MEMORIAL BRIDGE MAP
Built in a key structural and economic location, the Mike O’Callaghan-Pat Tillman Memorial Bridge had to meet the kinds of challenges that the Hoover Dam (1936) faced almost a hundred years ago when it rerouted the mighty Colorado River. Constructed during the Depression, the dam did not lack for workers, who converged on a magnificent site in the middle of the desert thirty miles from what would become neon Las Vegas, hungry for paying jobs. They built the dam, a sixty-story concrete colossus, and the people came.
The new bridge is also called the Hoover Dam Bypass Bridge because it bypasses U.S. Route 93, which runs on top of the dam. Route 93 had become a dangerous cocktail of heavy highway and commercial traffic mixed with gawking tourists, hairpin turns, and zero visibility, all exacerbated by post-9/11 security concerns. Five U.S. government agencies, led by the Central Federal Lands office of the Federal Highway Administration (CFL-FHWA) developed the new crossing, decades in the planning. Americans have had 80 years to celebrate Hoover Dam’s high-rolling hydroelectric chutzpah. But the lesser-known O’Callaghan-Tillman Bridge is a new player at the public works poker table.
The new bridge inevitably had a hard time competing with a structure that is renowned for its engineering excellence and is considered a wonder of the modern world. The dam, in addition to holding up extremely high structural and aesthetic standards, influenced the design and siting of the new bridge. State Historic Preservation officers from both Arizona and New Mexico emphasized that its design and height had to complement and not compete with the dam, which is approximately 1,500 feet (457 meters) downstream.
MEMORIAL BRIDGE MAP Photo Gallery
After considering the site’s unique topography, extreme wind conditions, and seismic hazards, designer T.Y. Lin devised a twin-rib concrete arch 1,060 feet (323 meters) long, with seven approach spans that range in length from 98 to 121 feet (30 to 37 meters), every element of it distilled from pure engineering reasoning. The composite concrete deck sits 890 feet (271 meters) above the river. Spectacular views of the dam can be seen from the bridge’s pedestrian lane, but only by those who get out of their carsto prevent drivers from slowing down or stopping, the bridge’s side walls are high. With a total length of 1,905 feet (581 meters), it is the longest single-arch bridge in North America.
Three mysterious overpasses, with no on- or off-ramps, were built for the sheep that roam the Black Mountains, home to the largest contiguous herd of desert bighorn sheep. Strategically located underpasses and overpasses near established sheep movement corridors protect herds, and motorists too. Surveillance cameras have captured the sheep enjoying their bespoke crossings. The bridge’s name honors Mike O’Callaghan, a decorated Korean War veteran who served as Nevada’s governor from 1971 to 1979, and Pat Tillman, who opted to abandon his lucrative football career in Arizona to enlist in the U.S.
Army, dying in Afghanistan at age twenty-seven.
Two contractors in California, the Obayashi Corporation and PSM Construction, devised a novel way to construct the bridge. A remote-controlled trolley system, traveling on temporary cables strung between two 330-foot (101-meter) towers, hoisted and positioned each concrete section.
