Hoover Dam Bypass
From Wikipedia, the free encyclopedia
 |
This article or section contains information about a bridge currently under construction. It may contain information of a speculative nature, and the content may change dramatically and frequently as construction progresses or new information becomes available. |
 |
| Hoover Dam Bypass | |
|---|---|
 An artist's rendering of the bypass showing what the project will look like when it is done sometime in 2010 |
|
| Official name | Mike O'Callaghan-Pat Tillman Memorial Bridge |
| Carries |  U.S. Route 93 |
| Crosses | Colorado River |
| Design | concrete-steel composite arch bridge |
| Longest span | 1,080 feet (329 m) |
| Total length | 1,900 feet (579 m) |
| Height | 890 feet (271 m) |
| Completion date | 2009 (projected) |
| Coordinates | Coordinates: |
Hoover Dam Bypass refers to the construction of the Mike O'Callaghan-Pat Tillman Memorial Bridge and connecting roads for a new route across the Colorado River for U.S. Route 93. The project links the U.S. states of Nevada and Arizona by spanning the Colorado River 1,500 feet downstream from the Hoover Dam. The entire project is expected to be completed by September 2009[1]. Its cost has been estimated to be about $240 million.
The bridge and the new sections of U.S. Highway 93 will be four lanes wide. Total length of the bridge is 1,900 feet (579 m) with a 1,080-foot (329 m) main span. The roadway will be 840 feet (256 m) above the river. When completed, it will be the first concrete-steel composite arch bridge built in the United States.
Pedestrians will be able to park and walk across the bridge for views of Hoover Dam. The dam will not be visible to drivers on the bridge, however[1].
Contents |
[edit] Justification for a new bridge
The bypass and the bridge are being constructed for several different reasons. U.S. Highway 93 is the primary link between Phoenix and Las Vegas, two cities that have seen population explosions since the Hoover Dam's completion. The section of U.S. 93 that approaches and crosses Hoover Dam is inadequate and antiquated. State of the art in 1935 (when the dam was completed), it is one lane in each direction, has many dangerous curves, including several hairpin turns, is narrow, and has poor sight distances.
Combined with sightseeing and pedestrian traffic at the dam, traffic often comes to a standstill. In the wake of the September 11, 2001 attacks, truck traffic over the Hoover Dam has been diverted south to a river crossing near Laughlin, Nevada, in an effort to safeguard the dam from hazardous spills or explosions. This disruption, however, has not eliminated the threat of a possible attack on the dam, as regular traffic can still pass over it. The bypass and the bridge are therefore intended to improve travel times, replace the dangerous roadway, and reduce the threat of an attack or an accident that could potentially happen at the dam site.
More than 17,000 cars and trucks are expected to use the new bridge on a daily basis, a number expected to grow by 50 percent over the next 20 years[1].
[edit] Building the bridge and bypass roads
The largest obstacle to the project is the river crossing itself. The bridge and the bypass are being constructed by a consortium of different government agencies and contractors, among them the Arizona Department of Transportation, the Nevada Department of Transportation, HDR, Inc., T.Y. Lin International, and Sverdrup Civil, Inc.
Construction consists of hoisting workers and up to 50 tons of materials 890 feet above the Colorado River using 2,300-foot-long steel cables held aloft by a pulley-type "high-line" crane system[1].
The arches will be made of 106 pieces -- 53 in each arch -- cast 24 feet at a time[1].
[edit] Milestones
- Mid 2006
- The bridge's construction was in its beginning stages when a permit problem between Clark County and subcontractor Casino Ready Mix arose over the operation of a concrete batch plant for the project.
- April 2007
- The bypass and the bridge were under construction and large cranes were visible near the river when looking from Hoover Dam.
- March 2008
- The approach spans were completed, consisting of seven concrete columns -- five on the Nevada side and two on the Arizona side[1]. The spans will act as the springboard for the remaining segments, with two more cable towers to be built on them to complete construction of the bridge.
[edit] Naming the Bridge
In late 2004, the proposed bridge name honoring Mike O'Callaghan and Pat Tillman was announced at a ceremony by Nevada governor Kenny Guinn and Arizona governor Janet Napolitano. O’Callaghan was a decorated Korean War veteran and was governor of Nevada from 1971 to 1979. He served as executive editor at the Las Vegas Sun newspaper. He suffered a heart attack and died on March 5, 2004. Tillman was an Arizona State University and Arizona Cardinals football player who gave up his multi million-dollar career in the National Football League to enlist in the U.S. Army, and was killed in Afghanistan.
[edit] Setback forces project rescheduling
Strong wind gusts across Black Canyon on September 15, 2006 appear to be the cause for the collapse of four cranes supporting the Aerial tramway used to transport people and materials across the Colorado River. Limited work resumed in October 2006, but the crane collapse caused a two-year construction delay.
Contracting firms Obayashi Corp. and PSM Construction USA Inc. absorbed the cost of rebuilding the cranes, which are now up and running[1].
