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Thursday, July 14, 2016

Road Trip: The I-15 Virgin River Corridor is a hidden engineering marvel

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By Tom Herrmann and Gant Wegner / ADOT Communications

When Arizona’s portion of Interstate 15 through the Virgin River Gorge was opened to traffic in December 1973, following nine years of construction, it was the most expensive rural interstate construction project to date.

Here’s why: Picture a 15-mile-long river gorge so rugged that travel through it by horse or on foot is nearly impossible. Now imagine a busy four-lane interstate freeway, following a route set by federal officials, running through the same gorge. It’s like a mini Grand Canyon … except you can’t drive through the Grand Canyon unless you have a raft.

Don’t feel bad if you have never heard of I-15. The 1,400-mile freeway traveling between Southern California and Alberta, Canada, clips just 29 miles of the far northwest corner of Arizona on its way between Las Vegas and Salt Lake City. The only place you may conveniently access I-15 in Arizona is via Mohave County Highway 91 in the town of Littlefield.

Let’s buckle up and take a road trip on I-15, where we’ll marvel at the human ingenuity of modern roadway engineering and admire Mother Nature’s handiwork in an ancient 500-million-year-old sandstone gorge:

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Entering the gorge from the south, we pass through “The Narrows” and see the rock faces that tower above us. Imagine the rock blasting that was involved to cut a path for the freeway. The original road builders were certainly courageous: Engineers rappelled down the 400-foot rock faces to set the explosive charges.

2016-0703 I-15 North Entrance ADOT Photo

Driving in from the north, our view is even more spectacular.

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The freeway skirts the Virgin River. The original road builders rerouted the river channel in 12 places to fit the freeway design and even imported a “swamp buggy” from Texas to navigate the waterway. Times have certainly changed. Today, the sensitive environmental rules restrict touching the river. Rock blasting in the gorge is prohibited. Recent repair work on bridges by the Arizona Department of Transportation required protective shielding to catch falling debris.

2016-0703 - I-15 Bridge No. 6

There are seven I-15 bridges through the gorge. After more than 40 years of use, the structures now require a little TLC through ADOT’s ongoing rehabilitation projects. Pictured here is Bridge No. 6, which received a comprehensive, $27 million upgrade – completed early this month – that widened the roadway and replaced the bridge’s girders, decks and railings. Three other bridges were repaired and improved since 2014.

The ride is smooth since the entire 29-mile length of I-15 in Arizona has been repaved.

Yet with all there is to admire along I-15, we should reflect on the amazing accomplishments by transportation workers, both yesterday and today, to make this road trip possible.

In the early 1960s, Max Blazzard, the Arizona Highway Department chief project supervisor, wrote at the beginning of the original construction project, “It’s hard to visualize a divided highway in this area. The canyon is so narrow and deep the sun never hits in some sections during the winter months.” Yet he led a daring team that engineered an untamed river gorge into a modern transportation thoroughfare.

More than 50 years later, Adam David Carreon, the ADOT resident engineer who managed the Bridge No. 6 improvement project, thinks today’s reconstruction work could be as challenging as the original project. His team worked within a limited equipment staging area, on a bridge 100 feet above a river they couldn’t disturb, to complete a major project simultaneously with 24,000 vehicles per day traveling through the work zone – all with a dedication to the safety of both motorists and workers.

To learn more about ADOT’s efforts to improve and maintain I-15, check out a time-lapse video of the most recent rehabilitation work on Bridge No. 6, along with a series of project updates and a bunch of photo albums.



We take for granted the ability to travel around Arizona on a network of highways and interstate freeways. The Road Trip series of blog posts takes a closer look at those roadways – their history and unique characteristics, and ADOT’s efforts to ensure your next journey is safe and efficient.
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