### In the 

# United States Court of Appeals
For the Seventh Circuit

____________________ Nos. 18-1918 & 18-2598

W ILLIAM L IEBHART & N ANCY L IEBHART, Plaintiffs-Appellants

,

v.

SPX C ORPORATION , TRC E NVIRONMENTAL C ORPORATION , & A POLLO D ISMANTLING S ERVICES , I NC

. Defendants-Appellees

.

____________________
Appeals from the United States District Court for the
Western District of Wisconsin.
No. 16-cv-700 — **James D. Peterson**
, Chief Judge

.

____________________

A RGUED D ECEMBER 4, 2018

— D ECIDED M ARCH 6, 2019

____________________

Before B AUER , K ANNE , and B RENNAN , Circuit Judges

.
K ANNE , Circuit Judge . William and Nancy Liebhart together 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 factory, last owned by SPX Corp oration. In 2014, SPX demolished the building with the assistance of TRC Environmental Corporation and Apollo Dismantl ing Services (collectively,2 Nos. 18-1918 & 18-2598

“the defendants”). The Liebharts allege that dust and debris containing toxic chemicals migr ated onto their properties, contaminating their yards and je opardizing their health and the health of their tenants.
The Liebharts sued under federal statutes authorizing private rights of action for environmental contamination. They also brought various state-law claims. Following discovery and the submission of expert witness reports, the districtcourt denied the Liebharts’ motion for partial summary judgment and granted summary judgment to the defendants withcosts. Although the district court adequately evaluated the expert witnesses and did not abuse its discretion in its procedural decisions, the court set the bar unnecessarily high for ȱěȱȱ ȱȱȱȱȱȱȱ Ȭ utes. For that reason, we vacate the district court’s judgment and remand for reconsideration.

**I. B**  **ACKGROUND**The factory dates to the 1920s and was used to manufacture various industrial equipment. Most relevant to our purpose, the factory manufactured power transformers containing polychlorinated biphenyls (PCBs), a carcinogenic chemical banned by the Environmental Protection Agency in 1979.
See Polychlorinated Biphenyls (PCBs) Manufacturing, Processing, Distribution in Commerce, and Use Prohibitions, 44
F ǯȱǯȱřŗǰśŗŚȱǻ¢ȱřŗǰȱŗşŝşǼȱǻ ęȱȱŚŖȱǯǯǯȱ 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 equipment removed, PCB contaminants remained in the facility. InNos. 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. ȱȱ ȱ ȱ ȱ ȱĚȱȱ ȱ ¢ȱ was generally contaminated, wi th concentrated amounts locat ȱȱęȱȱ ȱȱǯ
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 projec t. That November, the defendants timely proposed a self-implementing cleanup plan to the EPA, as required by 40 C.F. R. § 761.61(a). The trouble beganas demolition commenced in January 2015. The Liebharts allege 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 ȱȱȱǰȱȱ¢ȱĴȱȱ of photos and videos of dust from the facility blowing toward their homes to support their allegation. ȱȱęȱȱȱ  th 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 thereafter, a representative of the Wisconsin Department of Natural 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 reside ntial properties . Sure enough, the properties tested positive fo r the presence of PCBs. In August, the Liebharts vacated the property on advice of theirphysician to avoid further exposure to the chemicals. Frustrated with the lack of action, William Liebhart had the snow4 Nos. 18-1918 & 18-2598

sample tested for PCBs. Although the sample did, in fact, contain PCBs, the irregular manner of collection and storage spoiled the sample, and the laboratory declined to endorse the ȱ ȱ¢ȱęǯ
In September 2015 ǰȱȱĴȱȱȱȱȱȱcontamination to the DNR. In turn, the Liebharts sued in federal 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, theLiebharts brought a host of state-law claims under supplemental jurisdiction, including strict liability, negligence, tres- ǰȱǰȱȱȱ Ěȱȱȱǯ
During discovery ǰȱȱȱĴȱȱȱȬ ing for PCBs both in their yard and inside their home. They also underwent blood testing. Although the external surveys revealed a more comprehensive pi cture of the extent to which the soil on the Liebharts’ prop erties contained PCBs, the internal sampling and blood tests were both negative for contamination. 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 Ĵȱȱȱȱȱ¡Ȭ pert witnesses who were to testify at trial. Among those, three ȱȱȱȱ ǯȱǰȱȱȱĴȱ a report by John Woodyard, a li censed professional engineer. His report included a description of standard methods used when demolishing PCB-contamin ated buildings and an analysis of the purported ways in which the defendants deviated from those practices, thereby causing the contamination of theNos. 18-1918 & 18-2598 5

residences. The Liebharts’ second expert was Dr. David Carpenter, a public health physician who opined on ways in which the Liebharts might have been exposed to PCBs and the ȱȱěȱȱȱ¡ǯȱ
ȱȱ that “there is no ‘safe’ level of exposure to PCBs that does not increase the risk of disease.” Finally, the defendants submitted a report prepared by Dr. Russell Keenan, a toxicologistwho analyzed the survey data and determined that it was impossible to determine whether the presence of PCBs on the Liebharts’ property was due to the recent demolition or to ěȱȱȱȱ ȱȱȱ

. In December 2017, the Liebha rts moved for partial summary judgment on the issue of causation, reserving the issue of damages for a jury trial. The defendants cross-moved for summary judgment Dzȱ ¢ȱ ȱęȱ ȱȱ ȱ¡ȱ ȱ ¢ȱȱě ’ experts Woodyard and Carpenter under Fed. R. Evid. 702. In Febr uary 2018, after those motions were fully briefed to the court, the Liebharts sought leave toamend their complaint. In light of the information they obtained through discovery regardin g the burial of concrete on the property, they intended to allege separate RCRA and TSCA violations and seek an en largement of th e proposed injunction 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 ě ’ expert witness reports. The court explained that Woodyard’s report was “equivoc al” as to the issue of causation; it hedged on whether th e contaminants came from dem- ȱ ȱ ȱ ěȱ ȱ ȱ ȱ ǯȱ See Liebhart v. SPX Corp. , No. 16-cv-700-jdp, 2018 WL 1583296 at6 Nos. 18-1918 & 18-2598

*3–4 (W.D. Wis. Mar. 30, 2018). Second, the report “overlook[ed] t ȱȱęȱ ” and failed to account for “obvious alternative expl anations” in determining the cause of the contamination. Id. at *4 (quoting Fed. R. Evid. 702 ¢ȱĴ ’s note to 2000 amendm ents). Finally, the court noted that Woodyard’s report depended on “unreliable or uninformative” evidence, in cluding the Liebharts’ defec- ȱ ȱǰȱ ȱĴȱȱȱȱȱȱ clippings and a chromatogram that allegedly detected PCBs on the property. Id. at *4–5. For those reasons, the court excluded Woodyard’s report in its entirety. Id. at *5. ȱȱȱĴȱȱȱ¢ȱȱǯȱȬ 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 ofPCBs inside the Liebharts’ home and in their blood, suggesting that the Liebharts had not actually been exposed to PCBs ȱȱȱȱȱěȱǯȱ Id. at 5–6. ȱȱ¡ȱ¢ȱěȱȱǰȱȱȱȱ concluded that the Liebharts fa iled to present any admissible evidence to support their RC RA and TSCA claims. The remaining photos and videos certainly showed dust migrating onto the Liebharts’ property, but there was no reliable evidence proving that the dust co ntained 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. ȱȱȱȱ¢ȱȱȱȱě

, 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- ȱȱȱ ȱȱȱěȱȱ the factual basis for the new counts over a year ȱęȱȱ initial complaint, it also noted that they took an additional four months thereafter to seek leave to amend. During that ȱ ǰȱ ȱ ȱ ȱ Ĵȱ ȱ ȱ their motions for summary judgment, and the trial date was fast approaching. It found their petition untimely. Second, thedistrict court determined that the new claims were futile under both statutes' advanc e-notice requirements.

The ěȱ¢ȱ . Several months after the judgment, the clerk of the district court imposed costs onthe Liebharts in the amount of $46,320.02. The Liebharts separately appealed that decision . We consolidated the two appeals and now consider them together.

**II. A**  **NALYSIS**

The ȱȱęȱȱ ȱȱǯȱǰȱthey argue that the district court erred in excluding the opinions of expert witnesses Wood yard in full and Carpenter in part. As part of that argument, they allege that the districtcourt failed to apply the same stringent standard to the defendants’ expert Keenan. Second , they contend that summary judgment was inappropriate beca use, even absent the testi- ¢ȱȱȱ¡ȱ  ǰȱ¢ȱĴȱȱȬ ȱȱęȱȱȱȱȱȱȱȱ RCRA and TSCA. Third, they challenge the district court’s de- ȱȱȱȱȱȱȱęȱ¢ have iden- ęȱȱ ’s state-approved clean-up plan. Fourth, they argue that the district court abused its discretion in denying8 Nos. 18-1918 & 18-2598

leave to amend their complaint. Finally, they challenge the imposition of costs.
But there’s a larger issue l ooming in the background. The district court’s opinion operates under the assumption that ȱ ě s must demonstrate “an imminent and substantial danger with evidence of health problems they have ¢ȱ ěǯ ” Liebhart , 2018 WL 1583296 at *6. Relying primarily on Foster v. United States , 922 F. Supp. 642 (D.D.C. ŗşşŜǼǰȱ ȱ ȱ ȱ ȱ ȱ ȱ ȱ ȱ ȱ ěǰȱholding that “it doesn’t follow necessarily that there is an imminent 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 ques tion 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 ȱȱȱ ȱȱȱȱěȱȱȱȱ make out a prima facie violation of RCRA has led to much discussion among the circuits. We have yet to tackle that issuehead on, so the district court necessarily had to look elsewhere for guidance. Passed in 1976, “RCRA is a comprehensive environmental statute that empowers [the] EPA to regulate hazardous wastes fr om cradle to grave.” City of Chicago v. Envtl. Def. Fund , 511 U.S. 328, 331 (1994). The statute’s “primary purpose ... is to reduce the generation of hazardous waste and to ensure the proper treatment, storage, and disposal 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 enforcing the law, the statute, “like other environmental laws,... contains a citizen suit provision, § 6972, which permits private citizens to enforce its provisions in some circumstances.” Id. at 484. As relevant to this ca se, 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 imminent and substantial endangerment to health or the environment.42 U.S.C. § 6972(a)(1)(B) (emphasis added). Notably, Congress amended the language in 1980 by substituting thephrase “may present” for the original 1976 wording “is presenting.” 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 distri ct 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 Meghrig, 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’ ¢ȱĴȱȱȱȱȱȱ 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 br Ě¢ȱȱ Albany Bank & Trust Co. v. Exxon Mobil Corp. , 310 F.3d 969, 973 (7th Cir. 2002). ǰȱ ȱęȱ ȱ ȱȱ ȱ ȱ prima facie RCRA claim: “a ěȱȱȱǻŗǼȱȱȱȱȱȬ
erated solid or hazardo us waste, (2) that the defendant is contributing to or has contributed to the handling of this waste,and (3) that this waste may present an imminent and substantial danger to health or the environment.” Id. (citing Cox v. City of Dallas , 256 F.3d 281, 282 (5th Cir. 2001)). We then ob- ǰȱȱȱęȱǰȱȱ “[i]mminence does not require an existing harm, on ly an ongoing threat of future harm.” Id. (citing Cox , 256 F.3d at 299). That is the extent of our circuit preceden t on the “may present” language contained in § 6972(a)(1)(B).
But our sister circuits have engaged with this question in ȱǯȱȱȱęȱȱ ȱȱȱǰ the Third Circuit emphasized th at the statute “enhanced thecourts’ traditional equitable powers by authorizing the issuance of injunctions when there is but a risk of harm, a more lenient standard than the trad itional requirement of threatened irreparable harm.” United States v. Price , 688 F.2d 204, 211 (3d Cir. 1982). The court fo und the statutory language “unequivocal,” demonstrating that Congress “intended to ȱȱȱȱȱ¢ȱȱȱĜȱȬ 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. SeeNos. 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 co ntrol pollution only in emergency 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 standard 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- ȱ ǰȱ ȱěȱ ȱ ȱ ȱ ȱ ȱrisk of substantial or serious threatened harm, or some necessity for action.”)).

That error undercuts several of the reasons the districtcourt gave for rejecting the Liebharts’ RCRA claim. For example, the district court cursorily adopted a passing statement we made over twenty- ę years ago that “[t]he [EPA’s] accepted safe level of PCBs in the ȱȱę¢ȱȱȱ million,” id. (quoting Cincinnati Ins. Co. v. Flanders Elec. Motor12 Nos. 18-1918 & 18-2598

Serv., Inc. , 40 F.3d 146, 148 (7th Cir. 1994)), to create a requirement that the Liebharts show th at PCB contamination on their property met that threshold. But there is no requirement in ȱȱȱěȱȱȱ “a particular quantitative showing 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), ě ’d 39 F.3d 1011 (9th ǯȱŗşşŚǼǰȱȱȱȱȱȱěȱȱ ȱ
that “the level of contaminants [was] above levels that are considered acceptable by the State.” But as the Interfaith court noted, the Ninth Circuit’ ȱ ȱ Ĝȱ ȱ ȱ court’s judgment did not disc uss that requirement. RCRA ȱ ȱ ȱ ȱ ě s demonstrate contamination above some agency-derived thre shold level of concentration. 399 F.3d at 260–61. It merely requir es that they show that contaminants 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 endang erment 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 support its contention that contamination below the threshold ȱȱę¢ȱȱȱȱ (“ppm”) does not qualify as a regulatory violation, thereby contradicting Woodyard’s opinion regarding safe levels of PCBs and providing the groundsfor excluding it. In that case, we evaluated whether an insurance company was required to indemnify its insured for damages arising out of PCB contamin ation at an industrial site. ȱȱȱęȱȱȱȱ¢ȱȱȱ the Comprehensive Environmen tal Response, Compensation, and Liability Act of 1980 (CERCLA), 42 U.S.C. § 9601 et seq . InNos. 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’ ȱȱ¢ȱȱȱę¢ȱǯȱŚŖȱ F.3d at 148 (citing 40 C.F.R. § 761.60). ȱ ȱ ǰȱȱȱěȱ ¢ǰȱęȱȬ trial equipment and other wast es contaminated at levels above ę¢ȱ ppm and requires special pr ocedures for their storage and disposal. It does not unequivocally state that PCBs ȱȱȱ ȱȱę¢ȱȱȱȱȱȱ 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 endangerment to the health of the residents. That is especially apparent when we consider that the same set of regulations distinguishes between low and high-occupancy areas and requires 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 ŝŜŗǯřȱęȱ that the term “high-occupanc y area” includes residences. See also § ŝŜŗǯŗŘřȱǻȱȱȱȱȱȱę¢ȱ 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 [a gency] standards may support a ęȱȱ¢ǰȱȱ¢ȱ ȱĜȱȱ¢ȱȱȱ ǰȱȱȱȱȱȱ ȱęȱȱȱ

Ȭ ute.” Interfaith , 399 F.3d at 261.
This is not to say that ȱȱěȱȱȱȱȱ show some bit of soil on their property that tests positive for PCBs14 Nos. 18-1918 & 18-2598

above one ppm (or even above the purported lower Wisconsin DNR standard, which the defendants seem to have acknowledged in their state-a pproved 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 ȱ ȱ Ĵȱ ȱ ȱ ȱ ǰȱ ȱ ȱ 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 thatdoes not increase the risk of disease,” the district court rejected 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 di strict court co ncluded that“[t]he Liebharts do not contend that they can prove an imminent and substantial danger with evidence of health problems ¢ȱȱ¢ȱěǯ ” Id . at *6.

As we noted in Albany Bank, “[i]mminence does not require an existing harm, only an ongoing threat of future

1 On appeal, the Liebharts contend that there is no separate requirement for expert witness testimony because the photos and videos theyhave submitted into evidence suffice to prove their RCRA claim. The defendants 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]ithno experts to prove causation ... the appellants cannot prove their toxictort case under [state] law.”) Because the district court did not make a factual 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 instructed 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 ŗŘŚśȱǻŘȱǯȱŗşřŚǼǼǰȱȱęȱȱȱ ȱȱȬingly quoted the Ninth Circuit’s interpretation that the statutory 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 th e premises and pr olong their exposure. On remand, the district court should reevaluate its exclusion of Dr. Carpenter’s assertion regarding PCB safety under the standards we have ou tlined above and determine whether, if admissible, the re port demonstrates that a substantial and imminent threat to the Liebharts’ health may be present. B. TSCA Likewise Requires No Heightened Showing
TSCA authorizes a separate, pr ivate cause of action allowing “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 “hazardous waste” and controlling their manufacture, use, storage, 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] violation.” § 2619(a). Unlike RCRA, which authorizes mandatory16 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 ȱȱęȱȱǯ 2
The purported violation was based on 40 C.F.R. § 761.123, which, as we noted above, regulates “spills” of PCB materials ȱȱȱȱę¢ȱǯȱ district court correctly noted that the Liebharts had not shown any evidence that any PCBs had been “spilled” onto their property (by means of dust migratio n) at that level of concentration, and it granted summary judgment to th e defendants on that basis.

But the district court seems to have overlooked the following sentence in the regulation, which directs that “[t]he concentration of PCBs spilled is determined by the PCB concentration 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 Ěȱȱ ȱ ¢ǰȱ ȱȱ ȱȱȱȬ ȱ ȱ ȱ ȱę¢ -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 ę¢ȱȱȱȱȱȱȱȱȱ ȱȱȱ 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 analyz e 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

ęȱ ȱ  ȱ ȱ ȱ ȱ ȱ  ȱ the meaning of § 761.123 ȱȱęȱ

. C. The District Court Should Reconsider the Remaining Issues on Remand

 ȱ ȱ  ȱ ȱ ęȱ ȱ standard ȱ ěȱ must meet, we turn to the re maining 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 largepart] on the district court’s conclusion that [the] expert testimony was inadmissible. Whether the district court applied the appropriate legal framework for evaluating expert testimony 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 district court is “[ Ǿȱ ȱȱěȱȱ¡ȱęȱȬ mony ... the trial judge must determine at the outset ... ȱ ȱ ¡ȱ ȱ  ȱ ȱ ¢ȱ ȱ ǻŗǼȱ ęȱ 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 ěȱ¢ȱȱ¡ ȱ ȱ¢ǯȱ¢ȱ ȱȱȱȱě ȱȱȱȱ ȱȱȬsue in the district court by failing to engage with the defendants’ arguments in their motion to strike the testimony,18 Nos. 18-1918 & 18-2598

Woodyard’s analysis s ěȱ ȱ ȱ ȱ Ě ȱ ȱ ȱ from the way in which the parties have framed this lawsuit. ȱȱȱĚ¢ȱȱȱȱȱȱ “both sides assume that none of the defendan ts 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 relieffrom the owner of the facility for any cognizable contamination, 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 ... whohas contributed ... to the past or present handling ... or disposal” of hazardous waste); see also Meghrig , 516 U.S. at 486 (“RCRA contains no stat ute 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 necessari ly excluded claims resulting from PCBs that may ȱĴȱȱȱ¢ȱȬ ing the previous century. The district court correctly notedthat Woodyard’s expert opinion could not distinguish between these two alternatives, as both sets of contaminants originated from the same sour ce. There was even evidence showing that PCBs existed in the soil beneath the Liebharts’ asphalt driveway—Woodyard co uld not explain how that might have occurred as the result of dust blowing in the wind as opposed to seepage over th e 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 beforeNos. 18-1918 & 18-2598 19

demolition. Or perhaps some element of their state-lawclaims, which we have not addressed, required them to constrict the scope. They did not explain their reasoning to us (orit seems, to the district court). But the distinction makes it difęȱ ȱ¢ȱ ȱȱȱǰȱȱ ȱȱȱȱ “adequately account[] for obviou s alternative explanations.” ȱǯȱ
 Ĵ -Packard Co. , 877 F.3d 771, 787 (7th Cir. 2017). Viewed in this light, the district court was within its discretion to exclude the testim ony as unreliable and unhelpful to the trier of fact. The district court may choose to rethinkthat evaluation on remand under the legal standards we outlined above, but it may well reach the same conclusion.
2. The District Court Should Reconsider Its Denial of Injunctive Relief
The district court denied injunc tive relief to the Liebharts because the defendants had already agreed to a clean-up plan that had been approved by th e 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, whileTSCA authorizes only prohibitory injunctions. “[I]t is appropriate ‘to give great deference to the district court’s decision as to the precise equitable reli ef 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 Chicago , 791 F.2d 472, 479 (7th Cir. 1986)). That is especially true ȱȱěȱȱȱ¢ȱǰȱ ȱ “im- ȱęȱȱȱȱȱȱȱȬ ful consideration of the intrusiveness of the ordered act, as20 Nos. 18-1918 & 18-2598

ȱȱȱĜȱȱ¢ȱȱȱ in supervising the enjoined party’s compliance with the court’s order.” Kartman 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 st ate agency, the district court determined that there was no need for separate, federally-supervised 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 necessarily prevent a federal district court from granting an injunc- ȱȱȱęȱ ȱȱ¢ ’ ȱȱ ȱȱĜȱ ȱ 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 ȱ ȱ ęȱ ȱ ȱ ȱ ȱȱ ȱ ȱ ȱ
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 corre ctly held that it has discretion to award injunctive relief under the RCRA and is not re- ȱȱȱȱȱȱęȱȱ¢ǰ ” particularly in light of ongoing relief supervised by a state environmental agency).
Here, the district court determined that SPX’s existing ȱ  ȱ Ĝ and that the Liebharts had not “identif[ied] any way that SPX’ ȱȱǽ ǾȱęȱȱǽǾȱNos. 18-1918 & 18-2598 21

federal law.” Liebhart, 2018 WL 1583296 at *7. We agree. Although the Liebharts point to certain statistical sampling requirements outlined in 40 C. F.R. § 761.125 and contend that SPX’s existing plan fails to m eet those requir ements, the district court noted that SPX’s plan includes further sampling of the soil on the Liebharts’ prop erty. It emphasized that “theLiebharts do not otherwise explain why SPX’s proposed sampling scheme is substantively inadequate.” Liebhart, 2018 WL 1583296 at *7. We see no evidence that compels us to contra- ȱȱȱęǯ
However, in light of the legal standards we outlined above, we ask the district court to reconsider its decision to deny injunctive relief on re mand. Because the bar for establishing an imminent and substantial danger is lower than the district court believed when ev aluating the request for an injunction, it would be prudent to reassess whether the DNRapproved plan adequately remedies harms that may come within RCRA’s scope. See LAJIM, 2019 WL 1011021 at *6 (“[ Ǿȱȱȱęȱȱȱ ȱȱȱȱȱȱ imminent and substantial danger, it will usually be the case that injunctive relief is warranted. But that is not always the case.”) ǻȱȱ ȱȱĴǼǯ
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). Dist rict courts are to “freely give leave [to amend] when justic e 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 bad22 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 ȱȱȱȱęȱ ȱȱȱȱȱȱȱ denial: futility and undue delay. While we disagree with the ¢ȱ¢ǰȱ ȱȱ ȱȱęȱȱȱ¢ȱ
and decline to reverse.
We begin with the question of futility. Both statutes contain advance- ȱȱȱ£ȱěȱȱ ȱ ȱ ȱ ęȱ ȱ ȱ ȱ ǯȱ ¢ȱ ȱ ȱěȱȱ¢ȱȱȱ 60–90 ¢ȱȱȱȱęȬ 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- ȱȱ¢ȱȱȱęȱȱȱǰȱȱȱȱ any subsequent amendments th at sought to add new RCRA or TSCA counts. Although the Liebharts complied with the ȱȱȱęȱȱȱȱȱȱ 2016, they gave no new notice to the EPA before ęȱ ȱ leave to amend in February 2018. The district court held that, because the prior notice did not contain any mention of bur- ȱȱȱȱȱ¢ǰȱȱ ȱĜȱȱȱȱ EPA to the particular violation the Liebharts sought to include in the amended complaint.
The notice provisions serve tw o purposes. “First, notice allows Government agencies to take responsibility for enforcing 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 ¢ȱȱęǰȱ ǯȱ ǯȱȱ¢ȱǯǰȱ ǯ , 484Nos. 18-1918 & 18-2598 23

U.S. 49, 60 (1987)). The district co urt’s decision to require no- ȱ ȱ ȱ ȱ ȱ ȱ ȱ ęȱ ȱ purpose ǯȱ¢ȱȱȱȱȱ ĴȱȱȱȱȬplaint, the EPA had been on notice of alleged PCB contamination at the SPX property for over two years—and it had declined to get involved. Moreover, it was unlikely that the defendants would resolve the alleged violation to avoid being sued when they were already inthe midst of an extended law- ȱ ȱ ȱ ȱ ěǯȱ See AM Int’l , 106 F.3d at 1351(“[T]he delay period is designed to allow a [defendant] a period in which to clean up its act and avoid litigation. [This defendant] was clearly not interest ed 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 ... ȱȱ£ǰȱȱȱȱȱĴ¢ȱǰȱȱ already lawfully assumed the lead role in bringing a ... claim against the same facility.”) (quoting Dague v. City of Burlington , 733 F. Supp. 23, 26 (D. Vt. 1990)). When the original notice
is “ Ĝ¢ȱęȱȱȱ ȱȱȱǽȱȱ 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. Stro h Die Casting Co. , 116 F.3d 814, 819 (7th Cir. 1994), there is no need to requ ire a second round of advance notice for an amended complaint in the same litigation.
But an error in the futility analysis alone does not necessarily constitute an abuse of di scretion on the whole. In addition to futility, the district court cited undue delay and prejudice in its decision to deny leav e to amend. “[D]elay by itself ȱ¢ȱȱĜȱȱȱ¢ȱȱȱȱȱ to amend. Delay must be coupled with some other reason. Typically, that reason ... is prejudice to the non-moving24 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’ admission that they learned of the possible burial of contaminated concrete on the SP X property on Octobe r 11, 2017 but failed to seek leave to amend thei r complaint until February 22, 2018. During that more than fo ur-month period, the parties Ĵȱȱȱȱ -motions for summary judgment, and by February, trial wa s only three months away. The ȱȱȱęȱȱȱ¢ǯ
In response, the Liebharts contend that there was no un- ȱȱȱȱDZȱ¢ȱȱȱ¢ȱęȱȱ ǰȱęȱ  of discovery still remained. We disagree. While the district court’s explanation of prejudice was fairly short, even if the district court had failed ȱȱȱęȬ ing of prejudice altogether, we might still “ Ĝȱȱ that ‘the prejudice that wou ld 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 ǰȱ ȱ ěȱ  ȱ ¡ȱ months to move for leave to amend a complaint after sheknew (or should have known) of the additional alleged violation. 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 serveto defeat the public’s interest in speedy resolution of legal disputes, ‘[a] district court judge is entitled, in such circum- ǰȱȱȱȱ ȱȱě ’s amendment.’” (quoting Campbell v. Ingersoll Mill. Mach. Co. , 893 F.2d 925, 927 (7th Cir. 1990)) ǻȱȱĴǼ ).Nos. 18-1918 & 18-2598 25

On the contrary, in Life Plans , we found no undue delay ȱȱěȱ¢ȱȱ ȱȱȱȱȱ ten days after learning of the factual basis for its new count during discovery. 800 F.3d at 358. The Liebharts delayed morethan four months in the same circumstances. Although discovery 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. C**  **ONCLUSION**Although the district court properly exercised its discretion on the various evidentiary and procedural issues the ěȱȱ aised, its analysis on the merits was narrower than the statutes demand. It may reach the same conclusionson reconsideration, but the parties should have another opportunity to litigate whether a substantial and imminent endangerment to health exists in this case under the standards we have outlined. We therefor e VACATE the order of the district 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.