Boulder City in Clark County, Nevada — The American Mountains (Southwest)
Span The Gap with Cables 7 Arch
Journeys & Heros
Photographed by Sandra Hughes Tidwell, September 9, 2025
1. Span The Gap with Cables 7 Arch Marker
Innovative Design for the Deck Arch Bridge
The Design Team worked through six deck arch options to find one for the best form and function, a unique hybrid structure with a concrete arch coupled with a composite steel superstructure.
Engineer needed to find a bridge system that would perform well during high winds or a possible earthquake. The Design Team chose to use a pair of ribs for the arch instead of a single wide arch. Steel struts that flex in an earthquake or under high winds connect the twin ribs to protect the whole arch from damage. The arches transfer the forces to the canyon walls.
The twin arch ribs support concrete columns, which in turn support the bridge deck system. The bridge engineers used high-strength concrete where compression forces controlled the design in the arches and columns. Where flexing forces drove the design, they used steel for the sturts and deck girders.
How to build an arch bridge across a wide canyon 1. Set up towers, cables, winches, and staging areas.
2. Stabilize the cliff and set arch foundations.
3. Place concrete foundations for columns.
4. Build precast concrete columns on foundations.
5. Install beams and road decks of bridge approach.
6. Erect temporary towers and cable stay anchors.
7. Install arch rebar and cast concrete segments.
8. Install temporary stay cables on arch segments.
9. Install steel struts between twin arch ribs at columns.
10. Place concrete for final closure of arch.
11. Remove towers and cable stays from arch.
12. Build precast concrete spandrel columns and cap beams.
13. Install steel box girders of main bridge span.
14. Build road deck of main bridge span.
15. Remove towers, cables, and staging areas.
16. Build barriers and railing on visitor walkway and deck.
[Caption:]
Arch Construction Method
The bridge
this page online
The opposite halves of the twin-rib arch were made of 26 segments that hung in mid-air from cables until the builders placed the concrete of the final, narrow closure.
The cableway system lowered pre-made cages of steel reinforcing bars into place for each cast-in -place concrete segment. Fearless workers toiled 800 feet above the river connected the steel cages by hand. They set the forms, placed the concrete, and moved up for the next segment. High performance concrete with a compressive strengthn of 10,000 psi was needed to handle the massive loads.
Mike O'Callaghan - Pat Tillman Memorial Bridge
Topics. This historical marker is listed in this topic list: Bridges & Viaducts.
Location. 36° 0.883′ N, 114° 44.674′ W. Marker is in Boulder City, Nevada, in Clark County. It can be reached from Hoover Dam Access Road east of Boulder City Bypass / Purple Heart Highway (Interstate 11), on the right when traveling east. Touch for map. Marker is at or near this postal address: 81 Hoover Dam Access Rd, Boulder City NV 89005, United States of America. Touch for directions.
Regionally, this marker is in Nevada’s Colorado River Valley, in the Mojave Desert, and in Greater Las Vegas. It is also in the American Southwest and in the Mountain West. Globally, it is in North America, the Western Hemisphere, the Western World, and the Anglosphere. Historically, it finds itself in what was once New Spain and also Mexicos Alta California.
Other nearby markers. At least 8 other markers are within walking distance of this marker: Protecting the Place of Nature & History (here, next to this marker); Choose the Site for Crossing & Bridge (here, next to this marker); Clear the Way of Switchyard & Towers (here, next to this marker); Lay the Path with Cut & Fill (here, next to this marker); Design the Dream with Science & Art (here, next to this marker); Enjoying the Ride with Celebration & Pride (here, next to this marker); Raise the Road on Columns & Deck (here, next to this marker); America's Finest (within shouting distance of this marker). Touch for a list and map of all markers in Boulder City.
Credits. This page was last revised on December 26, 2025. It was originally submitted on October 2, 2025, by Sandra Hughes Tidwell of Killen, Alabama, USA. This page has been viewed 63 times since then and 26 times this year. Photo 1. submitted on October 2, 2025, by Sandra Hughes Tidwell of Killen, Alabama, USA. • Devry Becker Jones was the editor who published this page.
