Hoover Dam Bypass Builders Stick to Old-Style Cableways
Flying high over the Black Canyon, the giant cableways are about to slide into two years of heavy construction for the $114 million bridge slated for a June 2008 opening. One of the “high lines,” as workers call them, has been in service since January, and the second is scheduled for final load testing and commissioning later this month.
Strung between the Nevada and Arizona approaches are two pairs of 3-in.-dia wire cables, each supporting a 13.5-ton trolley and load block assembly. Each block holds a nine-part line of 7⁄8-in.-dia wire rope with a maximum line speed of 400 fpm. The cables hang from two 330-ft-tall lattice-framed towers that can luff, or tilt, 7° laterally in each direction. Backstays and concrete foundations support the towers. The contractor will adjust slack in the cables three times during construction to change hook heights for placing steel tub girders and precast concrete sections that make up the 1,960-ft-long, 88-ft-wide and 277-ft-deep concrete deck arch-type bridge.