Upper Missouri Waterkeeper v. Usepa ( 2021 )


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  •                    FOR PUBLICATION
    UNITED STATES COURT OF APPEALS
    FOR THE NINTH CIRCUIT
    UPPER MISSOURI WATERKEEPER,                  No. 19-35898
    Plaintiff-Appellee,
    D.C. No.
    v.                       4:16-cv-00052-
    BMM
    U.S. ENVIRONMENTAL PROTECTION
    AGENCY; MICHAEL REGAN, *
    Administrator, United States
    Environmental Protection Agency,
    Defendants,
    TREASURE STATE RESOURCES
    ASSOCIATION OF MONTANA; STATE
    OF MONTANA DEPARTMENT OF
    ENVIRONMENTAL QUALITY,
    Intervenor-Defendants,
    and
    NATIONAL ASSOCIATION OF CLEAN
    WATER AGENCIES; THE MONTANA
    LEAGUE OF CITIES AND TOWNS,
    Intervenor-Defendants-Appellants.
    *
    Michael Regan has been automatically substituted for former
    Administrator Andrew Wheeler. Fed. R. App. P. 43(c)(2).
    2     UPPER MISSOURI WATERKEEPER V. USEPA
    UPPER MISSOURI WATERKEEPER,            No. 19-35899
    Plaintiff-Appellee,
    D.C. No.
    v.                    4:16-cv-00052-
    BMM
    U.S. ENVIRONMENTAL PROTECTION
    AGENCY; MICHAEL REGAN,
    Administrator, United States
    Environmental Protection Agency,
    Defendants,
    NATIONAL ASSOCIATION OF CLEAN
    WATER AGENCIES; THE MONTANA
    LEAGUE OF CITIES AND TOWNS;
    STATE OF MONTANA DEPARTMENT
    OF ENVIRONMENTAL QUALITY,
    Intervenor-Defendants,
    and
    TREASURE STATE RESOURCES
    ASSOCIATION OF MONTANA,
    Intervenor-Defendant-Appellant.
    UPPER MISSOURI WATERKEEPER V. USEPA               3
    UPPER MISSOURI WATERKEEPER,            No. 20-35135
    Plaintiff-Appellee,
    D.C. No.
    v.                    4:16-cv-00052-
    BMM
    U.S. ENVIRONMENTAL PROTECTION
    AGENCY; MICHAEL REGAN,
    Administrator, United States
    Environmental Protection Agency,
    Defendants,
    NATIONAL ASSOCIATION OF CLEAN
    WATER AGENCIES; THE MONTANA
    LEAGUE OF CITIES AND TOWNS;
    TREASURE STATE RESOURCES
    ASSOCIATION OF MONTANA,
    Intervenor-Defendants,
    and
    STATE OF MONTANA DEPARTMENT
    OF ENVIRONMENTAL QUALITY,
    Intervenor-Defendant-Appellant.
    4     UPPER MISSOURI WATERKEEPER V. USEPA
    UPPER MISSOURI WATERKEEPER,           No. 20-35136
    Plaintiff-Appellee,
    D.C. No.
    v.                    4:16-cv-00052-
    BMM
    U.S. ENVIRONMENTAL PROTECTION
    AGENCY; MICHAEL REGAN,
    Administrator, United States
    Environmental Protection Agency,
    Defendants-Appellants,
    and
    NATIONAL ASSOCIATION OF CLEAN
    WATER AGENCIES; THE MONTANA
    LEAGUE OF CITIES AND TOWNS;
    TREASURE STATE RESOURCES
    ASSOCIATION OF MONTANA; STATE
    OF MONTANA DEPARTMENT OF
    ENVIRONMENTAL QUALITY,
    Intervenor-Defendants.
    UPPER MISSOURI WATERKEEPER V. USEPA                 5
    UPPER MISSOURI WATERKEEPER,              No. 20-35137
    Plaintiff-Appellant,
    D.C. No.
    v.                       4:16-cv-00052-
    BMM
    U.S. ENVIRONMENTAL PROTECTION
    AGENCY; MICHAEL REGAN,
    Administrator, United States               OPINION
    Environmental Protection Agency,
    Defendants-Appellees,
    NATIONAL ASSOCIATION OF CLEAN
    WATER AGENCIES; THE MONTANA
    LEAGUE OF CITIES AND TOWNS;
    TREASURE STATE RESOURCES
    ASSOCIATION OF MONTANA; STATE
    OF MONTANA DEPARTMENT OF
    ENVIRONMENTAL QUALITY,
    Intervenor-Defendants-Appellees.
    Appeals from the United States District Court
    for the District of Montana
    Brian M. Morris, Chief District Judge, Presiding
    Argued and Submitted March 4, 2021
    Portland, Oregon
    Filed October 6, 2021
    6          UPPER MISSOURI WATERKEEPER V. USEPA
    Before: Danny J. Boggs, ** Richard A. Paez, and
    Paul J. Watford, Circuit Judges.
    Opinion by Judge Watford
    SUMMARY ***
    Clean Water Act
    The panel reversed the portion of the district court’s
    summary judgment order challenged in Nos. 19-35898, 19-
    35899, 20-35135, and 20-35136, and affirmed the portion of
    the summary judgment order challenged in No. 20-35137, in
    actions challenging the U.S. Environmental Protection
    Agency’s approval of Montana’s variance request from
    approved water quality standards that were adopted under
    the Clean Water Act.
    The Clean Water Act requires States to adopt water
    quality standards regulating pollutants in their navigable
    waters. The standards consist of two components: (1) the
    designated uses for the water body, such as supporting
    aquatic life or recreational use; and (2) the “water quality
    criteria” necessary to protect those uses. 
    33 U.S.C. § 1313
    (c)(2)(A); 
    40 C.F.R. §§ 131.3
    (b), 131.11(a). States
    submit proposed water quality standards to the EPA for
    review and approval.
    **
    The Honorable Danny J. Boggs, United States Circuit Judge for
    the U.S. Court of Appeals for the Sixth Circuit, sitting by designation.
    ***
    This summary constitutes no part of the opinion of the court. It
    has been prepared by court staff for the convenience of the reader.
    UPPER MISSOURI WATERKEEPER V. USEPA                  7
    The EPA approved Montana’s water quality standards in
    2015. In 2017, Montana sought, and obtained, EPA’s
    approval of a variance in the water quality standard, which
    covered 36 municipal wastewater treatment facilities for a
    term of up to 17 years. The variance allowed those facilities
    to discharge more nitrogen and phosphorus into wadeable
    streams than would be permitted under the base water
    standards approved in 2015. Plaintiff Upper Missouri
    Waterkeeper contended that the EPA approval of the
    variance violated the Administrative Procedure Act. The
    district court granted partial vacatur of the EPA’s approval
    of the variance, and stayed its decision pending resolution of
    the appeals.
    First, the panel considered Waterkeeper’s cross-appeal,
    which contended that a provision of the Clean Water Act,
    
    33 U.S.C. § 1313
    (c)(2)(A), precluded the EPA from taking
    compliance costs into account when approving the variance
    requests. Applying Chevron analysis, the panel held at step
    one, that Congress had not directly spoken to the precise
    question at issue. Section 1313(c)(2)(A) does not speak at
    all to whether the EPA may consider compliance costs when
    approving a State’s proposed water quality standards or, by
    extension, when approving a State’s variance request. At
    step two, the panel held that the EPA reasonably construed
    § 1313(c)(2)(A) as permitting it to consider compliance costs
    when approving water quality standards and variance
    requests. The panel concluded that the EPA’s regulations
    reasonably interpreted the Clean Water Act as allowing
    consideration of compliance costs when the agency approves
    water quality standards and variance requests.
    Next, the panel turned to the EPA’s appeal, which
    challenged the district court’s partial vacatur of the agency’s
    decision approving Montana’s variance request. The district
    8       UPPER MISSOURI WATERKEEPER V. USEPA
    court held that the variance’s term of up to 17 years was
    invalid because it did not require compliance with the
    highest attainable condition at the outset of the term, and did
    not require compliance with Montana’s base quality water
    standards by the end of the term. The panel disagreed, and
    held that the EPA’s variance regulation unambiguously
    provided that compliance with the highest attainable
    condition was not required at the outset. The district court
    did not identify any provision in the EPA’s variance
    regulation supporting its view that the variance must require
    compliance with the base water quality standards by the end
    of the variance’s term. As reflected in the variance at issue
    here, the EPA’s regulations included numerous features to
    ensure that dischargers and waterbodies subject to variances
    continued to improve water quality. The panel concluded
    that the regulatory framework was consistent with the goals
    of the Clean Water Act, which as reasonably construed by
    the EPA, included supporting aquatic life and recreational
    uses whenever attainable.
    The panel remanded to the district court with instructions
    to deny Waterkeeper’s motion for summary judgment and to
    grant the EPA’s and intervenor-defendants’ motion for
    summary judgment in full.
    COUNSEL
    Janette K. Brimmer (argued), Earthjustice, Seattle,
    Washington, for Plaintiff-Appellee/Cross-Appellant.
    John L. Smeltzer (argued), David Gunter, and Alan D.
    Greenberg, Attorneys; Eric Grant, Deputy Assistant
    Attorney General; Jonathan D. Brightbill, Principal Deputy
    Assistant Attorney General; Environment and Natural
    UPPER MISSOURI WATERKEEPER V. USEPA              9
    Resources Division, United States Department of Justice,
    Washington, D.C.; David Fatouhi, Peter Z. Ford, Heidi
    Nalven, and Diane McConkey, Office of General Counsel,
    United States Environmental Protection Agency; Erin
    Perkins and Elyana Sutin, Office of Regional Counsel,
    United States Environmental Protection Agency; for
    Defendants-Appellants/Cross-Appellees United States
    Environment Protection Agency and Michael Regan.
    Kurt R. Moser (argued), Special Assistant Attorney General,
    State of Montana Department of Environmental Quality,
    Helena,     Montana,        for      Intervenor-Defendant-
    Appellant/Cross-Appellee State of Montana Department of
    Environmental Quality.
    Fredric P. Andes and Ashley E. Parr, Barnes & Thornburg
    LLP, Chicago, Illinois; Paul M. Drucker, Barnes &
    Thornburg LLP, Indianapolis, Indiana; Catherine A.
    Laughner, Chad E. Adams, and M. Christy S. McCann,
    Browning Kaleczyc Berry & Hoven P.C., Bozeman,
    Montana;     for   Intervenor-Defendant-Appellant/Cross-
    Appellee National Association of Clean Water Agencies and
    Montana League of Cities and Towns.
    Mark L. Stermitz and Jeffery J. Oven, Crowley Fleck PLLP,
    Billings,    Montana,       for      Intervenor-Defendant-
    Appellant/Cross-Appellee Treasure State Resources
    Association of Montana.
    10      UPPER MISSOURI WATERKEEPER V. USEPA
    OPINION
    WATFORD, Circuit Judge:
    Congress enacted the Clean Water Act “to restore and
    maintain the chemical, physical, and biological integrity of
    the Nation’s waters.” 
    33 U.S.C. § 1251
    (a). In furtherance
    of that objective, the Act requires States to adopt water
    quality standards regulating pollutants in their navigable
    waters. Water quality standards consist of two components:
    (1) the “designated uses” for the water body in question,
    such as supporting aquatic life or recreational use; and
    (2) the “water quality criteria” necessary to protect those
    uses, usually specified as the maximum concentration of a
    pollutant that may be present in the water. § 1313(c)(2)(A);
    
    40 C.F.R. §§ 131.3
    (b), 131.11(a). States must submit
    proposed water quality standards to the Environmental
    Protection Agency (EPA) for review and approval.
    
    33 U.S.C. § 1313
    (c).       Once approved, water quality
    standards are used to set effluent limits in the permits that
    individual dischargers must obtain in order to discharge
    pollutants from a point source into waters covered by the
    Act. 
    40 C.F.R. § 122.44
    (d)(1); see 
    33 U.S.C. § 1342
    .
    In 2014, the State of Montana adopted water quality
    standards governing two pollutants, nitrogen and
    phosphorus, in its “wadeable streams.” Montana assigned
    designated uses for wadeable streams that include the
    support of aquatic life and recreation, and to protect those
    uses it specified the maximum permissible concentrations of
    nitrogen and phosphorus. The EPA approved Montana’s
    water quality standards in 2015.
    Under regulations issued by the EPA, States may obtain
    a variance from approved water quality standards (known as
    the “base” water quality standards) if compliance with such
    UPPER MISSOURI WATERKEEPER V. USEPA                11
    standards is shown to be infeasible. See 
    40 C.F.R. § 131.14
    .
    A variance is a narrow, time-limited exemption from the
    base water quality standards, applicable to specific
    pollutants and to specific dischargers or a particular water
    body. §§ 131.3(o), 131.14(a). The EPA may approve a
    variance when the State demonstrates that compliance with
    the base water quality standards is not feasible for one of
    several specified reasons. §§ 131.14(b)(2)(i)(A), 131.10(g).
    One of those reasons, and the reason relevant in this case, is
    that implementing the pollution controls necessary to attain
    compliance with the base water quality standards “would
    result in substantial and widespread economic and social
    impact.” § 131.10(g)(6).
    To be approved, a variance must set interim limits that,
    although less stringent than those imposed by the base water
    quality standards, nonetheless “represent the highest
    attainable condition of the water body or waterbody segment
    applicable throughout the term of the [water quality
    standards] variance.” § 131.14(b)(1)(ii). The term of a
    variance may last “only . . . as long as necessary to achieve
    the highest attainable condition.” § 131.14(b)(1)(iv).
    In 2017, Montana sought EPA approval of the variance
    at issue in this appeal, which covers 36 municipal
    wastewater treatment facilities for a term of up to 17 years.
    The variance allows those facilities to discharge more
    nitrogen and phosphorus into wadeable streams than would
    be permitted under the base water quality standards
    approved in 2015. In support of the proposed variance,
    Montana submitted evidence demonstrating that these
    36 facilities could not attain compliance with the base water
    quality standards unless they adopted reverse osmosis
    technology, and that the high cost of adopting such
    technology would result in substantial and widespread
    12      UPPER MISSOURI WATERKEEPER V. USEPA
    economic and       social   impact   on   the   surrounding
    communities.
    After reviewing Montana’s evidence and conducting its
    own analysis, the EPA approved the variance. The EPA
    agreed with Montana’s assessment that (1) implementing
    reverse osmosis technology would be necessary to attain
    compliance with the base water quality standards, and (2) the
    cost of implementing such technology would result in
    substantial and widespread economic and social impact on
    the communities served by the 36 municipal wastewater
    treatment facilities. In reaching that conclusion, the EPA
    relied on economic guidance that it had previously issued,
    which provides that an average annual cost per household
    exceeding 2% of median household income in the affected
    community constitutes a substantial economic impact. The
    EPA’s analysis confirmed that costs of that magnitude would
    indeed be imposed on each of the affected communities. The
    EPA also determined that the interim limits imposed by the
    variance represented the highest attainable condition for all
    36 facilities, and that the variance’s term of up to 17 years
    would last only “as long as necessary to achieve the highest
    attainable condition.” 
    40 C.F.R. § 131.14
    (b)(1)(iv), (2)(ii).
    In this action, plaintiff Upper Missouri Waterkeeper
    (Waterkeeper) does not challenge any of the EPA’s factual
    determinations. It instead contends that the EPA’s approval
    of Montana’s variance request violates the Administrative
    Procedure Act because it is “not in accordance with law.”
    
    5 U.S.C. § 706
    (2)(A). Specifically, Waterkeeper argues that
    the Clean Water Act prohibits the EPA from considering
    compliance costs when granting variance requests.
    On cross-motions for summary judgment, the district
    court rejected Waterkeeper’s argument.        The court
    concluded that the EPA has reasonably construed the Clean
    UPPER MISSOURI WATERKEEPER V. USEPA                 13
    Water Act as permitting it to grant variances based on the
    economic impact that would be caused by requiring
    compliance with the base water quality standards. The court
    nevertheless held that the EPA’s approval of the variance’s
    term of up to 17 years was arbitrary and capricious because
    it does not require compliance with the highest attainable
    condition at the beginning of the variance term and does not
    require compliance with Montana’s base water quality
    standards by the end of the term. The court granted partial
    vacatur of the EPA’s approval of the variance and stayed its
    decision pending resolution of these appeals.
    On appeal, Waterkeeper urges us to reverse the district
    court’s rejection of its Administrative Procedure Act
    challenge to the EPA’s approval decision, while the EPA and
    the intervenor-defendants (the Montana Department of
    Environmental Quality, Treasure State Resources
    Association of Montana, Montana League of Cities and
    Towns, and National Association of Clean Water Agencies)
    urge us to reverse the district court’s partial vacatur of that
    decision. We affirm in part, reverse in part, and remand with
    instructions to enter judgment in favor of the EPA and the
    intervenor-defendants.
    I
    We take up Waterkeeper’s cross-appeal first. It contends
    that the following provision of the Clean Water Act
    precludes the EPA from taking compliance costs into
    account when approving variance requests:
    Whenever the State revises or adopts a new
    standard, such revised or new standard shall
    be submitted to the Administrator. Such
    revised or new water quality standard shall
    consist of the designated uses of the
    14      UPPER MISSOURI WATERKEEPER V. USEPA
    navigable waters involved and the water
    quality criteria for such waters based upon
    such uses. Such standards shall be such as to
    protect the public health or welfare, enhance
    the quality of water and serve the purposes of
    this chapter.     Such standards shall be
    established taking into consideration their use
    and value for public water supplies,
    propagation of fish and wildlife, recreational
    purposes, and agricultural, industrial, and
    other purposes, and also taking into
    consideration their use and value for
    navigation.
    
    33 U.S.C. § 1313
    (c)(2)(A). This provision addresses the
    establishment of water quality standards, not the granting of
    variances, and thus appears at first blush to be of limited
    relevance to Waterkeeper’s argument. Water quality
    standards and variances, however, are closely linked in the
    regulatory framework created by the EPA after the Clean
    Water Act’s passage. A bit more background on that
    framework is necessary before proceeding.
    The EPA has interpreted § 1313(c)(2)(A) as authorizing
    States to consider compliance costs when they first adopt
    water quality standards. In enforcing that provision’s
    directive that water quality standards “serve the purposes of
    this chapter,” the EPA has looked to the opening provision
    of the Clean Water Act, § 101, codified at 
    33 U.S.C. § 1251
    ,
    to identify those purposes. Section 1251(a)(2) of the Act
    declares that “it is the national goal that wherever attainable,
    an interim goal of water quality which provides for the
    protection and propagation of fish, shellfish, and wildlife and
    provides for recreation in and on the water be achieved by
    July 1, 1983.” 
    33 U.S.C. § 1251
    (a)(2) (emphasis added).
    UPPER MISSOURI WATERKEEPER V. USEPA                        15
    Although the deadline set by this provision has passed, the
    EPA has reasonably construed § 1251(a)(2) as an ongoing
    expression of Congress’s intent that the stated goal be
    achieved (albeit much later than hoped for) whenever the
    specified uses are “attainable.” See 
    40 C.F.R. § 131.2
    .
    The EPA’s regulations require States to adopt water
    quality standards that protect the uses described in
    § 1251(a)(2) unless the State can show through a “use
    attainability analysis” that attaining the water quality
    necessary to support those uses is not feasible for any one of
    the several reasons referenced earlier. See 
    40 C.F.R. § 131.10
    (g), (j); Water Quality Standards Regulatory
    Clarifications, 
    78 Fed. Reg. 54,518
    , 54,522–23 (Sept. 4,
    2013). Thus, a State may adopt a water quality standard that
    does not designate the uses described in § 1251(a)(2) if it can
    show that implementing the pollution controls necessary to
    protect those uses “would result in substantial and
    widespread economic and social impact.” 
    40 C.F.R. § 131.10
    (g)(6). Economic impact, of course, involves
    consideration of the costs that would be imposed on the
    affected stakeholders. 1
    The EPA adopted its variance regulation by building on
    this same framework. The agency recognized that States
    could decline to designate a use in the first instance (or
    1
    The EPA’s regulations make clear that compliance costs may be
    considered only when designating the uses to be protected by water
    quality standards. Once those uses have been designated, States must
    adopt water quality criteria adequate to protect those uses, “based on
    sound scientific rationale.” 
    40 C.F.R. § 131.11
    (a)(1); see Mississippi
    Commission on Natural Resources v. Costle, 
    625 F.2d 1269
    , 1277 (5th
    Cir. 1980). A variance does not modify the water quality criteria alone.
    A variance is instead a time-limited modification of both the “designated
    use and criterion.” 
    40 C.F.R. § 131.3
    (o).
    16      UPPER MISSOURI WATERKEEPER V. USEPA
    remove a previously designated use) by conducting a use
    attainability analysis and making the required showing that
    attainment of such a use is not feasible. If approved, that
    action would remove the designated use and associated
    water quality criteria from the water quality standard as
    applied to all dischargers and all pollutants.
    In light of this reality, the EPA concluded that variances
    “are an environmentally preferable tool over a designated
    use change because variances retain designated use
    protection for all pollutants as they apply to all sources with
    the exception of those specified in the variance.” 78 Fed.
    Reg. at 54,531. The variance procedure thus affords States
    a more targeted option when compliance with a water quality
    standard is unattainable only for certain dischargers or only
    with respect to certain pollutants. The variance regulation
    requires States to make the same showing required by a use
    attainability analysis, just one that is limited in scope to the
    specific dischargers and pollutants covered by the variance.
    Waterkeeper recognizes this link between water quality
    standards and variances.         Its contention under the
    Administrative Procedure Act is that the provision quoted at
    the outset, 
    33 U.S.C. § 1313
    (c)(2)(A), precludes the EPA
    from taking compliance costs into account when approving
    either water quality standards or variances. In assessing this
    contention, we employ the two-step framework established
    in Chevron U.S.A. Inc. v. Natural Resources Defense
    Council, Inc., 
    467 U.S. 837
     (1984).
    At step one, we ask whether “Congress has directly
    spoken to the precise question at issue.” 
    Id. at 842
    . The
    answer here is no. Section 1313(c)(2)(A) does not speak at
    all to whether the EPA may consider compliance costs when
    approving a State’s proposed water quality standards or, by
    extension, when approving a State’s variance request. The
    UPPER MISSOURI WATERKEEPER V. USEPA                  17
    provision is silent on the precise question at issue, but if
    anything, its reference to protecting the “public health or
    welfare” favors the EPA’s interpretation. 
    33 U.S.C. § 1313
    (c)(2)(A) (emphasis added). The concept of the
    public welfare is broad enough to encompass a regulatory
    program’s impact on the economic welfare of a community,
    and an assessment of that impact requires consideration of
    costs.
    It is true, as Waterkeeper argues, that § 1313(c)(2)(A)
    includes a list of uses and values that States must “tak[e] into
    consideration” when establishing water quality standards,
    without expressly mentioning the costs of compliance. But
    the inference that Waterkeeper asks us to draw—that
    Congress’s silence as to costs reflects an intention to forbid
    their consideration—is not supported by the text of the
    provision or the broader statutory context. Requiring States
    to formulate water quality standards by “taking into
    consideration” various uses and values does not tell us
    anything about whether Congress intended to mandate
    compliance with water quality standards regardless of how
    exorbitant the cost might prove to be. And nothing in the
    other provisions of the Clean Water Act suggests that
    Congress’s silence as to costs in § 1313(c)(2)(A) should be
    accorded special weight, as was true of the statutory
    provision at issue in Whitman v. American Trucking
    Associations, Inc., 
    531 U.S. 457
     (2001), the principal case
    on which Waterkeeper relies.
    In American Trucking, certain provisions of the Clean
    Air Act “explicitly permitted or required economic costs to
    be taken into account in implementing the air quality
    standards,” whereas the provision under review in that case
    did not, leading to the conclusion that Congress’s silence
    was intended to foreclose consideration of costs. 
    Id. at 467
    .
    18      UPPER MISSOURI WATERKEEPER V. USEPA
    The same cannot be said of the portion of the Clean Water
    Act we are reviewing, which precludes us from drawing the
    inference Waterkeeper urges about the supposed import of
    Congress’s silence as to costs in § 1313(c)(2)(A). Rather, as
    in Entergy Corp. v. Riverkeeper, Inc., 
    556 U.S. 208
     (2009),
    we think Congress’s silence as to costs in § 1313(c)(2)(A)
    can be understood “to convey nothing more than a refusal to
    tie the agency’s hands as to whether cost-benefit analysis
    should be used, and if so to what degree.” Id. at 222
    (interpreting § 316(b) of the Clean Water Act, codified at
    
    33 U.S.C. § 1326
    (b)).
    Having concluded that the statute is silent or ambiguous
    as to the precise question raised, we ask at step two of the
    Chevron analysis whether “the agency’s answer is based on
    a permissible construction of the statute.” Chevron,
    
    467 U.S. at 843
    . For two reasons, both alluded to above, we
    think the EPA has reasonably construed § 1313(c)(2)(A) as
    permitting it to consider compliance costs when approving
    water quality standards and variance requests.
    First, the provision states that water quality standards
    shall protect the “public . . . welfare,” and that term can
    reasonably be understood to encompass consideration of
    whether compliance costs would cause substantial and
    widespread economic and social impact. And second, the
    EPA has reasonably construed § 1313(c)(2)(A)’s
    requirement that water quality standards “serve the purposes
    of this chapter” as incorporating the purposes referred to in
    
    33 U.S.C. § 1251
    (a)(2). Congress declared in § 1251(a)(2)
    that water quality necessary to protect aquatic life and
    recreational use is to be achieved “wherever attainable.” The
    statute does not define what factors may be taken into
    account when deciding whether a particular use is
    “attainable,” so it fell to the EPA to flesh out the meaning of
    UPPER MISSOURI WATERKEEPER V. USEPA                 19
    that term. The agency could perhaps have interpreted the
    term to focus solely on whether achieving water quality of a
    particular level is technologically feasible, even if the costs
    involved would prove financially ruinous to the
    communities benefitting from the improvements. But it
    seems far more plausible that Congress used the term in the
    sense reflected in the EPA’s regulations—as including an
    assessment of whether achieving the necessary water quality
    is economically feasible, given the costs that would be
    imposed on the affected communities.
    We thus conclude that the EPA’s regulations reasonably
    interpret the Clean Water Act as allowing consideration of
    compliance costs when the agency approves water quality
    standards and variance requests.
    II
    We turn now to the EPA’s appeal, which challenges the
    district court’s partial vacatur of the agency’s decision
    approving Montana’s variance request. The court held that
    the variance’s term of up to 17 years is invalid because it
    (1) does not require compliance with the highest attainable
    condition at the outset of the term, and (2) does not require
    compliance with Montana’s base water quality standards by
    the end of the term. The district court believed these
    requirements were imposed by the EPA’s own variance
    regulation, but the plain language of the regulation
    unambiguously provides otherwise. We therefore have no
    need to decide whether the EPA’s interpretation of its
    regulation is entitled to deference under Kisor v. Wilkie,
    
    139 S. Ct. 2400
     (2019).
    20      UPPER MISSOURI WATERKEEPER V. USEPA
    A
    In ruling that compliance with the highest attainable
    condition must be achieved at the outset of a variance’s term,
    the district court relied on the EPA’s definition of a variance.
    The regulation defines the term “water quality standards
    variance” as a “time-limited designated use and criterion for
    a specific pollutant(s) or water quality parameter(s) that
    reflect the highest attainable condition during the term of the
    [water quality standards] variance.” 
    40 C.F.R. § 131.3
    (o)
    (emphasis added). The court concluded that the phrase
    “during the term” requires compliance with the highest
    attainable condition at the beginning of the variance’s term.
    On appeal, in defending the district court’s ruling,
    Waterkeeper points to another provision of the regulation,
    which states that the interim limits imposed by the variance
    must represent “the highest attainable condition of the water
    body or waterbody segment applicable throughout the term
    of the [water quality standards] variance.” § 131.14(b)(1)(ii)
    (emphasis added). Waterkeeper contends that the phrase
    “throughout the term” has the same meaning as the phrase
    “during the term” in § 131.3(o), and that both require
    compliance with the highest attainable condition at the very
    outset of the term.
    We do not think either phrase can fairly be read in the
    manner that the district court and Waterkeeper suggest. To
    be sure, both of the cited provisions provide that the highest
    attainable condition specified in the variance shall apply
    throughout (or during) the variance’s term, from the
    beginning of the term to the end. But those provisions do
    not state that an individual discharger must be in compliance
    with the highest attainable condition on day one.
    Instead, the EPA’s variance regulation unambiguously
    provides that compliance with the highest attainable
    UPPER MISSOURI WATERKEEPER V. USEPA                  21
    condition is not required at the outset. A variance request
    may be approved only when a State can show that
    compliance with the base water quality standards cannot
    feasibly be attained. § 131.14(b)(2)(i)(A). If approved, the
    variance replaces the base water quality standard with the
    most rigorous standard that can feasibly be attained—the
    “highest attainable condition.” § 131.14(b)(1)(ii). The
    regulation then provides that a variance may remain in effect
    only “as long as necessary to achieve the highest attainable
    condition.” § 131.14(b)(1)(iv) (emphasis added). That
    provision makes clear that the purpose of a variance is to
    provide the time needed to achieve this attainable interim
    standard, which means, of course, that compliance with the
    highest attainable condition is required by the end of the
    variance’s term, not at the beginning.
    B
    The district court did not identify any provision in the
    EPA’s variance regulation supporting its view that a
    variance must require compliance with the base water
    quality standards by the end of the variance’s term. We have
    found nothing in the regulation to support that view either.
    As just noted, the regulation explicitly states that the term of
    the variance may last only as long as necessary to achieve
    compliance with the highest attainable condition—not with
    the base water quality standards.                  
    40 C.F.R. § 131.14
    (b)(1)(iv). As this provision reflects, the purpose of
    a variance is to make incremental progress toward
    compliance with the base water quality standards, but the
    ultimate goal by the end of the variance’s term is to achieve
    compliance with the highest attainable condition. Indeed, if
    compliance with the base water quality standards were
    feasible within a reasonably foreseeable timeframe—say, by
    the end of the variance’s term—there would be no basis for
    22      UPPER MISSOURI WATERKEEPER V. USEPA
    granting a variance in the first place. When attainment of
    the base water quality standards is feasible within a
    reasonably foreseeable timeframe, a State may instead use a
    permit compliance schedule to set a specific deadline by
    which compliance with the base water quality standards will
    be achieved. § 122.47; see Water Quality Standards
    Regulatory Revisions, 
    80 Fed. Reg. 51,020
    , 51,039–40
    (Aug. 21, 2015).
    In defense of the district court’s ruling, Waterkeeper
    contends that unless a variance requires compliance with the
    base water quality standards by the end of the term, States
    would be free to postpone compliance with the base
    standards indefinitely simply by securing one variance after
    another, in conflict with the goals of the Clean Water Act.
    That contention reflects a misunderstanding of the nature
    and purpose of a variance. A variance may be granted only
    when compliance with the base water quality standards is not
    feasible for one of the reasons specified in the EPA’s
    regulations. To be approved, the variance must require
    compliance with the highest attainable condition that is
    feasible, and the variance may last only as long as necessary
    to achieve compliance with the highest attainable condition.
    If at the end of the variance’s term compliance with the base
    water quality standards has become feasible, another
    variance may not be granted. And, to obtain another
    variance, the State must submit an application subject to the
    same degree of EPA scrutiny and public participation as was
    the application for the initial variance. In the interim, while
    compliance with the base water quality standards remains
    unattainable, the variance’s requirements ensure that
    incremental progress toward attainment of the base
    standards is being made.
    UPPER MISSOURI WATERKEEPER V. USEPA                  23
    The variance at issue here reflects these safeguards. In
    accordance with the regulation, the variance states:
    “Through the permitting process and the specific details of
    each facility, the time required must be as short as possible
    to meet the highest attainable condition.” This period may
    be “up to 17 years,” but the period permitted for an
    individual facility carefully tracks the steps the facility must
    take to achieve compliance with the highest attainable
    condition. If a facility reaches the highest attainable
    condition but still cannot attain compliance with the base
    water quality standards, the facility must implement a
    “pollutant minimization program”—that is, “a structured set
    of activities to improve processes and pollutant controls”—
    as detailed in the variance. The variance is also subject to
    close review every three years. Thus, as reflected in the
    variance at issue here, the EPA’s regulations include
    numerous features to ensure that dischargers and
    waterbodies subject to variances continue to improve water
    quality.
    The regulatory framework discussed above is fully
    consistent with the goals of the Clean Water Act, which, as
    reasonably construed by the EPA, include supporting
    aquatic life and recreational uses “wherever attainable.”
    
    33 U.S.C. § 1251
    (a)(2).
    *       *       *
    We reverse the portion of the district court’s summary
    judgment order challenged in Nos. 19-35898, 19-35899, 20-
    35135, and 20-35136, and affirm the portion of the summary
    judgment order challenged in No. 20-35137. We remand to
    the district court with instructions to deny Waterkeeper’s
    motion for summary judgment and to grant the EPA’s and
    24       UPPER MISSOURI WATERKEEPER V. USEPA
    intervenor-defendants’ motions for summary judgment in
    full.
    AFFIRMED in part, REVERSED in part, and
    REMANDED with instructions.
    The parties shall bear their own costs on appeal.