Kubricky Construction New bridge emulates concrete spandrel arches of the historic crossing it replaces.

Kubricky Construction Corp., Glens Falls, N.Y., used a 300-ton crane to lift into place two sections of arched formwork for a 122-ft-long center span. Crews opened the new bridge to traffic last fall, avoiding a potential $3,200-per-day fine. They are now building a parking lot and scenic outlook area, with total completion set for August, says John Walsh, Kubricky project manager.

The Vermont Agency of Transportation determined that retrofitting the original nearly century-old historic bridge, with a concrete open spandrel arch, would cost at least $1.5 million. The agency rejected a downstream site with endangered trees, an active railroad and fractured rock issues, says Sherard G. Farnsworth, VTrans project manager.

Kubricky Construction Arches were rotated into place adjacent to active rail.

But building alongside the bridge was no easy task, either. It required navigating adjacent abandoned quarries, the railroad and the old bridge, just 5 ft away. A college borders the site. “The permitting challenges and physical challenges were tremendous,” says Chris Baker, national director of structural engineering for designer Vanasse Hangen Brustlin Inc., Watertown, Mass.

A stroke of luck came in 2000, when Farnsworth got a call from an owner looking to dispose of 400,000 cu yd of fill from a nearby hospital project. VTrans acquired the fill and placed it in the quarry at about $3 per cu yd under a $1.4-million contract to dewater both quarries, plug the tunnel and fill the east 2 acre quarry of the 2 open quarry pits on either side of the Colchester approach to the bridge. “We eliminated two retaining walls totaling 700-ft-long and saved $1.5 million,” says Farnsworth. “If we had not filled in the east quarry, we would have had to close down the road for 18 months.”

Fli-Rite Aviation Rail, old bridge, quarries and other obstacles bordered the Vermont river-gorge site.

State preservationists wanted a modern version of the historic bridge’s spandrel arch. “The columns of the piers are cast in place, and prestressed concrete spans make up the top part of the arch spans,” says Baker. Good rock conditions eliminated profile-altering abutments for the arches.

Kubricky blasted some 300 cu yd of the rocky slopes for rock-bolted foundations. Two sets of self-supporting formwork were built on their sides, then lifted and spun right side up in the air for placement and pour, says Walsh. “The arch from base to top is 35 feet,” he notes. “To erect that standing up, we’d need that much room. We didn’t have the room alongside the railroad to do that.”

The arches are each 4 ft wide and  4 ft thick, spaced 20 ft apart. They comprise a 122-ft-long center span as part of the approximately 285-long crossing, says Walsh. The old bridge was demolished in January. The new bridge is prepared to carry 7,000 daily motorists.