United States Court of Appeals

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued February 10, 2017 Decided July 18, 2017

No. 15-1246

SIERRA CLUB AND CALIFORNIA COMMUNITIES

AGAINST TOXICS,

PETITIONERS

v.

ENVIRONMENTAL PROTECTION AGENCY AND

E. SCOTT PRUITT, ADMINISTRATOR,

U.S. ENVIRONMENTAL PROTECTION AGENCY,

RESPONDENTS

On Petition for Review of Final Action of the 

United States Environmental Protection Agency

Neil Gormley argued the cause for petitioners. With him on

the briefs was James S. Pew.

Eileen T. McDonough, Attorney, U.S. Department of

Justice, argued the cause for respondents. With her on the brief

was John C. Cruden, Assistant Attorney General, was on the

brief.

Jeffrey A. Knight and Bryan M. Stockton were on the brief

for amicus curiae Coalition for Clean Air Implementation in

support of respondents.
2

Before: ROGERS and MILLETT, Circuit Judges, and

SENTELLE, Senior Circuit Judge.

Opinion for the Court filed by Senior Circuit Judge

SENTELLE.

SENTELLE, Senior Circuit Judge: Sierra Club and California

Communities Against Toxics (collectively “Sierra Club”)

petition for review of the Environmental Protection Agency’s

(“EPA”) determination that EPA had satisfied its responsibilities

under 42 U.S.C. § 7412(c)(6) to establish “maximum achievable

control technology” (“MACT”) standards for emissions of

certain hazardous air pollutants (“HAPs”). Petitioners contend

that as to three of the HAPs, EPA arbitrarily relied upon

standards set previously to regulate other emissions without

justifying its decision to treat those previously regulated

emissions as “surrogates” for the § 7412(c)(6) HAPs. EPA

moves the court to dismiss the petition as untimely and disputes

it substantively. Because we conclude that the petition is not

untimely and that EPA did not adequately respond to

petitioners’ comments raising the issues concerning the use of

surrogacyin the administrative proceedings, we deny the motion

to dismiss and order the matter remanded to EPA for further

proceedings.

I. BACKGROUND

Congress enacted the current version of § 7412 as part of

the Clean Air Act Amendments of 1990 to further its original

intent, “to reduce hazardous air pollutants.” See Sierra Club v.

EPA, 353 F.3d 976, 979 (D.C. Cir. 2004). In general, that

section requires MACT standards for “major source[s]” of air

pollutants, that is to say, those with potential to emit ten tons or

more of a single HAP or twenty-five tons or more of a

combination of HAPs per year. See 42 U.S.C. § 7412(a)(1)
3

(describing major sources); see also § 7412(d). Congress

singled out a category of specific pollutants of a particularly

hazardous nature for special treatment under § 7412(c)(6). With

respect to those pollutants, Congress required EPA, as pertinent

to this petition, to regulate emissions of seven specific hazardous

air pollutants more stringently than the statute required for

pollutants in general. Specifically, EPA was required to list

categories and subcategories of sources of such HAPs

accounting for at least 90% of the aggregate emissions of each. 

See § 7412(c)(6). EPA was further required to establish and

subject these listed sources to MACT standards, see id., even if

it would have otherwise had discretion to apply a less-stringent

standard to any area sources on the list, see § 7412(d)(5). The

statute specifically required EPA to conclude these duties by

November 15, 2000. § 7412(c)(6).

Much activity followed, both administratively and in

litigation. Although petitioners devote much ink to a rehash of

the years of proceedings, we will describe the intervening events

briefly, with only enough detail to support our decision in the

present controversy. As mentioned, in addition to the creation

of MACT standards, § 7412 required EPA to perform the

preliminary duty of listing sources of the seven specific HAPs. 

See § 7412(c)(6). “In 1998 EPA published its conclusion that it

had satisfied” that preliminary duty. Sierra Club v. EPA, 699

F.3d 530, 531 (D.C. Cir. 2012). Sierra Club petitioned this court

for review of that determination. We dismissed the petition as

premature, determining that the Clean Air Act “precluded

review of the agency’s source-listing under § [7412](c)(6) until

the agency had issued emissions standards thereunder . . . .” Id.

(explaining Sierra Club v. EPA, No. 98-1270, 1998 WL849408,

at *1 (D.C. Cir. Nov. 24, 1998), in which we dismissed the

petition, relying on 42 U.S.C. § 7412(e)(4)). 
4

Thereafter, when EPA failed to meet the November 2000

statutory deadline for promulgating the (c)(6) list and MACT

standards, Sierra Club brought a district court action to compel

compliance with the statute, which ultimately led to our 2012

decision in Sierra Club. After the district court had ordered the

agency to comply with its statutory duties, EPA issued a

determination that it had “completed sufficient standards to meet

the 90 percent requirement” of § 7412(c)(6). Sierra Club, 699

F.3d at 532 (citation omitted). Sierra Club petitioned for review. 

Then, as now, EPA moved for dismissal of the petition as

untimely. We disagreed. Id. at 532-34. We also concluded that

EPA had not complied with its duty to provide the period of

notice and comment. Id. at 534-35. We vacated and remanded

for further proceedings. Id. at 535.

Thereafter, EPA began administrative proceedings which

ultimately led to the final rule under review. More specifically,

at the time of our remand, the order that Sierra Club had

obtained from the district court was still outstanding. Sierra

Club moved the district court to enforce its prior order with

respect to several of the § 7412(c)(6) HAPs. Sierra Club v.

McCarthy, 61 F. Supp. 3d 35, 38-39 (D.D.C. 2014). The district

court, perceiving that EPA had not complied with its prior order,

“direct[ed] EPA to initiate a process of notice and comment

rulemaking before it reissues or, after consideration of the

comments submitted, reconsiders or modifies its

Determination.” Id. at 41. The court required that the final

action “include a statement explaining its basis” and required

EPA to “respond to the comments that it receive[d].” Id.

Subsequently, EPA published the notice of rulemaking and final

rulemaking that Sierra Club contests as arbitrary and capricious

in this case. 

Expressing its intent to comply with the district court’s

order, EPA issued this notice of proposed rulemaking entitled
5

“Completion of Requirement to Promulgate Emissions

Standards,” 79 Fed. Reg. 74,656 (Dec. 16, 2014) (“Proposed

Determination”). The notice expressly provided for comments,

as required in the district court’s 2014 order. Sierra Club filed

comments. As pertinent to the present controversy, EPA’s

proposed rule included three HAPs upon which Sierra Club’s

comments and present petition focus: polychlorinated biphenyls

(“PCBs”), polycyclic organic matter (“POM”), and

hexachlorobenzene (“HCB”).

As to each of the three HAPs, Sierra Club contends that

EPA’s final rule does not comply with the requirements of

§ 7412(c)(6) that as to every pollutant covered by the section,

EPA must provide sufficient standards for the categories and

subcategories of “sources accounting for not less than 90 percent

of the aggregate emissions of each such pollutant . . . .” 42

U.S.C. § 7412(c)(6). In terms of the issues preserved by

petitioners for review in this proceeding, Sierra Club’s main

argument is that the agency improperly relied on “surrogates.”

That is to say, rather than issuing new specific standards, the

agency relied on previously set emission limits for another

hazardous air pollutant or compound, “which serves as a

surrogate for the targeted section [7412](c)(6) [pollutant].” 

Proposed Determination, 79 Fed. Reg. at 74,677. After

receiving petitioners’ comments on its proposed rule, EPA

published the final rule now under review: “Completion of

Requirement to Promulgate Emissions Standards,” 80 Fed. Reg.

31,470 (June 3, 2015) (codified at 40 C.F.R. pt. 63) (“Final

Determination”). 

Sierra Club filed the present petition. EPA moved to

dismiss the petition as untimely. For the reasons set forth

below, we deny the motion to dismiss and grant remand for

further proceedings.
6

II. ANALYSIS

A. Standard of Review

EPA’s final rule is subject to judicial review under 42

U.S.C. § 7607(b)(1). We review such final rules under the

standards of the Administrative Procedure Act, 5 U.S.C.

§ 706(2), and will set the rule aside if it is “arbitrary, capricious,

an abuse of discretion, or otherwise not in accordance with law.” 

Id. § 706(2)(A). Insofar as the agency has interpreted the Clean

Air Act, we apply the standard of Chevron, U.S.A., Inc. v.

NRDC, 467 U.S. 837 (1984). That is, if “the intent of Congress

is clear,” that is the end of the analysis. Id. at 843-45. If it is

ambiguous, then we ask if the agency’s interpretation is

reasonable, and if so, we uphold the agency’s construction. Id.

In the present controversy, petitioners’ challenge is directed to

the decisions of EPA, not primarily to its interpretation of the

statute. 

B. Timeliness

EPA’s motion to dismiss is based on the argument that

Sierra Club’s objections to the standards used in the final

determination are actually challenges to “the adequacy of the

pre-existing standards,” that is, the MACT standards with

respect to the surrogate pollutants. Resp’ts’ Br. at 37. EPA

relies on the judicial review provision of the Clean Air Act,

which provides that any petition for review of the

Administrator’s promulgation of standards “shall be filed within

sixty days from the date notice of such promulgation, approval,

or action appears in the Federal Register . . . .” 42 U.S.C.

§ 7607(b)(1). We note that the statute further provides an

exception “if such petition is based solely on grounds arising

after such sixtieth day,” and that any such petition “shall be filed

within sixty days after such grounds arise.” Id. For reasons
7

similar to those set forth by us in Sierra Club v. EPA, 699 F.3d

530, we agree with petitioners.

In the prior decision, we held that “[i]f Sierra Club is

correct . . . the agency action Sierra Club challenges is only the

Determination, which (in its view) repurposed previous

rulemakings to satisfy EPA’s § [7412](c)(6) obligations,”

making the challenge “timely” as it “could not be brought at all

until after EPA identified the rules that it believed satisfied its

responsibilities under § [7412](c)(6).” Sierra Club, 699 F.3d at

534.

The same reasoning applies here. Sierra Club again

challenges the present determination that EPA had satisfied

§ 7412(c)(6) through its promulgation of MACT standards for

surrogate emissions rather than for the listed (c)(6) HAPs

themselves. That issue could not be reviewed prior to the

issuance of the final rule now before us. Petitioners could not

raise those objections until the final rule employing the

surrogates was released. Petitioners do not, for example, attack

the adequacy of the listing or standards with respect to any

surrogate pollutant, but only the repurposing of standards for

satisfaction of the § 7412(c)(6) requirements with respect to

PCBs, POM, and HCB. It is therefore clear that our reasoning

in Sierra Club applies equally to the present case. Sierra Club’s

present challenge to the interaction of the surrogacy decisions

with the 90% (c)(6) requirements is timely, and the motion to

dismiss will be denied.

C. The Substantive Petition

We wish to make clear at the outset that the question before

us is the narrow one of the adequacy of EPA’s justification for

the use of surrogates. Insofar as the parties characterize this

petition as a challenge to the achievement of the 90%
8

requirement, that question rises or falls with surrogacy. EPA

has published a purported 90% listing. However, the adequacy

of the MACT standards for the 90% requirement relies upon the

propriety of the use of the surrogates. As to those issues,

petitioners’ challenge is timely. This does not determine

whether it is meritorious. Petitioners raised their objections to

the use of the surrogates in comments. We have frequently held

in various contexts that, in APA review, we will often find

agency decisions arbitrary or capricious where the agency has

failed to respond to major substantive comments. See Pub.

Citizen, Inc. v. FAA, 988 F.2d 186, 197 (D.C. Cir. 1993)

(citations omitted); see also NRDC v. EPA, 859 F.2d 156, 188-

89 (D.C. Cir. 1988). In this case, the agency’s responses to the

comments consisted principallyof the same timeliness argument

we rejected above. Therefore, if we conclude that the

substantive comments raised meritorious issues unanswered by

EPA, then we must remand for further proceedings.

We have in the past approved the use of surrogates by EPA. 

We have ruled that “EPA may use a surrogate to regulate

hazardous pollutants if it is ‘reasonable’ to do so.” Nat’l Lime

Ass’n v. EPA, 233 F.3d 625, 637 (D.C. Cir. 2000) (citation

omitted). Therefore, Sierra Club does not argue, nor do we

hold, that surrogates may not be used. The question is whether

the current use of surrogates is reasonable. 

This Court has identified three potential tests for evaluating

the sufficiency of a surrogacy designation. National Lime

“established a three-part analysis for determining whether the

use of [a particular surrogate] for HAPs is reasonable . . . .” 

Sierra Club, 353 F.3d at 984. That three-part test requires EPA

to determine if (1) the relevant hazardous air pollutant is

invariably present in the proposed surrogate; (2) control

technologies for the proposed surrogate indiscriminatelycapture

the relevant HAP along with other pollutants; and (3) the control
9

of the surrogate is the only means by which facilities achieve

reductions in emissions of the hazardous air pollutant. See id.;

see also U.S. Sugar Corp. v. EPA, 830 F.3d 579, 628 (D.C. Cir.

2016) (The reasonableness inquiry “requires the surrogate’s

emissions to share a close relationship with the emissions of the

[target hazardous air pollutant].”); Mossville Envtl. Action Now

v. EPA, 370 F.3d 1232, 1242 (D.C. Cir. 2004) (The

reasonableness inquiry “merely requires ‘that there [be] a

correlation between [the surrogate and the target hazardous air

pollutants].’” (quoting Nat’l Lime, 233 F.3d at 639)). Applying

those standards, in Sierra Club, we held that the use of a

surrogate was reasonable. Sierra Club, 353 F.3d at 984-85. 

Even if the surrogates in the present case are different than a

specific surrogate considered in Sierra Club or in National Lime,

the three-part test is nonetheless instructive. 

In this context, as in the prior cases, EPA must demonstrate

the reasonableness of the use of a particular surrogate in a

specific context. Although EPA provided some explanation of

the surrogacy relationships in this case, see Proposed

Determination, 79 Fed. Reg. at 75,677-80, EPA failed to

respond adequately to comments disputing those explanations. 

In the proposed determination, EPA admits that “in some

standards promulgated prior to [its] development of the baseline

emissions inventory . . . , the EPA did not always explain the

surrogacy relationship.” Proposed Determination, 79 Fed. Reg.

at 74,678; see also Final Determination, 80 Fed. Reg. at 31,471-

72 (final determination noting that proposed determination

explained the surrogate standards). In the final determination,

it then proceeds to provide brief information on the newly

“explained” surrogacy relationships but does not substantively

respond to comments on those purported explanations, urging

instead that the relevant standards had not been reopened and

thus could not be substantively challenged. Despite comments

urging that EPA’s surrogacy claims needed additional analysis
10

and data in support to establish their reasonableness, EPA

responded that such comments “mischaracterize[d]” its

“proposed determination,” as “the legitimacy of the standards”

it relied on is “far outside the scope of the proposed”

determination. Final Determination, 80 Fed. Reg. at 31,477. 

Thus, EPA did not need “to respond to those comments.” Id.

EPA cannot hide behind the established nature of the

standards it uses when it applies new surrogacy relationships. 

Byadmitting that “the proposed determination in some instances

clarifies the surrogacy relationship,” EPA makes irrelevant its

point that “the proposal does not discuss or attest to the

substance of the standards previously promulgated.” See Final

Determination, 80 Fed. Reg. at 31,480. In its admission, EPA

belies its own claim that the determination was “only . . . the

mathematical and technical basis for the EPA’s calculation.” Id.

Providing brand-new clarification of some surrogacy

relationships necessarily rendered it substantive and EPA’s

failure to explain sufficiently these newly “clarified”

relationships and respond to the associated comments dooms the

current determination. While the parties make other arguments,

all are either restatements of the propositions contained in the

major issue or do not warrant separate discussion. We wish to

make clear that we are not holding that EPA’s decision is

substantively incorrect. Indeed we express no opinion on that

subject. We simply remand the matter to EPA for further

proceedings, which should include the explanations omitted

from the present determination.

CONCLUSION

For the reasons set forth above, we conclude that EPA

failed to explain its proposed reliance on surrogates and thus its

determination does not satisfy 42 U.S.C. § 7412(c)(6). We

therefore hold that Sierra Club’s timely petition for review is 

Granted in part.