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12.02.2009
Bridge Nixed
DOT shuts down vulnerable Champlain crossing
The Champlain Bridge on the border of New York and Vermont was permantly closed in October amid concerns about its possible collapse.
Ed Barna

Every five years, the 80-year-old Champlain Bridge, used by more than 3,500 cars daily to cross over Lake Champlain between New York and Vermont, undergoes an underwater safety inspection. But this October, concerns about the bridge’s stability led the New York State Department of Transportation (DOT) to call for an inspection one year early.

Officials were shocked at what they found: Cracks in concrete piers that concerned inspectors during the previous visit in 2005 had more than tripled in size, from five to 18 inches deep. “You should not see anywhere close to that deterioration in that short a time,” said John Zicconi, director of planning, outreach, and community affairs for the Vermont Agency of Transportation. The department immediately closed the bridge for good on October 16.

The closed bridge, seen from New York.
mmr Dad/Flickr

Designed by engineering firm Fay, Spofford & Thorndike in 1929, the Champlain Bridge is a notable example of a continuous truss design, in which each span is interconnected to the others, allowing for less material and a lighter, more elegant aesthetic. The design is the same as that of the Minneapolis bridge that collapsed in 2007, killing 13 people. And it shares that bridge’s vulnerabilities. “Like the Minnesota bridge, when you lose one pier or support or section, it drags the others down with it,” said Robert Dennison, chief engineer for the DOT, which operates the bridge jointly with Vermont.

Another vulnerability is the unreinforced concrete that was used to build the nine piers on which the bridge rests. As the lake ices over, thaws, and re-ices every winter, water seeps into the concrete’s pores and expands as it freezes, widening existing cracks. Compounding the problem are the bearings atop the piers on which the bridge rests. Made of both steel and polymer composites, they have become rigid over the years. That means that when the bridge is buffeted laterally by wind or expanding ice, those forces get transferred directly to the already-weakened piers.

The bridge's roadway exhibits many cracks, though it is the ones in its piers that have caused the greatest concern.
Ed Barna

Transportation agencies have ruled out any possibility of repair, given the bridge’s fragile state. “To even attempt to repair it would put workers at risk,” Zicconi said. The departments are rushing to complete the permits and engineering plans needed for a controlled demolition as soon as possible, for fear that the coming winter’s wind, temperatures, and snow loads might collapse the bridge precipitously. After the demolition, a new bridge will be constructed as close as possible to the location of the current one; the details of its design are still uncertain.

Until that time, two state-subsidized ferries will be transporting drivers across the lake. Land detours are much more circuitous, taking people about 100 miles out of their way to the south, and even farther on the detour to the north. The total cost of subsidizing alternate transportation, demolishing the bridge, and building a new one will amount to at least $80 million, Zicconi estimated, to be shouldered equally by Vermont and New York.

Drivers must now take a ferry to cross the lake or a 100-mile detour.
route17fan/flickr

Despite the suddenness of the bridge’s demise, it should not come as a surprise. The Champlain Bridge has already outlived its life expectancy of 70 to 75 years. “I think we’ve become used to the concept that bridges have an infinite life,” said Dennison. “They don’t.”

Julia Galef