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Defunct Maine Mine Causing Widespread Contamination

October 17, 2013
Image Caption: The Callahan Mine open pit is seen while it was still active in the 1970s. Credit: Maine Geological Survey

Brett Smith for redOrbit.com – Your Universe Online

New environmental research from Dartmouth College has shown that an open pit mine site in Maine is causing widespread contamination to the nearby area.

Operational during the 1960s and 70s, the Callahan Mine Site is located in Maine’s Goose Pond estuary and is currently being cleaned up by the Environmental Protection Agency (EPA). The report indicates that federal officials may not have known the extent of the damage caused by run-off and seepage from the old mining operations.

The new Dartmouth study, published in the journal Archives of Environmental Contamination and Toxicology, is one of the first to look at the environmental effects of an open pit mine on an estuary and nearby marine food web.

Working as a part of Dartmouth’s Toxic Metal Superfund Research Program, the researchers tested the estuary’s water and sediments. The team also looked at the potential contamination of Atlantic killifish which inhabit the nearby waters. The tiny fish are an important food for larger fish species that are eaten by humans.

The team found prominent levels of copper, zinc, cadmium and lead in the water, sediments and fish. While these results were somewhat predictable, the scientists said were surprised to see high concentrations in certain areas of the marsh – which they took as a sign that metals are continually leaking from mine rubble and residue. Further investigation revealed that the former mining site is still leaking copper, zinc and lead into the Gulf of Maine – and at a rate of seepage that is only exceeded by some areas of Boston Harbor, the scientists said.

The research team said they were unsure how far contamination had spread, but suspected that the region’s fish and birds are being affected. They warned that humans who eat regional seafood could be putting themselves at risk of ingesting mine waste.

The Callahan open-pit mine is the only mining site in an estuary system in the United States. The researchers said the site offers a unique chance to study open-pit mining’s impact on a sensitive environment.

The site’s Goose Pond estuary is a part of Penobscot Bay. The toxic heavy metals that seep into this body of water primarily come from waste rock removed in the process of creating the pit mine and from tailings – the byproduct of the ore extraction process that is typically produced as a slurry, or sediment and water.

To tap the mineral resources beneath the estuary, the Callahan Mining Corp. began by constructing dams at both ends of the pond. This shifted the freshwater that had been flowing into the body of water and blocked a tidal exchange with Penobscot Bay. Between 1968 and 1972, the mining company excavated a 300-foot deep, 1,000-foot wide pit, and removed 800,000 tons of copper and zinc ore. After mining operations had ended, the dam at the Penobscot Bay end of the estuary was opened, allowing tidal flow to resume and the pit filled with water.

Dartmouth’s Toxic Metals Superfund Research Program, which conducted the study and provides relevant information to the EPA, operates under a national ‘Superfund’ umbrella created by Comprehensive Environmental Response, Compensation, and Liability Act of 1980.


Source: Brett Smith for redOrbit.com - Your Universe Online



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