Hoover Dam Bypass Bridge Info: The Story Behind the O'Callaghan-Tillman Memorial Bridge


The construction of the Hoover Dam bypass is considered by many to be one of the most important engineering marvels in modern times. Physical evidence does indeed give weight to the argument: It is the first concrete-steel composite arch bridge built in the United States, as well as being the longest concrete arch in the entire Western Hemisphere. And it is indeed an extraordinary feat of engineering, becoming the second-highest bridge in the U.S. at 890 feet above the Colorado river (the first is the Royal Gorge Bridge in Colorado at 1,053 feet, completed in 1929).

The bypass bridge will also provide a much-needed economic boon to the states of both and Arizona and Nevada. US Highway 93, formerly the primary link between Phoenix and Las Vegas, had been recognized in recent decades as inadequate to modern economic demands.

Built in 1935, U.S. Highway 93 was originally a narrow two-lane highway (one lane in each direction) nested deep in the desert mountains surrounding the Hoover Dam. Driving on it was an exhilarating experience, with dangerous hairpin curves and poor sight distances to contend with. Combine this with over 14,000 daily commuters and tourists from all over the country (if not the world), and it's unsurprising that traffic on the Hoover Dam often resembled a parking lot in the days before the bypass bridge was completed.

So it had been recognized for many years that a more direct route which relieved the horrid congestion was needed. US Route 93 is not just any highway: It is the shortest route between Las Vegas and Phoenix, two of the fastest growing cities in America over the last 50 years. It is a major economic artery, and it was due for a serious overhaul. After determining the optimum bridge location, construction on the Hoover Dam bypass bridge (known today by its official name of "O'Callaghan-Tillman Memorial Bridge") began in earnest early in 2003. It quickly added more than 1200 jobs to the area, employment that would endure for the next seven years, becoming a blessing for two states wracked by economic recession.

Hoover Dam Bypass Construction Begins

Listed below are a few of the key major players, illustrating the truly massive scope of the project:

In 2003, after all necessary planning and environmental work was completed, work begins on the two Approaches (Nevada and Arizona) in both states.

The Nevada Approach

The contract for the Nevada Approach was awarded to Edward Kraemer & Sons, Inc for $30 million USD. Within 2 years, they would go on to acheive success in their role building the new Hoover Dam bypass bridge's Nevada Approach, a massive undertaking in itself: 2.11 miles of new four-lane highway alignment that included six new bridges, a new US 93 traffic interchange, 50,000 square feet of retaining walls, wildlife crossings and a 1.6 mile extension of the River Mountain Loop hiking trail. Construction of those bridges was no small feat either: One of them was a 463-ft-long, three-span, steel-girder structure, crossing a 160-ft-deep ravine. Edward Kraemer & Sons ended up moving over 1.5 million cubic yards of blasted rock (later colored by land reclamation experts Soil Tech with Permeon to make the blasted rock zones appear naturally aged again), adding 2.8 million pounds of reinforcing steel, and pouring over 12,000 cubic yards of concrete as their contribution to the project. The Nevada approach was finally completed after a few delays in November of 2005.

The Arizona Approach

The conctract to construct the Arizona Approach was awarded to both RE Monks Construction and Vastco Inc., and was worth $21.4 million USD. The project involved building a connection between US 93 and the Colorado River Bridge. It also involved constructing a 1.8 mile long four-lane roadway, a 900 ft long bridge, a new traffic interchange to connect to the US 93, wildlife crossings, hiking trail access parking, and new drainage structures. The Arizona Approach Phase was a successful preliminary operation of the Hoover dam bypass construction project, and was finshed right on schedule in December of 2004.

Building the Bridge

The Obayashi Corporation and PSM Construction USA, Inc. were both awarded the contract to build the bridge itself. They had their work cut out for them. Just to begin, 3.5 million cubic yards of earth had to be removed. It required 243 million TONS of concrete and 16 million pounds of steel, which was used to reinforce the concrete. It was built as a composite design: Concrete, one of the strongest, stablest and longest-lasting materials known to man, was used to build the arches which supported the entire structure, while steel was used as the connecting material for the two arches' ribs, as well as for reinforcing the concrete columns that would be used to hold up the actual bridge itself.

The arches, which are the largest in the entire Western Hemisphere, were engineered at the dizzying height of up to 900 ft above the life-giving Colorado River, and built in 24-foot long concrete increments. In terms of safety, every step of the process was treated as a separate engineering component, subjecting each step of the process to rigorous evaluation. And the project was inherently dangerous due to windy condidtions: The high-line crane system which utilized 2,300-foot long steel cables to hoist workers and materials actually collapsed on September 18, 2006 due to high winds in the area, causing a two year delay in the project. Winds of up to 55 mph in Las Vegas Valley that day are attributed by engineers as the cause of the accident, which did not result in any deaths or injuries.

However, the contruction of the Hoover Dam bypass bridge would not be without tradgedy. On Monday, November 24, 2008 Sherman Jones died in a bad construction accident involving the cables that were used to align the temporary concrete towers, the ones that supported the construction of the two arches which supported the bridge. The cause of his death was subsequently found by coroners to be due to blunt-force trauma injuries and ruled accidental.

The bridge would go on to be named after Mike O'Callaghan, a highly decorated Korean War veteran and former governor of Nevada. It was also named after American hero Pat Tillman, an Arizona Cardinals football player who gave up a multi-million dollar career at the NFL to fight in Afghanistan against the Taliban. Pat Tillman was allegedly killed by friendly fire in on April 22, 2004. The circumstances surrounding his death remain a controversey to this day. Members of both the O'Callaghan and Tillman families were present at the opening and dedication ceremonies.

On Thursday, October 14, 2010 the newly named O'Callaghan-Tillman Memorial Bridge was finally complete, and by Tuesday night, October 19, weeks ahead of schedule, traffic commenced to flow on the bridge. According to estimates made by the Federal Highway Administration, the economic impact of not building the bridge would have cost $100 million annually in terms of commuting time saved and gas usage. For decades both states also had to deal with difficulties caused by the occasional accidents which occurred on both sides of the Hoover Dam. This would snarl traffic in between the two states for hours on end, causing untold difficulties for many people for many years. The O'Callaghan-Tillman Memorial Bridge, a modern engineering masterpiece, would finally unravel the plague of congestion in a high-traffic economic zone, ushering in a new era of interstate commerce and partnership between the mighty states of Nevada and Arizona. To see this bridge from breath-taking perspectives, consider these tours to Hoover Dam.