Environment Carefully Deconstructing Dams in Washington State. November 30, 2005 Scientists are trying to figure out how best to remove two large, century-old dams on the Elwha River in Washington state. Removing a dam, especially a big one, is not simple. It can release huge amounts of sediment and actually worsen the river's ecology. These are the largest dams ever slated for removal in the United States.