants in its 2006

revision of the PM[2.5] NAAQS, but

retained the old profile for plants

that burn primarily lignite coal.

Industry petitioners argue that

because the 2004 designations were

based on a flawed EGU profile that

vastly overestimated carbon emissions,

EPA's nonattainment designations for

counties with large electric power

plants that burn bituminous

coal--particularly the 23 identified

in the petition for

reconsideration--are likewise flawed.

EPA responds that its ultimate

designations did not turn on any one

estimate of a single chemical

component of PM[2.5]. Rather, the

agency relied on numerous data points,

including emissions levels and county

rankings of weighted emissions scores

within a C/MSA, that were largely

unaffected by the lower carbon

estimate. According to EPA, changes in

the speciation profile for plants that

burn bituminous coal did not

substantially lower total PM[2.5]

emissions estimates. Instead, the

proportions of pollutants emitted by

these sources changed. Specifically,

the estimate of crustal particles,

also a precursor to PM[2.5], increased

as the carbon estimate decreased. See

Johnson Attach. at 4.

We hold that EPA was not obligated

to upend the designations process when

it discovered a mistake in its

speciation profile for certain power

plants. EPA used the best information

available in making its designations,

and that is all our precedent

requires. In American Iron & Steel

Institute v. EPA, 115 F.3d 979, 1006,

325 U.S. App. D.C. 76 (D.C. Cir.

1991), the petitioners argued that

EPA's estimate for the mercury

concentration permitted in the Great

Lakes was flawed because the agency

used inaccurate data that had since

been corrected. Relying on ICC v.

Jersey City, 322 U.S. 503, 64 S. Ct.

1129, 88 L. Ed. 1420 (1944), and

Vermont Yankee Nuclear Power Corp v.

Natural Resources Defense Council, 435

U.S. 519, 98 S. Ct. 1197, 55 L. Ed. 2d

460 (1978), we held that EPA did not

act arbitrarily by using the older

data in its calculation. "The agency

was not obliged to stop the entire

process because a new piece of

evidence emerged. If this were true

then the administrative process could

never be completed. An agency does,

however, have an obligation to deal

with newly acquired evidence in some

reasonable fashion." Am. Iron, 115

F.3d at 1007.

Here, EPA dealt with newly acquired

evidence in a reasonable fashion by

explaining why it would not have

changed the challenged designations.

EPA is correct that revisions to the

speciation profile for plants that

burn bituminous coal altered only one

component of the weighted emissions

score, which itself is only one of

numerous analytical tools used to

assess the first of nine factors EPA

considers in determining contribution

to PM[2.5] violations. Speciation

profiles for power plants are by no

means the exclusive or even the

primary basis for EPA's designations,

but merely make up one part of a much

larger and multi-factored

decisionmaking process. Johnson

Attach. at 6-7.

Petitioners nonetheless contend

that the carbon error is particularly

important because carbon typically

makes up a large portion of the urban

excess and therefore weighs heavily in

these counties' weighted emissions

scores, which themselves weigh heavily

in the contribution analysis because

of the presence of large power plants.

That may be so, but EPA granted a

March 2006 request to recalculate the

weighted emissions scores using the

revised estimates and concluded

that even if [the agency]

were to reconsider the

designations, the area by

area [*46] evaluation of

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
counties with emissions

scores or activities

contributing to violations

of the NAAQS would not

result in a different

outcome. Of the counties

[petitioners] identified in

[their] petition, EPA sees

no change in the rank or

magnitude of sources

relative to other counties

in the areas that would

negate the appropriateness

of inclusion of the counties

within their respective

designated nonattainment

areas.

Letter from Stephen L. Johnson, Adm'r,

EPA, to David M. Flannery, Counsel For

Midwest Ozone Group et al. 2-3 (Aug.

16, 2007); see also J.A. at 2881-83

(showing initial and revised scores

for the 23 counties identified by

petitioners); Johnson Attach. at 10-12

(explaining why particular

designations would not have changed

with new data). Even with a change in

the estimated proportion of carbon

emitted by plants that burn bituminous

coal, the overall level of pollutants

emitted by those EGUs generally stayed

the same, as did county rankings of

weighted emissions scores. For

example, EPA explained that using the

new speciation data for a power plant

in Jefferson County, Indiana, would

not have changed its nonattainment

designation despite industry

petitioners' claim that it is among

the most problematic of EPA's

determinations. See J.A. at 2826

(Midwest Ozone Petition for

Reconsideration). Although the

weighted emissions score for Jefferson

County would have been lower, it still

would have been higher than

surrounding counties' scores because

of the significant levels of SO[2] and

NO[x] that the county's power plant

continued to emit. Johnson Attach. at

12. EPA dealt with the so-called

carbon error in a reasonable fashion.

D. Application of the Nine-Factor Test

As explained above, EPA uses nine

factors--including things like air

quality, population density, and

traffic patterns-to determine the

boundaries of areas contributing to

nearby PM[2.5] violations. See PM[2.5]

Designations Rule, 70 Fed. Reg. at

947; see also supra at 8. State

petitioners argue generally that EPA

arbitrarily applied its nine-factor

test by treating similarly situated

counties differently without

adequately explaining the allegedly

divergent outcomes. In each of their

challenges, petitioners seize upon

discrete data points and ignore the

very nature of the nine-factor test,

which is designed to analyze a wide

variety of data on a "case-bycase

basis," Holmstead Memo Guidance at 6.

It is EPA's holistic assessment of

numerous factors that drives the

process--no single factor determines a

particular designation. And although

petitioners seek to paint a picture of

systemwide inconsistencies, their

challenges really amount to an attack

on EPA's designations of a small group

of New York counties. Although we

address such individual challenges in

Part VI, we conclude here that with

respect to the system as a whole, EPA

consistently applied its nine-factor

test and adequately explained its

decisions based on record evidence.

1. First Factor: EPA's

Characterizations of County Emissions

The first of the nine factors EPA

uses to designate areas calls for the

agency to consider how emissions

levels contribute to nearby PM[2.5]

violations. In describing these

levels, EPA characterizes a county's

emissions as low, high, significant,

insignificant, and so forth. State

petitioners argue that EPA

characterized county emissions

inconsistently, providing further

evidence that the designations were

arbitrary. For example, petitioners

claim it is [*47] manifestly

arbitrary to designate as attainment

counties with emissions levels EPA

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
characterized as "low " based on

weighted emissions scores of 9.4

(Sevier County, Tennessee) and 6.3

(Jasper County, Georgia), while

designating as nonattainment counties

with lower scores of 4.5 (Orange

County, New York), 3.7 (Westchester

County, New York), and 1.9 (Rockland

County, New York). States' Opening Br.

34. As explained above, a weighted

emissions score reflects only a

county's share of a C/MSA's total

emissions. Weighted emissions scores

cannot be used in any meaningful way

to compare emissions levels between

counties in different C/MSAs. Because

cumulative emissions scores for all

counties within a C/MSA must total

100, areas with few counties (like the

Athens, Georgia, MSA) will invariably

have relatively larger county-level

scores than areas with numerous

counties (like the NY-NJ-CT-PA C/MSA),

even though emissions levels in the

smaller C/MSA may be lower.

Likewise, petitioners argue that

two instances in which EPA revised a

county designation from nonattainment

to attainment show that its

characterization of emissions data and

subsequent designations were

arbitrary. EPA originally described

the emissions levels in Woodford

County, Kentucky, as "significant" and

designated it as nonattainment.

Technical Support Document § 6.4.3.3

(Factor 1). But EPA later

concluded--without any change in

emissions levels--that the county "has

relatively low emissions," id.

(Justifications for Changes to EPA

Recommendations Contained in the June

24, 2004, Letters to States), and

revised its designation to attainment.

These changes, petitioners argue,

reflect the flawed manner in which EPA

applied the first factor. But EPA

adequately explained the change. After

the initial designation, Kentucky

submitted evidence that PM[2.5]

violations in nearby Fayette County

were due to local sources, not

emissions from Woodford County as

originally thought. Id. Petitioners

reply that EPA used the new data to

explain the change in Woodford

County's designation, not the change

in EPA's assessment of emissions

levels. To the extent that is even

true, though, we can reasonably

discern EPA's path. Given that the

weighted emissions score is a rough

estimate of a county's relative (and

relevant) emissions in the first

place, EPA simply interpreted the

numeric score differently when the new

data suggested its facial significance

was inaccurate.

In the same vein, petitioners

contend EPA acted arbitrarily in

revising its designation for Jasper

County, Georgia. Finding "significant

emissions" that potentially contribute

to PM[2.5] violations in other parts

of the region, EPA originally

designated the county as

nonattainment. See id. § 6.4.2.2

(Factor 1). Data later submitted by

Georgia, however, showed that

emissions from a source in Jasper

County were actually insignificant,

prompting EPA to redesignate the

county as attainment. See id. §

6.4.2.1 (Justification for Changes to

EPA Recommendations Contained in the

June 24, 2004, Letters to States);

Letter from Ron Methier, Chief, Air

Prot. Branch, Ga. Dep't of Natural

Res., to Beverly Bannister, Dir., Air,

Pesticides & Toxics Mgmt. Div., EPA

Region 4, at 2 (Nov. 1, 2004). Far

from being arbitrary, these revised

designations demonstrate the

reasonableness of EPA's case-by-case

approach to applying the first factor.

2. First Factor: EPA Region 1's Use

of a Bright-line Test

As explained in greater detail in

Part VI, EPA Region 1 used a

bright-line test to determine which

counties within a [*48] C/MSA would

be designated as attainment. The test

worked like this: EPA Region 1 ranked

each of its counties from highest to

lowest according to their weighted

emissions scores. Starting from the

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
top of the list, EPA Region 1 added

each county's score and stopped when

the sum hit 80%. Counties above the

80% cut-off point were presumed to be

nonattainment; those below were

designated as attainment, provided

they did not have a violating monitor

and were not among those recommended

for nonattainment status by a state.

See Technical Support Document § 6.1.1

(Factor 1). State petitioners argue

that application of this 80% test led

to inconsistent area designations, and

they are right in one instance.

Rockland County, New York, which is

not in EPA Region 1 and was designated

as nonattainment, would have been

designated as attainment under the 80%

test. Such an inconsistency is

evidence of an arbitrary designation,

but as Part VI explains, EPA's

mistaken designation of Rockland

County is an aberration, and

petitioners fail to identify any other

designation that might have changed

had EPA applied the 80% test

elsewhere. Nothing about the way EPA

Region 1 applied the first factor

reveals a fundamental problem with

EPA's evaluation of emissions in

potentially contributing areas.

3. Second Factor: Use of Design

Values

Under the second of the nine

factors, which looks to air quality,

EPA uses monitoring data to compute a

"design value" to describe the

concentration of ambient PM[2.5] in a

county. See supra at 12. The agency

then compares the design value to the

annual NAAQS to help determine whether

the county is violating PM[2.5]

standards or contributing to

violations nearby. See id.; EPA Br.

14. State petitioners argue that EPA

arbitrarily designated some counties

as nonattainment despite their

relatively low design values and other

counties as attainment despite their

higher design values. For example, EPA

designated Hardin County, Kentucky, as

attainment even though its design

value of 14.1 was higher than the 12.5

design value for Westchester County,

New York, which was designated as

nonattainment. See Technical Support

Document § 6.4.3.2 (Factor 2); id. §

6.2.2 (Factor 2).

As EPA explained, however, design

values alone do not determine

designations based on contribution.

Indeed, they are merely one component,

albeit an important one, of a complex

process that ultimately yields

designations. Petitioners' argument

ignores the multiple factors EPA uses

in making case-by-case assessments of

counties' contributions to nearby

violations. See Holmstead Memo

Guidance at 4. Some areas, like Hardin

County, may have relatively high

design values but still fall short of

violating the annual PM[2.5] standard

of 15 micrograms per cubic meter. And

many such counties are not

contributing areas because they have

low rankings for other factors like

population, traffic, and emissions

levels. See, e.g., Technical Support

Document § 6.4.3.2 (explaining Hardin

County's attainment designation). The

three areas state petitioners use as

examples of inconsistent

treatment--Nassau, Suffolk, and

Westchester Counties in New York--may

have had lower design values when

compared to other attainment areas,

but each ranked high for emissions

levels, population, and number of

commuters, all of which support the

determination that they contributed to

nearby violations. See id. § 6.2.2. In

short, EPA had ample evidence upon

which it based its designation of

these counties as nonattainment,

despite their relatively low design

values.

4. Sixth and Seventh Factors:

Distance Between a Power Plant and a

Violating Monitor

EPA takes account of the distance

between a power plant and a violating

[*49] monitor to help determine

whether an area's meteorological

features (the sixth factor) and its

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
particular geography and topography

(the seventh factor) will increase the

likelihood that emissions from the

plant will contribute to a violation.

State petitioners argue that EPA used

this distance inconsistently. For

example, the agency designated

Clearfield County, Pennsylvania, as

attainment even though it has a power

plant 60 miles from a violating

monitor. See id. § 6.3.4.2

(Discussion). By contrast, EPA

designated Orange County, New York, as

nonattainment even though its power

plant is 50 miles from the closest

violating monitor. See id. § 6.2.2.

But EPA never placed the type of

weight on the distance factor that

petitioners' argument assumes.

Although EPA considered the distances,

it weighed other factors as well. For

example, Orange County has very high

emissions levels, and meteorological

data show winds blowing from the

county toward violating monitors

elsewhere. See id. Clearfield County,

on the other hand, has mountainous

terrain and other geographic features

limiting emissions travel. See id. §

6.3.4.2 (Discussion). Petitioners

claim that the attainment designation

for Jasper County, Georgia,

demonstrates inconsistency because it

has a power plant 45 miles from the

nearest violating monitor. But the

plant's emissions are relatively

insignificant, and other factors--such

as low population and few

commuters--support the county's

designation. See id. § 6.4.2.1

(Justification for Changes to EPA

Recommendations Contained in the June

24, 2004, Letters to States); Letter

from Ron Methier to Beverly Bannister

at 2. Once again, seizing upon a

single factor misapprehends the

purpose of the nine-factor test.

5. Multiple Factors

Finally, petitioners compare

weighted emissions scores, design

values, population density, number of

commuters, and population growth for

four attainment counties (Lee County,

Alabama; Russell County, Alabama;

Sevier County, Tennessee; and Fulton

County, Ohio) with the same data for

one nonattainment county--New York's

Orange County--to illustrate that EPA

applied the nine factors

inconsistently, rendering the

designation process unpredictable and

arbitrary. See Technical Support

Document §§ 6.4.2.5, 6.4.6.2, 6.5.4.9.

Although this argument acknowledges,

where the others do not, that EPA

considers how the various factors

might work together, it fails for two

reasons. First, as we have already

explained, see supra at 15,

comparisons of weighted emissions

scores between counties in different

C/MSAs are meaningless. And second,

even though Orange County ranked

relatively low on some factors, which

might suggest it was a good candidate

for an attainment designation, it also

has emissions levels of PM[2.5],

SO[2], and NOx that far exceed the

levels of the four attainment counties

petitioners point to. See Technical

Support Document § 6.2.2. Orange

County's designation, which is

adequately justified, is yet another

illustration of the case-by-case

analysis that the Designations Rule

calls for and the nine-factor test

achieves.

VI.

Petitioners finally argue that even

if the PM[2.5] nonattainment

designations are reasonable as a

general matter, certain individual

county designations are independently

arbitrary and capricious. With but one

exception, we reject these challenges

as well.

A. New York County Designations

New York challenges the

nonattainment designations of five

counties surrounding New York City:

Suffolk, Westchester, [*50] Nassau,

Orange, and Rockland--collectively the

"outer counties." We find New York's

claims without merit, except for its

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
challenge to the designation of

Rockland County, which we remand to

EPA for additional explanation.

New York makes several broad

challenges to the designations of the

outer counties. Most generally, the

state argues that EPA's designations

lack a rational basis and that EPA

failed to respond to the comments New

York submitted. To justify the

nonattainment designations for

Westchester, Suffolk, and Nassau

Counties, EPA cites their high

emissions, population, traffic, and

commuting patterns. For Orange County,

EPA relies on high emissions, as

indicated by a weighted emissions

score ranking it fifth in the CMSA.

EPA also relies on meteorological data

to show that wind blows from each of

the outer counties toward the

violating monitors some percentage of

the time. Technical Support Document

at 6-24 to -36. EPA considered and

responded in some detail to New York's

comments challenging the designations.

Responses to Comments EPA Region 2 at

2-9 to -14. We find that EPA's basis

for designating Suffolk, Westchester,

Nassau, and Orange Counties can

reasonably be discerned from the

record. See Motor Vehicles Mfrs. Ass'n

v. State Farm Mut. Auto. Ins. Co., 463

U.S. 29, 43, 103 S. Ct. 2856, 77 L.

Ed. 2d 443 (1983) ("We will . . .

'uphold a decision of less than ideal

clarity if the agency's path may

reasonably be discerned.'" (quoting

Bowman Transp., Inc. v. Arkansas-Best

Freight Sys., Inc., 419 U.S. 281, 286,

95 S. Ct. 438, 42 L. Ed. 2d 447

(1974))).

New York next contends that EPA did

not correctly take into account

commuting data for the outer counties

and points to its own data showing

that only 13% of outer county

commuters drive to New York City.

States' Opening Br. 39. EPA responds

that the relevant factor on which it

relied was not the percentage of

commuters but rather the raw number of

commuters. New York correctly

highlights the inconsistency in EPA's

treatment of Rockland County's

commuter data, which is discussed

below, but as to the other counties,

New York's arguments are not

persuasive. The Technical Support

Document shows that Westchester and

Nassau Counties each have over 100,000

commuters to New York and Bronx

Counties. Technical Support Document

at 6-29. Suffolk County has fewer

commuters to New York and Bronx

Counties (roughly 44,000), but it has

higher Vehicle Miles Traveled (VMT)

than either Westchester or Nassau

Counties, likely due to its location

on eastern Long Island. Id. New York

is correct that Orange County's

commuter numbers and VMT are far lower

than any of the other three counties,

id., but EPA based Orange County's

nonattainment designation on its high

emissions, not its commuter numbers,

id. at 6-24. EPA's reliance on

commuting data is supported by the

record, which shows significant

numbers of commuters and VMT for

Westchester, Nassau, and Suffolk

Counties.

New York also maintains that EPA

impermissibly changed its theory of

outer county contribution from

contribution to a violating monitor in

New Haven, Connecticut, to

contribution to violating monitors in

Manhattan and the Bronx. EPA's initial

rationale for designation in the

Technical Support Document reads:

"Nassau County ranks high for

emissions, population, traffic, and

commuting patterns. In addition, an

analysis of pollution roses and back

trajectories to New Haven, CT showed a

contribution from Nassau County." Id.

Based on comments submitted by New

York and Connecticut, EPA agreed that

the violating New Haven monitor was

"not representative of community

exposure" [*51] and thus should not

be the basis of designations. See id.

at 6-35. EPA did not, however, change

the outer counties' designations on

this ground.

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
New York's claim that EPA's

continued nonattainment designations

were arbitrary fails because EPA's

rationale for the designations can be

discerned from the Technical Support

Document, which lists numerous reasons

for designation other than

contribution to the New Haven monitor.

It is a reasonable reading of the

Technical Support Document to

attribute the list of factors, such as

emissions and commuters, as referring

to contribution to the violating

monitors in Manhattan and the Bronx,

while the initial rationale for

contribution to New Haven was back

trajectories and pollution roses. More

important, New York is protesting the

iterative process of revision that the

CAA itself mandates: EPA revised its

position in response to New York's

comments. New York's underlying

complaint is that the iterations

should have continued, perhaps ad

infinitum. But such a process is

inconsistent with the CAA: Congress

imposed deadlines on EPA and thus

clearly envisioned an end to the

designation process.

Although we reject New York's

challenge to the designations of

Westchester, Suffolk, Nassau, and

Orange Counties, the state's challenge

to Rockland County's nonattainment

designation has merit. EPA appears to

have acted inconsistently in

designating Rockland County as a

nonattainment area.

First, New York persuasively shows

that Rockland's treatment was

inconsistent with the treatment of

other counties in the same CMSA that

fall within a different EPA region.

New York notes that EPA Region 1,

which encompasses the CMSA's New

England counties, employed what New

York terms an "80% test" in deciding

which counties would be designated

nonattainment. The Region 1 materials

do not reference such a test, but New

York is correct in its description of

the process EPA Region 1 apparently

employed. Region 1 "dropped" from

nonattainment consideration Litchfield

and Middlesex Counties in Connecticut

and Hampden and Berkshire Counties in

Massachusetts because: "(1) none of

these counties contain violating

PM[2.5] monitors, (2) none were

recommended for nonattainment

designation by the state, and (3) all

have emissions scores </= 2.5." Id. at

6-6. Region 1 arrived at the 2.5

cutoff by ranking all of the CMSA

counties from highest to lowest

weighted emissions score, summing the

weighted emissions scores from top to

bottom, and drawing a line after the

county at which the cumulative

emissions score equaled 80%--thus, the

"80% test." Any counties below the 80%

line were dropped from further

consideration if they did not contain

a violating monitor and were not

recommended by the state for a

nonattainment designation. See id. at

6-4 to -6. Although this may be a

reasonable approach in the abstract,

New York's complaint is that, if this

process had been applied in Region 2,

which includes the New York counties,

Rockland County would have been

dropped from consideration instead of

designated nonattainment. EPA responds

that the "80% test" was no test at

all. But the agency's characterization

is unavailing because no matter how

Region 1's process is characterized,

the fact remains that Rockland County

would have been designated attainment

if it had been in Region 1, but was

designated nonattainment by EPA Region

2. Such inconsistent treatment is the

hallmark of arbitrary agency action.

Second, EPA's rationale for

designating Rockland County changed

between the initial designation and

the final designation, with no

apparent change in data. The [*52]

only rationale EPA cited in its

initial designation of Rockland was

that Rockland "is contiguous to . . .

Orange and Westchester Counties," both

of which EPA designated as

nonattainment. Id. at 6-24. In the

initial designations, EPA

characterized Rockland County's

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2009 U.S. App. LEXIS 14948; 69 ERC (BNA) 1033
commuter numbers as "low," id. at

6-31; when it revised its

designations, EPA characterized

Rockland County's commuter numbers as

"significant," though there was no

intervening change in data, id. at

6-35.

Third, and relatedly, New York

argues that EPA treated Rockland

County differently than Dutchess

County in New York and Ocean County in

New Jersey, both of which were

designated attainment. New York notes

that both counties have similar or

worse values than Rockland on most or

all of the factors EPA assessed. EPA's

response, laid out in its brief to

this court, is that of the factors New

York cites, only commuting was

significant for Rockland, and that

Rockland's numbers of commuters to

violating counties are three times the

same statistic for Dutchess and Ocean

Counties. EPA also notes that Rockland

has large power plants, while Ocean

County does not. EPA Br. 154.

EPA's attempt to distinguish

Rockland County does not withstand

close inspection. First, EPA cannot

rely on Rockland's power plants to

distinguish Rockland from Ocean County

because power plants are solely a

proxy for emissions, and Rockland has

lower emissions than either Ocean or

Dutchess County. Second, EPA is

correct that, while Rockland has three

to four times the number of commuters

to violating counties as the other two

counties, EPA initially characterized

Rockland's commuter numbers as "low."

The agency's later rhetorical revision

of its characterization to

"significant" is not justified by any

change in the underlying data, which

renders suspect EPA's reliance on

commuters as the sole basis for

distinguishing Rockland from the other

two counties.

In sum, Rockland County's

nonattainment designation is troubling

because of the apparent inconsistency

in EPA's approach to designations in

different EPA regions, EPA's varying

characterizations of Rockland's

statistics, and EPA's treatment of

Rockland as compared to Dutchess and

Ocean Counties. In light of the

agency's scientific expertise and the

complexity of the designation process,

we remand to give EPA another

opportunity to provide a coherent

explanation for its designation. See,

e.g., North Carolina v. EPA, 550 F.3d

1176, 384 U.S. App. D.C. 70 (D.C. Cir.

2008).

B. Other Individual County Challenges

We have considered the other

individual county challenges lodged by

Petitioners and conclude that none of

them has merit. Our standard of review

is deferential. EPA "must examine the

relevant data and articulate a

satisfactory explanation for its

action including a 'rational

connection between the facts found and

the choice made.'" State Farm, 463

U.S. at 43 (quoting Burlington Truck

Lines, 371 U.S. at 168). The record

before us shows that EPA considered

numerous relevant factors for each

challenged county, and the evidence

supports the nonattainment

designations EPA promulgated. In the

accompanying judgment, we deny the

petitions for review of the remaining

individual county designations.

VII.

Having considered petitioners'

remaining arguments and finding them

without merit, we deny the petitions

for review in [*53] all respects

save one: the designation of Rockland

County is remanded to EPA.

So ordered.

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