Association of Irritated Residents , a California non-profit corporation v. U.s. Environmental Protection Agency

FOR PUBLICATION
UNITED STATES COURT OF APPEALS
FOR THE NINTH CIRCUIT
ASSOCIATION OF I RRITATED
RESIDENTS , a California non-profit
corporation,
Petitioner,
v.
U.S. ENVIRONMENTAL PROTECTION
AGENCY; M ICHAEL S. REGAN, in his
official capacity as Administrator of
the U.S. Environmental Protection
Agency; DEBORAH J ORDAN, in her
official capacity as Acting Regional
Administrator for Region IX of the
U.S. Environmental Protection
Agency,
Respondents,
SOUTH COAST AIR QUALITY
M ANAGEMENT DISTRICT ; SAN
J OAQUIN V ALLEY UNIFIED AIR
POLLUTION CONTROL DISTRICT ,
Intervenors.
No. 19-71223
OPINION
On Petition for Review of an Order of the
Environmental Protection Agency

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2 ASS ’ N OF I RRITATED RESIDENTS V. USEPA
Argued and Submitted July 7, 2020
Portland, Oregon
Filed August 26, 2021
Before: Mark J. Bennett and Eric D. Miller, Circuit Judges,
and Benita Y. Pearson,* District Judge.
Opinion by Judge Miller
SUMMARY**
Clean Air Act / Standing
The panel granted in part, and denied in part, a petition
for review of a final rule of the Environmental Protection
Agency (“EPA”) approving the State of California’s plan for
meeting the air quality standard for ozone in the San Joaquin
Valley, 84 Fed. Reg. 11,198 (Mar. 25, 2019).
The plan contained a single contingency measure that
would be activated if the other provisions of the plan do not
achieve reasonable further progress toward meeting the
standard. An environmental organization petitioned for
review, arguing that the contingency measure was
inadequate.
* The Honorable Benita Y. Pearson, United States District Judge for
the Northern District of Ohio, sitting by designation.
** This summary constitutes no part of the opinion of the court. It
has been prepared by court staff for the convenience of the reader.

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ASS ’ N OF I RRITATED RESIDENTS V. USEPA 3
The panel held that petitioner, Association of Irritated
Residents (“AIR”), a California nonprofit corporation with
members who reside in the Valley, met the requirements for
Article III standing. AIR’s members established injury in
fact by submitting declarations containing credible
allegations of respiratory distress as well as harm to their
recreational and aesthetic interests as a result of ozone
depletion in the Valley. The threat that the Valley will
continue to fail to meet the ozone standard–and therefore
that the contingency measure will be activated–is neither
conjectural nor hypothetical, but a reasonable inference from
the historical record. The panel also concluded that AIR’s
challenge was ripe for review.
AIR contended that the EPA’s approval of the
contingency measure in the State’s plan reflected an
unreasonable interpretation of the Clean Air Act and was
arbitrary and capricious because the measure provided only
a nominal emissions reduction of one ton per day. The panel
agreed that the EPA’s approval was arbitrary and capricious.
Under the Administrative Procedure Act, when an agency
changes its policy, it must display awareness that it is
changing position and show that there are good reasons for
the new policy. In approving a contingency measure that
provided a far lower emissions reduction, the EPA did not
acknowledge that it had changed its understanding of what
reasonable further progress meant. The panel rejected the
EPA’s contention that its new position was a response to this
court’s decision in Bahr v. EPA, 836 F.3d 1218 (9th Cir.
2016). The panel held that the EPA may not avoid the need
for robust contingency measures by assuming that they will
not be needed. Because the EPA did not provide a reasoned
explanation for approving the State plan, the rule was
arbitrary and capricious.

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4 ASS ’ N OF I RRITATED RESIDENTS V. USEPA
The panel rejected AIR’s challenge to the EPA’s
approval of the State’s Enhanced Enforcement Activities
Program. The EPA did not recognize the program as a stand-
alone contingency; instead the agency approved it as a plan
strengthening measure. The panel held that because the
program did not create any emission limitation that was less
stringent than one in effect in the state plan, nothing in the
Clean Air Act prohibited the State from pursuing it. The
panel further held that the program was consistent with the
statutory requirement that the measures included in the plan
be enforceable.
COUNSEL
Brent J. Newell (argued), Law Offices of Brent J. Newell,
Petaluma, California; Andrew L. Packard and William N.
Carlon, Law Offices of Andrew L. Packard, Petaluma,
California; for Petitioner.
Alan D. Greenberg (argued), Attorney; Jonathan D.
Brightbill, Principal Deputy Assistant Attorney General;
Environmental Defense Section, Environment and Natural
Resources Division, United States Department of Justice,
Denver, Colorado; Jefferson Wehling, Office of the
Regional Counsel, United States Environmental Protection
Agency, San Francisco, California; Geoffrey L. Wilcox,
Office of the General Counsel; United States Environmental
Protection Agency, Washington, D.C.; for Respondents.
Jessica E. Hafer Fierro (argued) and Annette A. Ballatore-
Williamson, San Joaquin Valley Unified Air Pollution
Control District, Fresno, California; Barbara Baird and Mary
J. Reichert, South Coast Air Quality Management District,
Diamond Bar, California; for Intervenors.

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ASS ’ N OF I RRITATED RESIDENTS V. USEPA 5
OPINION
MILLER, Circuit Judge:
The Environmental Protection Agency adopted a final
rule approving the State of California’s plan for meeting the
air quality standard for ozone in the San Joaquin Valley.
84 Fed. Reg. 11,198 (Mar. 25, 2019). The plan contains a
single contingency measure that will be activated if the other
provisions of the plan do not achieve reasonable further
progress toward meeting the standard. Arguing that the
contingency measure is inadequate, an environmental
organization petitions for review. Because we agree that the
agency’s approval of the plan was arbitrary and capricious,
we grant the petition in part and remand.
I
A
The Clean Air Act establishes “a cooperative state-
federal scheme for improving the nation’s air quality.”
Vigil v. Leavitt, 381 F.3d 826, 830 (9th Cir. 2004). Under the
Act, the EPA issues standards for atmospheric pollutants
such as ozone. 42 U.S.C. §§ 7408(a), 7409(a); see, e.g.,
40 C.F.R. § 50.15. States, in turn, establish plans to meet
those standards and submit them to the EPA for approval.
42 U.S.C. §§ 7407(a), 7410(a). When an area does not meet
a standard, it is designated a “nonattainment” area. See id.
§§ 7407(d)(1)(A), 7501(2). There are several degrees of
nonattainment, ranging from marginal to extreme, id.
§ 7511(a)(1), and each classification imposes increasingly
stringent requirements to reduce emissions and promote
progress toward attainment, id. § 7511a(b)(1)(A), (c)(2)(B),
(d), (e).

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6 ASS ’ N OF I RRITATED RESIDENTS V. USEPA
A state plan must “include enforceable emission
limitations” to attain the relevant air quality standard.
42 U.S.C. § 7410(a)(2)(A); see id. § 7502(c)(6); Committee
for a Better Arvin v. EPA, 786 F.3d 1169, 1176 (9th Cir.
2015). Plans covering nonattainment areas must also include
provisions to ensure “reasonable further progress,”
42 U.S.C. § 7502(c)(2), that is, “annual incremental
reductions in emissions” to achieve attainment, id.
§ 7501(1); see 40 C.F.R. § 51.1100(t) (defining “reasonable
further progress” for emissions relevant to meeting ozone
standards); id. § 51.1110(a)(2) (same). For extreme ozone
nonattainment areas, the plan must provide for reasonable
further progress of “at least 3 percent of baseline emissions
each year.” 42 U.S.C. § 7511a(c)(2)(B)(i), (d), (e).
The Act requires assessment of progress at triennial
“milestones.” 42 U.S.C. § 7511a(g)(1). At each milestone,
“the State shall determine whether each nonattainment area
. . . has achieved a reduction in emissions during the
preceding intervals equivalent to the total emission
reductions required to be achieved by the end of such
interval.” Id. If the State does not meet a milestone in an
extreme nonattainment area, it must submit a plan revision
within nine months. Id. § 7511a(g)(5).
Congress recognized that a State’s implementation plan
might not succeed. Thus, plans covering nonattainment areas
must “provide for the implementation of specific measures
to be undertaken if the area fails to make reasonable further
progress” or fails to attain the relevant air quality standard.
42 U.S.C. § 7502(c)(9). Those contingency measures “shall
. . . take effect in any such case without further action by the
State or the [EPA] Administrator.” Id. Similarly, any plan
revision covering an extreme nonattainment area “shall
provide for the implementation of specific measures to be

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ASS ’ N OF I RRITATED RESIDENTS V. USEPA 7
undertaken if the area fails to meet any applicable
milestone.” Id. § 7511a(c)(9); see id. § 7511a(d), (e). Those
measures also take effect automatically “upon a failure by
the State to meet the applicable milestone.” Id.
§ 7511a(c)(9), (d), (e); see also 80 Fed. Reg. 12,264,
12,285–86 (Mar. 6, 2015) (finalizing requirements for
contingency measures in state plans). By requiring
contingency measures, the Act closes any potential gap in
progress should a nonattainment area miss a milestone. See
42 U.S.C. §§ 7502(c)(9), 7511a(c)(9).
B
The San Joaquin Valley is a large inland area of
California extending from the Sacramento-San Joaquin
Delta in the north to the Tehachapi Mountains in the south.
The Valley has long struggled to attain air quality standards
for ozone. In 2012, the EPA classified the Valley as an
extreme nonattainment area for the 8-hour ozone standard.
See 40 C.F.R. § 51.1103(a), (d); 77 Fed. Reg. 30,088, 30,092
(May 21, 2012).
The San Joaquin Valley Air Pollution Control District is
responsible for developing the state implementation plan for
the Valley. 83 Fed. Reg. 44,528, 44,529 (Aug. 31, 2018).
Another state agency, the California Air Resources Board, is
responsible for submitting the state plan to the EPA for
approval. Id. We refer to these entities collectively as the
State.
In late 2018, the State proposed updates to its plan for
the Valley. The updates reflected a response to our decision
in Bahr v. EPA, 836 F.3d 1218 (9th Cir. 2016), in which we
held that contingency measures may not include measures
that have already been implemented in a state plan. Id.
at 1235–36; accord Sierra Club v. EPA, 985 F.3d 1055,

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8 ASS ’ N OF I RRITATED RESIDENTS V. USEPA
1067–68 (D.C. Cir. 2021). The State explained that previous
plans for the Valley had “featured contingency measures that
relied upon reductions from the continued implementation
of programs already adopted,” which “provided excess
emission reductions beyond what was required for
attainment or reasonable further progress.” Because those
measures could no longer count as contingency measures
after Bahr, the plan provided for a different contingency
measure: the repeal of a rule allowing for the sale of small
containers of paint. The plan also prescribed an “Enhanced
Enforcement Activities Program”—a menu of options to
reduce emissions if the State was unable to meet a milestone
or attainment.
The EPA approved the revised plan. 84 Fed. Reg.
at 11,198. The agency acknowledged that it had previously
“recommended in guidance that contingency measures
should provide emissions reductions approximately
equivalent to one year’s worth of [reasonable further
progress], which, with respect to ozone in the . . . Valley,”
amounted to about 11.4 tons per day. Id. at 11,205. The
agency estimated that the one contingency measure
proposed by the State—the repeal of the small-container
exemption for paint—would provide reductions of only one
ton per day. Id. at 11,206. But the agency stated that it now
“do[es] not believe that the contingency measures
themselves must provide for one year’s worth of [reasonable
further progress].” Id. Under its new approach, the agency
permitted the State to count “additional emission reductions
projected to occur that a state has not relied upon for
purposes of [reasonable further progress] or attainment . . .
and that result from measures the state has not adopted as
contingency measures.” Id.

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ASS ’ N OF I RRITATED RESIDENTS V. USEPA 9
The EPA also approved the Enhanced Enforcement
Activities Program, but it did not consider that program to
be “a stand-alone contingency measure.” 84 Fed. Reg.
at 11,204; see id. at 11,203. Instead, the agency approved the
program as “a [plan]-strengthening portion of the
contingency measure.” Id. at 11,204.
II
The Association of Irritated Residents (AIR), a
California nonprofit corporation with members who reside
in the Valley, petitions for review of the EPA’s final rule
approving the state plan. The San Joaquin Valley Air
Pollution Control District and the South Coast Air Quality
Management District have intervened in defense of the rule.
Although the EPA does not question AIR’s standing, the
intervening districts do, so we begin by considering their
argument.
To establish Article III standing, “a plaintiff must show
(1) it has suffered an ‘injury in fact’ that is (a) concrete and
particularized and (b) actual or imminent, not conjectural or
hypothetical; (2) the injury is fairly traceable to the
challenged action of the defendant; and (3) it is likely, as
opposed to merely speculative, that the injury will be
redressed by a favorable decision.” Friends of the Earth, Inc.
v. Laidlaw Env’t Servs. (TOC), Inc., 528 U.S. 167, 180–81
(2000); see also Lujan v. Defenders of Wildlife, 504 U.S.
555, 560–61 (1992). AIR meets those requirements.
It is well established “that environmental plaintiffs
adequately allege injury in fact when they aver that they use
the affected area and are persons ‘for whom the aesthetic and
recreational values of the area will be lessened’ by the
challenged activity.” Friends of the Earth, 528 U.S. at 183
(quoting Sierra Club v. Morton, 405 U.S. 727, 735 (1972));

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10 ASS ’ N OF I RRITATED RESIDENTS V. USEPA
accord Ecological Rts. Found. v. Pacific Lumber Co.,
230 F.3d 1141, 1149 (9th Cir. 2000). Applying that
reasoning, we have explained “that evidence of a credible
threat to the plaintiff’s physical well-being from airborne
pollutants falls well within the range of injuries to
cognizable interests that may confer standing.” Hall v.
Norton, 266 F.3d 969, 976 (9th Cir. 2001); see also Sierra
Club v. EPA, 762 F.3d 971, 977 (9th Cir. 2014).
AIR’s members have established injury in fact by
submitting declarations containing credible allegations of
respiratory distress as well as harm to their recreational and
aesthetic interests as a result of ozone pollution in the Valley.
But the districts argue that those injuries are not caused by
the EPA’s approval of the contingency measure in the
State’s plan, and, correspondingly, that setting aside the
plan’s approval would not redress the injuries. That is so,
they say, because the contingency measure has not yet been
activated, so its implementation is merely “hypothetical.”
We disagree. An injury is fairly traceable to a challenged
action as long as the links in the proffered chain of causation
“are ‘not hypothetical or tenuous’ and remain ‘plausib[le].’”
Maya v. Centex Corp., 658 F.3d 1060, 1070 (9th Cir. 2011)
(alteration in original) (quoting National Audubon Soc’y,
Inc. v. Davis, 307 F.3d 835, 849 (9th Cir. 2002)). Similarly,
a plaintiff can meet the redressability requirement by
showing that “it is likely, although not certain, that his injury
can be redressed by a favorable decision.” Wolfson v.
Brammer, 616 F.3d 1045, 1056 (9th Cir. 2010); accord
Friends of the Earth, 528 U.S. at 181. Neither part of the test
demands absolute certainty, and both are satisfied here.
The Valley has long been “an area with some of the worst
air quality in the United States,” and it has repeatedly failed
to meet air quality standards. Committee for a Better Arvin,

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ASS ’ N OF I RRITATED RESIDENTS V. USEPA 11
786 F.3d at 1173. In 2001, the EPA found that the Valley did
not attain the 1-hour ozone standard that was then in effect
and reclassified the Valley as a severe nonattainment area
for the 1-hour ozone standard. 66 Fed. Reg. 56,476, 56,481
(Nov. 8, 2001). Since 2004, the Valley has been designated
as a nonattainment area for the 8-hour ozone standard. See
69 Fed. Reg. 23,858, 23,888–89 (Apr. 30, 2004). And in
2012, the Valley was reclassified as an extreme
nonattainment area for the 8-hour ozone standard. See
40 C.F.R. § 51.1103(a), (d); 77 Fed. Reg. at 30,092. The
threat that the Valley will continue to fail to meet the ozone
standard—and therefore that the contingency measure will
be activated—is neither conjectural nor hypothetical, but a
reasonable inference from the historical record.
As the districts acknowledge, their arguments relate
more to ripeness than to standing. The ripeness doctrine,
which aims to avoid premature and potentially unnecessary
adjudication, “is ‘drawn both from Article III limitations on
judicial power and from prudential reasons for refusing to
exercise jurisdiction.’” National Park Hosp. Ass’n v.
Department of Interior, 538 U.S. 803, 808 (2003) (quoting
Reno v. Catholic Soc. Servs., Inc., 509 U.S. 43, 57 n.18
(1993)). “The constitutional component of ripeness overlaps
with the ‘injury in fact’ analysis for Article III standing,” and
therefore “the inquiry is largely the same: whether the issues
presented are ‘definite and concrete, not hypothetical or
abstract.’” Wolfson, 616 F.3d at 1058 (quoting Thomas v.
Anchorage Equal Rts. Comm’n, 220 F.3d 1134, 1139 (9th
Cir. 2000) (en banc)). For the reasons we have already
explained, constitutional ripeness is satisfied here.
To assess prudential ripeness, we must “evaluate both
the fitness of the issues for judicial decision and the hardship
to the parties of withholding court consideration.” Abbott

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12 ASS ’ N OF I RRITATED RESIDENTS V. USEPA
Labs. v. Gardner, 387 U.S. 136, 149 (1967); see Colwell v.
Department of Health & Hum. Servs., 558 F.3d 1112, 1124
(9th Cir. 2009). The issue here is fit for review because it is
a purely legal question presented in the concrete setting of
the EPA’s approval of the specific plan adopted by the State.
See Whitman v. American Trucking Ass’ns, 531 U.S. 457,
479 (2001) (concluding that an issue was ripe when it was
“purely one of statutory interpretation that would not benefit
from further factual development of the issues presented”
(internal quotation marks omitted)); see also Oklevueha
Native Am. Church of Haw., Inc. v. Holder, 676 F.3d 829,
838 (9th Cir. 2012); Clean Air Implementation Project v.
EPA, 150 F.3d 1200, 1204 (D.C. Cir. 1998). And delaying
review would cause hardship to AIR because it would mean
that the allegedly inadequate contingency measure could not
be reviewed until it was already implemented, when any
review would be too late to redress the injuries suffered by
AIR’s members. We conclude that the challenge is ripe for
review.
III
According to AIR, the EPA’s approval of the
contingency measure in the State’s plan reflects an
unreasonable interpretation of the Clean Air Act and is
arbitrary and capricious because the measure will provide
only a nominal emissions reduction of one ton per day. The
EPA responds with the observation that the statute does not
“specify the quantity of emission reductions that a
contingency measure must provide,” and it argues that “there
exists no binding requirement for the particular amount of
emission reductions that EPA must require in a contingency
measure.”
All parties agree that we must review the EPA’s
interpretation of the Clean Air Act using the deferential

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ASS ’ N OF I RRITATED RESIDENTS V. USEPA 13
framework of Chevron U.S.A. Inc. v. NRDC, Inc., 467 U.S.
837 (1984). The first step under Chevron is to determine
whether Congress has “directly addressed the precise
question at issue.” Id. at 843. AIR does not argue that the
EPA’s interpretation fails at step one of Chevron but instead
relies on step two, arguing that the agency has adopted an
unreasonable interpretation of the statute. See id. at 843–44.
AIR observes that the EPA has long taken the position that
contingency measures “should be approximately equal to the
emissions reductions necessary to demonstrate [reasonable
further progress] for one year.” 57 Fed. Reg. 13,498,
13,543–44 (Apr. 16, 1992); see also 80 Fed. Reg. at 12,286
(“The EPA’s long-standing interpretation is that a 3 percent
emissions reduction from the [reasonable further progress]
baseline . . . is the minimum contingency measure adoption
requirement.”). In AIR’s view, the EPA’s new, contrary
interpretation of the statute is unreasonable.
As the District of Columbia Circuit has observed, there
is considerable overlap between a challenge at Chevron step
two and an argument that an agency’s action is arbitrary and
capricious: “Whether a statute is unreasonably interpreted is
close analytically to the issue whether an agency’s actions
under a statute are unreasonable.” General Instrument Corp.
v. FCC, 213 F.3d 724, 732 (D.C. Cir. 2000); accord
Judulang v. Holder, 565 U.S. 42, 52 n.7 (2011); see also
Diaz-Reynoso v. Barr, 968 F.3d 1070, 1076 (9th Cir. 2020).
We think AIR’s challenge is most appropriately evaluated
under the arbitrary-and-capricious framework, and we agree
with AIR that even assuming that the EPA’s interpretation
of the statute is permissible, its action cannot survive review.
Under the Administrative Procedure Act, “[w]hen an
administrative agency sets policy, it must provide a reasoned
explanation for its action.” Judulang, 565 U.S. at 45. Of

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14 ASS ’ N OF I RRITATED RESIDENTS V. USEPA
particular relevance here, when an agency changes its policy,
it “must at least ‘display awareness that it is changing
position’ and ‘show that there are good reasons for the new
policy.’” Encino Motorcars, LLC v. Navarro, 136 S. Ct.
2117, 2126 (2016) (quoting FCC v. Fox Television Stations,
Inc., 556 U.S. 502, 515 (2009)). The requirement of a
reasoned explanation “is not a high bar, but it is an
unwavering one.” Judulang, 565 U.S. at 45. The EPA’s
reasoning does not clear that bar.
In the challenged rule, the EPA acknowledged the
traditional relationship between contingency measures and
the requirement of reasonable further progress: “The
purpose of emissions reductions from implementation of
contingency measures is to ensure that, in the event of a
failure to meet a[] [reasonable further progress] milestone or
a failure to attain the [air quality standards] by the applicable
attainment date, the state will continue to make progress
toward attainment at a rate similar to that specified under the
[reasonable further progress] requirements.” 84 Fed. Reg.
at 11,205. It also recognized that it had adopted a specific
understanding of the necessary scale of contingency
measures, having previously said “that contingency
measures should provide emissions reductions
approximately equivalent to one year’s worth of [reasonable
further progress], which, with respect to ozone in the San
Joaquin Valley nonattainment area,” is about 11.4 tons per
day. Id.
In approving a contingency measure that provides a far
lower emissions reduction—only one ton per day—the EPA
did not say that it had changed its understanding of what
reasonable further progress means. Instead, it said that
“contingency measures themselves” do not need to “provide
for one year’s worth of [reasonable further progress].”

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ASS ’ N OF I RRITATED RESIDENTS V. USEPA 15
84 Fed. Reg. at 11,206. Now, according to the agency, a
State can combine emissions reductions achieved through
contingency measures with “sources of surplus emissions
reductions,” that is, “additional emission reductions
projected to occur that a state has not relied upon for
purposes of [reasonable further progress] or attainment or to
meet other nonattainment plan requirements.” Id.
The EPA described its new position as a response to our
decision in Bahr, but it cannot be reconciled with our
reasoning in that case. Under Bahr, contingency measures
may not be measures that the State is already implementing
in its plan. 836 F.3d at 1236. Our decision was based on the
plain language of the statute, which reflects the
commonsense idea that if currently existing measures are not
successful in ensuring progress, then it is unreasonable to
rely upon them as contingency measures. Id. In Sierra Club,
which endorsed the holding of Bahr, the District of
Columbia Circuit explained the idea well: “[M]easures that
are already implemented are not measures ‘to take effect’ or
‘to be undertaken’ if the area fails to satisfy the applicable
requirements. . . . They are simply measures that have
failed.” 985 F.3d at 1068 (quoting 42 U.S.C. § 7502(c)(9)).
But here, the agency has relied on “surplus” emissions
reductions from existing measures to make up for what
everyone agrees would otherwise be an inadequate
contingency measure. That approach is a transparent effort
to circumvent Bahr. Having been told that it could not rely
on projected emissions reductions from existing measures as
contingency measures, the agency has simply relabeled them
“surplus reductions.” In doing so, it has severed the
relationship between the requirement of contingency
measures and the benchmark of reasonable further progress,
without an adequate explanation of why the new—and far
more modest—contingency measure is reasonable.

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16 ASS ’ N OF I RRITATED RESIDENTS V. USEPA
The EPA argues that its prior statements tying
contingency measures to reasonable further progress did not
have the force of law. That is beside the point because the
EPA still must give a reasoned explanation for departing
from agency practice or policy. See Encino Motorcars,
136 S. Ct. at 2125–26. If already-implemented measures
cannot themselves be contingency measures—and Bahr
makes clear that they cannot—then neither can they be a
basis for declining to establish contingency measures that
would otherwise be appropriate.
The premise of the EPA’s rule appears to be that
contingency measures will not be needed “because already-
implemented measures (although not relied upon for the
purpose[] of meeting the statutory contingency measure
requirement) will also ensure sufficient continued progress
in the event of a failure to achieve a[] [reasonable further
progress] milestone.” 84 Fed. Reg. at 11,206. But the reason
the statute requires contingency measures is to have a
backup that can be put in place immediately in case already-
implemented measures in a plan fail to achieve reasonable
further progress. See Sierra Club, 985 F.3d at 1068; Bahr,
836 F.3d at 1235. The agency may not avoid the need for
robust contingency measures by assuming that they will not
be needed. Because the agency did not provide a reasoned
explanation for approving the state plan, the rule is arbitrary
and capricious.
IV
AIR also challenges the EPA’s approval of the State’s
Enhanced Enforcement Activities Program. The scope of
that challenge is narrow because the EPA recognized that the
program “fails to include all of the characteristics necessary
to provide for a stand-alone contingency measure” and
therefore did not approve it as one. 84 Fed. Reg. at 11,204.

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ASS ’ N OF I RRITATED RESIDENTS V. USEPA 17
Nor did the agency “credit the [program] as achieving any
emissions reductions.” Id. at 11,206. Instead, the agency
approved it as a plan “strengthening” measure. Id. at 11,204.
The dispute, then, concerns only whether such a measure is
permissible under the Act.
The Act generally charges the States with responsibility
for meeting air quality standards, and it permits the adoption
of emissions limitations. 42 U.S.C. §§ 7407(a), 7416. The
only restriction is “that if an emission standard or limitation
is in effect under an applicable implementation plan . . . ,
such State or political subdivision may not adopt or enforce
any emission standard or limitation which is less stringent
than the standard or limitation under such plan.” Id. § 7416.
Because the program does not create any emission limitation
that is less stringent than one in effect in the state plan,
nothing in the statute prohibits the State from pursuing it.
Of course, once a State seeks to incorporate an additional
emissions limitation into its plan, section 7410(a)(2)(A)
requires that the limitation be enforceable. See Committee
for a Better Arvin, 786 F.3d at 1176. The EPA acknowledges
that the program must be enforceable to be incorporated into
the plan, and it argues that those components of the program
that were approved as part of the plan are indeed
enforceable. We agree. Under the program, if an area does
not meet a milestone or attainment, the State must prepare a
report within 60 days that “include[s] a determination of the
probable causes of the failure and . . . state[s] the type and
quantity of additional enforcement resources that will be
utilized within the failing area along with an explanation of
why the type and quantity of enforcement resources
allocated (Enhanced Enforcement Program) are
appropriate.” The measures identified in the program must
then be implemented. If the report is not drafted, or if the

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18 ASS ’ N OF I RRITATED RESIDENTS V. USEPA
chosen program is not implemented, those failings may be
challenged either by the EPA or by citizens. See 42 U.S.C.
§§ 7509, 7604(a). The program is therefore consistent with
the statutory requirement that measures included in the plan
be enforceable. See Committee for a Better Arvin, 786 F.3d
at 1177.
PETITION GRANTED in part and DENIED in part;
REMANDED.

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