United States v. Ameren Missouri ( 2021 )


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  •              United States Court of Appeals
    For the Eighth Circuit
    ___________________________
    No. 19-3220
    ___________________________
    United States of America
    lllllllllllllllllllllPlaintiff - Appellee
    Sierra Club
    lllllllllllllllllllllIntervenor - Appellee
    v.
    Ameren Missouri
    lllllllllllllllllllllDefendant - Appellant
    ------------------------------
    Chamber of Commerce of the United States of America; American Chemistry
    Council; America's Power; Missouri Chamber of Commerce and Industry;
    National Association of Manufacturers; National Mining Association
    lllllllllllllllllllllAmici on Behalf of Appellant(s)
    ____________
    Appeal from United States District Court
    for the Eastern District of Missouri - St. Louis
    ____________
    Submitted: December 16, 2020
    Filed: August 20, 2021
    ____________
    Before SMITH, Chief Judge, LOKEN and MELLOY, Circuit Judges.
    ____________
    SMITH, Chief Judge.
    Ameren Missouri (“Ameren”) appeals an adverse judgment of the district court
    in a Clean Air Act (CAA) enforcement action brought by the United States of
    America, acting at the request of the Administrator of the United States
    Environmental Protection Agency (EPA) (hereinafter, EPA or “government”).
    Ameren argues that the district court erroneously found it liable for not obtaining
    permits for projects at its Rush Island Energy Center (“Rush Island”) and, as a result,
    assessed liability under the applicable federal regulations. In addition, Ameren
    maintains that the district court ordered legally flawed injunctions at both Rush Island
    and at a different plant, Labadie Energy Center (“Labadie”). We affirm the district
    court’s liability determination, but we reverse in part the remedial portion of its order
    concerning the Labadie plant and remand for further proceedings consistent with this
    opinion.
    I. Background
    A. Statutory and Regulatory Background of the CAA
    “Congress enacted the Clean Air Act Amendments of 1970 seeking to
    guarantee the prompt attainment and maintenance of specified air quality standards.”
    Sierra Club v. Otter Tail Power Co., 
    615 F.3d 1008
    , 1011 (8th Cir. 2010) (quotations
    omitted). In enacting the CAA amendments, Congress “directed EPA to devise
    National Ambient Air Quality Standards (NAAQS) limiting various pollutants, which
    the States were obliged to implement and enforce.” 
    Id.
     (quotation omitted). The New
    Source Performance Standards (NSPS) program was a key part of the CAA’s
    regulatory scheme. 
    Id.
     The NSPS program “required EPA to develop technology-
    based performance standards designed to limit emissions from major new sources of
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    pollution.” 
    Id.
     (quotation omitted). Both newly constructed facilities and modified
    facilities with increased emissions constitute “[n]ew sources.” 
    Id.
     “It is ‘unlawful for
    any owner or operator of any new source to operate such source in violation of’
    applicable performance standards.” 
    Id.
     (quoting 
    42 U.S.C. § 7411
    (e)).
    The NSPS program, however, “did too little to ‘achieve the ambitious goals of
    the 1970 amendments.’” 
    Id.
     (quoting Env’t Def. v. Duke Energy Corp., 
    549 U.S. 561
    ,
    567 (2007)). “Merely setting emissions limits failed to improve air quality in those
    areas that had already attained the minimum standards of the NAAQS because
    polluters had no incentive to diminish emissions below the established limits.” 
    Id.
     As
    a result, in 1977, Congress amended the CAA “to add the ‘Prevention of Significant
    Deterioration’ (PSD) program, which seeks to ensure that the ‘air quality floor’
    established by the NAAQS does not ‘in effect become a ceiling.’” 
    Id.
     (quoting Sierra
    Club v. Thomas, 
    828 F.2d 783
    , 785 (D.C. Cir. 1987)).
    The PSD program limited construction of major emitting facilities with
    specified preconditions. 
    42 U.S.C. § 7475
    (a). “The term ‘construction’ when used in
    connection with any source or facility, includes the modification . . . of any source or
    facility.” 
    Id.
     § 7479(2)(C) (emphasis added). “The term ‘modification’ means any
    physical change in, or change in the method of operation of, a stationary source which
    increases the amount of any air pollutant emitted by such source or which results in
    the emission of any air pollutant not previously emitted.” Id. § 7411(a)(4).
    The PSD program prohibits the construction of a major emitting facility unless
    preconditions are satisfied. One precondition is that the proposed facility obtain a
    permit setting forth applicable emission limitations. Id. § 7475(a)(1). Another
    precondition is that “the owner or operator of such facility demonstrates . . . that
    emissions from construction or operation of such facility will not cause, or contribute
    to, air pollution in excess of” prescribed air quality standards. Id. § 7475(a)(3). The
    PSD program also requires the owner or operator to install “the best available control
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    technology for each pollutant subject to regulation . . . emitted from, or which results
    from, [the proposed] facility.” Id. § 7475(a)(4). The “‘best available control
    technology’ (BACT) . . . . is not a particular type of technology.” Otter Tail, 
    615 F.3d at 1011
     (quoting 
    42 U.S.C. § 7475
    (a)(4)). Instead, the BACT “is an ‘emission
    limitation based on the maximum degree of reduction of each pollutant subject to
    regulation . . . which the permitting authority, on a case-by-case basis, taking into
    account energy, environmental, and economic impacts and other costs, determines is
    achievable’ for the facility in question.” 
    Id.
     (alteration in original) (quoting 
    42 U.S.C. § 7479
    (3)).
    Only major modifications to emitting sources are subject to PSD review. Ala.
    Power Co. v. Costle, 
    636 F.2d 323
    , 399 (D.C. Cir. 1979). “Major modification means
    any physical change in or change in the method of operation of a major stationary
    source that would result in: a significant emissions increase . . . of a regulated NSR
    [New Source Review] pollutant . . . ; and a significant net emissions increase of that
    pollutant from the major stationary source.” 
    40 C.F.R. § 52.21
    (b)(2)(i).
    For projects that only involve “existing emissions units,” the EPA applies what
    it calls the actual-to-projected-actual applicability test. 
    Id.
     § 52.21(a)(2)(iv)(c).1 To
    apply this test, the “baseline actual emissions” must first be calculated. “Baseline
    actual emissions means the rate of emissions, in tons per year, of a regulated NSR
    pollutant . . . .” Id. § 52.21(b)(48).
    1
    This test provides: “A significant emissions increase of a regulated NSR
    pollutant is projected to occur if the sum of the difference between the projected
    actual emissions . . . and the baseline actual emissions . . . , for each existing
    emissions unit, equals or exceeds the significant amount for that pollutant . . . .” Id.
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    Next, the “projected actual emissions” must be calculated by
    determining the maximum annual rate, in tons per year, at which an
    existing emissions unit is projected to emit a regulated NSR pollutant in
    any one of the 5 years (12–month period) following the date the unit
    resumes regular operation after the project, or in any one of the 10 years
    following that date, if the project involves increasing the emissions
    unit’s design capacity or its potential to emit that regulated NSR
    pollutant and full utilization of the unit would result in a significant
    emissions increase or a significant net emissions increase at the major
    stationary source.
    Id. § 52.21(b)(41)(i). An “owner or operator of the major stationary source . . . [must]
    consider all relevant information” to calculate “the projected actual emissions.” Id.
    § 52.21(b)(41)(ii)(a). “[A]ll relevant information . . . include[s] . . . historical
    operational data, the company’s own representations, the company’s expected
    business activity and the company’s highest projections of business activity, the
    company’s filings with the State or Federal regulatory authorities, and compliance
    plans under the approved State Implementation Plan . . . .” Id. But the owner or
    operator “[s]hall exclude” from the projected actual emissions “that portion of the
    unit’s emissions following the project that an existing unit could have accommodated
    during the consecutive 24-month period used to establish the baseline actual
    emissions . . . and that are also unrelated to the particular project, including any
    increased utilization due to product demand growth.” Id. § 52.21(b)(41)(ii)(c). The
    “exclu[sion] [of] increases stemming from unrelated demand growth” is referred to
    as “the ‘demand growth exclusion.’” New York v. EPA, 
    413 F.3d 3
    , 16 (D.C. Cir.
    2005).
    Finally, the baseline actual emissions calculation is subtracted from the
    projected actual emissions calculation to determine if the difference between the
    numbers is “significant.” 
    40 C.F.R. § 52.21
    (a)(2)(iv)(c). A table in the regulations
    sets forth the numeric thresholds that are considered “significant” for each regulated
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    pollutant. 
    Id.
     § 52.21(b)(23)(i). If the difference in the projected actual emissions and
    the baseline actual emissions is significant, see id., then a permit is required before
    beginning construction on the project. Id. § 52.21(a)(2)(iii).
    The actual-to-projected-actual test is distinguishable from “a potential-to-
    potential test,” which “compare[s] past potential emissions with future potential
    emissions.” New York, 413 F.3d at 17. “[T]he plain language of the CAA indicates
    that Congress intended to apply NSR to changes that increase actual emissions
    instead of potential or allowable emissions . . . .” Id. at 40.
    B. Missouri’s State Implementation Plan
    “The PSD program is primarily implemented by the states through ‘state
    implementation plans’ (SIPs).” Otter Tail, 
    615 F.3d at
    1011 (citing 
    42 U.S.C. § 7471
    ). While “[s]tates have broad discretion in designing their SIPs,” their “plans
    must include certain federal standards.” 
    Id.
     The EPA reviews and approves States’
    SIPs. 
    Id.
     at 1011–12.
    Missouri expressly incorporated the EPA’s PSD regulations into its SIP
    (“Missouri SIP”). See 
    Mo. Code Regs. Ann. tit. 10, § 6.060
    (8)(A) (2007) (“All of the
    subsections of 40 CFR 52.21, other than [certain subsections], are hereby
    incorporated by reference.”). The EPA approved Missouri’s SIP, explaining that “the
    provisions of § 52.21 supersede the state provisions for purposes of the PSD
    program.” Approval and Promulgation of Implementation Plans; State of Missouri,
    
    71 Fed. Reg. 36,486
    -02, 36,487 (June 27, 2006); see also 
    id. at 36,489
     (“This revision
    also incorporates by reference the other provisions of 40 CFR 52.21 as in effect on
    July 1, 2003, which supersedes any conflicting provisions in the Missouri rule.
    Section 9, pertaining to hazardous air pollutants, is not SIP approved.”).
    -6-
    C. Title V Program
    In addition to the CAA’s PSD program, “the CAA . . . require[s] each covered
    facility to obtain a comprehensive operating permit setting forth all CAA standards
    applicable to that facility.” Otter Tail, 
    615 F.3d at
    1012 (citing 42 U.S.C. § 7661a(a)).
    The operating permits “incorporate into a single document all of the CAA
    requirements governing a facility. Similar to other CAA programs, Title V is
    implemented primarily by the states under EPA oversight. In states with EPA
    approved programs,” the state permitting authority issues the Title V permits. Id.
    (citations omitted). These permits “are subject to EPA review and veto.” Id. The EPA
    has approved Missouri’s operating permit program under Title V of the CAA. This
    program is incorporated into the Missouri SIP. See Mo. Code. Regs. Ann. tit. 10, §
    6.065 (2007).
    D. Factual Background and Procedural History
    This case involves Ameren’s Rush Island power plant, which includes two
    coal-fired electric generating units, Units 1 and 2. These units began service in 1976
    and 1977. They were grandfathered into the PSD program. They do not have air
    pollution control devices for sulfur dioxide. Rush Island currently emits
    approximately 18,000 tons of sulfur dioxide per year. Small performance
    improvements or increases in unit availability can result in a 40-ton increase in sulfur
    dioxide. For the Rush Island units to emit more than 40 tons of sulfur dioxide, it takes
    only an availability of 0.3 percent or an additional 21 hours of operation at full power.
    By 2005, problems with Units 1’s and 2’s major boiler components forced
    Ameren to frequently take the units out of service. This made the units underperform
    and reduced the amount of electricity Ameren could generate and sell from the units.
    Ameren decided to replace the problem components with new, redesigned
    components. Ameren, however, did not do any quantitative PSD review for Unit 1’s
    project and belatedly performed PSD review for Unit 2’s project. Ameren proceeded
    with the projects without reporting its planned modifications to the EPA, obtaining
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    the necessary permits, or installing pollution controls. To replace the major boiler
    components, Ameren took Unit 1 offline in 2007 and Unit 2 offline in 2010. Each
    unit was completely offline for three to four months to complete the projects. Ameren
    spent more than $20 million per project.
    By replacing the failing components with new, redesigned components,
    Ameren expected unit availability to improve by much more than 0.3 percent,
    allowing the units to operate hundreds of hours more per year after the projects.
    Ameren expected to use that increased availability (and increased capacity for Unit
    2) to burn more coal and generate more electricity. Unavoidably, the units would also
    emit more sulfur dioxide pollution.
    As Ameren expected, its replacement of the failing components resulted in
    increased availability at Units 1 and 2 by eliminating hundreds of outage hours per
    year. And, Unit 2’s capacity increased. The units ran more, burned more coal, and
    consequently emitted hundreds of tons more sulfur dioxide per year because of the
    operational increases.
    The government filed suit against Ameren in response to the projects. It alleged
    that Ameren violated the CAA, the Missouri SIP, and Ameren’s Rush Island Plant
    Title V Permit by performing major modifications on Units 1 and 2 without obtaining
    the necessary permits, installing pollution control technology, or otherwise complying
    with all applicable requirements.
    1. Liability Phase
    a. Summary Judgment
    The district court bifurcated the proceedings into a liability phase and a remedy
    phase. During the liability phase, the district court issued two summary-judgment
    orders. In the first summary-judgment order, the district court rejected Ameren’s
    argument that the major-modification test set forth in the federal regulations did not
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    provide the relevant PSD liability test because the Missouri SIP elsewhere separately
    defined modification to mean that “the source’s potential emissions would
    significantly increase.” United States v. Missouri (Ameren I), 
    158 F. Supp. 3d 802
    ,
    808 (E.D. Mo. 2016) (emphasis added). According to Ameren, the government could
    not establish liability because it never alleged that “the [Rush Island] projects
    increased the units’ potential emissions.” 
    Id.
     (emphasis added). In rejecting this
    argument, the court first explained that “the PSD rules impose their own independent,
    stand-alone applicability provisions in Section (8) of the Missouri SIP (incorporating
    EPA’s PSD rules set out at 40 C.F.R. 52.21).” 
    Id. at 809
    . The court reasoned that “the
    PSD-specific applicability language should trump the general applicability language
    in Section (1) of the [Missouri] SIP.” 
    Id.
    The court next cited the “well-established” “regulatory and statutory history of
    the PSD rules” as leaving “no doubt that the federal PSD rules are focused on ‘major
    modifications’ which are based on actual emissions determinations,” not potential
    emissions. 
    Id. at 810
    . The court found “most persuasive[] [that the] EPA’s approval
    of the SIP provided that the CAA and the program requirements as set out in 
    40 C.F.R. § 52.21
     would supersede any conflicting provisions in the state SIP.” 
    Id.
    (citing Approval and Promulgation of Implementation Plans; State of Missouri, 71
    Fed. Reg. at 36,489).
    Finally, the district court concluded that Ameren urged an interpretation of the
    SIP that would conflict with the PSD rules and, in the court’s view, “render a portion
    of the PSD rules superfluous.” Id.
    In its second summary-judgment order, the district court addressed causation
    and “the PSD program’s demand growth exclusion.” United States v. Ameren Mo.
    (Ameren II), No. 4:11-cv-77-RWS, 
    2016 WL 728234
    , at *9 (E.D. Mo. Feb. 24, 2016).
    According to the district court, “two main criteria . . . determine whether a major
    source of pollution must obtain a PSD permit. First, there must be a physical change,
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    and second, that change would be expected to cause a significant net increase in
    actual emissions.” 
    Id.
     The demand growth exclusion is relevant to the second
    criteria—“how to determine whether the physical changes would have caused a
    significant net emissions increase, and if so, whether any of the increased emissions
    may be excluded from review under the ‘demand growth exclusion.’” 
    Id.
     The district
    court rejected Ameren’s proposed interpretation of the exclusion as applying to “any
    emissions increases a unit could have accommodated at baseline.” 
    Id.
     Instead, the
    court held “that the demand growth exclusion requires a showing that the unit ‘could
    have accommodated’ the emissions at baseline and that . . . those increases were
    unrelated to the project.” 
    Id. at *11
    . The court also held that “while it remains the
    EPA’s burden to prove that Ameren should have expected the projects to cause an
    increase in emissions, the burden is Ameren’s to prove that the demand growth
    exclusion applies.” 
    Id.
    Also in the second summary-judgment order, the district court addressed
    Ameren’s argument that “because EPA brought suit after the challenged projects’
    completion,” it was “limited to an ‘actual increase’ theory.” 
    Id. at *13
    . Under
    Ameren’s actual-increase theory, the EPA would have to show that “the Projects
    actually caused emissions to increase” to establish Ameren’s liability. 
    Id.
     By contrast,
    under “an ‘expectations’ theory,” the EPA could establish liability by showing “that
    Ameren ‘should have expected’ the Projects to increase emissions.” 
    Id.
     The court held
    that the government could proceed on the expectations theory. 
    Id.
     at *13–16.
    Additionally, the court considered Ameren’s argument that the government had
    to “come forward with admissible evidence of what a reasonable power plant operator
    or owner would expect, and its failure to do so [was] fatal to EPA’s expectations
    theory case.” 
    Id. at *18
    . But the court agreed with the government “that no special
    standard of care evidence is required for the factfinder to be able to determine
    whether a reasonable power plant operator or owner would have expected the projects
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    to cause a significant emissions increase”; instead, “the PSD regulations themselves
    . . . guide the factfinder’s determination.” 
    Id.
    Finally, the court rejected Ameren’s argument that the court “lack[ed] subject
    matter jurisdiction to hear EPA’s [Title V] claim that Ameren [was] operating under
    an inadequate or deficient permit.” 
    Id. at *24
    .
    b. Trial
    Subsequently, the district court held a trial on the merits. After trial, the district
    court entered an order setting forth its factual findings and legal conclusions. See
    United States v. Ameren Mo. (Ameren III), 
    229 F. Supp. 3d 906
     (E.D. Mo. 2017). The
    court concluded that Ameren’s Rush Island overhauls were major modifications that
    triggered PSD pollution-control requirements. The district court found that “[t]he
    emissions evidence show[ed] [that] an increase related to the projects should have
    been expected and actually occurred.” 
    Id. at 997
     (emphasis omitted). The court
    identified categories of evidence that “all establish that there is a significant net
    [sulfur dioxide] increase of more than 40 tons that was caused by the projects.” 
    Id. at 998
    .
    First, the court identified “[t]wo key—and undisputed—characteristics of the
    Rush Island units.” 
    Id. at 988
    . The first characteristic was that “the Rush Island units
    are big sources of pollution.” 
    Id.
     The second characteristic was that “the Rush Island
    units are ‘baseload’ units” that are “cheap sources of electricity” and “operate as
    much as they can.” 
    Id.
     According to the court, “[t]hese two facts lead to a logical
    conclusion [that] if the Rush Island units are upgraded so they can generate more
    electricity, they will. Performance improvements have a direct impact on annual
    generation and pollution levels.” 
    Id.
    Second, Robert Koppe, a power plant performance expert, opined that the Rush
    Island’s plant availability increased because it replaced “these problematic
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    components.” 
    Id. at 989
    . Thereafter, “Dr. Ranajit Sahu, a permitting engineer and
    expert for the United States, took Mr. Koppe’s findings on expected improved
    availability and used them to calculate the expected additional pollution that would
    result from the improvements.” 
    Id. at 990
    . He “calculated an expected increase in
    emissions of 608 tons of [sulfur dioxide] post-project for Unit 1.” 
    Id.
     And, “[b]ased
    on Mr. Koppe’s prediction of regained availability, . . . Dr. Sahu calculated an
    expected increase of 415 tons per year of [sulfur dioxide] in Unit 2 that would result
    from the availability improvement alone.” 
    Id. at 992
    .
    Third, Dr. Ezra Hausman, a modeler and market consultant with 20 years’
    experience in the electric industry, explained that the “sophisticated computer
    modeling program” that Ameren used “to model and predict the Rush Island units’
    fuel needs . . . for the years after the 2007 and 2010 major boiler outages” “showed
    that both a unit’s capacity level and its availability are linearly related to the unit’s
    projected coal consumption.” 
    Id. at 994, 995
    . Thus, “if Ameren increased the number
    of hours its Rush Island units were able to run, or if the company enabled the units
    to operate at higher output levels during those hours, then the units would . . . burn[]
    more coal and, as a result, emit[] more pollution.” 
    Id.
     at 994–95. Dr. Hausman’s
    “results show[ed] that Ameren’s modeling would predict significant emissions
    increases at the Rush Island units as a result of the projects.” 
    Id. at 996
    .
    Finally, “the actual post-project data” showed “a significant net [sulfur dioxide]
    increase of more than 40 tons that was caused by the projects.” 
    Id. at 998
    . Both units
    were available more and operated every hour that they were available. Both units also
    increased their maximum generating levels. This resulted in both units increasing
    their sulfur dioxide pollution.
    In summary, the court determined that “[b]ased on the known facts that the
    Rush Island units are low-cost, baseload units, common sense compels the same
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    conclusion: improving availability or capacity at baseload units like Rush Island will
    result in additional operations and pollution.” 
    Id.
    Regarding liability, the district court also rejected Ameren’s defenses. First, the
    district court concluded that Ameren failed to satisfy “its burden of proving that the
    Rush Island projects fall within the narrow routine maintenance exemption.” 
    Id. at 1003
    . The court characterized “[t]he 2007 and 2010 major boiler outages [as]
    unprecedented events for Rush Island Units 1 and 2—they were the centerpieces of
    the ‘most significant’ outages in plant history.” 
    Id.
     (citation omitted).
    Second, the court rejected Ameren’s argument that any increases in production
    and pollution were merely the result of demand growth that should be excluded from
    the liability assessment. According to the court, the “relevant information” that
    Ameren had “showed that the Rush Island units’ performance would improve,
    resulting in increased generation and emissions.” 
    Id. at 1010
    .
    In summary, the district court “enter[ed] a finding of liability against Ameren,”
    concluding that the Rush Island Unit 1 and 2 projects described above were major
    modifications under the CAA, Ameren violated the PSD program’s requirements “by
    failing to obtain a preconstruction permit and install best available pollution control
    technology,” and Ameren violated Title V of the CAA. 
    Id. at 1017
    .
    2. Remedy Phase
    a. Summary Judgment
    After entering its post-trial order on liability, the district court proceeded to the
    remedy phase. The court addressed the parties’ summary-judgment motions. First, the
    court rejected Ameren’s argument “that the Clean Air Act does not authorize
    injunctions as a remedy for past violations.” United States v. Ameren Mo. (Ameren
    IV), 
    372 F. Supp. 3d 868
    , 871 (E.D. Mo. 2019). According to the court, “[t]he plain
    language of § 7413(b) gives the EPA authority to ‘commence a civil action’ for
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    injunctive relief or civil penalties, ‘or both,’ whenever a person ‘has violated or is in
    violation of any requirement or prohibition of’ EPA air quality control programs.”
    Id. (quoting 
    42 U.S.C. § 7413
    (b)). The court reasoned that § 7413(b)’s plain
    “language places no restriction on injunctive relief for past violations” and instead
    “authorizes the EPA to seek injunctive relief whenever a person has violated the
    Clean Air Act.” Id.
    In addition, the district court rejected Ameren’s argument that the court could
    not “order injunctive relief that includes emissions reductions or control technology
    at the Labadie Energy Center (Labadie) coal-fired power plant.” Id. at 874.
    b. Trial
    The district court subsequently held a remedy trial. Following the trial, the
    court issued an order imposing a two-pronged remedy with the purpose of “[(1)]
    bring[ing] Ameren’s Rush Island facility into compliance with the law and
    [(2)] . . . remediat[ing] the harm from the more than 162,000 tons—and counting—in
    excess [sulfur dioxide] that Rush Island emitted after Ameren failed to obtain a PSD
    permit there.” United States v. Ameren Mo. (Ameren V), 
    421 F. Supp. 3d 729
    , 802
    (E.D. Mo. 2019).
    As to compliance, the district court concluded that “Ameren must make Rush
    Island compliant by obtaining a PSD permit with emissions limitations based on wet
    FGD [flue gas desulfurization technology]” used as the BACT. 
    Id. at 806
     (emphasis
    omitted). The court determined that FGD technology is technically and economically
    feasible and “can remove 95% or more of [sulfur dioxide] emissions.” 
    Id. at 812
    .
    As to remediation, the district court concluded that “Rush Island’s excess
    pollution is best remediated by decreasing emissions at the nearby Labadie Energy
    Center.” 
    Id. at 789
     (emphasis omitted). Labadie consists of four coal-burning units
    and is located 35 miles west of St. Louis. Ameren argued that imposition of the
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    remedy was “extreme” and “constitute[d] a penalty” “because Labadie is ‘totally
    innocent,’ and Ameren has not violated the Clean Air Act there.” 
    Id. at 820
    . The
    district court rejected Ameren’s argument, reasoning that its “remedy is based on
    straightforward equitable principles and the authority [it] ha[s] under the Clean Air
    Act ‘to restrain’ violations, ‘to require compliance,’ and ‘to award any other
    appropriate relief.’” 
    Id.
     (quoting 
    42 U.S.C. § 7413
    (b)). According to the court, its
    remedy was “narrowly tailored” because “a tight geographic nexus [exists] between
    the harms Rush Island caused and the benefits gained through reducing Labadie’s
    emissions. Pollution from Labadie affects the same communities as those affected by
    Rush Island, and to the same degree.” 
    Id.
     at 820–21. The court reasoned that its
    remedy “achieve[d] the maximum possible environmental benefit”: “When Ameren
    reduces emissions at Labadie commensurate with the excess emissions from Rush
    Island, Ameren will have put the public in the place it would have been absent
    Ameren’s Clear Air Act violation.” 
    Id. at 821
    . The court explained that “Ameren’s
    ton-for-ton reductions at Labadie will lower the risks of premature mortality and
    disease in the same communities impacted by Ameren’s Rush Island violations.” 
    Id.
    The court rejected Ameren’s argument “that any injunction against its Labadie
    plant would constitute a penalty.” 
    Id.
     While the court acknowledged it could not
    “issue injunctive relief that would constitute a penalty,” it concluded that “[b]y
    ordering emissions reductions up to, but not surpassing, the excess emissions from
    Rush Island, [the court was] ordering relief that goes exactly to ‘remedying the
    damage caused to the harmed parties by the defendant’s action.’” 
    Id.
     (quoting United
    States v. Ameren Mo., No. 4:11-cv-77-RWS, 
    2016 WL 468557
    , at *1 (E.D. Mo. Feb.
    8, 2016)). The court “order[ed] Ameren to base its relief at Labadie on DSI [dry
    sorbent injection] control technology” “[t]o . . . ensure that any relief at Labadie does
    not surpass the damage caused by Rush Island.” 
    Id.
     Installation of DSI technology on
    Labadie’s units would allow Ameren to “operate DSI for as many years as necessary
    to remediate Rush Island’s excess emissions[] and terminate its use of DSI without
    suffering significant lost capital assets.” 
    Id.
     The court “order[ed] Ameren to begin
    -15-
    operating Labadie with DSI, or a more effective pollution control, beginning no later
    than three years after [its] order.” 
    Id. at 822
    .
    3. Summary
    In summary, the district court found Ameren in violation of the CAA for
    “mak[ing] major modifications to expand Rush Island’s capacity” without “apply[ing]
    for a PSD permit and meet[ing] reduced emissions requirements.” 
    Id. at 824
    . By
    failing to “apply for the required PSD permit,” Ameren “skirted PSD’s requirement
    to install the best available technology to control the pollution Rush Island emits.” 
    Id.
    “To remedy [Ameren’s] violation of the Clean Air Act,” the district court
    ordered Ameren to “apply for a PSD permit for Rush Island within ninety days,
    propose wet FGD as BACT in its permit application, and implement BACT no later
    than four and one-half years from [the] order.” 
    Id.
     “In addition to the relief [the court]
    order[ed] at Rush Island, [it] also order[ed] Ameren to reduce its pollution at Labadie
    in an amount equal to Ameren’s excess emissions at Rush Island.” 
    Id.
     It left Ameren
    the option whether to “install[] DSI or some other more effective pollution control at
    Labadie.” 
    Id.
    II. Discussion
    Ameren appeals the district court’s orders. It raises five arguments: (1) the
    Rush Island projects did not require permits under the Missouri SIP; (2) the Rush
    Island projects did not constitute major modifications; (3) the district court lacked
    jurisdiction under Article III and statutory authority under the CAA to enter the
    injunctions; (4) the injunctive relief ordered at Labadie is punitive, not remedial, and
    therefore prohibited; and (5) the district court lacked jurisdiction over the Title V
    claims. We address each in turn.
    -16-
    A. Missouri SIP
    Ameren first argues that “under the plain language of Missouri’s SIP, permits
    are required only for increases in potential emissions” and “it [is] undisputed that the
    [Rush Island] Projects would not, and did not, increase potential emissions.”
    Appellant’s Br. at 30. According to Ameren, the district court erroneously
    “substituted the federal regulations’ applicability standard,” which “nullified the SIP
    Permit Rule’s Applicability Provision.” 
    Id.
     at 30–31.
    The Missouri SIP identifies which construction or modification projects at
    emission sources require prior construction permits. 
    Mo. Code Regs. Ann. tit. 10, § 6.060
     (2007). Ameren cites to § 6.060(1) of the Missouri SIP, entitled
    “Applicability” (“Applicability Section”). This section governs Missouri’s air quality
    construction permit programs. The Applicability Section provides, in relevant part,
    that
    [n]o owner or operator shall commence construction[2] or modification
    of any installation subject to this rule, begin operation after that
    construction or modification, or begin operation of any installation
    which has been shut down longer than five (5) years without first
    obtaining a permit from the permitting authority under this rule.
    
    Mo. Code Regs. Ann. tit. 10, § 6.060
    (1)(C) (2007) (emphases added).
    In turn, the Missouri SIP offers two definitions of modification. First, it
    generally defines “[m]odification” as “[a]ny physical change, or change in method of
    operation of, a source operation or attendant air pollution control equipment which
    would cause an increase in potential emissions of any air pollutant emitted by the
    source operation.” 
    Id.
     § 6.020(2)(M)(10) (emphasis added). “Potential to emit” means
    2
    “It is undisputed that the projects at issue were not ‘construction’ as defined
    by the Missouri SIP or the PSD rules.” Ameren I, 158 F. Supp. 3d at 809 n.5.
    -17-
    the unit’s ability to emit at full design capacity “assuming continuous year-round
    operation.” Id. at § 6.020(2)(P)(19).
    Second, the Missouri SIP separately defines “Title I modification.”
    Id. § 6.020(2)(M)(11). A “Title I modification” is “[a]ny modification that requires
    a permit under 10 CSR 10-6.060 section (7) or (8), or that is subject to any
    requirement under 10 CSR 10-6.070 or 10 CSR 10-6.080.” Id. § 6.020(2)(T)(3)
    (emphasis added).3
    Ameren maintains that the Missouri SIP limits PSD applicability to only
    projects increasing both actual and potential emissions. According to Ameren, the
    Missouri SIP’s Applicability Section and definitional sections mean that “[i]f a
    project would not increase a unit’s potential emissions, it is not a modification and
    does not trigger permitting under the Applicability Provision.” Appellant’s Br. at 35.
    Because the government “never alleged that the projects increased the units’ potential
    emissions, Ameren argues that it [was] entitled to full summary judgment.” Ameren
    I, 158 F. Supp. 3d at 808–09.
    Ameren, however, overlooks that, in contrast to the general definition of
    modification in § 6.020(2)(M)(10), § 6.060(8)(A) of the Missouri SIP contains “PSD-
    specific applicability language.” Id. at 809 (emphasis added) (citing RadLAX Gateway
    Hotel, LLC v. Amalgamated Bank, 
    566 U.S. 639
    , 645 (2012)). That
    section—expressly referenced in the Missouri SIP’s definition of “Title I
    modification”—provides, in relevant part:
    3
    In addition to defining modification, the Missouri SIP independently defines
    “[m]ajor modification” as “[a]ny physical change or change in the method of
    operation at an installation or in the attendant air pollution control equipment that
    would result in a significant net emissions increase of any pollutant.” 
    Id.
    § 6.020(2)(M)(3). The Missouri SIP uses the term major modification in a section
    concerning BACT. See id. § 6.020(2)(B)(5).
    -18-
    (8) Attainment and Unclassified Area Permits.
    (A) All of the subsections of 40 CFR 52.21 other than (a) Plan
    disapproval, (q) Public participation, (s) Environmental impact
    statements and (u) Delegation of authority are incorporated by
    reference. 40 CFR 52.21 as used in this rule refers to 40 CFR 52.21
    promulgated as of July 1, 2003 as published by the Office of the Federal
    Register, U.S. National Archives and Records, 700 Pennsylvania
    Avenue NW, Washington, D.C. 20408. This rule does not incorporate
    any subsequent amendments or additions.
    
    Mo. Code Regs. Ann. tit. 10, § 6.060
    (8)(A) (2007) (emphases added).
    In turn, the federal regulation referenced in § 6.060(8)(A) of the Missouri SIP
    provides that the PSD’s “[a]pplicability procedures” “apply to the construction of any
    new major stationary source or the major modification of any existing major
    stationary source” located in a PSD area. 
    40 C.F.R. § 52.21
    (a)(2)(ii) (emphasis
    added). The regulations explicitly define major modification. “Major modification
    means any physical change in or change in the method of operation of a major
    stationary source that would result in: a significant emissions increase . . . of a
    regulated NSR pollutant . . . ; and a significant net emissions increase of that pollutant
    from the major stationary source.” 
    Id.
     § 52.21(b)(2)(i) (emphasis added). “A . . . major
    modification shall meet each applicable emissions limitation under the [SIP] and each
    applicable emissions standard and standard of performance under 40 CFR parts 60
    and 61.” Id. § 52.21(j)(1).
    The federal regulation establishes that a major modification triggers the PSD
    requirements. According to the regulation, “[n]o . . . major modification . . . shall
    begin actual construction without a permit that states that the . . . major
    modification will meet those requirements.” Id. § 52.21(a)(2)(iii). To assess whether
    a major modification occurred, the federal regulation states that an
    -19-
    “[a]ctual-to-projected-actual applicability test [applies] for projects that only involve
    existing emissions units.” Id. § 52.21(a)(2)(iv)(c) (emphasis added). Under that test,
    [a] significant emissions increase of a regulated NSR pollutant is
    projected to occur if the sum of the difference between the projected
    actual emissions . . . and the baseline actual emissions . . . , for each
    existing emissions unit, equals or exceeds the significant amount for that
    pollutant . . . .
    Id.
    As the district court observed, “EPA’s approval of the [Missouri] SIP illustrates
    why the specific PSD rules control.” Ameren I, 158 F. Supp. 3d at 810. In approving
    the Missouri SIP, the EPA stated, “[W]e are approving most of the revisions to the
    Construction Permits Required rule because the revisions incorporate, by reference,
    the Federal New Source Review reforms . . . . ” Approval and Promulgation of
    Implementation Plans; State of Missouri, 71 Fed. Reg. at 36,486. More specifically,
    it stated that it was “approving revisions to Missouri rule, 10 CSR 10-6.060,
    Construction Permits Required, into the SIP. This rule incorporates by reference the
    . . . PSD . . . program in 40 CFR 52.21 . . . .” Id. at 36,487.
    Importantly, the “EPA’s approval of the SIP provided that the CAA and the
    program requirements as set out in 40 C.F.R. 52.21 would supersede any conflicting
    provisions in the state SIP.” Ameren I, 158 F. Supp. 3d at 810 (quoting 71 Fed. Reg.
    at 36,486 (“This revision incorporates by reference the other provisions of 40 C.F.R.
    52.21 as in effect on July 1, 2003, which supersedes any conflicting provisions in the
    Missouri rule.” (emphasis added in Ameren I))).
    Furthermore, as the district court pointed out, Ameren’s argument that “the
    [Missouri] SIP first requires . . . that a threshold determination be made that a project
    is a ‘modification’” under § 6.020(2)(M)(1), “would render a portion of the PSD rules
    -20-
    superfluous.” Id. at 810. The Supreme Court rejected a similar argument in Duke
    Energy. In that case, the Court held that the EPA is not required “to conform its PSD
    regulations on ‘modification’ to their NSPS counterparts.” 
    549 U.S. at 565
    .
    According to the Court, aligning the PSD regulations with the NSPS regulations “was
    inconsistent with their terms and effectively invalidated them.” 
    Id.
     Relevant to the
    present case, the Court rejected the defendant power company’s argument that,
    “before a project can become a ‘major modification’ under the PSD regulations, it
    must meet the definition of ‘modification’ under the NSPS regulations.” 
    Id.
     at 581 n.8
    (citations omitted). According to the Court, “the language of the regulations [did] not
    support” such a reading because it would render portions of the PSD regulations
    superfluous. 
    Id.
     (“[I]t would be superfluous for PSD regulations to require a ‘major
    modification’ to be a ‘physical change in or change in the method of operation,’ if
    they presupposed that the NSPS definition of ‘modification,’ which contains the same
    prerequisite, had already been satisfied.” (citations omitted)).
    Finally, United States v. Cinergy Corp., 
    623 F.3d 455
     (7th Cir. 2010), upon
    which Ameren relies, is distinguishable. There, the EPA brought an enforcement
    action against several coal-fired power plants. 
    Id. at 456
    . As in the present case, the
    EPA alleged that the plants’ projects were major modifications requiring a PSD
    permit. 
    Id.
     The plants argued that no permit was required because the projects did not
    increase the units’ potential emissions under the Indiana SIP, which based
    applicability on increases in potential emissions instead of actual emissions. 
    Id. at 458
    . On appeal, the Seventh Circuit held that “[t]he Clean Air Act does not authorize
    the imposition of sanctions for conduct that complies with a [SIP] that the EPA has
    approved.” 
    Id.
     (citing 
    42 U.S.C. § 7413
    (a)(1)).
    Like the power plants in Cinergy, Ameren maintains that it lacked notice “that
    EPA would treat its approval of Sections 10–6.060(1)(C) (Applicability) and
    10–6.020(2)(M)(10) (definition of ‘modification’) as a rejection of them”;
    furthermore, it asserts that “allowing EPA to impose liability when it is undisputed
    -21-
    no modification has occurred would violate basic principles of due process and fair
    notice.” Ameren I, 158 F. Supp. 3d at 812. But Cinergy is distinguishable from the
    present case because (1) the Indiana SIP did not incorporate the PSD rules into the
    State’s plan; (2) the “EPA’s approval of the Indiana SIP did not expressly provide
    that the PSD rules as set out in the Code of Federal Regulations supersede any
    conflicting provisions in the state SIP”; and (3) the power plants in Cinergy had
    “actual notice” of the Indiana SIP provision, whereas “it is not clear that Ameren had
    actual notice of the SIP provision.” Id. Furthermore, Cinergy is merely persuasive
    authority and not binding on this court. See Duluth, Winnipeg & Pac. Ry. Co. v. City
    of Orr, 
    529 F.3d 794
    , 798 (8th Cir. 2008).
    Accordingly, we hold that the district court did not err in holding that the Rush
    Island projects required permits through application of the actual-to-projected-actual
    applicability test under 
    40 C.F.R. § 52.21
    (a)(2)(iv)(c), incorporated by reference in
    § 6.060(8)(A) of the Missouri SIP.
    B. Major Modification
    Alternatively, Ameren argues that “even if federal regulations governed
    applicability, Ameren was held liable under the wrong legal standards, independently
    requiring reversal.” Appellant’s Br. at 45. Ameren maintains that the district court
    erred in concluding the Rush Island projects constituted major modifications.
    Specifically, Ameren contends that the district court erroneously (1) shifted the
    burden of proof on causation; (2) “applied new interpretations of the federal
    regulations’ causation provision”; and (3) applied a “‘reasonable power plant
    operator’ standard the regulations do not require.” Id. at 45–46. In addition, Ameren
    asserts that the district court erred by permitting the government to use expert
    opinions on actual post-project emissions that were not disclosed. Id. at 56.
    A “[m]ajor modification” at emission sources occurs when a physical change
    in the facility would result in “a significant emissions increase.” 40 C.F.R.
    -22-
    § 52.21(b)(2)(i). “To satisfy its burden under the [CAA], the government ha[s] to
    show that at the time of the projects [Ameren] expected, or should have expected, that
    its modifications would result in a ‘significant net emissions increase’ . . . .” United
    States v. Ala. Power Co., 
    730 F.3d 1278
    , 1282 (11th Cir. 2013).
    1. Burden of Proof
    One feature of the federal regulation’s “projected-actual-emissions
    methodology [is] the exclusion from the emissions projection of any emissions due
    to increased demand.” New York, 413 F.3d at 31. This demand-growth exclusion
    functions as a type of defense for the source to avoid triggering PSD requirements.
    The federal regulation “allow[s] exclusion of emissions that could have been
    accommodated during the baseline period and ‘that are also unrelated to the particular
    project.’” Id. at 33 (quoting 
    40 C.F.R. § 52.21
    (b)(41)(ii)(c)). Emissions “unrelated to
    the particular project . . . include[] any increased utilization due to product demand
    growth.” 
    Id.
     (quoting 
    40 C.F.R. § 52.21
    (b)(41)(ii)(c)).
    Thus, under the regulation, “a source must”
    establish[] two criteria . . . before excluding emissions from its
    projection: “(1) [t]he unit could have achieved the necessary level of
    utilization during the consecutive 24-month period [the source] selected
    to establish the baseline actual emissions; and (2) the increase is not
    related to the physical or operational change(s) made to the unit.”
    
    Id.
     (alterations in original) (emphasis added) (quoting Prevention of Significant
    Deterioration (PSD) and Nonattainment New Source Review (NSR): Baseline
    Emissions Determination, Actual-to-Future-Actual Methodology, Plantwide
    Applicability Limitations, Clean Units, Pollution Control Projects, 
    67 Fed. Reg. 80,186
    -01, 80,203 (Dec. 31, 2002)); see also United States v. DTE Energy Co., 
    845 F.3d 735
    , 737 (6th Cir. 2017).
    -23-
    Ameren argues that “the [d]istrict [c]ourt improperly shifted the burden of
    proving causation to Ameren.” Appellant’s Br. at 46. Before the district court, the
    parties disputed who bore the burden of proving “that any increases in emissions were
    caused by demand growth.” Ameren II, 
    2016 WL 728234
    , at *11. Ameren argued that
    the EPA bore the burden of proving demand growth “because under the definition of
    ‘projected actual emissions,’ the regulations require that unrelated emissions be
    exempted from the calculation.” 
    Id.
     By contrast, the EPA maintained that Ameren
    bore the burden of proof on demand growth as “the party seeking to benefit from an
    exemption.” 
    Id.
     The district court held that “while it remains EPA’s burden to prove
    that Ameren should have expected the projects to cause an increase in emissions, the
    burden is Ameren’s to prove that the demand growth exclusion applies.” 
    Id.
    (emphasis added).
    The district court is correct. As recognized in New York and DTE Energy, it is
    the source’s burden to prove the applicability of the demand-growth exclusion. This
    is in accordance with the Supreme Court precedent that the party asserting the
    exception bears the burden of proving its applicability. NLRB v. Ky. River Cmty.
    Care, Inc., 
    532 U.S. 706
    , 711 (2001) (“The burden of proving the applicability of the
    supervisory exception . . . should thus fall on the party asserting it.”); FTC v. Morton
    Salt Co., 
    334 U.S. 37
    , 44–45 (1948) (“[T]he general rule of statutory construction that
    the burden of proving justification or exemption under a special exception to the
    prohibitions of a statute generally rests on one who claims its benefits . . . .”).
    As a result, we hold that the district court did not impermissibly shift the
    burden of proof to Ameren in proving the applicability of the demand-growth
    exclusion.
    2. Causation
    According to Ameren, in post-trial briefing, the government switched theories
    on how the district court should analyze increased demand to satisfy the demand-
    -24-
    growth exclusion. Ameren also asserts that the government, in effect, promulgated
    a new causation standard without following notice-and-comment rulemaking.
    Specifically, Ameren contends, the government persuaded the district court that
    Ameren had to show “demand growth for a specific unit’s generation.” Appellant’s
    Br. at 47. Ameren argues that this causation standard is “the exact opposite of EPA’s
    prior statements [that] ‘[d]emand growth refers to what the utility expects to be
    required to produce in the way of energy system wide, not for a single unit, but
    system wide.’” 
    Id.
     (citation omitted).
    We hold that the district court did not apply an improper causation standard.
    Citing New York, the district court expressly acknowledged that Ameren had to
    satisfy “two criteria . . . before excluding emissions from its projection.” Ameren III,
    229 F. Supp. 3d at 1003 (quoting New York, 413 F.3d at 33). The first requirement
    is that “the unit could have achieved the necessary level of utilization during the
    [baseline period].” Id. (emphasis added) (alteration in original) (quoting New York,
    413 F.3d at 33). The second requirement is that “the increase is not related to the
    physical or operational change(s) made to the unit.” Id. (emphasis added) (quoting
    New York, 413 F.3d at 33). This accurately states the appropriate causation standard.
    As a result, the district court did not err in holding that to prove the applicability of
    the demand-growth exclusion, Ameren had to establish “that demand on the unit
    increases.” Id. at 1003.
    3. Reasonable Power Plant Operator
    “In order to be deemed a major modification, [the government] . . . [must] show
    (1) a physical change to the plant; (2) a significant net emissions increase; and (3) a
    causal link between the two.” United States v. La. Generating, LLC, 
    929 F. Supp. 2d 591
    , 593 (M.D. La. 2012). As explained supra, “the government had to show that at
    the time of the projects [Ameren] expected, or should have expected, that its
    -25-
    modifications would result in a ‘significant net emissions increase’ . . . .” Ala. Power
    Co., 730 F.3d at 1282.4
    “[T]he [federal] regulations do not require a utility to be prescient, rather they
    require the company to undertake a reasonable estimate of what post-project
    emissions would be.” United States v. Duke Energy Corp., No. 1:00-cv-1262, 
    2010 WL 3023517
    , at *6 (M.D.N.C. July 28, 2010) (emphasis added) (citing United States
    v. Cinergy Corp., 
    458 F.3d 705
    , 709 (7th Cir. 2006)). “[T]he question [is] whether the
    owner of the facility at the time of the work . . . expected or reasonably should have
    expected, the work to increase emissions . . . .” La. Generating, 929 F. Supp. 2d at
    593 (emphasis added).
    In its motion for summary judgment at the liability phase, Ameren argued that
    “under an expectations theory,” the EPA had to “come forward with admissible
    evidence of what a reasonable power plant operator or owner would expect, and its
    failure to do so is fatal to EPA’s expectations theory case, warranting a grant of
    partial summary judgment.” Ameren II, 
    2016 WL 728234
    , at *18. While “Ameren
    acknowledge[d] that the determination of whether a party acted reasonably is
    generally a question for the factfinder,” it maintained that “when the touchstone for
    objective reasonableness requires a technical understanding of the subject matter that
    is beyond a layperson’s normal understanding, the factfinder must have guidance to
    make that determination.” 
    Id.
    The district court, however, determined “that no special standard of care
    evidence is required for the factfinder to be able to determine whether a reasonable
    power plant operator or owner would have expected the projects to cause a significant
    emissions increase.” 
    Id.
     The court reasoned that (1) “[t]he legal standards supplied
    4
    Alternatively, the government can prove a project actually resulted in a
    significant increase in emissions. See 
    40 C.F.R. § 52.21
    (a)(2)(iv)(b).
    -26-
    by the PSD rules are sufficient to guide the analysis,” and (2) “the parties
    . . . submitted mountains of evidence regarding what they believe a reasonable power
    plant operator or owner would have concluded.” 
    Id.
     Specifically, the parties’ experts
    would “testify about what Ameren did to make its projections, what information
    Ameren considered or did not consider, and why, and what the projections showed.”
    
    Id.
     The court noted that other “courts that have considered expectations theory
    enforcement actions” have applied “[t]his method.” 
    Id.
     (first citing United States v.
    Duke Energy Corp., 
    981 F. Supp. 2d 435
    , 439 (M.D.N.C. 2013); then citing Cinergy,
    
    623 F.3d at 459
    ; and then citing La. Generating, 929 F. Supp. 2d at 593).
    On appeal, Ameren now asserts that the district court erroneously denied
    “[s]tandard-of-care evidence [in] defining the specific boundaries of reasonableness.”
    Appellant’s Br. at 50. According to Ameren, “the written requirements of the
    regulations,” as opposed to the “expert witnesses’ subjective views,” “should have
    governed liability.” Id. Ameren maintains that “[b]y superimposing a[] [reasonable
    power plant operator] standard, the [d]istrict [c]ourt allowed EPA’s experts to second-
    guess Ameren’s conclusions even though Ameren followed the regulations’ written
    requirements.” Id. at 51.
    We conclude that the district court did not err in holding that “no special
    standard of care evidence is required for the factfinder to be able to determine
    whether a reasonable power plant operator or owner would have expected the projects
    to cause a significant emissions increase.” Ameren II, 
    2016 WL 728234
    , at *18.
    Instead, the district court, as the factfinder, was entitled to “consider all relevant
    information available to [Ameren] at the time of the project, including prior operating
    data and [Ameren’s] own statements and documents” in determining whether Ameren
    “should have predicted that a project would have caused a [significant] net increase.”
    
    Id. at *19
     (quoting Jury Instr. No. 23, United States v. Cinergy, 1:99-cv-1693-LJM-
    JMS (S.D. Ind. 2008), ECF No. 1335).
    -27-
    4. Expert Testimony
    Ameren argues that the district court abused its discretion in admitting and
    relying on undisclosed expert opinions. See Ryan v. Bd. of Police Comm’rs of St.
    Louis, 
    96 F.3d 1076
    , 1081 (8th Cir. 1996) (“We review the district court’s decision
    to admit evidence over a party’s objection for abuse of discretion.”).
    In two motions filed during the trial on the liability phase and in post-trial
    briefs, Ameren moved to exclude the expert testimony of Koppe and Dr. Sahu
    “concerning causation of the actual emissions increases.” Ameren III, 229 F. Supp.
    3d at 1015. Ameren argued to the district court that “the testimony concerning the
    causation of the actual emissions increases are new, undisclosed opinions.” Id.
    The district court denied Ameren’s motions to exclude Koppe’s and Dr. Sahu’s
    testimony. First, it rejected Ameren’s argument that the experts’ opinions were “new”
    and concluded that Ameren had “sufficient notice of both the United States’ actual
    emissions case and of Mr. Koppe and Dr. Sahu’s opinions.” Id. at 1016. The court
    highlighted that the experts “(1) analyzed the actual post-project data in their reports,
    the attachments, and their work papers, and (2) stated that the projected increases
    actually materialized.” Id. at 1015. Additionally, the court noted that the experts
    discussed in their reports and depositions “how the projects enable increased
    availability and contribute to increases in emissions.” Id. The court explained that the
    experts were not required to “state[] their opinions in the precise words that Ameren
    thinks they should have used” because the “notice required of expert opinions is not
    so formulaic.” Id.; see also Thompson v. Doane Pet Care Co., 
    470 F.3d 1201
    ,
    1202–03 (6th Cir. 2006) (explaining that Federal Rule of Evidence 26(a)(2)(B)
    “contemplates that the expert will supplement, elaborate upon, explain and subject
    himself to cross-examination upon his report”)).
    Second, the district court concluded that even if it erroneously admitted the
    expert testimony, Ameren was unable to “show that it was prejudiced by the
    -28-
    challenged testimony or the admission of the exhibits.” Ameren III, 229 F. Supp. 3d
    at 1016. This was because “[t]he evidence the United States presented to show that
    the actual emissions increases were caused by the projects was also presented in the
    context of its expectations case regarding the expected causes of projected emissions
    increases, so the challenged testimony is in part cumulative evidence.” Id. The court
    also noted Ameren’s “opportunity both during pre-trial discovery and during
    cross-examination at trial to test those opinions.” Id.
    Here, even assuming that the district court abused its discretion by admitting
    the expert testimony, “any error would be harmless.” Smith v. Tenet Healthsystem SL,
    Inc., 
    436 F.3d 879
    , 889 (8th Cir. 2006). Harmless error applies here because the
    district court, as the factfinder, expressly stated that had the expert testimony on
    actual emissions not been admitted, the result would not be different.
    C. Injunctive Relief
    Ameren argues generally that the district court lacked Article III jurisdiction
    and statutory jurisdiction to issue injunctive relief “based on Rush Island’s
    operation.” Appellant’s Br. at 66. According to Ameren, the district court found
    during the liability phase “that the Rush Island Projects were major modifications
    requiring permits before Ameren could commence construction.” Id. at 67. But,
    during the remedy phase, the government “did not seek to prove any injury from the
    violation it proved” and “[i]nstead . . . sought to obtain relief based on the harm from
    Rush Island’s operation without a PSD permit.” Id. Ameren maintains that
    “[o]perations do not cause an injury that the PSD program recognizes.” Id. Ameren
    further argues that the district court lacked jurisdiction to impose injunctive relief
    redressing “excess emissions.” Id. at 69. Ameren asserts that the government waived
    “penal relief, including civil penalties; an injunction to prevent construction; an
    injunction to obtain information about future planned projects; and declaratory
    relief.” Id. at 71 (citations omitted). Finally, Ameren argues that the CAA “does not
    -29-
    authorize injunctions for wholly past violations” and that “[o]nly past violations are
    at issue here.” Id. at 72.
    “We review a district court’s grant of a permanent injunction for abuse of
    discretion.” Kittle-Aikeley v. Strong, 
    844 F.3d 727
    , 735 (8th Cir. 2016). An abuse of
    discretion occurs when a district court “reaches its conclusion by applying erroneous
    legal principles or relying on clearly erroneous factual findings.” 
    Id.
     (citation
    omitted). “Where the determinative question is purely legal, our review is more
    accurately characterized as de novo.” 
    Id.
     (quotation omitted).
    “Whenever . . . the [government] finds that any person has violated or is in
    violation of any requirement . . . of an applicable implementation plan or permit, [the
    government] [must] notify the person . . . of such finding.” 
    42 U.S.C. § 7413
    (a)(1)
    (emphasis added). Only after the “expiration of 30 days following the date on which
    such notice of a violation [was] issued” may the government “bring a civil
    [enforcement] action.” 
    Id.
     § 7413(a)(1)(C). The government is authorized to
    “commence a civil action for a permanent or temporary injunction, or to assess and
    recover a civil penalty . . . , or both,” “[w]henever such person has violated, or is in
    violation of” a requirement of Title I of the CAA. Id. § 7413(b)(1) (emphasis added).
    A civil enforcement action
    may be brought in the district court of the United States for the district
    in which the violation is alleged to have occurred, or is occurring, or in
    which the defendant resides, or where the defendant’s principal place of
    business is located, and such court shall have jurisdiction to restrain
    such violation, to require compliance, to assess such civil penalty, to
    collect any fees owed the United States under this chapter (other than
    subchapter II) and any noncompliance assessment and nonpayment
    penalty owed under section 7420 of this title, and to award any other
    appropriate relief.
    Id. § 7413(b) (emphases added).
    -30-
    In summary,
    [t]he Clean Air Act authorizes the EPA to bring a civil enforcement
    action when any person has violated a permit or SIP, has violated any
    requirement in certain subchapters of the Clean Air Act (including the
    PSD program), or “attempts to construct or modify a major stationary
    source” in any state that the EPA Administrator has found out of
    compliance with the New Source Review program.
    United States v. EME Homer City Generation, L.P., 
    727 F.3d 274
    , 291–92 (3d Cir.
    2013) (emphases added).
    Section 7413(b) “limits a district court’s jurisdiction to awarding certain kinds
    of relief.” 
    Id. at 292
    . “Each type of relief in [§ 7413(b)] (except for civil penalties) is
    necessarily forward-looking.” Id. (footnote omitted). The remaining term —“[a]ny
    other appropriate relief”—is merely a “catch-all” provision that “follows ‘a list of
    specific items separated by commas.’” Id. at 293 (quoting Ali v. Fed. Bureau of
    Prisons, 
    552 U.S. 214
    , 225 (2008)). “As the word ‘other’ demonstrates, this general
    phrase is a residual category of the same type as the preceding items (namely, kinds
    of relief).” 
    Id.
     “[T]he canon of ejusdem generis requires us to interpret this catch-all
    as permitting forward-looking relief, consistent with the preceding types of relief in
    the list.” 
    Id. at 295
    .
    In Homer City, the Third Circuit held that “[t]he text of the Clean Air Act does
    not authorize an injunction against former owners and operators for a wholly past
    PSD violation, even if that violation causes ongoing harm.” 
    Id. at 291
     (emphases
    added). But the court “express[ed] no opinion” on whether injunctions are “available
    in general to remedy ongoing harm from wholly past violations.” 
    Id.
     at 291 n.19
    (emphases added). Indeed, as against the current owners, the court explained that the
    government could, after “completion of a facility’s modification, . . . still obtain an
    injunction requiring the owner or operator to comply with the PSD requirements.” 
    Id.
    -31-
    at 289 (emphases added); see also United States v. U.S. Steel Corp., 
    16 F. Supp. 3d 944
    , 950 (N.D. Ind. 2014) (“Requiring a company to do ‘a further round of
    modifications to get the permit’ could only be done through injunctive relief.”
    (quoting United States v. Midwest Generation, LLC, 
    720 F.3d 644
    , 646 (7th Cir.
    2013)).
    Homer City is distinguishable from the present case because it concerned
    injunctive relief against a facility’s former owners. United States v. Luminant
    Generation Co., L.L.C., 
    905 F.3d 874
    , 888 (5th Cir. 2018), reh’g en banc granted,
    
    929 F.3d 316
     (5th Cir. 2019).5 It does not detract from the plain language of
    § 7413(b), which “plainly gives district courts jurisdiction to restrain a violation,
    require compliance, and award any other appropriate relief whenever a person has
    committed a . . . violation” Id.
    Here, however, Ameren also specifically challenges the district court’s
    injunction against its Labadie plant, which committed no violations of the CAA.
    According to Ameren, neither the CAA nor the regulations authorize such relief.
    Under § 7413, a district court “has the authority to order [a defendant] to take
    appropriate actions that remedy, mitigate and offset harms to the public and the
    environment caused by the [defendant’s] proven violations of the CAA.” United
    States v. Cinergy Corp., 
    582 F. Supp. 2d 1055
    , 1060 (S.D. Ind. 2008) (emphasis
    added); see also United States v. Oliver, No. 3:06-CV-196-JWS, 
    2009 WL 10671371
    ,
    at *13 (D. Alaska June 25, 2009) (“Section 113(b) of the Clean Air Act, 
    42 U.S.C. § 7413
    (b), expressly provides for injunctive relief to redress violations of the Act.”
    (emphasis added)), aff’d, 394 F. App’x 376 (9th Cir. 2010).
    5
    The Fifth Circuit ultimately dismissed the appeal in Luminant on the parties’
    motion.
    -32-
    Here, the government never provided notice of or alleged that the Ameren’s
    Labadie plant committed a violation of the CAA. The plain language of § 7413(b) and
    caselaw make clear that the injunctive relief a district court may award must redress
    a violation of the CAA. See 
    42 U.S.C. § 7413
    (b)(1)–(3) (permitting civil enforcement
    actions “[w]henever such person has violated, or is in violation of” certain
    requirements and noting that the district “court shall have jurisdiction to restrain such
    violation”). Because Ameren committed no violation of the CAA at its Labadie plant,
    the district court lacked authority to authorize injunctive relief as to it. Cf. United
    States v. Cinergy Corp., 
    618 F. Supp. 2d 942
    , 967 (S.D. Ind. 2009) (denying
    government’s requested relief because the remedy would be punitive as the
    government proved no violation at the non-source unit against which it was sought.),
    rev’d on other grounds, 
    623 F.3d 455
     (7th Cir. 2010); United States v. Westvaco
    Corp., No. MJG-00-2602, 
    2015 WL 10323214
    , at *12 & n.27 (D. Md. Feb. 26, 2015)
    (rejecting government’s request for the district court to order the defendant “to install
    control technology on a totally ‘innocent’ boiler” that the government never alleged
    “violated PSD regulations” (footnote omitted)).
    Accordingly, we reverse the Labadie injunction and remand for further
    proceedings consistent with this opinion.
    E. Jurisdiction over Title V Claims
    Finally, Ameren challenges the district court’s jurisdiction over the Title V
    claims.
    Ameren operates Rush Island under a Title V permit issued by the Missouri
    Department of Natural Resources. This permit “restat[ed] the requirement that
    Ameren was prohibited from performing any unpermitted major modifications of
    Rush Island Units 1 or 2.” Ameren III, 229 F. Supp. 3d at 985.
    -33-
    The government brought Title V claims against Ameren, and Ameren
    challenged the district court’s subject matter jurisdiction to hear those claims. It
    argued—as it does here—that the Title V violation “is reviewable exclusively by the
    courts of appeals, not collaterally in civil . . . enforcement actions in the district
    courts.” Appellant’s Br. at 73 (alteration in original) (quoting Homer City, 727 F.3d
    at 296–97).
    Ameren’s jurisdictional argument lacks merit. “The EPA has authority to bring
    a civil enforcement action against a person who, among other things, ‘has violated,
    or is in violation of, any other requirement or prohibition of [various subchapters,
    including Title V].’” Homer City, 727 F.3d at 298 (alteration in original) (quoting 
    42 U.S.C. § 7413
    (b)(2)). In turn, Title V’s plain text “lists only two ways in which it can
    be violated: operating without a Title V permit or violating the terms of a Title V
    permit while operating a source.” 
    Id.
     (emphasis added) (citing 42 U.S.C.§ 7661a(a)).
    The district court expressly found that Ameren violated an express permit term
    prohibiting it from performing unpermitted major modifications. Cf. Otter Tail, 
    615 F.3d at 1020
    . Under § 7413(b), the district court had jurisdiction to consider whether
    Ameren violated the express terms of its Title V permit.
    III. Conclusion
    Accordingly, we affirm the judgment of the district court in all respects except
    as to the injunctive relief entered against Ameren’s Labadie plant. We remand for
    further proceedings consistent with this opinion.
    ______________________________
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