Mines Magazine Turns 100 - the Timothy and Bernadette Marquez ...

By Larry BorowskyPhotography Courtesy of Hoover Dam Bypass Bridge ProjectIn five seasons as a middle linebacker for the Colorado School of Mines football team, DaveZanetell learned a lot about teamwork. That education turned out to be every bit as useful ashis Mines engineering degree—maybe even more so—when it came to building the Hoover DamBypass Bridge.Officially opened in October, it’s the longest concrete-arch bridge in North America. The towering300-foot precast/post-tensioned concrete columns supporting the roadway at either side of thearch are the tallest in the world, it’s the second-tallest bridge in North America and it’s one of themost technically challenging bridges ever constructed.The director of engineering for the Central Federal Lands Highway Division (a unit of the FederalHighway Administration that encompasses all but five states west of the Mississippi), Zanetellpersonally led the Bypass Bridge project management team since his appointment in 2001.Zanetell, photographedfrom Hoover Dam, with thebridge almost completed.Zanetell had no shortage of talented people and firms to pickfrom—the opportunity to build an iconic and technically challengingstructure in the shadow of one of history’s greatest engineeringachievements doesn’t come along very often. “It was one of the biggestjobs you can imagine; one that had the world’s attention. Thebest people in every discipline wanted to be involved, and given thejob we had before us, it was a good thing,” he says. But, he adds,great people come with strong opinions.Zanetell had to knit two state governments, four federal agencies,five general contractors, and dozens of consultants into aneffective unit. It might easily have devolved into a chaotic tangleof turf wars, conflicting agendas, and clashing egos, but pullingfrom his old football playbook, Zanetell united these disparate playersinto a formidable team. “It took work to mold all of that talentinto a cohesive group with a singular vision,” says Zanetell, whocelebrated the completion of the $240-million span, on budget, thisfall after almost six years of construction.Strung nearly 1,000 feet above the Colorado River, the 1,900-foot arch-bridge solves problems that stymied engineers for morethan three decades. Some of these were difficulties intrinsic to thephysical site—high winds, challenging terrain, steep walls, and thecanyon’s sheer depth and breadth—and some concerned the aesthetics.A steel-truss arch would have been the most straightforwardsolution, but for the structure to blend with the Hoover Dam, thenew bridge would also have to be concrete, and it was agreed thata sweeping arch would best complement the signature concave formof Hoover Dam.While none of the engineers questioned whether a concrete-archbridge would perform well once constructed, they all recognized thatit made a difficult job much harder. Concrete is heavier than steel,and its structural integrity can be compromised if allowed to set uptoo fast—a big concern in the hot, dry conditions of the Southwest.For these reasons, several previous plans to build a concrete bridgenext to the dam had died during evaluation; as recently as the earlynineties, a study declared a concrete bridge in this location to bemarginally viable, at best.Colorado School of Mines 23