## Facts

- Mallinckrodt, Inc. (as successor to the former plant owner/operator) owned and operated a chlor-alkali facility on the Penobscot River in Orrington, Maine from 1967 to 1982.
- The plant used mercury-cell technology and released mercury-bearing wastes into the environment during its operations.
- Environmental groups alleged mercury contamination persisted downstream in sediments and biota, with risks associated with methylmercury bioaccumulation in fish and wildlife and consequent human exposure.
- The Environmental Protection Agency had previously taken regulatory and administrative actions concerning the site under the Resource Conservation and Recovery Act (RCRA), including requiring studies and certain remedial measures.
- Plaintiffs Maine People’s Alliance and the Natural Resources Defense Council filed a RCRA citizen suit alleging that the mercury contamination “may present an imminent and substantial endangerment” to health or the environment.
- After a bench trial, the district court found liability and ordered Mallinckrodt to fund a comprehensive, court-supervised study of mercury contamination in the Penobscot River and to undertake appropriate remedial measures based on the study’s results.

## Issues

1. Under 42 U.S.C. § 6972(a)(1)(B), what level of proof is required to show that waste “may present an imminent and substantial endangerment” to health or the environment?
2. Whether RCRA citizen suits under § 6972(a)(1)(B) are limited to extraordinary “emergency” situations, particularly when EPA has already acted.
3. Whether the district court exceeded its equitable authority or lacked competence by ordering a complex, phased scientific study and possible remediation.

## Decision

- The First Circuit affirmed the district court’s judgment for plaintiffs.
- The court held that § 6972(a)(1)(B) is satisfied by a reasonable prospect of a serious, near-term threat; proof of actual harm or a certainty of harm is not required.
- The court rejected the view that § 6972(a)(1)(B) is an emergency-only remedy or that citizen enforcement is categorically improper when EPA has taken some prior action.
- The court concluded the district court acted within its equitable discretion in ordering a comprehensive study and structuring potential remediation around the study’s findings.
- The court upheld the district court’s factual findings linking ongoing downstream mercury risks to the plant’s past disposal practices, finding no clear error.

## Legal Principles

- A RCRA citizen suit under 42 U.S.C. § 6972(a)(1)(B) may proceed where there is a reasonable prospect that the defendant’s handling or disposal of solid or hazardous waste may present a serious, near-term threat to health or the environment.
- “Imminent” in § 6972(a)(1)(B) concerns the present existence of a risk that is not speculative; it does not require immediate injury or current manifestation of harm.
- “Substantial endangerment” focuses on the potential seriousness of harm; a lower probability of very severe harm can satisfy the standard.
- Prior or partial agency action does not necessarily bar a citizen suit when unresolved endangerment remains and statutory prerequisites and limitations are satisfied.
- Upon a finding of endangerment under § 6972(a)(1)(B), district courts have broad equitable discretion to order measures reasonably tailored to abate the threat, including investigation, monitoring, and phased remedial actions.

## Conclusion

The First Circuit held that RCRA’s imminent-and-substantial-endangerment citizen-suit provision reaches conditions posing a reasonable prospect of serious near-term harm from mercury contamination and affirmed a remedial order requiring a court-supervised study and potential remediation within the district court’s equitable authority.


Maine People’s Alliance v. Mallinckrodt, Inc., 471 F.3d 277 (1st Cir. 2006)