The bridge is the first concrete-steel composite arch bypass built in the country. It rises 270m above the Colorado River. This make it the 7th highest bridge in the world at the time of its construction, but now occupies the 14th position. Its has a length of 579m and span of 323m. Its full name is Mike O’Callaghan–Pat Tillman Memorial Bridge. The project was completed within five years, and there were more than 1200 workers and 300 engineers. Its value is approximately 114 million U.S. dollars.
Bridge like this, bypassing Hoover dam, is unique in its kind facility that requires an innovative approach to design and implementation. Among the factors that affect the overall project are primarily the cost, aesthetics, and the stages of construction as well as the future operation of the facility. The designers and the builders were facing a huge challenge, because there is no other project with similar requirements to invoke.
Idea and project development
Such a major project has a long history of careful planning and research. The first ideas for the bypass road to divert traffic of Hoover dam, are discussed in the mid-60s of the twentieth century. Even then, there was a significant increase in traffic between both Arizona and Nevada. The two-lane highway runs along the arc of the dam and is part of U.S. Highway 93. The plot is tight, heavy and with sharp turns. This creates conditions for numerous accidents. Today hundreds of thousands of tourists visit the complex each year and the number of cars and trucks passing through this route has increased even more over the years, which only confirms the need for a new bypass way that will simultaneously ease the traffic, will shorten travel time and will allow visitors to safely make their Hoover Dam tour.
For twenty years, until 1988, a series of studies on the project and its implementation have been made. There was also a report on a detailed assessment of the environmental impact. Then there was the preparation of the final investment project. It incorporates access road from Arizona with a length of 1,6km and another road from Nevada 3,5km stretch of country like Nevada, and the most important part of the project – a bridge over the Colorado River with a length of approximately 610m , located 450m from the Hoover Dam downstream.
A consortium of companies was formed. It had to undertake the design and implementation. The designers had to deal with the difficult task to analyze and choose the best of the architectural and design standpoint solution for the future bridge.
The preliminary design was approved by the government and the work on it started in 2001. With its location near Hoover dam, the new bridge will be an integral part of the historic center and will be combined in a unique way with one of the most famous engineering feats in the United States. As prescribed in the report , it is requested to minimize the height of the new facility, so the bridge and the dam can be seen clearly from the dam and river level. The goal is complemention, not competition between the two facilities.
The standard approach for a project of such important is to make a detailed analysis of options for the computational scheme of the bridge, given the architectural features and Bills of Quantities for each option. Through 25 years of research, the work of the designers is somewhat relieved. There were discussios for different variations of the bridge. A scoring system was used to report advantages and disadvantages of each of these variations. The option with the highest number of points is the bridge over the Colorado River to be built as an arc. A suspension bridge was the alternative. But it was rejected due to some design flaws, higher initial and operating cost.