Federal regulators have issued a draft environmental impact statement saying there are significant benefits to a plan to demolish four massive dams on Northern California’s Klamath River to save imperiled migratory salmon. That sets the stage for the largest dam demolition project in U.S. history. The issuing of the statement Friday by the Federal Energy Regulatory Commission clears a major regulatory hurdle for the project and paves the way for public hearings on the document before a final draft is issued as soon as this Summer. That would allow preparations to begin in earnest for taking down the dams. The aging dams were built before current environmental regulations. An agreement to remove the dams was drafted decades ago between tribal, fishing, agricultural and other interests, but the actual demolition has faced many delays.