Niagara Gorge Access Project

Talk about working conditions.

It's the dead of winter in upstate New York and 85-mile-an-hour winds and an icy mist are blowing off the thundering waters of Niagara Falls.

And you're on top of a 20-story-high structure, attaching 18- by 6-ft. mirrored glass wall sections onto a new 260-ton galvanized steel frame. And, there are more than 750,000 gallons of water falling each second only 100 ft. away.

"Wow!" one jury member said about the project team responsible for building a new 200-ft.-tall observation tower beside the sheer Niagara Gorge of the falls. "I was impressed by the working conditions, the site logistics, the tough location, the fact that it was done in the winter and rebuilt from the top down."

The new observation tower provides access for millions of people each year to view the falls, to travel down into the gorge and to ride on the Maid of the Mist boat into the waterfall. New high-speed elevators were installed to service nearly 700,000 visitors each summer. The project cost $20 million.

To minimize interruptions in the operations of the New York State Parks and the Maid of the Mist tours, the construction schedule was restricted to the eight off-season months from October to May. Much of the work progressed seven days a week, 24 hours a day.

With the project site in the Niagara Gorge and adjacent to the Niagara River, the area was impacted by a "microclimate" that could change in a moment. During the cold winter months, the wind would carry the mist created by the falls across the project site and leave behind a treacherous coating of ice.

To handle the problem, the project team provided a 200-ft.-tall, freestanding, shrink-wrapped scaffold enclosure surrounding the existing tower.

The enclosure was anchored by 24 rock anchors, embedded 35 ft. into the bedrock of the lower Niagara Gorge. It provided a safe haven for work on the towers throughout the winter months and also provided a pair of scaffold stairs for personnel access to and from the lower gorge.

The scaffold enclosure - which was only designed to withstand 65-mph winds - worked effectively except for two, one-week periods when winds were clocked in excess of 85 mph.

A temporary metal deck platform system was suspended below the existing bridge trusses. This system acted as a debris catch, a working platform, containment for the lead-based paint removal and recoating operations, and access from the upper gorge to the scaffold.

To meet the schedule and quality control requirements of the project, the project team required that the new structural steel for the tower be prefinished. That raised two concerns: The risks associated with erecting prefinished steel exposed to the misting from the falls and cost and quality assurance issues pertaining to touch-up requirements after erection.

In response to these concerns, the project team proposed an alternate finish, hot dipped galvanizing. The result was savings of $107,000, a slip-resistant finish that allowed erection in even wet conditions and the virtual elimination of any field touch-ups.

While the scaffold enclosure provided protection from the wind, it was required to remain open at the top to hoist materials in and out of the tower. It was, therefore, not heated.

Due to the conditions and the demand of the schedule, the project team requested that the structural engineer design the new structure with all bolted connections. The project team worked closely with the steel erector to identify large bents of structural steel that could be preassembled in the upper gorge and lowered into place with the project crane.

These massive sections of steel were lowered through the existing bridge trusses and then down into the scaffold enclosure, using a crane stationed 230 ft. away. The countless hours spent determining permissible bent sizes were regained many times over when 259 tons of structural steel, all levels of grating and the center stair tower were erected in 24 days in the dead of winter.