Document ID: s3://data.kl3m.ai/documents/govinfo/USCOURTS/USCOURTS-caDC-07-01428/USCOURTS-caDC-07-01428-0/pdf.json

Parties Involved:
Environmental Protection Agency
Respondent
Stephen L. Johnson
Respondent
Oakland County, Michigan
Petitioner

Document Text:

United States Court of Appeals 

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued April 6, 2009 Decided July 7, 2009 

No. 05-1064 

CATAWBA COUNTY, NORTH CAROLINA, ET AL., 

PETITIONERS

v. 

ENVIRONMENTAL PROTECTION AGENCY, 

RESPONDENT

SIERRA CLUB, 

INTERVENOR

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 

On Petitions for Review of Final Actions 

of the Environmental Protection Agency 

Marc D. Machlin argued the cause and filed the briefs for 

petitioner Oakland County, Michigan. 

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Louis E. Tosi argued the cause for Industry Petitioners. 

With him on the briefs were Paul E. Gutermann, Charles L. 

Franklin, Douglas A. McWilliams, Allen A. Kacenjar, 

Michael E. Born, Cheri Ann Budzynski, Gale Lea Rubrecht, 

Kathy G. Beckett, David M. Flannery, and Edward L. Kropp. 

Andrew M. Cuomo, Attorney General, Attorney General=s 

Office of the State of New York, Michael J. Myers and Jacob 

Hollinger, Assistant Attorney Generals, Mark Rudolph, 

Senior Counsel, Office of Legal Services, West Virginia, 

Steve Carter, Attorney General, Attorney General=s Office of 

the State of Indiana, Steve D. Griffin and Valerie Tachtiris, 

Deputy Attorneys General, and Thomas M. Fisher, Special 

Counsel, were on the briefs of State Petitioners. 

Karma Barsam Brown, Phillip L. Conner, Ronald E. 

Cardwell, Ethan R. Ware, George William House, S. Kyle 

Woosley, and Lewis S. Wiener were on the briefs for County 

Petitioners.

Laurel A. Bedig and Monica Derbes Gibson, Attorneys, 

and Jon M. Lipshultz, Senior Counsel, U.S. Department of 

Justice, argued the cause for respondent. With them on the 

brief were John C. Cruden, Deputy Assistant Attorney 

General, Jessica O’Donnell, Attorney, and Geoffrey L. 

Wilcox, Counsel, U.S. Environmental Protection Agency. 

Kenneth C. Amaditz, Attorney, U.S. Department of Justice, 

entered an appearance. 

David S. Baron and Jennifer C. Chavez were on the brief 

for intervenor. Howard I. Fox entered an appearance. 

Before: TATEL, GARLAND, and GRIFFITH, Circuit Judges. 

Opinion for the Court filed PER CURIAM. 

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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 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 

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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 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 

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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 PM2.5, 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 (“PM2.5 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 PM2.5 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 

PM2.5 concentrations—PM2.5 can travel hundreds or thousands 

of miles. 

In 1997, EPA abandoned its practice of regulating all 

particulate matter, both coarse and fine, under a unified 

standard. Instead it established specific PM2.5 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 PM2.5 NAAQS, setting 

the annual standard—the one at issue here—at 15 micrograms 

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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 (D.C. Cir. 2002), on remand 

from Whitman v. Am. Trucking Ass’ns, 531 U.S. 457 (2001), 

aff’g in part and rev’g in part Am. Trucking Ass’ns v. EPA, 

175 F.3d 1027 (D.C. Cir. 1999). In the meantime, Congress 

had passed legislation requiring the deployment of a 

nationwide PM2.5 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 PM2.5 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 

PM2.5 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 PM2.5

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: 

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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 PM2.5 national ambient air 

quality standards. 

§ 7407(d)(6)(B). 

In April 2003, EPA issued a guidance document initiating 

the PM2.5 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 PM2.5 

air quality standards generally include a significant urbanscale 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 PM2.5 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 statistical areas (CMSAs) 

(interchangeably, “C/MSAs”). Id. Thus, under this approach, 

a violation of the PM2.5 NAAQS in the District of Columbia, 

for instance, would trigger the presumption that seventeen 

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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 PM2.5

levels in the city and warrant “nonattainment” designations. 

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 

PM2.5 concentrations in and near many metropolitan areas,” 

the agency had “found an association of higher PM2.5 

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 PM2.5, 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 PM2.5 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 

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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 PM2.5 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. PM2.5 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 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 PM2.5 problem, EPA designated the urban 

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nonattainment area as either an area larger than the OMBdefined metropolitan area (for instance, in Chattanooga, 

Tennessee) or smaller (for instance, in Washington, DC). 

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. 

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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 PM2.5 precursors that sources 

emit. PM2.5 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/aqtrnd04/pm. 

html. The chemical precursors to secondary PM2.5 include 

sulfur dioxide (SO2), emitted in substantial part by power 

plants; nitrogen oxides (NOx), 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 PM2.5 Designations Rule, 70 

Fed. Reg. at 945; Technical Support Document § 3.1. 

Atmospheric chemical reactions between these gases yield 

secondary PM2.5 in the form of sulfate and nitrate particles. 

PM2.5 Designations Rule, 70 Fed. Reg. at 945. The PM2.5

NAAQS set a 15μg/m3

 annual limit for all fine particulate 

matter without distinguishing among the various kinds (or 

“species”) of PM2.5. Even so, “speciation data” that breaks 

the total PM2.5 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 PM2.5 

problem, it suggests, by extrapolation, the kinds of sources 

most responsible for the problem as well. 

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While the Holmstead Memo announced EPA’s 

methodology for determining whether an area with passable 

PM2.5 concentrations nonetheless deserves a “nonattainment” 

designation, EPA regulations set forth the technical 

procedures for measuring ambient PM2.5 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 PM2.5 concentration, 

what’s called the “design value,” on any given day. The 

annual design value—which determines whether an area 

complies with the PM2.5 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 PM2.5 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] PM2.5 monitor.” PM2.5 

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 

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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 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 PM2.5 can travel 

in the atmosphere, EPA thought it important to isolate the 

portion of urban PM2.5 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 direction of the metropolitan area—and 

“subtract[ed] the rural concentration from the measured 

urban concentration.” Id. § 3.1. True to name, this simple 

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arithmetic allowed EPA to estimate the portion of urban PM2.5 

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 

PM2.5 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 PM2.5 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 PM2.5 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, 

SO2, NOx, 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 

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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 PM2.5 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 PM2.5 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 

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 failing to 

publish both the Rule and the Holmstead Memo for notice and 

comment. They are in error as to both. 

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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 PM2.5 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 

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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 (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) 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 PM2.5

national ambient air quality standards . . . .” § 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 PM2.5 designations, 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 17 of 56
18 

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 noticeand-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 (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). 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 18 of 56
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 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, 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 

(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 

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-à-vis the 

states: “A demonstration supporting the designation of 

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20 

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 (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 (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 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 20 of 56
21 

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 PM2.5

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 PM2.5 Designations— 

Preliminary Recommendations, with PM2.5 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 

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 Air Act by applying the C/MSA presumption and 

nine-factor test to identify areas that contribute to nearby 

PM2.5 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 

(D.C. Cir. 2008). But if the statute is either silent or 

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22 

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 (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 (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 (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 PM2.5 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 

(D.C. Cir. 2004); accord. Nuclear Energy Inst., Inc. v. EPA, 

373 F.3d 1251, 1269 (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 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 22 of 56
23 

area contributes to a nearby PM2.5 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 (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 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 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 PM2.5 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. 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 23 of 56
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16, 23 (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 (D.C. Cir. 

1990); see also Clinchfield Coal Co. v. Fed. Mine Safety & 

Health Review Comm’n, 895 F.2d 773, 779 (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 (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 PM2.5 like ozone and carbon monoxide 

but chose an altogether different scheme in subsection 

(d)(6)—one “based on air quality monitoring data,” 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 24 of 56
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§ 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 PM2.5 like 

the one that Congress mandated for ozone and carbon 

monoxide in subsection (d)(4). But nothing in subsection 

(d)(6) even hints at such a prohibition. Subsection (d)(6)(A) 

requires states to submit PM2.5 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” 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 PM2.5 

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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 

(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 

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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 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 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 PM2.5 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 PM2.5 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 

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§ 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 PM2.5 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 

PM2.5 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 (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. 

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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 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 fatally 

undermines petitioners’ Chevron step one argument. See 

Cellular Telecomms. & Internet Ass’n v. FCC, 330 F.3d 502, 

509 (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 

(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 PM2.5 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 

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30 

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 (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 (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, 

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id. at 1194, something the Holmstead Memo and certainly the 

Technical Support Document did in spades. Of course, EPA 

may have applied 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 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’ 

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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 (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 PM2.5 NAAQS. 

Acting on evidence that urban PM2.5 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 

PM2.5 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 

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33 

Rule in four regards: EPA’s designation of noncontiguous 

townships as nonattainment, the agency’s refusal to account 

for some potential emissions reductions, the 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 (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 (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 (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 

(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. 

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34 

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 

PM2.5 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 PM2.5 monitor.” PM2.5

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 PM2.5 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 

PM2.5 violation. See PM2.5 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 that 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 34 of 56
35 

designations should be made at the county level. Because 

emissions from a 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.” PM2.5

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 PM2.5 emissions. For example, the 

Conesville Plant in Franklin Township emitted 99% of the 

SO2, 90% of the NOx, 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 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 35 of 56
36 

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 PM2.5

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 PM2.5 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 PM2.5. But ozone was the subject of a different 

designations process and a separate rulemaking, and nothing 

compels EPA to use the same approach for PM2.5. Petitioners 

emphasize that PM2.5 and ozone are both pollutants that can 

travel long distances. That similarity alone, however, is not 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 36 of 56
37 

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 PM2.5 designations 

process, it explained that “unlike ozone,” PM2.5 “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 PM2.5

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 NOx

State Implementation Plan (also known as the “NOx SIP 

Call”). See generally North Carolina v. EPA, 531 F.3d 896, 

902–03 (D.C. Cir.) (describing programs), modified, 550 F.3d 

1176 (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 SO2 and NOx

emissions from upwind sources in 28 states and the District of 

Columbia that contribute to nonattainment levels for ozone 

and PM2.5 in downwind states. Id. at 903. When EPA made 

its PM2.5 designations, it reasonably decided emissions 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 37 of 56
38 

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 

PM2.5 emissions for specific sources. Indeed, CAIR did not 

require states to submit to EPA their recommendations as to 

which power plants would reduce SO2 and NOx emissions and 

how they would do so until September 2006—nearly two 

years after the agency had designated areas under the PM2.5

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 effect until more than a year 

after the agency had completed designating areas. See

Rulemaking on Section 126 Petition from North 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 

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39 

CAIR when it promulgated the PM2.5 designations in 

December 2004. See Johnson Attach. at 8 n.11. 

It was likewise reasonable for EPA to disregard 

forecasted reductions from the NOx SIP Call. Created to 

reduce ozone pollution, this program requires 22 upwind 

states and the District of Columbia to decrease NOx

emissions, a significant precursor to PM2.5, but it has nothing 

to do with reducing SO2, another significant PM2.5 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 SO2 in their respective areas. See Johnson Attach. at 8. 

EPA concluded that reducing NOx but not SO2 was a step in 

the right direction for reducing PM2.5, 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 SO2, EPA reasonably decided not to 

alter nonattainment designations based only on forecasted 

reductions in NOx. 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 NOx and 

SO2). 

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. 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 39 of 56
40 

Among the analytical tools EPA uses to make 

designation determinations is a county’s weighted emissions 

score, which allows the agency to compare SO2, NOx, carbon, 

and crustal emissions across counties within a C/MSA. See

PM2.5 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 PM2.5

emissions, as well as SO2, NOx, carbon, and crustal emissions 

for each county. See What Is the National Emissions 

Inventory (NEI)?, http://www.epa.gov/ttn/chief/net/neiwhatis. 

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/ 

speciation/ (last visited June 11, 2009). 

The speciation profile EPA used for large electric 

generating units (EGUs) estimated that carbon makes up 21% 

of their PM2.5 emissions. As it turns out, that estimate was 

wrong for plants that burn bituminous coal. Carbon accounts 

for only 2.9% of their PM2.5 emissions. See J.A. at 2848–49. 

EPA updated the speciation profile for these plants in its 2006 

revision of the PM2.5 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 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 40 of 56
41 

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 PM2.5. 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 PM2.5 emissions estimates. Instead, 

the proportions of pollutants emitted by these sources 

changed. Specifically, the estimate of crustal particles, also a 

precursor to PM2.5, 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 (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 (1944), and Vermont 

Yankee Nuclear Power Corp v. Natural Resources Defense 

Council, 435 U.S. 519 (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. 

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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 PM2.5 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 multifactored 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 evaluation of 

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. 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 42 of 56
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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 SO2 and NOx 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 PM2.5 violations. See PM2.5 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 

USCA Case #07-1428 Document #1194958 Filed: 07/07/2009 Page 43 of 56
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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 PM2.5 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 manifestly 

arbitrary to designate as attainment counties with emissions 

levels EPA 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 

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45 

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 

PM2.5 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, 

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46 

Georgia. Finding “significant emissions” that potentially 

contribute to PM2.5 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 

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 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 

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47 

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 PM2.5 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 PM2.5 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 

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design values but still fall short of violating the annual PM2.5

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 monitor to help determine whether an area’s 

meteorological features (the sixth factor) and its 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 

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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 PM2.5, SO2, and NOx that far exceed 

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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 PM2.5

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, Nassau, Orange, and Rockland—collectively the 

“outer counties.” We find New York’s claims without merit, 

except for its 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 

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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 (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 (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. 

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 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” 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. 

 

 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. 

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 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 PM2.5 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 

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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 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 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. 

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 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 (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 

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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 all respects save one: the designation of Rockland County 

is remanded to EPA. 

So ordered. 

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