The federal government on Monday gave a thumbs up to the Donlin Gold project in southwestern Alaska, issuing major permits for development following an environmental review and drawing a swift rebuke from opposition groups.

The approvals by the Army Corps and Bureau of Land Management followed a six-year environmental review of the project, an open-pit hard rock gold mine that would be built about 10 miles north of the Kuskokwim River community of Crooked Creek, about 275 miles west of Anchorage.

Donlin Gold, owned by NovaGold Resources and Barrick Gold U.S., must still seek scores of individual state and federal permits.

"We still have a ways to go for sure, but today's decision is a really big deal," said Kurt Parkan, a Donlin Gold spokesman.

The agencies selected Donlin's proposed development scenario, they said in a joint decision. The selection rejects other development proposals that sought reduced environmental impact, including not allowing the development at all.

The company expects to produce 33 million ounces of gold over the project's 27-year life. Mining facilities, including a 2,350-acre tailings pond to hold 568 million tons of ground-up waste material, would occupy land owned by The Kuskokwim Corp. and Calista Corp., Alaska Native organizations from the region.

Construction will include development of a 316-mile natural gas pipeline from Cook Inlet, and a 30-mile access road to a port along the Kuskokwim. Barges would haul cargo, supplies and diesel fuel along the river that links to the Bering Sea.

The Corps issued a permit allowing Donlin Gold to place fill material such as gravel into U.S. waters. The agency said an estimated 3,500 acres of wetlands and 226,000 linear feet of streams would be impacted. BLM issued a permit for the pipeline right-of-way over federal lands.

The Corps said Donlin's plan is the least environmentally damaging "practicable" alternative. Donlin must provide "compensatory mitigation" for the impact to U.S. waters, which can include restoring aquatic resources, the agency said in a statement.

Donlin Gold has agreed to give hiring preference to Calista's Alaska Native shareholders, according to the environmental review.

The project would employ an estimated 3,000 people during construction, and 1,200 during operations, Parkan said.

"It will create good-paying jobs to a region of Alaska with historically high unemployment, and we look forward to realizing the many opportunities that the mine will bring to the state of Alaska and the American people," said Interior Secretary Ryan Zinke, in a statement.

Close to a dozen tribal organizations from communities in the region have issued resolutions opposing the project, according to KYUK-AM.

The Yukon-Kuskokwim River Alliance and the tribal government in the city of Bethel, Orutsararmiut Native Council, said in a statement they are "outraged" by Monday's decision. The groups said the agencies ignored voices from the region and could hurt wildlife and subsistence hunters and fishermen.

The environmental review shows potential impacts including increased levels of mercury in air and waterways, damage to salmon habitat and bank erosion, the groups said.

Alissa Nadine Rogers, with the alliance, said the agencies have made a "life-changing decision."

"This is a drastic move on behalf of communities that would be greatly affected by the mine," Rogers said.

Maver Carey, president of The Kuskokwim Corp., said the company helped Donlin Gold and agencies in the permitting process.

"Together, we have gone above and beyond the minimum state and federal requirements to ensure this project protects our lands while economically benefiting our shareholders and region for generations to come," Carey said in a statement from Donlin Gold.

Parkan said the Corps permit will allow construction of roads, the port and pits where rocks will be mined.

He said there was no start date for construction. The company is focused on acquiring remaining permits, a process that will continue in the months ahead.

Parkan said Donlin has taken steps to address the environmental concerns, including by proposing the natural gas pipeline to sharply reduce the amount of diesel fuel heading up the river to power equipment.

Parkan said more than 400 meetings have been held over the years, many in rural communities, with several months of public comment.