How do we make tunnels through mountains?

The Science of Zion National Park

Zion National Park — E. Winick

As an engineering student, relocation every 8 months has been part of the college experience. As a result of my internships being all over the country, I had to complete my 3rd cross United States drive this month and this time I wanted to make it a little more fun by visiting 8 national parks and diving into the science and engineering behind them. Now back home, I want to share that science with you all!

Zion-Mt. Carmel Tunnel — E.Winick

For my cross country drive, the second national park I hit was Zion National Park in Utah. Now, I loved the park and it was absolutely gorgeous, but as an engineering student the thing that truly struck me was a tunnel. Yes, a tunnel.

Driving out of the park I took the Zion-Mt.Carmel Highway. About 6 miles from the visitor center, I hit one of the coolest tunnels I’ve ever been through, Zion-Mt. Carmel Tunnel. This is a 1.1 mile tunnel that was completed in 1930 by the Nevada Construction Co. which at the time it was constructed, it was the longest tunnel of its type in the United States.

So how did they engineer and make this long of a tunnel through a mountain in the 1920s and 1930s? Well, it started with the windows.

The only light throughout the drive through the tunnel is provided by cutouts or windows in the side of the tunnel. These windows had other purposes than just lighting for cars and the workers making the tunnel. They were used for both ventilation and the dumping of rocks during construction. Rocks were dumped through the openings in the wall into the canyon below to create the tunnel. These windows provided the crews with a source to reach the inside of the cliff and bore their way through the rock. Slowly the builders created a small initial hole that went through to opposite ends of the cliff. After this small hole was created, drilling and blasting were used to widen the tunnel until it was wide enough to be passable by cars. During this process some collapses did occur resulting in additional concrete structural supports being put into the tunnel.

The impact of this tunnel in Zion made the trip between the national parks in the area much quicker, giving a faster route between Bryce Canyon National Park and Grand Canyon National Park. The trip to visit all these parks is referred to as the Grand Circle Tour.

Historic Landmark Sign — E. Winick

As a result of the design and engineering of this tunnel, in May 2012, Zion-Mt. Carmel Tunnel and the high way connected to it were designated as a Historic Civil Engineering Landmark by the American Society of Civil Engineers (ASCE). So if anyone wants to plan an even more nerdy road trip, try out a tour of all the Historic Civil Engineering Landmarks around the country. See the list of all of the here on the ASCE website.

Want to learn more about the science of the national parks and dive into the creative side of science? Follow Erin on Twitter to get the latest blog post updates?

Other national park blogs in the series:

Death Valley: Why is Death Valley so Hot?