To the Editor:
The proposal to pave Sherman’s Bridge seems a bit over the top, unnecessary, and not in keeping with the historic nature of the bridge. Instead, I suggest installing a wearing surface, running parallel to the direction of traffic.
According to the U.S. Forest Service manual, “Timber Bridges: Design, Construction, Inspection, and Maintenance,” a wearing surface is a layer placed on the bridge deck to form the roadway surface. It is the only portion of the bridge in direct contact with vehicle traffic. On timber bridges, a wearing surface is one of the most important components of the superstructure and serves two primary purposes. First, it provides a safe, smooth surface for vehicle traffic and improves the poor skid resistance of treated timber decks. Second, the wearing surface protects the deck from the abrasion and physical action of vehicle traffic. Without this protection, timber decks can wear rapidly, resulting in accelerated deterioration and reduced structural capacity.
When worn, the wearing plates are replaced without having to repair the bridge deck. But note that the roads leading up to the bridge need to be co-planar with the surface of the wearing plates in order to ensure a smooth transition from road to bridge and back to road again.
The use of at least partial wearing plates is common practice on wooden bridges in Vermont, regardless of whether the bridge is covered or uncovered, public or private, for cars or for snowmobiles. Implementation of this approach on Sherman Bridge would reduce wear and tear on the vehicles, extend the life of the bridge, reduce noise for the surrounding neighborhoods, and save money.
Cindy Berman
Campbell Road
