JUNEAU — The U.S. Environmental Protection Agency improperly withdrew proposed restrictions on mining activity in Alaska’s Bristol Bay region, according to a lawsuit filed Tuesday by critics of the proposed Pebble Mine.

The lawsuit is the latest development in the ongoing fight over plans to develop a copper and gold deposit in southwest Alaska.

Opponents of the Pebble Mine worry about the impact it could have on the region known for its salmon habitat, including a prominent sockeye salmon fishery.

The Pebble Limited Partnership, which wants to develop the mine, is seeking approval of a key permit from the U.S. Army Corps of Engineers.

A spokeswoman in the EPA’s regional office said by email that the agency doesn’t comment on pending litigation.

Under the Obama administration, EPA proposed restrictions on development in the Bristol Bay region but never finalized them. The agency looked at three mine scenarios, two of which it said were based on statements made by Northern Dynasty Minerals, the project’s owner.

EPA, at the time, said it had reason to believe that mining of the deposit at any of the sizes it analyzed could result in “significant and unacceptable adverse effects” on streams, wetlands, lakes and ponds and the fisheries they support.

The proposal called for restricting discharge of dredged or fill material into waters that would cause loss of certain amounts of streams or wetlands or streamflow alterations.

A 2017 settlement agreement between EPA and the Pebble partnership called for EPA to initiate a process for withdrawing the proposed restrictions.

But that effort was halted last year, with the EPA saying it had serious concerns about the impacts of mining in the region and wanted more information.

Earlier this year, a memo released by the EPA from its general counsel called for its regional administrator to resume consideration of whether to withdraw the proposed restrictions.

The memo was released shortly before the EPA in July submitted comments on the corps’ draft environmental review, which the regional administrator said likely underestimated impacts the project could have on fish and other resources.

The agency, later that month, announced it was withdrawing the proposed restrictions, saying they were based on hypothetical mine scenarios and outdated now that a mine plan has been submitted. The EPA has said it plans to work with the corps to address its concerns.

The lawsuit alleges EPA has failed to provide a “reasoned explanation” for its change in position.

Mike Heatwole, a spokesman for Pebble, said by email that the Pebble partnership thinks the lawsuit is without merit, “as the EPA acted appropriately.” Pebble partnership CEO Tom Collier has said the proposed restrictions were an overreach.

Plaintiffs in the case are Bristol Bay Native Association, United Tribes of Bristol Bay, Bristol Bay Regional Seafood Development Association, Bristol Bay Reserve Association and Bristol Bay Economic Development Corp.

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• By Becky Bohrer, Associated Press

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