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

For nearly 50 years, Maine’s Penobscot River has been contaminated with tons of mercury from a now-shuttered chemical plant in Orrington. 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. So in 2000, NRDC and the Maine People’s Alliance sued Mallinckrodt, a former owner and operator of the plant, to seek a cleanup of the mercury in the river.

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. If approved by the court, the settlement provides that Mallinckrodt will pay at least $187 million, and up to $267 million, to independent trusts that will fund and implement remediation and restoration work. The court held a fairness hearing regarding the proposed settlement on October 1, 4, and 5, 2021 and is reviewing the proposed consent decree to determine whether it is fair, reasonable, and in the public interest. It will only take effect if the court approves it. 

Additional information about the proposed settlement is available in this blog, in this fact sheet, in this public notice regarding the court hearing, and at

Last Updated

October 29, 2021



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