Three of four contractor teams prequalified to bid the second major leg of an $8.7-billion transit tunnel under the Hudson River between New Jersey and Manhattan submitted bids that were opened by the owner, New Jersey Transit, on Dec. 15. The project, to dig 5,200-ft-long twin bored tunnels through New Jersey's Palisades rock formation to a river access point in Hoboken, N.J., had been estimated to cost $250 million. A Secaucus, N.J., joint venture of Schiavone Construction Co., Skanska Civil and J.F. Shea was the low bidder at $258.8 million; a joint venture of OHL USA Inc., Davie, Fla., and
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.