Photo by Don Wilson; courtesy of POWER Engineers
Electrical union workers installed anchorages on both sides of the falls to stretch and secure a 2 in.-dia. wire cable.
Photo by Steve Behal, courtesy of POWER Engineers
High-wire stuntman Nik Wallenda successfully completed the 1,800-ft walk across Niagara Gorge on June 15.

Famed stuntman Nik Wallenda, who last month became the first person allowed to cross directly over Niagara Falls, did so on a 2-in.-dia. cable that was stretched 1,800 ft across the U.S.-Canada border waterfalls by a team of engineers, contractors and members of an electrical workers' union local in East Syracuse, N.Y.

For the June 15 event, the first sanctioned high-wire walk in the Niagara Gorge in 116 years, POWER Engineers, Hailey, Idaho, and O'Connell Electric, Rochester, N.Y., designed and managed the cable installation that included micropile anchors set into bedrock on both sides of the falls, using 170-ton cranes. The anchors held the seven-ton cable at a tension of 60,000 lb.

Because of the cable's over-water location, the firms used a series of stabilizing pendulums to eliminate cable twisting, which would make it unwalkable, says POWER.The firm adds that the cable was installed overnight in 14 hours and then removed in a seven-hour operation.

The team had to work mostly at night to avoid interrupting the movements of the Maid of the Mist tour boat operation.

Wallenda, a member of the famous family of acrobat-aerialists, crossed on the cable that sagged just 35 ft at its midpoint, which put it 200 ft above the river, says POWER.

The wire stretched from a U.S. anchorage that is higher in elevation than the one on the Canadian side.

"Technically, this was not nearly the largest or most complex cable installation that we have done," Peter Catchpole, the firm's senior project manager, told ENR. "But the key challenges were the timeline and knowledge of the cable itself. When we were first engaged in early March, the installation plan was for an event assumed for late August."  

Organizers accelerated that timeframe by two months. "This put the heat on equipment rental and permit issues," Catchpole says. "Most problematic was the fact that the cable was not pretensioned at the factory to remove its inherent looseness," he adds. 

He adds that in determining how the cable would stretch, the team had to "estimate on the side of 'perfect' that would allow better adjustments without moving the cable to a height that did not work" for Wallenda or TV cameras.

"If we had made a poor estimate that required making a change to the length of the cable, we would have triggered a day or two of hard work and caused considerable angst" to the event participants. "As it turned out, we did our educated guessing pretty well," he contends.

Catchpole also told ENR that another engineering challenge was "the quality of information we had of the crossing geometry and certain knowledge of the cable itself." He says it was "essential that we decide the length of the cable before pinning both ends because there was no mechanism provided to adjust it afterwards."

Catchpole says the team was also challenged by having three conflicting sets of information on the distance between the anchorages. "I hired a local surveyor [several days before the walk] and got a fourth number," he says. "We ran with his distance."

O'Connell Electric says the team successfully practiced the stunt with Wallenda, 33, by stringing a wire outside a Niagara Falls, N.Y., casino.

According to published reports, the stunt cost $1.3-million, which was offset by TV broadcast rights. The National Labor-Management Cooperation Committee, a venture of the National Electrical Contractors Association and the electrical workers' union, says it was a sponsor of the event.