A river snakes through vast wild lands near Gates of the Arctic National Park and Preserve, Alaska in Sept. 2022. Bonnie Jo Mount/The Washington Post

A road critical to operating a proposed open-pit mine in a remote part of Alaska hit a new hurdle Friday when the Biden administration issued a finding that the road could threaten Alaska Native communities and their lifestyle more than previously estimated.

The Interior Department analysis is not a final decision on the fate of Ambler Road, one of the most high-profile environmental issues in the state. But it poses a setback for a planned 211-mile transportation corridor that would run through one of the largest roadless areas in the country – intersecting Gates of the Arctic National Park – to help a mining company access an estimated $7.5 billion worth of copper north of the Arctic Circle.

Originally approved under former president Donald Trump, the road right of way was suspended by the Biden administration last year. The Interior Department said it found “significant deficiencies” in the prior environmental review and ordered additional analysis.

The draft version of that analysis has now found 66 communities where subsistence-style living activities could be affected, up from 27 communities in the last analysis, released in 2020, Interior’s Bureau of Land Management said in a news release. Nearly half could face significant impacts because of the road, the agency added. The review also updated the potential effects of the road on caribou and fish.

“Subsistence use would be altered by the presence of a road, both because a road would affect wildlife behavior and because it would bisect travel routes used by hunters and affect their access to subsistence use areas,” the supplemental review says.

It further found all the options for a road would fragment wildlife habitat, altering the movement and migration of caribou and other animals – partly because of vehicle noise – although some proposals would have more impact than others. With caribou already under pressure from other development and climate change, the road could affect calving and survival rates, the analysis says.

The agency’s Alaska state director said the review includes more robust input from talks with Alaska Native groups. “Continued public input and engagement on this draft is critical to ensuring our analysis captures the proposed road’s potential impacts,” the director, Steve Cohn, said in a statement.

While not final, the findings raise even more questions about a project that many environmental groups oppose, and some administration officials are concerned about. The administration is due to publish a final analysis and then a subsequent final decision roughly next spring.

Executives at the mining venture Ambler Metals are planning to review the findings, the company said in a statement. It said the project is an “urgent” necessity for supplying domestic minerals that can support U.S. national security and clean-energy technology to address climate change.

“Ambler Metals and our partners are confident we can address any issues raised,” Ramzi Fawaz, the company’s chief executive, said in the statement. “This project has been unnecessarily bogged down in federal bureaucracy for years and I urge the Department of the Interior to avoid any further delays.”

The new review also angered mining advocates because it factored in potential impacts from public use of the road, even though the corridor wouldn’t be open to the public under the current proposal. Some members of the public expressed concern that the road might someday end up opened to the broader public, and the analysis concluded that “public use and trespass are reasonably expected,” and should be considered.

While the project has support from some locals, others oppose it, and blocking it is one of the top priorities of national park advocates. To reach the mine site, the road would cross 11 major rivers and hundreds of streams, breaking apart unspoiled tundra and caribou migration paths. It also would cross 26 miles of Gates of the Arctic National Park and Preserve and sit close to Kobuk Valley National Park.

“It is good see the Biden administration looking carefully at the actual costs of this bad idea,” Alex Johnson, Arctic and Interior Alaska campaign director for the National Parks Conservation Association, said in a statement.

“The international mining companies who are pushing this project have yet to prove there are viable amounts of critical minerals in this region to justify the economics of the project, let alone permanently alter one of the last remaining wild landscapes on Earth.”