Crews at the U.S. Energy Dept.’s Hanford nuclear-waste site in Washington state have placed the first of six massive, 50-ton shield doors at the site’s high-level waste treatment facility with a fit no wider than a human hair, say officials of San Francisco-based Bechtel National Inc., design-contractor for the $12.2-billion project on the 560-sq-mile site. Photo: Bechtel National Inc. Crews supervise installation of the first of six 50-ton radiation shield doors at Hanford site. Photo: Bechtel National Inc. The shield door is in a key area of the 65-acre plant complex, which, when completed, will vitrify high-level nuclear waste now
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.