Persistent water seepage has prompted the contractor of a new “straw” at southern Nevada’s Lake Mead to drill a starter tunnel in a drier direction. Photo: Courtesy of Southern Nevada Water Authority Nevada starter-tunnel route must be changed. The contractor says it is investigating an alternate alignment roughly 20� east from the current 200-ft-long starter tunnel. The plan would be to eventually rejoin the original alignment. Vegas Tunnel Constructors LLC (VTC), a joint venture of S.A. Healy Co., Lombard, Ill., and Impreglio S.p.A., Sesto San Giovanni, Italy, last year encountered water three times in six months while creating a starter
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.