William Liebhart v. SPX Corporation ( 2019 )


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  •                               In the
    United States Court of Appeals
    For the Seventh Circuit
    ____________________
    Nos. 18-1918 & 18-2598
    WILLIAM LIEBHART & NANCY LIEBHART,
    Plaintiffs-Appellants,
    v.
    SPX CORPORATION, TRC ENVIRONMENTAL CORPORATION, &
    APOLLO DISMANTLING SERVICES, INC.
    Defendants-Appellees.
    ____________________
    Appeal from the United States District Court for the
    Western District of Wisconsin.
    No. 16-cv-700 — James D. Peterson, Chief Judge.
    ____________________
    ARGUED DECEMBER 4, 2018 — DECIDED MARCH 6, 2019
    ____________________
    Before BAUER, KANNE, and BRENNAN, Circuit Judges.
    KANNE, Circuit Judge. William and Nancy Liebhart to-
    gether own three houses on the same block in Watertown,
    Wisconsin. Besides a few other houses, the rest of the block
    was previously occupied by an abandoned transformer fac-
    tory, last owned by SPX Corporation. In 2014, SPX demol-
    ished the building with the assistance of TRC Environmental
    Corporation and Apollo Dismantling Services (collectively,
    2                                       Nos. 18-1918 & 18-2598
    “the defendants”). The Liebharts allege that dust and debris
    containing toxic chemicals migrated onto their properties,
    contaminating their yards and jeopardizing their health and
    the health of their tenants.
    The Liebharts sued under federal statutes authorizing pri-
    vate rights of action for environmental contamination. They
    also brought various state-law claims. Following discovery
    and the submission of expert witness reports, the district
    court denied the Liebharts’ motion for partial summary judg-
    ment and granted summary judgment to the defendants with
    costs. Although the district court adequately evaluated the ex-
    pert witnesses and did not abuse its discretion in its proce-
    dural decisions, the court set the bar unnecessarily high for
    the plaintiffs to show a violation of the applicable federal stat-
    utes. For that reason, we vacate the district court’s judgment
    and remand for reconsideration.
    I. BACKGROUND
    The factory dates to the 1920s and was used to manufac-
    ture various industrial equipment. Most relevant to our pur-
    pose, the factory manufactured power transformers contain-
    ing polychlorinated biphenyls (PCBs), a carcinogenic chemi-
    cal banned by the Environmental Protection Agency in 1979.
    See Polychlorinated Biphenyls (PCBs) Manufacturing, Pro-
    cessing, Distribution in Commerce, and Use Prohibitions, 
    44 Fed. Reg. 31,514
     (May 31, 1979) (codified at 40 C.F.R. pt. 761).
    The parties all agree that the facility has not manufactured or
    handled any items containing PCBs since 1971, and that it
    shut down completely in 2005.
    But even with all the products and manufacturing equip-
    ment removed, PCB contaminants remained in the facility. In
    Nos. 18-1918 & 18-2598                                       3
    2009, SPX retained TRC and another company (not named as
    a defendant in this suit) to study the property and determine
    the extent and precise location of any PCB contamination.
    Those studies revealed that the concrete floor of the factory
    was generally contaminated, with concentrated amounts lo-
    cated in specific areas throughout the site.
    Several years went by. In 2014, SPX decided to move ahead
    with the demolition, retaining Apollo to conduct the work
    and TRC to supervise the project. That November, the defend-
    ants timely proposed a self-implementing cleanup plan to the
    EPA, as required by 
    40 C.F.R. § 761.61
    (a). The trouble began
    as demolition commenced in January 2015. The Liebharts al-
    lege that Apollo demolished the building recklessly, failing to
    use appropriate safety methods to control the dust generated
    by demolition equipment. They assert that their properties
    were covered in dust, and they submitted hundreds of photos
    and videos of dust from the facility blowing toward their
    homes to support their allegation.
    The Liebharts filed a complaint with the local government
    in February. They also collected a dust-covered sample of
    snow from their yard and placed it in a mason jar. Soon there-
    after, a representative of the Wisconsin Department of Natu-
    ral Resources (“DNR”) contacted the defendants about the
    Liebharts’ concerns. In April, TRC collected samples of the
    surface soil (roughly down to eight inches below ground) on
    both the industrial and residential properties. Sure enough,
    the properties tested positive for the presence of PCBs. In Au-
    gust, the Liebharts vacated the property on advice of their
    physician to avoid further exposure to the chemicals. Frus-
    trated with the lack of action, William Liebhart had the snow
    4                                       Nos. 18-1918 & 18-2598
    sample tested for PCBs. Although the sample did, in fact, con-
    tain PCBs, the irregular manner of collection and storage
    spoiled the sample, and the laboratory declined to endorse the
    results with any confidence.
    In September 2015, SPX submitted a plan to remediate the
    contamination to the DNR. In turn, the Liebharts sued in fed-
    eral district court in October. The complaint sought injunctive
    relief under both the Resource Conservation and Recovery
    Act (RCRA), 
    42 U.S.C. § 6901
     et seq., and the Toxic Substances
    Control Act (TSCA), 
    15 U.S.C. § 2601
     et seq. In addition, the
    Liebharts brought a host of state-law claims under supple-
    mental jurisdiction, including strict liability, negligence, tres-
    pass, nuisance, and negligent infliction of emotional distress.
    During discovery, the Liebharts submitted to further test-
    ing for PCBs both in their yard and inside their home. They
    also underwent blood testing. Although the external surveys
    revealed a more comprehensive picture of the extent to which
    the soil on the Liebharts’ properties contained PCBs, the in-
    ternal sampling and blood tests were both negative for con-
    tamination. The Liebharts later learned in October 2017 that
    the defendants allegedly buried some of the concrete remains
    on-site rather than removing them to a toxic waste dump as
    required by the EPA-approved clean-up plan.
    The parties prepared and submitted the reports of the ex-
    pert witnesses who were to testify at trial. Among those, three
    are pertinent to our discussion. First, the Liebharts submitted
    a report by John Woodyard, a licensed professional engineer.
    His report included a description of standard methods used
    when demolishing PCB-contaminated buildings and an anal-
    ysis of the purported ways in which the defendants deviated
    from those practices, thereby causing the contamination of the
    Nos. 18-1918 & 18-2598                                        5
    residences. The Liebharts’ second expert was Dr. David Car-
    penter, a public health physician who opined on ways in
    which the Liebharts might have been exposed to PCBs and the
    potential health effects of continuing exposure. He concluded
    that “there is no ‘safe’ level of exposure to PCBs that does not
    increase the risk of disease.” Finally, the defendants submit-
    ted a report prepared by Dr. Russell Keenan, a toxicologist
    who analyzed the survey data and determined that it was im-
    possible to determine whether the presence of PCBs on the
    Liebharts’ property was due to the recent demolition or to
    runoff that occurred over the last several decades.
    In December 2017, the Liebharts moved for partial sum-
    mary judgment on the issue of causation, reserving the issue
    of damages for a jury trial. The defendants cross-moved for
    summary judgment; they also filed a motion to exclude the
    testimony of plaintiffs’ experts Woodyard and Carpenter un-
    der Fed. R. Evid. 702. In February 2018, after those motions
    were fully briefed to the court, the Liebharts sought leave to
    amend their complaint. In light of the information they ob-
    tained through discovery regarding the burial of concrete on
    the property, they intended to allege separate RCRA and
    TSCA violations and seek an enlargement of the proposed in-
    junction to include removal of that material.
    The district court issued its decisions on March 30. First,
    the court granted in part the defendants’ motion to exclude
    the plaintiffs’ expert witness reports. The court explained that
    Woodyard’s report was “equivocal” as to the issue of causa-
    tion; it hedged on whether the contaminants came from dem-
    olition or from runoff during the preceding decades. See
    Liebhart v. SPX Corp., No. 16-cv-700-jdp, 
    2018 WL 1583296
     at
    6                                       Nos. 18-1918 & 18-2598
    *3–4 (W.D. Wis. Mar. 30, 2018). Second, the report “over-
    look[ed] too much significant evidence” and failed to account
    for “obvious alternative explanations” in determining the
    cause of the contamination. 
    Id. at *4
     (quoting Fed. R. Evid. 702
    advisory committee’s note to 2000 amendments). Finally, the
    court noted that Woodyard’s report depended on “unreliable
    or uninformative” evidence, including the Liebharts’ defec-
    tive snow sample, while omitting other evidence such as grass
    clippings and a chromatogram that allegedly detected PCBs
    on the property. 
    Id.
     at *4–5. For those reasons, the court ex-
    cluded Woodyard’s report in its entirety. 
    Id. at *5
    .
    Although the court admitted the vast majority of Dr. Car-
    penter’s report, it struck Carpenter’s conclusion that “there is
    no ‘safe’ level of exposure to PCBs that does not increase the
    risk of disease” as unsupported by the medical studies he
    cited. 
    Id. at *5
    . In doing so, the court pointed to the absence of
    PCBs inside the Liebharts’ home and in their blood, suggest-
    ing that the Liebharts had not actually been exposed to PCBs
    and so could not have suffered harm. 
    Id.
     at 5–6.
    With that expert testimony off the table, the district court
    concluded that the Liebharts failed to present any admissible
    evidence to support their RCRA and TSCA claims. The re-
    maining photos and videos certainly showed dust migrating
    onto the Liebharts’ property, but there was no reliable evi-
    dence proving that the dust contained PCBs. Given that any
    PCBs detected in the soil may have been there prior to the
    demolition, the lack of evidence doomed the Liebharts’ case.
    The court denied partial summary judgment to the plaintiffs,
    granted summary judgment to the defendants on the federal
    claims, and dismissed the state-law claims without prejudice.
    Nos. 18-1918 & 18-2598                                         7
    The district court also denied the Liebharts’ petition for
    leave to amend their complaint on two grounds. First, alt-
    hough the court acknowledged that the plaintiffs discovered
    the factual basis for the new counts over a year after filing the
    initial complaint, it also noted that they took an additional
    four months thereafter to seek leave to amend. During that
    intervening period, the parties had submitted and briefed
    their motions for summary judgment, and the trial date was
    fast approaching. It found their petition untimely. Second, the
    district court determined that the new claims were futile un-
    der both statutes' advance-notice requirements.
    The plaintiffs immediately appealed. Several months after
    the judgment, the clerk of the district court imposed costs on
    the Liebharts in the amount of $46,320.02. The Liebharts sep-
    arately appealed that decision. We consolidated the two ap-
    peals and now consider them together.
    II. ANALYSIS
    The Liebharts raise five issues for our consideration. First,
    they argue that the district court erred in excluding the opin-
    ions of expert witnesses Woodyard in full and Carpenter in
    part. As part of that argument, they allege that the district
    court failed to apply the same stringent standard to the de-
    fendants’ expert Keenan. Second, they contend that summary
    judgment was inappropriate because, even absent the testi-
    mony of their expert witnesses, they submitted adequate pho-
    tographic and scientific evidence to state a valid claim under
    RCRA and TSCA. Third, they challenge the district court’s de-
    nial of injunctive relief in light of deficiencies they have iden-
    tified in SPX’s state-approved clean-up plan. Fourth, they ar-
    gue that the district court abused its discretion in denying
    8                                       Nos. 18-1918 & 18-2598
    leave to amend their complaint. Finally, they challenge the
    imposition of costs.
    But there’s a larger issue looming in the background. The
    district court’s opinion operates under the assumption that
    RCRA plaintiffs must demonstrate “an imminent and sub-
    stantial danger with evidence of health problems they have
    already suffered.” Liebhart, 
    2018 WL 1583296
     at *6. Relying
    primarily on Foster v. United States, 
    922 F. Supp. 642
     (D.D.C.
    1996), the district court set a high bar for RCRA plaintiffs,
    holding that “it doesn’t follow necessarily that there is an im-
    minent and substantial risk of harm simply because there is
    some amount of PCBs on the property.” Liebhart 
    2018 WL 1583296
     at *5. We review that question of law, which was the
    underlying basis for the award of summary judgment, de
    novo. Daugherty v. Harrington, 
    906 F.3d 606
    , 609 (7th Cir. 2018).
    A. RCRA Requires Only that Harm “May” Be Imminent
    The question of how much harm a plaintiff must prove to
    make out a prima facie violation of RCRA has led to much dis-
    cussion among the circuits. We have yet to tackle that issue
    head on, so the district court necessarily had to look else-
    where for guidance. Passed in 1976, “RCRA is a comprehen-
    sive environmental statute that empowers [the] EPA to regu-
    late hazardous wastes from cradle to grave.” City of Chicago v.
    Envtl. Def. Fund, 
    511 U.S. 328
    , 331 (1994). The statute’s “pri-
    mary purpose … is to reduce the generation of hazardous
    waste and to ensure the proper treatment, storage, and dis-
    posal of that waste which is nonetheless generated, ‘so as to
    minimize the present and future threat to human health and
    the environment.’” Meghrig v. KFC Western, Inc., 
    516 U.S. 479
    ,
    483 (1996) (quoting 
    42 U.S.C. § 6902
    (b)).
    Nos. 18-1918 & 18-2598                                           9
    Although the EPA has the primary responsibility for en-
    forcing the law, the statute, “like other environmental laws,
    … contains a citizen suit provision, § 6972, which permits pri-
    vate citizens to enforce its provisions in some circumstances.”
    Id. at 484. As relevant to this case, the statute provides that
    any person may commence a civil action on his own
    behalf … against any person, … including … any
    past or present owner or operator of a treatment,
    storage, or disposal facility, who has contributed or
    who is contributing to the past or present handling,
    storage, treatment, transportation, or disposal of any
    solid or hazardous waste which may present an im-
    minent and substantial endangerment to health or
    the environment.
    
    42 U.S.C. § 6972
    (a)(1)(B) (emphasis added). Notably, Con-
    gress amended the language in 1980 by substituting the
    phrase “may present” for the original 1976 wording “is pre-
    senting.” Maine People’s All. and Nat. Res. Def. Council v.
    Mallinckrodt, Inc., 
    471 F.3d 277
    , 287 (1st Cir. 2006) (citing Solid
    Waste Disposal Act of 1980, Pub. L. 96–482, § 25, 
    94 Stat. 2334
    ,
    2348). The section authorizes district courts to grant injunctive
    relief and “order [a violator] to take such other action as may
    be necessary” to remediate the endangerment. Id.; see also Me-
    ghrig, 
    516 U.S. at 484
     (“Under a plain reading of this remedial
    scheme, a private citizen suing under § 6972(a)(1)(B) could
    seek a mandatory injunction, i.e., one that orders a responsible
    party to ‘take action’ by attending to the cleanup and proper
    disposal of toxic waste, or a prohibitory injunction, i.e., one
    that ‘restrains’ a responsible party from further violating
    RCRA.”); Avondale Fed. Sav. Bank v. Amoco Oil Co., 
    170 F.3d 692
    , 694 (7th Cir. 1999).
    10                                     Nos. 18-1918 & 18-2598
    The critical question in this case is how to determine
    whether alleged contamination “may present an imminent
    and substantial endangerment to health.” § 6972(a)(1)(b). We
    touched on this question only briefly in Albany Bank & Trust
    Co. v. Exxon Mobil Corp., 
    310 F.3d 969
    , 973 (7th Cir. 2002).
    There, we first outlined the elements of a prima facie RCRA
    claim: “a plaintiff must allege (1) that the defendant has gen-
    erated solid or hazardous waste, (2) that the defendant is con-
    tributing to or has contributed to the handling of this waste,
    and (3) that this waste may present an imminent and substan-
    tial danger to health or the environment.” 
    Id.
     (citing Cox v.
    City of Dallas, 
    256 F.3d 281
    , 282 (5th Cir. 2001)). We then ob-
    served, interpreting the final element, that “[i]mminence does
    not require an existing harm, only an ongoing threat of future
    harm.” 
    Id.
     (citing Cox, 
    256 F.3d at 299
    ). That is the extent of
    our circuit precedent on the “may present” language con-
    tained in § 6972(a)(1)(B).
    But our sister circuits have engaged with this question in
    great depth. In the first major case interpreting the provision,
    the Third Circuit emphasized that the statute “enhanced the
    courts’ traditional equitable powers by authorizing the issu-
    ance of injunctions when there is but a risk of harm, a more
    lenient standard than the traditional requirement of threat-
    ened irreparable harm.” United States v. Price, 
    688 F.2d 204
    ,
    211 (3d Cir. 1982). The court found the statutory language
    “unequivocal,” demonstrating that Congress “intended to
    confer upon the courts the authority to grant affirmative eq-
    uitable relief to the extent necessary to eliminate” the risks
    posed by toxic waste. 
    Id.
     at 213–14.
    In the subsequent decades, several other circuits adopted
    and further developed the same interpretation of § 6972. See
    Nos. 18-1918 & 18-2598                                         11
    Mallinckrodt, 
    471 F.3d at 277
    ; Dague v. City of Burlington, 
    935 F.2d 1343
    , 1355–56 (2d Cir. 1991), rev’d in part on other grounds,
    
    502 U.S. 1071
     (1992); Interfaith Cmty. Org. v. Honeywell Int’l,
    Inc., 
    399 F.3d 248
     (3d Cir. 2005); United States v. Waste Indus.,
    Inc., 
    734 F.2d 159
    , 165 (4th Cir. 1984) (rejecting the argument
    that “[§ 6972] was designed to control pollution only in emer-
    gency situations”); Cox, 
    256 F.3d at
    299–301; Price v. United
    States Navy, 
    39 F.3d 1011
    , 1019 (9th Cir. 1994); Burlington N.
    and Santa Fe Ry. Co. v. Grant, 
    505 F.3d 1013
    , 1019–22 (10th Cir.
    2007); Parker v. Scrap Metal Processors, Inc., 
    386 F.3d 993
    , 1014–
    15 (11th Cir. 2004). We now join those courts and explicitly
    embrace the core content of their interpretation.
    The district court therefore used an incorrect legal stand-
    ard to evaluate the Liebharts’ argument that PCBs from the
    demolition may present an imminent and substantial danger
    to their health and that of their tenants. It did not cite any of
    the cases we listed above, but instead relied on a single district
    court decision from a circuit that has not yet addressed the
    issue. See Liebhart, 
    2018 WL 1583296
     at *5 (quoting Foster, 
    922 F. Supp. at 662
     (“While there can be no question that the levels
    of contamination present at the Site may warrant future re-
    sponse action, the plaintiff cannot establish either a current
    risk of substantial or serious threatened harm, or some neces-
    sity for action.”)).
    That error undercuts several of the reasons the district
    court gave for rejecting the Liebharts’ RCRA claim. For exam-
    ple, the district court cursorily adopted a passing statement
    we made over twenty-five years ago that “[t]he [EPA’s] ac-
    cepted safe level of PCBs in the environment is fifty parts per
    million,” 
    id.
     (quoting Cincinnati Ins. Co. v. Flanders Elec. Motor
    12                                         Nos. 18-1918 & 18-2598
    Serv., Inc., 
    40 F.3d 146
    , 148 (7th Cir. 1994)), to create a require-
    ment that the Liebharts show that PCB contamination on their
    property met that threshold. But there is no requirement in
    RCRA for a plaintiff to make “a particular quantitative show-
    ing as a sine qua non for liability.” Interfaith, 
    399 F.3d at 260
    ; see
    also Dague, 
    935 F.2d at 1356
    . Only one circuit has come to an
    arguably contrary conclusion. In Price v. United States Navy,
    
    818 F. Supp. 1323
    , 1325 (S.D. Cal. 1992), aff’d 
    39 F.3d 1011
     (9th
    Cir. 1994), the district court required RCRA plaintiffs to show
    that “the level of contaminants [was] above levels that are con-
    sidered acceptable by the State.” But as the Interfaith court
    noted, the Ninth Circuit’s opinion affirming the district
    court’s judgment did not discuss that requirement. RCRA
    does not require that plaintiffs demonstrate contamination
    above some agency-derived threshold level of concentration.
    
    399 F.3d at
    260–61. It merely requires that they show that con-
    taminants on the property are seriously dangerous to human
    health (or will be, given prolonged exposure over time). See
    Cox, 
    256 F.3d at
    299–300 (“an endangerment is ‘substantial’ if
    it is ‘serious’” (quoting United States Navy, 
    39 F.3d at 1019
    )).
    That’s especially true when the standard is taken out of
    context. The district court relied on Cincinnati Ins. Co. to sup-
    port its contention that contamination below the threshold
    level of fifty parts per million (“ppm”) does not qualify as a
    regulatory violation, thereby contradicting Woodyard’s opin-
    ion regarding safe levels of PCBs and providing the grounds
    for excluding it. In that case, we evaluated whether an insur-
    ance company was required to indemnify its insured for dam-
    ages arising out of PCB contamination at an industrial site.
    The EPA had identified the insured as potentially liable under
    the Comprehensive Environmental Response, Compensation,
    and Liability Act of 1980 (CERCLA), 
    42 U.S.C. § 9601
     et seq. In
    Nos. 18-1918 & 18-2598                                       13
    that context, we noted that the contaminated site contained
    PCBs concentrated at levels up to 58,000 ppm, well above the
    EPA’s general regulatory threshold of fifty ppm. 
    40 F.3d at
    148
    (citing 
    40 C.F.R. § 761.60
    ).
    But that regulation, still in effect today, identifies indus-
    trial equipment and other wastes contaminated at levels
    above fifty ppm and requires special procedures for their stor-
    age and disposal. It does not unequivocally state that PCBs
    concentrated at levels lower than fifty ppm are safe for human
    exposure. Neither Cincinnati Ins. Co. nor the EPA regulation
    stand for the proposition that PCBs concentrated at forty-nine
    ppm on residential property do not present a substantial endan-
    germent to the health of the residents. That is especially ap-
    parent when we consider that the same set of regulations dis-
    tinguishes between low and high-occupancy areas and re-
    quires that, in high-occupancy areas, bulk PCB remediation
    waste, such as soil, be cleaned up to levels of concentration at
    or below one ppm. § 761.61(a)(4)(i)(A). Section 761.3 confirms
    that the term “high-occupancy area” includes residences. See
    also § 761.123 (regulating spills of PCBs concentrated at fifty
    ppm or greater but emphasizing that “[t]he concentration of
    PCBs spilled is determined by the PCB concentration in the
    material spilled as opposed to the concentration of PCBs in
    the material onto which the PCBs were spilled”). “Proof of
    contamination in excess of [agency] standards may support a
    finding of liability, and may alone suffice for liability in some
    cases, but its required use is without justification in the stat-
    ute.” Interfaith, 
    399 F.3d at 261
    .
    This is not to say that all the plaintiffs must do is to show
    some bit of soil on their property that tests positive for PCBs
    14                                               Nos. 18-1918 & 18-2598
    above one ppm (or even above the purported lower Wiscon-
    sin DNR standard, which the defendants seem to have
    acknowledged in their state-approved clean-up plan). Of
    course, there must be accompanying evidence that establishes
    some connection between the existing contaminants and
    some imminent and substantial endangerment to health. 1 But
    the Liebharts attempted to provide such evidence, and the
    district court held the bar higher than necessary under
    RCRA’s standard. In criticizing expert witness Carpenter’s
    statement that “there is no ‘safe’ level of exposure to PCBs that
    does not increase the risk of disease,” the district court re-
    jected Carpenter’s citation to studies showing the general
    risks of PCB exposure because “the Liebharts do not cite any
    evidence that they have been exposed to PCBs.” Liebhart, 
    2018 WL 1583296
     at *5. Moreover, the district court concluded that
    “[t]he Liebharts do not contend that they can prove an immi-
    nent and substantial danger with evidence of health problems
    they have already suffered.” 
    Id. at *6
    .
    As we noted in Albany Bank, “[i]mminence does not re-
    quire an existing harm, only an ongoing threat of future
    1 On appeal, the Liebharts contend that there is no separate require-
    ment for expert witness testimony because the photos and videos they
    have submitted into evidence suffice to prove their RCRA claim. The de-
    fendants push back on that argument, insisting that many of the issues are
    beyond the competence of lay fact-finders and require the assistance of
    experts to address. See, e.g., C.W. ex rel. Wood v. Textron, Inc., 
    807 F.3d 827
    ,
    838 (7th Cir. 2015) (“Given the complex nature of this case, … [and w]ith
    no experts to prove causation … the appellants cannot prove their toxic-
    tort case under [state] law.”) Because the district court did not make a fac-
    tual finding as to whether this case is sufficient complex to require expert
    testimony, and because we remand for reconsideration of a separate legal
    issue, we need not reach that question today.
    Nos. 18-1918 & 18-2598                                        15
    harm.” 
    310 F.3d at 973
    . Although the Supreme Court has in-
    structed that “[a]n endangerment can only be ‘imminent’ if it
    ‘threaten[s] to occur immediately,’” Meghrig, 
    516 U.S. at 485
    (quoting Webster’s New Int’l Dictionary of English Language
    1245 (2d ed. 1934)), it qualified that statement when it approv-
    ingly quoted the Ninth Circuit’s interpretation that the statu-
    tory term “implies that there must be a threat which is present
    now, although the impact of the threat may not be felt until
    later.” 
    Id. at 486
     (quoting United States Navy, 
    39 F.3d at 1019
    ).
    We take that to mean that the Liebharts must show that there
    are PCBs currently on the property that have the potential to
    substantially threaten their health at some point in the future
    if they continue to occupy the premises and prolong their ex-
    posure. On remand, the district court should reevaluate its ex-
    clusion of Dr. Carpenter’s assertion regarding PCB safety un-
    der the standards we have outlined above and determine
    whether, if admissible, the report demonstrates that a sub-
    stantial and imminent threat to the Liebharts’ health may be
    present.
    B. TSCA Likewise Requires No Heightened Showing
    TSCA authorizes a separate, private cause of action allow-
    ing “any person [to] commence a civil action … against any
    person … who is alleged to be in violation of … any rule
    promulgated under” the Act. 
    15 U.S.C. § 2619
    (a)(1). The EPA
    promulgated the PCB regulations in question pursuant to
    statutory authority under TSCA, designating PCBs as “haz-
    ardous waste” and controlling their manufacture, use, stor-
    age, and disposal. See 40 C.F.R. pt. 761. The Liebharts’ TSCA
    claim alleged that the defendants violated those regulations,
    thereby authorizing the district court to “restrain [the] viola-
    tion.” § 2619(a). Unlike RCRA, which authorizes mandatory
    16                                             Nos. 18-1918 & 18-2598
    injunctions to compel remediation of previous violations,
    TSCA authorizes only prohibitory injunctions to stop ongoing
    violations. Id. The defendants argued that there was no longer
    an ongoing violation, as demolition was complete by the time
    the Liebharts filed their claim. 2
    The purported violation was based on 
    40 C.F.R. § 761.123
    ,
    which, as we noted above, regulates “spills” of PCB materials
    concentrated at levels above fifty ppm. The district court cor-
    rectly noted that the Liebharts had not shown any evidence
    that any PCBs had been “spilled” onto their property (by
    means of dust migration) at that level of concentration, and it
    granted summary judgment to the defendants on that basis.
    But the district court seems to have overlooked the follow-
    ing sentence in the regulation, which directs that “[t]he con-
    centration of PCBs spilled is determined by the PCB concen-
    tration in the material spilled as opposed to the concentration
    of the material onto which the PCBs were spilled.” 
    Id.
     The
    Liebharts’ complaint seems to have alleged that the concrete
    floor of the factory, which contained at least some contami-
    nated areas above the fifty-ppm threshold, was demolished
    and “spilled” onto the Liebharts’ property. By the plain text
    of the regulation, there is no need to show that contaminants
    on the Liebharts’ property are themselves concentrated above
    fifty ppm so long as the original material that was the source
    of that spill met the criteria. On remand, the district court may
    again determine that there is no ongoing violation, but it must
    2 The district court determined that the Liebharts waived this claim
    by failing to engage the defendants’ argument that there was no “ongoing
    violation.” But the court chose to analyze the merits of the claim regardless
    of waiver and reached its conclusion on an alternative basis. We likewise
    set aside the issue of waiver to reach the district court’s merits analysis.
    Nos. 18-1918 & 18-2598                                        17
    first determine whether the alleged violation comes within
    the meaning of § 761.123 in the first place.
    C. The District Court Should Reconsider the Remaining Issues
    on Remand
    Now that we have clarified the standard the plaintiffs
    must meet, we turn to the remaining procedural issues the
    Liebharts have asked to us to address.
    1. The District Court did not Abuse Its Discretion in Excluding
    Woodyard’s Testimony
    “The summary-judgment decision here turned [in large
    part] on the district court’s conclusion that [the] expert testi-
    mony was inadmissible. Whether the district court applied
    the appropriate legal framework for evaluating expert testi-
    mony is reviewed de novo, but the court’s choice of relevant
    factors within that framework and its ultimate conclusion as
    to admissibility are reviewed for abuse of discretion.” Lees v.
    Carthage College, 
    714 F.3d 516
    , 520 (7th Cir. 2013). When a dis-
    trict court is “[f]aced with a proffer of expert scientific testi-
    mony … the trial judge must determine at the outset …
    whether the expert is proposing to testify to (1) scientific
    knowledge that (2) will assist the trier of fact to understand or
    determine a fact in issue.” Daubert v. Merrell Dow Pharm., Inc.,
    
    509 U.S. 579
    , 592 (1993). “The trial court must have … latitude
    in deciding how to test an expert’s reliability.” Kumho Tire Co.,
    Ltd. v. Carmichael, 
    526 U.S. 137
    , 152 (1999).
    The district court was well within its discretion to exclude
    the proffered testimony of expert witness Woodyard. Beyond
    the problem that the plaintiffs seemed to have waived this is-
    sue in the district court by failing to engage with the defend-
    ants’ arguments in their motion to strike the testimony,
    18                                     Nos. 18-1918 & 18-2598
    Woodyard’s analysis suffers from a critical flaw that stems
    from the way in which the parties have framed this lawsuit.
    The district court briefly noted in its opinion that “both sides
    assume that none of the defendants can be held liable for any
    PCB contamination on the Liebharts’ property that occurred
    before the demolition began, so the court will make the same
    assumption.” Liebhart, 
    2018 WL 1583296
     at *1. That’s a curious
    choice. RCRA permits the Liebharts to obtain injunctive relief
    from the owner of the facility for any cognizable contamina-
    tion, regardless of whether the PCBs migrated onto their
    property before or after the demolition occurred. See 
    42 U.S.C. § 6972
    (a)(1)(B) (authorizing suit against “any person … who
    has contributed … to the past or present handling … or dis-
    posal” of hazardous waste); see also Meghrig, 
    516 U.S. at 486
    (“RCRA contains no statute of limitations.”).
    But because the Liebharts restricted their claims to PCBs
    that allegedly migrated onto their property via the dust from
    the 2015 demolition, they necessarily excluded claims result-
    ing from PCBs that may have gotten onto their property dur-
    ing the previous century. The district court correctly noted
    that Woodyard’s expert opinion could not distinguish be-
    tween these two alternatives, as both sets of contaminants
    originated from the same source. There was even evidence
    showing that PCBs existed in the soil beneath the Liebharts’
    asphalt driveway—Woodyard could not explain how that
    might have occurred as the result of dust blowing in the wind
    as opposed to seepage over the course of years before any
    demolition occurred.
    Perhaps the Liebharts decided to frame their claims in this
    way because they wanted to go after defendants TRC and
    Apollo, who would not be liable for what happened before
    Nos. 18-1918 & 18-2598                                           19
    demolition. Or perhaps some element of their state-law
    claims, which we have not addressed, required them to con-
    strict the scope. They did not explain their reasoning to us (or
    it seems, to the district court). But the distinction makes it dif-
    ficult for Woodyard to make his case, given that he did not
    “adequately account[] for obvious alternative explanations.”
    Gopalratnam v. Hewlett-Packard Co., 
    877 F.3d 771
    , 787 (7th Cir.
    2017). Viewed in this light, the district court was within its
    discretion to exclude the testimony as unreliable and unhelp-
    ful to the trier of fact. The district court may choose to rethink
    that evaluation on remand under the legal standards we out-
    lined above, but it may well reach the same conclusion.
    2. The District Court Should Reconsider Its Denial of Injunctive
    Relief
    The district court denied injunctive relief to the Liebharts
    because the defendants had already agreed to a clean-up plan
    that had been approved by the Wisconsin DNR. We review
    that decision for an abuse of discretion. See AMI Int’l, Inc. v.
    Datacard Corp. 
    106 F.3d 1342
    , 1352 (7th Cir. 1997) (remanding
    grant of RCRA injunction).
    As we mentioned above, RCRA authorizes district courts
    to issue either mandatory or prohibitory injunctions, while
    TSCA authorizes only prohibitory injunctions. “[I]t is appro-
    priate ‘to give great deference to the district court’s decision
    as to the precise equitable relief necessary in a particular
    case.’” Bowes v. Ind. Sec. of State, 
    837 F.3d 813
    , 817 (7th Cir.
    2016) (quoting Gjersten v. Bd. Of Election Com’rs for City of Chi-
    cago, 
    791 F.2d 472
    , 479 (7th Cir. 1986)). That is especially true
    when a plaintiff requests a mandatory injunction, which “im-
    poses significant burdens on the defendant and requires care-
    ful consideration of the intrusiveness of the ordered act, as
    20                                      Nos. 18-1918 & 18-2598
    well as the difficulties that may be encountered in supervising
    the enjoined party’s compliance with the court’s order.” Kart-
    man v. State Farm Mut. Auto. Ins. Co., 
    634 F.3d 883
    , 892 (7th Cir.
    2011).
    Considering SPX’s decision to formulate a clean-up plan
    and obtain approval from the state agency, the district court
    determined that there was no need for separate, federally-su-
    pervised remediation. It reached that conclusion even while
    assuming that the defendants were in violation of either
    RCRA or TSCA, despite the fact it found no such violation.
    Other courts have determined that the existence of a parallel
    plan of remediation supervised by the state does not neces-
    sarily prevent a federal district court from granting an injunc-
    tion if it finds the state agency’s actions to be insufficient to
    remedy the violation of federal law. See, e.g., Interfaith, 
    399 F.3d at
    264–68. On the other hand, the same courts have also
    upheld denials of injunctions in similar situations when the
    district court finds that the parallel plan is adequate to the
    task. See Trinity Indus., Inc. v. Chicago Bridge & Iron Co., 
    735 F.3d 131
    , 139–40 (3d Cir. 2013) (distinguishing Interfaith). We
    recently reached the same conclusion. See LAJIM, LLC v. Gen.
    Elec. Co., No. 18-1522, 
    2019 WL 1011021
    , at *4–11 (7th Cir. Mar.
    4, 2019) (“[T]he district court correctly held that it has discre-
    tion to award injunctive relief under the RCRA and is not re-
    quired to order relief after a finding of liability,” particularly
    in light of ongoing relief supervised by a state environmental
    agency).
    Here, the district court determined that SPX’s existing
    plan was sufficient and that the Liebharts had not “iden-
    tif[ied] any way that SPX’s plan [was] deficient or violate[d]
    Nos. 18-1918 & 18-2598                                             21
    federal law.” Liebhart, 
    2018 WL 1583296
     at *7. We agree. Alt-
    hough the Liebharts point to certain statistical sampling re-
    quirements outlined in 
    40 C.F.R. § 761.125
     and contend that
    SPX’s existing plan fails to meet those requirements, the dis-
    trict court noted that SPX’s plan includes further sampling of
    the soil on the Liebharts’ property. It emphasized that “the
    Liebharts do not otherwise explain why SPX’s proposed sam-
    pling scheme is substantively inadequate.” Liebhart, 
    2018 WL 1583296
     at *7. We see no evidence that compels us to contra-
    dict that factual finding.
    However, in light of the legal standards we outlined
    above, we ask the district court to reconsider its decision to
    deny injunctive relief on remand. Because the bar for estab-
    lishing an imminent and substantial danger is lower than the
    district court believed when evaluating the request for an in-
    junction, it would be prudent to reassess whether the DNR-
    approved plan adequately remedies harms that may come
    within RCRA’s scope. See LAJIM, 
    2019 WL 1011021
     at *6
    (“[O]nce a court finds a defendant liable for creating a risk of
    imminent and substantial danger, it will usually be the case
    that injunctive relief is warranted. But that is not always the
    case.”) (internal quotations and citations omitted).
    3. The District Court did not Abuse Its Discretion in Denying
    Leave to Amend the Complaint.
    We review a denial of leave to amend a complaint for
    abuse of discretion. Life Plans, Inc. v. Sec. Life of Denver Ins. Co.,
    
    800 F.3d 343
    , 357 (7th Cir. 2015). District courts are to “freely
    give leave [to amend] when justice so requires.” Fed. R. Civ.
    P. 15(a)(2). “The Supreme Court has interpreted this rule to
    require a district court to allow amendment unless there is a
    good reason—futility, undue delay, undue prejudice, or bad
    22                                     Nos. 18-1918 & 18-2598
    faith—for denying leave to amend.” Life Plans, 800 F.3d at 357
    (citing Foman v. Davis, 
    371 U.S. 178
    , 182 (1962)). The district
    court in this case identified two of those grounds as bases for
    denial: futility and undue delay. While we disagree with the
    futility analysis, we concur with the finding of undue delay
    and decline to reverse.
    We begin with the question of futility. Both statutes con-
    tain advance-notice requirements that citizen plaintiffs must
    observe prior to filing RCRA or TSCA suits. They require
    those plaintiffs to notify the EPA 60–90 days in advance of fil-
    ing the complaint. 
    42 U.S.C. § 6972
    (b)(2); 
    15 U.S.C. § 2619
    (b)(1)(A). But the district court chose to apply the re-
    quirements not only to the filing of the complaint, but also to
    any subsequent amendments that sought to add new RCRA
    or TSCA counts. Although the Liebharts complied with the
    requirements prior to filing their original complaint in April
    2016, they gave no new notice to the EPA before filing for
    leave to amend in February 2018. The district court held that,
    because the prior notice did not contain any mention of bur-
    ied PCBs on the SPX property, it was insufficient to alert the
    EPA to the particular violation the Liebharts sought to include
    in the amended complaint.
    The notice provisions serve two purposes. “First, notice al-
    lows Government agencies to take responsibility for enforc-
    ing environmental regulations, thus obviating the need for
    citizen suits. … Second, notice gives the alleged violator ‘an
    opportunity to bring itself into complete compliance with the
    Act[s] and thus likewise render unnecessary a citizen suit.’”
    Hallstrom v. Tillamook Cty., 
    493 U.S. 20
    , 29 (1989) (quoting
    Gwaltney of Smithfield, Inc. v. Chesapeake Bay Found., Inc., 484
    Nos. 18-1918 & 18-2598                                         
    23 U.S. 49
    , 60 (1987)). The district court’s decision to require no-
    tice for an amendment to a complaint fulfilled neither pur-
    pose. By the time the Liebharts attempted to amend their com-
    plaint, the EPA had been on notice of alleged PCB contamina-
    tion at the SPX property for over two years—and it had de-
    clined to get involved. Moreover, it was unlikely that the de-
    fendants would resolve the alleged violation to avoid being
    sued when they were already in the midst of an extended law-
    suit with the same plaintiffs. See AM Int’l, 
    106 F.3d at 1351
    (“[T]he delay period is designed to allow a [defendant] a pe-
    riod in which to clean up its act and avoid litigation. [This de-
    fendant] was clearly not interested in using the delay period
    to resolve the dispute without going to court.”); see also Dague,
    
    935 F.2d at 1351
     (“There is no need to maintain a window of
    opportunity for the government to take the lead enforcement
    role … when a citizen, acting as a private attorney general, has
    already lawfully assumed the lead role in bringing a … claim
    against the same facility.”) (quoting Dague v. City of Burling-
    ton, 
    733 F. Supp. 23
    , 26 (D. Vt. 1990)). When the original notice
    is “sufficiently specific to inform the alleged violator [and the
    agency] about what it is doing wrong, so that it will know
    what corrective actions will avert a lawsuit,” Atl. States Legal
    Found., Inc. v. Stroh Die Casting Co., 
    116 F.3d 814
    , 819 (7th Cir.
    1994), there is no need to require a second round of advance
    notice for an amended complaint in the same litigation.
    But an error in the futility analysis alone does not neces-
    sarily constitute an abuse of discretion on the whole. In addi-
    tion to futility, the district court cited undue delay and preju-
    dice in its decision to deny leave to amend. “[D]elay by itself
    is normally an insufficient reason to deny a motion for leave
    to amend. Delay must be coupled with some other reason.
    Typically, that reason … is prejudice to the non-moving
    24                                      Nos. 18-1918 & 18-2598
    party.” Dubicz v. Commonwealth Edison Co., 
    377 F.3d 787
    , 793
    (7th Cir. 2004). The district court cited the Liebharts’ admis-
    sion that they learned of the possible burial of contaminated
    concrete on the SPX property on October 11, 2017 but failed
    to seek leave to amend their complaint until February 22,
    2018. During that more than four-month period, the parties
    submitted and briefed their cross-motions for summary judg-
    ment, and by February, trial was only three months away. The
    Liebharts provided no justification for their delay.
    In response, the Liebharts contend that there was no un-
    due prejudice to the defendants: by the time they filed their
    motion, five weeks of discovery still remained. We disagree.
    While the district court’s explanation of prejudice was fairly
    short, even if the district court had failed to articulate a find-
    ing of prejudice altogether, we might still “affirm providing
    that ‘the prejudice that would result from such amendment
    was apparent.’” Park v. City of Chicago, 
    297 F.3d 606
    , 613 (7th
    Cir. 2002) (quoting Feldman v. Am. Mem’l Life Ins. Co., 
    196 F.3d 783
    , 793 (7th Cir. 1999)). In Park, the plaintiff waited six
    months to move for leave to amend a complaint after she
    knew (or should have known) of the additional alleged viola-
    tion. 
    Id.
     Because trial was approaching, we concluded that the
    district court was well within its discretion to deny leave. Id.;
    see also Perrian v. O’Grady, 
    958 F.2d 192
    , 194–95 (7th Cir. 1992)
    (“Because substantive amendments shortly before trial serve
    to defeat the public’s interest in speedy resolution of legal dis-
    putes, ‘[a] district court judge is entitled, in such circum-
    stances, to refuse to allow a plaintiff’s amendment.’” (quoting
    Campbell v. Ingersoll Mill. Mach. Co., 
    893 F.2d 925
    , 927 (7th Cir.
    1990)) (internal citation omitted)).
    Nos. 18-1918 & 18-2598                                                      25
    On the contrary, in Life Plans, we found no undue delay
    when a plaintiff promptly moved to amend its complaint just
    ten days after learning of the factual basis for its new count
    during discovery. 800 F.3d at 358. The Liebharts delayed more
    than four months in the same circumstances. Although dis-
    covery was ongoing at the time of the Liebharts’ motion, the
    parties had already briefed their dispositive motions, and the
    district court was preparing its summary-judgment order that
    would ultimately dispose of the case. We therefore cannot say
    that denial of leave for undue delay and prejudice was an
    abuse of the district court’s discretion. Of course, the district
    court may permit an amendment on remand if the interests of
    justice so require.
    III. CONCLUSION
    Although the district court properly exercised its discre-
    tion on the various evidentiary and procedural issues the
    plaintiffs have raised, its analysis on the merits was narrower
    than the statutes demand. It may reach the same conclusions
    on reconsideration, but the parties should have another op-
    portunity to litigate whether a substantial and imminent en-
    dangerment to health exists in this case under the standards
    we have outlined. We therefore VACATE the order of the dis-
    trict court and REMAND for further proceedings consistent
    with this opinion. 3
    3 The Liebharts also challenge the taxation of costs against them by the
    clerk of the district court. Because we vacate the district court’s judgment,
    we assume that the imposition of costs is automatically vacated and so do
    not reach that issue. The clerk of the district court is free to reassess costs
    on remand as the case proceeds.