An effort to remove or cover potentially harmful mercury deposits from the lower Penobscot River will finally begin this year, thanks to a 2022 Maine U.S. District Court consent decree. The mercury is present in river and mudflat sediments from Orrington to Penobscot Bay due to spillage by the HoltraChem Manufacturing Company that occurred from 1967 to the early 1970’s. The chemical builds up in the food chain until it reaches levels in fish and shellfish that are toxic to humans. According to the Bangor Daily News, the lower Penobscot currently contains an estimated nine metric tons of mercury—the highest levels in Maine.

The remediation project will involve capping portions of the mudflats with clean sediment, and removing contaminated soil from other areas. The project is expected to last 10 years, with the goal of lowering mercury concentration to about 400 parts per billion across most of the contaminated area. A pilot project is expected to begin this year to study the effectiveness of the capping strategy.

The court settlement requires Mallinckrodt US LLC, the former owner of HoltraChem, to pay at least $187 million and up to $267 million to trusts that will fund the restoration and remediation efforts.