State of New York v. EPA ( 2020 )


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  •  United States Court of Appeals
    FOR THE DISTRICT OF COLUMBIA CIRCUIT
    Argued May 7, 2020                     Decided July 14, 2020
    No. 19-1231
    STATE OF NEW YORK, ET AL.,
    PETITIONERS
    v.
    ENVIRONMENTAL PROTECTION AGENCY AND ANDREW
    WHEELER, IN HIS OFFICIAL CAPACITY AS ADMINISTRATOR OF
    THE U.S. ENVIRONMENTAL PROTECTION AGENCY,
    RESPONDENTS
    ADIRONDACK COUNCIL, ET AL.,
    INTERVENORS
    On Petition for Review of a Final Action of the
    United States Environmental Protection Agency
    Steven C. Wu, Deputy Solicitor General, Office of the
    Attorney General for the State of New York, argued the cause
    for petitioners. With him on the briefs were Letitia James,
    Attorney General for the State of New York, Barbara D.
    Underwood, Solicitor General, Morgan A. Costello and
    Claiborne E. Walthall, Assistant Attorneys General, Gurbir S.
    Grewal, Attorney General for the State of New Jersey, Lisa
    Morelli, Deputy Attorney General, and Christopher G. King,
    Senior Counsel, New York City Law Department.
    2
    Joshua A. Berman argued the cause for petitioners-
    intervenors Sierra Club, et al. With him on the briefs were Sean
    H. Donahue, Graham G. McCahan, Vickie L. Patton, and
    Liana James.
    Samara M. Spence, Attorney, U.S. Department of Justice,
    argued the cause for respondent. With her on the brief were
    Jonathan Brightbill, Principal Deputy Assistant Attorney
    General, and Abirami Vijayan and Stephanie L. Hogan,
    Counsel, U.S. Environmental Protection Agency. Sarah A.
    Buckley, Attorney, U.S. Department of Justice, entered an
    appearance.
    David M. Flannery, Kathy G. Beckett, Edward L. Kropp,
    Samuel B. Boxerman, Samina M. Bharmal, David M.
    Friedland, Laura K. McAfee, E. Carter Chandler Clements,
    Norman W. Fichthorn, Steven P. Lehotsky, and Michael B.
    Schon were on the brief for respondents-intervenors Midwest
    Ozone Group, et al. Laura M. Goldfarb, Amy M. Smith and
    Peter Tolsdorf entered appearances.
    Joseph A. Newberg II and Mary Ann Lee were on the brief
    for amicus curiae Commonwealth of Kentucky, Energy and
    Environment Cabinet in support of respondents.
    Before: SRINIVASAN, Chief Judge, and GRIFFITH and
    MILLETT, Circuit Judges.
    Opinion for the Court filed by Circuit Judge MILLETT.
    Concurring opinion filed by Circuit Judge GRIFFITH.
    MILLETT, Circuit Judge: Air pollutants do not stay still.
    Nor do they respect state borders. That has created a “complex
    problem”—namely that “air pollution emitted in one State[]
    3
    [can] caus[e] harm in other States.” EPA v. EME Homer City
    Generation, L.P., 
    572 U.S. 489
    , 495 (2014).
    This case involves a challenge to the Environmental
    Protection Agency’s asserted failure to address cross-border
    pollution under the Clean Air Act’s Good Neighbor Provision,
    42 U.S.C. § 7410(a)(2)(D)(i). The State of New York
    petitioned the EPA to find that power-generating and other
    facilities in nine different States were violating the Good
    Neighbor Provision by producing emissions that contributed
    significantly to New York’s difficulty attaining or maintaining
    compliance with the 2008 and 2015 National Ambient Air
    Quality Standards for ozone.
    The EPA denied New York’s petition on the ground that it
    failed to meet the agency’s standard for establishing a violation
    of the Good Neighbor Provision and, in particular, for
    demonstrating that cost-effective controls could be imposed on
    the pollution sources. The State of New York, the State of New
    Jersey, and the City of New York petitioned this court for
    review.
    We grant the petition for review. The EPA offered
    insufficient reasoning for the convoluted and seemingly
    unworkable showing it demanded of New York’s petition. In
    addition, the EPA’s finding that New York did not have an air
    quality problem under the 2008 National Ambient Air Quality
    Standards for ozone relied on two faulty interpretations of the
    Clean Air Act that have since been invalidated. See
    Maryland v. EPA, No. 18-1285, slip op. at 25–34 (D.C. Cir.
    May 19, 2020). For those reasons, we vacate the EPA’s
    decision and remand for further proceedings not inconsistent
    with this opinion.
    4
    I
    A
    The Clean Air Act, 42 U.S.C. §§ 7401 et seq., directs the
    EPA to establish and periodically revise National Ambient Air
    Quality Standards, or NAAQS, that set the maximum allowable
    concentrations for various air pollutants, including ozone. 42
    U.S.C. §§ 7408(a), 7409. To measure compliance with the
    NAAQS, the EPA, “in coordination with state governments,
    divides the country geographically into ‘air quality control
    regions.’” Natural Res. Defense Council v. EPA, 
    777 F.3d 456
    ,
    458 (D.C. Cir. 2014) (formatting modified) (quoting 42 U.S.C.
    § 7407). While some air quality control regions “lie within a
    single state[,] * * * others encompass portions of two or more
    states.” Maryland, slip op. at 6 (quoting Delaware Dep’t of
    Natural Res. & Environmental Control v. EPA, 
    895 F.3d 90
    ,
    94 (D.C. Cir. 2018)).
    Once new air quality standards go into effect, each State
    must develop an implementation plan to ensure the standards
    are met within the State’s air quality control region. See 42
    U.S.C. § 7410(a)(1); see also
    id. § 7407(b)–(e).
    In addition,
    those plans must prohibit “any source or * * * emissions
    activity within the State from emitting any air pollutant in
    amounts which will * * * contribute significantly to
    nonattainment in, or interfere with maintenance by, any other
    State with respect to” the NAAQS.
    Id. § 7410(a)(2)(D)(i).
    That subpart is known as the “Good Neighbor Provision.” See
    Wisconsin v. EPA, 
    938 F.3d 303
    , 309–319 (D.C. Cir. 2019).
    Under Section 110 of the Clean Air Act, the EPA must
    review each State’s implementation plan and ensure its
    compliance with statutory requirements, including the Good
    Neighbor provision. See 42 U.S.C. § 7410(k)(1)–(4). If a State
    fails to timely correct a deficiency in its plan, then the EPA will
    5
    promulgate a federal implementation plan for the relevant
    region(s).
    Id. § 7410(c)(1).
    Section 126(b) of the Clean Air Act, 42 U.S.C. § 7426(b),
    creates an additional mechanism for enforcing the Good
    Neighbor Provision. It authorizes affected States or local
    subdivisions to petition the EPA to make a “finding that any
    major source or group of stationary sources emits or would
    emit any air pollutant in violation of the prohibition of [the
    Good Neighbor Provision.]” Id.1
    Under Section 126(b), the EPA must generally respond to
    the petition “[w]ithin 60 days after receipt of [such] petition
    * * * and after public hearing[.]” 42 U.S.C. § 7426(b). The
    agency may, however, grant itself an extension of up to six
    months “upon a determination that such extension is necessary
    to afford the public, and the agency, adequate opportunity to
    carry out the purposes of th[e] subsection.”
    Id. § 7607(d)(1)(N),
    (d)(10).
    If an existing pollution source in another jurisdiction is
    found to be in violation of the Good Neighbor Provision, that
    source generally must cease operation within three months. 42
    U.S.C. § 7426(c). But the EPA may allow continued operation
    if the “source complies with such emission limitations and
    compliance schedules * * * as may be provided by the
    Administrator to bring about compliance * * * as expeditiously
    1
    Section 126(b) cross-references Section 110(a)(2)(D)(ii) of the
    Clean Air Act, 42 U.S.C. § 7410(a)(2)(D)(ii). But that is understood
    to be a scrivener’s error. Appalachian Power Co. v. EPA, 
    249 F.3d 1032
    , 1040–1044 (D.C. Cir. 2001). For present purposes, the proper
    cross-reference is the Good Neighbor Provision, 42 U.S.C.
    § 7410(a)(2)(D)(i). See Appalachian 
    Power, 249 F.3d at 1040
    –1044.
    6
    as practicable, but in no case later than three years after the date
    of such finding.”
    Id. B Over
    time, the EPA has promulgated increasingly
    stringent ozone standards.2 As relevant here, in 2008, the EPA
    lowered the acceptable ozone level, measured over eight hours,
    from 80 parts per billion to 75 parts per billion. 40 C.F.R.
    § 50.15. And in 2015, it promulgated an even more restrictive
    ozone standard of 70 parts per billion.
    Id. § 50.19.
    Both the
    2008 NAAQS and the more stringent 2015 NAAQS remain in
    effect with differing deadlines for compliance.
    Depending on the degree of nonattainment, the Clean Air
    Act provides a deadline by which each air quality control
    region must achieve compliance. See 42 U.S.C. § 7511(a)(1),
    (b)(1). The more severe the noncompliance, the more time the
    region has to remedy the problem. See
    id. If the
    region fails to
    meet the compliance deadline, the EPA will reclassify it to a
    higher severity level. See
    id. § 7511(b)(2).
    That, in turn,
    automatically extends the deadline for compliance to the
    attainment date for that higher level.
    As relevant here, areas in “serious” nonattainment of the
    2008 NAAQS have a statutory attainment deadline of 2021.
    See Determination of Attainment and Reclassification for 2008
    Ozone NAAQS, 84 Fed. Reg. 44,238, 44,244 (Aug. 23, 2019).
    Areas in “moderate” nonattainment of the 2015 NAAQS have
    2
    See, e.g., 44 Fed. Reg. 8202, 8217 (Feb. 8, 1979) (setting the
    primary ozone standard at 120 parts per billion); 62 Fed. Reg.
    38,856, 38,885 (July 18, 1997) (at 80 parts per billion); 73 Fed. Reg.
    16,436, 16,483 (March 27, 2008) (at 75 parts per billion); 80 Fed.
    Reg. 65,292, 65,362 (Oct. 26, 2015) (at 70 parts per billion).
    7
    a 2024 deadline for compliance. Response to Section 126(b)
    Petition from New York, 84 Fed. Reg. 56,058, 56,072 n.48
    (Oct. 18, 2019).
    C
    The New York-Northern New Jersey-Long Island, New
    York-New Jersey-Connecticut Area (“New York Metropolitan
    Area” or “Area”) is a multistate air quality control region. It is
    currently in “serious” nonattainment of the 2008 ozone
    NAAQS, having twice failed to meet previously applicable
    statutory deadlines for attainment. See Determination of
    Attainment and Reclassification for 2008 Ozone NAAQS, 84
    Fed. Reg. at 44,238, 44,244 (reclassifying seven areas,
    including the New York Metropolitan Area, to serious
    nonattainment); see also
    id. at 44,243
    tbl.2.                The
    reclassification to serious nonattainment triggered a July 2021
    attainment deadline.
    Id. at 44,244.
    The Area is also in “moderate” nonattainment of the 2015
    NAAQS, with a 2024 deadline for attainment. Additional Air
    Quality Designations for 2015 Ozone NAAQS, 83 Fed. Reg.
    25,776, 25,821 (June 4, 2018); see 84 Fed. Reg. at 56,072 n.48.
    In March 2018, New York filed a Section 126(b) petition
    (“Petition”) that asked the EPA to find that approximately 350
    sources of nitrogen oxides in nine States were contributing
    significantly to nonattainment in the New York Metropolitan
    Area under the 2008 and 2015 NAAQS. J.A. 58, 60, 76.3 The
    3
    The Petition also alleged that these out-of-state sources were
    interfering with attainment in Chautauqua County, New York.
    J.A. 60.    New York’s and the Intervenor Environmental
    Associations’ arguments before this court focus exclusively on the
    8
    Petition pointed to Illinois, Indiana, Kentucky, Maryland,
    Michigan, Ohio, Pennsylvania, Virginia, and West Virginia as
    the sources of infiltrating ozone pollution. J.A. 60. New
    York’s modeling projected that the nine States would
    contribute at least one percent of the 2008 NAAQS (that is, at
    least 0.75 parts per billion) to at least one nonattaining ozone
    monitor in the New York Metropolitan Area. J.A. 60, 69.
    Within those nine States, the Petition focused the need for
    regulation on facilities that emit at least 400 tons of nitrogen
    oxides per year. See J.A. 60, 68, 76.4
    Rather than resolving the Petition within the 60-day
    statutory deadline, 42 U.S.C. § 7426(b), the EPA granted itself
    a six-month extension of time. Extension of Deadline, 83 Fed.
    Reg. 21,909, 21,910–21,912 (May 11, 2018); see also 42
    U.S.C. § 7607(d)(1)(N), (d)(10) (authorizing the EPA to grant
    itself an extension under certain circumstances).
    When the EPA missed that extended deadline, New York
    filed suit to compel a decision. The United States District
    Court for the Southern District of New York ordered the EPA
    to grant or deny the Petition by September 2019. See New York
    New York Metropolitan Area. So we do not address the EPA’s
    findings with respect to Chautauqua County.
    4
    New Jersey, like the nine listed States, was projected to
    contribute at least 0.75 parts per billion to ozone levels in the New
    York Metropolitan Area. J.A. 69. The Petition nevertheless did not
    list New Jersey as a potential violator because New York’s modeling
    indicated that the 400-ton-per-year sources in New Jersey did “not
    significantly contribute to any nonattainment or maintenance
    monitors.” J.A. 71.
    9
    v. Wheeler, No. 19-CV-3287, 
    2019 WL 3337996
    , at *2
    (S.D.N.Y. July 25, 2019).
    After undertaking notice and comment procedures and
    conducting a public hearing, the EPA issued a final decision
    denying the Petition on September 20, 2019. 84 Fed. Reg. at
    56,093. The decision was published in the Federal Register the
    next month.
    Id. In evaluating
    the Petition, the EPA applied a four-step
    framework derived from prior rulemakings on the interstate
    transport of ozone. 84 Fed. Reg. at 56,058, 56,062–56,063.
    Those steps are: (1) identifying downwind areas that have
    trouble attaining or maintaining the NAAQS; (2) determining
    which upwind States’ emissions are “linked” to downwind air
    quality problems; (3) ascertaining which of those linked States’
    upwind sources “significantly contribute” to nonattainment or
    interfere with maintenance of the NAAQS in a downwind area;
    and (4) implementing emission reductions/budgets within the
    upwind States.
    Id. at 56,062.
    The EPA imposed the burden of satisfying each of those
    steps on New York as the Section 126(b) petitioner. See 84
    Fed. Reg. at 56,069–56,070. The EPA also construed
    Section 126(b) as allowing States to challenge interstate
    transport of pollution only when it impacted downwind
    receptors “within their geographical borders,” even if the
    upwind pollutants impede attainment in the air quality region
    of which the State is a part.
    Id. at 56,080;
    see also
    id. at 56,081
    & n.70.
    With respect to Step 1 of the four-part framework, the EPA
    found an air quality problem in the New York Metropolitan
    Area under the 2015 NAAQS. 84 Fed. Reg. at 56,080–56,081.
    But it found no such attainment problem under the 2008
    NAAQS.
    Id. The EPA
    reached that conclusion by treating
    10
    2023 as the relevant year for evaluating the existence of an air
    quality problem under the 2008 NAAQS. Id.; see also
    id. at 56,074
    (“The EPA disagrees that it is inappropriate to rely on
    the 2023 modeling because it does not align with a particular
    attainment date.”). On that basis, the EPA denied the portion
    of the Petition seeking to enforce the 2008 NAAQS. Rather
    than project air quality in 2021—the year by which attainment
    was legally required—the EPA found that “New York has not
    demonstrated that there will be a nonattainment or maintenance
    problem” in 2023. The EPA’s own analysis also projected no
    air quality problems under the 2008 ozone NAAQS by 2023.
    Id. at 56,080–56,081.
    The EPA agreed with New York, though, that the New
    York Metropolitan Area would likely be in nonattainment of
    the 2015 NAAQS in 2023. See 84 Fed. Reg. at 56,080–56,081.
    At Step 2, the EPA “assum[ed], without deciding” that the
    emissions in the nine States identified in the Petition were
    “linked” to air quality problems in the New York Metropolitan
    Area. 84 Fed. Reg. at 56,082.
    At Step 3, the EPA denied the Petition in full based on
    New York’s failure to carry its assigned burden of establishing
    significant contributions from upwind sources under either the
    2008 or 2015 NAAQS. In particular, the EPA decided that the
    Petition’s “assessment of whether the sources” could be
    “further controlled through implementation of cost-effective
    controls [was] insufficient[.]” 84 Fed. Reg. at 56,059; see also
    id. at 56,088–56,089.
    The EPA reasoned that New York could have met its
    evidentiary burden of demonstrating the availability of cost-
    effective controls by producing “one or more of the following”
    analyses:
    11
    (i) Verifying that the named sources whose emissions
    are those from the most recent emissions inventory
    continue to emit [nitrogen oxides] at the same rate or
    continue to operate; (ii) describing or quantifying
    potentially available emissions reductions from the
    named        sources       (i.e.,       the      control
    technologies/techniques and the costs of those control
    technologies/techniques);       (iii) describing     the
    downwind air quality impacts of controlling the
    named sources relative to other sources; or
    (iv) providing information on the relative cost of the
    available emissions reductions and whether they are
    less expensive than other reductions from other
    sources.
    84 Fed. Reg. at 56,088–56,089.
    The EPA then added that it could “[]not determine whether
    it would be appropriate to regulate any of the hundreds of”
    named sources unless they were all “compared to one another
    or * * * compared to other, unnamed sources in the same
    upwind states or in other states.” 84 Fed. Reg. at 56,090. In
    the EPA’s view, this comparison must involve
    identifying the current operating status of each named
    facility, the magnitude of emissions from each
    emitting unit within each named facility, the existing
    controls on each of these emissions units, additional
    control options on each emissions unit, the cost of
    each potential control option, the emissions
    reductions potential resulting from the installation of
    controls, and potential air quality impacts of
    emissions reductions.
    Id. 12 In
    addition to finding that New York failed to carry its
    burden with respect to Step 3, the EPA concluded that a prior
    Cross-State Air Pollution Rule Update, which we shall refer to
    as the 2008 Update Rule, had fully addressed any Good
    Neighbor Provision violations arising in the nine named States.
    84 Fed. Reg. at 56,089 (“[T]he EPA has now determined * * *
    that the emissions reductions required under the * * * [2008]
    Update [Rule] fully address the good neighbor requirements
    with respect to the 2008 ozone NAAQS for all the States named
    in the [P]etition.”); see Cross-State Air Pollution Rule Update
    for the 2008 Ozone NAAQS, 81 Fed. Reg. 74,504 (Oct. 26,
    2016).
    The State of New York, the State of New Jersey, and the
    City of New York petitioned this court for review. Three
    environmental organizations intervened in support of the
    petitioning States.5 Several parties (collectively, “Industry
    Intervenors”) separately intervened in support of the EPA.6 On
    December 20, 2019, this court granted expedited review.
    II
    This court has jurisdiction under Section 307(b)(1) of the
    Clean Air Act. See 42 U.S.C. § 7607(b)(1); see also Sierra
    Club v. EPA, 
    955 F.3d 56
    , 61 (D.C. Cir. 2020).
    5
    The intervening environmental organizations are Adirondack
    Counsel, Environmental Defense Fund, and Sierra Club.
    6
    The Industry Intervenors are: Midwest Ozone Group, the Air
    Stewardship Coalition, GenOn Holdings, LLC, the National
    Association of Manufacturers, and the Chamber of Commerce of the
    United States of America.
    13
    We may set aside the EPA’s decision under Section 126 if
    it is “arbitrary, capricious, an abuse of discretion, or otherwise
    not in accordance with law.” 42 U.S.C. § 7607(d)(1)(N),
    (d)(9); see also Maryland, slip op. at 18 (“[W]e apply the same
    standard of review under the Clean Air Act as we do under the
    Administrative Procedure Act.”) (quoting Allied Local & Reg’l
    Mfrs. Caucus v. EPA, 
    215 F.3d 61
    , 68 (D.C. Cir. 2000)).
    III
    The EPA’s reasons for rejecting New York’s Petition were
    arbitrary and capricious in two respects.
    First, the EPA failed to provide a reasoned explanation for
    why, under Step 3 of its framework, the Petition failed to show
    that the named sources contributed significantly to downwind
    nonattainment. The EPA’s test, at best, was a moving target
    and, at worst, demanded likely unattainable standards of proof.
    Second, binding circuit precedent flatly rejects the two
    grounds on which the EPA relied in deciding, under Step 1, that
    the New York Metropolitan Area did not have a cognizable air
    quality problem under the 2008 NAAQS.
    A
    The EPA denied the Petition in full, as to compliance with
    both the 2008 and 2015 NAAQS, under Step 3. Specifically,
    the EPA pointed to perceived inadequacies in New York’s
    evidence that cost-effective emission reductions could be
    imposed at the sources of the offending contamination. 84 Fed.
    Reg. at 56,059, 56,088–56,089.
    The central problem is that the standard by which the EPA
    deemed New York’s cost-effectiveness showing to be
    insufficient is impossible to discern because the explanation
    14
    kept shifting. And if the standard truly means what the EPA’s
    decision at times says, it would be nigh impossible to meet.
    First, the EPA’s decision denying the Petition said that
    New York could have carried its burden by undertaking “one
    or more of” four possible analyses. 84 Fed. Reg. at 56,088–
    56,089. By way of reminder, those were: (i) “[v]erifying that
    the named sources * * * continue to emit [nitrogen oxides] at
    the same rate or continue to operate”; (ii) “describing or
    quantifying potentially available emissions reductions from the
    named sources”; (iii) “describing the downwind air quality
    impacts of controlling the named sources relative to other
    sources”; and (iv) evaluating “the relative cost of the available
    emissions reductions and whether they are less expensive than
    other reductions from other sources.”
    Id. at 56,088–56,089.
    Taking the EPA at its word, the Petition’s satisfactory
    demonstration of any “one” of those prongs should have
    sufficed. 84 Fed. Reg. at 56,088.
    Yet the EPA denied the Petition without any reasoned
    explanation as to how New York failed to satisfy the first of the
    four analyses, in particular with respect to sources that are
    electric generating units, or “EGUs.” J.A. 76 (“Appendix B
    includes average emission rates by EGU facility for the 2014
    to 2016 period (these data are unavailable for non-EGUs)[.]”);
    see also J.A. 90–92 (listing EGU emission rates). The agency’s
    decision never offered a coherent explanation for why it
    nonetheless rejected the Petition in full at Step 3. It simply
    went on to discuss more potential hurdles for New York’s
    Petition to clear. 84 Fed. Reg. at 56,089–56,090.
    At oral argument, the agency could not say whether New
    York had satisfied the first of the four listed analyses. Counsel
    simply said it was “questionable” whether the first analytical
    option had been met. Oral Arg. Tr. 41:22–24. But the EPA
    15
    cannot sensibly reject a petition on the ground that it has not
    yet figured out if the information provided is sufficient.
    Perhaps recognizing the problem, the EPA sidestepped the
    issue by claiming that the four analyses proposed by the agency
    are not “a specific test,” and instead simply “lay[] out the
    categories of things [the agency] is looking for.” Oral Arg. Tr.
    42:9–11; see also
    id. at 44:5–11.
    So, we are told, when the
    EPA said “one or more” in its decision, it actually meant more
    than one but maybe not all.
    Id. at 44:10–12.
    We are at a loss. Nowhere does the decision explain which
    of these four analyses are necessary or sufficient. Instead, the
    EPA faulted New York for failing to provide “this or any such
    similar analyses[.]” 84 Fed. Reg. at 56,089. But the decision
    never explains what “this” analysis is or why the Petition did
    not meet it. Nor did it shed light on what “similar analysis”
    would suffice. The EPA’s decision just left the court and future
    Section 126(b) petitioners to guess at the agency’s meaning.
    The reasoned agency decisionmaking that the Clean Air Act
    demands, 42 U.S.C. § 7607(d)(1)(N), (d)(9), does not allow the
    EPA to keep moving the finish line.
    Second, the EPA’s decision sent contradictory messages
    about whether, or to what extent, New York had to produce a
    global comparative analysis of potential emission reductions at
    listed and unnamed sources within each of the nine States.
    The EPA lists “describing the downwind air quality
    impacts of controlling the named sources relative to other
    sources” as one of the four analyses that would have allowed
    New York to meet its burden of proof. 84 Fed. Reg. at 56,089
    (emphasis added). The EPA then explained that it “cannot
    determine whether it would be appropriate to regulate any of
    the hundreds of” named sources unless those sources are first
    “compared to one another or * * * compared to other, unnamed
    16
    sources in the same upwind states or in other states.”
    Id. at 56,090.
    This suggests that a comprehensive comparative
    analysis of all sources—named and unnamed—within each
    designated State is strictly required.
    In response to commenters’ concerns that such a universal
    source comparison requirement was unworkable, the EPA
    stated that such “[a]pportioning” of “responsibility for
    emissions reductions across many sources in many states is a
    key outcome of applying the four-step interstate transport
    framework * * * under step 3[.]” 84 Fed. Reg. at 56,089–
    56,090 (emphasis added). The EPA then elaborated that the
    critical “source comparison necessarily involves” the
    petitioning State
    identifying the current operating status of each named
    facility, the magnitude of emissions from each
    emitting unit within each named facility, the existing
    controls on each of these emissions units, additional
    control options on each emissions unit, the cost of
    each potential control option, the emissions
    reductions potential resulting from the installation of
    controls, and potential air quality impacts of
    emissions reductions.
    Id.
    at 56,090.
    The EPA concluded that, without such detailed
    comparative information about individual sources’
    technological and operational capabilities, the agency “cannot
    determine whether the sources named in the [Petition] have
    available or cost-effective emissions reductions either as
    compared to one another or as compared to other, unnamed
    sources in the same upwind states or in other states.” 84 Fed.
    Reg. at 56,090 (emphasis added). Without that broad swath of
    comparative data, the decision said, the “EPA cannot determine
    17
    whether it would be appropriate to regulate any” of the sources
    identified in New York’s Petition.
    Id. But, despite
    comments flagging the concern, 84 Fed. Reg.
    at 56,089, the EPA left entirely unexplained how States are
    supposed to obtain the required detailed and technically
    particularized internal information from some unknown
    number of unnamed and unidentified sources. On top of the
    crushing breadth of the demand for information from unnamed
    sources across each State, the EPA directed that the analysis
    must “necessarily” identify each individual source’s
    “magnitude of emissions from each emitting unit within each
    named facility,” as well as “the existing controls [and]
    additional control options” for each unit, and “the emissions
    reductions potential resulting from the installation of controls”
    on each unit.
    Id. at 56,090.
    Those analyses—especially determining the emission
    reductions that would result from installing a particular control
    technology on each emitting unit—would require detailed and
    intricate inside knowledge of each facility’s equipment and
    operations. Such information is frequently not publicly
    available, especially for non-EGUs. See Oral Arg. Tr. 34:13–
    17, 59:5–9. Nor did the EPA explain why sources charged with
    polluting would hand such information out at the asking.
    At oral argument, the EPA backed away from the plain
    language of its decision, insisting that “[i]t is not EPA’s
    position that a petitioning state would have to do a comparative
    analysis.”     Oral Arg. Tr. 46:6–8.7         Rather, the EPA
    7
    But see 84 Fed. Reg. at 56,088–56,089 (EPA directing New
    York to conduct “one or more” of four possible analyses, including
    “describing the downwind air quality impacts of controlling the
    named sources relative to other sources[,]” and analyzing “the
    relative cost of the available emissions reductions and whether they
    18
    characterized such a comparative analysis as simply “one way”
    for a petitioning State to show cost-effectiveness.
    Id. at 46:13.
    The EPA also insisted that the statement in its decision that
    States can demonstrate cost-effectiveness by “describing the
    downwind air quality impacts of controlling the named sources
    relative to other sources[,]” 84 Fed. Reg. at 56,089 (emphasis
    added), did not suggest a comparative analysis. See Oral Arg.
    Tr. 46:14–23.
    This is all quite mystifying. If New York did not have to
    undertake the comparative analysis flagged in two of the four
    proposed analyses and discussed over two pages of the Federal
    Register, and if the EPA cannot definitively say whether New
    York has satisfied “one or more” of the preferred analyses, 84
    Fed. Reg. at 56,088, then we are left with no coherent
    explanation of what was missing from New York’s Petition.
    The required analysis seems to be a constantly moving target,
    with the words of explanation from the agency variously
    meaning and not meaning what they say.
    At bottom, the EPA’s Delphic explanation of New York’s
    purported failure to carry its burden of proof—and of even
    what that burden is—falls far short of reasoned
    decisionmaking. See Environmental Defense Fund v. EPA,
    
    922 F.3d 446
    , 454 (D.C. Cir. 2019) (“An agency acts arbitrarily
    are less expensive than other reductions from other sources”)
    (emphasis added);
    id. at 56,090
    (EPA stating that New York has
    provided insufficient information to allow it to “determine whether
    the sources named in the New York [P]etition have available or cost-
    effective emissions reductions either as compared to one another or
    as compared to other, unnamed sources in the same upwind states or
    in other states”) (emphasis added).
    19
    and capriciously when it offers * * * unreasoned justifications
    for a decision.”).
    Third, in addition to dismissing New York’s cost-
    effectiveness analysis as insufficient to support a Step 3
    finding, the decision claims “that the emissions reductions
    required under the * * * [2008] Update [Rule] fully address the
    good neighbor requirements with respect to the 2008 ozone
    NAAQS for all the States named in the [P]etition.” 84 Fed.
    Reg. at 56,089. The EPA added that the electric generating unit
    control technologies identified by New York and by certain
    commenters had already been accounted for in the 2008 Update
    Rule’s trading scheme.
    Id. at 56,092.
    The EPA has abandoned the first contention—that the
    2008 Update Rule fully satisfies the Good Neighbor
    requirements under the 2008 NAAQS. And for good reason.
    This court has held that the 2008 Update Rule did not satisfy
    any States’ Good Neighbor obligations. See New York v. EPA,
    781 F. App’x 4, 6–7 (D.C. Cir. 2019) (vacating the EPA’s
    Determination Regarding Good Neighbor Obligations for the
    2008 Ozone National Ambient Air Quality Standard, 83 Fed.
    Reg. 65,878 (Dec. 21, 2018)); see also 
    Wisconsin, 938 F.3d at 309
    , 313–318 (holding that the 2008 Update Rule violated the
    Clean Air Act by allowing upwind States to continue
    contributing to downwind air quality problems “beyond the
    statutory deadlines by which downwind States must
    demonstrate their attainment”).
    But the EPA continues to press its second rationale—that
    the 2008 Update Rule’s emissions trading scheme fully
    addressed any Good Neighbor Provision obligations associated
    with electric generating units. To be sure, this court’s decision
    in Wisconsin upheld the reasonableness of the Update’s cap-
    20
    and-trade scheme and its specific emissions budgets.
    
    Wisconsin, 938 F.3d at 329
    –335.
    But the EPA is incorrect to argue that Wisconsin also held
    that the 2008 Update Rule comprehensively addressed all Good
    Neighbor Provision obligations associated with electric
    generating units. To the contrary, Wisconsin described the
    2008 Update Rule as only a “first, partial step to addressing a
    given upwind State’s significant 
    contribution.” 938 F.3d at 313
    (quoting 2008 Update Rule, 81 Fed. Reg. 74,522). Indeed, the
    EPA itself announced that full resolution of the Good Neighbor
    Provision obligations would require consideration of “further
    EGU reductions[.]”
    Id. (quoting 2008
    Update Rule, 81 Fed.
    Reg. at 74,522); see also 2008 Update Rule, 81 Fed. Reg. at
    74,521 (“To evaluate full elimination of a state’s significant
    contribution to nonattainment or interference with
    maintenance, * * * further EGU reductions that are achievable
    after 2017 should be considered.”). So the 2008 Update Rule
    does nothing to salvage the EPA’s Step 3 rejection of New
    York’s Petition.
    Finally, the Industry Intervenors urge this court to override
    the EPA’s finding that the New York Metropolitan Area is
    likely to face compliance issues in 2023 with respect to the
    2015 NAAQS, and to uphold the EPA’s denial of the Petition,
    at least in part, based on this alternative ground. Industry
    Intervenors Br. 36–39. The Industry Intervenors also argue
    that the court should uphold the EPA’s decision on the alternate
    ground that the sources listed in the Petition do not qualify as a
    “group” under Section 126. Industry Intervenors Br. 7–17.
    Because the agency did not rest its decision on either of those
    bases, we reject both arguments. See USPS v. NLRB, 
    969 F.2d 1064
    , 1069 (D.C. Cir. 1992) (“[W]e reject [the intervenor’s]
    endeavor to achieve disposition of this case on a rationale [not]
    set forth by the agency itself.”) (internal quotation marks
    21
    omitted); see also SEC v. Chenery Corp., 
    318 U.S. 80
    , 93–95
    (1943).
    B
    The EPA’s denial of the Petition at Step 1 with respect to
    the 2008 NAAQS is equally unsustainable. Recall that Step 1
    involves identifying downwind areas that have trouble
    attaining or maintaining the NAAQS. 84 Fed. Reg. at 56,062.
    The EPA found that the Petition failed to demonstrate that the
    New York Metropolitan Area had an air quality problem under
    the 2008 NAAQS. 84 Fed. Reg. at 56,080–56,081.
    That decision was legally flawed in two ways.
    For starters, the EPA’s decision erroneously treated 2023
    as the relevant Step 1 reference year for the 2008 NAAQS,
    even though the New York Metropolitan Area is subject to a
    2021 nonattainment deadline. 84 Fed. Reg. at 56,080. This
    court rejected that very proposition in Wisconsin, holding that
    the 2008 Update Rule violated the Clean Air Act by allowing
    “upwind States to continue their significant contributions to
    downwind air quality problems beyond the statutory deadlines
    by which downwind States must demonstrate their
    
    attainment[.]” 938 F.3d at 309
    ; see also
    id. at 315–316
    (The
    Clean Air Act “cannot reasonably be understood to enable
    upwind States to continue their significant contributions
    outside of the statutory timeframe by which downwind areas
    must achieve attainment, much less continue those
    contributions with no deadline at all.”). This means that the
    agency “must evaluate downwind air quality at [the downwind
    States’ statutory] deadline”—here, 2021—and “not at some
    later date[,]” like 2023, as the EPA did in this case. Maryland,
    slip op. at 33.
    22
    The second problem with the EPA’s analysis of the 2008
    NAAQS portion of New York’s Petition is that it unreasonably
    “interpreted * * * [S]ection 126(b)’s petition authority as
    limited to states * * * seeking to address interstate transport of
    pollution impacting downwind receptors within their
    geographical borders.” 84 Fed. Reg. at 56,080 (emphasis
    added); see also
    id. at 56,081
    & n.70.
    Our recent decision in Maryland firmly closed the door on
    that proposition, “at least” with respect to monitors like New
    York’s that are “located in a multistate nonattainment area that
    includes the petitioning state.” Maryland, slip op. at 27–28
    (internal quotation marks omitted). To hold otherwise would
    have created an untenable incongruity in the statute—placing
    States “in regulatory limbo” where they are subject to
    regulatory burdens based on their air quality control region’s
    nonattainment, “yet unable to avail [themselves] of the
    intended remedy for addressing upwind contributions” to that
    nonattainment.
    Id. at 26.
    IV
    For the foregoing reasons, we grant the petition for review,
    vacate the EPA’s denial of the Petition, and remand the case
    for further proceedings consistent with this opinion.
    New York asks that we include a 60-day deadline for the
    EPA to issue a new decision. See 42 U.S.C. § 7426(b)
    (imposing a 60-day deadline for the EPA to act on
    Section 126(b) petitions); Natural Res. Defense Council, Inc.
    v. Train, 
    510 F.2d 692
    , 705 (D.C. Cir. 1974) (“The authority to
    set enforceable deadlines both of an ultimate and an
    intermediate nature is an appropriate procedure for exercise of
    the court’s equity powers to vindicate the public interest.”).
    23
    Although we decline to impose a formal deadline at this
    time, we fully expect the EPA to act promptly on remand.
    So ordered.
    GRIFFITH, Circuit Judge, concurring: I write separately to
    discuss the proper role of section 126 of the Clean Air Act.
    Comprehensive remedies for interstate ozone transfer must be
    implemented through state implementation plans (SIPs)—or, if
    necessary, federal plans—that satisfy the Good Neighbor
    provision. By contrast, section 126 is designed for targeted
    regulation. New York’s petition, which covers 350 diverse
    sources across nine states, is inconsistent with that design.
    Start with the text. Section 126 empowers downwind
    jurisdictions to request EPA regulation of “any major source or
    group of stationary sources” that causes air-quality problems
    under the Good Neighbor provision. 42 U.S.C. § 7426(b). In its
    original form, section 126 limited petitioners to a single “major
    source.” Pub. L. No. 95-95, § 123(b), 91 Stat. 685, 685 (1977).
    Congress added the “group of stationary sources” language
    more than a decade later. Clean Air Act Amendments, Pub. L.
    No. 101-549, § 109(a)(1)(A), 104 Stat. 2399, 2469 (1990).
    That change “plainly reflected a decision to act against
    sources whose emissions, while harmless individually, could
    become harmful when combined with others.” Appalachian
    Power Co. v. EPA, 
    249 F.3d 1032
    , 1049 (D.C. Cir. 2001). But
    it did not convert section 126 from a rifle to a blunderbuss. The
    contrast with the Good Neighbor provision, which applies to
    “any source or other type of emissions activity,” remains stark.
    42 U.S.C. § 7410(a)(2)(D)(i); cf. Appalachian 
    Power, 249 F.3d at 1049
    (contrasting the Good Neighbor provision’s “broad”
    language, which enabled “findings based on aggregate
    emissions from within each regulated state,” with section 126,
    which “demands that the significant contribution come from a
    ‘major source or group of stationary sources’”). Had Congress
    wished to harmonize the scope of these provisions, it could
    have standardized their text. It did not.
    Nor did Congress simply append a plural—“or sources”—
    to “any major source.” Instead, it provided that the “stationary
    2
    sources” must constitute a “group.” That choice indicates that
    the provision’s intended remedial scope is limited, not
    comprehensive. We give an “undefined term its ordinary
    meaning,” United States v. Williams, 
    836 F.3d 1
    , 8 (D.C. Cir.
    2016), and dictionaries confirm what common sense suggests:
    a “group” is a collection of items that share a common attribute.
    Group, WEBSTER’S NEW INTERNATIONAL DICTIONARY 1004
    (3d ed. 1981) (defining “group” as “an assemblage of objects
    regarded as a unit because of their comparative segregation
    from others”); see also Oxford English Dictionary Online,
    www.oed.com/view/Entry/81855 (3d ed. 2014) (“[a] number
    of things having some related properties or attributes in
    common, regarded as forming a unity or classified together
    under a general name or description”).
    As we observed in Appalachian Power, this “statutory
    language allows the EPA to regulate facilities in upwind states
    as a class or category, e.g. all coal-fired power plants in North
    
    Carolina.” 249 F.3d at 1057
    (emphasis added). Petitioners and
    EPA presumably enjoy wide latitude when identifying such
    commonalities, and we don’t need to set boundaries today. The
    crucial point for present purposes is that “group of stationary
    sources” describes a set of sources with some unifying
    characteristic; it is not merely the plural form of “stationary
    source.”
    New York’s petition, which seeks EPA regulation of 350
    disparate sources across the Midwest and mid-Atlantic regions,
    falls short by any measure. In addition to 130 power plants, the
    petition covers oil refineries, natural-gas compressor stations,
    chemical plants, steel and paper mills, waste incinerators, and
    factories that produce goods ranging from glass to ammunition.
    J.A. 90-99. These sources are not united by geography (they
    range from Illinois to Maryland), plant technology, industry
    3
    sector, or any other “class or category.” Appalachian 
    Power, 249 F.3d at 1057
    .
    The only feature shared by the sources in New York’s
    petition is that each emits more than 400 tons of nitrogen
    oxides per year. See NYSDEC Detailed Comments at 10, J.A.
    495. That arbitrary threshold captures both an Indiana power
    plant emitting more than 10,000 tons annually and a Virginia
    bottle factory emitting just 412 tons. J.A. 90, 97. If that’s
    enough to establish a “group,” the term is all but meaningless.
    At oral argument, Petitioners claimed to “stick to a group in the
    sense that we are talking just about interstate ozone transport
    here, and we are trying to identify all the sources that contribute
    to our problem.” Oral Arg. Tr. 11:3-6. In other words,
    Petitioners think a petition is sufficiently limited if it targets a
    single air pollutant and lists sources that allegedly transgress
    the Good Neighbor provision. But that reading equates the duty
    to identify a “group of . . . sources” with the substantive
    inquiry—effectively erasing the word “group” from the statute.
    Moving from text to context, the Act’s tight deadlines and
    harsh remedial scheme confirm that section 126 isn’t designed
    to solve comprehensive regional problems. “Congress
    specified that the Administrator take final action on a section
    126(b) petition very quickly.” New York v. EPA, 
    852 F.2d 574
    ,
    578 (D.C. Cir. 1988). EPA must make the requested finding or
    issue a denial “[w]ithin 60 days after receipt of any petition . . .
    and after public hearing,” 42 U.S.C. § 7426(b), subject to an
    optional six-month extension,
    id. § 7607(d)(10).
    In an earlier
    case, we found it “reasonable to conclude” that EPA need not
    perform the wide-ranging tasks associated with reevaluating
    SIPs “in such a short period of time.” New 
    York, 852 F.2d at 578
    . By the same token, EPA cannot be expected to craft a
    definitive solution to a downwind state’s ozone problems
    within the timeframe provided by section 126.
    4
    Compare that quick turnaround to the timelines for SIP
    development under section 110. That process affords three
    years for states to craft implementation plans, two months for
    EPA’s initial “completeness” evaluation, one year for EPA’s
    full substantive evaluation, and two years for revisions before
    EPA must impose a federal plan. 42 U.S.C. § 7410(a), (c)(1),
    (k)(1)-(5). Keep in mind that “the substantive inquiry for
    decision is the same in both [section 110 and section 126]
    proceedings.” Appalachian 
    Power, 249 F.3d at 1047
    (internal
    quotation marks omitted). If Congress expected EPA to
    conduct the same “substantive inquiry” along such divergent
    timelines, then it cannot have intended the scope of the two
    inquiries to be the same.
    Next, consider the drastic repercussions of a finding under
    section 126(b) that a source “emits or would emit in violation”
    of the Good Neighbor provision. 42 U.S.C. § 7426(b).
    Petitioners acknowledged at oral argument that section 126, “in
    contrast to [section] 110, allows for a . . . more expedited
    schedule for compliance.” Oral Arg. Tr. 7:17-19. That’s an
    understatement. If EPA makes an affirmative finding, the
    offending plant has three months to comply or cease
    operations. 42 U.S.C. § 7426(c)(2). Operating beyond that
    period is “a violation of this section,”
    id. § 7426(c),
    and
    exposes the source to civil penalties,
    id. § 7413(d).
    This swift,
    severe, and purely federal intervention is a poor fit for regional
    relief and stands in sharp contrast to section 110’s cooperative
    approach.
    EPA “may permit the continued operation of a source”
    beyond three months, but only if the source “complies with
    such emission limitations and compliance schedules” as EPA
    may provide.
    Id. § 7426(c).
    But when EPA confronts a petition
    seeking regulation of hundreds of diverse sources, that task is
    an onerous one for both the regulator and the regulated.
    5
    Consider the petition here. A finding that these sources emit in
    violation of the Good Neighbor provision would open a three-
    month window for EPA to develop source-specific regulations
    for the large power plant in Indiana, the bottle manufacturer in
    Virginia, and everything in between. Beyond that three-month
    period, each source would face the prospect of shutting down
    or risking administrative penalties. Again, these aspects of the
    statutory scheme strongly suggest that section 126 authorizes
    targeted intervention.
    Section 126 and the Good Neighbor provision differ in
    another important respect. The latter obliges a state to regulate
    its own sources to prevent harmful interstate transport. See 42
    U.S.C. § 7410(a)(2)(D)(i) (“any source or other type of
    emissions activity within the State”). EPA steps in only when
    state-led efforts fail. See
    id. § 7410(c)(1).
    But section 126
    allows a downwind state to request direct federal regulation of
    sources beyond its borders. See
    id. § 7426(b)
    (“any major
    source or group of stationary sources”). Construed too broadly,
    section 126 would make downwind states (with EPA’s help)
    the primary regulators of their upwind neighbors. That is
    inconsistent with the Clean Air Act’s ethos of cooperative
    federalism. I don’t mean to suggest that a state must wait for
    the SIP process to conclude before filing a petition. See
    Appalachian 
    Power, 249 F.3d at 1045
    , 1048 (holding that EPA
    may “mak[e] [section] 126 findings” and conduct the section
    110 process simultaneously because the provisions “operate
    independently”). But in the ordinary course, comprehensive
    regulation of a state’s polluters should be controlled by the state
    itself, not a neighboring government.
    In sum, the textual and contextual evidence convinces me
    that section 126 was not designed for petitions of this breadth.
    Nor is it simply an alternative route by which a downwind state
    can trigger the massive regulatory undertaking associated with
    6
    SIP development under section 110. And I’m not alone in this
    assessment: Petitioners call section 126 “a source-specific
    tool” for securing “tailored remedies . . . narrower than the
    seasonal average ozone budgets established by EPA’s regional
    rulemakings under” section 110. Pet’r Br. 57. Quite right. I
    likewise agree that “Congress plainly intended for section 126
    to provide . . . targeted relief independent of more
    comprehensive rulemaking.”
    Id. But a
    jurisdiction that invokes this “tailored,” “source-
    specific” provision,
    id., should in
    fact tailor its petition to
    specific sources—something New York did not even try to do.
    Two states took a more appropriate approach in a recent section
    126 case decided in our court. See Maryland v. EPA, No. 18-
    1285, slip op. at 12-13 (D.C. Cir. May 19, 2020). Maryland’s
    petition identified thirty-six sources, all power plants;
    Delaware filed four separate petitions, each targeting a single
    source.
    Id. Future petitioners
    should follow those examples,
    which are more consistent with the text and structure of section
    126.
    The opinion for the court properly declines to address
    these matters because EPA did not rely on them in its denial of
    New York’s petition. But in a future case, EPA may decide to
    enforce the textual and structural restrictions on the scope of a
    section 126 petition. Prospective petitioners should act
    accordingly.