The engineering team charged with taking stock of mercury in the Penobscot River is looking to meet with certain community members and groups as part of a study of possible remediation solutions.

Most of the mercury now sitting at the bottom of the river is believed to have been discharged into between 1967 and 1970 by Mallinckrodt US LLC (then known as International Minerals and Chemical Corp.) from its now-shuttered chlor-alkali plant in Orrington.

Mallincktrodt manufactured chlorine and sodium hydroxide, used to make caustic soda, chlorine bleach and pesticide. In its early years of operation, the plant released "mercury-impacted brine sludge" into waste disposal ponds that then leached into the river.

In 2000, Maine People’s Alliance and the Natural Resources Defense Council brought a lawsuit against Mallinckrodt, alleging violations of the Resource Conservation and Recovery Act. U.S. District Court of Maine in 2003 found Mallinckrodt liable and ordered the company to fund an independent a study of mercury pollution in the river, which resulted in the first two phases of the study, now completed.

In 2014, Maine Department of Marine Resources closed a 7-square-mile area near the mouth of the river to lobster and crab harvesting because of elevated levels of mercury. In 2016, DMR extended the closure to the end of Cape Jellison in Stockton Springs and Perkins Point in Castine. Later that year, the closure was made permanent.

In 2015 a U.S. District Court judge ordered Mallinckrodt to pay for remediation, then estimated at $130 million. The court chose Amec Foster Wheeler, an international engineering firm with an office in Portland, to conduct Phase III of the mercury study.

This phase, dubbed Evaluation of Potential Active Remedies, focuses on 30 miles of the river between the former Veazie Dam site and Fort Point in Stockton Springs. Along the route, the river passes Eddington, Bangor, Brewer, Orrington, Hampden, Winterport, Frankfort, Bucksport, Verona Island, Prospect, Orland, Penobscot and Stockton Springs before opening into Penobscot Bay. The former Mallinckrodt plant site is at roughly the midpoint of the study area.

Phases I and II of the study concluded that mercury concentrations in the river are high enough to pose threats to some wildlife and potentially to human consumers of fish and shellfish.

They also determined that the problem is not going away by itself soon. A 320,000-ton "mobile pool" of contaminated sediment has remained in the river because the mix of salt water from Penobscot Bay pushing up the river creates a wedge that prevents the contaminated sediment from reaching the ocean, the study concluded.

At the current rate of decline, the study group estimated it would take between 106 and 390 years, depending on the location in the river, for mercury concentrations in the main channel to decrease to a safe level for plants and wildlife.

The forecast could be worse in slower-moving areas of the river. Mendall Marsh Wildlife Management Area in Frankfort, a salt marsh that serves as a nursery for fish and wildlife, is shaped in such a way that it could act as a "sediment trap." Maine Department of Inland Fisheries & Wildlife has reported high levels of mercury found in breast meat of black ducks taken from the marsh and has recommended limits for consumption by humans.

Cleanup options could include capping the toxic sediment, dredging the river, or monitoring the river and letting nature take its course. The results of the Phase III engineering study will be submitted to the court in spring 2018, the engineering team's Community Involvement Program Lead, Mary Kelly, said by email June 30.

"The court will then review the information and make decisions on how to proceed," Kelly said. "If the court orders remedial work, it is unlikely that it would begin before 2019."

Kelly will be conducting meetings with interested stakeholders in the study area in mid- to late July 2017. To schedule a time to discuss the Community Involvement Program, contact her by email or by phone, 207-828-2604.

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