Sierra Club v. Envtl. Prot. Agency

United States Court of Appeals

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued November 9, 2017 Decided July 6, 2018

No. 15-1487

SIERRA CLUB AND NATURAL RESOURCES DEFENSE COUNCIL,

PETITIONERS

v.

ENVIRONMENTAL PROTECTION AGENCY AND E. SCOTT

PRUITT,

RESPONDENTS

BRICK INDUSTRY ASSOCIATION, ET AL.,

INTERVENORS

Consolidated with 15-1492, 15-1493, 15-1496, 16-1179

On Petitions for Review of a Final Action of the

United States Environmental Protection Agency

James S. Pew argued the cause and filed the briefs for

Environmental petitioners.

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William L. Wehrum, Felicia H. Barnes, Todd E.

Palmer, Valerie L. Green, Cameron F. Field, Howard L.

Gilberg, Jean M. Flores, Jeffrey S. Longsworth, Charles M.

Denton, and Roger J. Marzulla were on the joint briefs for

Industry petitioners.

Kate R. Bowers, Attorney, U.S. Department of

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

were Sonya J. Shea, Attorney, and Sonja L. Rodman and Scott

J. Jordan, Attorneys, U.S. Environmental Protection Agency.

Felicia H. Barnes argued the cause for Industry

respondent-intervenors. With her on the joint brief were

William L. Wehrum Jr., Todd E. Palmer, Valerie L. Green,

Cameron F. Field, Jeffrey S. Longsworth, and Charles M.

Denton.

James S. Pew was on the brief for Environmental

respondent-intervenors.

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: In this consolidated

proceeding, we consider petitions for review of an

Environmental Protection Agency (“EPA”) final rule entitled

“NESHAP for Brick and Structural Clay Products

Manufacturing; and NESHAP for Clay Ceramics

Manufacturing,” 80 Fed. Reg. 65,470 (Oct. 26, 2015)

(“Brick/Clay Rule”), and its partial denial of reconsideration of

that rule, 81 Fed. Reg. 31, 234 (May 18, 2016).

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In Case No. 15-1487, petitioners Sierra Club and

Natural Resources Defense Council (collectively,

“Environmental Petitioners”) contend that the EPA erred in its

use of health-based standards for acid gas emissions, failed to

properly explain its methodology in setting maximum

achievable control technology-based standards, and

improperly allowed brick plants to meet alternative emissions

floors. In Case Nos. 15-1492, 15-1493, 15-1496, and 16-1179,

the Brick Industry Association, the Tile Council of North

America, Inc., and the Kohler Company (collectively,

“Industry Petitioners”) contend that the EPA made multiple

errors in its methodology in the Brick/Clay Rule.

Finally, the EPA moved to sever and hold in abeyance

the Industry Petitioners’ petition for review while it reconsiders

the Brick/Clay Rule. Industry Petitioners supported the

motion; the Environmental Petitioners opposed the motion to

hold the entire case in abeyance but not EPA’s motion to sever

and hold in abeyance the Industry Petitioners’ petition. See

Unopposed Mot. at 2, Doc. No. 1703072 (Filed Nov. 3, 2017).

We deferred consideration of the motion pending oral

argument. We now deny the motion and consider this case on

its merits. For the reasons stated below, we deny Industry

Petitioners’ petition for review and grant in part that of the

Environmental Petitioners and remand the Brick/Clay Rule to

the agency for further proceedings consistent with this opinion.

I. Background

Under the Clean Air Act (“CAA”), the EPA regulates

all major and area sources of hazardous air pollutants. 42

U.S.C. § 7412(d)(1). There are 189 hazardous air pollutants

subject to regulation under the CAA, including hydrogen

chloride, hydrogen fluoride, chlorine, and heavy metals such as

mercury. Id. § 7412(b)(1). During the regulatory process, the

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EPA identifies categories of sources that generate hazardous

air pollutants, and then sets emissions limits for each major

source category. Id. § 7412(c)(1)-(2), (d)(1).

The EPA found that kilns emit hazardous acid gases,

primarily hydrogen chloride (HCl), hydrogen fluoride (HF),

and chlorine (Cl2). 80 Fed. Reg. at 65,473. Each of these acid

gas pollutants causes health issues, such as asthma, respiratory

problems, skin irritation, burns, low blood pressure, and, in

severe cases, death. Regulatory Impact Analysis: Final Brick

and Structural Clay Products NESHAP at 4-28 to 4-30, Docket

# EPA-HQ-OAR-2013-0291-0665 (July 2015). Kilns also

emit heavy metal pollutants, such as mercury, lead, arsenic, and

other particulate matter. 80 Fed. Reg. at 65,473. Heavy metal

pollutants also cause health issues, such as neurological

damage, respiratory harm, and cancer, and threaten the natural

environment. Regulatory Impact Analysis at 4-27 to 4-33,

Docket # EPA-HQ-OAR-2013-0291-0665.

Once the EPA listed brick and ceramic kilns as a major

source of hazardous air pollutants, it was required to regulate

them. 42 U.S.C. § 7412(e)(1)(E). In 2003, the EPA first

undertook the regulation of kiln emissions under the CAA. 68

Fed. Reg. 26,690 (May 16, 2003) (“2003 Rule”). In 2007, this

Court held that the 2003 Rule did not comply with the CAA

and vacated it. Sierra Club v. EPA, 479 F.3d 875, 876 (D.C.

Cir. 2007) (per curiam) (“Sierra I”). In 2012, Sierra Club

brought suit against the EPA to force it to promulgate

regulations to replace the vacated 2003 Rule. Sierra Club v.

EPA, 850 F. Supp. 2d 300, 301 (D.D.C. 2012). In 2014, after

years of data collection, the EPA proposed a new rule to replace

the vacated standards for kiln emissions. 79 Fed. Reg. 75,622

(Dec. 18, 2014). On October 26, 2015, the EPA published the

final Brick/Clay Rule. 80 Fed. Reg. at 65,470. Industry

Petitioners then submitted a petition for reconsideration of the

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Brick/Clay Rule, which the EPA denied in relevant part. 81

Fed. Reg. 31,234 (May 18, 2016).

The Brick/Clay Rule and the EPA’s partial denial of

reconsideration are the subjects of the petitions in this

consolidated case. The Brick/Clay Rule applies to brick, clay,

and tile kilns. The emissions standards for brick and structural

clay products, such as clay pipe and roof tile, are published in

the Brick/Clay Rule and codified at 40 C.F.R. pt. 63, subpt.

JJJJJ. 80 Fed. Reg. at 65,520. The emissions standards for clay

ceramic products, such as pressed tile and sanitaryware (e.g.,

toilets and sinks), are published within the Brick/Clay Rule,

titled the National Emissions Standards for Hazardous Air

Pollutants for Clay Ceramic Manufacturing (“Clay

NESHAP”), codified at 40 C.F.R. pt. 63, subpt. KKKKK. 80

Fed. Reg. at 65,543.

Now, the Brick Industry Association petitions for

review of the Brick/Clay Rule as applicable to the brick

industry and for review of the EPA’s denial of reconsideration

of the Brick/Clay Rule. The Kohler Company petitions for

review of the Clay NESHAP. The Tile Council of North

America petitions for review of certain provisions of the Clay

NESHAP applicable to the subcategory of ceramic tile

manufacturing (“Tile NESHAP”). Finally, the Environmental

Petitioners petition for review of the Brick/Clay Rule as

applicable to all the Industry Petitioners. Industry Petitioners

intervened on behalf of the EPA in response to the

Environmental Petitioners’ petition; the Environmental

Petitioners intervened on behalf of the EPA in response to the

Industry Petitioners’ petitions.

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A. Clean Air Act Framework for Emissions

Standards

The CAA governs the setting of emissions standards

using technology and health thresholds. 42 U.S.C. § 7412(d).

When these types of limits are not feasible, the EPA may

substitute alternative methods to limit emissions such as

operational controls. Id. § 7412(h).

1. Maximum Achievable Control Technology

Emissions Standards

The 1990 amendments to the CAA directed the EPA to

issue emissions limits using technology-based standards, called

“Maximum Achievable Control Technology” (“MACT”).

MACT standards require the “maximum degree of [emissions]

reductions” that the EPA “determines is achievable.” 42

U.S.C. § 7412(d)(2); see Sierra I, 479 F.3d at 877. The

emissions standards for new sources must be no “less stringent

than the emission control that is achieved in practice by the best

controlled similar source.” 42 U.S.C. § 7412(d)(3). Congress

adopted this MACT-based scheme because the EPA’s previous

use of health-based standards had been “problematic,” because

of uncertainty over which pollutants pose a health risk. NRDC

v. EPA, 529 F.3d 1077, 1079 (D.C. Cir. 2008).

In establishing a MACT emissions standard, the EPA

defines a minimum stringency requirement, or “floor,” based

on emissions levels achieved by existing sources. 42 U.S.C.

§ 7412(d)(3)(A), (B); Sierra I, 479 F.3d at 877. For categories

and subcategories of existing emissions sources composed of

thirty or more individual sources, the EPA sets the MACT floor

using “the average emission limitation achieved by the best

performing 12 percent of the existing sources (for which the

Administrator has emissions information).” 42 U.S.C.

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§ 7412(d)(3)(A). If there are fewer than thirty individual

sources, the EPA sets the MACT floor using “the average

emission limitation achieved by the best performing 5

sources.” Id. § 7412(d)(3)(B). The EPA may set more

stringent standards than the MACT floor if the more stringent

standard is achievable considering cost and other factors. Id.

§ 7412(d)(2); U.S. Sugar Corp. v. EPA, 830 F.3d 579, 594-95

(D.C. Cir. 2016) (per curiam) (“U.S. Sugar”), cert. denied sub

nom. American Mun. Power v. EPA, 137 S. Ct. 2296 (2017).

2. Alternatives to MACT Standards

Alternatively, the EPA may use a health threshold

rather than MACT standards for “pollutants for which a health

threshold has been established.” 42 U.S.C. § 7412(d)(4); see

U.S. Sugar, 830 F.3d at 623-24. Such a health-based standard

must include an “ample margin of safety.” 42 U.S.C.

§ 7412(d)(4). Additionally, if the EPA determines it is “not

feasible” to prescribe either a health- or technology-based

emissions standard the agency may promulgate a design,

equipment, work-practice, or operational standard. Id.

§ 7412(h).

B. Brick/Clay Rule

In the Brick/Clay Rule, the EPA set MACT standards

to regulate heavy metal emissions from kilns and health

thresholds to regulate acid gas emissions. 80 Fed. Reg. at

65,471.

1. Heavy Metal Emissions

The EPA chose to regulate heavy metal emissions in the

Brick/Clay Rule using MACT standards under § 7412(d)(1).

80 Fed. Reg. at 65,471. In setting the brick MACT floor, the

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EPA set separate standards for particulate matter (which it used

as a surrogate for nonmercury hazardous metals) and mercury,

with subcategories for large tunnel and small tunnel brick kilns.

Id. at 65,530-31. Additionally, the EPA provided “alternative

equivalent limits” for heavy metal emissions from brick kilns.

Id. at 65,474, 65,485. There were more than thirty individual

sources for each category, so the best twelve percent of

performers were used to set the brick MACT floor. Id. at

65,485.

The Clay NESHAP sets separate MACT standards for

subcategories of floor tile, wall tile, and sanitaryware that are

heavy metal emissions sources. Id. at 65,478. In response to

an EPA information request, Kohler activated a

decommissioned emissions scrubber at its South Carolina Kiln

10 (“Kiln 10”), and that data was used as one of the best

performing sources in setting the corresponding MACT floor.

See id. at 65,510; see also 81 Fed. Reg. at 31,235. The Tile

NESHAP regulates emissions for a subcategory of ceramic tile

plants and has separate dioxin/furan and mercury emissions

standards. 80 Fed. Reg. at 65,554. Because fewer than thirty

sources exist for each category of clay and tile kilns, the

average of the five best performers was used to set the clay and

tile MACTs. See id. at 65,504 n.102, 65,510.

Both Industry and Environmental Petitioners challenge

the EPA’s methods of setting various MACT floors as unlawful

and arbitrary. We will address the background of those

methods in further detail with respect to the individual petitions

for review.

2. Acid Gas Emissions

The EPA regulates hazardous acid gas emissions for

new and existing brick tunnel kilns and all ceramics kilns

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except for sanitaryware shuttle kilns in the Brick/Clay Rule

using health thresholds under § 7412(d)(4). 80 Fed. Reg. at

65,471, 65,474, 65,478. Environmental Petitioners contend

that EPA’s choice of health thresholds over a MACT standard

means that kiln facilities largely will not need to add more

pollution controls. Environmental Petitioners challenge EPA’s

use of health thresholds and the methods it used to set the

thresholds as contrary to the CAA. We will address the

background of the EPA’s reasoning in setting the health

thresholds in the context of the Environmental Petitioners’

petition for review.

II. Standard of Review

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

U.S.C. § 7607(b)(1). We will set aside an EPA action under

the CAA if it is “arbitrary, capricious, an abuse of discretion,

or otherwise not in accordance with law.” 42 U.S.C.

§ 7607(d)(9)(A). We review EPA’s interpretation of the CAA

under the two-step framework of Chevron U.S.A., Inc. v.

NRDC, Inc., 467 U.S. 837 (1984). We first determine if

Congress has “directly spoken to the precise question at issue.”

Id. at 842. If so, then we must “give effect to the

unambiguously expressed intent of Congress.” Id. at 843. If,

however, “the statute is silent or ambiguous with respect to the

specific issue,” we defer to the EPA’s interpretation of the

CAA so long as it “is based on a permissible construction of

the statute.” Id.

Under these standards, we review in turn the

Environmental Petitioners’ and the Industry Petitioners’

petitions for review.

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III. Environmental Petitioners’ Petition

The Environmental Petitioners petition this Court to

review the Brick/Clay Rule, claiming that it is unlawful and

arbitrary. They argue that the EPA erred in its use of health

thresholds to regulate acid gas pollutants, in its use of the upper

prediction limit method in setting MACT floors, and in its

provision of alternative MACT floors for brick kilns.

A. Health Thresholds for Acid Gas Emissions

The Environmental Petitioners mount a three-part

challenge to the EPA’s use of health thresholds to regulate acid

gas emissions. First, the Environmental Petitioners argue that

the EPA violated the CAA by concluding that the acid gas

pollutants do not pose a cancer risk. Second, Environmental

Petitioners argue that the EPA violated the CAA and was

arbitrary in its determination of the health thresholds for the

acid gas pollutants’ noncarcinogenic risks. Finally, they

contend that the EPA violated the CAA by failing to include an

ample margin of safety in the health threshold.

1. Cancer Risks

Petitioners contend that the EPA violated the CAA by

concluding that the acid gas pollutants do not pose a cancer

risk. Under the CAA, the EPA may implement a health

threshold-based emissions limit for “pollutants for which a

health threshold has been established.” 42 U.S.C.

§ 7412(d)(4). The EPA and Environmental Petitioners agree,

though for differing reasons, that the EPA should not

implement health thresholds in lieu of MACT standards for

carcinogenic pollutants.

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Under Chevron step one, Environmental Petitioners

argue that the EPA acted contrary to the clear meaning of the

word “established” in 42 U.S.C. § 7412(d)(4)—“to put beyond

a reasonable doubt: prove,” WEBSTER’S NEW COLLEGIATE

DICTIONARY 284 (7th ed. 1971)—by concluding based on mere

lack of evidence that hydrogen chloride, hydrogen fluoride, and

chlorine do not cause cancer. Likewise, the Environmental

Petitioners argue that the term “health threshold” in

§ 7412(d)(4) unambiguously requires the EPA to identify the

specific amount of a pollutant that lacks any health risk.

Because the EPA did not rely on conclusive proof that the acid

gas pollutants are noncarcinogenic, the Environmental

Petitioners assert that the EPA violated the plain language of

the CAA requiring it to find an “established” “health threshold”

when formulating health-based standards under § 7412(d)(4).

We cannot resolve this case at step one as

Environmental Petitioners urge. In other contexts, we have

held that the “EPA is not obligated to conclusively resolve

every scientific uncertainty before it issues regulation.” White

Stallion Energy Ctr., LLC v. EPA, 748 F.3d 1222, 1245 (D.C.

Cir. 2014) (per curiam), rev’d on other grounds by Michigan v.

EPA, 135 S. Ct. 2699 (2015). The statutory term “established”

does not unambiguously require that the EPA prove its

scientific conclusions beyond all possible doubt. Nor does the

term “health threshold” require that the EPA find a specific

threshold that lacks uncertainty. With respect to scientific

conclusions, “established” and “health threshold” are

ambiguous terms and we give deference to the EPA to the

extent its interpretations fall within the bounds of

reasonableness.

The Environmental Petitioners separately argue that the

EPA acted unreasonably in concluding that it was “established”

that the acid gases present no cancer risk. The Environmental

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Petitioners contend that the EPA’s reliance on the lack of

expert data on the cancer risks of these pollutants is insufficient

to demonstrate that their non-carcinogenic nature was

“established.”

The EPA counters that it is not required to prove a

negative and that its interpretation of “established” is based on

its expert judgment that it need not find “universal agreement”

that the acid gases pose no cancer risk. To reach its conclusion,

the EPA reviewed toxicity assessments in several databases

and opinions from scientific bodies and found that none

classified the three acid gas pollutants as carcinogens or as

“suggestive of the potential to be carcinogenic.” 80 Fed. Reg.

at 65,488. Further, the EPA searched for existing studies

regarding the cancer risk of the acid gases and found that,

though the studies are limited in scope, none proved any

carcinogenic potential. Id. at 65,488-89.

The EPA has not provided a sufficient record to

determine that there is no cancer risk. The EPA noted that for

hydrogen chloride “[l]ittle research has been conducted on its

carcinogenicity.” 79 Fed. Reg. at 75,639-41; see also 80 Fed.

Reg at 65,488-90. In addressing the cancer risk of chlorine, the

EPA reviewed limited studies of workers in the chemical

industry. 80 Fed. Reg. at 65,489. In addition to reviewing

limited studies of workers, EPA also reviewed studies

involving rodents and non-human primates. Id. With respect

to hydrogen fluoride, the EPA observed there was a “limited

number of studies investigating the carcinogenic potential of

[Hydrogen Fluoride]” and “[t]hese studies are unreliable on the

issue of possible carcinogenicity of [Hydrogen Fluoride]

and/or fluorides, in general, because of many confounding

factors . . . and because no breakdown was done by type of

fluoride exposure.” Id. at 65,488. This is not merely a situation

in which the EPA relies on the results of scientific studies that

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were unable to demonstrate a cancer risk to “prove a negative.”

Rather, the EPA relies on the lack of any significant studies.

The EPA failed to explain how it was able to reach the

conclusion that the acid gas pollutants do not pose a cancer risk

despite the admittedly limited body of research. Because of

this acknowledged lack of evidence, the EPA did not base its

findings on substantial evidence.

Therefore, the EPA acted unreasonably by concluding

that it is “established” that the acid gas pollutants pose no

cancer risk. Accordingly, we grant the Environmental

Petitioners’ petition on this issue.

2. Noncarcinogenic Risks

Second, Environmental Petitioners argue that the EPA

violated the CAA and was unreasoned and arbitrary by relying

on low confidence evidence for the health risks of hydrogen

chloride, by declining to use the California Environmental

Protection Agency’s reference concentrations for hydrogen

chloride, and by not shielding the public from acute exposure

to hydrogen fluoride.

a. Hydrogen Chloride

With respect to the noncarcinogenic health threshold

for hydrogen chloride, Environmental Petitioners argue that the

EPA violated the CAA’s requirement that the health threshold

be “established” by relying on a low confidence reference

concentration value in setting the emissions limit. The

Environmental Petitioners assert that any deference to the

EPA’s interpretation of “established” does not extend to

allowing the EPA to use a single low-confidence, low-quality

risk assessment to conclude that a threshold is “established.”

Further, the California EPA uses a more conservative reference

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concentration for the amount of hydrogen chloride that does

not pose a health risk, and the EPA failed to explain why it used

a different reference concentration.

The EPA explained that the “low confidence” label

means that it has low confidence in the derivation of the

hydrogen chloride reference concentration below which no

adverse health risks were expected to occur because the

existing data were incomplete and the reference concentration

is subject to change as new data are developed. 80 Fed. Reg.

at 65,489-90. Further, the EPA asserted that though reference

concentrations are assigned high, medium, and low confidence

values based on the supporting database, even a low confidence

value is reliable enough for regulatory use. Id. at 65,490. The

EPA stated that it did not use the California EPA’s hydrogen

chloride reference concentration because of its general

preference “favoring EPA benchmarks.” Id. at 65,491.

The EPA’s statement that “low confidence” reference

concentrations are suitable for regulatory purposes lacks any

supporting reasoning. The EPA did not explain how the health

threshold could be established if low confidence reference

concentrations are subject to change. This lack of reasoning is

compounded by the EPA’s failure to explain why low

confidence data were enough to demonstrate an “established”

limit less strict than the California EPA threshold. Because the

EPA acted unreasonably in finding that the noncarcinogenic

health threshold for hydrogen chloride was established, we

grant the Environmental Petitioners’ petition as to this issue.

b. Hydrogen Fluoride

With respect to the hydrogen fluoride health threshold,

the Environmental Petitioners argue that the emissions limits

do not protect the public from the health effects of acute

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exposure, as required for health thresholds. See 42 U.S.C.

§ 7412(d)(4). In both the brick and ceramics risk assessments,

the EPA found that some kilns had the potential to exceed the

health threshold for acute exposures, but concluded there was

a “low potential” for health effects. The EPA calculated a

hazard quotient of two for these acute exposures, where a

hazard quotient less than one indicates low potential for acute

health risk. 80 Fed. Reg. at 65,503.

EPA argues that the hazard quotient calculation is

conservative. First, the hazard quotient calculation uses the

conservative California EPA acute reference concentration to

calculate the exposure level and if it had applied its own

reference level, there would have been a hazard quotient less

than one. However, the EPA does not offer a calculation or

explanation to confirm this assertion. Second, the EPA’s acute

exposure scenario conservatively assumes that someone is

present at a time with both worst-case emissions and worst-

case weather conditions. Finally, the EPA reasoned that it was

unlikely a facility would emit only hydrogen fluoride at the

maximum permitted concentration rather than a combination

of other gases.

EPA’s reasoning is flawed. As we held in the hydrogen

chloride analysis, the EPA failed to explain why it would be

appropriate to use a less conservative standard than the

California EPA level. Thus, even assuming that use of EPA’s

reference level would have resulted in below-one hazard

quotients, EPA fails to show that the hazard quotient

calculation performed protects from acute exposure. Likewise,

the EPA failed to explain why “no adverse health effects are

expected to occur,” 80 Fed. Reg. at 65,491, in the worst-case

scenario of peak emissions during worst-case weather. The

EPA does not adequately explain how a hydrogen fluoride

emissions limit based on an “established health threshold” can

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permit potential health risks from acute exposure. Therefore,

we grant the Environmental Petitioners’ petition as to this

issue.

3. Ample Margin of Safety

Third, Environmental Petitioners argue that the EPA

violated the CAA by failing to include an ample margin of

safety. For health-based standards, the CAA directs the EPA

to set a “threshold level, with an ample margin of safety.” 42

U.S.C. § 7412(d)(4). Environmental Petitioners argue that, by

failing to do so, the EPA violated the plain language of the

CAA.

EPA responds that it is entitled to deference in

determining “how” to provide the ample margin of safety

because the statute does not provide unambiguous direction.

According to EPA, we should defer to its interpretation that an

ample margin of safety can be built into a health threshold by

using “conservative” modeling assumptions that provide the

margin of safety “at multiple points in the process.” The

Environmental Petitioners counter that the word “with”

requires that the ample margin of safety be added to the health

threshold.

The EPA offered a limited description of how it built a

margin into its model by adopting conservative assumptions.

80 Fed. Reg at 65,501. First, the EPA identified the source that

produced the highest modeled ambient concentration of

hazardous air pollutants. Id. Then, the EPA modeled that

source, with worst-case weather and worst-case population

proximity, and scaled up its emissions until it reached a hazard

quotient of one, at which point it would be expected to affect

human health. The EPA used that scaled-up emissions value

as the health-based emissions limit. Id. Because it is unlikely

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that any source would ever experience both worst-case weather

and population proximity when maximum emissions occur, the

EPA concluded that its emissions limit was “health protective”

and provides an ample margin of safety. Id. In this

conservative model, however, the EPA still found cases that

exceeded the hazard quotient of one, indicating a human health

risk, but nonetheless concluded that there was a low potential

for health impacts because it is unlikely that a person will be

present at the place and time when maximum risk occurs. 80

Fed. Reg. at 65,502-03.

Though we agree that the EPA is entitled to deference

in determining how to include an ample margin of safety in the

health threshold, the question is whether the EPA provided any

margin of safety at all. The EPA’s model actually

demonstrates a situation in which a source could emit up to the

emissions limit and, together with worst-case weather or

population proximity, the source could meet or exceed the

health threshold. Therefore, the EPA has not offered a

sufficient explanation of how its model includes an ample

margin of safety to the health threshold. Because the EPA did

not meet the CAA requirement to include an ample margin of

safety in the health threshold, we grant the Environmental

Petitioners’ petition as to this issue.

For the reasons stated above, we grant the

Environmental Petitioners’ petition for review of the EPA’s

setting of a health threshold for the acid gases.

B. Use of the Upper Prediction Limit to Set MACT

Floors

The Environmental Petitioners next contend that the

EPA’s methodology in setting the MACT floors is inconsistent

with the CAA. The EPA used a method called the “upper

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prediction limit,” which is a statistical tool that allows the EPA

to estimate the best performing source from a limited data set

and account for the variability inherent to emissions and

emissions testing. See generally National Ass’n of Clean

Water Agencies v. EPA (“NACWA”), 734 F.3d 1115, 1122,

1144-45 (D.C. Cir. 2013). The EPA used the upper prediction

limit for twenty-two of the brick MACT floors and twenty-

seven of the clay MACT floors. A number of the brick and

clay MACT floors were based on datasets that EPA concedes

were “limited.”

The EPA relies on “stack tests” to sample actual kiln

emissions. See Use of the Upper Predicition Limit for

Calculating MACT Floors (“HA for Calculating MACT

Floors”) at 2, Docket # EPA-HQ-OAR-2013-0291-0128 (Sept.

9, 2014). The EPA generally collects and tests emissions from

a source three times, each for a discrete period of time,

capturing snapshots of the emissions. See NACWA, 734 F.3d

at 1122. However, emissions vary over time and there are

variations in testing equipment and laboratories; stack tests do

not measure the emissions at all times and under all conditions.

Id. Because stack test emissions results are variable, the upper

prediction limit applies statistical methods to the results in

order to derive an emissions limit that accounts for that

variability within a specified degree of confidence. See id. The

upper prediction limit equation factors in the average of the

best performing source’s stack test results, the distribution of

the results, the variance of the results, and the total number of

tests in order to calculate a MACT floor. UPL for Calculating

MACT Floors at 4-5.

We “accord[] Chevron deference to [the EPA’s]

interpretation of [the CAA] as allowing it to estimate MACT

floors.” U.S. Sugar, 830 F.3d at 636 (third alteration in

original). The EPA has “wide latitude” in its data gathering to

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set the MACT floor. Id. This Court has discussed the EPA’s

application of the upper prediction limit method to calculate

MACT floors.

In NACWA, our key concern was whether the EPA had

provided a reasoned basis to conclude that the upper prediction

limit represents the CAA’s “average emissions limitation

achieved.” NACWA, 734 F.3d at 1130, 1139-45; see also U.S.

Sugar, 830 F.3d at 633. We held that the EPA “ha[d] not

clearly explained how the upper prediction limit itself operates

to predict [the best performing sources’ upper limit] with

sufficient accuracy” or “how the upper prediction limit can

actually predict the upper limit EPA expects the best

performing unit or units to achieve.” NACWA, 734 F.3d at

1144-45.

In U.S. Sugar, the EPA provided the explanation that

had been lacking in NACWA, describing the limitations of

stack-test data, why the agency chose to use the upper

prediction limit, and how and why the upper prediction limit

accounts for variability in test results. U.S. Sugar, 830 F.3d at

636-37. EPA explained how the upper prediction limit “allows

a reasonable inference” regarding the emissions of top

performing units, and upon review we held that the EPA “ha[d]

conducted reasoned decision making.” Id. at 636. Thus, we

accepted the upper prediction limit as consistent with the CAA,

but with the caveat that whether it could be reasonably applied

to small datasets remained an open question. Id. at 633 n.25.

In this case, EPA has sufficiently explained the

application of the upper prediction limit to small datasets, but

in five cases failed to explain adjustments made to individual

upper prediction limit calculations. The EPA defined a

“limited dataset” as having between three and six data points,

and explained why it was possible to use datasets with as few

20

as three data points, though no fewer so long as the EPA

engages in further evaluation. Approach for Applying the

Upper Prediction Limit to Limited Datasets (“Brick Limited

Datasets Memo”) at 5-6, Docket # EPA-HQ-OAR-2013-0291-

0661 (Sept. 24, 2015); Approach for Applying the Upper

Prediction Limit to Limited Datasets (“Clay Limited Datasets

Memo”) at 5-6, Docket # EPA-HQ-OAR-2013-0290-0295

(Sept. 24, 2015). Except where adjustments were made to

results, Environmental Petitioners provide no reason to think

that any of the results reached by applying the upper prediction

limit to limited datasets are unreasonable or inadequately

explained. EPA failed, however, to adequately explain

adjustments it made to five of the upper prediction limit results.

The EPA argues that it was sufficient for it to evaluate

the “reasonableness” of the results produced by the upper

prediction limit for small datasets on a case-by-case basis and

then adjust the results to best estimate the reductions in

emissions achieved by the best performing sources. Brick

Limited Datasets Memo at 6-10. EPA made no adjustments to

its upper prediction limits results for the Clay MACT floors.

Clay Limited Datasets Memo at 8. For brick plants, the EPA

made five adjustments to MACT floors because it concluded

that the upper prediction limit produced unreasonable results.

Brick Limited Datasets Memo at 8-10. In two of those cases,

EPA rejected datasets that were in fact from the best

performing source, resulting in a MACT floor that was derived

from the second best performing unit rather than the best

performing. Id. at 8-9.

Although EPA adequately explains the general bases

for its evaluation and adjustment, id. at 6-8, the agency offered

only cursory explanations of the specific choices it made in

adjusting five of the floors. EPA also did not explain how using

data from the second best performing unit instead of the best

21

performing unit comports with the CAA’s requirements that

MACT floors be calculated based on the best performing unit

or units. Id. at 8-10. EPA must better explain its reasoning

when performing such adjustments. For that we reason we

grant Environmental Petitioners’ petition as to the five adjusted

floors. We deny the petition as to the other applications of the

upper prediction limit to limited datasets.

C. Provision of Alternative Emissions Floors for

Brick Plants

The Environmental Petitioners argue that the EPA’s

decision to allow brick tunnel kilns to comply with

“alternative” emissions floors is not authorized by the CAA.

Rather than a single limit for each brick tunnel kiln

subcategory, the EPA gave the brick industry a choice of three

emissions limits expressed in different units of measurement

for mercury (mass of pollutant per ton of bricks produced,

pounds per hour, or concentration) and non-mercury emissions

(pounds per hour and options that limit particulate matter as a

surrogate). 80 Fed. Reg. at 65,474, 65,530-31.

The Environmental Petitioners argue that EPA’s

provision of alternative emissions limits violates the statute’s

plain language requiring the MACT floor to be set based on

“the best” performing sources in a category. 42 U.S.C.

§ 7412(d)(3). Thus, it is contrary to the plain meaning of “best”

to define several different groups of sources as “the best.” The

EPA counters that its interpretation of “best” should receive

deference because Congress did not specify which unit of

measurement the EPA should use to identify the best

performing source. Different sources perform differently

depending on the unit of measurement—for instance, a small

kiln might produce a smaller volume of pollutants overall than

a larger source but pollutes at a higher rate when emissions are

22

measured in pounds per hour. See Final [MACT] Floor

Analysis for Brick and Structural Clay Products

Manufacturing, at A-2, A-5, A-9, Docket # EPA-HQ-OAR-

2013-0291-0660 (Sept. 24, 2015). The EPA argues it was

reasonable for it to allow the industry to select which emissions

limit unit of measurement their kilns must meet. We disagree.

The EPA has the authority to “distinguish among

classes, types, and sizes” of emissions sources and set separate

MACT floors for each. See 42 U.S.C. § 7412(d)(1). But once

the EPA identifies a source in a category it must set the MACT

floor based on the “best” performing sources. Id. § 7412(d)(3).

EPA has the discretion to determine what metric to use in

defining the “best” source, so long as it is reasonable. Cf.

Mossville Env. Action Now v. EPA, 370 F.3d 1232, 1241 (D.C.

Cir. 2004). However, the EPA’s discretion does not extend to

defining several different “best” metrics within the same

category and allowing emitters to comply with the most

favorable standard. The alternative standards allow a kiln to

avoid complying with a MACT floor defined by the best

emissions achieved by other sources in its category, as required

by the CAA. Because the EPA’s provision of alternate

emissions standards is contrary to the statutory requirement of

a standard based on the “best” performing sources, we grant the

Environmental Petitioners’ petition as to this issue also.

IV. Industry Petitioners’ Petition

In four of the consolidated cases, Industry Petitioners

petition for review of the Brick/Clay Rule by challenging the

EPA’s methodology in setting the MACT floor for their

respective categories and subcategories of kilns. We address

in turn the Brick Industry Association’s petition for review of

the brick MACT floor, the Tile Council’s petition for review of

23

the Tile NESHAP, and Kohler’s petition for review of the Clay

NESHAP.

A. Brick MACT Floor

With respect to the portion of the Brick/Clay Rule in

which the EPA set the MACT floor for large and small tunnel

brick kilns, the Brick Industry argues that: (1) EPA violated

the CAA because it used synthetic minor sources to set the

MACT floor for brick plant major sources; (2) EPA acted

arbitrarily and capriciously because it did not explain its use of

allegedly suspicious data in setting the particulate matter and

nonmercury hazardous metal emissions standards; and

(3) EPA violated the intent of Congress by setting mercury

emissions standards which require raw material substitution.

1. Use of Synthetic Minor Sources in Setting

MACT Floors

First, the petitioner argues that the EPA violated the

CAA because it used emissions data from synthetic minor

sources to set the MACT floor for particulate matter and

nonmercury hazardous metal emissions for brick plant major

sources. The EPA uses particulate matter emissions as a

surrogate for all nonmercury hazardous metal emissions. See

80 Fed. Reg. at 65,484.

As an initial matter, the EPA argues that the Brick

Industry Association’s petition for review is untimely because

it failed to raise this issue when the EPA used synthetic minor

sources to set the MACT floors in the 2003 Rule. We lack

jurisdiction to review a claim unless the petition for review is

brought within sixty days of the challenged action appearing in

the Federal Register. Medical Waste Inst. & Energy Recovery

Council v. EPA, 645 F.3d 420, 427 (D.C. Cir. 2011) (citing 42

24

U.S.C. § 7607(b)(1)). But this Court vacated the 2003 Rule.

Sierra I, 479 F.3d at 876. The existence of a prior but now-

vacated rule does not bar a later petition to review the

replacement rule. See Motor & Equip. Mfrs. Ass’n v. Nichols,

142 F.3d 449, 460-61 (D.C. Cir. 1998). We now turn to the

merits of the petition for review.

Because there are more than thirty sources in the brick

plant source category, the EPA sets the MACT floor by

determining “the average emission limitation achieved by the

best performing 12 percent of the existing sources . . . in the

category.” 42 U.S.C. § 7412(d)(3)(A). The petitioner argues

that “synthetic minor sources” (also called “synthetic area

sources”) are not major sources. Thus, the petitioner contends

that the EPA’s inclusion of synthetic minor sources in the list

of best performing major sources violates the statutory

requirement that the EPA use data from sources “in the

category.”

The EPA admits that it used emissions data from

synthetic minor sources to set the MACT floor for brick plant

major sources. A “major source” is defined as one that “emits

or has the potential to emit considering controls, in the

aggregate, 10 tons per year or more of any hazardous air

pollutant or 25 tons per year or more of any combination of

hazardous air pollutants.” 42 U.S.C. § 7412(a)(1) (emphasis

added). An “area source” is defined as “any stationary source

of hazardous air pollutants that is not a major source.” Id.

§ 7312(a)(2). The CAA does not define “synthetic minor

source” or “synthetic area source.”

The EPA explained that a synthetic minor source emits

lower quantities of hazardous air pollutants than a major source

“because they use some emission control device(s), pollution

prevention techniques or other measures . . . .” Summary of

25

Public Comments and Responses, at 46-47, Docket # EPA-

HQ-OAR-2013-0291-0685 (Sept. 2015). However, “[i]f not

for the enforceable controls they have implemented, synthetic

minor sources would be major sources under . . . the CAA.” Id.

at 47. The EPA’s definition of a synthetic minor source

conforms to the plain text of the CAA, which states that major

sources include sources with “the potential to emit considering

controls.” 42 U.S.C. § 7412(a)(1).

Next, the Brick Industry argues that synthetic minor

sources do not qualify as “in the category” of major brick plant

sources, because treating them as in the same category deprives

the phrase of any meaning. We disagree. In this case, the EPA

has defined categories of small and large tunnel brick kiln

sources, while excluding tile and other nonbrick sources,

meaning the phrase “in the category” still has meaning. We

defer to the EPA’s reasonable interpretation that “the category”

should be defined as major brick sources, including those with

the potential to emit to that level considering controls, such as

synthetic minor sources, as required by the CAA.

Accordingly, we deny the Brick Industry Association’s

petition for review because the EPA did not violate the CAA

by using emissions data from synthetic minor sources to set the

MACT floor for particulate matter and nonmercury metal

emissions for brick plant major sources.

2. Data Used to Set Particulate Matter MACT

Floors

Second, the Brick Industry Association argues that the

EPA acted arbitrarily and capriciously because it did not

correct, supplement, or reconcile suspicious data and used that

data to set the MACT floor for particulate matter and

nonmercury hazardous metal emissions from brick plants.

26

Brick plants may incorporate air pollution control

devices, such as fabric filters or dry lime absorbers. See 79

Fed. Reg. 75,625. The Brick Industry Association argues that

the EPA relied on erroneous data from kilns that use dry lime

absorbers as the best performing sources without explaining

why those sources performed unexpectedly better than the kilns

equipped with fabric filters.

In the proposed Brick/Clay Rule, the EPA

acknowledged that data showed that fabric filters were

generally the best pollution control technology for particulate

matter emissions. 79 Fed. Reg. at 75,635. Accordingly, the

EPA proposed to determine the MACT floor based on the

twenty-seven best performing fabric filter-based kilns, which it

expected would represent the top twelve percent of the 255

operating major source and synthetic minor source brick tunnel

kilns. Id. Along with the proposal, the EPA requested

additional information to address whether low emissions data

from nonfabric-filter kilns showing high performance were

reliable. Id. The EPA noted that it could, in the alternative, set

the particulate matter MACT floor based on the top twelve

percent of all brick plants in each kiln size subcategory. Id. at

75,635 n.1. The EPA explained that “the reliability of the data

showing low emissions from some kilns without a [fabric

filter]-based [pollution control] is a key factor in the EPA’s

determination of which approach is appropriate.” Id.

In the final Brick/Clay Rule, the EPA adopted this

alternative approach, setting the particulate matter MACT floor

based on the best performing twelve percent of kilns in each

size subcategory without regard to the type of pollution

controls used. 80 Fed. Reg. at 65,485. This resulted in a

significantly more stringent control than expected in the

proposed rule based on data from fewer sources because the

27

EPA had not collected as much data from nonfabric filter

sources. See Id. at 65,484-85, 65,530. The Brick Industry

Association objects to the EPA’s adoption of this method,

arguing that dry lime absorbers are “only incidentally

effective” in controlling particulate matter emissions, therefore

any data that shows these kilns are performing better than those

with fabric filters is “technically not plausible.” Therefore, the

Brick Industry Association contends, the EPA relied on

anomalous results and acted arbitrarily by failing to resolve the

anomalies. Further, the Brick Industry Association argues that

the EPA compounded its error by removing data points from

kilns utilizing fabric filters.

In the final Brick/Clay Rule and upon reconsideration,

the EPA explained that it received no data explaining why

some kilns without fabric filters performed exceptionally well.

80 Fed. Reg. at 65,485. Further, the EPA noted that in some

cases there were issues with probe and filter temperatures

which invalidated the data from some fabric filter kilns,

requiring that data to be thrown out. Id. at 65,484-85.

Additionally, the EPA had observed in the proposed rule that

the data from the dry lime absorber kilns showed that the fabric

filters might not be the best performing filters as originally

thought. 79 Fed. Reg. at 75,635.

In light of this admittedly unexpected result, the EPA

reviewed the data to confirm that the tests were performed in

normal operating conditions and requested additional data from

the Brick Industry Association. Id. The Brick Industry

Association provided a list of the dry lime absorber kilns that

it recommended should be excluded from the top performing

set of kilns, primarily speculating these kilns performed well

because they had installed new limestone but offering no other

concrete evidence or analysis in support of this speculation.

28

Email Re: DLA/Uncontrolled Kilns, Docket # EPA-HQ-OAR-

2013-0291-0614 (June 25, 2015).

As we have already noted, “EPA typically has wide

latitude in determining the extent of data-gathering necessary

to solve a problem.” Sierra Club v. EPA, 167 F.3d 658, 662

(D.C. Cir. 1999). The EPA’s explanation of why it discarded

some of the data from the fabric filter-based kilns and why it

relied on the best twelve percent of all the sources for which it

had data, rather than just the best performing fabric filter-based

sources, was sufficiently reasoned and is entitled to deference.

Additionally, the Brick Industry Association argues

that the EPA failed to respond to its comment containing the

list of dry lime absorber kilns that it contends should have been

excluded from consideration as best performing sources. The

EPA has an obligation to respond to significant comments to

the regulation. 42 U.S.C. § 7607(d)(6)(B). However, the EPA

determined that the Brick Industry Association’s comment was

not significant because it failed to offer any explanation or data

showing the data from high-performing nonfabric filter kilns to

be unreliable. We agree. Because the comment contained only

speculation, without additional details, it was not “significant.”

Accordingly, we deny the Brick Industry Association’s

petition for review because the EPA was not arbitrary or

capricious when it used data from kilns that did not use fabric

filters to set the MACT floor for particulate matter emissions

from brick plants.

3. Improper Requirement to Substitute Raw

Materials

Third, the Brick Industry argues that the EPA violated

Congressional intent by setting mercury emissions standards

29

that require that the industry make raw material substitutions.

Mercury content varies based on where clay is quarried, which

can affect the resulting mercury emissions from kilns using the

clay. 80 Fed. Reg. at 65,485. Relying on the legislative

history, the Brick Industry Association argues that the 1990

amendment to the CAA prohibited the EPA from requiring

material substitutions when it sets emissions standards. See

H.R. Rep. No. 101-952, at 339 (1990) (Conf. Rep.). Further,

the Brick Industry Association argues that the EPA acted

unreasonably because it did not establish subcategories based

on raw materials to avoid raw material substitutions.

“When setting the MACT floor, the EPA considers only

the performance of the cleanest sources in a category or

subcategory; it does not take into account other factors . . . .”

U.S. Sugar, 830 F.3d at 594. This Court has held that the EPA

is required to set a MACT floor that “reflect[s] what the best

performers actually achieve,” and the EPA may not deviate

from that by requiring that “floors must be achievable by all

sources using MACT technology.” Cement Kiln Recycling

Coal. v. EPA, 255 F.3d 855, 861 (D.C. Cir. 2001). Likewise,

in addressing the 2003 Rule in Sierra I, we held that setting

MACT floors based on technology controls alone was

insufficient to satisfy the CAA’s requirements. 479 F.3d at

883. Nontechnology factors, such as the source of raw

materials, can affect emissions levels and cannot be ignored.

Id. In other words, the EPA need not consider whether all

sources can achieve the MACT floor, and must still set the floor

based on the emissions achieved by the best performers even

though they have access to different raw materials than the

other sources. Id.

Ultimately, though, the Brick Industry Association’s

argument is misplaced. The EPA did not mandate a raw

material substitution. The EPA responded to a comment by

30

stating that it is “not requiring the use of offsite raw materials

in this rule.” Summary of Public Comments and Responses at

26. Furthermore, the EPA considered the effect of raw

materials in defining the MACT floor and used a variability

equation to factor in the variation in mercury content in clay

quarries. 80 Fed. Reg. at 65,485. Additionally, the EPA

considered the existence of potential control technology that

would allow the industry to achieve the MACT floor without a

raw material substitution. Summary of Public Comments and

Responses at 26-27.

The EPA reasoned that some brick kilns could use an

activated-carbon injection control device in order to achieve

the MACT floor without a raw material substitution. Id. The

Brick Industry Association contends that it is unreasonable for

the EPA to consider this device because the EPA has not shown

it would be effective. However, the EPA cited information

showing that activated-carbon injection devices are effective in

other industries in controlling mercury emissions from similar

sources. Methodology and Assumptions Used to Estimate the

Model Costs and Impacts of BSCP Air Pollution Control

Devices for the Final Rule at 7-9, Docket # EPA-HQ-OAR-

2013-0291-0662 (Sept. 24, 2015). Finally, in response to the

Brick Industry Association’s comment that the EPA should

have created subcategories based on the mercury content of the

raw materials, instead of the size of the brick kilns, the EPA

explained that it did not have enough information to create

those subcategories, because the data did not show a strong

correlation between raw material mercury and mercury

emissions. Summary of Public Comments and Responses at

13.

The EPA relied on substantial evidence to conclude that

technological controls are available to achieve the MACT floor

without raw material substitution and made a reasoned decision

31

not to subcategorize based on the mercury content of raw

materials. Likewise, the EPA is not required to set a standard

that is achievable by all sources. Therefore, we deny the Brick

Industry Association’s petition for review.

B. Tile NESHAP

The Tile Council of North America petitions for review

of the Tile NESHAP. The petitioner first argues that the EPA

violated the CAA by listing it as a major source because there

are no longer any major source tile kilns and, further, that it

was denied its right to comment on its listing. Next, the Tile

Council argues that even if the EPA was permitted to

promulgate the Tile NESHAP, the EPA erred by failing to

perform a beyond-the-floor MACT analysis for dioxin/furan

emissions.

The central issue in the Tile Council’s petitions is its

objection to the EPA’s listing of tile kilns as a major source of

hazardous air pollutants. In 2002, the EPA replaced a clay

products manufacturing source category with two source

categories: brick and structural clay products and clay ceramic

products, the latter of which includes tile. 67 Fed. Reg. 47,894

(July 22, 2002). At the time, there were tile-manufacturing

plants that were major sources of hazardous air pollutants. Id.

at 47,914. Once an industry is listed as a major source of

hazardous air pollutants, the EPA must establish emissions

limits. 42 U.S.C § 7412(d)(1). In 2014, just before the EPA

proposed the Brick/Clay Rule, all tile kilns that that would be

subject to its emissions standards as major sources either closed

or became synthetic area sources. TCNA Letter, Docket

# EPA-HQ-OAR-2013-0290-0131 (Aug. 29, 2014).

As a threshold matter, we must address the Tile Council

of North America’s standing. Its membership is made up of

32

domestic ceramic tile manufacturing companies. To

demonstrate that it has standing, the Tile Council must

establish its injury is actual or imminent, not hypothetical.

Lujan v. Defenders of Wildlife, 504 U.S. 555, 560 (1992).

When “standing is not self-evident, . . . the petitioner must

supplement the record to the extent necessary to explain and

substantiate its entitlement to judicial review.” Sierra Club v.

EPA, 292 F.3d 895, 900 (D.C. Cir. 2002). The Tile Council

asserts that it has standing because its members operate

ceramic tile kilns that fall within the Tile NESHAP

subcategory and those members have a direct financial and

environmental stake in the Brick/Clay Rule.

The Tile Council admits that none of its members are

major sources, and so they are not subject to the Tile

NESHAP’s emissions limits. But the Tile Council argues that

its members are constructing new kilns that may be subject to

the major source emissions limits. Further, the Tile Council

claims that its members expend resources to remain area

sources and avoid being subject to emissions limits on major

sources. The EPA argues that the Tile Council lacks standing

because none of its members have suffered harm or face

imminent harm from the emissions limits on major sources.

We agree with the EPA. The Tile Council failed to identify

any member that is injured or will imminently be injured by the

Brick/Clay Rule. The Tile Council’s arguments regarding

potential future injuries are merely speculative.

Likewise, the Tile Council of North America’s

assertion that it has associational standing also fails. To

establish associational standing, its members must have

individual standing to challenge the Tile NESHAP in their own

right. Hunt v. Wash. State Apple Advert. Comm’n, 432 U.S.

333, 342 (1977). Because we have concluded that the Tile

Council of North America has not identified an injury or

33

imminent injury to any of its members from the Tile NESHAP,

it has not demonstrated that its members have individual

standing to challenge the rule in their own right. Therefore, the

Tile Council of North America does not have associational

standing.

Because we find that Tile Council of North America

has no standing to petition for review of the Tile NESHAP, we

need not address the petitioner’s remaining arguments on their

merits.

C. Clay NESHAP

With respect to the Clay NESHAP, Kohler argues that

the EPA violated the CAA by using emissions data that was not

representative of any existing operating source to set the

MACT floor for clay sanitaryware kilns. Because there are less

than thirty sources in the clay kiln source category, the EPA

sets the MACT floor based on “the average emission limitation

achieved by the best performing 5 sources.” 42 U.S.C.

§ 7412(d)(3)(B) (emphasis added). Specifically, Kohler argues

that the EPA erred by including data from Kiln 10 as one of the

best performing sources.

When Kohler constructed Kiln 10 in 2005, it installed a

scrubber to comply with the now-vacated 2003 Rule for new

sources. 80 Fed. Reg. at 65,510. In 2009, Kohler

decommissioned the scrubber and now operates Kiln 10

without it. Id. However, the Kiln 10 scrubber remained

functional and attached to the source. Id. During the data

collection period, the EPA asked Kohler to reactivate the

scrubber and EPA tested Kiln 10 while the scrubber was

operating. Id.

34

We have repeatedly recognized that section 7412(d)(3)

requires the floors to reflect emissions achieved “in practice.”

See, e.g., Cement Kiln, 255 F.3d at 862; Nat’l Lime Ass’n v.

EPA, 233 F.3d 625, 632 (D.C. Cir. 2000). It may seem that the

“in practice” requirement supports Kohler’s argument that the

data collected from Kiln 10 while it was using the scrubber was

“artificial” and in performance of a test, not “in practice.”

However, the statute does not specify when emissions achieved

“in practice” occur. Likewise, the statute requires that the EPA

consider the average emissions “achieved,” which

contemplates that the performance could have occurred in the

past. See 42 U.S.C. § 7412(d)(3).

Kohler operated Kiln 10 with the scrubber between

2005 and 2009. 80 Fed. Reg. at 65,510. The EPA correctly

reasoned that emissions produced with a scrubber were

“achieved” during that time. That the EPA chose to collect the

data through a later test after Kohler decommissioned the

scrubber rather than during its four years of operation is within

the EPA’s discretion.

This Court considered a similar argument in a case

regarding emissions standards for hospital waste incinerators.

Med. Waste Inst. & Energy Recovery Council v. EPA, 645 F.3d

420 (D.C. Cir. 2011). In that case, we affirmed the EPA’s use

of emissions data from a facility that had put controls in place

to comply with a remanded, but not vacated, rule. Id. at 422,

424-25. Though in this case the EPA used data from a source

with pollution controls that were put in place to comply with a

rule that was vacated, this distinction is not of “outcome-

changing significance.” Id. at 426.

We deny Kohler’s petition for review because the EPA

did not violate the CAA when it used data from Kiln 10 as a

35

best performing source because the EPA reasonably concluded

that Kiln 10 had achieved those emissions “in practice.”

V. Conclusion

For the reasons set forth above, we deny the Industry

Petitioners’ petitions for review and we grant the

Environmental Petitioners’ petition for review as to (1) the

EPA’s use of a health threshold to set the emissions limit for

acid gases; (2) the EPA’s ad hoc adjustments of upper

prediction limit calculations, and (3) the EPA’s provision of

alternative MACT floors for brick plants. We deny the

Environmental Petitioner’s petition for review as to the general

application of the upper prediction limit to limited datasets as

defined by the EPA. We remand the Brick/Clay Rule to the

agency for further proceedings consistent with this opinion.