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Friday, October 25, 2013

Hoover Dam Bridge, A New Engineering Marvel



The Hoover Dam Bridge was mandated as a priority one project after 9-11, since the Hoover Dam is the primary conduit between Phoenix and Las Vegas, and a part of the Mexico to Canada Trans-America International Highway. A bridge had been in the planning for decades to alleviate congested traffic slowing national and international traffic between Arizona and Nevada.

(Artist renderings of final bridge above and just below).

Below: The Mike O’Callaghan-Pat Tillman Memorial Bridge as it appeared in June, 2010--taken from air intake inside the dam superstructure (photo Art Lynch)

Below: A view of Hoover Dam from the Mike O’Callaghan-Pat Tillman Memorial Bridge, which will greet pedestrians when it opens in November, and the bridge as it appeared on July 14, 2010. The bridge is due to open this fall, with visitor facilities and footbridge at the bridge opening in November. (credit and link: SAM MORRIS / FILE las Vegas Sun)

Weather changes, high winds, a very real earthquake zone, heavy traffic use and Homeland Security all played a roll in the design and constrution of a structure that required invention, innovation and engineering that had never been put to the test before.

(Suspension is only for during construction, and will be eliminated when structure will be self sustaining upon completion)

Prior to 9-11, truck traffic would cause congestion in Boulder City. This was midway through the Las  Vegas boom, with fewer tourist and locals in both Greater Las Vegas and the booming Phoenix Metro.

A bipass highway was promised, but funding and constuction became a much lower national pririty, so that highway has yet to begin as the bridge nears opening, leading to fears of congestion, crime and pollution for growth limited controlled Boulder City and the wild life reserves of the El Dorado Valley.

The bridge also changes the fact of the dam and historic views. Walls along the highway will make it impossible to see the dam or the views themselves as you cross the bridge, unless you are young enough, strong enough, and willing to take the walking and bike baths below the roadway.



The bridge itself is almost as great a construction wonder as the dam was itself. It will be one of a kind, state of the art, and built far faster than any bridge even approaching its type. The bridge will carry a certain archutectual beauty.

(Frank Crow's Twentieth Century engineering marvel meets 21 century one of a kind specially engineered bridge, seen under construction prior to road section spans and the elmination of suspension supports needed during construction).

A thank you for Nevada SAG member Heart Sharpe and her friend Sharon Lee for the article and photos.



THE WIDER VIEW: Taking shape, the new bridge at the Hoover Dam

Creeping closer inch by inch, 900 feet above the mighty Colorado River , the two sides of a $160 million bridge at the Hoover Dam slowly take shape.

The bridge will carry a new section of US Route 93 past the bottleneck of the old road which can be seen twisting and winding around and across the dam itself.



When complete, it will provide a new link between the states of Nevada and Arizona . In an incredible feat of engineering, the road will be supported on the two massive concrete arches which jut out of the rock face.

The arches are made up of 53 individual sections each 24 feet long which have been cast on-site and are being lifted into place using an improvised high-wire crane strung between temporary steel pylons.



The arches will eventually measure more than 1,000 feet across. At the moment, the structure looks like a traditional suspension bridge. But once the arches are complete, the suspending cables on each side will be removed. Extra vertical columns will then be installed on the arches to carry the road.



The bridge has become known as the Hoover Dam bypass, although it is officially called the Mike O'Callaghan-Pat Tillman Memorial Bridge, after a former governor of Nevada and an American Football player from Arizona who joined the US Army and was killed in Afghanistan.
Work on the bridge started in 2005 and should finish next year. An estimated 17,000 cars and trucks will cross it every day.

The foot bridge access to the new bridge is described in a story in the July 16, 2010 Las Vegas Sun:


The spectacular new observation deck 280 feet above Hoover Dam should be finished in a few months, allowing tourists to get photos that had previously been possible only from a helicopter.
The main purpose of the four-lane Mike O’Callaghan-Pat Tillman Memorial Bridge is to route traffic off the dam, of course. But motorists will find it difficult, if not impossible, to get snapshots of its vertigo-inducing views. That will require using the bridge’s sidewalk.
A final aspect of the $240 million project is pedestrian access.
People who want to walk on the bridge and get its eagle-eye view of the dam and the Colorado River 890 feet below will need to take an exit off U.S. 93 on the Nevada side of the river. The exit will take motorists to the existing road over the dam.
Before the final switchback into the canyon, there will be a turnoff to the right that will lead to a parking lot serving a pedestrian walkway to the bridge.
The lot is to have 65 parking spaces, plus four extra-large spaces to accommodate motor homes and buses.
Just off the parking lot will be a pedestrian plaza, interpretive exhibits and a switchback trail leading to a sidewalk to the bridge. From the parking lot, the trail is about 1,300 feet long on a gentle grade so it will be accessible to people with disabilities. The bridge across the gorge is 1,900 feet long, so a round-trip walk from the parking lot would be just over a mile if one walks all the way across the bridge.
Many people likely will want to do just that. The view “is going to be spectacular,” says Dave Zanetell, a Federal Highway Administration spokesman.




The dam was started in 1931 and used enough concrete to build a road from New York to San Francisco . The stretch of water it created, Lake Mead , is 110 miles long and took six years to fill. The original road was opened at the same time as the famous dam in 1936.

(Areal of Hoover Dam area prior to construction of the bridge).



An extra note: The top of the white band of rock in Lake Mead is the old waterline prior to the drought and development in the Las Vegas area. It is over 100 feet above the current water level.
 
For additional information visit the Federal Bureau of Reclamation, located in the first historic major government buiding at the apex of the city design in Boulder City.

Some of the material above first published in this blog January 22, 2010
Remainder from information gleaned since and from a "Las Vegas Sun" July 16th feature story.

10 comments:

Anonymous said...

Quick note on this article; I was actually able to go to the air duct where picture number 4 was taken. It's also the same one in the movie Chevy Chase Vegas Family Vacation.
Brent Wilson
Com101 4080

Jana said...

Well, I’m not young, but walking across the Hover Dam bypass is one the items on my bucket list! The word choice in the article, such as “built far faster than any bridge…” and “engineering that had never been put to the test before” makes the trip seem dangerous and gives it an adventurous flair!
Jana Hum/114

Lisa Mendez said...

The Hoover Damn is such an amazing place to visit. Our men are super intelligent, brave and strong. I took a tour and some of our men even lost their lives building the damn for us. We go to Arizona often and the new bridge comes in real handy. It saves on time. I just miss the pretty site of the damn. We use to ride under the damn on sea dew's and did you know, there are carp bigger that you and I in the lake.

Anonymous said...

Anthony Chu
I have recently been to the bridge it was truly an amazing site because not only of the unique design but also the walking across it proved to be exciting and very enjoyable.

Anonymous said...

I was able to walk all the way across the bridge a couple of months ago and I was wondering how far I went. Now I know just over a mile! I was the only one in my group to walk the whole distance to see the graffiti on the wall at the end. I wish they had a plaque at the end that said congratulations you are one of the few that made it past all the photographers? tourists taking pictures good job you made it.
It is quite a sight for sure!
Gwen Dennett com 101 sec 4522

Anonymous said...

I have so many memories driving through the Hoover Dam on our road trips as a kid. I am not so excited about the bridge, just because I think it takes the experience away. I will have to drive my kids through before we can no longer use the old way. Thanks for posting.

Jessica Pena

Austin Rains said...

the hoover dam was a engineering marvel I've studdied its creation and what it took to build it and help create the city of Las vegas. the bridge itsself was a masterpiece all the calculations made to make sure the bridge was safe for it people crossing and making sure it did not destroy the natural beauty of the hoover dam and its landscape.

Anonymous said...

Its amazing when you are there and actually see how big everything really is. Its amazing how people can build things like it. I watched on tv when they did the million dollar pour. Thats when they poured the cement for one side of the weight bearing area. Just that was a huge headache.

Devin Murtaugh

Anonymous said...

Coincidentally, I was just talking about this bridge the other day with someone. I am a food server on the strip and one of my tables was from Arizona. They were telling me that the drive over was much better than it had been previously because the traffic going over the Hoover Dam took hours at times, especially since 9/11. They said that this bridge is great and shortened their drive to Vegas considerably. I'm glad this bridge was opened. I'm sure it encourages people to travel and I actually feel more inclined to go to Arizona knowing that their is a more efficient way of going now.

-Jason Mejia (COM-101)

Anonymous said...

Very cool pictures. I have never been to the dam, but i have heard it is one of the coolest views. Very cool to see pictures of it being built!
-N186P