By Mel Huff | Contributor
Historic bridges require maintenance, and the Seguin Bridge—the “upper” covered bridge on Roscoe Road in Charlotte—is no exception. The most recent work on the bridge was in 2014 after a VTrans assessment found extensive insect damage along the entire length of the top chord of the downstream truss. The town authorized treating it for carpenter ants and powder post beetles. Although this helped contain the damage to the exemplary kingpost Burr Arch bridge, larger structural issues were yet to be addressed.
This week, Blow & Cote, Inc. of Morrisville, which won the bid, plans to begin repairs that will close the bridge and part of Roscoe Road until mid-October or November 2016. The reconstruction will cost $431,048, but the town’s share, according to Selectman Fritz Tegatz, will be only about $2,000. That’s because the bridge is enrolled in the Vermont Historic Bridge Program, a partnership for preserving and maintaining the invaluable structures.
But what’s the problem with it? It looks fine.
Joseph C. Nelson, president of the Vermont Covered Bridge Society and author of Spanning Time: Vermont’s Covered Bridges, noted “recent damage” to the bridge in 2011. “At least three knee braces were broken out, and all of the rest had damage of some sort, ranging from cracks to paint transfer from an apparently over-height vehicle,” he wrote in a Wikipedia entry.
In addition to the extensive insect damage documented in 2013, VTrans also reported a fracture in the bottom chord of the downstream truss and said the floor beams, flooring and siding appeared worn. The repair plan VTrans developed will be implemented over the next six months.
Seguin or Sequin?
Agreement about the Seguin Bridge, which was built around 1850, is hard to come by, starting with its name. It’s “Seguin,” for the Seguins who owned land in the area. The “Sequin” spelling first appeared in 1974, when the bridge was entered in the National Register of Historic Places. Since then others have copied the misspelling.
What’s not in dispute is that the kingpost Burr Arch bridge is a masterpiece.
Gilbert Newbury, a structural engineer and timber bridge expert, has noted that intricate “keys,” especially visible in the Seguin Bridge, are used in the tension connections in the bottom chords, and that “the elaborate roof framing systems include ‘birds-mouth’ notches in the rafters and beams. Nelson also writes, citing Newbury, “the top lateral braces are set in an elliptical shape, very difficult to do, and not copied elsewhere.”
Within VTrans, a Historic Bridge Preservation Committee evaluates restoration plans according to a Historic Covered Bridge Preservation Plan. The plan’s priorities are, first, “to maintain the historic use of these bridges as part of Vermont’s network of roads. The second is a desire to preserve the structural integrity of historic members of these bridges to the maximum extent possible” (historicbridges.vermont.gov/covered-bridge).
As Robert McCullough, a faculty member in the University of Vermont’s historic preservation program—and formerly the VTrans Historic Preservation Coordinator—says, “That’s the objective, to try to keep the bridge as original as you possibly can.”
The current restoration plan, designed by John Weaver, calls for replacing both top chords with new ones an inch wider, and replacing and strengthening the floor. The plan also includes repairing the south abutment, replacing the siding and applying fire retardant and a wood preservative to the untreated lumber and timber. The plan was approved by the Historic Bridge Preservation Committee.
As it was in the past, the bridge is again a locus of disagreement.
Jan Lewandoski is a highly regarded Vermont timber framer who in 1994 did what Nelson calls “authentic” repairs to the Seguin Bridge and in 2009 served as a consultant on the restoration of the Thorpe barn.
For Lewandoski, the repairs proposed by VTrans present the potential for damage to the unusual overhead bracing when the upper chords are replaced. Lewandoski expressed another concern: that raising the weight limit will increase “the danger from those who think the bridge can now take any size vehicle after its repairs.” Even more serious is the risk to the roof, itself. “If the entire top chord is being replaced, I expect the entire roof is coming off.” When anything so old is taken apart, Lewandoski says, there’s a risk of damage.
Marc Cote, Blow & Cote’s president, confirmed that the plan is to remove the roof and lay it on the ground. “All we can hope now,” Lewandoski said, “is that anything doesn’t get broken, or changed for no reason. What it all comes down to is I just hope they’re careful.”
You’ve got to carry that weight
Mark Sargent, the project manager, says VTrans increased the weight limit at the town’s request and notes that the change from 5 to 7 tons is not an “appreciable amount.” (For context, a Prius with no passengers or luggage weighs a little more than 1.5 tons. The lightest Type C school bus—the type CCS uses—weighs around 9.75 tons. The Quinlan Bridge is rated for 16 tons.)
The idea of increasing the weight limit emerged at a meeting of Sargent and the Selectboard at the bridge. Charles Russell remembers it took place late in his last term in office.
“There was the discussion of…what those repairs would mean for the rating,” he said, “and they said the way it is right now, we would have to rate this really low so that almost nothing could go through. They came up with a plan for how to get the rating higher.
“My impression was we weren’t shooting to make it hugely different,” Russell said, adding, “Mark Sargent was great—thinking outside the box!”
The Seguin Bridge restoration is a labor of love for Sargent, a seventh generation Vermonter who grew up on the Connecticut River in Fairlee. After doing a site visit to the bridge and seeing the carpenter ant damage, he contacted his federal counterparts, got money for the engineering and had the bridge designed by VTrans for about $23,000—work that would ordinarily cost 10 times as much. “If it weren’t for my efforts,” he said, “this covered bridge would have probably been closed by now, or within a couple of years. And it would be a lengthy time until it was rehabilitated.”
Sargent is confident there will be no damage to the bridge when the top is removed. He said, “John Weaver (the designer) and I are a pretty good team. We hold the contractors’ nose to the grindstone. We’re both passionate about covered bridges.”
But Lewandoski is less sanguine about the risk to the rare example of craftsmanship and early engineering imagination.
The Seguin Bridge “is one of the most intact and beautiful, oldest, well-built and sophisticated bridges in the state,” he declares. “I just fear what this upgrading will result in.”