Dan Bender, with the La Plata County Sheriff's Office, takes a water sample from the Animas River near Durango, Colo., on Aug. 6, 2015, after the accidental release of an estimated 3 million gallons of waste from the Gold King Mine. Federal officials fear that at least six of the sites examined by The Associated Press could have blowouts like the one at Gold King.

(Jerry McBride/The Durango Herald)