A Majestic Showcase

This article describes the funding, design and construction of the Mike O’Callaghan-Pat Tillman Memorial Bridge, which straddles the boundary between Arizona and Nevada near the Hoover Dam. Towering nearly 900 ft (274 m) above the Colorado River, the bridge sits atop the world’s tallest precast concrete columns. Its central span -- at 1,060 ft (323 m) long -- is the Western Hemisphere’s longest single-span concrete arch. Although a narrow two-lane highway running across the dam’s crest connected Arizona and Nevada on either side of Black Canyon, this road was a major traffic chokepoint between Las Vegas and Phoenix by the 1980s. The plan to bypass the road has been under development since the late 1980s. Construction of the O’Callaghan-Tillman Bridge -- the largest span of the nine bridges used in the bypass -- began in early 2005. The project required overcoming immense logistic, environmental and weather challenges. Unlike other bridges, which are typically constructed from the ground up, the O’Callaghan-Tillman Bridge was built from the top down. Extensive cabling above the canyon transported materials from one side to the other while workers lowered key components of the bridge into place. The arch of the bridge is flexible and allows the weight of vehicles and the bridge itself to be borne by the canyon walls. The arch was constructed by pouring concrete in place into each of 26 sections, one after the other, until both legs of the arch met in the middle for a closure casting. Arizona and Nevada provided $140 million toward the project’s total cost, while the Federal Highway Administration provided an additional $100 million. The bridge was opened to traffic on October 19, 2010.