Less than a mile downstream from one of the nation's best-known engineering marvels, the Hoover Dam, a second is taking shape.
A soaring 1,900-foot span across the gorge created by the Colorado River on the Arizona-Nevada border should be completed this fall, eliminating much of a sometimes hourlong bottleneck as traffic creeps over the dam on the key route between Phoenix and Las Vegas.
When it is scheduled to open in November, motorists will cross the longest bridge of its kind in the western hemisphere, with towering concrete columns that rise above a twin rib arch beneath them....
