PRECEDENTIAL

UNITED STATES COURT OF APPEALS

FOR THE THIRD CIRCUIT

_____________

No. 14-3147

_____________

NATIONAL PARKS CONSERVATION ASSOCIATION; 

SIERRA CLUB; CLEAN AIR COUNCIL,

 Petitioners

v.

UNITED STATES ENVIRONMENTAL PROTECTION 

AGENCY,

 Respondent

* Pennsylvania Department of Environmental Protection; 

 Homer City Generation LP,

 Intervenors

*(Pursuant to Clerk Order dated 08/21/14) 

_____________

On Petition for Review of Final Agency Action

of the United States Environmental Protection Agency

(EPA-R03-OAR-2012-0002)

______________

Argued April 14, 2015
2

______________

Before: AMBRO, VANASKIE, and SHWARTZ,

Circuit Judges

(Opinion Filed: September 29, 2015)

David S. Baron, Esq.

Earthjustice Legal Defense Fund

1625 Massachusetts Avenue, N.W.

Suite 702

Washington, DC 20036

Charles McPhedran, Esq. [ARGUED]

Earthjustice

1617 John F. Kennedy Boulevard

Suite 1675

Philadelphia, PA 19103

Counsel for Petitioners

Kate R. Bowers, Esq. [ARGUED]

United States Department of Justice

Environment and Natural Resources Division

P.O. Box 7611

Ben Franklin Station

Washington, DC 20044

Regina McCarthy, Esq.

Environmental Protection Agency

Ariel Rios Building

1200 Pennsylvania Avenue, N.W.

Washington, DC 20460

Counsel for Respondent
3

Robert A. Reiley, Esq. [ARGUED]

Kristen M. Furlan, Esq.

Pennsylvania Department of Environmental Resources

Office of Chief Counsel

9th Floor

400 Market Street

Harrisburg, PA 17101

Counsel for Intervenor Pennsylvania Department of 

Environmental Protection

Chet M. Thompson, Esq. [ARGUED]

Kirsten L. Nathanson, Esq.

Crowell & Moring

1001 Pennsylvania Avenue, N.W.

Washington, DC 20004

Counsel for Intervenor Homer City Generation LP

___________

OPINION OF THE COURT

___________

VANASKIE, Circuit Judge.

Section 169A of the Clean Air Act, 42 U.S.C. § 7491, 

and implementing regulations promulgated by the United 

States Environmental Protection Agency (“EPA”) require 

states to evaluate the impact that emissions from certain 

sources of pollution within their borders have on atmospheric 

visibility in national parks and wilderness areas. After 

conducting this evaluation, the Commonwealth of 

Pennsylvania declined to require its sources to implement

additional pollution controls because it concluded that the 
4

costs associated with the controls outweighed the limited 

visibility improvements they would produce. The 

Commonwealth’s conclusions were set forth in its 2010 State 

Implementation Plan (“SIP”), which was approved by the 

EPA in 2014.

Alleging that the EPA’s approval of Pennsylvania’s 

SIP was arbitrary and capricious, the National Parks 

Conservation Association, Sierra Club, and Clean Air Council 

(collectively, “Conservation Groups”) filed the petition for 

review presently before the Court. For the reasons that 

follow, we will grant the petition in part and deny it in part, 

and remand the matter to the EPA for further consideration.

I.

A. Statutory and Regulatory Framework

In 1970, Congress enacted the Clean Air Act, 42 

U.S.C. §§ 7401–7671q, to address the increasing amount of 

air pollution created by the industrialization of the United 

States and the resulting threat to public health and welfare. 

Employing “cooperative federalism,” the Clean Air Act gives 

both the federal government and the states responsibility for 

maintaining and improving air quality: “the federal 

government develops baseline standards that the states 

individually implement and enforce.” Bell v. Cheswick 

Generating Station, 734 F.3d 188, 190 (3d Cir. 2013)

(citation and quotation marks omitted).

As originally enacted, the Clean Air Act “did not 

elaborate on the protection of visibility as an air-quality 

related value.” Chevron U.S.A., Inc. v. EPA, 658 F.2d 271, 

272 (5th Cir. 1981) (emphasis added). In 1977, however, 
5

Congress added § 169A to the Clean Air Act “[i]n response to 

a growing awareness that visibility was rapidly deteriorating 

in many places, such as wilderness areas and national parks . . 

. .” Id. With § 169A, Congress “established as a national 

goal the ‘prevention of any future, and the remedying of any 

existing, impairment in visibility in mandatory class I areas 

which impairment results from man-made air pollution.’” 

Am. Corn Growers Ass’n v. EPA, 291 F.3d 1, 3 (D.C. Cir. 

2002) (per curiam) (quoting 42 U.S.C. § 7491(a)(1)). The 

protected “Class I areas” include certain national parks and 

wilderness areas under 42 U.S.C. § 7472(a).1 “Visibility 

impairment” means both “reduction in visual range and 

atmospheric discoloration.” Id. § 7491(g)(6).

In connection with § 169A, Congress directed the EPA

to issue regulations to ensure “reasonable progress” toward 

the national goal of restoring visibility conditions to their 

natural state in Class I areas. Id. § 7491(a)(4). Congress 

dictated that the EPA’s regulations require adoption of a State 

Implementation Plan (“SIP”) by each state that has a Class I 

area within its borders or whose emissions “may reasonably 

be anticipated to cause or contribute to any impairment of 

visibility” in any Class I area. Id. § 7491(b)(2). Each SIP 

must include, inter alia, emission limits, compliance 

 

1 There are 156 Class I areas in the United States, 

including 47 national parks, 108 wilderness areas, and one 

international park. No Class I area is located within 

Pennsylvania’s borders. 40 C.F.R. pt. 51, app. Y.; EPA, List 

of 156 Mandatory Class I Federal Areas, 

http://www.epa.gov/visibility/class1.html (last visited Aug. 

26, 2015).
6

schedules, and a long-term strategy for meeting the national

visibility goal. Id. In response to this statutory directive, the 

EPA promulgated the Regional Haze Rule in 1999. Regional 

Haze Regulations, 64 Fed. Reg. 35,714 (July 1, 1999).2 

 

2 The EPA has explained the visibility impairment 

known as “regional haze” as follows: 

Regional haze is visibility 

impairment that is produced by a 

multitude of sources and activities 

which are located across a broad 

geographic area and emit fine 

particles (PM2.5) (e.g., sulfates, 

nitrates, organic carbon, elemental 

carbon, and soil dust) and their 

precursors (e.g., sulfur dioxide 

(SO2), nitrogen oxides (NOX), and 

in some cases, ammonia (NH3) 

and volatile organic compounds 

(VOC)). Fine particle precursors 

react in the atmosphere to form 

fine particulate matter, which 

impairs visibility by scattering 

and absorbing light. Visibility 

impairment reduces the clarity, 

color, and visible distance that 

one can see. PM2.5 can also cause 

serious health effects and 

mortality in humans and 

contributes to environmental 
7

Section 169A and the Regional Haze Rule also require

each SIP to include a determination of the best available 

retrofit technology (“BART”) for certain major stationary 

sources of pollution that are reasonably anticipated to cause 

or contribute to visibility impairment in any Class I area. 

North Dakota v. EPA, 730 F.3d 750, 756 (8th Cir. 2013) 

(citing 42 U.S.C. § 7491(b)(2)(A); 40 C.F.R. §§ 51.301, 

51.308(e)). BART is defined as “an emission limitation 

based on the degree of reduction achievable through the 

application of the best system of continuous emission

reduction for each pollutant which is emitted by an existing 

stationary facility.” 40 C.F.R. § 51.301. 

To satisfy the BART requirements, a state’s SIP must

first identify all “BART-eligible” sources within its borders. 

Under the regulations, a stationary source of air pollution is 

BART-eligible if it: (1) was in existence on August 7, 1977, 

but not in operation prior to August 7, 1962; (2) fits within 

one of 26 identified categories; and (3) has the potential to 

emit annually at least 250 tons of any air pollutant. Id.

Next, a state’s SIP must determine which of these 

BART-eligible sources are “subject to BART.” A source is 

subject to BART if it “emits any air pollutant which may 

 

effects such as acid deposition 

and eutrophication.

Approval and Promulgation of Air Quality Implementation 

Plans; Commonwealth of Pennsylvania; Regional Haze State 

Implementation Plan, 77 Fed. Reg. 3,984, 3,985 (Jan. 26, 

2012).
8

reasonably be anticipated to cause or contribute to any 

impairment of visibility in any mandatory Class I Federal 

area.” Id. § 51.308(e)(1)(ii) (emphasis added). The EPA

recommends that a state consider a source to “cause”

visibility impairment if it is responsible for a change in 

visibility in a Class I area of at least 1.0 deciview.

3

 Regional 

Haze Regulations and Guidelines for Best Available Retrofit 

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

39,118 (July 6, 2005). The suggested threshold for 

determining whether a source “contributes” to visibility 

impairment at a level no higher than 0.5 deciviews. Id.

For each BART-eligible source that is subject to 

BART, the state must conduct a source-specific analysis to 

determine appropriate emission limitations. In so doing, 

states “weigh[] the following five factors: (1) ‘the costs of 

compliance’; (2) ‘the energy and non[-]air quality 

environmental impacts of compliance’; (3) ‘any existing 

pollution control technology in use at the source’; (4) ‘the 

remaining useful life of the source’; and (5) ‘the degree of 

improvement in visibility which may reasonably be 

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

 

3 Changes in visibility are expressed in a standard unit 

of measurement known as the deciview. See 40 C.F.R. § 

51.301 (stating that the deciview is “a measurement of 

visibility impairment” that is “derived from calculated light 

extinction, such that uniform changes in haziness correspond 

to uniform incremental changes in perception across the 

entire range of conditions, from pristine to highly impaired”). 

A higher deciview value corresponds with a greater level of 

visibility impairment.
9

WildEarth Guardians v. EPA, 759 F.3d 1064, 1068 (9th Cir. 

2014) (quoting 42 U.S.C. § 7491(g)(2); 40 C.F.R. pt. 51, app. 

Y). 

To aid states in identifying BART-eligible sources and 

determining appropriate emission limitations, the EPA issued 

the BART Guidelines, 70 Fed. Reg. 39,156. WildEarth 

Guardians, 759 F.3d at 1068. The Guidelines, issued in 

2005, provide states with a five-step process for making their 

source-specific BART determinations, and these five steps 

subsume the statutory considerations listed above. Id. at 

1068–69 (citing 70 Fed. Reg. 39,127). Under the Guidelines, 

a state is to first identify all available retrofit control

technologies. Second, technically infeasible options are 

eliminated. Third, the effectiveness of the remaining control 

techniques is assessed. Fourth, the impacts, including the

cost of compliance, energy impacts, non-air quality impacts, 

and the remaining useful life of the facility, are evaluated. 

Finally, a state must estimate the visibility impacts at Class I 

areas. Id. at 1069 (citing 70 Fed. Reg. 39,164, 39,166). 

While states are required to use the Guidelines when making 

BART determinations for any fossil fuel-fired power plant

with a total electricity generating capacity of 750 megawatts

or more, the Guidelines are advisory for smaller BARTeligible sources. Id. (citing 42 U.S.C. § 7491(b)(2)(B); 40 

C.F.R. § 51.308(e)(1)(ii)(B)).

As an alternative to conducting this source-specific

analysis, states may instead implement another program if 

they can demonstrate it is “better-than-BART” at reducing 

emissions. Specifically, the regional haze regulations permit 

a state to “opt to implement or require participation in an 

emissions trading program or other alternative measure” if it

can show that the program would result in “greater reasonable 
10

progress” toward the national goal of restoring natural 

visibility “than would be achieved through the installation 

and operation of BART.” 40 C.F.R. § 51.308(e)(2). States 

participating in such programs do not have to conduct a 

source-specific BART analysis or compel pollution sources 

within their borders to install, operate, and maintain BART at 

their facilities. Id.

Regardless of whether a state conducts the sourcespecific BART analysis or follows the better-than-BART 

approach, it must ultimately submit its SIP to the EPA. The 

EPA, in turn, must review the SIP and determine whether it 

meets the requirements of the Clean Air Act. 42 U.S.C. § 

7410(a)(1). The EPA is required to approve a SIP as a whole 

if it meets all the statutory requirements, and it may approve 

any portion of a SIP that meets the requirements. Id. at § 

7410(k)(3). If a state fails to submit a SIP, submits an 

incomplete SIP, or submits a SIP that does not meet the 

statutory requirements, the EPA must enact its own Federal 

Implementation Plan (“FIP”), unless the state can provide a 

SIP that the EPA can approve within two years. North 

Dakota, 730 F.3d at 757 (citing 42 U.S.C. § 7410(c)).

B. Procedural Background

Pennsylvania submitted its regional haze SIP to the 

EPA in December 2010, identifying 34 BART-eligible 

sources of pollution within its borders. App. 43–171. These 

pollution sources—various power plants, mills, refineries, and 

other facilities around the state—emit visibility-impairing 

particulate matter (“PM”) into the atmosphere, as well as the 

chemical precursors to PM, which include sulfur dioxide 

(“SO2”) and oxides of nitrogen (“NOx”). Pennsylvania 

elected to treat each of these 34 BART-eligible sources as 
11

subject to BART,

4

and it opted to follow the five-step process 

outlined in the Guidelines for making source-specific BART 

determinations.5 Pennsylvania, however, chose to follow the 

better-than-BART approach with respect to the eight fossil 

fuel electric generating stations with a capacity of 750 

megawatts or more.

Thus, Pennsylvania conducted a source-specific BART 

analysis regarding the SO2 and NOx emissions of each source

with an electricity generating capacity below 750 megawatts, 

but did not do so for the fossil fuel electric generating stations 

having a capacity of 750 megawatts or more. Pennsylvania

noted that these sources participated in the “cap and trade” 

program6for SO2 and NOx emissions established by EPA

 

4 This practice ensures that a BART analysis is 

conducted for every BART-eligible source, even if the 

deciview impact from the source is not high enough that the 

source would be considered to “cause” or “contribute” to 

visibility impairment in any Class I area under 40 C.F.R. § 

51.308(e)(1)(ii).

5 Pennsylvania was obligated to follow the Guidelines 

for each of the eight fossil fuel-fired power plants in the state 

that have electricity generating capacity of at least 750 

megawatts, but the Guidelines were advisory for the 

remaining BART-eligible sources. See 42 U.S.C. § 

7491(b)(2)(B); 40 C.F.R. § 51.308(e)(1)(ii)(B).

6 A cap and trade program is an environmental policy 

tool that involves setting a mandatory cap on emissions while 

providing pollution sources with flexibility as to how they 
12

Clean Air Interstate Rule (“CAIR”), 70 Fed. Reg. 25,162 

(May 12, 2005), and concluded that the sources’ participation 

in the cap and trade program was better than BART at 

reducing such emissions.

Ultimately, Pennsylvania’s SIP found that requiring 

additional emission controls at any of the 34 BART-eligible 

sources would result in only minimal visibility improvement

in affected Class I areas. Weighing this minimal 

improvement against the cost of implementing the controls, 

Pennsylvania concluded that additional controls were not 

warranted.

In January 2012, the EPA issued a proposed rule

providing for a limited approval of Pennsylvania’s SIP

(“2012 Proposed Rule”). Approval and Promulgation of Air 

Quality Implementation Plans; Commonwealth of 

Pennsylvania; Regional Haze State Implementation Plan, 77

Fed. Reg. 3,984 (Jan. 26, 2012). The EPA concluded that 

Pennsylvania’s BART analysis complied with the statutory 

requirements of the Clean Air Act and the regional haze 

regulations. However, the EPA declined to address 

Pennsylvania’s reliance on the better-than-BART CAIR 

program regarding SO2 and NOx emissions for certain

pollution sources, noting that particular issue was the subject 

of a separate rulemaking proceeding. The EPA also 

announced a one-month period for interested parties to 

comment on the 2012 Proposed Rule.

 

comply with the cap. See EPA, Cap and Trade, 

http://www.epa.gov/captrade (last visited Aug. 26, 2015).
13

On June 7, 2012, the EPA issued its final rule (the 

“National Rule”) in the separate proceeding referenced by the 

2012 Proposed Rule, disapproving the SIPs submitted by

Pennsylvania and 14 other states to the extent they relied on 

the CAIR program to limit SO2 and NOx emissions. Regional 

Haze: Revisions to Provisions Governing Alternatives to 

Source-Specific Best Available Retrofit Technology (BART) 

Determinations, Limited SIP Disapprovals, and Federal 

Implementation Plans, 77 Fed. Reg. 33,642 (June 7, 2012). 

With this disapproval, the EPA also promulgated FIPs for 13 

of the states (including Pennsylvania), effectively replacing 

the states’ reliance on the CAIR program with reliance on the 

newly promulgated Cross-State Air Pollution Rule, better 

known as the Transport Rule. By issuing the National Rule, 

the EPA also finalized its conclusion that the Transport Rule 

was better-than-BART at reducing SO2 and NOx emissions, 

and that it addressed the shortcomings of the CAIR program 

previously identified by the United States Court of Appeals 

for the District of Columbia Circuit.7

 

7 The EPA initially promulgated CAIR in 2005, but the 

D.C. Circuit vacated the rule in 2008, noting multiple fatal 

flaws not pertinent to the present case. North Carolina v. 

EPA, 531 F.3d 896, 921 (D.C. Cir. 2008) (per curiam). On 

rehearing, the D.C. Circuit elected to leave CAIR in place 

while the EPA crafted a new program to address CAIR’s 

deficiencies. North Carolina v. EPA, 550 F.3d 1176, 1178 

(D.C. Cir. 2008) (per curiam). EPA responded by 

promulgating the Transfer Rule. The D.C. Circuit vacated 

this rule in 2012, EME Homer City Generation, L.P. v. EPA, 

696 F.3d 7, 37 (D.C. Cir. 2012), but the Supreme Court later 
14

Shortly thereafter, on July 13, 2012, the EPA finalized 

its limited approval of Pennsylvania’s SIP. Approval and 

Promulgation of Air Quality Implementation Plans; 

Pennsylvania; Regional Haze State Implementation Plan, 77 

Fed. Reg. 41,279 (July 13, 2012). With this “2012 Final 

Rule,” the EPA responded to comments regarding the 2012 

Proposed Rule and reaffirmed its conclusion that 

Pennsylvania’s BART analysis was proper.

In response to the 2012 Final Rule, the Conservation 

Groups filed a petition for review with this Court, challenging 

the rule on a number of fronts. Nat’l Parks Conservation 

Assoc. v. EPA, No. 12-3534. We did not reach the merits of 

the petition, though, since the EPA filed a motion for 

voluntary remand without vacatur in order to consider and 

respond in greater detail to the Conservation Groups’ 

concerns. We granted the motion on October 22, 2013, and 

remanded the matter to the EPA.

Following remand, the EPA entered a final rule on 

April 30, 2014 (“2014 Final Rule”), reissuing its limited 

approval of Pennsylvania’s SIP. Approval and Promulgation 

of Air Quality Implementation Plans; Pennsylvania; Regional 

Haze State Implementation Plan, 79 Fed. Reg. 24,340 (Apr.

30, 2014). With this rule, the EPA expanded its responses to 

certain comments and acknowledged numerous deficiencies 

in Pennsylvania’s source-specific BART analysis. In the end, 

however, the EPA approved the SIP, finding that 

 

overturned the decision, upheld the Transport Rule, and 

remanded for further proceedings. EPA v. EME Homer City 

Generation, L.P., 134 S. Ct. 1584, 1609–10 (2014).
15

Pennsylvania reasonably concluded that no additional 

pollution controls were required at the 34 BART-eligible 

sources given the low visibility impact of the sources in Class 

I areas and the high cost of implementing the controls. 

This petition for review followed, with the 

Conservation Groups alleging that the EPA arbitrarily and 

capriciously approved Pennsylvania’s SIP. We subsequently 

granted motions to intervene filed by the Pennsylvania 

Department of Environmental Protection (the state agency 

responsible for drafting Pennsylvania’s SIP) and Homer City 

Generation, L.P., a coal-fired power plant in Indiana County, 

Pennsylvania.

II.

Under § 307(b)(1) of the Clean Air Act, we have 

jurisdiction to review a final EPA action that is “locally or 

regionally applicable” within our Circuit. 42 U.S.C. § 

7607(b)(1); GenOn REMA, LLC v. EPA, 722 F.3d 513, 519 

(3d Cir. 2013). However, a petition for review regarding any 

“nationally applicable regulations promulgated, or final action 

taken, by the Administrator [of the EPA] . . . may be filed 

only in the United States Court of Appeals for the District of 

Columbia.” 42 U.S.C. § 7607(b)(1) (emphasis added).

When reviewing a final EPA action, we must 

“determine whether it is ‘arbitrary, capricious, an abuse of 

discretion, or otherwise not in accordance with the law.’” 

GenOn REMA, 722 F.3d at 525 (quoting 42 U.S.C. § 

7607(d)(9)(A)). While this is a narrow and deferential 

standard of review, Motor Vehicle Mfrs. Ass’n v. State Farm 

Mut. Auto. Ins. Co., 463 U.S. 29, 43 (1983), we must 

nevertheless ensure that the EPA “examined the relevant data 
16

and articulated a satisfactory explanation for its action, 

including a rational connection between the facts found and 

the choice made.” Prometheus Radio Project v. FCC, 373 

F.3d 372, 389–90 (3d Cir. 2004) (citation and quotation 

marks omitted).

III.

A. Transport Rule

The Conservation Groups challenge the EPA’s

decision to allow Pennsylvania to rely on the Transport Rule 

in lieu of conducting a source-specific BART analysis 

regarding SO2 and NOx emissions from each source with an 

electricity generating capacity of at least 750 megawatts. In 

particular, they argue that the Transport Rule is not betterthan-BART at reducing SO2 and NOx emissions, has not been 

implemented as the EPA assumed it would be when it 

permitted Pennsylvania to rely on the rule, and is subject to 

further delays and legal challenges. 

The EPA counters that this appeal is not the 

appropriate vehicle to challenge its finding that the Transport 

Rule is better-than-BART or its decision to approve states’

reliance on this rule, as both these determinations stem from a

final rule and separate rulemaking proceeding not presently 

before this Court. Moreover, the EPA argues that under 42 

U.S.C. § 7607(b)(1), the Conservation Groups must pursue 

any such challenge in the D.C. Circuit. We agree with the 

EPA on both points.

Following extensive administrative proceedings, the 

EPA issued its National Rule on June 7, 2012. 77 Fed. Reg. 

33,642. With it, the EPA finalized the emissions-limiting 
17

Transport Rule, a replacement to the CAIR program that had 

been invalidated by the D.C. Circuit in North Carolina v. 

EPA, 531 F.3d 896, 921 (D.C. Cir. 2008) (per curiam). The 

National Rule included the finding that the emission trading 

programs established by the Transport Rule are better-thanBART. 77 Fed. Reg. 33,643 (“In this action, the EPA is 

finalizing our finding that the trading programs in the 

Transport Rule . . . achieve greater reasonable progress 

towards the national goal of achieving natural visibility 

conditions in Class I areas than source-specific . . . (BART) in 

those states covered by the Transport Rule.”). The EPA also

finalized its disapproval of the SIPs submitted by 

Pennsylvania and 14 other states to the extent they relied on 

the CAIR program to limit SO2 and NOx emissions, and 

promulgated FIPs for 13 states (including Pennsylvania), 

effectively replacing the states’ reliance on the CAIR 

program with reliance on the newly promulgated Transfer 

Rule. Id. 

By contrast, the 2014 Final Rule, which the 

Conservation Groups challenge here, does not address the 

merits of the Transport Rule or Pennsylvania’s reliance on it. 

Instead, it notes those issues were addressed in a “separate but 

related action,” referring to the National Rule. See 79 Fed. 

Reg. 24,340–41. Prior to issuing the 2014 Final Rule, the 

EPA repeatedly explained that the propriety of the Transport 

Rule, the CAIR program, and Pennsylvania’s reliance on the 

Transport Rule or the CAIR program were beyond the scope 

of these rulemaking proceedings. See, e.g., 2012 Final Rule, 

77 Fed. Reg. 41,282 (“Comments related to [the Transport 

Rule] as an alternative to BART for [electricity generating 

units] are beyond the scope of this rulemaking. The EPA

addressed similar comments concerning the Transport Rule as 
18

a BART alternative in [the National Rule].”); 2012 Proposed 

Rule, 77 Fed. Reg. 3,984 (“[W]e are not taking action in this 

notice to address the Commonwealth’s reliance on CAIR to 

meet certain regional haze requirements.”).

In short, the Conservation Groups seek to use this 

appeal from the administrative proceedings that culminated in 

the 2014 Final Rule to challenge decisions the EPA reached 

in separate proceedings. We find no support for this approach 

in the text of the Clean Air Act provision authorizing judicial 

review of EPA actions. See 42 U.S.C. § 7607(b)(1). 

Additionally, as the administrative record upon which these 

decisions were made is not before us, we lack the information 

necessary to evaluate the EPA’s action regarding the 

Transport Rule. See Fed. Power Comm’n v. Transcontinental 

Gas Pipe Line Corp., 423 U.S. 326, 331 (1976) (stating that 

“we have consistently expressed the view that ordinarily 

review of administrative decisions is to be confined to 

consideration of the decision of the agency . . . and of the 

evidence on which it is based”) (citation and quotation marks 

omitted). Accordingly, we cannot entertain the Conservation 

Groups’ challenge to the Transport Rule.

Moreover, even if the Conservation Groups could use 

this appeal to challenge the Transport Rule, we are not the 

proper court to hear the challenge. Under 42 U.S.C. § 

7607(b)(1), petitions for review of “nationally applicable 

regulations promulgated, or final action taken, by the 

Administrator [of the EPA] . . . may be filed only in the [D.C. 

Circuit].” Id. (emphasis added). We conclude that the EPA’s

National Rule, which finalized the Transport Rule (applicable 

to 28 states and the District of Columbia) and resulted in 13 

FIPs permitting various states to rely on the Transport Rule, 

falls into this category. See Texas v. EPA, No. 10-60961, 
19

2011 WL 710598, at *5 (5th Cir. Feb. 24, 2011) 

(unpublished) (“Our conclusion today—that an EPA action 

involving the SIPs of numerous far-flung states is ‘nationally 

applicable’ and thus reviewable only in the D.C. Circuit—is 

consistent with the holdings of our sister circuits to have 

considered the question.”); W. Va. Chamber of Commerce v. 

Browner, No. 98-1013, 1998 WL 827315, at *4 (4th Cir. Dec. 

1, 1998) (unpublished) (“An EPA rule need not span ‘from 

sea to shining sea’ to be nationally applicable.”) (footnote 

omitted); Puerto Rican Cement Co. v. EPA, 889 F.2d 292, 

299–300 (1st Cir. 1989) (finding EPA regulations to be 

“nationally applicable” where they applied to any SIP “that 

ha[d] been disapproved with respect to prevention of 

significant deterioration of air quality in any portion of any 

State where the existing air quality is better than the national 

ambient air quality standards,” and the list of states governed 

by the regulations changed as SIPs were approved and 

disapproved by the EPA).8

Accordingly, we will deny the Conservation Groups’ 

petition for review to the extent it challenges the Transport

Rule or Pennsylvania’s reliance on it.

 

8 What’s more, even the Conservation Groups appear 

to recognize that their challenge to the Transport Rule should 

be heard by the D.C. Circuit: the National Parks Conservation 

Association and Sierra Club are participants in consolidated 

appeals challenging the Transport Rule that are currently 

pending before the D.C. Circuit. See Util. Air Regulatory 

Grp. v. EPA, No. 12-1342 (D.C. Cir.).
20

B. Source-Specific BART Analysis

The Conservation Groups also contend that 

Pennsylvania’s source-specific BART analysis failed to 

comply with the Guidelines in many respects, and that the 

EPA violated the Clean Air Act by arbitrarily approving 

Pennsylvania’s SIP despite these fatal flaws. The EPA

counters that Pennsylvania’s analysis was largely proper, and 

that the errors it committed did not affect the reasonableness 

of the state’s decision not to require its BART-eligible 

sources to implement additional pollution controls. In what 

resembles a harmless-error argument, the EPA asserts that,

despite Pennsylvania’s flawed analysis, the resulting overall 

picture supported its ultimate decision. As discussed below, 

while we reject some of the arguments advanced by the 

Conservation Groups, we are nevertheless compelled to 

conclude that the EPA arbitrarily approved Pennsylvania’s 

SIP given the multiple flaws in Pennsylvania’s BART 

analysis and the EPA’s insufficient explanation as to why it 

could overlook them.

1. Identification of All Available Retrofit Control 

Technologies

The Conservation Groups contend that Pennsylvania 

failed to satisfy the BART requirement of identifying all 

available pollution control technologies. In particular, they 

argue that the state did not consider upgrades to existing 

electrostatic precipitator (“ESP”) control technologies for 

BART-eligible power plants within the state, or other 

available combinations of controls. 

The EPA counters that Pennsylvania’s SIP notes that 

ESP upgrades were considered for all but two power plants, 
21

and that Pennsylvania had declined to consider upgrades at 

those two facilities because they had recently installed “stateof-the-art” ESP controls. The EPA also argues that 

Pennsylvania did consider combinations of controls, 

including fabric filters on sources where technically feasible.

While we agree with the EPA that Pennsylvania’s SIP 

states that upgrades and combinations were considered, we 

cannot discern from the administrative record the specifics of

Pennsylvania’s analysis or why it rejected certain upgrades or 

combinations. As the Conservation Groups noted in their 

comments to the 2012 Final Rule, App. 487, Pennsylvania’s 

SIP states in conclusory fashion that ESP upgrades, 

enhancements, or replacements were considered for certain 

sources. See, e.g., App. 221 (stating that “[t]he retrofit 

technologies reviewed” during the course of the BART 

analysis for the Mitchell Power Station “included fuel-related 

modifications, ESP upgrades, enhancements or replacement, 

replacement of the ESPs with fabric filters or compact hybrid 

particulate collectors”). What the SIP fails to do, however, is 

identify or describe the upgrades considered or explain why 

these controls were rejected. Similarly, the EPA has failed to 

explain—either in the 2014 Final Rule or now on appeal—

how it could meaningfully evaluate Pennsylvania’s analysis 

described in such conclusory fashion. We acknowledge that 

EPA and BART regulations do not require exhaustive 

analysis of every conceivable emissions control. See 40 

C.F.R. pt. 51, app. Y § IV.D. n.12 (explaining that “[i]t is not 

necessary to list all permutations of available control levels 

that exist for a given technology”). Nonetheless, the EPA has 

failed to satisfactorily explain why the SIP’s conclusory 

listings are acceptable.

2. Baseline Level for PM Emissions
22

The Conservation Groups next challenge 

Pennsylvania’s source-specific BART analysis regarding PM 

emissions from 13 power plants. Specifically, they contend 

the state improperly concluded that the filterable emission 

limit of 0.1 pound of particulate matter per million British 

thermal units (“0.1 lb/MMBtu”) represents BART for those 

facilities.9 The Conservation Groups argue the limit is not 

sufficiently stringent, and note that lower limits (between 

0.07 lb/MMBtu and 0.012 lb/MMBtu) have qualified as 

BART at other facilities. In short, they assert that 

Pennsylvania had no reasoned basis for selecting the emission 

limit that it did, and that the EPA arbitrarily approved 

Pennsylvania’s BART analysis regarding PM emissions 

predicated on this threshold.

In the 2014 Final Rule, the EPA concedes that 

Pennsylvania failed to determine whether the 0.1 lb/MMBtu 

emission limit actually represents BART for those facilities. 

See 79 Fed. Reg. 24,344 (“Here, Pennsylvania determined 

that PM BART for most of the subject-to-BART [electricity 

generating units] was their existing permitted emission limits 

 

9 After a state has identified the best available control 

technology for reducing emissions at a particular source, it 

must then set an “emission limit.” This limit represents the 

emission-reduction capabilities of the identified control 

technology. See 2014 Final Rule, 79 Fed. Reg. 24,344 

(stating that “once a state has selected a control technology 

that represents BART, the state must then complete the 

BART analysis by selecting an emission limit that represents 

the emission-reduction capabilities of that control 

technology”). 
23

of 0.1 lb/MMBtu, which can be achieved by the existing 

[control technology]. While the EPA agrees with the 

commenter that Pennsylvania ideally should have examined 

whether 0.1 lb/MMBtu actually reflects the ‘degree of 

reduction achievable’ for the particular [control technology] 

at each facility, EPA thinks that Pennsylvania’s failure to do 

so was not fatal in this instance . . . .”) (footnote omitted). 

The EPA excuses this failure for two reasons. First, it argues

that Pennsylvania’s error was essentially harmless, as 

imposing a stricter PM emission limit on these sources would 

have minimal visibility impact in Class I areas since the PM 

emissions from these sources were responsible for only a 

minimal portion of the visibility impairment in these areas. 

Second, the EPA claims that the issue is “largely moot[].” Id.

at 24,345. Specifically, the agency notes that many of these 

13 power plants have retired or put in motion plans to retire 

or convert to cleaner burning fuels since Pennsylvania 

conducted its BART determinations. The EPA also notes that 

the remaining sources will have to comply with a more 

stringent PM emission limit of 0.03 lb/MMBtu by 2015 due 

to the implementation of the Mercury and Air Toxics

Standards (“MATS”) Rule. Id. at 24,344.

We find the EPA’s arguments unconvincing. As 

discussed in greater detail infra, Part III.B.7, the EPA’s claim 

of harmless error is unpersuasive since the agency has offered 

scant justification for this position, apart from its own 

assurances that the multiple flaws in Pennsylvania’s analysis 

did not impact the reasonableness of its conclusions. 

Similarly, the EPA has not identified, nor have we located, 

any legal support for the EPA’s contention that it may excuse

errors in a state’s BART analysis as moot based on events 

that are yet to transpire. To the contrary, the EPA has a 
24

statutory obligation to disapprove a SIP that does not comply

with the Clean Air Act and to promulgate a FIP if the 

deficiencies are not timely cured. See 42 U.S.C. § 7410(k) 

(requiring the EPA to review SIPs to ensure compliance); id. 

§ 7410(l) (prohibiting the EPA from approving a revision to a 

SIP if it would interfere with any applicable requirement of 

the Clean Air Act).

3. Alternative Pollution Control Limits: BACT, 

LAER, and MACT

The Conservation Groups also contend Pennsylvania’s 

BART analysis regarding PM emissions did not comply with 

the Guidelines because the state did not consider more 

stringent emission limits developed as part of separate air 

quality permitting processes under the Clean Air Act. In 

particular, they argue that limits imposed by other 

programs—known as best available control technology 

(“BACT”), lowest achievable emission rate (“LAER”), and 

maximum achievable control technology (“MACT”)—are

relevant to the BART analysis because they demonstrate 

achievable emission reductions.10

 

10 BACT is “an emission limitation based on the 

maximum degree of reduction of each pollutant . . . which the 

permitting authority, on a case-by-case-basis, taking into 

account energy, environmental, and economic impacts and 

other costs, determines is achievable for [the] facility . . . .” 

42 U.S.C. § 7479(3). Under the Clean Air Act’s Prevention 

of Significant Deterioration program, no new major air 

pollutant emitting facility may be constructed unless the 

facility is equipped with BACT. Alaska Dep’t of Envtl. 
25

In response, the EPA notes that the BART Guidelines 

do not require states to consider the exact emission limits

determined to be BACT and LAER. Instead, they must 

consider the technologies used to achieve BACT and LAER

when conducting the first step of the BART analysis: 

identifying all available control technologies for their 

pollution sources. See BART Guidelines, 40 C.F.R. pt. 51, 

app. Y (“Technologies required as BACT or LAER are 

available for BART purposes and must be included as control 

alternatives.”) (emphasis added). Moreover, the EPA notes 

that the stringent emission levels determined to be BACT or 

LAER are not necessarily achievable by BART-eligible 

sources because those programs apply to new and newly 

 

Conservation v. EPA, 540 U.S. 461, 468 (2004). In 

“nonattainment areas”—areas that are not in attainment with 

the Clean Air Act’s National Ambient Air Quality 

Standards—new and modified pollution sources are required 

to install LAER, which is more stringent than BACT. See 

Citizens Against Ruining the Env’t v. EPA, 535 F.3d 670, 673 

n.3 (7th Cir. 2008). Under the Clean Air Act’s National 

Emission Standards for Hazardous Air Pollutants program, 

the EPA imposes MACT on major sources of certain 

hazardous air pollutants. MACT “must reflect ‘the maximum 

degree of reduction in emissions’ that the EPA determines is 

‘achievable,’ taking into consideration ‘the cost of achieving 

such emission reduction, and any non-air quality health and 

environmental impacts and energy requirements.’” Nat’l Res. 

Def. Council v. EPA, 749 F.3d 1055, 1057 (D.C. Cir. 2014) 

(quoting 42 U.S.C. § 7412(d)(2)).
26

modified sources, while BART governs pollution sources 

constructed before 1977.

The EPA also notes that, for sources of PM emissions

that are subject to MACT standards, the BART Guidelines

permit—but do not require—states to rely on the stringent 

MACT standards for purposes of BART. In other words, the 

Guidelines create a presumption that a state’s reliance on the 

MACT standards satisfies BART, but they do not require the 

state to rely on the MACT standard to satisfy BART. See

BART Guidelines, 40 C.F.R. pt. 51, app. Y (“We believe that, 

in many cases, it will be unlikely that States will identify 

emission controls more stringent than the MACT standards 

without identifying control options that would cost many 

thousands of dollars per ton. Unless there are new 

technologies subsequent to [issuance of] the MACT standards 

which would lead to cost-effective increases in the level of 

control, you may rely on the MACT standards for purposes of 

BART.”).

We agree with the EPA’s reading of the BART 

Guidelines on these points. As a result, we reject the 

Conservation Groups’ contention that Pennsylvania 

improperly failed to consider BACT, LAER, and MACT

emission limitations.

4. Cost-Effectiveness Threshold

The Conservation Groups argue that Pennsylvania 

failed to properly evaluate the cost-effectiveness of the 

pollution controls available for each BART-eligible source. 

In particular, they note that Pennsylvania did not set a 

“threshold” for cost-effectiveness—that is, an amount of 

money at which it would reject any available control option 
27

as too expensive. Absent such a threshold, the Conservation 

Groups contend, Pennsylvania had no principled way of 

determining when a pollution control was a cost-effective 

method of improving visibility in affected Class I areas.

The EPA asserts that nothing in the Clean Air Act 

requires Pennsylvania to set a fixed threshold of costeffectiveness, and that the Guidelines make no mention of 

such a threshold in their instructions on how to evaluate costeffectiveness. See BART Guidelines, 40 C.F.R. pt. 51, app. 

Y; Nat’l Parks Conservation Ass’n v. EPA, 788 F.3d 1134,

1142 (9th Cir. 2015) (“To be sure, the Act and the 

Regulations do not specifically require that EPA explain its 

cost-effectiveness decisions through use of a ‘bright line’ 

rule.”). Instead of drawing a line in the sand on costeffectiveness, the EPA notes that Pennsylvania’s SIP

appropriately determined that pollution “sources with a higher 

degree of potential visibility improvement from control would 

justify higher cost controls,” and that “only low cost controls 

would be justified for sources with a lower degree of potential 

visibility improvement.” App. 100. 

Because we agree that Pennsylvania was not 

compelled to set a threshold for cost-effectiveness, we 

conclude that the EPA did not act arbitrarily by approving 

Pennsylvania’s SIP absent such a threshold.

5. Cost-Effectiveness Metric

The Conservation Groups also assert that Pennsylvania 

used an improper metric when calculating the costeffectiveness of additional pollution controls. Specifically, 

they argue that Pennsylvania evaluated the cost of controls 

based on the dollars-per-deciview metric rather than the 
28

dollars-per-ton metric required by the Guidelines.11 The 

Conservation Groups contend that Pennsylvania’s use of the 

dollars-per-deciview metric distorted the true cost of pollution 

controls and led to the state’s conclusion that additional 

pollution controls were not warranted at any of the BARTeligible sources.

In responding to this argument during the notice-andcomment period and now on appeal, the EPA has taken 

seemingly inconsistent positions. In the text of the 2014 Final 

Rule, the EPA states, without elaboration, that Pennsylvania’s 

use of the dollars-per-deciview metric was “flawed.” 2014 

Final Rule, 79 Fed. Reg. 24,342 (stating that “EPA agrees 

with the commenters that Pennsylvania’s reliance on the 

[dollars-per-deciview] metric was flawed for multiple 

reasons”). On appeal, however, the EPA responds that 

the Guidelines specify that cost-effectiveness calculations be 

expressed in terms of dollars-per-ton, but they do not forbid 

the consideration of the dollars-per-deciview metric as well.

12

 

 

11 As its name implies, the dollars-per-ton metric is a 

measurement of the costs associated with removing a ton of a 

particular pollutant from a source’s emission. The dollarsper-deciview metric, by contrast, considers the costs 

associated with pollution reduction that would result in a 1.0 

deciview visibility improvement. The dollars-per-ton metric 

is frequently abbreviated as “$/ton,” while the dollars-perdeciview metric is abbreviated as “$/dv.”

12 As the Tenth Circuit has noted, the Guidelines 

“permit the BART-determining authority to use dollar per 

deciview as an optional method of evaluating cost 

effectiveness.” Oklahoma v. EPA, 723 F.3d 1201, 1221 (10th 
29

 

Cir. 2013) (citing 40 C.F.R. pt. 51, app. Y(IV)(E)(1)). As to 

the issue of whether states are required to use the dollars-perton metric in evaluating cost-effectiveness, however, “[t]he 

guidelines themselves are a bit unclear.” Id. at 1221 n.13. 

The Tenth Circuit explains:

In the section on cost 

effectiveness, the guidelines 

mention only the dollar-per-ton 

metric. 40 C.F.R. pt. 51 app. 

Y(IV)(D)(4)(c). However, the 

guidelines later state that, in 

evaluating alternatives, “we 

recommend you develop a chart 

(or charts) displaying for each of 

the alternatives” that includes, 

among other factors, the cost of 

compliance defined as 

“compliance—total annualized 

costs ($), cost effectiveness 

($/ton), and incremental cost 

effectiveness ($/ton), and/or any 

other cost-effectiveness measures 

(such as $/deciview).” Id. app. 

Y(IV)(E)(1) (emphasis added).

Id.
30

The EPA also notes that Pennsylvania considered both 

metrics with respect to 33 of its 34 BART-eligible sources. 

Resp. Br. 46.

Our review of the EPA’s decision is limited to the 

reasoning supplied in its final rule, not the justifications 

subsequently crafted and proffered by the agency’s appellate 

counsel. See Motor Vehicle Mfrs. Ass’n, 463 U.S. at 50 (“It is 

well-established that an agency’s action must be upheld, if at 

all, on the basis articulated by the agency itself.”) (citations 

omitted); Safe Air for Everyone v. EPA, 488 F.3d 1088, 1091

(9th Cir. 2007) (stating that “our review of an administrative 

agency’s decision begins and ends with the reasoning that the 

agency relied upon in making that decision”). As a result, we 

are left with the EPA’s conclusion that Pennsylvania’s use of 

the dollars-per-deciview metric is “flawed” in multiple

unidentified respects and no meaningful explanation as to 

why the EPA ignored these flaws. This rationale is 

insufficient to justify the EPA’s approval of Pennsylvania’s 

analysis of cost-effectiveness.

6. Cumulative Visibility Impact

As part of its source-specific BART analysis, 

Pennsylvania was required to calculate the visibility 

improvement that could be achieved in Class I areas by 

implementing additional pollution controls at its BARTeligible sources. The state’s calculations for each source, 

however, took into account only the potential impact such 

controls would have on the visibility in the Class I area most 

severely impacted by the source. Pennsylvania did not 

consider the “cumulative visibility impact”—that is, it did not 

calculate the total visibility improvement for all affected 

Class I areas that would result from installing additional 
31

controls at each source. As a result, the Conservation Groups 

argue, Pennsylvania underestimated the visibility impact of 

each source and, correspondingly, underestimated the costeffectiveness of additional control technologies. 

In the 2014 Final Rule, the EPA admits that 

Pennsylvania should have calculated the cumulative visibility 

impact from its sources. 79 Fed. Reg. 24,342 (“EPA also 

agrees with the commenters that, in considering the visibility 

improvement expected from the use of controls, Pennsylvania 

should have taken into account the visibility impacts at all 

impacted Class I areas rather than focusing solely on the 

benefits at the most impacted area.”). The EPA contends this 

error, among others, was harmless, a contention we address 

below.

7. Harmless Error

To justify its approval of Pennsylvania’s admittedly 

flawed BART analysis, the EPA advances a harmless error 

argument. In particular, the EPA contends it reasonably 

approved Pennsylvania’s conclusion that pollution controls 

were not warranted as the overall picture that emerged from 

the state’s analysis demonstrated that the improvement in 

visibility at affected Class I areas as a result of the controls 

would be minimal. Based on the administrative record before 

us, however, that conclusion is a bridge too far.

In the 2014 Final Rule, the EPA concedes that 

Pennsylvania’s BART determinations contained “systemic

deficiencies” and a “large number” of errors. 79 Fed. Reg. 

24,341, 24,343 (quotation marks omitted). On a broad scale, 

the EPA acknowledges that Pennsylvania’s SIP lacked 

necessary technical information and supporting 
32

documentation, and that it was insufficiently thorough. Id. at 

24,342 (noting that “many of the comments criticizing 

Pennsylvania’s BART determinations are correct,” and that 

“the Pennsylvania regional haze SIP contains very limited 

information describing Pennsylvania’s analyses and 

consideration of the BART factors”); id. (stating 

“Pennsylvania should have provided a more thorough and 

detailed analysis of costs and visibility impacts in its regional 

haze SIP”). More specifically, the EPA concedes that 

Pennsylvania erred at multiple steps of the BART analysis. 

For example, by failing to consider the cumulative visibility 

impact of each source, Pennsylvania understated the impact 

that pollution originating within its borders had on Class I 

areas beyond those borders. Id. (“EPA also agrees . . . that . . 

. Pennsylvania should have taken into account the visibility 

impacts at all impacted Class I areas rather than focusing 

solely on the benefits at the most impacted area.”). The EPA

also admits that Pennsylvania’s cost-effectiveness 

calculations were flawed. Id. (“Similarly, EPA agrees with 

the commenters that Pennsylvania’s reliance on the $/dv 

metric was flawed for multiple reasons.”); id. (agreeing with 

the commenters “that many of the [pollution] controls under 

consideration [by Pennsylvania] were likely cost-effective 

measures,” even though the state rejected them as too 

expensive).

Tellingly, the EPA concedes that these various failures 

impaired its ability to independently assess Pennsylvania’s 

analysis. In the agency’s own words, it has a duty under the 

Clean Air Act “to exercise independent technical judgment in 

evaluating the adequacy of a state’s regional haze SIP, 

including its BART determinations.” Approval, Disapproval 

and Promulgation of Implementation Plans; State of 
33

Wyoming; Regional Haze State Implementation Plan; 

Federal Implementation Plan for Regional Haze, 79 Fed. 

Reg. 5,032, 5,064 (Jan. 30, 2014). Here, however, with 

respect to the control technologies considered by 

Pennsylvania and the costs associated with those controls, the 

EPA concedes that “the cursory information available in the 

record does not allow for an assessment of how these 

numbers were derived or whether Pennsylvania’s analyses 

were reasonably done.” 2014 Final Rule, 79 Fed. Reg. 

24,342. Regarding Pennsylvania’s determination of potential 

visibility improvements in Class I areas, the EPA similarly 

notes that “it is difficult to assess the estimates of the 

improvements in visibility associated with various controls 

given the limited information in the SIP as to the assumptions 

relied on in the modeling and the summary nature of the 

results provided.” Id. Likewise, regarding Pennsylvania’s 

estimates of the costs of implementing certain pollution 

controls, the EPA laments: “Unfortunately, where controls 

were estimated to be more cost-effective, EPA cannot assess 

the extent to which Pennsylvania’s analyses are reasonable 

estimates for purposes of making a BART determination.” 

Id. 

Despite the multitude of problems with Pennsylvania’s 

SIP, and the EPA’s admitted inability to adequately assess the 

state’s analysis, the EPA asserts that “the information that 

Pennsylvania did provide” is sufficient to conclude “that 

Pennsylvania’s ultimate BART determinations were 

nevertheless reasonable.” Id. Without citation to supporting 

authorities or further explanation, the EPA broadly claims 

that, “based on the cost estimates for other BART sources in 

other states” it has reviewed, “Pennsylvania’s cost numbers 

appear to be generally consistent for such controls . . . .” Id.
34

The EPA further concludes that “[w]here Pennsylvania 

estimated the costs of controls to be in the tens of thousands 

or hundreds of thousands of dollars per ton of pollutant 

removed, Pennsylvania’s conclusions that such controls are 

not cost-effective seem reasonable, even assuming that the 

true cost[s] of controls are likely less than what Pennsylvania 

estimated.” Id.

As a reviewing court, we must ensure that the EPA

“articulate[s] a satisfactory explanation” for its decision to 

approve Pennsylvania’s SIP, “including a rational connection 

between the facts found and the choice made.” Prometheus 

Radio Project, 373 F.3d at 389–90 (citation and quotation 

marks omitted). The EPA’s conclusory assertions on the 

issue of control costs and its invocation of its own experience 

addressing cost estimates do not suffice. See Natural Res. 

Def. Council, Inc. v. Hodel, 865 F.2d 288, 298 (D.C. Cir. 

1988) (per curiam) (“[C]onclusory remarks . . . do not equip a 

decisionmaker to make an informed decision about alternative 

courses of action or a court to review the [agency’s] 

reasoning.”); see also Ass’n of Private Colleges & Univs. v. 

Duncan, 870 F. Supp. 2d 133, 154 (D.D.C. 2012) (“That this 

explanation could be used to justify any [determination] at all 

demonstrates its arbitrariness.”); Nat’l Parks Conservation 

Ass’n, 788 F.3d at 1145 (remanding where the “reasoning 

fails to reveal to a reader how EPA determined that the cost 

of controls were not justified”).

The EPA also asserts that “[w]hen the other key BART 

factor—visibility—is taken into account, . . . an overall 

picture emerges that supports Pennsylvania’s BART 

determinations.” 2014 Final Rule, 79 Fed. Reg. 24,342. In 

essence, the EPA contends that, given Pennsylvania’s 

calculations showing that its BART-eligible sources had 
35

minimal visibility impact at Class I areas, it was reasonable to 

conclude that additional pollution controls were unwarranted. 

We are unpersuaded by this reasoning. As noted 

above, the 2014 Final Rule repeatedly criticizes 

Pennsylvania’s SIP calculations and supporting 

documentation, noting that the SIP is so lacking that it is 

difficult to assess the visibility impact calculations 

Pennsylvania did conduct. What the EPA could determine, 

however, was that Pennsylvania underestimated the impact of 

pollution from its sources because it failed to calculate the 

cumulative visibility impact from each source. The EPA now 

urges us to rely on these very same visibility impact 

calculations to conclude that the “overall picture” supports 

Pennsylvania’s BART analysis. The EPA unconvincingly 

insists we rely on what it has said is flawed.13

 

13 The EPA also argues that because 26 of 

Pennsylvania’s 34 BART-eligible sources had less than a 0.5 

deciview impact on any Class I area, the state could have 

exempted these 26 sources from its BART analysis. Under 

the agency’s own regulations and the BART Guidelines, 

however, a state need not exempt these sources. See, e.g., 

Regional Haze Regulations, 70 Fed. Reg. 39,104, 39,107 

(“States certainly have the discretion to consider that all 

BART-eligible sources within the State are ‘reasonably 

anticipated to cause or contribute’ to some degree of visibility 

impairment in a Class I area.”); BART Guidelines, 40 C.F.R. 

pt. 51, app. Y (“Once you have compiled your list of BARTeligible sources, you need to determine whether . . . to make 

BART determinations for all of them . . . .”).
36

In the end, the EPA has identified a host of problems 

with Pennsylvania’s BART analysis. What it has not done, 

however, is provide a sufficient explanation as to why it 

overlooked these problems and approved Pennsylvania’s SIP. 

Because we, as a reviewing court, need an agency to show its 

work before we can accept its conclusions, we will remand 

this case to the EPA for further consideration.

IV.

For the aforementioned reasons, we will vacate the 

2014 Final Rule to the extent it approved Pennsylvania’s 

source-specific BART analysis and remand to the EPA for 

further proceedings consistent with this Opinion.