An infrastructure superstar21 March 2011
Described as a herculean engineering and construction feat, the Hoover dam bypass bridge was constructed to help safeguard the hydropower dam and its facilities
Spanning the rugged and mountainous Black Canyon and rising high above the Colorado River in the US is an immense roadway of steel, concrete and pavement known as the Mike O’Callaghan-Pat Tillman Memorial Bridge.
Referred to during construction as the Hoover Dam Bypass Bridge, this American infrastructure superstar was orchestrated by the US Department of Transportation, Federal Highway Administration. It is a breathtaking answer to the pragmatic problem of the ageing road system across the Hoover dam. Travel for visitors passing through is improved and security for Hoover dam as a destination point has also been heightened.
Approximately 40 years ago the federal government identified a need to improve Highway 93 near Hoover dam. It wasn’t until some 50 years later in the mid 1990s that the highway was identified as a high priority corridor in the National Highway System Designation Act of 1995. It is the major commercial corridor between the states of Arizona, Nevada and Utah, and on the North American Free Trade Agreement (NAFTA) route between Mexico and Canada.
The traffic congestion caused by the inadequacy of the existing highway across the dam imposed a serious economic burden on the three states. Near the dam traffic experts considered the road to be dangerous due to the number of tight hairpin turns and the high traffic volume.
Safety and security issues were accentuated following the terrorist attacks on 11 September 2001 and tractor-trailer rigs were prohibited from driving across the dam. This forced trucks travelling east and west from Las Vegas to drive across the Colorado River at the bridge connecting the communities of Bullhead City, Arizona, and Laughlin, Nevada, adding about 48km to the route between Las Vegas and Kingman, Arizona.
Purpose and overview
Prior to completion of the bridge, the existing US 93 led travellers of all kinds over Hoover dam to cross the Colorado River. Traffic volumes, combined with the sharp curves of US 93 in the vicinity of Hoover dam created a potentially dangerous situation. Any catastrophe that might occur could potentially: impact innocent tourists and commercial traffic; create millions of dollars of damage to the dam and its facilities; affect the quality and quantity of Lake Mead and the Colorado River; and affect the distribution of power and water supplied by Hoover dam to communities in the southwest.
By developing an alternate crossing of the river near Hoover dam, vehicle and truck traffic are removed from the top of the dam. This new route eliminates the frequent traffic jams of the former highway, along with the old narrow roadways, inadequate shoulders, limited sight distance and low travel speeds.
Public meetings and opportunities for comment about the bridge began in late 1997. During the public comment analysis phase, a variety of environmental factors were closely considered including possible impacts to wildlife, noise, public safety, public service, air quality and traffic circulation. In September 1998 the draft environmental impact statement (DEIS) was completed by the collaboration of the Nevada Department of Transportation (NDOT), the Arizona Department of Transportation (ADOT), the National Park Service (NPS) who manages the nearby Lake Mead Recreation Area, the US Army Corps of Engineers (ACOE), the US Coast Guard (USCG), the US Fish and Wildlife Service (FWS) and dam owner the Bureau of Reclamation. Additionally, there was extensive consultation about wildlife, water quality, construction plans and historic resources with these partners and the US Environmental Protection Agency (EPA) and the State Historic Preservation Offices in Arizona and Nevada.
The construction work began in Arizona and Nevada in 2003 on the roads leading to the future bridge. Construction activities then focused on the bridge and continued through six distinct, yet overlapping phases until its dedication and opening for traffic in October 2010.
Work on the bridge, a herculean engineering and construction feat by any measure, began in 2004 and all aspects of the multi-year project were proceeding on schedule and on budget.
Suddenly in 2007, bridge construction suffered a setback when wind speeds of up to 88km per hour slammed into the site resulting in the downing of strategic cables and the contractors’ tower failure. The state, federal and private partners including suppliers, subcontractors, fabricators, engineers, and insurers got involved in developing, reconditioning, and operating the contractors’ original cable crane system. They also participated in the analysis of the accident. While the joint venture and multi-agency project management team was disappointed by the delay, everyone continued working together safely to advance the project as aggressively as possible in order to achieve the revised completion date in 2010.
The design and construction budget for the bypass bridge was US$240M including US$100M in federal funds, US$20M each from Arizona and Nevada, and US$100M in state bond funds. The construction portion was approximately US$11M.
The bridge opened on 16 October 2010 and soon traffic was flowing normally across the newly opened 579m long bridge, which is supported by a 323m long arch span.