Pebble Mine could have devastating environmental consequences on the world's largest sockeye salmon fishery and Southwest Alaska's Bristol Bay region, according to the final scientific assessment report by the US Environmental Protection Agency (EPA).
EPA regional administrator for Region ten Dennis McLerran said large-scale mining poses risks to salmon and the tribal communities that have depended on them for thousands of years.
"The assessment is a technical resource for governments, tribes and the public as we consider how to address the challenges of large-scale mining and ecological protection in the Bristol Bay watershed," McLerran said.
The Pebble project is situated in the Bristol Bay region in south-west Alaska, about 200 miles from Anchorage.
It is a greenfield project based on a copper-gold-molybdenum porphyry deposit, which is considered to be the largest deposit of its kind in the world.
The EPA study revealed that, depending on the size of the mine, up to 94 miles of streams and 5,350 acres of wetlands, lakes and ponds would be destroyed.
According to the EPA estimate, mining activity in the region will reduce the flow of 9 miles to 33 miles of salmon-supporting streams, which could affect the ecosystem's structure and function.
Up to 5,350 acres of wetlands, ponds and lakes would be lost and water would be polluted through billions of tonnes of toxic mine waste, the agency noted.
The project is being developed by the Pebble Limited Partnership (PLP), a 50-50 partnership between Anglo American and an affiliate of Northern Dynasty Minerals.
In September, Anglo American Pebble (AA Pebble) decided to withdraw from the Pebble copper project in Alaska, US.
Alaska Native leaders, commercial fishermen, investors, jewellers and conservation organisations applauded the EPA's report and urged the agency to use its authority under the Clean Water Act to safeguard Bristol Bay and the communities and fishery it supports.
Nunamta Aulukestai chairman Luki Akelkok said: "It's time for the EPA to take immediate steps to protect the fishery, the Alaska Native communities who rely on it as their primary source of food, and the 14,000 jobs that depend on it."
Nunamta Aulukestai is an association of ten Bristol Bay Native Tribes and Native Village Corporations.
Northern Dynasty president and CEO Ron Thiessen said that the publication of the final watershed assessment is the final chapter in a sad story.
"We believe EPA set out to do a flawed analysis of the Pebble project and they certainly succeeded with both their first and second drafts of the BBWA. We have every expectation that the final report released today is more of the same," Thiessen said.
Thiessen also stated that the final BBWA report will affect future development of the Pebble project, as it does not include any recommendations or regulatory actions.
"We look forward to defining a proposed development plan for Pebble and to having it reviewed by federal and state regulatory agencies under the National Environmental Policy Act (NEPA) in the months and years ahead," Thiessen added.
Image: The Pebble project is located in the Bristol Bay region of south-western Alaska.