Maine People’s Alliance and NRDC v. HoltraChem Manufacturing Co., LLC, and Mallinckrodt US LLC

For more than 50 years, Maine’s Penobscot River has been contaminated with tons of mercury from a now-shuttered chemical plant in Orrington. But on October 11, 2022—following two decades of legal battles to address the contamination—a federal district court approved a settlement, setting in motion a cleanup plan, long-term monitoring, and funding for projects that will benefit the environment and communities affected by the pollution. Mallinckrodt US LLC, a former owner and operator of the plant, must pay $187 million, and up to $267 million, to independent trusts that will fund and direct these remediation activities.


Mercury in the environment is converted by bacteria into methylmercury, a potent neurotoxin that’s particularly harmful to the developing brain of a child or fetus. In 2000, NRDC and the Maine People’s Alliance sued Mallinckrodt to seek a cleanup of the mercury in the Penobscot River that had persisted for decades.

After a trial in 2002, the federal district court in Maine held that mercury in the Penobscot River could present an imminent and substantial threat to public health and the environment. The judge ordered Mallinckrodt to fund an independent study to determine if remediation was necessary and feasible and, if so, to develop a precise plan to fix the situation. The district court’s decision was upheld on appeal in 2006.

Over nine years, a panel of three mercury experts appointed by the court studied the Penobscot and submitted three reports, all confirming that the river and estuary contain elevated mercury levels, putting wildlife, as well as humans who eat seafood and waterfowl, at risk. Several species, including lobsters, black ducks, eels, and marsh songbirds, were found to have high mercury levels. The panel also concluded that the rate of natural recovery was too slow: it would take 22 to 77 years for mercury levels to be reduced by half in various parts of the Penobscot system, and 106 to 390 years for mercury concentrations to decline to levels similar to natural background concentrations. As a result, the experts recommended establishing a remediation program to evaluate and implement active measures to speed up the river’s recovery. In response to these data, the State of Maine issued a consumption advisory for waterfowl along the lower Penobscot. The state also closed a seven-square-mile portion of the lobster and crab fishery at the mouth of the river and expanded the closure by about five and a half square miles in 2016 after conducting additional sampling.

In June 2014, the federal district court in Maine held a 19-day trial to evaluate the panel’s recommendations. In September 2015, the judge accepted the recommendation to proceed with a remediation study and ordered the appointment of an engineering firm to evaluate and propose potential solutions to clean up the remaining mercury in the Penobscot.

The engineering firm selected by the court in January 2016 evaluated potential remediation options, produced numerous technical reports, and completed its final report and recommendations in September 2018. The engineers recommended that the court order a suite of active remedies to address portions of the Penobscot River. The remedies include dredging, thin layer capping, and long-term monitoring—along with an adaptive management approach that considers additional remedies if the initial remedies are insufficient. The engineering firm maintains a community involvement website to inform the public about its study

On March 19, 2021, NRDC, Maine People’s Alliance, and Mallinckrodt filed a proposed consent decree to settle the case. The Court held a three-day fairness hearing in October 2021 to receive evidence and testimony regarding the proposed settlement, and it officially approved the settlement on October 11, 2022. The settlement provides that Mallinckrodt will pay $187 million, and up to $267 million, to independent trusts that will fund and implement remediation and restoration work. This work will accelerate recovery of the Penobscot and make a real difference for the ecosystem, the fish and wildlife, and the people who rely on them.

Additional information about the settlement is available at More on the ceaseless drive of local advocates and NRDC’s decades-long involvement in our story here.

Last Updated

October 11, 2022



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