Vermont’s first segmental concrete bridge, a 1,036-ft-long span, carries Interstate 91 and stretches over Vermont Route 30 and the West River. Standing 100 ft above the river valley, the 515-ft main span forms an open gateway anchored by curving cathedral piers.

The project swapped two deteriorated steel bridges with a single, 104.8-in.-wide concrete bridge. The span comprises concrete trapezoidal sections placed by a cantilever construction system. Gov. Phil Scott (R) labeled it “the largest construction project since the interstate system was first built” in Vermont.

In what Linn describes as the Vermont Agency of Transportation’s “positive approach to sensitive challenges,” VTrans and PCL held extended negotiations regarding the schedule change and reached a settlement that reduced the project’s contract value by nearly $1.38 million and protected the state from further delay-related costs.

VTrans’ initial segmental-concrete bridge concept, deemed “ugly” by some community members, led to an aesthetics committee, comprising local stakeholders, to help develop a more pleasing design. “Figg worked closely with the community and VTrans on the aesthetic and functional design centered around a theme of ‘Vermont: A Bridge to Nature,’ incorporating features such as concrete forms that look like stone,” says Garrett Hoffman, Northeast director at Figg.

Linda Figg, president and chief executive officer of the Figg Bridge Group, the bridge’s designer, says the dramatic cathedral-like piers, with nature-observation platforms on each side of the river, were inspired by the state seal. “The platform space is formed from the top of each footing with a stone texture and a pattern that represents a white pine with 14 branches,” she says. “From the top of the platform rise, the curving quad- wall pier columns directly support the concrete-box girder superstructure.”

The dome-shaped underside of the superstructure that runs the length of the bridge is sky-blue, evoking the feeling of being in an outdoor cathedral, Figg adds.

With cantilevers all on a curve, the design created significant challenges associated with geometry, particularly with the upper portions of the columns that had to tie into the pier table, Linn says.

“The size of each pier table resulted in very large loads imposed on falsework,” he says. “To achieve the desired as-built dimensions, each lift required an analysis to determine the theoretical deflections of falsework and formwork.”

One of the biggest challenges occurred during a stretch of unusually mild weather in early 2014, following freezing temperatures. The warmer temperatures broke up ice upstream, causing an ice jam near the bridge, which became a “choke point” for water coming down river, Linn recalls. While crews were working on the foundation, the water rose several feet within minutes, flooding equipment. That night, the temperatures dropped into the single digits, freezing all the equipment.

“We had to wait until the river drained into the Connecticut before bringing excavation onto the causeway to scrape off the ice,” Linn recalls. “We got lucky—the highest water level was within three inches of the computer equipment.”