Left on its own, the Penobscot River could take 80 years or longer to diffuse the estimated 9 metric tons of mercury spilled into it from a chemical plant in Orrington between 1967 and the early 1970s, according to experts studying the river.
But a 2022 Maine U.S. District Court consent decree could speed up the river’s return to safe water by decades.
The decade-long cleanup will require some of the mercury to be covered and other contaminated sediments to be removed, but scientists must figure out the best areas to do that for the biggest impact. They are getting ready to carry out their plans starting with a pilot project later this year and are seeking input from the public.
What’s at stake is the health of the second-largest river in New England, the fish and animals that rely on it, and the people who use it for food and recreation. Depending on how effective the extensive remediation is, the Penobscot River mercury cleanup could become a model for redressing industrial pollution in other freshwater bodies across the state.
The planned cleanup of the Penobscot River estuary, which contains the highest amount of mercury in a Maine freshwater body, marks a turning point for environmental remediation in state waters: The polluter will pay for the extensive cleanup. Mallinckrodt US LLC, owner of the defunct HoltraChem Manufacturing Co. plant that discharged the mercury, will pay at least $187 million and up to $267 million to trusts that will fund the restoration and remediation efforts.
The court decree also requires the company to pay $20 million for projects in affected communities, including a fish passage at Frankfort Dam and improving water quality at the Penobscot Nation. The plant produced chlorine bleach for paper mills, with mercury being one of the manufacturing chemicals discharged into the river. Before the Clean Water Act of 1972, the dumping was not regulated.
“It’s quite a groundbreaking accomplishment to hold the polluter accountable and have them pay for the cleanup,” said Dianne Kopec, a faculty fellow in the George J. Mitchell Center for Sustainability Solutions at the University of Maine in Orono. Kopec was a staff biologist and data analyst in a study of mercury in the river.
The Maine People’s Alliance and the Natural Resources Defense Council sued the owners of the plant, located on the banks of the river, in 2000, the same year HoltraChem filed for bankruptcy. The judge approved the settlement in 2022. The litigation was the oldest pending case in Maine’s federal courts.
Mercury is a poisonous, naturally occurring chemical element that does not break down in the environment. In a water body it can only be covered or dredged, then moved to a lined pit on land. It is present in all freshwater lakes, ponds and rivers in Maine, which has triggered state regulators to issue consumption warnings about mercury. It is toxic when eaten in contaminated fish and other wildlife.
The Penobscot River — New England’s second-longest river system — is a tidal river, which adds to the challenge of removing mercury. High and low tides and potentially ice floes can move the sediments that contain mercury, once again exposing the toxic chemical.
The plan is to cap areas with several inches of sand. That will be more than the centimeters per year in sediment that the river naturally builds up, which isn’t enough to bury the mercury quickly. Areas being considered for capping are mudflats in coves and other areas between Orrington and North Bucksport that are expected to total about 130 acres.
Even after the planned remediation, the river itself will have to dilute the remaining mercury, with scientists required to monitor water quality and wildlife for up to 45 years.
“Normally a river that is not tidally influenced would, over time, carry things downstream and clean itself out,” said Lauri Gorton, program manager for the Greenfield Penobscot Estuary Remediation Trust, which is responsible for carrying out the measures in the consent decree. “That’s one of the challenges here. It will take such a long time for the river to naturally reduce concentrations because the saltwater continues to push mercury back up and hold it in the estuary.”
Mercury levels in Maine’s fish, loons and eagles are among the highest in North America, according to the Maine Department of Environmental Protection. Most people are exposed to the most toxic form of mercury, methylmercury, by eating fish, waterfowl and game animals. Mercury can impair vision and memory, and can cause tremors and kidney disease, according to the U.S. Centers for Disease Control and Prevention. Methylmercury forms when mercury interacts with organic matter in sediments.
If worms in the sediment eat the methylmercury, and birds or fish eat the worm, the chemical gets into their tissue and builds up over time. That is one of the reasons, Gorton said, that the state has closed areas for fishing, crabbing and lobstering.
The cleanup is welcome news to Chuck Loring, director of the Penobscot Nation Department of Natural Resources. While most of the pollution is south of the Penobscot Indian Island Reservation, migrating fish and birds bring it up the river near them, he said. That has caused nation members to abstain from subsistence fisheries protected by treaty. People also avoided swimming or recreating in the river.
“Our ancestors have survived off the fish and wildlife around the river since time immemorial,” he said. “The environmental tragedy that occurred downstream of us will have lasting effects on the river and its inhabitants.”
Loring said striped bass weighing 10 pounds to 12 pounds each are a newfound source of protein for subsistence fishing in the Penobscot Nation and can feed his family for a couple of meals. Even those carry guidelines for safe eating developed by the Penobscot Nation.
“I can’t feed my daughter all that much from them due to contaminant concerns,” he said. “I also limit my own intake.”
In addition to being a source of food, medicine and spirituality for the Penobscot Nation, the river was important historically for moving lumber, and as a commercial and tourism route from Bangor to Boston, said historian Earle Shettleworth. During the War of 1812, the British were capturing parts of eastern Maine. The state found it needed to better protect Bangor, an important economic center for lumber at the time. Fort Knox was established in 1844 in Prospect to protect against a potential future British invasion, he said.
‘Small levels do build up’
The lower Penobscot River from Veazie to Verona Island has an estimated 9 metric tons of mercury in it — the highest levels in Maine — because of the HoltraChem spillage. But the chemical exists in freshwater bodies across Maine for a different reason: It is carried through the air from coal-fired smokestack emissions, mostly from the Midwest and southern Canadian factories, said Kopec of the University of Maine. It settles into the waters, then builds up in fish, causing statewide warnings from regulators about eating freshwater fish, black ducks and other game, especially for pregnant and nursing women and children under age 8.
Mercury in the air is not as concentrated as in the water, with the discharges from the HoltraChem plant making the Penobscot River highly contaminated, said Josh Paul, air quality program manager with the Penobscot Nation.
“The rainwater falling on your skin isn’t going to affect you, but the long-term effects of mercury in the rainwater do affect surface waters, run from soils into the rivers and collect there, affecting our food chain,” he said. “There wouldn’t be the same short-term effect as a factory dumping into the river, but, long-term, small levels do build up.”
Unlike in the air, mercury in the river can be cleaned up, added Dan Kusnierz, water resources program manager with the Penobscot Nation.
“The widespread mercury that comes from airborne deposition can’t be cleaned up other than to stop it at the source,” he said.
HoltraChem released mercury into the Penobscot River estuary, which runs from the head of tide near Bangor to Fort Point and Cape Jellison in Penobscot Bay, starting in 1967. The lawsuit filed in 2000 asked the court to order an independent study to evaluate the harm from the contamination and require remedial cleanup measures. Several studies were done over more than a decade at a cost of more than $30 million, according to the Natural Resources Defense Council.
Credit: Courtesy of Greenfield Penobscot Estuary Remediation Trust
The studies prompted the Maine Department of Inland Fisheries and Wildlife in 2011 to issue an advisory to pregnant women and young children to not eat waterfowl from the lower Penobscot River, especially black ducks. In 2014 the Maine Department of Marine Resources closed lobster and crab fisheries north of Fort Point State Park in Stockton Springs, and expanded the closed area in 2015.
Mercury released into the river tends to stick to organic matter in the water and sediments, where it is stored. That is especially true in areas of the estuary where particles settle in the mudflats and marshes, including the Frankfort Flats, where the Marsh and Penobscot rivers meet in Frankfort, and the Mendall Marsh area, according to research by Maine Sea Grant.
Most of the mercury was released between 1967 and 1972, when the federal Clean Water Act regulating pollutant discharges was passed, said Kopec of the University of Maine. But initial attempts to reduce it were not always effective, she said. The company created a landfill on the floodplain of the river that was not lined, so mercury waste continued to flow out, especially during storms, she said. The company later created secure landfills for the mercury waste.
Mallinckrodt also separately paid an estimated $130 million to demolish buildings and remove more than 6,000 tons of mercury-contaminated soil on about 60 acres of the 230-acre site on which it operated. The site cleanup, started in 2015, was completed in 2019. It also dredged and placed clean material in a small offshore area near the plant.
The total amount of mercury in the Penobscot River’s sediment ranges up to 2,100 parts per billion, according to a 2023 study of mercury in sediments of Orrington Reach, which stretches from Orrington to North Bucksport. Kopec said the overall goal is to bring mercury concentrations down to about 400 parts per billion across most of the contaminated area.
‘We have to set things right’
The Remediation Trust plans to conduct a year-long, small-scale pilot test starting later in 2024 to see how well capping works in the face of storms, ice floes and other potential disturbances in the river. It is currently getting the necessary permits to conduct the test.
“We want to demonstrate that it’s going to be effective and do it in a way to protect the flats and the benthic environment, the organisms that live in the sediment and the adjacent marshes,” Gorton said.
The final cleanup also will require permits and approvals from landowners adjacent to the intertidal flats, said Cindy Brooks, president of the Greenfield Environmental Trust Group. That group manages the two trusts that will receive Mallinckrodt money, the Remediation Trust and the Beneficial Environmental Projects Trust, the latter funding projects in affected communities. The Remediation Trust plans to hold a public information and update meeting in Frankfort on Aug. 1.
Kopec said that once the mercury problem was identified, it had to be stopped at the source: the plant has stopped producing and is bankrupt. Then the damage needs to be cleaned up, she said.
“You don’t let it sit there,” Kopec said. “We have to set things right.”
Lori Valigra is an investigative environment reporter for the BDN’s Maine Focus team. She may be reached at [email protected]. Support for this reporting is provided by the Unity Foundation and donations by BDN readers.
