A federal judge blocked what would have been the largest timber sale in Alaska’s Tongass National Forest in decades.

Wednesday’s ruling ends the U.S. Forest Service’s plan to open 37.5 square miles of old growth forest on Prince of Wales Island to commercial logging, CoastAlaska reported.

The ruling by Judge Sharon L. Gleason also stops road construction for the planned 15-year project.

Conservationists had already successfully blocked the federal government’s attempt to clear large amounts of timber for sale without identifying specific areas where logging would have occured.

Gleason allowed the forest service to argue in favor of correcting deficiencies in its review and moving forward without throwing out the entire project, but ultimately ruled against the agency.

Gleason’s ruling said the economic harm of invalidating the timber sales did not outweigh “the seriousness of the errors” in the agency’s handling of the project.

The method used in the Prince of Wales Landscape Level Analysis was the first time the agency used it for environmental review on an Alaska timber sale.

The forest service, which can appeal the decision, did not return calls seeking comment.

Gleason’s decision affects the Prince of Wales Island project and the Central Tongass Project near Petersburg and Wrangell.

The ruling triggers a new environmental review under the National Environmental Policy Act, said Meredith Trainor, executive director of the Southeast Alaska Conservation Council.

The ruling in the lawsuit brought by the council includes a requirement for public input on specific areas proposed for logging, Trainor said.

Tess Axelson, executive director of the Alaska Forest Service, said in a statement that the ruling “threatens the viability of Southeast Alaska’s timber industry.”

• This is an Associated Press report.