FOR PUBLICATION

UNITED STATES COURT OF APPEALS

FOR THE NINTH CIRCUIT

STATE OF ARIZONA, EX REL. HENRY

R. DARWIN, Director, Arizona

Department of Environmental

Quality,

Petitioner,

v.

U.S. ENVIRONMENTAL PROTECTION

AGENCY; LISA P. JACKSON,

Administrator, United States

Environmental Protection Agency,

Respondents,

NATIONAL PARKS CONSERVATION

ASSOCIATION; SIERRA CLUB,

Respondent-Intervenor.

No. 13-70366
2 ARIZONA EX REL. DARWIN V. USEPA

SALT RIVER PROJECT

AGRICULTURAL IMPROVEMENT AND

POWER DISTRICT,

Petitioner,

v.

U.S. ENVIRONMENTAL PROTECTION

AGENCY,

Respondent,

NATIONAL PARKS CONSERVATION

ASSOCIATION; SIERRA CLUB,

Respondent-Intervenors.

No. 13-70410

OPINION

On Petition for Review of an Order of the

Environmental Protection Agency

Argued and Submitted

March 9, 2015—San Francisco, California

Filed February 24, 2016

Before: Marsha S. Berzon, Jay S. Bybee,

and John B. Owens, Circuit Judges.

Opinion by Judge Berzon
ARIZONA EX REL. DARWIN V. USEPA 3

SUMMARY*

Environmental Law 

The panel denied consolidated petitions for review of a

Final Rule, promulgated by the Environmental Protection

Agency under the Clean Air Act, that partially disapproved

Arizona’s regional haze State Implementation Plan (“SIP”) – 

setting forth emission limits and other measures – and issued

a Federal Implementation Plan (“FIP”) in place of the

disapproved SIP elements.

The panel held that the EPA did not act arbitrarily and

capriciously when it disapproved in part the SIP’s “best

available retrofit technology” for the Coronado Generating

Station, a coal-fueled power plant located in Eastern Arizona,

and when it issued a replacement FIP as to the disapproved

portions. The panel also held that the EPA did not err

procedurally in promulgating the FIP in the same rule as its

partial disapproval of the SIP.

The panel held that its ultimate review of the EPA’s FIP

must await the EPA’s final action on its proposal to revise the

FIP in specific respects. Accordingly, the panel stayed the

proceedings as to evaluation of the FIP’s technical feasibility

until the administrative process was complete.

* This summary constitutes no part of the opinion of the court. It has

been prepared by court staff for the convenience of the reader.
4 ARIZONA EX REL. DARWIN V. USEPA

COUNSEL

Peter Glaser (argued), Troutman Sanders LLP, Washington,

D.C.; Paul L. Gale, Troutman Sanders LLP, Irvine,

California; Carroll W. McGuffeyIII, Troutman Sanders LLP,

Atlanta, Georgia; Thomas C. Horne, Arizona Attorney

General, and James T. Skardon, Assistant Attorney General,

Phoenix, Arizona, for Petitioner State of Arizona.

Norman W. Fichthorn (argued) and Aaron M. Flynn, Hunton

& Williams LLP, Washington, D.C., for Petitioners Arizona

Public Service Company and Salt River Project Agricultural

Improvement and Power District.

Angeline Purdy (argued), United States Department of

Justice; RobertG.Dreher, ActingAssistant AttorneyGeneral,

Washington, D.C., for Respondent United States

Environmental Protection Agency.

Michael A. Hiatt (argued), Earthjustice, Denver, Colorado;

Suma Peesapati, Earthjustice, San Francisco, California, for

Respondent-Intervenors National Parks Conservation

Association and Sierra Club.

Maureen A. Scott, Matthew Laudone, and Janice M. Alward,

Phoenix, Arizona, for Amicus Curiae Arizona Corporation

Commission.

Michelle L. Wood, Phoenix, Arizona, for Amicus Curiae

Arizona Residential Utility Consumer Office.

Gordon A. Coffee, John M. Holloway III, and Stephanie B.

Sebor, Winston & Strawn LLP, Washington, D.C.; Rae

Cronmiller, Environmental Counsel, National Rural Electric
ARIZONA EX REL. DARWIN V. USEPA 5

Cooperative Association, Arlington, Virginia, for Amicus

Curiae National Rural Electric Cooperative Association.

OPINION

BERZON, Circuit Judge:

Congress initially enacted the Clean Air Act (“the Act” or

“CAA”) in 1963 to “protect and enhance the quality of the

Nation’s air resources so as to promote the public health and

welfare and the productive capacity of its population.” 

42 U.S.C. § 7401(b)(1). Later, in the Clean Air Act

Amendments of 1977, Pub. L. No. 95-95, § 128, 91 Stat. 685,

742 (current version at 42 U.S.C. § 7491), Section 169A was

added “in response to a growing awareness that visibility was

rapidly deteriorating in many places, such as wilderness areas

and national parks.” Am. Corn Growers Ass’n v. EPA,

291 F.3d 1, 3 (D.C. Cir. 2002) (internal quotation marks

omitted) (quoting Chevron U.S.A., Inc. v. EPA, 658 F.2d 271,

272 (5th Cir. 1981)).

To improve outdoor visibility, the Act as amended

“invites each State to submit to EPA a ‘State Implementation

Plan’ (‘SIP’) setting forth emission limits and other measures

necessary to make reasonable progress toward the national

visibility goal.” Nat’l Parks Conservation Ass’n v. EPA,

788 F.3d 1134, 1138 (9th Cir. 2015) (“NPCA”) (citing

42 U.S.C. §§ 7410(a), 7491(b)(2)). SIPs must include

determinations of the “best available retrofit technology”

(“BART”) to reduce emissions from certain major emission

sources, including large fossil-fuel power plants. 42 U.S.C.

§ 7491(b)(2). If a state chooses not to submit a SIP, or if

EPA disapproves a SIP in whole or in part, “the Act requires
6 ARIZONA EX REL. DARWIN V. USEPA

EPA to produce a ‘Federal Implementation Plan’ (‘FIP’) for

that State.” NPCA, 788 F.3d at 1138–39 (citing 42 U.S.C.

§ 7410(c)(1)(A)).

Arizona and the Salt River Project Agricultural

Improvement and Power District (“the State” and “SRP,”

respectively, and, collectively, “Petitioners”) petition for

review of a Final Rule (“Rule”) promulgated by EPA. The

Rule partially disapproved Arizona’s regional haze SIP

submission and promulgated a FIP in place of the

disapproved SIP elements. Approval, Disapproval and

Promulgation of Air Quality Implementation Plans, 77 Fed.

Reg. 72,512 (Dec. 5, 2012) (the “Final Rule”). In what

remains of this case,1 Petitioners challenge (1) EPA’s

disapproval of Arizona’s BART determinations, and (2) the

FIP’sreplacement determinations, concerning nitrogen oxides

(NOX) emission limits at Coronado Generating Station

(“Coronado”), a two-unit, 733-megawatt coal-fueled power

plant located in Eastern Arizona.

We conclude that EPA did not act arbitrarily and

capriciously when it disapproved in part the SIP’s BART

determinations for Coronado and issued a replacement FIP as

to the disapproved portions. We therefore deny the

consolidated petitions for review.

 

1

See infra note 6.
ARIZONA EX REL. DARWIN V. USEPA 7

I. STATUTORY AND REGULATORY

BACKGROUND

A. The Clean Air Act’s Visibility Protections

In enacting Section 169A2 Congress “declare[d] as a

national goal the prevention of any future, and the remedying

of any existing, impairment of visibility in mandatory class I

Federal areas which impairment results from manmade air

pollution.” § 7491(a)(1). “Class I” Federal areas include

certain national wilderness areas and national parks. Arizona

contains twelve Class I areas, the largest of which is Grand

Canyon National Park.

Section 169A seeks to reduce “regional haze,” that is,

“visibility impairment caused by geographically dispersed

sources emitting fine particles and their precursors into the

air.” Am. Corn Growers, 291 F.3d at 3 (internal quotation

marks omitted). In service of this goal, Section 169A

requires that certain sources contributing to visibility

impairment install BART—which, again, is an acronym for

“best available retrofit technology.”3 States must review all

major stationary emissions sources built between 1962 and

1977 to determine whether the source “emits any air pollutant

2 We use “Section 169A” to refer generically to the visibility

amendments, but use the codified version, 42 U.S.C. § 7491, for specific

citations.

3 We apologize for the extensive use of acronyms in this opinion and

include a brief glossary at the end to aid the reader. Environmental

litigation is awash in such alphabetical shorthand, and the “insiders”

would not know what we meant if we used other terms. We have

therefore decided against expanding the Federal Reporter 3d (F.3d, of

course, another shorthand) by stubbornly spelling out each term.
8 ARIZONA EX REL. DARWIN V. USEPA

which may reasonably be anticipated to cause or contribute

to any impairment of visibility in” any Class I area. 

§ 7491(b)(2)(A). The states are then responsible for

determining the appropriate BART controls for each source. 

See 42 U.S.C. § 7491(b)(2)(A), (g)(2).

EPA reviews the states’ SIP submissions, if any, for

consistency with the statute and regulations. See 42 U.S.C.

§ 7410(c)(1)(A); Oklahoma v. EPA, 723 F.3d 1201, 1204

(10th Cir. 2013). If EPA determines that a SIP does not meet

the Act’s requirements, the federal agency may itself

determine BART and impose a FIP. See 42 U.S.C.

§ 7491(b)(2)(A). More specifically, if EPA finds that a state

has not submitted a required SIP, determines that a submitted

SIP is incomplete, or disapproves a SIP in whole or in part, it

“shall promulgate a [FIP] at any time within 2 years.” 

42 U.S.C. § 7410(c)(1). EPA must promulgate a FIP “unless

the State corrects the deficiency, and [EPA] approves the plan

or plan revision, before [EPA] promulgates [the FIP].” Id.

When determining BART, states or EPA must consider

five factors: “[1] the costs of compliance, [2] the energy and

nonair 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.” 

42 U.S.C. § 7491(g)(2). Each source subject to the BART

requirement must install and operate BART “as expeditiously

as practicable but in no event later than five years after the

date of approval of a [SIP] . . . or the date of promulgation of

[a FIP].” 42 U.S.C. §§ 7491(g)(4).
ARIZONA EX REL. DARWIN V. USEPA 9

B. EPA Regional Haze Regulations

Section 169A directed EPA to issue regulations requiring

states with Class I areas within their borders to submit SIPs

containing “emission limits, schedules of compliance and

other measures as may be necessary to make reasonable

progress toward meeting the national goal.” 42 U.S.C.

§ 7491(b)(2). EPA was also required to develop guidelines

for the states “on appropriate techniques and methods for

implementing” Section 169A. Id. § 7491(b)(1). In 1990,

Congress added Section 169B to expand the CAA’s focus to

include regional haze, see 42 U.S.C. § 7492—that is,

“visibility impairment that is caused by the emission of air

pollutants from numerous sources located over a wide

geographic area,” 40 C.F.R. § 51.301. “Section 169B

requires, among other things, that EPA undertake research to

identify ‘sources’ and ‘source regions’ of visibility

impairment in Class I areas, consider designating transport

commissions to study the interstate movement of pollutants,

and establish a transport commission for the Grand Canyon

National Park.” Am. Corn Growers, 291 F.3d at 4.

Pursuant to Sections 169A and 169B, EPA in 1999

promulgated regional haze regulations. 64 Fed. Reg. 35,714

(July 1, 1999) (codified at 40 C.F.R. § 51.300–.309). The

D.C. Circuit partially vacated those regulations in American

Corn Growers Ass’n v. EPA, 291 F.3d at 6.4

 Thereafter, the

agency in 2005 promulgated new regulations, the Regional

Haze Regulations and Guidelines for Best Available Retrofit

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

(July 6, 2005) (“Haze Regulations”). At the same time, EPA

issued Guidelines to help states identify “BART-eligible”

 

4 American Corn Growers is discussed infra, at p. 21.
10 ARIZONA EX REL. DARWIN V. USEPA

sources and determine the appropriate BART for each source. 

Id. at 39,156 (codified at 40 C.F.R. pt. 51, app. Y)

(“Guidelines”); see also 42 U.S.C. § 7491(b).

The Haze Regulations set a goal of achieving natural

visibility at all Class I areas by 2064. 40 C.F.R. § 51.308. 

Toward that end, the Regulations direct states to submit SIPs

to EPA containing “goals (expressed in deciviews) that

provide for reasonable progress towards achieving natural

visibility conditions.” 40 C.F.R. § 51.308(d)(1). A

“deciview” is a measurement of visibility impairment. More

specifically, it “is a haze index 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.” 

40 C.F.R. § 51.301. One deciview is the minimum visibility

impairment humans can perceive. See Guidelines at 39,120

n.32.

The SIP must also include, among other matters,

“emission limitations representing BART and schedules for

compliance with BART for each BART-eligible source that

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). The BART requirements apply

unless the state opts to implement an alternative emission

control measure that provides greater progress than would be

achieved through the installation of BART (commonly

referred to as “better-than BART”). See id. § 51.308(e)(2).

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.” 
ARIZONA EX REL. DARWIN V. USEPA 11

Id. § 51.301. Three of the major pollutants that states must

evaluate when determining whether a source causes or

contributes to visibility impairment are sulfur dioxide

(“SO2”), nitrogen oxides (“NOX”), and particulate matter. See

Guidelines at 39,162. States must establish BART for each

pollutant. Id. at 39,163.

BART determinations for fossil-fueled power plants with

a total generating capacity greater than 750 megawatts must

comply with the Guidelines. 42 U.S.C. § 7491(b)(2). The

Guidelines set forth the following five-step process:

(1) identify all available retrofit control technologies;

(2) eliminate technically infeasible options; (3) evaluate the

control effectiveness of remaining control technologies;

(4) evaluate impacts and document the results; and

(5) evaluate the visibility impacts. Guidelines at 39,164. The

Guidelines also provide more detailed instructions for

performing each of these steps. Id. at 39,164–72. “For

sources other than 750 MW power plants . . . States retain the

discretion to adopt approaches that differ from the

[G]uidelines.” Guidelines at 39,158.

Section 309 of the Haze Regulations, 40 C.F.R. § 51.309,

allows certain western states to develop alternative visibility

improvement programs, based on the recommendations of the

Grand Canyon Visibility Transport Commission (“the

Commission”). The Commission was created to address

visibility impairment “for the region affecting the visibility of

the Grand Canyon National Park.” See 42 U.S.C. § 7492(f). 

This region includes sixteen Class I areas on the Colorado

Plateau located in Arizona, Colorado, New Mexico, and Utah. 

40 C.F.R. § 51.309(b). States within the relevant Transport

Region—Arizona, California,Colorado, Idaho, Nevada, New

Mexico, Oregon, Utah, and Wyoming—that submit a SIP
12 ARIZONA EX REL. DARWIN V. USEPA

compliant with all of the Commission’s recommendations are

“deemed to comply with the requirements for reasonable

progress with respect to the 16 Class I areas.” Id.

§ 51.309(a). Any covered state that elects not to submit a

Section 309 plan is “subject to the requirements of [Section

308] in the same manner and to the same extent as any State

not included within the Transport Region.” Id. Further, even

if a state submits a Section 309 SIP, it must submit a Section

308 SIP or otherwise establish “reasonable progress goals” —

including BART determinations — for any Class I areas in

the state not covered under Section 309. Id. § 51.309(g)(2).

II. PROCEDURAL HISTORY

A. The State’s SIP Submissions

The Haze Regulations set a December 17, 2007 deadline

for SIP submittals. 40 C.F.R. § 51.308(b). EPA issued a

finding on January 15, 2009, that thirty-seven states,

including Arizona, had not submitted SIPs satisfying the

Act’s visibility requirements. Finding of Failure To Submit

State Implementation Plans Required by the 1999 Regional

Haze Rule, 74 Fed. Reg. 2,392 (Jan. 15, 2009). Noting that

Arizona had “opted to develop [its SIP] based on the

recommendations of the Grand Canyon Visibility Transport

Commission” pursuant to Section 309, id. at 2,393, EPA

found that the State had failed to “submit the plan elements

required by” two provisions of the Section 309 regulations,

40 C.F.R. §§ 51.309(d)(4) and 51.309(g).5Id. EPA further

5 Arizona’s Section 309 SIP, which Arizona submitted to EPA on

December 23, 2003, and supplemented a year later, merits further

explanation. EPA did not act upon the State’s 2003 and 2004

submissions. The Section 309 regulations were revised in October 2006,
ARIZONA EX REL. DARWIN V. USEPA 13

explained that “[t]his finding starts the two year clock for the

promulgation by EPA of a FIP.” Id.

Although EPA determined that its January 2009 finding

triggered the Act’s two-year window, see 42 U.S.C.

§ 7410(c)(1), it did not take any further action by January

2011. Several environmental groups sued EPA in early 2011

to compel the agency to promulgate FIPs for the states

covered by the January 2009 finding. See Nat’l Parks

Conservation Ass’n v. EPA, No. 11-CV-01548 (D.D.C.). 

EPA and the plaintiff groups entered into a Consent Decree

setting deadlines for EPA action for each state covered by the

following the D.C. Circuit’s decision in Center for Energy and Economic

Development v. EPA, 398 F.3d 653 (D.C. Cir. 2005). See 71 Fed. Reg.

60,612 (Oct. 13, 2006). Arizona then resubmitted its Section 309 SIP to

EPA in December 2008, acknowledging that the plan did not include

provisions required under 40 C.F.R. §§ 51.309(d)(4) and 51.309(g) as

revised. In 2013, EPA disapproved the Section 309 SIP because of these

deficiencies. 78 Fed. Reg. 48,326 (Aug. 8, 2013).

Arizona contends that, as EPA did not expressly find that its Section

309 SIP was incomplete within six months of its initial submission in

2003, the plan became complete by operation of law. Thus, it contends,

42 U.S.C. § 7410(k)(2) required EPA to disapprove its SIP within one

year, which, of course, it did not do. But, as EPA noted in its 2013

disapproval, the fact that Arizona’s submission met the completeness

criteria set out in § 7410(k) “[did] not mean that [it was] complete in the

sense that [it] contained the provisions necessary to satisfy the

requirements of [Section 309].” 78 Fed. Reg. at 48,327. The § 7410(k)

criteria “do not include the substantive provisions that a given SIP must

include to comply with the minimum requirements of the [Act].” Id.

Those provisions are instead “set out in the [Act] itself and in EPA’s

implementing regulations.” Id. EPA concluded that it could not approve

Arizona’s previously submitted SIP until it was resubmitted with valid

provisions for addressing stationary sources, provisions Arizona has

conceded were not included in the 2003 plan. Id.
14 ARIZONA EX REL. DARWIN V. USEPA

lawsuit. For Arizona, the Consent Decree required EPA by

November 15, 2012 either to approve the State’s SIP with

respect to its BART determinations or to propose a FIP.

To avoid a FIP, Arizona elected to develop a Section 308

SIP; it was submitted to EPA on February 28, 2011. The SIP

proposed progress goals and long term strategies to achieve

those goals, including BART determinations. Specifically,

the SIP included BART determinations for emission units at

three fossil fuel power plants that Arizona concluded were

BART-eligible and subject to BART: Apache Generating

Station Units 1–3, Cholla Power Plant Units 2–4, and

Coronado Generating Station Units 1–2. Only the SIP’s

determinations as to Coronado are at issue in this case.6

Overall, the State’s BART determinations for NOX

, the

pollutant with which we are concerned here, consisted of

“combustion controls, either in the form of low-NOX burners

(LNB) with flue gas recirculation (FGR), or LNB with

overfire air (OFA) or separated overfire air (SOFA).” 77 Fed.

Reg. 42,834, 42,842 (July 20, 2012). For Coronado, Arizona

6 The State and other industry petitioners (Arizona Electric Power

Cooperative, Arizona Public Service Company, and PacifiCorp) initially

filed petitions for review of the Final Rule’s determinations as to Apache

and Cholla, and we consolidated our review of those petitions with this

case. On February 20, 2015, we ordered the litigation with respect to

Cholla severed and held in abeyance pending completion of state and

federal administrative proceedings that could render the petitions for

review moot. As of the publication of this opinion, those proceedings

have not yet been completed. On June 17, 2015, we dismissed the

petitions as to Apache after EPA issued a final action approving a sourcespecific revision to the SIP that established a BART alternative for

Apache and withdrawing the portions of the FIP addressing BART for

Apache. See Approval and Promulgation of Air Quality Implementation

Plans, 80 Fed. Reg. 19,220 (Apr. 10, 2015).
ARIZONA EX REL. DARWIN V. USEPA 15

determined that the proper control technology was low-NOX

burners with overfire air. Translating the chosen technology

into the resulting emission improvement, the SIP established

enforceable NOX emissions limits of 0.32 lb/mmBtu for both

units of the Coronado facility.

7

B. EPA’s Actions

In July 2012, EPA proposed (1) partially to approve and

partially to disapprove the State’s BART determinations with

respect to the three power plants in its Section 308 SIP; and

(2) to promulgate a FIP for the disapproved elements. 

77 Fed. Reg. at 42,834. EPA deferred taking action “on the

State’s other BART determinations or any other parts of the

SIP regarding the remaining requirements of the [Haze

Regulations].” Id. at 42,836. In a later rulemaking, EPA

approved in part and disapproved in part the remaining

portions of Arizona’s Section 308 SIP. See 78 Fed. Reg.

46,142 (July 30, 2013) (“Phase 2 Rule”).8 After a notice-andcomment period, EPA promulgated the Final Rule challenged

here, in December 2012. 77 Fed. Reg. at 72,512.

The Final Rule approved the State’s emission limits for

SO2 and particulate matter at all the units but disapproved the

State’s emissions limits for NOX at the seven coal-fired

7 The SIP also included BART determinations for SO2 and particulatematter, but they are not at issue in this case.

8 Petitioners petition for review of the Phase 2 Rule in Phoenix Cement

Co. v. EPA, No. 13-73383, decided contemporaneously with this case in

a memorandum disposition.
16 ARIZONA EX REL. DARWIN V. USEPA

generating units at Apache, Cholla, and Coronado.9Id. at

72,514. EPA explained that Arizona’s “overall approach” to

the five-step BART analysis was “generally reasonable and

consistent with the [Haze Regulations] and the BART

Guidelines.” 77 Fed. Reg. at 42,840. But it determined that

Arizona’s BART analysis suffered from several flaws,

particularly with respect to costs and visibility improvement,

that resulted in NOX control determinations “inconsistent”

with the Haze Regulations. 77 Fed. Reg. at 42,841–42; see

also 77 Fed. Reg. at 72,516–21. EPA found that the State’s

analyses with respect to SO2 and particulate matter suffered

from similar “deficiencies,” 77 Fed. Reg. at 72,517, but

nonetheless approved Arizona’s determinations for these

pollutants because the analytical flaws had no “substantive

impact on [the State’s] selection of controls.” 77 Fed. Reg.

at 42,841.

Explaining that the Consent Decree required EPA

promptly to issue a FIP for any portion of the Arizona SIP it

disapproved, the Final Rule simultaneously issued a FIP

addressing the disapproved elements. 77 Fed. Reg. at

72,567–68. EPA conducted a “new five-factor BART

analysis” of the three power plants to evaluate Arizona’s SIP

and “to document the technical basis for proposing BART

determinations in [EPA’s] FIP,” focusing in particular on

analyzing the cost controls and visibility impacts associated

with the different BART options. 77 Fed. Reg. at 42,852; see

generally 77 Fed. Reg. at 42,852–65; 77 Fed. Reg. at

72,526–61.

9 EPA approved Arizona’sBART determination for the natural gas-fired

Apache Unit 1. See 77 Fed. Reg. at 72,514.
ARIZONA EX REL. DARWIN V. USEPA 17

Based on these analyses, EPA concluded that selective

catalytic reduction (“SCR”) with low-NOX burners and

overfire air — the most stringent available retrofit control

option — was the proper BART control for Coronado. See

77 Fed. Reg. at 42,864. EPA proposed NOX emission limits

much lower than those contained in Arizona’s SIP: 0.050

lb/mmBtu (calculated on a rolling 30-boiler-operating-day

average) for Coronado Unit 1, and 0.080 lb/mmBtu for

Coronado Unit 2.10

Id. at 42,865, tbl. 24. EPA also proposed

compliance deadlines, as well as recordkeeping and reporting

requirements, to enforce the FIP’s BART determinations.11

Id. Finally, EPA sought public comment on several aspects

of the proposed FIP. Id. at 42,835–36.

In the Final Rule, EPA revised certain elements of the

proposed FIP in response to public comments and additional

information. 77 Fed. Reg. at 72,514. Notably, EPA

weakened the final NOX emissions limits to “provide an extra

margin of compliance” and changed its methodology to

require plant-wide averaging. Id. at 72,514–15. As relevant

here, EPA changed its proposed NOX emission limits from

0.050 lb/mmBtu for Coronado Unit 1 and 0.080 lb/mmBtu for

Coronado Unit 2 to an averaged limit of 0.065 lb/mmBtu

across both units of the Coronado facility. Id. at 72,514–15,

tbl. 1. The Final Rule also extended the compliance deadlines

for installation and operation of the controls at the facilities. 

See id.

10 Arizona’s SIP had adopted NOX emissions limits of 0.32 lb/mmBtu

for both units of the Coronado facility.

11 Arizona’s SIP was disapproved in part because it lacked such

deadlines and requirements. See 77 Fed. Reg. at 72,514.
18 ARIZONA EX REL. DARWIN V. USEPA

Arizona and SRP filed timely petitions for review of the

Final Rule. After the cases were consolidated, we permitted

National ParksConservation Association and Sierra Club (the

“Respondent-Intervenors”) to intervene in the consolidated

action.

III. DISCUSSION

A. Standard of Review

Under the Administrative Procedure Act (“APA”), we

uphold a final agency action unless it is “arbitrary, capricious,

an abuse of discretion, or otherwise not in accordance with

law.” 5 U.S.C. § 706(2). To meet its regulatory obligations,

an agency 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.” 

Motor Vehicle Mfrs. Ass’n of U.S., Inc. v. State Farm Mut.

Auto. Ins. Co., 463 U.S. 29, 43 (1983) (internal quotation

marks and citation omitted). An agency’s action is “arbitrary

and capricious” within the meaning of APA § 706(2) “if the

agency has relied on factors which Congress has not intended

it to consider, entirely failed to consider an important aspect

of the problem, offered an explanation for its decision that

runs counter to the evidence before the agency, or is so

implausible that it could not be ascribed to a difference in

view or the product of agency expertise.” Id. “When we

review an agencyaction ‘involv[ing] primarily issues of fact,’

and where ‘analysis of the relevant documents requires a high

level of technical expertise, we must defer to the informed

discretion of the responsible federal agencies.’” NPCA,

788 F.3d at 1141 (quoting Marsh v. Or. Nat. Res. Council,

490 U.S. 360, 377 (1989)).
ARIZONA EX REL. DARWIN V. USEPA 19

The parties vigorously dispute how we should apply the

APA arbitrary and capricious standard here. EPA maintains

that in this case, as in most administrative law cases, the

standard calls for judicial deference to the federal agency as

to the decisions within its authority. Arizona (with the

support of SRP) contends, to the contrary, that Section

169A’s allocation of initial BART authority to the states

requires that we defer to “the state’s expert judgments, not to

EPA’s.” As this brief summary indicates, the parties’

disagreement concerning judicial review is grounded in

competing visions of the Act’s division of responsibility

between the states and EPA. We therefore begin our analysis

at the agency level, progressing thereafter to the question of

our review standard.

The states possess “broad authority over BART

determinations. . . . Congress intended the states to decide

which sources impair visibility and what BART controls

should apply to those sources.” Am. Corn Growers, 291 F.3d

at 8. In this connection, Section 169A of the Act gives states

the initial responsibilities of determining which sources are

subject to BART and of deciding, based on consideration of

the five statutory factors, what BART controls must be

installed and what the resulting emission limitations should

be. See 42 U.S.C. § 7491(b)(2)(A), (g)(2).

But, as the Tenth Circuit has noted, the BART

determination process “does not differ from other parts of the

[Act]—states have the ability to create SIPs, but they are

subject to EPA review.” Oklahoma, 723 F.3d at 1209; see

also N. Dakota v. EPA, 730 F.3d 750, 758 (8th Cir. 2013). 

EPA may only approve SIPs, or portions of SIPs, that “meet[]

all the applicable requirements” of the Act. 42 U.S.C.

§ 7410(k)(3). Thus, while the Act “gives states discretion in
20 ARIZONA EX REL. DARWIN V. USEPA

balancing the five BART factors, it also mandates that the

state adhere to certain requirements when conducting a

BART analysis.” Oklahoma, 723 F.3d at 1208. 

Consequently, when reviewing regional haze SIPs, EPA may

not approve “a BART determination that is based upon an

analysis that is neither reasoned nor moored to the [Act]’s

provisions.” N. Dakota, 730 F.3d at 761. In short, EPA is not

limited to the “ministerial” role of verifying whether a

determination was made; it must “review the substantive

content of the BART determination.” Id.

Alaska Department of Environmental Conservation v.

EPA, 540 U.S. 461 (2004) (“ADEC”), does not support the

opposite conclusion, Arizona’s contention to the contrary

notwithstanding. ADEC involved a challenge to EPA’s

authority to review states’ determinations of “best available

control technology” (“BACT”) under the Prevention of

Significant Deterioration program (“PSD”), 42 U.S.C. § 7470

et seq., a different part of the Act from the one mandating

BART. See ADEC, 540 U.S. at 468. The PSD program is

applicable to new construction of pollution emitting facilities. 

See 42 U.S.C. § 7475. As with the BART process at issue

here, for the PSD program the state “exercises primary or

initial responsibility for identifying BACT in line with the

Act[].” ADEC, 540 U.S. at 484.

ADEC rejected an argument made by the petitioners in

that case similar to Arizona’s contention here—in that

instance, that EPA’s enforcement role was limited to ensuring

that the state-issued PSD permit contain a BACT

requirement. Instead, ADEC accepted EPA’s interpretation

of its authority—that EPA is authorized to review state

BACT determinations to ensure they are “reasonablymoored

to the Act’s provisions.” Id. at 485, 488–89.
ARIZONA EX REL. DARWIN V. USEPA 21

To be sure, ADEC explained, Alaska had “considerable

leeway” in its BACT determinations, and EPA was required

to accord appropriate deference to such determinations. Id.

at 490. But EPA has the authority to verify “substantive

compliance” with the Act’s BACT provisions “to guard

against unreasonable designations.” Id. at 489–90. ADEC is

thus fully consistent with our conclusion that EPA has

substantive authority to assure that a state’s proposals comply

with the Act, not simply the ministerial authority to assure

that the state has made some determination of BART.

Arizona also invokes American Corn Growers, in which

petitioners challenged aspects of EPA’s initial 1999 regional

haze rule. That case does not support Arizona’s position

regarding EPA’s SIP role either. The D.C. Circuit in

American Corn Growers disapproved EPA’s initial rule in

part because its requirements were “inconsistent with the

Act’s provisions giving the states broad authority over BART

determinations.” Am. Corn Growers, 291 F.3d at 8. But

American Corn Growers in no way suggested that once a

state has exercised its BART role by proposing a SIP, EPA

lacks authority substantively to review the SIP for

consistency with the Act.

From our determination that EPA has a substantive role

in deciding whether state SIPs are compliant with the Act and

its implementing regulations follows the conclusion that the

ordinary APA “arbitrary and capricious” judicial review

standard applies, with the requisite deference, to EPA’s

determinations. Again, neither American Corn Growers nor

ADEC supports a contrary conclusion. In particular, neither

ADEC nor American Corn Growers bolsters Arizona’s

contention that, upon judicial review, EPA bears the burden
22 ARIZONA EX REL. DARWIN V. USEPA

of proving that the State’s BART determinations are

unreasonable.

ADEC did state that, for the purposes of deciding whether

the state agency’s BACT determination in that case was

reasonable, “the production and persuasion burdens remain

with EPA.” 540 U.S. at 494. But ADEC was at that juncture

addressing a concern wholly absent here. In ADEC, the

Supreme Court held that the Act prevented EPA from

“gain[ing] a proof-related tactical advantage” by imposing a

stop-construction order rather than filing a civil action in state

court. 540 U.S. at 493–94. In that connection, ADEC noted

that “Congress nowhere suggested that the allocation of proof

burdens would differ depending upon which enforcement

route EPA selected.” Id. at 493 (emphasis added). 

Petitioners in this case, however, challenge not an EPA

enforcement action but the Final Rule disapproving in part

Arizona’s SIP submission. Such prospective administrative

agency rulemaking is ordinarily reviewed under the APA’s

arbitrary and capricious standard; there is no basis for

applying a different standard here.

In sum, Section 169A gives states substantial

responsibility in determining appropriate BART controls. 

EPA may not disapprove reasonable state determinations that

comply with the relevant statutory and regulatory

requirements. See Am. Corn Growers, 291 F.3d at 6–8. That

is, as ADEC put it, EPA may not “second guess” reasoned,

legally compliant state decisions. 540 U.S. at 490. But

Congress intended that EPA, not the states alone, ultimately

ensure that state determinations as to regional haze comply

with the Act, and so authorized EPA to disapprove state

“analysis that is neither reasoned nor moored to the [Act’s]

provisions.” N. Dakota, 730 F.3d at 761. Once the federal
ARIZONA EX REL. DARWIN V. USEPA 23

agency has done so, our role as the reviewing court remains

what it always is when substantively reviewing agency action

under the APA—deciding, with appropriate deference to the

federal agency, whether the agency’s action was “arbitrary,

capricious, an abuse of discretion, or otherwise not in

accordance with law.” 5 U.S.C. § 706(2).

B. Partial Disapproval of the SIP’s BART

Determinations

We now turn to Petitioners’ challenges to EPA’s partial

disapproval of Arizona’s SIP as it applies to the Coronado

BART determinations.

1. Arizona’s procedural claim

Before addressing Petitioners’ substantive arguments, we

address Arizona’s procedural argument. Arizona maintains

that, in acting only on the BART determinations when it

promulgated the Final Rule, deferring action on the rest of the

SIP, EPA “misconstrued its statutory authority and acted in

an arbitrary fashion.” Specifically, Arizona contends that

EPA cannot properly evaluate BART determinations

separately from the broader reasonable progress analysis,

because BART determinations are just one aspect of

achieving Section 169A’s overall “reasonable progress” to

the natural visibility goal. 42 U.S.C. § 7491(b)(2).

That is not so. There is no requirement that EPA approve

or disapprove a SIP submittal in a single action. To the

contrary, the Act expressly permits EPA to approve or

disapprove a SIP “in part.” 42 U.S.C. § 7410(c)(1), (k)(3);

see also Ass’n of Irritated Residents v. EPA, 423 F.3d 989,

997 (9th Cir. 2005).
24 ARIZONA EX REL. DARWIN V. USEPA

The EPA rule partially disapproving a regional haze SIP

which was recently upheld by Oklahoma, 723 F.3d at 1206,

for example, “t[ook] no action on whether Oklahoma has

satisfied the reasonable progress requirements.” 76 Fed. Reg.

81,728, 81,730 (Dec. 28, 2011). Under the Haze Regulations,

SIPs must contain reasonable progress goals, 40 C.F.R.

§ 51.308(d)(1), as well as source-specific BART

determinations, id. § 51.308(e)(1).12 Of course, the

implementation of the BART determinations will ultimately

contribute toward meeting the reasonable progress goals. But

the Act sets out standards for BART that are freestanding,

source-by-source, and not dependent on the long term

visibility goals identified. EPA did not act arbitrarily by

considering Arizona’s BART determinations separately from

the State’s reasonable progress analysis.

2. Arizona’s substantive claims

Turning to the substance of the Final Rule: EPA found

that the SIP’s “overall approach” was “generally reasonable

and consistent” with the Haze Regulations and the

Guidelines.1377 Fed. Reg. at 42,840. But it concluded that

the State’s BART determinations were deficient in three

particular respects. First, Arizona’s control cost calculations

12 As Arizona argues, in “some circumstances” BART controls may not

be “necessary to make reasonable progress.” But that is so when states

elect to implement an “emissions trading program or other alternative

measure,” that result in “greater reasonable progress” than BART. Id.

§ 51.308(e)(2) (emphasis added). Here, the State did not submit an

alternative measure under § 51.308(e)(2), choosing instead to conduct a

source-specific BART analysis.

 

13 Petitioners do not challenge the Haze Regulations or the Guidelines,

only their implementation in the Final Rule here at issue.
ARIZONA EX REL. DARWIN V. USEPA 25

were not performed in accordance with the Guidelines and

were otherwise unreasonable. See id. at 42,841; 77 Fed. Reg.

at 72,516–18, 72,566. Second, Arizona did not properly

evaluate the visibility improvements to all Class I areas. See

77 Fed. Reg. at 42,841–42; 77 Fed. Reg. at 72,519, 72,566. 

And third, Arizona inadequately explained its consideration

of the BART factors. See 77 Fed. Reg. at 42,841, 42,846; 77

Fed. Reg. at 72,517, 72,566. Because of these deficiencies,

EPA partially disapproved Arizona’s BART determinations,

including those pertaining to Coronado’s NOX emission

controls.

Arizona and SRP contend that each of EPA’s conclusions

is legally flawed and unsupported by the record. 

Consequently, they contend, the agency’s partial disapproval

of the SIP was arbitrary and capricious. We disagree. EPA’s

conclusions concerning the State’s BART analysis and

determinations were well explicated, carefully grounded in

the administrative record, and analytically reasonable, and so

properly support its disapproval of Arizona’s NOX BART

determinations for Coronado.

(i) The SIP’s Cost Analysis

As one of the BART factors, states must consider the

“costs of compliance.” 42 U.S.C. § 7491(g)(2); 40 C.F.R.

§ 51.308(e)(1)(ii)(A). “States have flexibility in how they

calculate costs.” Haze Regulations, 70 Fed. Reg. at 39,127. 

A state’s cost calculations are critical to determining a BART

control’s “cost effectiveness,” where “‘effectiveness’ is

measured in terms of tons of pollutant emissions removed,

and ‘cost’ is measured in terms of annualized control costs.” 

Id. at 39,167.
26 ARIZONA EX REL. DARWIN V. USEPA

After identifying control alternatives and achievable

emissions performance levels, states are directed to “develop

estimates of capital and annual costs.” Id. at 39,166. “The

basis for equipment cost estimates also should be

documented, either with data supplied by an equipment

vendor . . . or by a referenced source (such as the [Office

of Air Quality Planning and Standards] Control Cost

Manual . . . ).” Id.

The Guidelines instruct that the Cost Manual “addresses

most control technologies in sufficient detail for a BART

analysis,” and that “cost estimates should be based on the

[Cost Manual] where possible” to “maintain and improve

consistency.” Id. States are allowed by the Guidelines to

include “additional information” — such as “any information

supplied by vendors that affects your assumptions regarding

purchased equipment costs, equipment life, [or] replacement

of major components” — in their cost calculations, but

require them to provide documentation for any “element of

the calculation that differs from the . . . Cost Manual.” Id.

n.15. Finally, the Guidelines indicate that “[t]he cost analysis

should also take into account any site-specific design or other

conditions . . . that affect the cost of a particular BART”

option. Guidelines at 39,166.

In its proposed rule, EPA found “certain aspects” of

Arizona’s cost calculations “inconsistent” with the Guidelines

and Cost Manual and “disagree[d] with the manner in which

[Arizona]interpreted the cost-related information included in

its [] SIP.” 77 Fed. Reg. at 42,841. With regard to Coronado,

specifically, EPA noted in its proposed rule that SRP

“provided summaries of total control costs, such as total

annual operating and maintenance costs and total annualized

capital cost, but did not provide cost information at a level of
ARIZONA EX REL. DARWIN V. USEPA 27

detail that included line item costs.” Id. at 42,850. This

omission meant that SRP did not provide Arizona “with

control cost calculations at a level of detail that allowed for

a comprehensive review.” Id. at 42,851. As a result, EPA

explained, it “[did] not believe that [Arizona] was able to

evaluate whether SRP’s control costs were reasonable.” Id.

Arizona’s BART analysis was therefore inadequate because

it “did not properly consider the costs of compliance for each

control option.” Id.

We conclude that EPA’s disapproval of the cost analysis

underlying Arizona’s BART determination for Coronado on

that basis was not “arbitrary, capricious, [or] an abuse of

discretion.” 5 U.S.C. § 706(2)(A). Arizona simply relied on

the cost data provided by SRP, despite the fact that the data

failed to include sufficient detail for the State meaningfully

to analyze the reasonableness of the costs of various control

alternatives. States are required by statute to consider “costs

of compliance” in making BART determinations. 42 U.S.C.

§ 7491(g)(2). When they are not presented with enough data

to do so, EPA may reasonably conclude that their analysis is
28 ARIZONA EX REL. DARWIN V. USEPA

inadequate.14 EPA’s decision to do so was not arbitrary or

capricious.

(ii) The SIP’s Visibility Analysis

As part of its BART analysis, a state must analyze “the

degree of improvement in visibility which may reasonably be

anticipated to result from the use” of alternative control

technologies. 40 C.F.R. § 51.308(e)(1)(ii)(A). EPA found no

problems with the “technical adequacy of [Arizona’s

visibility] modeling.” 77 Fed. Reg. at 72,519. Rather, EPA

found Arizona’s interpretation of the visibility modeling for

all three plants “problematic.” Id. The problems, EPA

contends, resulted in Arizona understating the visibility

benefits associated with installing SCR at Coronado. We

conclude that EPA’s assessment of Arizona’s visibility

analysis considered the appropriate factors rationally, and so

defer to its conclusions. See Motor Vehicle Mfrs., 463 U.S.

at 43.

14 EPA also disapproved the cost analysis for failing to use the

“overnight method” required by the Cost Manual. The “overnight”

method “treats the costs of a project as if the project were completed

‘overnight,’ with no construction period and no interest accrual.” 77 Fed.

Reg. at 72,530. “Since assets under construction do not provide service

to current customers,” utilities for ratemaking purposes use an alternative,

“levelized” methodology, to “capitalize[] the interest and return on equity

that would accrue over the construction period and adds them to the rate

base when construction is completed and the assets are used.” Id.

Because EPA had a sufficient alternative basis for disapproving the

Coronado cost analysis, we do not here decide whether it could require

Arizona to employ the overnight method. We discuss EPA’s use of the

overnight method in its FIP infra, at 39–40.
ARIZONA EX REL. DARWIN V. USEPA 29

For Coronado, Arizona used a “visibility index”

averaging the visibility benefits at the closest nine Class I

areas, but did not evaluate such benefits separatelyat the most

impacted Class I area, the Gila Wilderness Area. 77 Fed.

Reg. at 72,519; see also 77 Fed. Reg. at 42,850–51. EPA’s

regulations “do not prescribe a particular approach to

calculating or considering visibility benefits across multiple

Class I areas,” 77 Fed. Reg. at 42,841; states have the

“flexibility to assess visibility improvements due to BART

controls by one or more methods,” Guidelines at 39,170. The

indexing approach therefore “could be acceptable in itself as

part of assessing multiple area impacts and improvements.” 

77 Fed. Reg. 72,519. But, EPA concluded, “without any

consideration of particular area improvements, the averaging

process causes especially large benefits at some individual

areas to be diluted or lost, effectively discounting some of the

more important effects of the controls.” Id. (emphasis

added).

Moreover, regardless of the methodology used, EPA

maintains, Arizona’s visibility analysis in its SIP was

unreasonable because it used “two contrasting, yet

equally incomplete, approaches to assessing visibility

improvements.” Arizona used a visibility index average to

analyze visibility benefits at Coronado, but its analyses for

Apache and Cholla considered visibility improvements “only

at the single Class I area with the greatest modeled impact

from a facility,” rather than at all impacted Class I areas. 

77 Fed. Reg. at 72,519. That is, the cumulative averaging

approach taken by Arizona in its analysis for Coronado “is

counter to [Arizona’s] emphasis elsewhere in the SIP on the

importance of considering the visibility improvement at the

single area having the largest impact from a given facility.” 

Id. The upshot is the appearance that the State selectively
30 ARIZONA EX REL. DARWIN V. USEPA

chose for each plant a methodology that minimized the

visibility improvement achieved by the more stringent

emission controls at each location.

Arizona made no attempt in its SIP, nor in its briefing in

this appeal, to counter this appearance by explaining why it

chose differing approaches to visibility analysis for different

facilities. SRP may be correct that “[t]he Guidelines allow

states to use either or both approaches.” But, as described

above, a state must include in its SIP “an explanation of the

CAA factors that led [the State] to choose that option over

other control levels.” Guidelines at 39,170–71 (emphasis

added). Adopting inconsistent — indeed, contradictory —

approaches without providing any explanation for that

decision frustrated EPA’s ability to “review the substantive

content of the BART determination.” N. Dakota, 730 F.3d at

761.

Arizona also contends that the outcome of its BART

determinations would not have changed even if it had adopted

the approach to visibility analysis EPA prescribed. The

visibility improvements resulting from installing SCR, the

State maintains, would in any event be “imperceptible” to the

human eye.

EPA expressly, and reasonably, rejected this argument

when it promulgated the Haze Regulations and Guidelines in

2005:

Even though the visibility improvement from

an individual source may not be perceptible,

it should still be considered in setting BART

because the contribution to haze may be

significant relative to other source
ARIZONA EX REL. DARWIN V. USEPA 31

contributions in the Class I area. Thus, we

disagree that the degree of improvement

should be contingent upon perceptibility. 

Failing to consider less-than-perceptible

contributions to visibility impairment would

ignore the CAA’s intent to have BART

requirements apply to sources that contribute

to, as well as cause, such impairment.

70 Fed. Reg. at 39,129.

In sum, EPA rationally determined that Arizona’s BART

visibility analysis for Coronado was unsupported by

explanation and inconsistent with the CAA and its

regulations. We defer to its conclusions.

(iii) The SIP’s Choice of BART

EPA’s Guidelines require states to support their BART

determinations with “documentation for all required

analyses,” including explanations of their BART five-factor

analysis. 40 C.F.R. § 51.308(e)(1). Further, the Guidelines

indicate that states “should provide a justification for

adopting the technology . . . select[ed] as the ‘best’ level of

control, including an explanation of the [Act’s] factors that

led [the State] to choose that option over other control

levels.” Guidelines at 39,170–71 (emphasis added). A state

need not perform this analysis if a source already has, or has

committed to installing, the most stringent controls available. 

Id. at 39,165. Otherwise, as EPA explained in proposing the

Rule here at issue, “[s]tates are free to determine the weight

and significance assigned to each factor, but must consider all

five factors and provide a reasoned explanation for adopting

[BART].” 77 Fed. Reg. at 42,838 (emphasis added).
32 ARIZONA EX REL. DARWIN V. USEPA

In the Final Rule, EPA concluded that, although Arizona

“presented information relevant to each of the BART factors”

and “expressly stated” that it had considered those factors, it

did not “provide[] an explanation regarding how this

information was used to develop its BART determinations.” 

77 Fed. Reg. at 72,517; see also id. at 72,566 (“[Arizona] has

not demonstrated that it actually took into consideration the

BART factors in making its determinations[.] . . . [I]t gave no

explanation or rationale for how it reached a determination

based on that information.”). More specifically, EPA found

that Arizona did not discuss how the results of the visibility

index were weighed against the other BART factors for

Coronado. Id. at 72,518; 77 Fed. Reg. at 42,851. Further,

EPA noted that while the SIP includes cost data, it “provides

no explanation regarding how, or even if, th[e] cost

information was used in arriving at its NOX BART

determinations.” 77 Fed. Reg. at 72,517. Indeed, “[i]n the

case of . . . Coronado, the . . . SIP does not analyze th[e] cost

information in even a qualitative manner.” Id.

A review of Arizona’s BART Technical Support

Document supports EPA’s analyses with regard to Coronado. 

Arizona’s ultimate determination was that, “[a]fter reviewing

the BART analysis provided by the company, and based upon

the information above . . . BART control at [Coronado] for

NOXis . . . Low NOX burners with OFA” with an emission

rate of 0.32 lbs/mmBtu. Before announcing that decision,

Arizona provided several charts of data concerning the

various controls’ cost-effectiveness and visibility impacts. 

But, having done so, it provided no reasoning or rationale to

justify its ultimate BART selection. There was simply

no attempt made to explain why the State chose one

control technology over another, or how it evaluated the

various BART factors (i.e., cost-effectiveness, visibility
ARIZONA EX REL. DARWIN V. USEPA 33

improvement, energy and non-air quality environmental

impacts, existing pollution control technology in use, and the

remaining useful life of the source), either individually or in

combination.

Indeed, Arizona does not meaningfully contest EPA’s

adverse characterization of its BART analysis. Rather, it

contends that “no great explanation is required to understand

the State’s decision not to spend hundreds of millions of

dollars of its citizens’ money for an imperceptible

improvement in visibility.” Yet, under the Act and its

implementing regulations, states are required in SIPs to

explain the choice of BART, taking into account not only cost

and visibility improvement, but also the three other BART

factors. See 40 C.F.R. § 51.308(e)(1)(ii)(A); Guidelines at

39,170–71.

We recently invalidated a FIP in part because EPA’s

conclusory cost-benefit analysis “fail[ed] to reveal to a reader

how EPA determined that the cost of controls were not

justified.” NPCA, 788 F.3d at 1145. The same failure here,

albeit by a state in its SIP, fares no better. Although the Act

affords states significant discretion in determining the

appropriate levels of BART controls, EPA must review

whether a state’s determinations comply with the statute and

its rules. See N. Dakota, 730 F.3d at 761; Oklahoma,

723 F.3d at 1209. Just as we could not in NPCA review

EPA’s cost/benefit analysis absent any coherent agency

analysis, EPA reasonably determined that it could not

meaningfully review Arizona’s parallel determination,

because the State did not provide an adequate explanation of

its underlying analysis, if any. Cf. 40 C.F.R.

§ 51.308(e)(1)(ii)(A); Guidelines at 39,170–71.
34 ARIZONA EX REL. DARWIN V. USEPA

In sum, EPA’s conclusion that Arizona did not adequately

explain its NOX BART determinations provides reasonable

support for its partial disapproval of Arizona’s SIP. We

therefore defer to EPA’s determination.

(iv) Conclusion

EPA reasonably concluded that Arizona’s cost and

visibility impact analyses for Coronado suffered from

significant analytical defects and that the SIP did not provide

a reasoned explanation of the bases for the ultimate BART

determination for Coronado. Although Section 169A affords

the states substantial authority to determine BART controls,

the combination of these defects provided EPA reasonable

grounds upon which to disapprove the Arizona’s BART

determinations as to NOX emissions limits at Coronado. Its

partial disapproval of the SIP in this respect was not arbitrary

or capricious.

C. EPA’s Promulgation of the FIP

To remedy the deficiencies it identified in its partial

disapproval of Arizona’s SIP, EPA in the same Final Rule

promulgated a FIP. As relevant here, EPA concluded that

selective catalytic reduction with low-NOX burners and

overfire air, “the most stringent available control option” for

NOX emissions, was BART for Coronado. 77 Fed. Reg. at

42,864. It thus proposed NOX emission limits of 0.05

lb/mmBtu, based on a rolling 30-boiler-operating day

average,

15

for Coronado. Id. at 42,865. After receiving

 

15

“Boiler operating day means a 24–hour period between 12 midnight

and the following midnight during which any fuel is combusted at any

time in the steam-generating unit. It is not necessary for fuel to be
ARIZONA EX REL. DARWIN V. USEPA 35

comments on its proposed rule, EPA’s Final Rule imposed a

FIP containing revised NOX emission limits of 0.065

lb/mmBtu, measured as an average of the two Coronado

generating units. See 77 Fed. Reg. at 72,514–15. This final

emission limit is, of course, very significantly more stringent

than the 0.32 lb/mmBtu NOX limit proposed by Arizona in its

SIP. As required by the Guidelines, EPA explained its

general analytical approach and BART determinations at

substantial length in the Final Rule. See id. at 72,526–35.

SRP presses a number of substantive challenges to the

FIP’s emission limit, as well as to EPA’s analysis underlying

that determination. Arizona, on the other hand, challenges

EPA’s decision to promulgate a FIP in the same rule in which

it disapproved in part Arizona’s SIP. We address these

challenges in turn.

1. The FIP’s BART Determinations

Under Section 169A and the Haze Regulations, EPA must

perform the same BART analysis when promulgating a

regional haze FIP as that performed by states in developing

SIPs. See 42 U.S.C. § 7491(b)(2)(A), (g)(2); see also 40

C.F.R. § 51.308(e)(1)(ii)(A)–(B). Challenges to the FIP are

reviewed “under the same arbitrary and capricious standard

. . . used to evaluate the EPA’s rejection of the SIP.” 

Oklahoma, 723 F.3d at 1215. But this review requires a

“slightly different perspective,” as we “evaluat[e] the EPA’s

own choices under the guidelines, as opposed to evaluating its

combusted the entire 24–hour period.” 40 C.F.R. § 60.41. At the end of

each boiler operating day, emissions are measured and a new 30-day

rolling average is calculated. See 40 C.F.R. § 60.48Da(b).
36 ARIZONA EX REL. DARWIN V. USEPA

choice to reject [Arizona’s] SIP under the guidelines.” Id.

(emphasis added).

SRP contends that EPA’s cost and visibility analyses

contained in its FIP were arbitrary and capricious. It also

maintains that, for a number of reasons, the FIP’s NOX

emission limits are neither achievable nor reasonable. 

Consequently, it argues, the FIP’s BART determinations for

Coronado were, on the whole, arbitrary and capricious. For

the reasons set forth below, we in the main do not agree, but

we leave one issue open because EPA is reconsidering it.

a. EPA’s Visibility Analysis

SRP first disputes EPA’s “cumulative” approach. EPA

estimated the visibility improvements that would occur at

each of the Class I areas potentially impacted by Coronado’s

emissions and then aggregated those improvements. SRP

contends this analysis resulted in “a large deciview number”

that does not represent the actual perception of visibility

conditions at any particular Class I area. SRP’s challenge to

EPA’s visibility improvement analysis suffers from two

substantial defects.

First, EPA considered the “cumulative visibility

improvement” resulting from various control technologies

“[a]s a supplement” to considering deciview improvements

at individual Class I areas. For Coronado, specifically, EPA

explained that modeling showed that SCR control technology

would result in visibility benefits at each of eleven Class I

areas—including the Gila Wilderness Area, which EPA

faulted Arizona for failing to consider—as well as on a

cumulative basis. See 77 Fed. Reg. at 42,863 tbl.23. In

response to Petitioners’ comments critiquing EPA’s
ARIZONA EX REL. DARWIN V. USEPA 37

cumulative approach, EPA explained in the Final Rule that

“[t]he approach is simply one wayof assessing improvements

at multiple areas, for consideration along with other visibility

metrics.” 77 Fed. Reg. at 72,532. SRP’s claim that EPA

“focused on this [cumulative] methodology almost

exclusively” is simply not supported by the record.

Second, SRP’s insistence on “human perception” as the

determinative “cornerstone” for the BART determinations for

each individual source is overstated. As discussed above,

when promulgating the BART Guidelines, EPA explicitly

disagreed “that the degree of improvement should be

contingent upon perceptibility” when determining BART for

an individual source. 70 Fed. Reg. at 39,129.

EPA’s Final Rule provided a fully adequate explanation

of its application of the deciview concept in the FIP. Again,

one deciview is the minimum visibility difference people can

perceive. See Guidelines at 39,120 n.32. The Guidelines

suggest that states use a minimum threshold of 0.5 deciviews

to determine whether a source is subject to BART controls. 

EPA explained in its Final Rule, however, that “[s]maller

improvements from controls should be considered in BART

determinations, since they can be beneficial in considering

effects from controls on multiple sources.” 77 Fed. Reg. at

72,533 (emphasis added).

In conclusion, EPA’s visibility improvement assessment

was consistent with the statute and regulatory requirements,

and supported by the record.
38 ARIZONA EX REL. DARWIN V. USEPA

b. EPA’s Cost Analysis

SRP also challenges EPA’s cost analysis, arguing that it

“diverged” from the Guidelines and was “inadequate” to

support its BART determinations for NOX emissions. 

Additionally, SRP argues that EPA’s cost assessment was

flawed “because [EPA] insisted on rigid adherence to the

[Cost Manual] irrespective of site-specific costs.”

EPA explains that it used the “air pollution control cost

development” component of the Integrated Planning Model

(“IPM”) to develop its cost estimates. See 77 Fed. Reg. at

72,530. IPM, a model of the United States electric power

sector, “relies upon a very large number of data inputs and

provides forecasts” of costs and other variables relevant to

decisionmaking in that sector. Id. SRP maintains that by

using IPM cost estimates, EPA ignored the Coronado

facility’s “site-specific characteristics,” and so understated

the actual costs of compliance for installing controls at

Coronado.

In the Final Rule, however, EPA explained that it did not

rely on IPM as a whole, but rather on “one component of

IPM, specifically, the component that develops the costs of

air pollution control technologies.” Id. As EPA explained,

that cost development methodology was not “generic” or

“generalized.” Id. Rather, it was grounded in databases of

actual SCR projects from 2004, 2006, and 2009. Id. At the

same time, EPA recognized that “a costly engineering

evaluation that included site visits would potentially produce

a more refined cost estimate that could be considered more

site-specific than our own.” Id.
ARIZONA EX REL. DARWIN V. USEPA 39

In addition, in response to Petitioners’ public comments

contending that EPA failed to consider site-specific

information, EPA conducted supplemental cost analyses that

relied upon “cost estimates provided by SRP.” See id. at

72,558–60. Based on this supplemental cost analysis, EPA

concluded that “the cost-effectiveness values of SCR . . . [are]

not . . . cost-prohibitive” for Coronado. Id. at 72,560.

Not satisfied, SRP contends that in its supplemental

analysis, “EPA excluded costs it deemed inconsistent with the

[Cost Manual]” such as Allowance for Funds Utilized During

Construction (“AFUDC”).16 This argument restates

Petitioners’ objections to EPA’s reliance on the overnight

costing methodologywhen it partially disapproved Arizona’s

SIP. See supra note 14. EPA’s use of such a methodology in

its own FIP’s cost analysis is, without doubt, reasonable. See

77 Fed. Reg. at 72,518.

In rejecting Arizona’s SIP, EPA explained that the use of

the overnight method was “crucial to [its] ability to assess the

reasonableness of the costs of compliance.” Id. The agency

went on:

A proper evaluation of cost-effectiveness

allows for a reasoned comparison not only of

different control options for a given facility,

but also of the relative costs of controls for

similar facilities. If the cost-effectiveness of

a control technology for a particular facility is

outside the range for other similar facilities,

16

 “AFUDC primarily represents a tool for utilities to capture their cost

of borrowing and return on equity during construction periods.” 77 Fed.

Reg. at 72,531.
40 ARIZONA EX REL. DARWIN V. USEPA

the control technology may be rejected as

not cost-effective. . . . Without an

‘apples-to-apples’ comparison of costs, it is

impossible to draw rational conclusions about

the reasonableness of the costs of compliance

for particular control options. Use of the

[Cost Manual] methodology is intended to

allow a fair comparison of pollution control

costs between similar applications for

regulatory purposes.

Id. EPA concluded that “it is reasonable for us to insist that

the [Cost Manual] methodology be observed in the cost

estimate process.” Id. Accordingly, it rejected comments

that items like AFUDC should have been incorporated into its

cost analysis, as they were “inconsistent with [the Cost

Manual] methodology.” Id. at 72,531.

EPA’s analysis is reasonable. The purpose of the cost

analysis required as part of a BART determination is to foster

comparison of the cost of the visibility improvements enabled

by various control technologies. As EPA’s comments

indicate, cross-facility comparisons of similar sources with

regard to the cost-effectiveness of a given control option aid

in determining cost-effectiveness at a specific source. 

Control options are likely to impact similar sources similarly;

comparisons assure that the cost and benefit figures used for

a particular site are realistic, rather than inflated in one

direction or another. Consideration of AFUDC would not

further this inquiry, as AFUDC is ultimately reflective of the

implementing entity’s financial and logistical situations,

grounded in past decisions and in the company’s financial

policies and attitudes, not of the hard costs of the equipment

and construction, which should be consistent across sites. 
ARIZONA EX REL. DARWIN V. USEPA 41

While AFUDC and similar concepts are relevant for sales and

ratemaking, including them would undermine the sort of

“apples-to-apples” comparison that EPA asserts is necessary

as part—but only part—of assessing the control options.

This approach is consonant with the Guidelines, which

specifically advise that “reasonable range[s]” for cost

effectiveness are those that are “consistent with the range of

cost effectiveness values used in other similar permit

decisions over a period of time.” Guidelines at 39,168; see

also Oklahoma, 723 F.3d at 1213 (“The guidelines say that

states should follow the manual’s methodology so that

projects can be more easily compared.”). Moreover, adopting

a costing methodology which focuses on achieving

consistencyand facilitating comparisons aligns with the CAA

itself, which empowers EPA to promulgate national

regulations concerningBART determinations. See 42 U.S.C.

§ 7491(a)(4), (b)(1).

Accordingly, we reject SRP’s argument that the FIP’s

underlying cost analysis was arbitrary and capricious.

c. Achievability of the FIP’s NOX emission limits for

Coronado

The Haze Regulations provide that the BART

determination “must be based on an analysis of the best

system of continuous emission control technology available

and associated emission reductions achievable for each

BART-eligible source that is subject to BART.” 40 C.F.R.

§ 51.308(e)(1)(ii)(A) (emphasis added). The reviewing

authority should “take into account the most stringent

emission control level that the technology is capable of

achieving,” by considering “recent regulatory decisions and
42 ARIZONA EX REL. DARWIN V. USEPA

performance data (e.g., manufacturer’s data, engineering

estimates and the experience of other sources).” Guidelines

at 39,166.

SRP argues that the FIP’s NOX emission limit for

Coronado — 0.065 lb/mmBtu averaged across the facility—

is not achievable. More specifically, it argues that (1) the

emission limits are technically infeasible; and (2) EPA did

not take into account the Consent Decree binding Coronado

Unit 2 when formulating the emission limits.

Both of these arguments will be rendered moot if EPA’s

recent action proposing to revise the FIP’s NOX emission

limit for Coronado results in a final revised FIP consistent

with the proposal. See 80 Fed. Reg. 17,010 (March 31,

2015).17 The proposed revision would replace the facilitywide compliance method with “a unit-specific compliance

method for determining compliance with . . . BART []

emission limits for nitrogen oxides,” and would establish

“unit-specific limit[s]” of 0.065 lb/mmBtu for Coronado Unit

1 and 0.080 lb/mmBtu for Coronado Unit 2. Id.

SRP’s technical feasibility argument was largelybased on

the assertion that a 0.050 lb/mmBtu emissions limit — which

SRP contended Coronado Unit 1 would have to satisfy —

was “infeasible” for SCR retrofits to coal-fired electric

generating units. Even though EPA based its BART

determinations for Coronado on modeling showing that SCR

controls could achieve a 0.050 lb/mmBtu NOX emission rate

with an 80%–90% control efficiency, see 77 Fed. Reg. at

42,853, and has imposed a NOX emission limit in the 0.050

17 EPA has recently informed us that it expects to issue the final revised

FIP by March 2016.
ARIZONA EX REL. DARWIN V. USEPA 43

lb/mmBtu range in other, similar rulemakings, see 77 Fed.

Reg. at 72,544 tbl.7, the proposed revised FIP’s limits for

Coronado Unit 1 are now 0.065 lb/mmBtu.18 Likewise,

although SRP initially argued that the FIP’s emission limits

were inconsistent with the limits prescribed by a pre-existing

Consent Decree as to Coronado Unit 2, EPA’s proposed FIP

revision establishes the same emissions limit as that

prescribed by the Consent Decree: 0.080 lb/mmBtu. See

80 Fed. Reg. at 17,016–18. Consequently, these arguments,

whatever merit they may have had as to the original FIP, will

not carry force if the proposed revised FIP is adopted.

Additionally, SRP argues that the FIP’s emissions limits

are in conflict with EPA’s own “presumptive” limits. The

BART Guidelines provide a list of “presumptive NOXlimits,”

based on boiler and coal type, for certain coal-fired

generating units operating without post-combustion controls. 

Guidelines at 39,171. Under the Guidelines, the reviewing

authority “should require such [facilities] to meet the

[presumptive] NOX emission limits, unless [it] determine[s]

that an alternative control level is justified based on

consideration of the statutory factors.” Id. The presumptive

NOX

 limits for Coronado are 0.32 lb/mmBtu for bituminous

coal and 0.23 lb/mmBtu for sub-bituminous coal. Id. tbl.1. 

Arizona’s SIP proposed a NOX emission limit for Coronado

within the presumptive limit range, while the FIP imposes a

far lower facility-wide limit. SRP argues that EPA, unlike

Arizona, did not consider the presumptive limits, and

therefore violated the Guidelines.

18 A 0.065 lb/mmBtu emissions limit may also be, in SRP’s view,

technically infeasible, and SRP is entitled to petition for review of EPA’s

action finalizing the FIP revision when it is issued. See 42 U.S.C.

§ 7607(b).
44 ARIZONA EX REL. DARWIN V. USEPA

As the Final Rule explains, EPA did consider the

presumptive limits but found there is “no single presumptive

NOXlimit that applies to any of these units,” as each of the

facilities “historically burned both bituminous and subbituminous coal.” 77 Fed. Reg. at 72,529. Accordingly, EPA

instead “considered the technological basis for presumptive

NOX BART limits . . . as part of the five-factor analysis [it]

performed for each facility.” Id.

In any event, SRP’s argument that the “law requires [the

presumptive] limits to be taken into account in any BART

determination” is belied by the Guidelines. The presumptive

emission limits are “rebuttable” and “do[] not preclude states

or EPA from setting limits that differ from those

presumptions.” 77 Fed. Reg. at 72,529. Instead, the

Guidelines expressly allow for an alternative control level to

be formulated based on the statutory factors, provided that the

alternative limits are based on a reasoned BART analysis. 

70 Fed. Reg. at 39,171. Moreover, the presumptive emission

limits are presumed to be cost-effective, not presumed to be

BART in every case. See 77 Fed. Reg. at 51,620, 51,633

(Aug. 24, 2012); 77 Fed. Reg. 14,604, 14,665 (Mar. 12,

2012).

In sum, EPA acted reasonably in departing from

Guidelines’ rebuttable presumptive limits. But, because EPA

has not yet completed its proposed revised FIP, we decline to

rule on the reasonableness of its emissions limits, as they are

likely to be altered. This aspect of these proceedings is

therefore stayed until EPA concludes the administrative

process and issues its final revised FIP.
ARIZONA EX REL. DARWIN V. USEPA 45

2. Simultaneous Disapproval of a SIP and

Promulgation of a FIP

Apart from its substantive challenges to the FIP, Arizona

contends that EPA procedurallyerred in promulgating the FIP

in the same rule as its partial disapproval of the SIP. That is

not so.

Under the Act, EPA shall promulgate a FIP “at any time

within 2 years” after EPA disapproves a SIP in whole or in

part or finds that a state has not made a required submission. 

42 U.S.C. § 7410(c) (emphasis added). A state may forestall

the promulgation of a FIP if it “corrects the deficiency, and

[EPA] approves the plan or plan revision, before [EPA]

promulgates such [FIP].” Id. Furthermore, a state may

submit a SIP revision to EPA at any time, and EPA must act

on it within twelve months of submission. Id. § 7410(k).

The Final Rule’s partial disapproval of Arizona’s BART

determinations constituted a trigger under the Act for

promulgating a FIP replacing those elements. The Act

expressly authorizes EPA to promulgate a FIP “at any time”

within two years of disapproving a SIP. “At any time,” of

course, includes simultaneously with the SIP’s disapproval. 

See Oklahoma, 723 F.3d at 1223.

Arizona ultimately recognizes that EPA had the authority

to promulgate the FIP simultaneously with its partial

disapproval, but maintains that EPA did not realize that it had

discretion to provide Arizona up to two years to correct any

deficiencies. EPA, Arizona posits, harbored the erroneous

belief that its obligations under the Consent Decree required

it to act when it did.
46 ARIZONA EX REL. DARWIN V. USEPA

Some procedural background is required to understand

the thrust of Arizona’s argument. After EPA did not

promulgate FIPs within two years of its January 2009 finding

that many states, including Arizona, had not submitted

required SIPs, it entered into a Consent Decree requiring the

federal agency to approve a SIP or promulgate a FIP by

November 15, 2012. See supra, p. 13–14. In the Final Rule,

EPA stated that the Consent Decree “required [it] to issue a

FIP for any portion of the Arizona SIP that we cannot

approve.” 77 Fed. Reg. at 72,569. EPA further explained

that “while . . . in the absence of an expired statutory duty and

a court-ordered deadline to issue a FIP, it would be preferable

for us to give Arizona additional time to revise its Regional

Haze SIP prior to promulgation of a FIP, we simply do not

have this option under these circumstances.” Id. at 72,571.

Arizona contends that the January 2009 finding

constituted only a determination that Arizona failed to submit

a Section 309 SIP, and that the correct remedy for Arizona’s

asserted deficiency “was to impose a FIP supplying the

missing Section 309 elements, not to impose a FIP under

Section 308, as it did here.” But, as we explained earlier, see

supra, p. 11–12, Section 309 provides an alternative

mechanism for western states to comply with the CAA’s

visibility requirements for certain Class I areas. Such states

must include Section 308 components for other Class I areas,

and they remain subject to Section 308’s requirements if they

do not submit a Section 309 SIP. See 40 C.F.R. § 51.309(a),

(e), (g)(2). Arizona expressly acknowledged that its Section

309 SIP submission lacked certain requirements under

sections 51.309(d)(4)(viii) and (g). Because the State did not

submit an adequate Section 309 SIP, it did not submit an

adequate regional haze SIP. EPA was required to promulgate
ARIZONA EX REL. DARWIN V. USEPA 47

a FIP to fill in the gap. See 42 U.S.C. §§ 7410(c)(1),

7491(b)(2)(A).

More practically, it is unlikely that a different outcome

would have resulted if EPA had provided Arizona with

additional time to correct its Section 308 SIP. EPA had

expressed a number of its concerns to Arizona after reviewing

its proposed SIP in late 2010. EPA also identified the basis

for its proposed partial disapproval in its July 2012 proposed

rule. Arizona made no effort to correct its SIP in light of

these comments. There is no reason to think it would have

done so after the Final Rule disapproving the SIP issued

either.

In sum, EPA properly promulgated its FIP in the same

rule as its partial disapproval of the SIP. Further, as EPA

stated in the Final Rule, the State remains free to, at any time,

“submit a revised SIP to replace the FIP.” 77 Fed. Reg. at

72,571.

IV. CONCLUSION

For the reasons set forth above, we deny Arizona’s and

SRP’s petitions for review of EPA’s Final Rule as to EPA’s

disapproval of Arizona’s SIP. Our ultimate review of EPA’s

FIP, however, must await EPA’s final action on its proposal

to revise the FIP in specific respects. As noted, EPA has

stated that it expects to finalize the revised FIP by March

2016. Accordingly we stay these proceedings as to

evaluation of the FIP’s technical feasibility until the

administrative process is complete.

PETITIONS DENIED.
48 ARIZONA EX REL. DARWIN V. USEPA

GLOSSARY OF ACRONYMS

AFUDC–Allowance for Funds Utilized DuringConstruction

APA – Administrative Procedure Act

CAA – Clean Air Act

BACT – Best Available Control Technology

BART – Best Available Retrofit Technology

EPA – Environmental Protection Agency

FIP – Federal Implementation Plan

IPM – Integrated Planning Model

LNB – Low NOX Burner

NOX – Nitrogen Oxides

OAQPS – Office of Air Quality Planning and Standards

OFA – Overfire Air

PSD – Prevention of Significant Deterioration

SCR – Selective Catalytic Reduction

SIP – State Implementation Plan

SO2 – Sulfur Dioxide
ARIZONA EX REL. DARWIN V. USEPA 49

SRP – Salt River Project Agricultural Improvement and

Power District