The aging, severely deteriorated and historic Mitchell River wooden drawbridge was replaced with a safer, innovative and context sensitive bridge that combined the aesthetics of wood and granite with more durable and long-lasting concrete and steel components. Designed in compliance with multiple Federal and State regulations, design standards, historic requirements and local input, the essence of the old bridge was skillfully constructed in a new wooden drawbridge which maintains the signature look and characteristics that were important to the Town of Chatham while satisfying modern load rating requirements. The new bridge has been enthusiastically reveived by the community and has quickly become a local destination enjoyed by motorists, boaters, pedestrians, bicyclists and anglers alike.
This project replaces a deteriorating wooden drawbridge with a new structure that meets current loading requirements, yet is able to maintain the historic appearance of the bridge it replaced and will continue to provide the residents and tourists of Chatham, MA with a true destination structure. The existing 192′ long 12 span two lane wooden drawbridge, a popular destination in town, was difficult to operate and maintain and only had a small raised curb to separate pedestrians and fishermen from vehicular traffic. The new 195′ long six span replacement bridge features an all timber superstructure consisting of glu-laminated deck panels and stringers and an innovative hybrid timber deck and steel frame bascule span. The new concrete substructure is supported by driven steel pipe piles and showcases granite facing and concrete staining to provide the desired historic look of an old bridge, while providing the longevity and load capacity of modern materials.
The project was impacted by a third-party design delay which had the potential to push the construction and the full bridge closure and detour through the center of town into another summer tourist season. This option was not looked upon favorably by the Town of Chatham and the Massachusetts Department of Transportation, so the project team agreed that they could and would accelerate the schedule in order to open the drawbridge prior to the busy summer tourist season, essentially shaving five months off of the project schedule.
The work included driving and removing steel sheeting cofferdams in a marine environment; concrete formwork and placement; glulam timber work; treated timber work; and structural steel construction all within a salt-water marine environment and with work performed predominately during off-season time periods. SPS New England Safety Department implemented Daily Job & Safety Briefings, Weekly Job Hazard Analysis, Weekly Tool Box Talks, Bi-Monthly Safety Committee Meetings and Weekly Site Inspections to promote and maintain a safe culture on the job.
SPS New England was able to re-sequence the work in order to shorten the construction duration, enhance project safety and reduce potential for environmental impacts. We strengthened portions of the existing timber approach spans and used them as a temporary work trestle for cranes and heavy equipment during demolition, pile driving and bridge construction. This approach reduced barge based construction and avoided potential maritime construction traffic impacts on sensitive nearby shell fish habitat and eelgrass beds.
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