The Enchanted Valley Chalet, located 13 miles from the nearest road, was built as a backcountry lodge in the 1930s, before the creation of the park. More recently, it has been used as a wilderness ranger station and emergency shelter.
Visitors last winter noticed the river had come within 18 inches of the chalet, and recent photographs show the river undercutting the building by about 8 feet. Park Service officials said Monday that an expedited environmental review has been completed, giving them the green light to move the building.
They're worried that if the chalet falls into the river it could harm protected bull trout.
Plans call for moving it away from the river bank before fall rains begin, and then undertaking a more complete study and public review to figure out what to do with the structure long-term.
Officials said they do not yet have details about how and when they will move the chalet.