Nat Resrc Def Cncl v. EPA ( 2009 )


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  •  United States Court of Appeals
    FOR THE DISTRICT OF COLUMBIA CIRCUIT
    Argued November 20, 2008                 Decided July 10, 2009
    No. 06-1045
    NATURAL RESOURCES DEFENSE COUNCIL,
    PETITIONER
    v.
    ENVIRONMENTAL PROTECTION AGENCY,
    RESPONDENT
    NATIONAL PETROCHEMICAL & REFINERS ASSOCIATION, ET
    AL.,
    INTERVENORS
    Consolidated with 06-1046, 06-1047, 06-1214, 07-1311
    On Petitions for Review of an Order
    of the Environmental Protection Agency
    David S. Baron argued the cause and filed the briefs for
    petitioner Natural Resources Defense Council.
    Anne Milgram, Attorney General, Attorney General’s
    Office of the State of New Jersey, and Maurice A. Griffin,
    Deputy Attorney General, were on the briefs for petitioner State
    of New Jersey.
    2
    Kevin P. Auerbacher, Assistant Attorney General, entered an
    appearance.
    Frank S. Craig III, John B. King, Steven J. Levine, and
    Patrick O'Hara were on the briefs for petitioners The Chamber
    of Greater Baton Rouge, et al. Geraldine E. Edens entered an
    appearance.
    Andrew Cuomo, Attorney General, Attorney General’s
    Office of the State of New York, Morgan A. Costello and
    Michael J. Myers, Assistant Attorneys General, Richard
    Blumenthal, Attorney General, Attorney General's Office of the
    State of Connecticut, and Kimberly P. Massicotte, Assistant
    Attorney General, were on the briefs for intervenors the States
    of New York and Connecticut in support of petitioner.
    Charles H. Knauss and Sandra P. Franco were on the briefs
    for intervenor National Petrochemical & Refiners Association
    in support of petitioner Natural Resources Defense Council.
    Brian H. Lynk, Attorney, U.S. Department of Justice,
    argued the cause for respondents. With him on the brief were
    John C. Cruden, Deputy Assistant Attorney General, and Diane
    E. McConkey, Counsel, U.S. Environmental Protection Agency.
    Norman W. Fichthorn and Lucinda M. Langworthy were on
    the brief for intervenor Utility Air Regulatory Group in support
    of respondents. Allison D. Wood entered an appearance.
    Charles H. Knauss was on the brief for intervenors National
    Petrochemical & Refiners Association and American Petroleum
    Institute in support of respondents. Martha E. Cox and Stacy R.
    Linden entered appearances.
    3
    Before: GINSBURG, HENDERSON and ROGERS, Circuit
    Judges.
    Opinion for the Court filed PER CURIAM.
    Opinion concurring in part and dissenting in part filed by
    Circuit Judge ROGERS.
    PER CURIAM: In 1997, the EPA revised the National
    Ambient Air Quality Standard (NAAQS) for ozone from a
    1-hour standard to an 8-hour standard. These consolidated
    petitions for review challenge aspects of the Final Rule To
    Implement the 8-Hour Ozone National Ambient Air Quality
    Standard — Phase 2, 
    70 Fed. Reg. 71,612
     (2005) (Phase 2
    Rule), and Phase 2 of the Final Rule To Implement the 8-Hour
    Ozone National Ambient Air Quality Standard — Notice of
    Reconsideration, 
    72 Fed. Reg. 31,727
     (2007) (Reconsideration
    Notice). We hold the Phase 2 Rule is inconsistent with the
    Clean Air Act (CAA or Act) in allowing participation in a
    regional cap-and-trade program to satisfy an area-specific
    statutory mandate. We further hold the EPA arbitrarily
    eliminated one safeguard and violated the anti-backsliding
    provision of the Act insofar as it eliminated another from its
    regulations governing review of new sources of pollution. We
    therefore grant the petitions with respect to those aspects of the
    Phase 2 Rule. In view of our decision in North Carolina v. EPA,
    
    531 F.3d 896
     (2008), in which we granted a petition for review
    of the Clean Air Interstate Rule (CAIR), we defer consideration
    of the Phase 2 Rule and Reconsideration Notice insofar as they
    relate to the CAIR program. We deny the petitions in all other
    respects.
    I. Background
    4
    The Act requires the EPA to designate areas as attainment,
    nonattainment, or unclassifiable for each NAAQS. CAA §
    107(d)(1)(B), 
    42 U.S.C. § 7407
    (d)(1)(B). States have primary
    responsibility for implementing those standards, and must
    submit a state implementation plan (SIP) that specifies how the
    state will achieve and maintain compliance with the NAAQS.
    
    Id.
     § 7407(a). Part D of the Act provides the SIP for a
    nonattainment area must include certain control measures. Id.
    § 7501 et seq. Subpart 1 applies to all nonattainment areas, id.
    §§ 7501-7509a, whereas Subpart 2 specifies additional
    requirements for ozone nonattainment areas, id. §§ 7511-7511f.
    Section 181 of the Act classifies ozone nonattainment areas
    from “marginal” to “extreme” based upon the degree to which
    the ozone level in the area exceeds the NAAQS. Id. § 7511. An
    area that exceeds the NAAQS by a greater margin is given more
    time to meet the standard but is subjected to progressively more
    stringent emissions controls for ozone precursors, namely,
    volatile organic compounds (VOCs) and oxides of nitrogen
    (NOX). See CAA § 182, 42 U.S.C. § 7511a.
    In 1997, the EPA determined the NAAQS for ozone,
    expressed as the amount of ozone in the ambient air averaged
    over one hour, was inadequate to protect public health. The
    EPA therefore promulgated a new NAAQS of .08 ppm of ozone
    averaged over eight hours. Under the 8-hour standard, some
    ozone nonattainment areas are subject only to the more flexible
    requirements of Subpart 1, while areas with higher levels of
    ozone are subject to the additional requirements of Subpart 2.
    See S. Coast Air Quality Mgmt. Dist. v. EPA, 
    472 F.3d 882
    ,
    893-95 (D.C. Cir. 2006).
    The EPA implemented the 8-hour NAAQS in two phases;
    the Phase 2 Rule and Reconsideration Notice here under review
    implement the requirements of Subpart 1 and Subpart 2 for areas
    not attaining the 8-hour NAAQS. The consolidated petitions
    5
    challenge those rules as follows. The Natural Resources
    Defense Council, the States of New Jersey, Connecticut, and
    New York, and the National Petrochemical and Refiners
    Association challenge provisions implementing the statutory
    requirement that each nonattainment area provide for such
    emissions reductions as may be obtained by the adoption of
    reasonably available control technology (RACT). The NRDC
    and New Jersey challenge provisions governing review of new
    sources of pollution. The NRDC also challenges two provisions
    implementing the statutory requirements that a SIP for a
    nonattainment area provide for specific percentage reductions in
    emissions and for contingency measures. Finally, the Chamber
    of Greater Baton Rouge and affiliated petitioners1 challenge the
    imposition of reformulated gasoline requirements in the Baton
    Rouge area.
    We review the EPA’s interpretation of the Act pursuant to
    Chevron U.S.A. Inc. v. Natural Res. Def. Council, Inc., 
    467 U.S. 837
     (1984): We ask first whether the 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,” then we defer to
    the EPA’s interpretation as long as it is “based on a permissible
    construction of the statute.” 
    Id.
     The Act requires us to review
    the Phase 2 Rule deferentially to determine only whether it is
    “arbitrary, capricious, an abuse of discretion, or otherwise not in
    accordance with law.” CAA § 307(d)(9)(A), 
    42 U.S.C. § 7607
    (d)(9)(A); see Bluewater Network v. EPA, 
    372 F.3d 404
    ,
    410 (D.C. Cir. 2004) (“We give particular deference to the EPA
    when it acts under unwieldy and science-driven statutory
    1
    The affiliated petitioners are the West Baton Rouge Chamber of
    Commerce, the Iberville Parish Chamber of Commerce, and the
    Louisiana Oil Marketers and Convenience Store Association.
    6
    schemes like the Clean Air Act”) (internal quotation marks
    omitted).
    II. Reasonably Available Control Technology
    Section 172(c)(1) of the Act requires that the SIPs for
    nonattainment areas “provide for the implementation of all
    reasonably available control measures as expeditiously as
    practicable (including such reductions in emissions from
    existing sources in the area as may be obtained through the
    adoption, at a minimum, of reasonably available control
    technology).” 
    42 U.S.C. § 7502
    (c)(1) (emphasis added). Ozone
    nonattainment areas that are subject to Subpart 2 of Part D are
    subject to more specific reasonably available control technology
    requirements. E.g., 
    id.
     § 7511a(b)(2)(C); id. § 7511a(f).
    Petitioners challenge three aspects of the implementation of the
    RACT requirement in the Phase 2 Rule. First, the NRDC
    challenges the rule providing that RACT is satisfied for Subpart
    1 areas by SIPs “demonstrating that the area has adopted all
    control measures necessary to demonstrate attainment as
    expeditiously as possible,” Phase 2 Rule, 70 Fed. Reg. at 71,701
    (codified at 
    40 C.F.R. § 51.912
    (c)(1)). Second, the State of New
    Jersey challenges the EPA’s decision to allow states to meet the
    RACT requirement under the 8-hour NAAQS by certifying that
    RACT is met under the 1-hour NAAQS, see 
    id. at 71,652-53
    .
    Third, the NRDC, New Jersey, the States of Connecticut and
    New York, and the National Petrochemical and Refiners
    Association challenge the EPA’s conclusion that states may
    satisfy the RACT requirement by participating in two
    cap-and-trade programs, the NOX SIP Call and CAIR, see 
    id.
    The court has stayed consideration of the CAIR-RACT
    determination.2
    2
    The second and third challenges are to the EPA’s statements in
    the preamble to the final rule. The statements constitute reviewable
    7
    A. RACT in Subpart 1 Nonattainment Areas
    The NRDC challenges the Phase 2 Rule’s treatment of the
    “reasonably available control technology” requirement of CAA
    § 172(c)(1), 
    42 U.S.C. § 7502
    (c)(1). Under the Phase 2 Rule,
    nonattainment areas governed by Subpart 1 that request an
    attainment deadline within five years of their designation “shall
    meet the RACT requirement by submitting an attainment
    demonstration SIP demonstrating that the area has adopted all
    control measures necessary to demonstrate attainment as
    expeditiously as practicable.” Phase 2 Rule, 70 Fed. Reg. at
    71,701/3 (codified at 
    40 C.F.R. § 51.912
    (c)(1)). The NRDC
    contends that this provision is an unlawful waiver of the RACT
    requirement of § 172(c)(1) because, under the Phase 2 Rule, a
    state need not require RACT at all in such areas. It views the
    statutory phrase “at a minimum” as imposing an unambiguous
    requirement for all nonattainment areas. The NRDC thus
    contends the Phase 2 Rule violates the plain text of § 172(c)(1)
    by doing away with this requirement in some nonattainment
    areas. However, we conclude that the term “reasonably
    available control technology” is ambiguous in context and that
    the EPA’s interpretation is reasonable.
    The court has previously concluded that the term
    “reasonably available” in the analogous phrase “reasonably
    final agency action, see CAA § 307(b)(1), 
    42 U.S.C. § 7607
    (b)(1), as
    they represent “the consummation of the agency’s decisionmaking
    process and . . . establish[] rights and obligations or create[] binding
    legal consequences.” Natural Res. Def. Council v. EPA, 
    559 F.3d 561
    ,
    564 (D.C. Cir. 2009). The EPA’s statements as to how it will
    implement the RACT requirement are not conjectural and their terms
    are clear, so it is fair to infer that the EPA intended the statements to
    create binding legal consequences. See Kennecott Utah Copper Corp.
    v. Dep’t of Interior, 
    88 F.3d 1191
    , 1222-23 (D.C. Cir. 1996).
    8
    available control measure” (RACM) in § 172(c)(1) is ambiguous
    and “clearly bespeaks [the Congress’s] intention that the EPA
    exercise discretion in determining which control measures must
    be implemented . . . .” Sierra Club v. EPA, 
    294 F.3d 155
    , 162-
    63 (D.C. Cir. 2002). The court explained that the statute did not
    specify which control measures would be deemed “reasonably
    available” and did not “compel[] a state to consider whether any
    measure is ‘reasonably available’ without regard to whether it
    would expedite attainment in the relevant area.” 
    Id. at 162
    .
    Thus, the EPA had discretion to conclude that a measure was not
    “reasonably available” if it would not expedite attainment. 
    Id.
    Because the same is true of the phrase “reasonably available
    control technology,” the term “reasonably available” within
    RACT is also ambiguous. Moreover, even if the phrase “at a
    minimum” requires that at least RACT-level reductions be
    achieved in all nonattainment areas, the phrase does not specify
    the content of the RACT requirement. Given this ambiguity, the
    EPA has discretion reasonably to define the controls that will
    demonstrate compliance.
    The EPA’s interpretation, construing “reasonably available”
    as meaning only control technologies that advance attainment,
    is reasonable in light of the statute’s accompanying text and
    structure. Section 172(c)(1) requires all nonattainment areas to
    achieve RACM “as expeditiously as practicable (including such
    reductions . . . as may be obtained through the adoption, at a
    minimum, of reasonably available control technology) . . . .” 
    42 U.S.C. § 7502
    (c)(1). To the extent an area is already achieving
    attainment as expeditiously as possible, imposition of additional
    control technologies would not hasten achievement of the
    NAAQS. In such a situation, the EPA may reasonably conclude
    that no control technologies are reasonably available and the
    area need not implement further technologies to satisfy the
    RACT requirement. Sierra Club v. EPA, 
    294 F.3d 155
     (D.C.
    Cir. 2002), supports the reasonableness of the EPA’s
    9
    interpretation. In Sierra Club, the court held reasonable the
    EPA’s interpretation of RACM as requiring only those control
    measures that would contribute to timely and expeditious
    attainment. 
    294 F.3d at 162
    ; see also Sierra Club v. EPA, 
    314 F.3d 735
    , 743-45 (5th Cir. 2002). The court explained, in part,
    that the “Act ‘use[s] the same terminology in conjunction with
    the RACM requirement’ as it does in requiring timely
    attainment.” Sierra Club, 
    294 F.3d at 162
    . The § 172(c)(1)
    RACM requirement, like the timely attainment requirement of
    CAA § 181(a)(1), 
    42 U.S.C. § 7511
    (a)(1), requires
    implementation of RACM “as expeditiously as practicable.”
    Thus, the court concluded, the RACM requirement could
    reasonably be understood as a means of meeting the attainment
    deadline. 
    294 F.3d at 162
    . Because the RACT requirement is
    located in a parenthetical modifying RACM and because the
    RACM requirement is described as “including” the RACT
    requirement, the RACT requirement is likewise linked to the
    timely attainment terminology. Given this textual linkage, the
    EPA may reasonably extend to the RACT requirement its
    interpretation of RACM as requiring only those control
    measures that would facilitate expeditious attainment of the
    NAAQS.
    Contrary to the NRDC’s arguments, the RACT requirement
    does not lose all meaning under the EPA’s definition. When
    control technology is necessary to advance attainment, it is
    “reasonably available” under the definition and would be
    required under the rule. The fact that the RACT requirement
    was previously located in a separate section and not in a
    parenthetical modifying the RACM requirement does not
    support the NRDC’s position. Compare CAA § 172(b)(2), 
    42 U.S.C. § 7502
    (b)(2), (3) (1977), with CAA § 172(c)(1), 
    42 U.S.C. § 7502
    (c)(1) (1990). Rather, the fact that the Congress
    moved the requirement to a parenthetical modifying the RACM
    requirement supports the EPA’s conclusion that the RACT
    10
    requirement could be interpreted in the same manner as the
    RACM requirement. Although both the NRDC and the EPA
    point to legislative history purportedly supporting their
    positions, neither points to legislative history bearing on the
    meaning of “reasonably available.” See H.R. REP. NO. 101-490,
    reprinted in 2 LEGISLATIVE HISTORY OF THE CLEAN AIR ACT
    AMENDMENTS OF 1990, at 223. The term “reasonably available”
    is ambiguous, and the EPA’s interpretation is a permissible
    construction of the statute.
    B. Certifying 8-Hour RACT Based Upon 1-Hour RACT
    The Phase 2 Rule provides that a control measure approved
    as RACT under the 1-hour standard will be approved as RACT
    under the 8-hour standard absent information indicating it
    should not be approved. Phase 2 Rule, 70 Fed. Reg. at 71,652/3.
    Rather than reassessing what constitutes RACT, a state can
    certify that controls that previously satisfied the RACT
    requirement also satisfy the requirement under the 8-hour
    standard. New Jersey contends this provision is contrary to the
    Act and arbitrary and capricious. In New Jersey’s view the EPA
    should require a re-analysis for all sources, not just those for
    which no controls had been considered RACT under the 1-hour
    standard, see id. at 71,655, because what is “reasonably
    available” changes over time. Without a re-analysis, New
    Jersey maintains there is no basis for states to certify that the
    initial RACT analysis meets the RACT requirement under the 8-
    hour NAAQS and states may apply outdated RACT controls.
    New Jersey thus claims that the EPA should have either updated
    its RACT guidance documents or at least provided uniform
    criteria for states to use in making RACT certifications.
    The EPA promulgates two types of guidance that assist
    states in determining what control techniques meet the RACT
    requirement, control techniques guidelines (CTGs) and
    11
    alternative control techniques (ACTs). Section 183 of the Act
    requires the EPA to issue CTGs for certain categories of sources
    that emit VOCs. See 42 U.S.C. § 7511b. Where CTGs exist,
    they establish the presumptive level of control meeting RACT.
    Phase 2 Rule, 70 Fed. Reg. at 71,654/3. Still, states can opt to
    require alternative controls rather than following the guidance
    in the CTGs. Notice of Final Determination and Availability of
    Final Control Techniques Guidelines, 
    71 Fed. Reg. 58,745
    ,
    58,747 (Oct. 5, 2006). Section 183(c) of the Act requires the
    EPA to issue ACTs for major sources of VOCs and NOX. 42
    U.S.C. § 7511b(c). The ACTs “describe available control
    techniques and their cost effectiveness” but do not establish
    presumptive RACT. Phase 2 Rule, 70 Fed. Reg. at 71,654/3.
    Thus, neither the CTGs nor ACTs set firm RACT requirements.
    Despite New Jersey’s concerns, the EPA’s certification
    provision does not conflict with the Act and is not arbitrary and
    capricious. Although the EPA did not revise the guidance
    documents, the EPA’s case-by-case approach adequately
    ensures that RACT determinations will take into account
    advances in technology. First, the EPA has directed states to
    consider available information in addition to the CTG and ACT
    documents when making RACT determinations. Id. at
    71,655/1. If a state is presented with information indicating that
    a previous RACT determination is inappropriate, the state must
    consider that information and modify its RACT determinations
    accordingly. Id. Second, when submitting RACT certifications
    to the EPA as part of their RACT SIP submissions, states must
    provide supporting information. Id. at 71,655/2. Third, if
    additional information is presented during notice-and-comment
    rulemaking, both the state and the EPA are required to consider
    that information as part of the rulemaking; this includes
    information presented during notice-and-comment rulemaking
    for RACT SIP submissions for previously controlled sources.
    Id. Because the EPA could reasonably conclude that these
    12
    mechanisms will ensure the case-by-case determinations will
    take into account advances in technology, the EPA could also
    reasonably conclude “that the best way to address the possibility
    that CTGs or ACTs might not reflect all currently available
    technologies was by requiring each State to consider any new
    available information in making its certification, which will then
    be reviewed by the EPA as part of the SIP submission process,”
    EPA Br. at 67; see also Phase 2 Rule, 70 Fed. Reg. at 71,655/1.
    See Nat’l Wildlife Fed’n v. EPA, 
    286 F.3d 554
    , 566-67 (D.C.
    Cir. 2002). Likewise, given the assurances that RACT
    determinations will reflect advances in technology, the EPA’s
    approach is consistent with the statutory goal of timely
    attainment of the NAAQS, see CAA §§ 172, 182, 
    42 U.S.C. §§ 7502
    , 7511a.
    Additionally, even if the EPA had revised the national
    guidelines and provided uniform criteria as New Jersey
    preferred, such actions would not have eliminated case-by-case
    inquiries by the states and the EPA. Both the CTGs and ACTs
    are guidance documents, see Conn. Fund for the Env’t v. EPA,
    
    672 F.2d 998
    , 1003 (2d Cir. 1982); United States v. Ford Motor
    Co., 
    736 F. Supp. 1539
    , 1543 (W.D. Mo. 1990), and neither sets
    firm RACT requirements. Thus, despite the existence of the
    CTGs, the EPA makes case-specific determinations as part of its
    SIP approval process. Notice of Final Determination and
    Availability of Final Control Techniques Guidelines, 71 Fed.
    Reg. at 58,747. ACTs are also merely guidelines and do not
    create presumptive RACT levels. Phase 2 Rule, 70 Fed. Reg. at
    71,654/3. As case-by-case determinations would be necessary
    even if the EPA had revised the guidance documents, the EPA
    could reasonably determine that the costs entailed in revising the
    guidance documents outweighed the benefits. The EPA has
    discretion to consider the costs of regulation unless the relevant
    statute precludes such a consideration. See, e.g., Sierra Club,
    
    294 F.3d at 162-63
    .
    13
    The EPA’s approach also addresses New Jersey’s concern
    that allowing states to make RACT determinations by relying on
    15-year-old CTGs plus new information, if any, provided by the
    public in comments is “an inadequate substitute” for requiring
    each state to undertake a new RACT determination for each
    source category. As noted, the EPA has directed states to
    submit supporting documentation along with RACT
    certifications. Phase 2 Rule, 70 Fed. Reg. at 71,655/2. Thus, the
    EPA will have available the information needed to verify states’
    determinations that the previous controls are still appropriate
    under the 8-hour standard. Additionally, persons disagreeing
    with a particular RACT certification can seek judicial review of
    a particular SIP approval. A state may also complete an entirely
    new RACT analysis if it so chooses. Id. at 71,652/3.
    In sum, we hold that the EPA’s decision to forego a revision
    of the nationwide guidelines in favor of case-by-case RACT
    certifications was reasonable and not inconsistent with the
    statutory goal of expeditious attainment. Because the Phase 2
    Rule requires each state to verify that previously-required RACT
    controls still satisfy the RACT requirement, we need not address
    the EPA’s assertion that a new RACT determination will likely
    “result in the same or similar control technology as the initial
    RACT determination under the 1-hour standard because the
    fundamental control techniques . . . are still applicable.” Id. at
    71,654/1. The EPA did not rest the rule upon this ground; each
    state must “consider new information” — information that may
    prove the EPA wrong — when the state determines whether
    previously-required controls “still represent[] an appropriate
    RACT level of control.” Id. at 71,655/1.
    C. Meeting RACT via NOX SIP Call
    The NOX SIP Call is a cap-and-trade program that regulates
    NOX emissions. The program covers 22 states in the Northeast
    14
    and the District of Columbia, and was intended to address the
    interstate transport of ozone. See generally Final Rule, Finding
    of Significant Contribution and Rulemaking for Certain States
    in the Ozone Transport Assessment Group Region for Purposes
    of Reducing Regional Transport of Ozone, 
    63 Fed. Reg. 57,356
    (Oct. 27, 1998); Michigan v. EPA, 
    213 F.3d 663
    , 675, 685-86
    (D.C. Cir. 2000). The NOX SIP Call established for each state
    a “NOX emissions budget,” which limits total emissions during
    the ozone season. Phase 2 Rule, 70 Fed. Reg. at 71,656/3. The
    EPA also adopted a rule allowing interstate trading of emissions
    allowances, and all states covered by the NOX SIP Call elected
    to participate in the interstate program. Thus, a source within a
    state could meet its emissions target either by installing controls
    or by purchasing allowances from other sources located
    anywhere in the region covered by the NOX SIP Call. See id.
    The Phase 2 Rule provides that to meet the NOX RACT
    requirement, “the State need not perform (or submit) a NOX
    RACT analysis for sources subject to the state’s emission
    cap-and-trade program” where that program meets the NOX SIP
    Call requirements or, in states achieving CAIR reductions solely
    from Electricity Generating Units, CAIR requirements. Id. at
    71,652/3. Petitioners and intervenors persuasively challenge
    this provision as being contrary to the express terms of the
    statute.
    Section 172(c)(1) of the Act requires that nonattainment
    areas achieve “such reductions in emissions from existing
    sources in the area” as can be achieved by the adoption of
    RACT. 
    42 U.S.C. § 7502
    (c)(1). Thus, the RACT requirement
    calls for reductions in emissions from sources in the area;
    reductions from sources outside the nonattainment area do not
    satisfy the requirement. See id.; see also CAA § 182(b)(2), 42
    U.S.C. § 7511a(b)(2) (requiring implementation of RACT with
    respect to certain VOC sources “in the area” for moderate and
    15
    above nonattainment areas). Accordingly, participation in the
    NOX SIP Call could constitute RACT only if participation
    entailed at least RACT-level reductions in emissions from
    sources within the nonattainment area. In the preamble to the
    proposed rule the EPA stated that “the overall emission
    reductions from sources in the NOX SIP Call cap-and-trade
    program will achieve more emissions reductions in the
    nonattainment area than would application of RACT to each of
    those units,” Proposed Rule to Implement the 8-Hour Ozone
    National Ambient Air Quality Standard, 
    68 Fed. Reg. 32,802
    ,
    32,839 (June 2, 2003) (Proposed Rule). The preamble to the
    final rule does not go as far. Rather, the final preamble states
    only that the “NOX SIP Call is estimated to achieve a beyond-
    RACT degree of control regionally,” Phase 2 Rule, 70 Fed. Reg.
    at 71,657. Such regionwide RACT-level reductions in
    emissions do not meet the statutory requirement that the
    reductions be from sources in the nonattainment area. Because
    the EPA has not shown that NOX SIP Call compliance will result
    in at least RACT-level reductions in emissions from sources
    within each nonattainment area, the EPA’s determination that
    compliance with the NOX SIP Call satisfies the RACT
    requirement is inconsistent with the “in the area” requirement
    and thus violates the plain text of § 172(c)(1).
    In an analogous situation, the court invalidated the CAIR
    trading program because the EPA’s regionwide approach made
    it impossible to tell whether the rule achieved a specific
    statutory objective. See North Carolina v. EPA, 
    531 F.3d 896
    ,
    906-08 (D.C. Cir. 2008). In developing CAIR, the court
    explained, the EPA “did not purport to measure each state’s
    significant contribution to specific downwind nonattainment
    areas and eliminate them in an isolated state-by-state manner.”
    
    Id. at 907
    . Despite a statutory provision prohibiting sources
    “within the State” from contributing significantly to
    nonattainment in “any other State,” CAA § 110(a)(2)(D), 42
    
    16 U.S.C. § 7410
    (a)(2)(D), the EPA adopted a regionwide approach
    to the problem. The court therefore held that the EPA was not
    exercising its statutory duty, reasoning that “[i]t is unclear how
    EPA can assure that the trading programs . . . will achieve
    section 110(a)(2)(D)(i)(I)’s goals if we do not know what each
    upwind state’s ‘significant contribution’ is to another state.”
    
    531 F.3d at 908
    . Similar reasoning applies to the NOX SIP Call.
    The EPA has not provided assurance that the NOX SIP Call will
    achieve the Act’s goal of “reductions from existing sources in
    the area,” because it has not evaluated the effect of the program
    on each nonattainment area.
    The EPA responds that its approach “gives meaning to the
    statute’s ‘in the area’ language” because its technical analysis
    shows that the cap-and-trade programs achieve greater
    reductions than would the application of RACT-level controls
    at each source. EPA Br. at 73. However, the EPA’s cited
    support for this proposition is the statement from the preamble
    to the proposed rule stating the EPA “believes” participation
    would “achieve more emissions reductions in the nonattainment
    area than would application of RACT” to all sources in the area.
    Proposed Rule, 68 Fed. Reg. at 32,839/2. That statement is
    unsupported by any record evidence and it does not appear in
    the preamble to the final rule. The EPA’s further response that
    its technical analysis supports the conclusion that NOX SIP Call
    participation meets the RACT requirement is no more
    persuasive. The EPA explains that its analysis showed that
    sources subject to the NOX SIP Call “collectively” would
    achieve beyond-RACT reductions in emissions. EPA Br. at 83.
    But regionwide reductions do not satisfy the “in the area”
    requirement. The EPA explains further that it found that
    purchasing allowances was more costly than installing RACT-
    level control technology and thus “most” sources meeting the
    NOX SIP call, “assuming rational economic behavior,” id.,
    would opt to install controls rather than purchase allowances.
    17
    This bare assertion is insufficient to demonstrate that NOX SIP
    Call compliance would lead to RACT-level reductions from
    sources in the area. Even if most sources in a nonattainment
    area installed controls rather than purchasing allowances, a
    small number of sources purchasing allowances and increasing
    emissions could mean that overall emissions from sources in the
    area remained unchanged or even increased.
    The EPA’s attempt to show ambiguity in the Act is likewise
    unavailing. The EPA maintains the statute is ambiguous as to
    whether RACT must be installed at each source in an area,
    noting that it has previously approved the concept of averaging
    emissions within a nonattainment area. The EPA reads the
    statutory phrase “as may be obtained” to indicate that the RACT
    requirement does not necessarily call for implementation of
    controls at each and every source, but rather requires an area to
    achieve at least RACT-level reductions in emissions. Even if
    the RACT requirement could be met through an emissions-
    averaging approach within a nonattainment area, averaging
    emissions across a region does not ensure that any reductions in
    emissions derive from reductions at sources within a particular
    area. Even if the EPA were correct that “nothing in the statute
    precludes consideration of the air quality impact that controls
    under a region-wide cap-and-trade program may have on NOX
    within the nonattainment area,” EPA Br. at 72, the EPA has not
    considered the impact of the NOX SIP Call on the air quality
    within specific nonattainment areas. Therefore the EPA has
    failed to demonstrate that NOX SIP Call compliance can be
    equated to RACT compliance.
    The EPA’s reliance on § 172(c)(6) is misplaced. That
    section provides that SIPs must include “enforceable emission
    limitations, and such other control measures . . . including
    economic incentives such as . . . auctions of emission rights . .
    . as may be necessary or appropriate to provide for attainment.”
    18
    
    42 U.S.C. § 7502
    (c)(6). The EPA offers that its approach to
    RACT is consistent with this express authorization of auctions.
    However, § 172(c)(6) merely authorizes the EPA to approve
    market-based measures in addition to those controls that are
    required by CAA § 172(c), including the RACT requirement; it
    does not authorize the EPA to replace the RACT requirement
    with a cap-and-trade program as is promulgated in the Phase 2
    Rule.
    The EPA also offers that to the extent individual sources
    emitting high levels of NOX are in compliance with the NOX SIP
    Call through the purchase of allowances, the states can define
    RACT to require greater reductions than are required by the
    EPA, and they must require beyond-RACT reductions as
    necessary to achieve timely attainment.              The EPA’s
    determination that NOX SIP Call compliance satisfies the RACT
    requirement is not based on a state choosing to so exercise its
    discretion. A state’s decision to require stricter controls cannot
    eliminate the defect in the EPA’s approach — failing to
    implement the requirement of at least RACT-level reductions in
    emissions from sources in the nonattainment area. This part of
    the Phase 2 Rule must therefore be remanded without vacatur
    because the EPA may be able to reinstate the provision for most
    nonattainment areas if, upon conducting a technical analysis, it
    finds the NOX SIP Call results in greater emissions reductions in
    a nonattainment area than would be achieved if RACT-level
    controls were installed in that area.
    III. Clean Data Policy
    Under the Act, each nonattainment area must attain the
    NAAQS by a deadline, known as the “attainment date,” which
    is established by the statute itself for areas subject to Subparts
    1 and 2, see CAA § 181, 
    42 U.S.C. § 7511
    , and by the EPA for
    areas subject only to Subpart 1, see CAA § 172, 
    42 U.S.C. § 19
    7502(a)(2). The Act also provides that the SIP for a
    nonattainment area subject only to Subpart 1 must “require
    reasonable further progress” (RFP), 
    id.
     § 7502(c)(2); the SIP for
    an area in moderate or a greater degree of nonattainment must
    provide for fixed percentage reductions of VOCs on a specified
    schedule. CAA §§ 182 (b)(1)(A), (c)(2)(B), 42 U.S.C. §§
    7511a(b)(1)(A), (c)(2)(B).3
    In order to ensure these requirements are met, the SIP for
    any nonattainment area must include “contingency measures” to
    be implemented “if the area fails to make reasonable further
    progress, or to attain the [NAAQS] by the attainment date,”
    CAA § 172(c)(9), 
    42 U.S.C. § 7502
    (c)(9), and the SIP for a
    serious, severe, or extreme nonattainment area must also include
    “contingency measures” that will take effect automatically “if
    the area fails to meet any applicable milestone,” CAA §
    182(c)(9), 42 U.S.C. § 7511a(c)(9).
    In the Phase 2 Rule, the EPA suspended the planning
    requirements for specified percentage reductions and
    contingency measures for each nonattainment area that has
    attained the 8-hour NAAQS but has not yet been designated an
    attainment area. 
    40 C.F.R. § 51.918
    . The suspension lasts
    “until ... the area is redesignated to attainment, at which time the
    requirements no longer apply; or [until the] EPA determines that
    the area has violated the 8-hour ozone NAAQS.” 
    Id.
     The EPA
    3
    An area may in some circumstances substitute a combined
    reduction in emissions of VOCs and NOX for the fixed percentage
    reduction of VOCs required by CAA § 182(c)(2)(B). See 42 U.S.C.
    § 7511a(c)(2)(C). Although CAA § 182(b)(1)(A) applies by its terms
    only to an area in moderate nonattainment, and § 182(c)(2)(B) only to
    an area classified in serious nonattainment, § 182(c), (d), and (e) apply
    those requirements to areas in a greater degree of nonattainment. See
    id. § 7511a(c)-(e).
    20
    terms this suspension the “Clean Data Policy,” 70 Fed. Reg. at
    71,644, because it applies when a nonattainment area produces
    “clean” air quality data. See Memorandum from John S. Seitz,
    Dir., Office of Air Quality Planning & Standards, RFP,
    Attainment Demonstration, and Related Requirements for
    Ozone Nonattainment Areas Meeting the Ozone National
    Ambient Air Quality Standard, at 5 (May 10, 1995),
    www.epa.gov/ttn/oarpg/t1/memoranda/clean15.pdf . It adopted
    the current version of the policy in 1995 and applied it in
    rulemakings specific to individual areas under the 1-hour
    NAAQS; it will similarly determine whether individual areas
    qualify for the suspension in area-specific rulemakings. 70 Fed.
    Reg. at 71,644-45.
    The NRDC contends the Clean Data Policy conflicts with
    both the letter and the purpose of the Act. More specifically, the
    NRDC argues the statutory provisions requiring a SIP to include
    contingency measures and percentage reductions allow no
    waivers for an area that has achieved the NAAQS; the only way
    for an area to be absolved of those requirements is to be
    redesignated an attainment area. See CAA § 175A(c), 42 U.S.C.
    § 7505a(c) (“Until [a maintenance] plan revision is approved
    and an area is redesignated as attainment ... the requirements of
    [Part D] shall continue in force and effect”). Further, the NRDC
    argues only its reading of the text is consistent with the intent of
    the Congress that, in order to ensure the air stays clean, no
    mandatory control requirement be lifted until a maintenance
    plan is in place.
    The EPA responds first that the NRDC did not raise before
    the agency and therefore forfeited its objection to the suspension
    of the planning requirement for contingency measures. See
    CAA § 307(d)(7)(B), 
    42 U.S.C. § 7607
    (d)(7)(B) (“Only an
    objection to a rule or procedure which was raised with
    reasonable specificity during the period for public comment ...
    21
    may be raised during judicial review”). We agree. We
    “enforce[] this provision strictly,” Motor & Equip. Mfrs. Ass’n
    v. Nichols, 
    142 F.3d 449
    , 462 (D.C. Cir. 1998) (internal
    quotation marks omitted), and although we allow commenters
    “some leeway in developing their argument before this court,”
    the comment must have provided “adequate notification of the
    general substance of the complaint,” S. Coast Air Quality Mgmt.
    Dist. v. EPA, 
    472 F.3d 882
    , 891 (D.C. Cir. 2006).
    The NRDC’s comments did not provide the EPA adequate
    notice that it objected to the suspension of the contingency
    measures. The NRDC did object to the Clean Data Policy, but
    only to the suspension of the requirements for an attainment
    demonstration and percentage reductions. The NRDC now
    contends it objected to the suspension of all Subpart 2
    requirements, pointing to its comment that the “EPA cannot
    authorize states to simply drop subpart 2 measures when the area
    is meeting either standard. The Act allows states to move
    mandated controls to a maintenance contingency plan, but only
    after the area has been redesignated to attainment.” Comments
    of Clean Air Task Force et al., at 48 (Aug. 1, 2003). That
    comment, however, was made in the context of an objection to
    a different provision of the proposed rule, namely the EPA’s
    determination that an area not attaining the 1-hour standard but
    meeting the 8-hour standard need not submit a maintenance plan
    meeting the requirements of CAA § 175A. The EPA cannot be
    expected to take the NRDC’s argument, raised in support of one
    specific objection, and apply it sua sponte to another provision.
    Because the NRDC did not raise its objection with “reasonable
    specificity,” the Act bars us from considering it. CAA §
    307(d)(7)(B), 
    42 U.S.C. § 7607
    (d)(7)(B).
    On the merits, the EPA maintains the Clean Data Policy
    does not waive the planning requirements for percentage
    reductions; instead, it contends, those requirements are by their
    22
    terms inapplicable when an area meets the applicable NAAQS.
    See Phase 2 Rule, 70 Fed. Reg. at 71,645/1-2, 71,646/1-2.
    The two planning requirements for percentage reductions
    are CAA § 182(b)(1), which requires an initial reduction of 15%
    of VOC emissions in the first six years for an area in moderate
    or greater nonattainment, and § 182(c)(2)(B), which requires
    subsequent reductions in VOC emissions averaging 3% per year
    for an area in serious or greater nonattainment unless an
    exception applies. See 42 U.S.C. § 7511a(b)(1), (c)(2)(B). As
    the EPA interprets these provisions, specific percentage
    reductions are required only as necessary to achieve attainment.
    We think the statute unclear as to whether those sections
    apply to an area that is already attaining the NAAQS. For the
    reasons below, we join the Tenth Circuit in holding the EPA’s
    interpretation is reasonable. See Sierra Club v. EPA, 
    99 F.3d 1551
     (10th Cir. 1996).
    Section 182(b)(1)(A)(i) initially requires the SIP for an area
    in moderate or greater nonattainment to plan a total reduction in
    VOC emissions of 15% over six years. 42 U.S.C. §
    7511a(b)(1)(A)(i). In the very next sentence, however, it
    elaborates that a plan should mandate “such specific annual
    reductions ... as necessary to attain the [NAAQS] for ozone by
    the attainment date.” Id. Moreover, each percentage reduction
    is linked to the requirement that an area make “reasonable
    further progress” toward attainment. See id. § 7511a(b)(1)
    (entitled “Plan provisions for reasonable further progress”); id.
    § 7511a(c)(2)(B) (entitled “Reasonable further progress
    demonstration”). “Reasonable further progress,” in turn, means
    “such annual incremental reductions in emissions ... as are
    required ... for the purpose of ensuring attainment.” CAA §
    171(1), 
    42 U.S.C. § 7501
    (1). The Act is therefore ambiguous as
    to what reductions are required when no further progress toward
    23
    attainment is necessary — or, for that matter, possible. The
    EPA reasonably resolved this ambiguity by concluding the
    specific percentage reductions are simply inapplicable in that
    circumstance. As the Tenth Circuit put the matter, “If a
    moderate ozone nonattainment area has in fact already attained
    the ozone standard, it would make little sense to require a state
    to demonstrate the area will make reasonable progress toward
    attainment.” Sierra Club, 
    99 F.3d at 1557
    .
    The EPA’s reasoning disposes as well of the NRDC’s
    contentions that the Clean Data Policy unlawfully circumvents
    the redesignation requirements, CAA § 107(d)(3)(E), 
    42 U.S.C. § 7407
    (d)(3)(E), violates the mandate that all Part D
    requirements remain in force until an area has an approved
    maintenance plan in place, CAA § 175A(c), 42 U.S.C. §
    7505a(c), and disregards the Supreme Court’s admonition that
    the EPA cannot “render Subpart 2’s carefully designed
    restrictions on EPA discretion utterly nugatory,” Whitman v.
    Am. Trucking Ass’ns, 
    531 U.S. 457
    , 484 (2001). The Clean Data
    Policy does not effect a redesignation; an area must still comply
    with the statutory requirements before it can be redesignated to
    attainment. Furthermore, Part D — including Subpart 2 —
    remains in force insofar as it applies but, as we have just seen,
    the EPA has reasonably concluded the provisions of the Act
    requiring percentage reductions do not apply to an area that has
    attained the NAAQS.
    IV. 15% VOC Reduction
    CAA section 182(b)(1) requires that, for a moderate
    nonattainment area, “no later than 3 years after November 15,
    1990, the State shall submit a revision to the applicable
    implementation plan to provide for volatile organic compound
    emission reductions, within 6 years after November 15, 1990, of
    at least 15 percent from baseline emissions, accounting for any
    24
    growth in emissions after 1990.” 42 U.S.C. § 7511a(b)(1)(A)(i).
    CAA section 182(c), (d) and (e) incorporate the 15% VOC
    reduction requirement for, respectively, “serious,” “severe” and
    “extreme” nonattainment areas. Id. § 7511a(c)-(e). After the
    initial six-year period, CAA section 182(c), (d) and (e) impose
    on the same areas an additional RFP requirement that the SIP be
    revised so that it “will result in VOC emissions reductions from
    the baseline emissions . . . [of] at least 3 percent of baseline
    emissions each year,” “averaged over each consecutive 3-year
    period beginning 6 years after November 15, 1990, until the
    attainment date.” Id. § 7511a(c)(2)(B)(i) (imposing requirement
    on “serious” areas); see id. § 7511a(d), (e) (incorporating 3%
    reduction requirement for “severe” and “extreme” areas).4 As
    used in the cited provisions, “the term ‘baseline emissions’
    means the total amount of actual VOC or NOx emissions from
    all anthropogenic sources in the area during the calendar year
    1990.” CAA § 182(b)(1)(B), 42 U.S.C. § 7511a(b)(1)(B); see
    also CAA § 182(c)(2)(B), 42 U.S.C. § 7511a(c)(2)(B).5
    In the Phase 2 Rule, the EPA determined that for all
    moderate and above areas “that had not met the 15 percent VOC
    emission reduction requirement for the 1-hour standard,” the
    RFP 15% reduction requirement “would apply” under the 8-hour
    4
    The statute permits a reduction in “an amount less than 3
    percent of such baseline emissions each year, if the State demonstrates
    to the satisfaction of the Administrator that the plan reflecting such
    lesser amount includes all measures that can feasibly be implemented
    in the area, in light of technological achievability.” CAA §
    182(c)(2)(B)(ii), 42 U.S.C. § 7511a(c)(2)(B)(ii).
    5
    Section 182 does not provide for a specific VOC reduction for
    a moderate area following the initial six-year 15% reduction period.
    Accordingly, thereafter a moderate area is subject to the general
    requirement in CAA section 172(c)(2) that “plan provisions shall
    require reasonable further progress,” 
    42 U.S.C. § 7502
    (c)(2).
    25
    standard. 70 Fed. Reg. at 71,632-33. Conversely, the EPA
    determined, 8-hour moderate and above areas that had already
    satisfied the 15% VOC emission reduction for the 1-hour
    standard will not be subjected a second time to the 15%
    requirement under the 8-hour standard. Id. at 71,633. Thus,
    “[a]reas classified under subpart 2 as moderate that had met the
    15 percent VOC emission reduction requirement for the 1-hour
    standard are treated in the final rule like areas covered under
    subpart 1,” while “[a]reas classified under subpart 2 as serious
    and above that had met the 15 percent VOC emission reduction
    requirement for the 1-hour standard would be subject to the RFP
    requirement in section 172(e) [sic6] and the final rule would
    require them to obtain an average of 3 percent annual reductions
    of VOC and/or NOX emissions reductions for the first 6 years
    after the baseline year and every subsequent 3 years out to their
    attainment date.” Id. For both the 15% and the 3% reductions
    RFP requirements, the Phase 2 Rule provides that the RFP
    periods “would be equivalent to the periods Congress
    established in subpart 2,” id. at 71,633, running from a new
    baseline year, i.e., 2002 “for areas designated nonattainment for
    the 8-hour ozone NAAQS with an effective date of June 15,
    2004,” id. at 71,637.
    First, the NRDC argues that the EPA “illegally waived”
    Subpart 2’s RFP requirement that each SIP be revised three
    years after the statute’s effective date to provide for a 15% VOC
    reduction within 6 years after enactment for all areas classified
    as “moderate” and above for ozone.7
    6
    The EPA apparently meant section 172(c), see supra note 5;
    section 172(e) is the anti-backsliding provision, see infra pp. 43-45.
    7
    “Ozone, an essential presence in the atmosphere’s stratospheric
    layer, is dangerous at ground level” and “is formed by the chemical
    reaction of nitrogen oxides (‘NOX’) with any of a number of volatile
    26
    As an initial matter, the EPA did not “waive” the 15%
    requirement but simply determined that, if a State had made the
    required revision for an area classified as moderate or greater
    when the one-hour NAAQS took effect, the State did not have
    to do so a second time after the 8-hour standard took effect. In
    so doing, the EPA reasonably resolved a statutory ambiguity
    under step 2 of the framework set out in Chevron U.S.A. Inc. v.
    Natural Resources Defense Council, Inc., 
    467 U.S. 837
    , 843
    (1984). See Natural Res. Def. Council v. EPA, 
    489 F.3d 1250
    ,
    1257 (D.C. Cir. 2007) (“Under Chevron: We first ask ‘whether
    Congress has directly spoken to the precise question at issue,’ in
    which case we ‘must give effect to the unambiguously expressed
    intent of Congress.’ If the ‘statute is silent or ambiguous with
    respect to the specific issue,’ however, we move to the second
    step and defer to the agency’s interpretation as long as it is
    ‘based on a permissible construction of the statute.’ ” (quoting
    Chevron, 
    467 U.S. at 842-43
    ) (internal quotation marks
    omitted)). Accordingly, we reject the NRDC’s challenge to the
    VOC reduction provision.
    The NRDC contends that the EPA’s reading of the statute
    is “untenable” because the statute requires that the SIP provide
    for a 15% reduction from “baseline emissions”—which the
    “EPA itself defines . . . for purposes of the 8-hour ozone
    standard as emissions in 2002, not 1990”—and that the
    reduction be effected “ ‘within 6 years after’ the baseline
    year—that is, between 2002 and 2008 for the 8-hour standard.”
    NRDC Br. at 29. This argument, however, sidesteps the EPA’s
    rationale for its interpretation. The EPA identified a “gap in the
    statutory scheme” because “[t]he CAA is silent regarding
    whether a nonattainment area that implements the 15-percent
    VOC emission reduction of 42 U.S.C. § 7511a(b)(1)(A) must
    organic compounds (‘VOCs’), in the presence of sunlight.” S. Coast
    Air Quality Mgmt. Dist. v. EPA, 
    472 F.3d 882
    , 887 (D.C. Cir. 2006).
    27
    implement that provision a second time if the NAAQS is
    revised, or instead must implement other RFP provisions that
    expressly would have applied had there been no revision of the
    NAAQS.” EPA Br. at 29. The EPA filled this gap by selecting
    the latter resolution. As the EPA explained in the Phase 2 Rule,
    while it “believes that the CAA is quite clear that the SIP must
    provide for a 15 percent reduction in baseline VOC emissions
    for some period after 1990 in an area subject to section
    182(b)(1)(A),” it “disagrees that the CAA plainly requires that
    the SIP for an area must require a second 15 percent reduction
    in VOC baseline emissions under a revised ozone standard.” 70
    Fed. Reg. at 71,635-36 (first emphasis added); see also id. at
    71,634 (“For those areas that have an approved 15 percent plan
    for their 1-hour ozone SIPs, an additional 15 percent VOC
    reduction is not necessary.”). Because the EPA ended its
    statutory analysis with the threshold inquiry whether section
    182(b)(1)(A)(i) must be applied a second time under its revised
    standards (concluding it need not), the Agency did not need to
    decide how to interpret the term “baseline emissions” or to
    identify a baseline year for the purpose of so applying the
    provision. Further, because it had no need to reach these issues,
    it did not resolve them arbitrarily or capriciously, as the NRDC
    asserts, by “allowing a select group of nonattainment areas to
    rely on a different baseline from the distant past.” NRDC Br. at
    30-31. Had the EPA required a nonattainment area to undertake
    a second 15% VOC reduction, it might have been arbitrary to
    use a different baseline or baseline year from that applicable to
    areas undertaking the first 15% VOC reduction under the 8-hour
    standard. But the Agency did not do so and we will not
    speculate whether it could lawfully have done so.
    The NRDC also argues that the EPA’s 15% approach is
    inconsistent with its treatment of section 182(c)(2)(B)(i)’s 3%
    reduction requirement for serious and above areas in that the
    “EPA does not read the Act as excusing such 3% continuing
    28
    emission cuts for serious and above 8-hour nonattainment areas
    merely because they may have had plans under the 1-hour
    standard to achieve continuing (i.e. post-1996) cuts of 3%/yr
    from a 1990 baseline.” NRDC Br. at 30 n.8. The 3% provision,
    however, is fundamentally different from the 15% provision in
    that the former does not (as does the latter) establish a one-time
    reduction requirement but instead imposes a continuing
    obligation that applies to “each consecutive 3-year period
    beginning 6 years after November 15, 1990, until the attainment
    date.” CAA § 182(c)(2)(B), 42 U.S.C. § 7511a(c)(2)(B).
    Finally, the NRDC asserts that the “EPA cannot override an
    express statutory command ‘simply by asserting that its
    preferred approach would be better policy,’ ” NRDC Br. at 30
    (quoting Engine Mfrs. Ass’n v. EPA, 
    88 F.3d 1075
    , 1089 (D.C.
    Cir. 1996)), referring to the EPA’s observation that its approach
    “provides flexibility to States to use a mix of NOx and VOC
    reductions” under CAA section 172, 
    42 U.S.C. § 7502
    , rather
    than the required VOC-only reductions mandated by CAA
    section 182(b)(1)(A)(1), 42 U.S.C. § 7511a(b)(1)(A)(1). 70 Fed.
    Reg. at 71,634. As already explained, however, the EPA’s
    interpretation does not override an express command but rather
    resolves an ambiguity. Id. at 71,635-36. In commending the
    flexibility afforded, the EPA merely offered one more reason
    why its interpretation of the ambiguous statutory language is
    reasonable.
    V. New Source “Offset” Credit for Past Emission
    Reductions
    CAA section 172(b) requires that each State containing a
    nonattainment area submit a nonattainment SIP meeting the
    requirements of section 172(c) pursuant to a schedule set by the
    EPA but not later than three years after a nonattainment area is
    so designated. 
    42 U.S.C. § 7502
    (b), (c). Section 172(c)(5) of
    29
    the Act requires that each nonattainment area SIP “shall require
    permits for the construction and operation of new or modified
    major stationary sources anywhere in the nonattainment area, in
    accordance with section 7503 of [Title 42].” 
    Id.
     § 7502(c)(5).
    Section 173 sets out the permitting process, known as “New
    Source Review” (NSR), in greater detail, providing that a permit
    may be issued only if, inter alia, (1) the permitting agency has
    determined that by the time the source begins operation,
    sufficient offsetting emissions reductions are obtained that the
    emission levels from the offsets and the plan provisions
    represent RFP from the pre-permit levels, id. § 7503(a)(1)(A),8
    and (2) the proposed source will “comply with the lowest
    achievable emission rate” (LAER), id. § 7503(a)(2).9 Section
    8
    Section 173(a)(1)(A) requires that
    the permitting agency determine[] that—
    (A) by the time the source is to commence operation,
    sufficient offsetting emissions reductions have been
    obtained, such that total allowable emissions from
    existing sources in the region, from new or modified
    sources which are not major emitting facilities, and from
    the proposed source will be sufficiently less than total
    emissions from existing sources (as determined in
    accordance with the regulations under this paragraph)
    prior to the application for such permit to construct or
    modify so as to represent (when considered together with
    the plan provisions required under section 7502 of this
    title) reasonable further progress (as defined in section
    7501 of this title); . . . .
    
    42 U.S.C. § 7503
    (a)(1)(A).
    9
    Section 173(a) also requires that (1) the new source owner or
    operator has demonstrated that all of its other major stationary sources
    in the State are subject to and in (or scheduled for) compliance with
    30
    173 further requires that “[s]uch emission reductions shall be, by
    the time a new or modified source commences operation, in
    effect and enforceable and shall assure that the total tonnage of
    increased emissions of the air pollutant from the new or
    modified source shall be offset by an equal or greater reduction,
    as applicable, in the actual emissions of such air pollutant from
    the same or other sources in the area.” 
    Id.
     § 7503(c)(1). Subpart
    2 specifically applies the NSR requirement to ozone
    nonattainment areas, CAA § 182(a)(2)(C)(i), 42 U.S.C.
    § 7511a(a)(2)(C)(i), and mandates increasingly stringent offset
    ratios as the ozone classification increases, CAA § 182(a)(4),
    (b)(5), (d)(2), 42 U.S.C. § 7511a(a)(4), (b)(5), (d)(2).10
    The Phase 2 Rule allows proposed new and modified
    sources to meet this offset requirement using credits from
    sources that shut down or curtailed operations as long ago as
    1977. 70 Fed. Reg. at 71,699 (to be codified at 
    40 C.F.R. § 51.165
    ). The EPA has long allowed emissions reductions
    occurring before a permit application to qualify as offset credits
    under specified circumstances. Before 1989, such pre-
    application emissions reductions could be offset only if the
    proposed source was “a replacement for the productive capacity
    applicable emission limitations and standards; (2) the Administrator
    has not determined the implementation plan applicable to the
    attainment area site of the new source is not being adequately
    implemented; and (3) an analysis of alternatives demonstrates that
    “benefits of the proposed source significantly outweigh the
    environmental and social costs imposed as a result of its location,
    construction, or modification.” 
    42 U.S.C. § 7503
    (a)(3)-(5).
    10
    More generally, the Act requires that all SIPs, even those for
    attainment areas, include regulation of new and modified sources “as
    necessary to assure that national ambient air quality standards are
    achieved, including a permit program as required in parts C and D of
    this subchapter.” CAA § 110(a)(2)(C), 
    42 U.S.C. § 7410
    (a)(2)(C).
    31
    represented by the proposed offset credit.” Requirements for
    Implementation Plans; Air Quality New Source Review, 
    54 Fed. Reg. 27,286
    , 27,290 (June 28, 1989).11 The 1989 Rule
    eliminated this restriction for an area with an approved
    attainment demonstration. 
    Id. at 27,292
    . In the Phase 2 Rule,
    the EPA “lift[ed] the requirement to have an approved
    attainment plan before using preapplication credits from
    shutdowns or curtailments as offsets.” 70 Fed. Reg. at 71,676.
    The NRDC challenges both the EPA’s longstanding policy
    allowing pre-application reductions as NSR offsets and the
    EPA’s elimination in the Phase 2 Rulemaking of the approved
    attainment demonstration requirement. We reject as untimely
    the NRDC’s challenge to the general policy of allowing pre-
    application offset credits but we agree that eliminating the
    attainment demonstration requirement was arbitrary and
    capricious and therefore in violation of the APA.
    11
    The pre-1989 regulation provided:
    Emissions reductions achieved by shutting down an existing
    source or permanently curtailing production or operating
    hours below baseline levels may be credited, provided that
    the work force to be affected has been notified of the
    proposed shutdown or curtailment. Source shutdowns and
    curtailments in production or operating hours occurring
    prior to the date the new source application is filed generally
    may not be used for emissions offset credit. However,
    where an applicant can establish that it shut down or
    curtailed production after August 7, 1977, or less than one
    year prior to the date of permit application whichever is
    earlier, and the proposed new source is a replacement for the
    shutdown or curtailment credit for such shutdown or
    curtailment may be applied to offset emissions from the new
    source.
    
    40 C.F.R. § 51.165
    (a)(3)(ii)(C) (1988).
    32
    CAA section 307(b), which governs judicial review of a
    rulemaking under the Act, requires that “[a]ny petition for
    review . . . shall be filed within sixty days from the date notice
    of such promulgation . . . appears in the Federal Register.” 
    42 U.S.C. § 7607
    (b)(1). As already noted, the EPA has allowed
    emission reductions from pre-application source shutdowns and
    curtailments to qualify as NSR offset credits since at least 1989.
    See 54 Fed. Reg. at 27,292. Thus, the deadline for filing a
    petition for review of section 51.165(a)(3)(ii)(C) insofar as it
    authorizes offset credits for pre-permit emission reductions is
    long since past and the court lacks jurisdiction to review it. See
    Motor & Equip. Mfrs. Ass’n v. Nichols, 
    142 F.3d 449
    , 460 (D.C.
    Cir. 1998) (section 7607(b)(1) “filing period is jurisdictional in
    nature, and may not be enlarged or altered by the courts”
    (internal quotation marks omitted)). Nonetheless, the NRDC
    contends that the EPA “reopened” the 1989 offset policy so as
    to make its challenge timely. We disagree.
    “The reopening doctrine allows an otherwise stale challenge
    to proceed because ‘the agency opened the issue up anew,’ and
    then ‘reexamined . . . and reaffirmed its [prior] decision.’ ” P &
    V Enters. v. U.S. Army Corps of Eng’rs, 
    516 F.3d 1021
    , 1023-24
    (D.C. Cir. 2008) (quoting Pub. Citizen v. Nuclear Reg. Comm’n,
    
    901 F.2d 147
    , 150-51 (D.C. Cir. 1990)) (internal quotation
    marks omitted). In this case, the EPA did not expressly reopen
    the issue of offsets for pre-application emission reductions. In
    its proposed rule, the EPA offered two alternative amendments
    to section 51.165(a)(3)(ii)(C), each of which eliminated the
    attainment demonstration requirement under certain
    circumstances. See Prevention of Significant Deterioration
    (PSD) and Nonattainment New Source Review (NSR), 
    61 Fed. Reg. 38,250
    , 38,311-14 (July 23, 1996) (Proposed Rules). In the
    Phase 2 Rule, the EPA selected the less restrictive of the two
    33
    alternatives.12 Neither alternative proposed changing the
    regulation insofar as it permits offset of pre-application emission
    reductions generally or even mentioned the matter. Further,
    other than eliminating the approved attainment demonstration
    requirement, the language of amended section 51.165(a)(3)(C)
    remains substantively identical to the 1989 regulation. Compare
    54 Fed. Reg. at 27,299 (§ 51.165(a)(3)(C) as effective June 29,
    1989), with 70 Fed. Reg. at 71,699 (§ 51.165(a)(3)(C) as
    effective Jan. 30, 2006). Accordingly, the subject of allowing
    offsets in general was not expressly reopened. See Nat’l Ass’n
    of Reversionary Prop. Owners v. Surface Transp. Bd., 
    158 F.3d 135
    , 142 (D.C. Cir. 1998) (“When an agency invites debate on
    some aspects of a broad subject, . . . it does not automatically
    reopen all related aspects including those already decided.”)
    Nor did the EPA constructively reopen the issue, as the
    NRDC contends. Under some circumstances an issue may be
    “deemed to have been constructively reopened even though it
    was not actually reopened” in a literal sense. Kennecott Utah
    Copper Corp. v. U.S. Dep’t of Interior, 
    88 F.3d 1191
    , 1214
    (D.C. Cir. 1996). “A constructive reopening occurs if the
    revision of accompanying regulations ‘significantly alters the
    stakes of judicial review’ as the result of a change that ‘could
    have not been reasonably anticipated.’ ” Sierra Club v. EPA,
    
    551 F.3d 1019
    , 1025 (D.C. Cir. 2008) (quoting Kennecott, 
    88 F.3d at 1227
    ; Envtl. Def. v. EPA, 
    467 F.3d 1329
    , 1334 (D.C. Cir.
    2006)). The EPA’s elimination of the attainment determination
    requirement did not work such a sea change. The basic
    regulatory scheme remains unchanged: pre-application offsets
    are permitted if certain requirements are met. The only change
    12
    Alternative 1 conditioned using offset credits upon an area
    being “current with part D ozone nonattainment planning
    requirements”; Alternative 2, which the EPA selected, did not. Phase
    2 Rule, 70 Fed. Reg. at 71,673.
    34
    is the elimination of the attainment demonstration
    requirement—which was itself added in 1989 to replace the
    more stringent requirement that “the proposed new source [be]
    a replacement for the shutdown or curtailment.” 
    40 C.F.R. § 51.165
    (a)(3)(ii)(C) (1988) (alteration added); see supra note
    11. That the NRDC’s challenge to the change may have merit,
    as indeed we conclude infra, does not provide a ground to
    conclude that the broader issue of allowing any pre-application
    offsets at all has been reopened. It simply means the particular
    change it challenges is unlawful. The “stakes” here are not
    quantitatively different from what they were in 1989 when a
    coalition of environmental groups argued to the EPA that the
    attainment demonstration requirement itself was inadequate to
    ensure RFP. See 54 Fed. Reg. at 27,291-92. Yet no one then
    challenged the general policy allowing pre-application offsets.
    Further, it could have been “reasonably anticipated” at that time
    that the EPA might subsequently eliminate the attainment
    demonstration requirement itself in favor of an alternative
    safeguard which would likewise allow more liberal use of pre-
    application offset credits, as in fact happened here. In sum, the
    EPA has done nothing since 1989 to reopen the general issue of
    allowing pre-application offsets either expressly or
    constructively.
    We next address the NRDC’s objection to the specific NSR
    revision that is subject to review in this proceeding—that the
    EPA erred in eliminating the attainment demonstration
    requirement. We agree with the NRDC that the EPA acted
    arbitrarily and capriciously when it did so.
    In the 1989 rulemaking, the EPA imposed the approved
    attainment demonstration requirement in order to comply with
    CAA section 173(a)(1), which allows an NSR permit to issue
    only if
    35
    the permitting agency determines that—
    (A) by the time the source is to
    commence operation, sufficient offsetting
    emissions reductions have been obtained,
    such that total allowable emissions from
    existing sources in the region, from new or
    modified sources which are not major
    emitting facilities, and from the proposed
    source will be sufficiently less than total
    emissions from existing sources allowed
    under the applicable implementation plan
    prior to the application for such permit to
    construct or modify so as to represent (when
    considered together with the plan provisions
    required under section 7502 of this title)
    reasonable further progress (as defined in
    section 7501 of this title); . . . .
    
    42 U.S.C. § 7503
    (a)(1)(A) (1989). The EPA concluded that the
    “essence of [this] provision is that a new source may be allowed
    in a nonattainment area only where its presence would be
    consistent with RFP toward attainment of the NAAQS” and that
    this policy is satisfied if there is in place for the area a “fully
    approved SIP” since, “[b]y definition, any fully approved SIP
    has independently assured RFP and attainment.” 54 Fed. Reg.
    at 27,292. “[W]here an attainment demonstration is lacking,”
    however, the EPA concluded that “retention of the current
    shutdown credit restriction on offset transactions”—that is, for
    a pre-permit shutdown, “the proposed source is a replacement
    for the productive capacity represented by the proposed offset,”
    id. at 27,290—“is necessary both to assure RFP and to guarantee
    that a new source does not cause or contribute to a violation of
    the NAAQS.” Id. at 27,292. Nonetheless, when the EPA
    amended section 51.165(a)(3)(C) in the Phase 2 Rule, it
    36
    eliminated the fully-approved SIP requirement without adding
    any other safeguard to ensure that issuing a particular permit is
    consistent with CAA section 173’s mandate that total reductions
    “represent . . . reasonable further progress.” 
    42 U.S.C. § 7503
    (a)(1)(A). The EPA justified eliminating the requirement
    on the ground that the 1990 amendments to the Act “changed
    the considerations involved” in that they “emphasized the
    emission inventory requirement in section 172(c)(3) as a
    fundamental tool in air quality planning” and “added new
    provisions keyed to the inventory requirement, including
    specific reduction strategies and [milestones] that measure
    progress toward attainment from the base year emissions
    inventory or subsequent revised inventories” along with “several
    adverse consequences where States fail to meet the planning or
    emissions reductions requirements.” 70 Fed. Reg. at 71,677; see
    also Reconsideration Notice, 72 Fed. Reg at 31,739. But
    imposing post hoc sanctions for failing to achieve RFP
    milestones does not accomplish what CAA section 173 requires,
    namely, that the EPA ensure that “by the time the source is to
    commence operation, sufficient offsetting emissions reductions
    have been obtained” to produce RFP, 
    42 U.S.C. § 7503
    (a)(1)(A)
    (emphasis added). Because the EPA has not explained how the
    amended rule, stripped of the approved attainment
    demonstration requirement, ensures that emission reductions are
    achieved “by the time” the new source begins operation rather
    than sometime down the road after milestones have been missed,
    we conclude that eliminating the requirement is arbitrary and
    capricious. See N. Baja Pipeline, LLC v. FERC, 
    483 F.3d 819
    ,
    821 (D.C. Cir. 2007) (under arbitrary and capricious standard,
    agency conclusions “must be reasonable and reasonably
    explained” (citing Nat’l Fuel Gas Supply Corp. v. FERC, 
    468 F.3d 831
    , 839 (D.C. Cir. 2006))); Transactive Corp. v. United
    States, 
    91 F.3d 232
    , 236 (D.C. Cir. 1996) (“In order to ensure
    that an agency’s decision has not been arbitrary, we require the
    agency to have identified and explained the reasoned basis for
    37
    its decision.” (citing F.J. Vollmer Co. v. Higgins, 
    23 F.3d 448
    ,
    451 (D.C. Cir. 1994); Nat’l Treasury Employees Union v.
    Horner, 
    854 F.2d 490
    , 498-99 (D.C. Cir. 1988))).13
    VI. NSR Limits on Pollution from New and Modified
    Major Sources
    Pursuant to the SIP NSR requirements of CAA Part D,
    supra pp. 28-30, the Phase 2 Rule accords a State three years to
    develop and submit an approvable nonattainment major NSR
    program for the 8-hour NAAQS. 70 Fed. Reg. at 71,672. In
    addition to the Part D requirements for nonattainment areas,
    however, CAA section 110(a)(2)(c) imposes on States a
    “general duty” to implement a NSR program in their SIPs for all
    areas, see supra note 10, which “exists during all periods,
    including before a State has an approved part D NSR permit
    program.” Id. at 71,677-78. Although section 110(a)(2)(c)
    requires that the SIP contain NSR provisions, it does not specify
    what NSR requirements apply during the period after an area is
    designated nonattainment but before the NSR SIP is effective.
    To fill this gap, the EPA decided in the Phase 2 Rule to retain an
    interim NSR regime it has used for this purpose since 1979,
    namely, Appendix S to 40 C.F.R. Part 51, which both establishes
    interim NSR permitting requirements paralleling the Act’s (in
    section IV.A) and provides for an exemption from the same
    requirements under certain circumstances (in section VI). The
    EPA further decided in the Phase 2 Rule, however, to eliminate
    an existing 18-month time limit on the applicability of Appendix
    S (including section VI’s exemption provision) to a given
    nonattaiment area. Petitioners NRDC and New Jersey challenge
    both the EPA’s general authority to exempt new sources from
    13
    In light of this conclusion, we need not consider the NRDC’s
    alternative contention that elimination of the requirement violates
    section 172(e) of the Act, 
    42 U.S.C. § 7502
    (e).
    38
    permitting requirements under section VI and, more specifically,
    its decision to eliminate the 18-month limit on such exemptions.
    We reject the petitioners’ objection to the EPA’s general
    exemption authority as untimely but agree that eliminating the
    18-month limit violates the “anti-backsliding” provision in CAA
    section 172(e), 
    42 U.S.C. § 7502
    (e).
    In 1979, the EPA codified in its regulations a three year-old
    “Emission Offset Interpretative Ruling” as Appendix S to 40
    C.F.R. Part 51 and directed that Appendix S was to “govern[]
    permits to construct and operate applied for before the deadline
    for having a revised SIP in effect that satisfies Part D.”
    Approval and Promulgation of Implementation Plans; Statutory
    Restriction on New Sources Under Certain Circumstances for
    Nonattainment Areas, 
    44 Fed. Reg. 38,471
    , 38,473 (July 2,
    1979) (codified at 
    40 C.F.R. § 52.24
    (c) (1979) (now § 52.24(k));
    see Emission Offset Interpretative Ruling, 
    44 Fed. Reg. 3274
    (Jan. 16, 1979) (codifying interpretive ruling in regulations). In
    so applying the interpretive rule, the EPA allowed a
    nonattainment area to avoid, during the period before the SIP
    was due, the statutory ban on all major source construction or
    modification in any nonattainment area not subject to a SIP that
    “me[t] the requirements of Part D (relating to nonattainment
    areas).” See Clean Air Act Amendments of 1977, Pub. L. No.
    95-95, § 108(b), 
    91 Stat. 685
    , 694 (Aug. 7, 1977) (establishing
    construction ban) (1977 CAA Amendments). The EPA noted at
    the time that the Congress had similarly adopted the rule (“as
    may be modified by rule of the Administrator”) to govern NSR
    during the interim period from enactment of the 1977 CAA
    amendments until July 1, 1979, when the statutory ban was to
    take effect. 44 Fed. Reg. at 38,472; 1977 CAA Amendments
    § 129(a)(1), 91 Stat. at 745 (adopting interpretive rule for
    interim before ban) (Aug. 7, 1977). The Congress eliminated
    the construction ban in 1990. Clean Air Act, Amendments, Pub.
    L. No. 101-549, § 101(c), 
    104 Stat. 2399
    , 2408 (1990).
    39
    In 1980, the EPA “clarif[ied]” Appendix S to limit to
    eighteen months the period during which it governed NSR in a
    qualifying nonattainment area. Approval and Promulgation of
    Implementation Plans; Statutory Restriction on New Sources
    Under Certain Circumstances for Nonattainment Areas, 
    45 Fed. Reg. 65,209
     (Oct. 2, 1980). Since that time the EPA has
    continued to apply Appendix S’s NSR requirements in the
    interim after an area’s nonattainment designation and before
    implementation of a revised SIP. Thus, after the Congress
    amended the Act in 1990—adding, inter alia, Subpart 2’s
    ozone-specific requirements—the EPA again affirmed its policy
    that Appendix S govern during the period between
    nonattainment designation and SIP approval and
    implementation. See State Implementation Plans; General
    Preamble for the Implementation of Title I of the Clean Air Act
    Amendments of 1990; Supplemental, 
    57 Fed. Reg. 18,070
    ,
    18,076 (Apr. 28, 1992).
    Since Appendix S was formally codified in 1979, section VI
    thereof has contained— unchanged—an exemption from section
    IV.A’s permitting requirements for an area whose attainment
    date had not passed if the source satisfied two conditions:
    In such cases, a new source which would cause or
    contribute to an NAAQS violation may be exempt
    from the Conditions of Section IV.A. so long as the
    new source [1.] meets the applicable SIP emission
    limitations and [2.] will not interfere with the
    attainment date specified in the SIP under Section 110
    of the Act.
    44 Fed. Reg. at 3285 (codified at Appendix S, § VI); cf. 40
    C.F.R. pt 51, app. S., § VI (2006) (same). In the Phase 2 Rule,
    the EPA added a third condition so that the reformulated
    provision now exempts new sources from the permitting
    40
    requirements in section IV.A “if the conditions in paragraphs
    VI.A through C are met,” namely:
    A. The new source meets the applicable SIP emission
    limitations.
    B. The new source will not interfere with the
    attainment date specified in the SIP under section 110
    of the Act.
    C. The Administrator has determined that conditions A
    and B of this section are satisfied and such
    determination is published in the Federal Register.
    70 Fed. Reg. at 71,704 (codified at 40 C.F.R. pt 51, app. S., § VI
    (2009)). The EPA further eliminated the 18-month limit on the
    applicability of Appendix S (including section VI) to a pre-SIP
    nonattainment area. 70 Fed. Reg. at 71,677; see 
    40 C.F.R. § 52.24
    (k) (2009).
    As noted above, petitioners NRDC and New Jersey
    challenge the EPA’s authority generally to exempt an area from
    Appendix S’s permitting requirements and specifically the
    EPA’s removal of the 18-month limit. We address each in turn.
    First, we consider the general challenge to the EPA’s
    exemption authority and conclude that it is time-barred. Under
    CAA section 307(b), any objection to the exemption policy was
    required to be raised in a petition for review “filed within sixty
    days from the date notice of [its] promulgation . . . appears in the
    Federal Register,” 
    42 U.S.C. § 7607
    (b)(1). In this case the
    triggering date was July 2, 1979, when the EPA published its
    final rule promulgating 
    40 C.F.R. § 52.24
    (c) (1979) (now
    52.24(k)), which directed that “[t]he Emission Offset
    Interpretative Ruling, 40 CFR Part 51, Appendix S”—which, as
    41
    then codified, contained the exemption provision in section VI,
    44 Fed. Reg. at 3285—“governs permits to construct and
    operate applied for before the deadline for having a revised SIP
    in effect that satisfies Part D.” 44 Fed. Reg. at 38,473 (codified
    at 
    40 C.F.R. § 52.24
    (c) (1979) (now 52.24(k)). It was on that
    date that the EPA unequivocally asserted its authority to exempt
    new sources from permitting requirements under section VI.
    Thus, the petitioners’ challenge to such authority in this case
    comes almost thirty years late and we are precluded from
    considering it. See Motor & Equip. Mfrs. Ass’n, 
    142 F.3d at 460
    . Nonetheless, the petitioners again (as with the emission
    offset authority issue treated supra) seek to circumvent the
    statutory time limit by invoking the reopening doctrine. Once
    again their attempt is unavailing.
    The petitioners contend the EPA implicitly reopened the
    question of its exemption authority because during the
    rulemaking, the Agency sought comment on an alternative
    exemption proposal which it subsequently declined to adopt.
    See Edison Elec. Inst. v. EPA, 
    996 F.2d 326
    , 332 (D.C. Cir.
    1993) (“By soliciting comments on the existing . . . regulations
    and advancing a possible ‘alternative approach’ . . ., the EPA
    clearly provided the type of ‘opportunity for renewed comment
    and objection’ that suffices to restart the statutory period for
    seeking review.” (quoting Ohio v. EPA, 
    838 F.2d 1325
    , 1328
    (D.C. Cir. 1988)). Specifically, the petitioners argue that the
    EPA reopened the question of its exemption authority when it
    “proposed to remove the general waiver language from
    Appendix S entirely, and replace it with a ‘transitional’ program
    that would only allow relief from NSR in a limited group of
    areas that, among other things, submitted plans by 2004
    adequate to attain standards by 2007”—a proposal the EPA
    subsequently declined to adopt. NRDC Br. at 41 (citing 68 Fed.
    Reg. at 32,846-48) (emphases in brief). As the petitioners’
    characterization demonstrates, however, the EPA reopened only
    42
    the question of how broadly it should exercise its exemption
    authority and not whether it had such authority in the first place.
    The abandoned proposal would have replaced section VI’s
    exemption provisions with a “transitional” program, which
    would, like section VI, provide exemptions from section IV.A’s
    NSR requirements but would allow the exemptions for a
    narrower class of “eligible” areas. See Proposed Rule To
    Implement the 8-Hour Ozone National Ambient Air Quality
    Standard, 
    68 Fed. Reg. 32,802
    , 32,846-47 (June 2, 2003) (setting
    out eligibility requirements for transitional program). Thus, the
    EPA’s alternative proposal did not implicitly reopen the
    question of its statutory authority vel non to grant any NSR
    exemptions but only whether section VI as previously applied
    might violate the Act by making exemptions too broadly
    available. Because the EPA did not seek comment on its general
    authority to exempt areas from the permitting requirements, this
    case is plainly distinguishable from Edison Electric Institute, in
    which the EPA “explicitly invited comments on the precise
    question for which petitioners [there sought] review.” Edison
    Elec. Inst., 
    996 F.2d at 332
    . Accordingly, we conclude that the
    issue of the EPA’s general exemption authority is foreclosed
    under CAA section 307(b)(1), 
    42 U.S.C. § 7607
    (b)(1).
    The petitioners also argue that the EPA constructively
    reopened the entire exemption provision “by dramatically
    expanding its scope and effect” when it eliminated the 18-month
    limit on Section VI exemptions. NRDC Br. at 41(citing
    Kennecott, 
    88 F.3d at 1226-27
    ); see also NRDC Reply Br. at 18.
    The extension of the exemption term, however, did not
    “ ‘significantly alter[] the stakes of judicial review’ as the result
    of a change that ‘could have not been reasonably anticipated.’ ”
    Sierra Club v. EPA, 
    551 F.3d at 1025
     (quoting Kennecott, 
    88 F.3d at 1227
    ; Envtl. Def., 
    467 F.3d at 1334
    ). In fact, when first
    codified in 1979, the interpretive ruling lacked such a limit—yet
    its general exemption authority went unchallenged. Further, an
    43
    exemption from NSR for even 18 months, if unlawful, seems
    worth challenging in its own right—as it could have been when
    the 18-month limit was added in 1980. To the extent that the
    EPA’s removal of the limit extends the exemption period, the
    extension is subject to direct challenge in this proceeding and we
    next address the petitioners’ challenge thereto.
    The petitioners contend that the EPA’s elimination of the
    18-month limit on NSR exemptions violates CAA
    section 172(e), the Act’s “anti-backsliding” provision. Section
    172(e) provides that if the the EPA “relaxes a national primary
    ambient air quality standard,” it must “promulgate requirements
    applicable to all areas which have not attained that standard as
    of the date of such relaxation” which “shall provide for controls
    which are not less stringent than the controls applicable to areas
    designated nonattainment before such relaxation.” 
    42 U.S.C. § 7502
    (e). Although section 172(e) expressly applies only when
    the EPA “relaxes” a NAAQS, the EPA has interpreted the
    language to also apply when it strengthens a NAAQS—as it did
    when it adopted the 8-hour ozone standard—reasoning that “if
    Congress intended areas to remain subject to the same level of
    control where a NAAQS was relaxed, they also intended that
    such controls not be weakened where the NAAQS is made more
    stringent.” Final Rule To Implement the 8-Hour Ozone National
    Ambient Air Quality Standard—Phase 1, 
    69 Fed. Reg. 23,951
    ,
    23,972 (Apr. 30, 2004) (Phase 1 Rule). In South Coast Air
    Quality Management District v. EPA, 
    472 F.3d 882
     (D.C. Cir.
    2006), we upheld this interpretation, 
    id. at 900
    , and also
    concluded that NSR is a “control” subject to section 172(e)’s
    backsliding prohibition, 
    id. at 902
    . Accordingly, the EPA’s
    elimination of the 18-month exemption limit violates section
    172(e) if the resulting NSR requirement is “less stringent” than
    the existing requirement. Insofar as Appendix S now provides
    for waiver of NSR for an unlimited time pending SIP approval,
    it is plainly “less stringent” than the previous version which
    44
    limited an NSR waiver to an 18-month term. As the petitioners
    argue, the EPA’s revision could delay implementing NSR
    controls in eligible nonattainment areas for years beyond the
    previous 18-month limit. Accordingly, we conclude that the
    revision constitutes backsliding in violation of section 172(e).
    The EPA offers three defenses of its revision. First,
    because the EPA established the time limit to allow a newly-
    designated nonattainment area a reasonable time to develop a
    SIP before the statutory construction ban applied, see 45 Fed.
    Reg. at 65,209, the EPA contends that it reasonably removed the
    18-month limitation after the Congress repealed the new source
    construction ban in 1990. The EPA might have done so but for
    section 172(e)’s unequivocal backsliding constraint, which
    plainly prohibits a “less stringent” NSR control—precisely what
    the revision produced. Second, the EPA asserts “there is no
    basis to speculate” that it will grant waivers for the entire period
    before SIP approval because “it ‘would be highly disinclined to
    grant a waiver where the SIP submission deadline has passed
    and EPA had not received the required submission.’ ” EPA Br.
    at 102-03 (quoting 72 Fed. Reg. at 31,745-46). We do not
    speculate, however, in concluding that, notwithstanding the
    EPA’s promised discretionary restraint, the revised section VI
    will produce some waivers lasting beyond the previously
    prescribed 18-month period and thus impose a control less
    stringent than before. This result contravenes section 172(e).
    Nor are we persuaded by the EPA’s third argument, that the
    revision’s new, third “pre-condition”—that the EPA determine
    that the existing two pre-conditions (satisfaction of applicable
    SIP emission limitations and non-interference with SIP’s
    attainment date) have been met and publish the determination in
    the Federal Register—“tightened” Part VI’s requirements. EPA
    Br. at 103. The new pre-condition simply formalized and made
    explicit what was already implicitly required—that the EPA find
    the existing two pre-conditions satisfied. Thus, the additional
    45
    pre-condition produced no “tightening” effect; on the contrary,
    it did nothing to counteract the indisputably relaxing effect of
    removing the 18-month limit.
    VII. Baton Rouge’s Reformulated Gasoline Requirement
    The Chamber of Greater Baton Rouge and affiliated
    petitioners (Chamber) contend the EPA arbitrarily and
    capriciously concluded that the Baton Rouge, Louisiana area
    (Baton Rouge) is a “covered area” under CAA section 211(k),
    
    42 U.S.C. § 7545
    (k), and therefore subject to a statutory ban on
    the sale to consumers of conventional gasoline.14 We conclude
    that the EPA correctly determined the statutory definition of
    “covered area” is ambiguous as to Baton Rouge under Chevron
    step 1 and that it reasonably resolved the ambiguity under
    Chevron step 2.
    CAA section 211(k)(1) authorizes the EPA to “promulgate
    regulations . . . establishing requirements for reformulated
    gasoline to be used in gasoline-fueled vehicles in specified
    nonattainment areas.” 
    42 U.S.C. § 7545
    (k)(1). Section
    211(k)(5) makes unlawful “[t]he sale or dispensing by any
    person of conventional gasoline to ultimate consumers in any
    covered area”—necessitating the use of reformulated gasoline
    instead. 
    Id.
     § 7545(k)(5)(A). Section 211(k)(10), in turn,
    designates as a “covered area” each of nine specific, high ozone
    areas and further provides: “Effective one year after the
    reclassification of any ozone nonattainment area as a Severe
    ozone nonattainment area under section 7511(b) of this title,
    14
    Section 211(k) defines “conventional gasoline” as “any
    gasoline which does not meet specifications set by a certification
    under [section 211(k)]” as “reformulated gasoline.” 
    42 U.S.C. § 7545
    (k)(10)(E)-(F).
    46
    such Severe area shall also be a ‘covered area’ for purposes of
    this subsection.” 
    Id.
     § 7545(k)(10)(D).
    In 1991, the EPA classified Baton Rouge as a “serious”
    ozone nonattainment area under the 1-hour standard. On April
    24, 2003, the EPA reclassified Baton Rouge as “severe,”
    effective June 23, 2003, pursuant to the bump-up provision,
    CAA § 181(b)(2), 
    42 U.S.C. § 7511
    (b)(2), because Baton Rouge
    failed to reach attainment by its November 15, 1999 attainment
    date. Notice of Withdrawal of October 2, 2002, Attainment
    Date Extension, Determination of Nonattainment as of
    November 15, 1999, and Reclassification of the Baton Rouge
    Ozone Nonattainment Area, 
    68 Fed. Reg. 20,077
     (Apr. 24,
    2003) (effective June 23, 2003). At that time, the EPA advised
    that “under Section 211(k) of the Act the use of reformulated
    gasoline (RFG) will be required in the Baton Rouge area
    beginning one year from the effective date of this rule,” that is,
    as of June 23, 2004. 
    Id. at 20,080
    . On April 30, 2004, the EPA
    designated Baton Rouge as nonattainment under the 8-hour
    standard and classified it as “marginal,” effective June 15, 2004.
    Air Quality Designations and Classifications for the 8-Hour
    Ozone National Ambient Air Quality Standards; Early Action
    Compact Areas With Deferred Effective Dates, 
    69 Fed. Reg. 23,858
    , 23,907 (Apr. 30, 2004).
    The Chamber filed a request for extension of the deadline
    to commence using RFG or waiver of the RFG requirement,
    which the EPA denied in a letter dated May 5, 2004. The
    Chamber then petitioned the United States Court of Appeals for
    the Fifth Circuit for review of the denial and the Fifth Circuit
    stayed the RFG deadline on June 18, 2004. On August 2, 2004
    the Fifth Circuit granted a joint motion to stay its proceedings
    “pending the outcome of the administrative decision making
    process,” with the RFG deadline stay to remain in effect during
    47
    remand. City of Baton Rouge v. EPA, No. 04-60408 (5th Cir.
    Aug. 2, 2004).
    In the Phase 2 Rule, the EPA concluded that an area such as
    Baton Rouge, which automatically became a “covered area”
    (subject to the RFG requirement) on the one-year anniversary of
    its bump-up to “severe,” should remain subject to the RFG
    requirement notwithstanding its classification to a less-than-
    severe status under the 8-hour standard and the subsequent
    revocation of the 1-hour standard: “EPA has determined that
    bump-up areas that lose their severe classification based solely
    on revocation of the 1-hour NAAQS should remain RFG
    covered areas at least until they are redesignated to attainment
    for the 8-hour NAAQS.” 70 Fed. Reg. at 71,686.15 The EPA
    concluded that “section 211(k)(10)(D) is ambiguous on the issue
    of whether a bump-up area continues to be a covered area when
    it is no longer classified as severe” and that therefore “EPA has
    discretion to determine whether section 211(k)(10)(D)
    authorizes removal of a bump-up area from the RFG program
    when it is no longer classified as severe, and to set appropriate
    criteria for such removal.” Id. The EPA explained that it “d[id]
    not believe that Congress would have intended that removal of
    the severe classification based solely on revocation of the less
    protective 1-hour NAAQS should result in backsliding of the
    RFG requirement.” Id. The Agency further found it
    “instructive” that “if EPA had never revised the 1-hour
    NAAQS[,] . . . the area would continue to be a covered area at
    15
    The EPA stated it was “reserving for future consideration what
    RFG requirements, if any, should apply to the nine mandatory areas
    and the bump-up areas covered by this final rule when they are
    redesignated to attainment for the 8-hour NAAQS.” 70 Fed. Reg. at
    71,687. The EPA further noted its determination did “not change or
    affect any discretion EPA may otherwise have under the RFG
    provisions to modify or remove RFG requirements.” Id. at 71,686.
    48
    least until it was redesignated to attainment for the 1-hour
    NAAQS.” Id. Accordingly, because “[h]ere, the removal of the
    severe classification is through revocation of the 1-hour
    NAAQS, not through redesignation to 1-hour attainment,” the
    EPA determined that “the removal of the severe classification
    for these areas as a result of revocation of the 1-hour standard
    should not lead to removal of the RFG requirement.” Id. The
    Chamber offers three arguments against the EPA’s
    interpretation. We address and reject each argument in turn.
    First, the Chamber contends that at Chevron step 1 Baton
    Rouge never became a “covered area” because the plain and
    unambiguous language of the statutory definition requires that
    a “covered area” be “a ‘Severe area’ that remains severe ‘one
    year after the reclassification,’ ” Chamber Br. at 15 (quoting
    CAA § 211(k)(10)(D), 
    42 U.S.C. § 7545
    (k)(10)(D)), that is, on
    June 23, 2004, on which date Baton Rouge was no longer a
    severe area as it had become a marginal area on June 15, 2004.
    The EPA does not quibble with the Chamber’s interpretation of
    the statutory language to require that the area remain classified
    as “severe” on the one-year anniversary of the reclassification.
    See EPA Br. at 111 (“[O]nce an area is reclassified as ‘severe,’
    the only other precondition to becoming ‘covered’ is that the
    area remain in severe nonattainment status for one year.”)
    (emphasis in original). The EPA points out, however, that as of
    the one-year anniversary of the bump-up—June 23,
    20004—Baton Rouge was not only a marginal area under the 8-
    hour standard but was also a severe area under the 1-hour
    standard, which was not revoked until June 15, 2005, almost a
    year later. See Phase 1 Rule, 69 Fed. Reg. at 23,954 (“We will
    revoke the 1-hour standard in full, including the associated
    designations and classifications, 1 year following the effective
    date of the designations for the 8-hour NAAQS.”). Thus, the
    EPA reasonably determined that under the plain language of the
    49
    statute, Baton Rouge was a severe area as of June 23, 2004 and
    became a “covered area” on that date.16
    Second, the Chamber asserts at Chevron step 2 that even if
    the definition of “covered area” is ambiguous, the EPA resolved
    the ambiguity unreasonably in two respects. The Chamber first
    argues the EPA improperly relied on the Supreme Court’s
    decision in Whitman v. Am. Trucking Ass’ns, 
    531 U.S. 457
    (2001). In support of its interpretation, the EPA cited
    Whitman’s “caution[] . . . against EPA making subpart 2
    ‘abruptly obsolete,’ ” 70 Fed. Reg. at 71,686 (quoting Whitman,
    
    531 U.S. at 485
    ), observing that, “[a]lthough the RFG
    requirement itself is not set forth in subpart 2, the requirement
    to use it in severe bump-up areas is tied directly to the
    classifications that arise by operation of subpart 2” and therefore
    “it would appear that the Supreme Court's caution should be as
    relevant for RFG bump-up areas as it is for the subpart 2 control
    obligations.” 
    Id.
     Notwithstanding the Chamber’s contrary
    assertions, the EPA reasonably determined that “the inclusion of
    a bump-up area in the RFG program is integrally tied to the
    16
    The Chamber argues that this reasoning is foreclosed because
    the EPA itself “stated that the 8-hour NAAQS is the ‘relevant’
    standard.” Chamber Br. at 18 (quoting Phase 1 Rule, 69 Fed. Reg. at
    23,983). The EPA used the term “relevant,” however, in explaining
    why it had decided that “control obligations an area is required to
    retain in the approved SIP for an area’s 1-hour classification must
    continue to be implemented under the SIP until the area attains and is
    redesignated to attainment for the 8-hour NAAQS.” 69 Fed. Reg. at
    23,983; see id. (“Since the relevant NAAQS is now the 8-hour
    NAAQS, we believe it is appropriate to require these mandated
    controls to remain as part of the implemented SIP until an area attains
    the 8-hour NAAQS and is redesignated to attainment.”). Thus, the
    cited language in fact supports retaining the RFG control based on the
    one-hour standard bump-up until Baton Rouge reaches 8-hour
    attainment.
    50
    subpart 2 provisions that establish the original classification and
    attainment date for an area and its later reclassification,” id.,
    which provisions cause an area to become a “covered” RFG area
    by operation of law. Accordingly, the EPA reasonably relied on
    Whitman’s general admonition to preserve Subpart 2 to support
    the Agency’s particular determination that the effects of the
    integrally connected provisions should remain intact following
    conversion to the 8-hour standard.
    The Chamber also asserts the EPA’s interpretation falters at
    Chevron step 2 because the Agency unreasonably relied on “the
    very same provisions it referred to in the Phase 1 Rule at 
    69 Fed. Reg. 23972
    ,” which provisions, the Chamber maintains, “did not
    support the Phase 1 Rule, nor do they support the imposition of
    RFG.” Chamber Br. at 22-23 (citing 70 Fed. Reg. at 71,686).
    The Chamber examines each of the statutes cited in the Phase 1
    Rule and asserts, correctly, that none of them directly relates to
    the RFG requirement. See id. at 23-24. The Chamber makes too
    much, however, of the EPA’s citation to the Phase 1 Rule. The
    EPA was simply referring readers “[f]or further discussion of
    the reasoning behind anti-backsliding provisions in the Phase 1
    Rule” because the Agency also relied on the anti-backsliding
    rationale for its interpretation of the “covered area” definition in
    the Phase 2 Rule.17 See 70 Fed. Reg. at 71,686.
    17
    The Chamber also objects in particular to the EPA’s reliance on
    CAA section 172(e), the anti-backsliding provision. See Chamber Br.
    at 23-24; Chamber Reply Br. at 2-3. The Chamber argues section
    172(e) applies only when the EPA “relaxes” a standard and that, in
    promulgating the 8-hour standard, the EPA in fact strengthened, rather
    than relaxed, the standard. The EPA’s reliance on section 172(e) in
    the Phase 1 Rule, however, supported its specific policy against
    backsliding in converting to the 8-hour standard notwithstanding the
    8-hour standard is stricter (not more relaxed) than the one-hour
    standard. We have already upheld this policy as reasonable. See S.
    Coast, 472 F.3d at 900.
    51
    Having rejected the Chamber’s contrary arguments, we
    conclude that the EPA’s statutory interpretation readily satisfies
    Chevron step 2. In upholding the EPA’s interpretation as
    reasonable, we, like the Agency, find it “instructive” that but for
    the happenstance of the EPA’s adoption of 8-hour standards, the
    Chamber would have no statutory basis to dispute that Baton
    Rouge is a covered RFG area under the mandatory bump-up and
    RFG provisions because Baton Rouge remained a severe one-
    hour area for one year following its classification as such. See
    70 Fed. Reg. at 71,686 (quoted supra p. 47).
    Finally, the Chamber contends the EPA was arbitrary and
    capricious in not making a specific determination that RFG
    would “protect the public health” in Baton Rouge and asserts
    that in fact RFG will interfere with the area’s progress toward
    attainment, thereby harming the public health. The Chamber
    first asserts that the EPA was required by CAA section
    109(b)(1) to make a specific finding that requiring RFG
    “protects the public health” of Baton Rouge, citing 
    42 U.S.C. § 7409
    (b)(1) (“National primary ambient air quality standards,
    prescribed under subsection (a) of this section shall be ambient
    air quality standards the attainment and maintenance of which
    in the judgment of the Administrator, based on such criteria and
    allowing an adequate margin of safety, are requisite to protect
    the public health.”). The Chamber further argues that requiring
    RFG in Baton Rouge will interfere with the area’s attainment
    because studies have shown RFG increases NOx levels and
    Baton Rouge’s SIP strategy for reducing ozone relies largely on
    reducing NOx (and not VOCs). By interfering with attainment,
    the Chamber contends, RFG in fact endangers the public health.
    As an initial matter, the Chamber’s objections based on harm to
    public health and interference with RFP and attainment are
    forfeited because they were not raised before the Agency. See
    CAA § 307(d)(7)(B), 
    42 U.S.C. § 7607
    (d)(7)(B) (“Only an
    objection to a rule or procedure which was raised with
    52
    reasonable specificity during the period for public comment
    (including any public hearing) may be raised during judicial
    review.”). To the extent Baton Rouge argues that RFG will not
    improve the public health, the EPA adequately addressed these
    objections and reasonably determined they may best be resolved
    through individual waiver requests.18
    In the Phase 2 Rulemaking, the Baton Rouge Clean Air
    Coalition asserted that RFG use in Baton Rouge would “provide
    no measurable benefits for NOx,” “less than 2 tons per day of
    VOC reductions, and “an ozone benefit . . . of around 0.26 ppb,”
    and asked whether these data “qualify as an ‘absurd result’ and
    [would] be subject to consideration for waiver.” Letter from
    Mike D. McDaniel, Executor Director, Baton Rouge Clean Air
    Coalition to U.S. EPA at 4 (July 30, 2003); see Phase 2 Rule, 70
    Fed. Reg. at 71,687-88. In response, the EPA noted that Baton
    Rouge had “submitted requests for an RFG waiver and for a
    waiver of the RFG oxygen content requirement, which are
    currently before the Agency.” 70 Fed. Reg. at 71,688. Based on
    its determination that “the transition to the more protective
    8-hour standard should [not] result in less restrictive
    requirements for RFG than would apply if the EPA had never
    revised the 1-hour standard,” the EPA advised that “[t]he
    appropriate mechanism to address Baton Rouge’s concerns is
    . . . in the context of Baton Rouge’s petitions for relief under the
    RFG program, and not by establishing different, less restrictive
    RFG requirements as part of the transition to the 8-hour
    standard.” Id. Baton Rouge’s waiver request is ongoing before
    the Agency with judicial review available in the Fifth Circuit.
    The EPA’s decision to address site-specific data and concerns in
    18
    As the EPA notes, the Chamber submitted material originating
    in the Fifth Circuit proceeding to support these objections but the
    material was not submitted during the proceeding before the Agency.
    See EPA Br. at 116.
    53
    an individual waiver proceeding, rather than in the general
    rulemaking, is reasonable. Cf. Nat’l Wildlife Fed’n v. EPA, 
    286 F.3d 554
    , 566 (D.C. Cir. 2002) (upholding as reasonable EPA’s
    decision to address “color pollution” “on a case-by-case basis
    through individual [National Pollutant Discharge Elimination
    System] permits or, when appropriate, through local limits”
    rather than “to establish nationwide standards for discharge of
    ‘color’ ”).
    VIII. Conclusion
    In sum, we hold (1) the Phase 2 Rule violates the Act by
    allowing participation in the NOX SIP Call to satisfy the
    requirement that a nonattainment area mandate such reductions
    as can be achieved by the application of RACT, (2) the EPA
    acted arbitrarily when it eliminated the requirement that an
    attainment demonstration be approved for an area before a new
    source would be allowed to use a past emission reduction to
    offset new emissions, and (3) the elimination of the 18-month
    time limit for NSR waivers under Appendix S violates the
    anti-backsliding provision of the Act. In light of the likelihood
    the EPA will be unable to cure the backsliding inherent in the
    removal of the 18-month time limit, we vacate that provision of
    the Phase 2 Rule and remand it to the EPA. See Ill. Pub.
    Telecomms. Ass’n v. FCC, 
    123 F.3d 693
    , 693 (D.C. Cir. 1997)
    (“When this court remands a rule ... with little or no prospect of
    the rule’s being readopted upon the basis of a more adequate
    explanation of the agency’s reasoning, the practice of the court
    is ordinarily to vacate the rule”). We remand to the EPA
    without vacatur the other two provisions of the Phase 2 Rule we
    hold invalid. We defer consideration of the Phase 2 Rule and
    Reconsideration Notice insofar as they relate to the CAIR
    program, and we deny the petitions in all other respects.
    So ordered.
    ROGERS, Circuit Judge, concurring in part and dissenting in
    part. I join the court’s opinion regarding challenges to the Phase
    2 Rule1 except in three respects. The petitioners met their
    burden to show reopening of both the general policies allowing
    new and modified sources to use offset credits from past
    emission reductions to meet the requirements of section 173 of
    the Clean Air Act (“CAA”), 
    42 U.S.C. § 7503
    , and EPA’s
    authority to waive interim new source review (“NSR”)
    Appendix S permitting requirements, 40 C.F.R. pt. 51, app. S, §
    VI. Additionally, the challenge to the contingency measure
    element of the Clean Data Policy was not forfeited because
    comments submitted by the NRDC and other environmental
    groups put EPA on notice of the challenge, which EPA, in fact,
    addressed.
    I.
    The principles underlying the reopening doctrine are well-
    established. It is only their application that may obfuscate the
    reality of what an agency regulatory action entails. This is the
    situation here.
    Under the reopening doctrine, which is an exception to the
    statutory limits on the period for seeking judicial review of
    agency action, see Env. Defense v. EPA, 
    467 F.3d 1329
    , 1333
    (D.C. Cir. 2006), an issue is reopened when an agency implicitly
    or explicitly, see West Virginia v. EPA, 
    362 F.3d 861
    , 872 (D.C.
    1
    Final Rule To Implement the 8-Hour Ozone National
    Ambient Air Quality Standard—Phase 2; Final Rule to Implement
    Certain Aspects of the 1990 Amendments Relating to New Source
    Review and Prevention of Significant Deterioration as They Apply in
    Carbon Monoxide, Particulate Matter and Ozone NAAQS; Final Rule
    for Reformulated Gasoline, 
    70 Fed. Reg. 71,612
    , 71,677 (Nov. 29,
    2005) (“Phase 2 Rule”).
    2
    Cir. 2004), solicits comment on a preexisting regulation or
    “otherwise indicates its willingness to reconsider such a
    regulation by inviting and responding to comments,” Kennecott
    Utah Copper Corp. v. Dep’t of Interior, 
    88 F.3d 1191
    , 1213
    (D.C. Cir. 1996). The “entire context” must “demonstrate[] that
    the agency has undertaken a serious, substantive reconsideration
    of the [existing] rule.” P & V Enters. v. U.S. Army Corps of
    Eng’rs, 
    516 F.3d 1021
    , 1024 (D.C. Cir. 2008) (internal quotation
    marks omitted) (alteration in original). Also, when a new rule
    “increase[s] the significance” of preexisting regulations,
    Kennecott, 
    88 F.3d at 1216
    , and thus “significantly alters the
    stakes of judicial review,” the new rule “constructively reopens”
    the previously settled issue, 
    id. at 1227
    . Applying these
    principles demonstrates EPA reopened consideration of two
    subjects.
    A.
    Offset credits. The Phase 2 Rule allows new and modified
    sources to meet emissions offset requirements under CAA §
    173(c), 
    42 U.S.C. § 7503
    (c), by using credits from sources that
    shut down or curtailed operations as long ago as August 7, 1977.
    See 
    40 C.F.R. § 51.165
    (a)(3)(ii)(C)(1)(ii); Op. at 28-31.
    Contrary to the court’s suggestion, this court’s opinion in
    Kennecott makes clear that the fact that the “basic regulatory
    scheme remains unchanged,” Op. at 33, is not dispositive of
    whether an issue has been constructively reopened. See
    Kennecott, 
    88 F.3d at 1219
    . Analyzing the reopening doctrine
    at that level of generality begs the question. If “adding new
    terms to [an] old rule” can result in reopening, see 
    id.,
     then so
    can removing old terms from an old rule, at least where those
    old terms were an important part of the underlying regulatory
    scheme. Furthermore, Kennecott also makes clear that the
    question whether the stakes are “quantitatively different,” Op.
    at 34, does not turn on whether the petitioner or another failed
    to object to a different change earlier. See Kennecott, 
    88 F.3d at
                            3
    1226-27. Although a 1989 Rule made it easier to use pre-
    application offset credits, see Requirements for Implementation
    Plans, Air Quality New Source Review, Final Rule, 
    54 Fed. Reg. 27,286
    , 27,292 (June 28, 1989) (“1989 Rule”), the concomitant
    addition of the attainment demonstration requirement mitigated
    the impact of the change and may well have meant it was not
    “worth challenging,” Kennecott, 
    88 F.3d at 1227
    , the regime as
    a whole. However, once EPA eliminated the attainment
    demonstration requirement and failed to replace it with a
    comparable substitute, the need for a challenge by
    environmental groups such as the NRDC arose because EPA had
    “dramatically expanded authority to use [pre-application offset]
    credits,” NRDC Br. at 44. This change meant that “a major new
    pollution source [may] add substantial new emissions to a
    nonattainment area without any contemporaneous offsets, even
    when the state has no plan for meeting standards and no idea of
    what total reductions are needed to attain standards.” Id. at 45.
    Both EPA’s and the court’s analysis show that a
    constructive reopening occurred. See Op. at 34-36. In
    announcing the 1989 Rule, EPA stated that to comply with the
    reasonable further progress (“RFP”) requirement of CAA §
    173(a)(1)(A), 
    42 U.S.C. § 7503
    (a)(1)(A), the restriction on pre-
    application offset credit was “necessary both to assure RFP and
    to guarantee that a new source does not cause or contribute to a
    violation of the NAAQS,” 1989 Rule, 54 Fed. Reg. at 27,292.
    This evaluation by EPA supports the conclusion that
    environmental groups would have determined in 1989 that it
    was not worth challenging the regulatory scheme as significant
    limits remained in place. Once EPA removed this “necessary,”
    id., limitation “without adding any other safeguard to ensure that
    issuing a particular permit is consistent with section 173’s
    mandate that total reductions ‘represent . . . reasonable further
    progress,’” Op. at 36 (quoting CAA § 173(a)(1)(A), 
    42 U.S.C. § 7503
    (a)(1)(A)), the stakes of judicial review were significantly
    4
    altered. The court’s speculation today — that it “could have
    been ‘reasonably anticipated’ in 1989 that EPA might eliminate
    the attainment demonstration requirement,” Op. at 34 — proves
    too much. Given EPA’s evaluation in the 1989 Rule of the
    importance of restricting the availability of pre-application
    offset credits, environmental groups had no reason then to lodge
    a challenge based on the possibility that EPA might, perhaps, at
    some point in the future reverse course. Cf. S. Coast Air Quality
    Mgmt. Dist. v. EPA, 
    472 F.3d 882
    , 898 (D.C. Cir. 2006).
    Although the reopening doctrine may not apply if the change
    could have been “reasonably anticipated,” see Env. Defense, 
    467 F.3d at 1333
    , such a limit on the doctrine does not go so far as
    preventing review because a petitioner might have guessed EPA
    could later change its evaluation of what was necessary. Such
    an approach would render the constructive reopening precedents
    nugatory.
    On the merits, the NRDC persuasively contends that
    “EPA’s final rule . . . unlawfully permits total allowable
    emissions after the new source starts operating to be higher than
    emissions from existing sources before the new source applied
    for its permit.” NRDC Br. at 42-43. The Phase 2 Rule’s
    allowance of offset credit for pre-application shutdowns and
    curtailments is contrary to the plain text of the CAA and fails
    under Chevron step one. Chevron U.S.A. Inc. v. Natural Res.
    Def. Council, Inc., 
    467 U.S. 837
    , 842-43 (1984). Section
    173(a)(1)(A) requires that “sufficient offsetting reductions” shall
    be obtained “such that total allowable emissions from existing
    sources in the region, from new or modified sources which are
    not major emitting facilities, and from the proposed source will
    be sufficiently less than total emissions from existing sources .
    . . prior to the application for such permit to construct or modify
    so as to represent . . . reasonable further progress.” 
    42 U.S.C. § 7503
    (a)(1)(A). Section 173(c)(1) requires that offsets come
    from “an equal or greater reduction, as applicable, in actual
    5
    emissions of such air pollutant from the same or other sources in
    the area.” 
    Id.
     § 7503(c)(1) (emphasis added); see also H.R. Rep.
    No. 101-490, pt. 1 (1990) (referring to reductions in “actual
    emissions”). Under the Phase 2 Rule, new and modified major
    sources may claim offset credit from reductions in emissions
    resulting from the shutdown or curtailment of operations from
    more than three decades ago. The absence of any meaningful
    time limit means the Rule is inconsistent with CAA §
    173(c)(1)’s requirement that new sources’ emissions “shall be
    offset” by an equal or greater reduction in “actual emissions,” 
    42 U.S.C. § 7503
    (c)(1). Congress is presumed, absent any
    indication to the contrary, to have intended the ordinary meaning
    of the word “actual,” as “existing or occurring at the time,”
    MERRIAM WEBSTER’S COLLEGIATE DICTIONARY (10th ed. 1993)
    (emphasis added); accord WEBSTER’S THIRD NEW INT’L
    DICTIONARY (1993). See Engine Mfrs. Ass’n v. S. Coast Air
    Quality Mgmt. Dist., 
    541 U.S. 246
    , 252 (2004). Congress has
    given no indication in the surrounding text, or elsewhere, that it
    intended to depart from the common meaning of “actual.”
    Hence, allowing an offset for no-longer-existing emissions from
    sources closed decades ago is inconsistent with the statutory
    text.
    EPA offers that because the Phase 2 Rule requires the old
    offsets to be included in the area’s emissions inventory,
    allowance of pre-application offset credits is consistent with the
    requirement in CAA § 173(a)(1)(A), 
    42 U.S.C. § 7503
    (a)(1)(A),
    that offsets ensure reasonable further progress toward
    attainment. See Phase 2 of the Final Rule to Implement the 8-
    Hour Ozone National Ambient Air Quality Standard, Final
    Notice of Reconsideration, 
    72 Fed. Reg. 31,727
    , 31,742/3 (June
    8, 2007) (“Final Notice of Reconsideration”). But using
    decades-old emissions in an accounting exercise cannot render
    those emissions “actual” as that word is commonly understood.
    Likewise, EPA offers that because “[f]rom an air quality
    6
    planning perspective” emissions from the previously shutdown
    or curtailed sources had impacted the area’s designations as
    nonattainment, they are “actual emissions reductions.” Phase 2
    Rule, 70 Fed. Reg. at 71,677; see also Final Notice of
    Reconsideration, 72 Fed. Reg. at 31,742/3. But that emissions
    were “actual” as long ago as the 1970s does not mean they
    continue to meet the common understanding of “actual” years
    later when a source applies for a construction or modification
    permit.
    Because the flaws in this part of the Phase 2 Rule, see 
    40 C.F.R. § 51.165
    (a)(3)(ii)(C)(1)(ii), cannot be remedied by
    further explanation by EPA, it must be vacated. See Allied-
    Signal, Inc. v. U.S. Nuclear Reg. Comm’n, 
    988 F.2d 146
    , 150-51
    (D.C. Cir. 1993). To what extent the court’s holding that
    elimination of the requirement of an approved attainment
    demonstration is arbitrary and capricious under CAA §
    307(d)(9)(A), 
    42 U.S.C. § 7607
    (d)(9)(A), Op. at 36, will result
    in a different outcome than vacatur remains to be seen upon
    remand.
    B.
    NSR waiver authority. Section 110(a)(2)(C), 
    42 U.S.C. § 7410
    (a)(2)(C), does not specify what NSR requirements apply
    in the period between an area’s designation as nonattainment
    and approval of its NSR state implementation plan (“SIP”).
    Prior to promulgating the Phase 2 Rule, EPA had filled this
    statutory gap by retaining Appendix S’s interim NSR regime,
    which by its terms could apply for only 18 months. Given the
    limited duration of its effect, the previous regulation “may not
    have been worth challenging,” Kennecott, 88 F.3d at 1227.
    However, EPA’s decision to eliminate the 18-month limitation
    “alter[ed] the stakes of judicial review,” id. By parity of
    reasoning, if there was a reopening in Kennecott where industry
    petitioners faced a new requirement creating the possibility of
    7
    the imposition of additional penalties, then there was a
    constructive reopening where EPA’s change meant NSR
    controls could be postponed indefinitely, thereby dramatically
    changing the scope and effect of the waiver provision.
    Additionally, EPA constructively reopened the issue of its
    NSR waiver authority when it proposed to remove the general
    waiver provision in Appendix S and replace it with a
    “transitional” program in which waivers would be available in
    only a limited set of nonattainment areas. See Proposed Rule to
    Implement the 8-Hour Ozone National Ambient Air Quality
    Standard, 
    68 Fed. Reg. 32,802
    , 32,846-48 (June 2, 2003)
    (“NPRM”). EPA has described the proposal as a “major rewrite
    of [A]ppendix S.” Phase 2 Rule, 70 Fed. Reg. at 71,674. In
    explaining the 2003 proposal, EPA stated “we do not believe
    that areas not meeting the transitional approach would be able
    to ensure that they were implementing an NSR program ‘as
    necessary’ to ensure the attainment of NAAQS . . . .” NPRM,
    68 Fed. Reg. at 32,848 (quoting CAA § 110(a)(2)(C), 
    42 U.S.C. § 7410
    (a)(2)(C)). In other words, EPA expressed doubt about
    a broad waiver’s consistency with statutory mandates in certain
    circumstances. Although it ultimately rejected the proposed
    alternative, EPA reopened the issue of its authority to waive
    interim NSR requirements by raising the question whether a
    broad waiver would be inconsistent with the CAA. See Edison
    Elec. Inst. v. EPA, 
    996 F.2d 326
    , 332 (D.C. Cir. 1993).
    On the merits, the challenge by the NRDC and the State of
    New Jersey to EPA’s authority to exempt new sources from the
    interim NSR permitting requirements is unpersuasive. They
    contend that “[w]here Congress has intended to allow exceptions
    to NSR requirements, it has expressly said so,” NRDC Br. at 38
    (citing, inter alia, CAA § 173(a)(1)(B), 
    42 U.S.C. § 7503
    (a)(1)(B), excepting economic development zones).
    However, EPA persuasively responds that the waivers are the
    8
    product of EPA’s gap-filling authority. See Chevron, 
    467 U.S. at 843-45
    . In exercising that authority, EPA established
    requirements “substantially similar to the requirements of part
    D,” CAA § 171 et seq., 
    42 U.S.C. § 7501
     et seq., although not
    identical to the “major NSR” program under Part D. See Phase
    2 Rule, 70 Fed. Reg. at 71,678/1. The “minor NSR” program
    under CAA § 110(a)(2)(C) calls for “regulation of the
    modification and construction of any stationary source within
    the areas covered by the plan as necessary to assure that
    [NAAQS] are achieved.” 
    42 U.S.C. § 7410
    (a)(2)(C) (emphasis
    added). EPA thus could reasonably conclude that the interim
    NSR requirements are inapplicable when the exemption
    conditions are met. In those instances, a waiver would be
    available only if the new source’s emissions would not interfere
    with timely attainment, see 40 C.F.R. pt. 51, app. S, § VI,
    making additional NSR requirements unnecessary.
    Although EPA had authority to provide waivers on a case-
    by-case basis where a waiver would not interfere with timely
    attainment, I concur in holding that EPA’s elimination of the 18-
    month limitation violates the anti-backsliding provision in CAA
    § 172(e), 
    42 U.S.C. § 7502
    (e), see Op. at 43-45.
    II.
    The Clean Data Policy, originally published in 1992 and
    revised in 1995, excuses state planning requirements relating to
    RFP, attainment demonstrations, and contingency measures for
    areas attaining the NAAQS but not yet redesignated as
    attainment areas. In commenting in 2003 on the proposed
    codification of this statutory interpretation, environmental
    groups, including the NRDC, stated that the “EPA cannot
    authorize states to simply drop subpart 2 measures when the area
    is meeting either [the 1-hour or 8-hour] standard.” Clean Air
    Task Force, et al., Comments at 48. By arguing that “[t]he
    9
    [CAA] allows states to move mandated controls to a
    maintenance contingency plan, [CAA § 175A, 42 U.S.C.
    § 7505a], but only after the area has been redesignated to
    attainment,” id. (emphasis added), environmental groups put
    EPA on notice of its view that until an area is designated as
    being in attainment, a state plan must continue to contain the
    antecedent requirements, such as contingency measures,
    applicable in nonattainment areas.
    Contrary to the court’s holding that the NRDC’s challenge
    to the contingency plan aspect of EPA’s Clean Data Policy is
    forfeited, Op. at 20-21, the rulemaking record evidences that
    comments put EPA on notice of that objection. First, these
    comments raised the objection to the Clean Data Policy with
    respect to the contingency measures requirement of Subpart 2
    “with reasonable specificity during the period for public
    comment,” CAA § 307(d)(7)(B), 
    42 U.S.C. § 7607
    (d)(7)(B), and
    sufficiently put EPA on notice of the objection. Second, the
    comment did not make a mere “general [challenge] to EPA’s
    approach,” Mossville Envt’l Action Now v. EPA, 
    370 F.3d 1232
    ,
    1238 (D.C. Cir. 2004) (internal quotation marks omitted)
    (alteration in original), but instead challenged application of a
    specific EPA policy — the Clean Data Policy — to a specific set
    of statutory requirements — those in Subpart 2 of the CAA,
    CAA § 181 et seq., 
    42 U.S.C. § 7511
     et seq. The comment
    therefore constituted “adequate notification of the general
    substance of the complaint,” S. Coast Air Quality Mgmt. Dist. v.
    EPA, 
    472 F.3d 882
    , 891 (D.C. Cir. 2006), including an objection
    regarding antecedent contingency measures in particular. Third,
    that other objections to the Clean Data Policy addressed only the
    requirements for RFP and attainment demonstrations does not
    render the broader objection insufficient to preserve for judicial
    review the objection to elimination of the antecedent contingency
    measures. Fourth, the comment that the “EPA’s ‘clean data
    policy,’ 68 Fed. Reg. at 32,835/3, is unlawful with respect to
    10
    both the 1-hour and 8-hour NAAQS for the reasons set forth . .
    . above [regarding RFP and the attainment demonstration],”
    Clean Air Task Force, et al., Comments at 100, shows that the
    objection was not limited to any particular aspect of the Clean
    Data Policy. Fifth, EPA’s response to the comments addressed
    contingency measures, among other requirements, further
    indicating the comments were sufficient to put EPA on notice of
    the objection. See Phase 2 Rule, 70 Fed. Reg. at 71,645/1,
    71,646/1; cf. Appalachian Power Co. v. EPA, 
    135 F.3d 791
    , 817-
    18 (D.C. Cir. 1998).
    Nonetheless, although the NRDC’s challenge is properly
    before the court, it fails on the merits. Section 172(c)(9)
    provides that SIPs in nonattainment areas “shall provide for
    implementation of specific measures to be undertaken if the area
    fails to make reasonable further progress, or to attain the
    [NAAQS] by the attainment date applicable under this part.” 
    42 U.S.C. § 7502
    (c)(9) (emphasis added). The NRDC contends that
    “[t]he [Clean Data] [P]olicy waives mandatory pollution control
    requirements based solely on an area’s current air quality,
    without requiring the area to also show — as mandated by
    Congress — that it has met all of the [CAA]’s applicable
    requirements . . . .” NRDC Br. at 34. However, EPA’s view that
    CAA §§ 172(c)(9) and 182(c)(9), 
    42 U.S.C. §§ 7502
    (c)(9),
    7511a(c)(9), are written in a manner that ties the antecedent
    contingency measures to the requirements for RFP and an
    attainment demonstration, such that all are inapplicable upon
    attainment, see Phase 2 Rule, 70 Fed. Reg. at 71,645, is
    consistent with the plain text and to the extent there may be
    ambiguity, it is a reasonable interpretation. The Clean Data
    Policy requires that areas have “three consecutive years of clean
    air quality monitoring data demonstrating attainment of the
    ozone standard” before EPA can determine areas have attained.
    Memorandum from John S. Seitz, Director, Office of Air Quality
    Planning and Standards, EPA, to Various EPA Directors 5 (May
    11
    10, 1995). Also, if EPA determines an area covered by the Clean
    Data Policy has violated the NAAQS prior to formal designation
    of attainment, the Clean Data Policy no longer applies to that
    area. See 
    40 C.F.R. § 51.918
    .