Revisiting the Bridge at Hoover Dam

Reviewing past posts, there are quite a few about construction and building topics.  I suppose that’s appropriate – these days I make my living as a construction executive after all, and I’ve done good time at a couple of major architecture and construction firms over the years.  Those facts put the little encounter I had yesterday at the office into perspective.

In 2013, Mary and I combined a work trip to Las Vegas with a drive up to the Grand Canyon.  On the way, we made a point of stopping at the Hoover Dam for the tour (see this post), and for a walk across the new bridge.  It turns out that one of my work colleagues (an engineer who works as a construction project manager) had some aerial photos that had been taken during the construction of the bridge, and he shared them, so I thought I’d make them the topic of today’s blog post.

If you’re familiar with the construction of many highway bridges in the west, they are often concrete arches, as is this one.  What I didn’t realize until now is that the concrete is cast in situ – forms are constructed and the concrete is poured into them at the job site in the position that it is to be used.  That makes for some fascinating process photos, as shown in the accompanying images…I’ll let them speak for themselves.

Inside Hoover Dam (aka - The Dam Tour)

This is only one side of the turbine room.

After we had a look at the new bypass bridge and looked down at Hoover Dam from a height of around 900 feet, we continued down the serpentine access road to check out this incredible engineering achievement.  As I drove the route, all I could think of was that this winding road was one the US Highway, and that it continued on across the dam, and that that was the route that people used to have to take to get through the area.  The traffic jams must have been constant!

We finally arrived at the visitors center and booked our tour down into the power plants and tunnels.  The elevator ride itself is a minute long, with stops carefully choreographed to manage all the tourists making their way through the facilities. It was all a comedy act from there as our chaperon introduced himself as our dam guide and told us he would answer all of our dam questions.

Eventually, when we reached the lowest elevator station, we were told that the tunnels that we were walking in were part of the channel infrastructure that had to be built to reroute the river before the dam could start - these tunnels themselves took two years to build, the same amount of time the dam took!

A scale model illustrating the construction process.

We also had a look at the turbines in their cavernous room - it is hard to believe that the base of the dam is 600 feet wide, and it surrounds this area on both sides.

Some other interesting facts about the dam, which was built during the Depression but had been planned over the 20 or so years before:

• The dam cost less than $50 million to build in the 1930's
• It was estimated that residual heat from curing the concrete would remain for more than 100 years
• The water in Lake Mead serves seven states - and provides a national recreation area as well

One of the inlet towers, showing the receding water level.

The calculus of population growth and rainfall and snowfall has meant receding water levels in Lake Mead.  In the photo of the inlet tower, the bleached out walls of the canyon above the water level are a testament to this problem - the water level has been in a constant state of retreat since the dam was first built.

We spent a couple of hours enjoying the tour and checking out the exhibits on the construction of the dam.  Then it was on to Flagstaff, which would be the base for our day trip up to the Grand Canyon.

The New Bridge at Hoover Dam

The O'Callaghan-Tillman Bridge, the new Hoover Dam bypass.

After my business was done in Las Vegas, Mary and I had planned a short vacation visit to the Grand Canyon, with a stay in Flagstaff, AZ.  On our way there, I'd planned a stop at the Hoover Dam so that we could take the tour - I'll post about that tomorrow, and so that we could check out the O'Callaghan-Tillman Bridge on US 93, which was opened in 2010 to replace the old route over the dam.

A view of the bridge from the pedestrian approach -
showing the handrail and the walkway.

The first photo of the bridge was taken from on top of the dam - where the old route went.  Here you can see that the bridge is only 1,500 feet downstream from the dam, and crosses the Colorado gorge at a height of 800+ feet. One of the attractions here - something I didn't know if I could handle - is that there is a walkway on the side of the highway that runs the length of the bridge.  The second photo below shows that feature - Mary and I walked out about halfway.

My final picture with this post is the incredible view of the dam you can see from the walkway.  They have included a lot of interpretive information along the walk up to the crossing - construction and engineering project data, including schedules, amounts of material used, and the firms involved.  Working for a couple of large engineering firms in the past, I enjoyed that part almost as much as they walk across the bridge itself.

The view of Hoover Dam from the new bridge.

We also took in the tour of the dam - that will be my next post.  In the meantime, if you want to know more about the bridge, here's the Wikipedia entry:

http://en.wikipedia.org/wiki/Mike_O'Callaghan%E2%80%93Pat_Tillman_Memorial_Bridge