COLCHESTER -Drivers and bikers traversing the old Lime Kiln Bridge that links Colchester to South Burlington probably had no inkling of its architectural significance. Below a narrow, crumbling deck, the 93-year-old bridge was constructed of a series of heroic arches suspended high above the Winooski River Gorge.
On the Vermont Agency of Transportation website, archaeologist Chris Slesar writes of this marvel of early-20th-century engineering: "Rarely does the built environment meet the natural environment with such grace."
Travelers crossing the bridge that will take the place of the original might like to know that the new structure is being honored as the second-most-impressive bridge built in North America this year.
"Only the most challenging jobs are going to get on our top-10 list," says Bill Wilson, editorial director of Roads and Bridges magazine. "And the Lime Kiln Bridge project is chock-full of challenges."
Wilson points to the success of Vermont Agency of Transportation engineers and consultants in completing a project that exhibits elegant form as well as ingenious solutions to site-specific problems. On schedule.
The $9 million bridge mimics the historic design of its predecessor but has been executed with modern materials. Instead of the cast-in-place concrete used in 1913, the 21st-century builders relied on pre-stressed concrete slabs fabricated at the Cararra works in Middlebury. Wilson further notes that the bridge surface has been outfitted with de-icing membranes representative of the "pro-active approach" taken by the state agency, known as VTrans.
The Lime Kiln Bridge beat out about 40 nominated projects for the number-two spot on the Illinois-based magazine's annual top-10 list, which will be published in its November issue. "This was probably the most competitive Top 10 there's been since I created the list six years ago," Wilson says.
The Benicia-Martinez Bridge in the San Francisco Bay area is being honored as the best bridge completed or under construction in 2006. This $800 million, 8790-foot-long span has been designed to withstand seismic shocks of an intensity that occurs about once a century, Wilson notes.
In overcoming "geo-technical issues of great intricacy," the Lime Kiln's engineers filled in a long-abandoned quarry that allowed the new bridge to be constructed alongside the original, says Colchester public works director Bryan Osborne. The bridge opened to traffic a month ago and will be officially inaugurated next August, when it is expected to be fully operational.
If the quarry and a connecting tunnel had not been filled, Lime Kiln Road would have had to remain closed for up to 18 months rather than just three weeks, notes Sherward Farnsworth, project director for VTrans. The 360,000 cubic yards of fill came from Fletcher Allen's scandal-plagued and budget-busting "Renaissance Project."
St. Michael's College donated the land for the new bridge. In return, the school paid nothing for the filling of the remainder of the quarry, which it also owns. St. Mike's will now be able to use the land as athletic fields or for construction of a hockey rink, Farnsworth says.
The project moved smoothly once it got going, but preparatory work and permit permutations consumed almost 15 years, Osborne points out. He says a full year was spent negotiating with the state's Department of Historic Preservation, which had wanted Colchester and South Burlington to preserve the old bridge as a pedestrian span. But the additional cost of rehabbing that structure would have placed the entire project beyond the two towns' financial means, Osborne says. And the old bridge had already been renovated twice - in 1940 and in 1991.
The replacement structure is the product of an agreement to tear down the original after architectural historians have had a chance to document it. There's still time to say good-bye to your great-grandparents' bridge. It won't be entirely demolished till December.