Hoover Dam Bypass

Infobox Bridge
bridge_name = Hoover Dam Bypass


caption = An artist's rendering of the bypass, due for completion in September 2009
official_name = Mike O'Callaghan-Pat Tillman Memorial Bridge
carries =
crosses = Colorado River
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design = concrete-steel composite arch bridge
mainspan = convert|1080|ft|m|0
length = convert|1900|ft|m|0
width =
height = convert|890|ft|m|0
load =
clearance =
below =
traffic =
begin =
complete = 2010 (projected)
open =
closed =
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map_

map_text =
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coordinates = coord|36|0|45|N|114|44|29|W|region:US_type:landmark|display=inline,title|name=Hoover Dam Bypass
lat =
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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 convert|1500|ft|m downstream from the Hoover Dam. The entire project is expected to be completed by September 2010. [http://www.lasvegasnow.com/Global/story.asp?S=5990168] 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 convert|1900|ft|m|0 with a convert|1080|ft|m|0|adj=on main span. The roadway will be convert|840|ft|m|0 above the river. When completed, it will be the first so-called concrete-steel composite arch bridge built in the United States. (All concrete arch bridges are reinforced with steel on the inside, and so, they are all made of composites of concrete and steel.)

Pedestrians will be able to park and walk across the bridge for views of Hoover Dam. The dam will not be visible to most drivers on the bridge, however.cite news |first=Francis |last=McCabe |title=Towering Achievement |url=http://www.lvrj.com/news/17150846.html |work=Las Vegas Review-Journal |publisher=Stephens Media Group |date=2008-03-31 |accessdate=2008-04-01 |id=ISSN|1097-1645 |page=1B]

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.

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 Federal Highway Administration, the Arizona Department of Transportation and Nevada Department of Transportation

The master design is by HDR, Inc.. T.Y. Lin International is designing the bridge and Sverdrup Civil, Inc. (the successor to Sverdrup & Parcel that is now a subsidiary of Jacobs Engineering Group) is designing the approaches. [http://www.hdrinc.com/13/38/1/default.aspx?projectID=27 Hoover Dam Bypass - hdrinc.com - Retrieved September 15, 2008] ]

Construction consists of hoisting workers and up to 50 tons of materials convert|890|ft|m above the Colorado River using convert|2300|ft|m|sing=on-long steel cables held aloft by a pulley-type "high-line" crane system.

The arches will be made of 106 pieces -- 53 in each arch -- cast convert|24|ft|m at a time.

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. 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.

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.

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 cranes' collapse caused a two-year construction delay.Contracting firms awarded the reconstruction contract for the cranes to Cincinnati's F&M Mafco inc. F&M sub-contracted with Italian Agudio s.p.A. to supply the aerial tramway (http://www.funiforum.org/funiforum/showthread.php?t=3958 here - Italian site - photos of the cranes and of the building site across the Colorado River)

Contracting firms Obayashi Corp. and PSM Construction USA Inc. (a division of Mitsubishi) absorbed the cost of rebuilding the cranes, which are now up and running.

References

External links

* [http://www.hooverdambypass.org Hoover Dam Bypass]
* [http://enr.construction.com/news/transportation/archives/080220a.asp New Cableway System Set For Hoover Dam Bypass ]
* [http://live8.truelook.com/face/sqface.jsp?name=/hooverdam/bypass&func=live&overlay=default] web-cam on site