Anglo American, the London-based company which owned a 50 percent share in the Pebble Mine project slated for Alaska's Bristol Bay watershed, announced Monday it was pulling out of the venture.While Pebble Mine's original backer, Northern Dynasty Minerals, plans to proceed anyway, the move could hamper a controversial proposed copper and gold mine that has become a lightening rod for environmentalists, fishing interests and several native Alaskan tribes.

Mark Cutifani, Anglo American's chief executive, released a statement Monday saying, "Despite our belief that Pebble is a deposit of rare magnitude and quality, we have taken the decision to withdraw following a thorough assessment of Anglo American’s extensive pipeline of long-dated project options." "Our focus has been to prioritise capital to projects with the highest value and lowest risks within our portfolio, and reduce the capital required to sustain such projects during the pre-approval phases of development as part of a more effective, value-driven capital allocation model,” he added.

The issue of whether to construct the mine — which aims to extract 80 billion pounds of copper, 107 million ounces of gold and 5.6 billion pounds of molybdenum — has dragged on for years, even though Northern Dynasty has not formally filed for federal or state permits to operate it. 

The mine's proponents say it will generate new jobs as well as millions in state and federal revenue; opponents are lobbying the Environmental Protection Agency to block it under the Clean Water Act on the grounds that it could contaminate Bristol Bay and imperil a thriving wild salmon fishery.

The EPA's new administrator, Gina McCarthy, visited the location of the proposed operation to meet with both supporters and critics of the project.Anglo American is not getting out of the deal unscathed: As of June 30, it had funded $541 million of the Pebble project's expenses.

Northern Dynasty CEO Ron Thiessen said his company would push ahead with the project, and aims to begin filing for a permit by the end of the year.“Northern Dynasty will again own 100% of one of the world’s most important copper & gold resources and will have the benefit of $541 million worth of expenditures, which opens the door to a number of exciting possibilities for Northern Dynasty and its shareholders and the Pebble Project and its stakeholders," he said in a statement. 

"Northern Dynasty and the Pebble Partnership have both the expertise and resources necessary to advance the Pebble Project.”Bristol Bay Native Corporation CEO Jason Metrokin, whose shareholders oppose the mine said in a statement, "We are glad that Anglo American has recognized that the proposed mine is too risky, and we urge Northern Dynasty Minerals to do the same.

"Even as he hailed it as "a positive development," however, Metrokin urged the EPA to invoke its Clean Water Act authority "to protect the fishery and water resources of the region and the economic and subsistence values that depend on those resources."