The Environmental Protection Agency has announced a set of restrictions that will in effect prevent the development of a controversial copper and gold mine in Alaska which many said would have been disastrous for the state’s largest salmon fishery.

Pebble Mine, located in south-west Alaska near Bristol Bay, would have been one of the largest opencast mines in the world — more than a mile deep, the depth of the Grand Canyon. And the total impact of the mine – from the project itself to the huge waste ponds and piles it would have required – could take up an area the size of Manhattan, according to the EPA. That, the EPA’s regional administrator, Dennis McLerran, said on Friday, was unacceptable for the environment, for those who rely on the salmon in Bristol Bay for work, and for the Native community who have argued that the area is integral to their way of life.



“Bristol Bay is an extraordinary ecosystem that supports an ancient fishing culture and economic powerhouse,” McLerran said in a statement. “The science is clear that mining the Pebble deposit would cause irreversible damage to one of the world’s last intact salmon ecosystems.”



Pebble Partnership, the company set up by the two mining corporations that sought to develop the mine, along with the state of Alaska, sued the EPA in May claiming the agency was overstepping its legal authority by weighing in on the development.



The EPA’s decision on Friday could theoretically be affected by that lawsuit, but many consider the suit a long shot.



Supporters of the mine, who say the EPA is killing the potential for an economic boom in the state, saw Friday’s announcement as an all-out attack on states' rights.



“The EPA is setting a precedent that strips Alaska and all Alaskans of the ability to make decisions on how to develop a healthy economy on their lands,” Senator Lisa Murkowski said. “This [decision] is a blueprint that will be used across the country to stop economic development.”



The agency’s decision does not rule out future development of the mine, but it sets environmental restrictions so burdensome that moving forward with the project would probably be financially untenable. While more action from Pebble Partnership and other supporters of the project is likely, those against the mine viewed the EPA’s announcement as a decisive win.



“This has been looming over us for a decade,” said Alannah Hurley, programme manager for the United Tribes of Bristol Bay, which represents different tribal groups in the area. “For the tribal community, everything that makes us who we are was at stake. For the EPA to recognise that Bristol Bay is worth protecting is huge.”