United States Court of Appeals 

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued November 7, 2006 Decided December 12, 2006 

No. 05-1353 

UTILITY AIR REGULATORY GROUP,

PETITIONER

V. 

ENVIRONMENTAL PROTECTION AGENCY, 

RESPONDENT

Consolidated with Nos. 05-1354, 05-1357 

On Petitions for Review of a Final Action of 

the United States Environmental Protection Agency 

Peter S. Glaser argued the cause for industry petitioners 

Utility Air Regulatory Group in Case No. 05-1353 and Center 

for Energy and Economic Development in Case No. 05-1357. 

With him on the briefs were Paul M. Seby, Norman W. 

Fichthorn, Allison D. Wood, and Mel S. Schulze. 

 Ann Brewster Weeks argued the cause for environmental 

petitioner National Parks Conservation Association in Case 
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No. 05-1354. With her on the briefs were Jonathan F. Lewis

and David W. Marshall. 

 Pamela S. Tonglao and Ammie Roseman-Orr, Attorneys, 

U.S. Department of Justice, argued the cause for respondent. 

With them on the brief were John C. Cruden, Deputy 

Assistant Attorney General, and M. Lea Anderson, Attorney, 

U.S. Environmental Protection Agency. 

 Peter S. Glaser, Paul M. Seby, Norman W. Fichthorn, 

Allison D. Wood, and Mel S. Schulze were on the brief for 

industry intervenors Utility Air Regulatory Group and Center 

for Energy and Economic Development in support of 

respondent in Case No. 05-1354. 

Before: GARLAND and BROWN, Circuit Judges, and 

WILLIAMS, Senior Circuit Judge. 

Opinion for the Court filed by Senior Circuit Judge

WILLIAMS. 

WILLIAMS, Senior Circuit Judge: In the eastern United 

States, the average visual range in most natural parks and 

wilderness areas designated as Class I Federal areas, see 42 

U.S.C. § 7472(a), is less than 30 kilometers, about 20 percent 

of what it would be under natural conditions. See National 

Research Council, Protecting Visibility in National Parks and 

Wilderness Areas 1 (1993). In order to address this problem, 

the Environmental Protection Agency promulgated a Regional 

Haze Rule, 40 C.F.R. § 51.308, pursuant to Section 169A of 

the Clean Air Act (“CAA”), 42 U.S.C. § 7491. See Regional 

Haze Regulations and Guidelines for Best Available Retrofit 

Technology (BART) Determinations, 70 Fed. Reg. 39,104 

(July 6, 2005) (the “Haze Rule”). The Haze Rule requires that 

under specified circumstances states impose best available 

retrofit technology (“BART”) on any BART-eligible sources. 
3

The latter are a specific class of large stationary pollution 

sources that “were put in place between August 7, 1962 and 

August 7, 1977, and whose operations fall within one or more 

of 26 specifically listed source categories.” 70 Fed. Reg. at 

39,105/1; see also 40 C.F.R. § 51.301. The regulation calls 

for imposition of BART if the source “may reasonably be 

anticipated to cause or contribute to any impairment of 

visibility in any mandatory Class I Federal area.” 40 C.F.R. 

§ 51.308(e)(1)(ii). The Haze Rule also permits states to 

reduce haze by alternate means, including a regional 

approach, so long as the alternative would be “better-thanBART”—i.e., would improve visibility more rapidly than 

under BART. 40 C.F.R. § 51.308(e)(2). Aspects of the Haze 

Rule have been before this court twice before, Center for 

Energy and Economic Development v. E.P.A., 398 F.3d 653 

(D.C. Cir. 2005) (“CEED”); American Corn Growers Ass’n v. 

E.P.A., 291 F.3d 1 (D.C. Cir. 2002) (“Corn Growers”), and 

those opinions contain extensive discussions of the rule’s 

statutory framework and regulatory history. 

This case involves challenges from multiple groups, 

including the Center for Energy and Economic Development 

and the Utility Air Regulatory Group (“industry petitioners”), 

and the National Parks Conservation Association 

(“environmental petitioner”). In its brief, EPA succinctly 

summarizes the challenges: “Industry Petitioners generally 

challenge the rule as inappropriately requiring States to apply 

BART to too many sources, while the Environmental 

Petitioner argues that the rule improperly allows States to 

exempt too many sources from BART.” Because we believe 

the Haze Rule is a reasonable interpretation of CAA § 169A, 

we affirm the rule against both sets of challenges. 
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* * * 

As we explained in Corn Growers, § 169A(a)(1) of the 

Clean Air Act established a national goal of preventing and 

remedying existing visibility impairment at Class I areas, and 

CAA § 169A(b)(2) directs EPA to issue regulations requiring 

that states adopt measures—including BART—to make 

“reasonable progress” towards meeting this national goal. See 

Corn Growers, 291 F.3d at 5-6. 

As outlined in § 169A(b)(2)(A) and implemented by the 

Haze Rule, the BART process consists of two steps. First, in 

the “Attribution Step” (“Step I”), states must review each 

“BART-eligible source” within the state to determine whether 

any such source emits “any air pollutant which may 

reasonably be anticipated to cause or contribute to any 

impairment of visibility in any mandatory Class I Federal 

area;” sources that do so are “subject to BART.” See 40 

C.F.R. § 51.308(e)(1)(ii). An earlier preamble to the Haze 

Rule required states to “find that a BART-eligible source is 

‘reasonably anticipated to cause or contribute’ to regional 

haze if it can be shown that the source emits pollutants within 

a geographic area from which pollutants can be emitted and 

transported downwind to a Class I area,” an approach known 

as “collective contribution.” Regional Haze Regulations, 64 

Fed. Reg. 35,714, 35,740/1 (July 1, 1999). In Corn Growers

we struck down such guidance as “inconsistent with the Act’s 

provisions giving the states broad authority over BART 

determinations.” 291 F.3d at 8 (emphasis added). In doing 

so, however, we did not foreclose the states themselves from 

deciding to take a collective approach in the Attribution Step, 

see id. at 18 (Garland, J., dissenting on other grounds), and the 

current rule identifies “collective contribution” as only one of 

at least three different approaches that a state may take in 

meeting its obligations under CAA § 169A(b)(2)(A). See 70 

Fed. Reg. at 39,117/2. Under the current Haze Rule, a state 
5

can complete the Attribution Step by using collective 

attribution, by demonstrating that, cumulatively, none of its 

BART-eligible sources contributes to visibility impairment, or 

by analyzing each source’s individual contribution. Id. States 

“may also use other reasonable approaches for analyzing the 

visibility impacts of an individual source or group of sources.” 

70 Fed. Reg. at 39,162/1. 

The second step outlined in § 169A(b)(2)(A), the 

“Determination Step” (“Step II”), requires states to determine 

the particular technology that an individual source “subject to 

BART” must install. That determination requires 

consideration of five factors: “the cost of compliance, the 

energy and nonair quality environmental impacts of 

compliance, any existing pollution control technology in use 

at the source, the remaining useful life of the source, and the 

degree of improvement in visibility which may reasonably be 

anticipated to result from the use of such technology.” 42 

U.S.C. § 7491(g)(2); see also 40 C.F.R. § 51.308(e)(1)(ii); 70 

Fed. Reg. at 39,163/3. In Corn Growers, we held that these 

five factors “were meant to be considered together by the 

states,” 291 F.3d at 6, but that EPA could not require the 

states to evaluate the improvement factor collectively while 

mandating that the other four factors be evaluated separately 

for each individual source. Compare id. at 8 with id. at 8-9. 

BART is not, however, the sole means by which states 

can meet their obligations under the Clean Air Act. The Haze 

Rule also permits states 

to implement or require participation in an emissions 

trading program or other alternative measure rather than 

to require sources subject to BART to install, operate, and 

maintain BART. Such an emissions trading program or 

other alternative measure must achieve greater reasonable 
6

progress than would be achieved through the installation 

and operation of BART. 

40 C.F.R. § 51.308(e)(2). We affirmed the use of such “better 

than BART” approaches in CEED, though we objected to the 

particular program under review there. See CEED, 398 F.3d 

at 660. We said nothing about how better-than-BART might 

be measured. 

After our CEED decision, EPA introduced the following 

test to evaluate whether a BART-alternative achieves “greater 

reasonable progress” than BART: 

If the distribution of emissions is not substantially 

different than under BART, and the alternative measure 

results in greater emission reductions, then the alternative 

measure may be deemed to achieve greater reasonable 

progress. If the distribution of emissions is significantly 

different, the State must conduct dispersion modeling 

. . . . The modeling would demonstrate “greater 

reasonable progress” if both of the following two criteria 

are met: 

(i) Visibility does not decline in any Class I 

area, and 

(ii) There is an overall improvement in 

visibility, determined by comparing the average 

differences between BART and the alternative over 

all affected Class I areas. 

40 C.F.R. § 51.308(e)(3). 

On March 10, 2005, EPA issued the Clean Air Interstate 

Rule (“CAIR”), requiring reductions in emissions of sulfur 

dioxide and nitrogen oxides in 28 eastern states and the 
7

District of Columbia. 70 Fed. Reg. 25,162 (May 12, 2005); 

see also 70 Fed. Reg. at 39,106/3. CAIR imposes specified 

emissions reduction requirements on each affected state, and 

enables states to meet the requirements by means of cap-andtrade programs. 70 Fed. Reg. at 39,106/3. In conjunction with 

the introduction of CAIR, EPA amended the Haze Rule to add 

a new regulation—contested here—providing that “[a] State 

that opts to participate in the Clean Air Interstate Rule capand trade . . . program . . . need not require affected BARTeligible EGUs [electric generating units] to install, operate, 

and maintain BART.” 40 C.F.R. § 51.308(e)(4); 70 Fed. Reg. 

39,156/3]; see also 70 Fed. Reg. 39,138-39 (noting that the 

CAIR-for-BART comparison is to be evaluated under the 

standards enumerated in § 51.308(e)(3)); 70 Fed. Reg. 

39,142/3 (same). 

In adopting the current version of § 51.308(e)(4), EPA 

provided analyses demonstrating that CAIR would achieve 

greater overall emission reductions than BART, and would 

make greater reasonable progress according to the twopronged visibility test outlined in § 51.308(e)(3)—i.e., that 

CAIR would result in a greater aggregate visibility 

improvement (than BART) averaged over all Class I areas 

without reducing visibility at any individual area. See 70 Fed. 

Reg. at 39,136; see also Technical Support Document for the 

Final Clean Air Interstate Rule, March, 2005, at 

http://www.epa.gov/cair/pdfs/finaltech04.pdf (“CAIR TSD”). 

In doing so, however, EPA also noted that the “determination 

that CAIR makes greater reasonable progress than BART for 

EGUs is not a determination that CAIR satisfies all reasonable 

progress requirements in CAIR affected States . . . . [A state] 

cannot assume that CAIR will satisfy all of its visibilityrelated obligations.” 70 Fed. Reg. at 39,143/3. In particular, 

despite the rule changes reflecting CAIR, the EPA retained a 

regulation specifying that states must establish reasonable 
8

progress goals “[f]or each mandatory Class I Federal area 

located within [a] State,” and that such goals must “provide 

for an improvement in visibility for the most impaired days 

. . . and ensure no degradation in visibility for the least 

impaired days . . . .” 40 C.F.R. § 51.308(d)(1) (emphasis 

added). 

On October 13, 2006, EPA once again promulgated 

revisions to the Haze Rule—revisions for some reason not 

called to our attention by any of the lawyers in this case. See 

Revisions to Provisions Governing Alternative to SourceSpecific Best Available Retrofit Technology (BART) 

Determinations, 71 Fed. Reg. 60,612 (Oct. 13, 2006). Those 

revisions largely appear to respond to this court’s decision in 

CEED. For example, the new rule both clarifies the process 

by which BART-alternatives are to be compared to BART and 

provides minimum elements for cap-and-trade programs 

adopted in lieu of BART. Id. at 60,612. But as the new rule 

does not become effective until December 12, 2006, and was 

not briefed or even mentioned by counsel, its specifics are not 

under consideration here. Our own perusal hasn’t uncovered 

any changes undermining our conclusions; in fact, in at least 

one instance (discussed below), the new rule corresponds with 

concessions that EPA made at oral argument but not in its 

original briefs to this court.

* * * 

Industry petitioners argue that EPA acted contrary to 

statutory authority in two respects: first, by authorizing a state 

to infer, from evidence that its BART-eligible sources 

collectively contribute to visibility impairment in at least one 

Class I area, that all such sources may reasonably be 

anticipated to cause or contribute to visibility at such an area, 

without a source-by-source analysis—i.e., by authorizing the 
9

use of collective attribution—and, second, by issuing 

mandatory guidelines for the states’ attribution determinations 

for power plants exceeding 750 megawatts (“MW”). We 

reject both arguments. 

Industry petitioners claim that the collective attribution 

process allows states virtually to skip the Attribution Step; 

“once a State finds that a single BART-eligible source in the 

State affects visibility in a Class I area, other BART-eligible 

sources in the State may be swept into the BART 

Determination process without any analysis as to their effect 

on visibility.” This is true, but because the substance of the 

impact issue remains open in Step II, it is of little consequence 

(with one exception, described below). 

Industry petitioners’ valid concern is that collective 

attribution will force sources to install BART even when such 

installations would serve no purpose whatsoever. But this 

fear is unwarranted. As EPA openly conceded at oral 

argument, if an individual source is found subject to BART in 

Step I because of collective attribution, that source can 

nonetheless challenge the necessity of installing BART in 

Step II—and have the impact issue resolved de novo. See 

Transcript of Oral Argument at 19-20. Recall that Step II 

involves the weighing of five factors, the last of which is the 

visibility impact of imposing BART. If that impact is zero

because the source does not contribute to visibility 

impairment in the first place, then the source need not impose 

BART, regardless of the results dictated by the other four 

factors or the use of collective attribution in Step I. Counsel 

for EPA, commenting in oral argument on the passage in 

EPA’s description of the BART determination process that 

industry found most alarming (“States, as a general matter, 

must require owners and operators of greater than 750 MW 

power plants to meet these BART emission limits,” 70 Fed. 

Reg. at 39,131/3), repeatedly confirmed that a finding of zero 
10

impact at this stage would trump the four remaining factors 

and excuse the application of BART. See Transcript of Oral 

Argument at 17. (This interpretation is in part paralleled in 

the October 13 revisions to the Haze Rule: “Where a State 

takes this approach [i.e., collective attribution], the 

opportunity for assessing source-by-source visibility impact 

would still remain at the next step of setting the benchmark—

the BART determination analysis.” 71 Fed. Reg. at 60,615/2.) 

We adopt counsel’s interpretation as our own understanding 

of the interplay between Steps I and II of the Haze Rule and 

between the impact criterion and the other factors. 

That individual sources found subject-to-BART under 

collective attribution can nonetheless challenge the necessity 

of installing BART at the Determination Step does not render 

collective attribution a meaningless exercise. By setting a low 

threshold above which sources “may reasonably be 

anticipated to cause or contribute to any impairment,” CAA 

§ 169A(b)(2)(A), collective attribution essentially places on a 

source itself the burden of demonstrating that it doesn’t 

contribute to visibility impairment. At oral argument, counsel 

for industry disclaimed any legal quarrel with EPA’s 

assignment of the burden. See Transcript of Oral Argument at 

12, 24. We find EPA’s interpretation reasonable as against 

industry’s challenges. 

Industry petitioners’ second argument is that EPA’s 

guidelines for state attribution determinations for power 

plants exceeding 750 MW are mandatory for the states, 

contrary to industry’s reading of the statute. But the industry 

briefs point to no such mandatory language. It is surely true 

that several elements of the Haze Rule purport to establish 

mandatory guidelines as to the Determination Step of the 

process. See, e.g., 70 Fed. Reg. at 39,131/3. Moreover, some 

passages identified in the briefs are ambiguous as to the force 

of EPA’s provisions. See, e.g., 70 Fed. Reg. at 39,123 (“In 
11

the unlikely case that a State were to find that a 750 MW 

power plant’s predicted contribution to visibility impairment 

is within a very narrow range between exemption from or 

being subject to BART, that the State can work with EPA 

. . . .”). 70 Fed. Reg. at 39,123/2. EPA’s brief, though not 

focusing on this passage, argued that these attribution 

guidelines were “advisory, not mandatory, as to all sources, 

including 750 megawatt power plants.” There appears to be 

no language in the rule which contradicts this claim; having 

defended the regulations on the basis that they are advisory 

here, EPA cannot later rely on a reading that they are 

mandatory. Of course states must still meet EPA’s explicit—

if rather general—requirement of a State Implementation Plan 

(“SIP”) that can satisfy the statute’s reasonable progress 

criterion, as construed by EPA. See 42 U.S.C. § 7491(b)(2) 

(requiring states to submit SIPs containing emission limits, 

schedules of compliance, and other measures necessary to 

make reasonable progress toward meeting the national 

visibility goal). But we do not understand industry to argue 

that such indirect compulsion violates the statute. 

* * * 

The environmental petitioner argues that EPA’s 

substitution of CAIR for BART contravenes the language and 

structure of the Clean Air Act because it cannot guarantee 

“reasonable progress” at all Class I areas. This argument is 

predicated on a belief that the Clean Air Act requires that 

BART-alternatives such as CAIR “do better” than BART at 

each individual Class I area (as opposed to simply in the 

aggregate), and, evidently, on every type of day (best days, 

worst days, etc.). 

EPA’s preliminary response is that environmental 

petitioner lacks standing because it has not been (and will not 
12

be) injured by the CAIR-for-BART rule. But EPA’s own 

evidence shows the likelihood that states will adopt CAIR and 

that CAIR will be less effective at a few areas on some days. 

When CAIR was first introduced EPA noted that “[b]ased on 

our experience . . . we anticipate that States will choose to 

require EGUs to participate in the cap and trade programs 

administered by EPA.” 69 Fed. Reg. 4,566, 4,586/3 (Jan. 30, 

2004). EPA’s technical analysis of CAIR then went on to 

predict that, at three (out of 156) Class I areas, such 

participation would result in visibility improvements on the 

best 20% of days that are less than the expected improvements 

at those areas under BART. See CAIR TSD 18. (The same 

analysis shows equal or superior visibility at all Class I areas 

on the 20% worst days. See id. at 23.) 

Those findings, of course, do not in themselves show that 

petitioners’ members will travel to the parks likely to be 

negatively impacted by the CAIR-for-BART Rule. Indeed, 

petitioner’s affidavits do not clearly indicate that its members 

visit every park, let alone that they visit the three operative 

parks on the best 20% of days. But given the organization’s 

large membership—over 320,000 members in all 50 states—

we find it reasonable to infer that at least one member will 

suffer injury-in-fact. We do so with some hesitation, 

however. While some judicial opinions purport to reject 

reliance on mathematical likelihood, see, e.g., Sargent v. 

Mass. Accident Co., 29 N.E.2d 825, 827 (Mass. 1940) ( “It 

has been held not enough that mathematically the chances 

somewhat favor a proposition to be proved”), that viewpoint 

overlooks the reality that all empirical issues are matters of 

probability. But it is at least an imposition for a party to force 

courts to rely on statistical inference when the party 

presumably has better evidence within easy reach—here, a 

member’s affidavit showing a high individualized probability 

of future visits to a particular park (presumably based on a 
13

pattern of past visits). Cf. United States v. Veysey, 334 F.3d 

600, 605 (7th Cir. 2003). Nevertheless, the size of petitioner’s 

membership appears large enough here to indicate substantial 

probability of injury. 

Having found that petitioner has standing, we nonetheless 

squarely reject its claim that the Clean Air Act requires EPA 

to ensure that any BART-alternative improves visibility at 

least as much as BART at every Class I area and in all 

categories of days. The plain language of the Act imposes no 

such mandate, and EPA’s refusal to read one in is reasonable. 

As we said in Corn Growers, “[t]he statutory goal 

enunciated in [CAA] § 169A(a)(1) is quite clear: ‘the 

prevention of any future, and the remedying of any existing, 

impairment of visibility.’” 291 F.3d at 10 (citing 42 U.S.C. 

§ 7491(a)(1)). In order to meet this goal, the Clean Air Act 

specifically calls for regulations to assure that “reasonable 

progress” is made by the states. 42 U.S.C. § 7491(a)(4). 

Because “reasonable progress” is nowhere defined in the Act 

itself, we review EPA’s interpretation of the term under the 

standard framework of Chevron U.S.A., Inc. v. Natural 

Resources Defense Council, Inc., 467 U.S. 837 (1984), and 

defer to the agency’s interpretation so long as it is reasonable. 

Recall that under the Haze Rule reasonable progress 

means that “[f]or each mandatory Class I Federal area . . . 

[states] must provide for an improvement in visibility for the 

most impaired days . . . and ensure no degradation in visibility 

for the least impaired days over the same period.” 40 C.F.R. 

§ 51.308(d)(1) (emphasis added). Moreover, unless there is 

some reasonable excuse, this progress must be sufficient to 

attain natural visibility conditions at every single Class I area 

by 2064. 40 C.F.R. § 51.308(d)(1)(ii). Indeed, EPA 

emphasized in its briefs that because “the regulatory scheme 

as a whole (and all the regulations promulgated pursuant to it) 
14

must be designed to achieve the goal [of reasonable progress] 

at every Class I area,” EPA Br. at 66 (emphasis added), states 

must, if CAIR is substituted for BART and is not likely to 

achieve that goal, take “other measures as necessary to 

achieve reasonable progress goals including at each Class I 

area,” id. at 67 (emphasis added). Thus, EPA not only agrees 

with petitioner that CAA § 169A(a)(1)’s declaration of a 

“national goal” that includes “the remedying of any existing[]

impairment of visibility . . . [that] results from manmade air 

pollution” implies a need for ubiquitous improvement over 

time (emphasis added), but it has adopted regulations 

manifesting that goal. 

Nonetheless, the Clean Air Act leaves wide discretion 

about how the goal is to be achieved. Notwithstanding the 

Act’s discussion of BART in § 169A(b), we have already held 

in CEED that EPA may leave states free to implement BARTalternatives so long as those alternatives also ensure 

reasonable progress. 398 F.3d at 660. Moreover, nothing in § 

169A(b)’s “reasonable progress” language requires at least as 

much improvement at each and every individual area as 

BART itself would achieve (much less improvement at each 

area at every instant); and EPA’s requirement of some 

improvement at all areas on the worst days, coupled with no 

degradation at any area on the best days, 40 C.F.R. 

§ 51.308(d)(1), appears a reasonable notion of reasonable 

progress. Finally, EPA allows use of a BART alternative only 

if it combines aggregate improvement (relative to BART) 

with universal, area-specific absence of degradation, 40 

C.F.R. § 51.308(e)(3); on this metric CAIR-for-BART is far 

better than BART. 70 Fed. Reg. at 39,138-39,142. 

Petitioner also appears to argue that the origin of CAIR in 

other clean air programs precludes EPA’s decision to allow 

states the CAIR option in fulfillment of § 169A. But 

petitioner identifies no language requiring EPA to impose a 
15

separate technology mandate for sources whose emissions 

affect Class I areas, rather than piggy-backing on solutions 

devised under other statutory categories, where such solutions 

meet the statutory requirements. 

The petitions for review are therefore 

Denied.