Committee members in attendance: J. B. McCarthy, David Hoyne, Warren Tripp, Eric Gilbertson, Nancy Boone, Scott Newman and Sue Scribner. Project engineers Mike Fowler, Mladen Gagulic and Rebecca Pellett from Bridge Management, Joe Nelson representing the Vermont Covered Bridge Society and Michael Canavan from the Federal Highway Administration were also in attendance.
The purpose of this meeting was to discuss the final plans development prepared by the Bridge Management Section.
Bridge Management provided a PowerPoint presentation showing historic photos of the structure as well as more recent ones. Details of recent repairs and Phase I work were highlighted as well. The following was discussed:
The final decision for the use of the bridge as decided by the Town of Cambridge is to allow vehicular traffic once again on the structure, one direction at a time.
The grade of the bridge was raised by approximately 3 feet during the Phase I work. This has affected the approaches as well as the abutments and the wingwalls, particularly the southwest one. The plans depict removing the existing concrete pad on top of the laid-up stone abutments, repairing the laid-up stone abutments, pouring a new pad and then laying-up more stone on top of that until the appropriate grade is reached. The approaches have been redesigned to meet the new grade requirement. A retaining wall will be needed.
It appears that the floor-beams were "doubled up" during some rehabilitation effort. The supplemental or added floor-beams will be removed except for the end one on each side of the bridge. These will be re-used as possible if any of the original floor-beams need replacing.
The new deck will be 3 "glu-lam with 2" oak runner planks. Should a curb be provided? It was suggested that smaller size curbing be used, perhaps 4" x 10". This would leave approximately 2 feet from the trusses to the inside of the curbing for pedestrian. Bridge Management will analyze this as dead load is a concern.
Distribution beams are to be removed. New lateral bracing will be added underneath.
There is quite a bit of elongation at the scarf joints. The shear keys and hardware will be replaced at the scarf joints. Many of the bottoms of the king posts where they meet the bottom chord were previously cut off with the remainder having been destroyed by ice.
There will be a member replacement table. Any changes or variations to this proposed by the Contractor will need approval from the Structures Section.
A "builders plaque" will be added to the portal over the height restriction sign. It is also proposed that a new sign be added with language to the effect that the bridge is listed on the National Register of Historic Places and great care should be take to preserve the bridge. Scott Newman has stated that he would like to provide input on the final language. It was discussed if the sign should be on the approach or a special plaque off to the side of the bridge. Mike Canavan reminded everyone that if it were to be on the roadway approach, it would need to meet the MUTCD. Joe Nelson suggested that the Cambridge Historical Society be contacted to confirm the official name of the bridge as it is oftentimes referred to as either the Poland Bridge or the Junction Bridge.
The plans provide for 12" of residual camber. As there is currently a sag of approximately 18", the overall change to the camber will be approximately 30"
Mike Fowler has designed a special asphalt plug joint to hopefully ensure that there will be a smooth transition from the pavement to the bridge deck.
It was proposed that any existing holes or open joints be soaked with an anti-fumigant prior to repairs.
A new standing seam metal roof will be installed as will new siding. Although it appears sound, it was proposed that some of the roof sheathing be replaced to ensure a good solid connection for the new roof as some has been damaged elsewhere by wind. Steel-backed timber guardrail will be used on the approaches. Both a fungicide and some sort of fire retardant will be applied to the bridge.
A pre-bid conference will be held and will be mandatory for perspective bidders. It will be emphasized that this is to be a rehabilitation project and the contractors should expect extra time for any proposed changes to the plans. Eric Gilbertson, representing the Division for Historic Preservation, would like to attend the pre-bid conference. Two construction seasons are to be expected so that there is no rushing to complete the project. There was some discussion as to a special pre-qualification process to ensure only experienced timber-bridge contractors bid on the project. Bridge Management will explore this further. The chosen contractor will need to submit their intended approach for the work for approval prior to starting.
Contract plans are to be submitted in the next few weeks for bidding later this spring or early summer.
[This article was originally posted April 3, 2002]