Question of the Day - 26 March 2022

Construction on what would ultimately be called the Mike O'Callaghan–Pat Tillman Memorial Bridge over the Colorado River just downriver from Hoover Dam began in 2003. The challenges were enormous. First, workers and materials had to be hoisted nearly 900 feet above the Colorado on 2,300-foot-long steel cables supported by a pulley-type high-line crane system.

Second, high winds in the canyon hampered efforts, culminating on Friday Sept. 15, 2006, when gusts of up to 100 mph snapped the 2,500-foot-long pulley that spanned Black Canyon. The snapped cable, in turn, toppled the two 300-foot-tall towers on both sides of the canyon that held up the crane system. Luckily, the winds had stopped work on the project, so only a skeleton crew of construction workers was on the site and no one was injured in the mishap.

When the accident occurred, the bypass project was about halfway completed and well on its way toward its original 2008 grand completion date. The accident, however, delayed the project for two years.

In April 2010, all the girders were in place, allowing construction workers to walk from Nevada to Arizona for the first time. Shortly thereafter, the pouring of the bridge deck began. It took another three months for the bridge deck to be paved. The bridge, which wound up costing $240 million, was dedicated on October 14, the grand opening party was held two days later, bicycles and pedestrians started crossing two days after that, and vehicular traffic was finally allowed on October 19, 2010.

It's 1,900 feet long with a 1,080-foot main span, and two lanes of traffic in each direction. It was the first concrete-steel-composite arch bridge ever built in the U.S. Its height of 890 feet qualifies it as the nation’s second highest bridge (the first is the Royal Gorge Bridge in Canon City, Colorado, at 955 feet) and, according to the website highestbridges.com, the 60th highest in the world. The highest is the Beipanjiang Bridge in Dugexiang, Guizhou, China, at 1,854 feet. Interestingly, eight of the world's highest bridges are in China and 56 of the 60 highest are also in China.

By the way, you can still drive across Hoover Dam -- but just to the parking lot and viewpoints on the Arizona side, where all vehicles must turn around and re-enter Nevada to access US 93.