The successful completion this spring of twin 2.1-mile-long bored tunnels in Seattle marks a literal breakthrough in that city's troubled history of light-rail construction. It also represents the halfway mark in the 3.15-mile, $1.9-billion project to connect downtown with the University of Washington.The 21-ft-dia tunnels run between Capitol Hill and the university. A Traylor Bros. Inc. and Kemper-Frontier Constructors Inc. joint venture worked under a $309-million contract.
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.