| Mike O'Callaghan – Pat Tillman Memorial Bridge | |
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The bridge as seen from the Hoover Dam |
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| Official name | Mike O'Callaghan – Pat Tillman Memorial Bridge |
| Other name(s) | Hoover Dam Bypass Bridge |
| Carries | U.S. Route 93 |
| Crosses | Colorado River |
| Locale | Lake Mead National Recreation Area, Clark County, Nevada – Mohave County, Arizona |
| Maintained by | Arizona Department of Transportation (ADOT) Nevada Department of Transportation (NDOT) |
| Designer | T. Y. Lin International |
| Design | concrete-steel composite arch bridge |
| Total length | 1,900 feet (579 m)[1] |
| Longest span | 1,060 ft (320 m)[1] |
| Clearance below | 900 ft (270 m)[1][lower-alpha 1] |
| Construction begin | February 14, 2005 |
| Construction end | October 14, 2010[2] |
| Construction cost | $240 million |
| Opened | October 16, 2010 (to pedestrians);[2] October 19, 2010 (regular traffic)[3] |
| Daily traffic | 15,000 |
The Mike O'Callaghan – Pat Tillman Memorial Bridge, the key component to the Hoover Dam Bypass project, was the first concrete-steel composite arch bridge built in the United States, and it incorporates the widest concrete arch in the Western Hemisphere. Opened on October 19, 2010, this four-lane highway bridge provides a crossing of the Colorado River for U.S. Route 93, linking Nevada with Arizona about 1,600 feet (about 500 meters) downstream from the Hoover Dam. This bridge is located about 30 miles (48 kilometers) southeast of Las Vegas, Nevada. At 840 feet (260 meters) above the Colorado River, this bridge is the second-highest in the United States, following the Royal Gorge Bridge. Built as part of the Hoover Dam Bypass Project, which was successfully completed within budget at a cost of $240 million, the bridge portion cost $114 million (2010 prices).[4]
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The bypass was constructed to improve safety, security, and traffic capacity.[5] Through extensive studies, this bridge route was determined to be the best route for the bypass.
U.S. Highway 93, in conjunction with U.S. Highway 60 via Wickenburg, Arizona, is the primary highway between Phoenix, Arizona, and Las Vegas, Nevada, two cities that have seen great increases in population since the completion of the Hoover Dam. The section of U.S. 93 that approached and crossed Hoover Dam was not adequate for modern traffic needs. It was too narrow, with just one lane in each direction, it had many dangerous curves, including several hairpin turns, and it had poor lines-of-sight, especially at night.
Through highway traffic combined with sightseeing and pedestrian traffic at the dam, the traffic often came to a standstill. As a consequence of the heightened security measures following the September 11, 2001, attacks, truck traffic over the Hoover Dam was diverted south to a bridge crossing the river at Laughlin, Nevada, in an effort to safeguard the dam from hazardous spills or explosions. This disruption, however, did not eliminate the threat of a possible attack on the dam, since regular traffic still passed over it. Hence, the new bypass and the bridge are intended to improve travel times, replace the dangerous roadway, and reduce the possibility of an attack or an accident at the site of the dam.
More than 17,000 cars and trucks are using the new bridge daily, a number expected to grow by 50 percent over the next 20 years.[6] This bridge is a key component of the proposed Interstate 11 project.[7]
Planning and environmental work was completed and the environmental impact statement issued in July 1988. The design of the preferred alternative started in July 2001.[8] Project design was by the Hoover Support team, led by HDR, Inc. and including T.Y. Lin International, Sverdrup Civil, Inc., and other specialist contributors.[9]
The bridge has a length of 1,900 feet (579 m) and a 1,060 ft (320 m) span.[1] The roadway is 900 ft (270 m)[1] above the Colorado River and four lanes wide.[9] This is the first concrete-and-steel composite arch bridge built in the United States. It includes the widest concrete arch in the Western Hemisphere and is also the second highest bridge in the nation, with the arch 840 ft (260 m) above the river.[10] The twin arch ribs are connected by steel struts.[11]
The composite design, using concrete for the arch and columns with steel construction for the roadway deck, was selected for schedule and cost control while being aesthetically compatible with the Hoover Dam.[11][12] Sean Holstege in The Arizona Republic has called the bridge "an American triumph".[13] USA Today called it "America's Newest Wonder" on October 18, 2010.[10]
Pedestrian access is provided over the bridge to tourists who wish to take in a different view of the nearby dam and river below, but the dam is not visible for those driving across it. A parking area is provided near the bridge on the Nevada side at what was a staging area during construction. A set of stairs and disabled access ramps lead to the sidewalk across the bridge.[6]
Work began in 2003 on the approaches in both states[14] and the construction contract for the arch bridge was awarded in October 2004.[8] The largest obstacle to the project was the river crossing. The bridge and the bypass were constructed by a consortium of different government agencies and contractors, among them the Federal Highway Administration, the Arizona Department of Transportation, and Nevada Department of Transportation, with RE Monks Construction and Vastco, Inc, constructing the Arizona Approach, Edward Kraemer & Sons, Inc, the Nevada Approach and Las Vegas Paving Corporation undertaking the roadway surfacing on both approaches. The bridge itself was built by Obayashi Corporation and PSM Construction USA, Inc., while Frehner Construction Company, Inc. was responsible for completing the final roadway installations.[3] A permit problem between Clark County and the subcontractor Casino Ready Mix arose in May 2006 over the operation of a concrete-batch plant for the project, and this caused a four-month delay.[8][15]
Construction required hoisting workers and up to 50 short tons (45 t) of materials 890 feet (270 m) above the Colorado River using 2,300 ft (700 m)-long steel cables held aloft by a "high-line" crane system.[6] High winds caused a cableway failure in September 2006, resulting in a further two year delay.[8] The approach spans, consisting of seven pairs of concrete columns—five on the Nevada side and two on the Arizona side—were completed in March 2008.[6] In November 2008, the construction worker Sherman Jones died in an accident.[8]
The arches are made of 106 pieces—53 per arch—mostly cast in place 24 ft (7.3 m).[6] The arch was constructed from both sides of the bridge concurrently, supported by diagonal cable stays strung from temporary towers. The concrete arch was 50 percent completed in May 2009. and the twin arch spans were completed with the casting of the center segments in the following August.[8] When the two halves of the arch were completed in August 2009, they were only 3⁄8 inches (9.5 mm) apart, and the gap was filled with a block of reinforced concrete.[16] The temporary cable stays were removed, leaving the arch self-supporting. By December, all eight of the vertical piers on the arch had been set and capped, and at the end of the month the first two of thirty-six 50-short-ton (45 t) steel girders had been set into place.[17]
By mid-April 2010, all of the girders were set in place, and for the first time construction crews could walk across the structure from Arizona to Nevada. Shortly thereafter, the pouring of the bridge deck began. The bridge deck was fully paved in July, and the high-line cranes were removed from the site as the overall project neared completion. The bridge was completed with a dedication ceremony on October 14, 2010.[18] and a grand opening party on October 16.[19] It was opened to bicycle and pedestrian traffic on October 18[20][21] and to vehicular traffic on October 19,[3] a few weeks earlier than estimated.[22] The building of the bridge was featured in episode 5x02 of the TV series Extreme Engineering. The filming of this episode took place before the start of work on the arch.
In late 2004, the proposed bridge name honoring Mike O'Callaghan and Pat Tillman was announced at a ceremony by the Governor of Nevada, Kenny Guinn, and the Governor of Arizona, Janet Napolitano. O’Callaghan, a decorated Korean War veteran, was the Governor of Nevada from 1971 through 1979, and he was the executive editor at the Las Vegas Sun newspaper for many years until his death on March 5, 2004. Tillman had been a football player for the Arizona State University team and for the Arizona Cardinals team. He gave up his multimillion dollar career in the National Football League to enlist as an infantryman in the U.S. Army, but he was killed by friendly fire in Afghanistan[23] on April 22, 2004.
Strong winds gusting across the Black Canyon on September 15, 2006, appear to have been the cause for the collapse of the "high-line" crane system that was used to carry workmen and materials at the bridge site. No injuries or fatalities occurred because of this accident. Limited construction work resumed in October 2006, but this accident caused a two-year delay in construction.
The bridge-construction companies Obayashi Corp. and PSM Construction, USA, Inc. absorbed the cost of the debris removal and the rebuilding of the cranes.[6][24] The reconstruction contract for the cranes was awarded to Cincinnati's F&M Mafco Inc.
Work was also halted when a Las Vegas construction worker, 48-year-old Sherman Jones, was killed during construction while adjusting a cable used to align temporary concrete towers, when a jack punctured his chest.[25][26] The Obayashi Corporation then resisted efforts for an investigation by the Occupational Safety and Health Administration, a regular practice that they had adopted following workers' deaths in California, Washington State, and elsewhere.[27]
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