One of Vermont’s oldest covered bridges is slated for an expensive restoration.
This piece first appeared in The Vermont Standard.
Final plans to rehabilitate the historic Taftsville Covered Bridge are almost complete. The Vermont Agency of Transportation (VTrans) and its design and construction management consultant, McFarland Johnson, are working on the last details and approvals needed to open the project for bids. But a program-cutting proposal by the Obama Administration could jeopardize the some of the funding for the nearly $3 million project.
The bridge, which spans the Ottauquechee River about two miles east of Woodstock Village, is one of the oldest covered bridges in the state. Businesses established by the Taft brothers in the late 18th century on opposite banks spawned the need for a bridge; the first three built near site of the existing span were washed out in floods. In 1836, Solomon Emmons III built the structure that has now survived for 175 years.
VTrans estimates that about 1,000 vehicles a day currently use the bridge to cross between Taftsville, along State Route 4 on one side, and River Road, with access to Woodstock and Quechee, on the other. The bridge is supported by vast mortar-less stone abutments on both banks of the river and a similarly constructed stone pier near the center of its 188 foot length. The “live” load from traffic is borne by systems of joined upright, lateral, and diagonal beams called trusses, and two pairs of laminated wooden arches, which were added sometime after the bridge’s original construction.
According to the National Park Service’s Historic American Engineering Record for the Taftsville Bridge, there is no documentation to explain Emmons’ design choices. He wasn’t known as a bridge builder, although he did work on one other Woodstock bridge, which is now gone. At Taftsville, he used a simple but relatively uncommon truss configuration known as a multiple kingpost. Many of its component timbers, with cross-sections of varying size, were hand-hewn from trees of near-by woods. And the truss’s lower joints are notable for their unusual, but functional, method of connection. The process to make them required fashioning large through holes in both connecting timbers, passing one through the other, then securing the intersection with a transverse piece slipped into the lower hole. The method was time consuming, but enabled Emmons to adjust the joints and square up the structure as he worked.
The Federal Highway Administration reports that although at least 10,000 timber covered bridges were built before 1900, there are fewer than 900 authentic covered bridges in the United States today, of any material or vintage. The bridge at Taftville, which is listed on the National Register of Historic Places, is one of the oldest remaining, and is a rare example of a hand crafted bridge; many subsequent structures used more systematic, even patented, truss designs.
Rehabilitating any historic bridge is complex, says McFarland Johnson consultant Ron Joy, who is working with VTrans to document specifications for, and manage, the project to recondition the bridge. “We’re designing this thing for modern snow loads and wind loads and traffic loads,” he says, “but we try to keep as much of the original bridge intact as we can.” The foundations and the superstructure will both be strengthened as part of the project.
There are some flaws and weaknesses in the existing, dry-laid stonewalls of the abutments and center pier, says Joy. “[The original builders] just got the best stones that they could, field stones or whatever,” he adds, “and tried to do the best they could to stack them up.” In the rehabilitation, the foundations will be treated with a proprietary mortar. The stones will then stick to each other and work together as a unit, but the adherent will also allow water to pass through, which is important to avoid the excess pressure created when water gets trapped behind the walls. Tension rods will also be drilled down into the central pier, to protect against pressure from water flow and ice, and the pier will get a new concrete cap to replace the current wooden crib that holds up the bridge above.
Up top, some elements of the truss system will be removed and replaced with new timbers, and strengthened with hidden tension-bearing metal tie rods. “We worked very closely with VTrans as well as the State’s Historic Preservation Officer,” says Joy, “we went through and did multiple inspections to minimize the number of existing truss members that we need to remove.” Some of the rafters supporting the roof will be changed out as well, and the arches will be fortified with additional wooden layers. The roof and red siding will be replaced, and metal braces that were installed inside in the 1950s to help keep the housing square will be eliminated in favor of something more historically appropriate. The structure’s undercarriage will be also be bolstered.
On the approaches to the bridge, there will be new signs and guardrails.
The project is on VTrans’ books at $2.989 million dollars, $350 thousand for preliminary engineering and the balance for construction. The Federal Government has been expected to foot eighty percent of the bill. According to Lenny LeBlanc, VTrans Director of Finance and Administration, $1.5 million was included as an earmark in the United States Legislature’s 2005 Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU). Another $1 million was granted to the project in 2009 through the National Historic Covered Bridge Preservation Program. Vermont is obligated to pay twenty percent of the project’s cost. Ordinarily, Woodstock would be on the hook for a tenth of the state’s share, but because the town signed an agreement to maintain the bridge, the state has waived that contribution.
Earlier this spring, however, President Barak Obama recommended elimination of the National Historic Covered Bridge Preservation Program. Depending on what Congress ultimately does, that could put a chunk of the funding at risk, but LeBlanc feels there is no real threat. “Even if that program is eliminated, it doesn’t necessarily mean that a prior year award would be eliminated,” he says. In the worst case, VTrans would have to replace lost monies with funds from another Federal program.
Nevertheless, VTrans Structures Project Manager Mark Sargent has accelerated preparations to get the Taftsville project out for bidding. The schedule had called for final specifications to go the Federal Highway Administration for approval and commitment of funds in Febraury; Sargent is now targeting to reach that milestone in July. “I’ll keep my head down and keep pushing,” he says.
Sargent and consultant Joy were in Woodstock for a hearing with the Selectboard on May 3; on May 17 the Board voted on a handful of details related to signage, lighting, detour route, metal brace replacement, and guardrail material. With their input in hand, Sargent and Joy will work up the final plans and specifications, and prepare paperwork for permission to use the proprietary mortar. They hope to submit the package to VTrans for its internal pre-contract review by the end of June. “We get comments back and then make a final submittal,” says Sargent; the funds become “obligated” during the subsequent final review process, which, barring any difficulties, can take about a month.
Once construction begins, the bridge will be closed for fifteen months or so. If all goes well, work could start as early as this winter.