Dams Condit Dam Demolition Begins Kiewit Infrastructure West, Vancouver, Wash., breached Washington state's Condit Dam on Oct. 26, beginning the nation's second-largest dam-removal project. The $33-million demolition job will remove the 125-ft-tall concrete structure to meet standards for fish habitats. Kiewit burst a hole in the 90-ft-wide base, which emptied the 92-acre reservoir in two hours. The dam removal, set to begin next spring and wrap up by Aug. 31, will open 33 miles of new spawning grounds for steelhead. With the Glines Canyon (210 ft) and the Elwha River (108 ft), the three largest dam-removal projects in U.S. history
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.