CHATHAM — In the latest effort to fix the sticky Mitchell River drawbridge, crews will begin major repairs on April 8 which could take nearly two months to complete. During that time, Bridge Street will be closed to through traffic.
On Monday, MassDOT officials notified the town that the bridge contractor, SPS New England, will be on site starting April 1, installing detour signs and informational message boards. The following week, they will begin the process of removing the top deck, which will allow “significant work” to the structure underneath in a bid to address the problems that have caused the movable span to stick in the closed position or to not fully close after opening.
Crews plan to have the work complete by May 26, the Memorial Day weekend.
Coastal Resources Director Ted Keon said he is not concerned that the project might extend beyond that time.
“This is, we hope, a worst-case timing scenario,” he said. Keon spoke with the MassDOT project manager, “and he’s hopeful that it would go sooner than that.”
Several times since the $14 million bridge was opened in June 2016, the contractor has returned to shave some of the wooden joints. The town owns the bridge, but MassDOT has acknowledged design problems and has committed to fixing them.
The Bridge will be in the closed position affecting larger vessels utilizing Mitchell River. Access for larger vessels will be contingent upon 48-hour notice to the
Chatham Harbormaster. The channel will remain open for smaller vessels to transit with appropriate caution.
In a compromise with preservationists who wanted a replacement bridge to be made entirely out of wood, engineers designed a span with a steel-and-concrete substructure that supports wooden deck panels. The wear surface, the top planks that vehicles pass over, rests on top of the deck panels. Parts of the bridge expand laterally during periods of high humidity, and other parts expand longitudinally, causing the movable span to bind. Most of the longitudinal swelling has been addressed, but the lateral swelling still causes the span to hit the fixed sidewalk areas, Keon said.
The work will require the removal of the surface deck to allow access to the panels underneath, which will then need to be shaved to size.
“It’s a fairly extensive process,” Keon said.
While Keon said he knew that some repairs were being planned, town officials only learned about the April 1 start date on Monday. After crews made temporary repairs last fall, engineers and state officials determined that a more substantial repair was needed to permanently fix the problem. “They couldn’t do it in the dead of winter,” Keon said.
Informational signs will be installed near the lighthouse and at the Doc Keene Scout Hall alerting motorists to the bridge closure. The road will remain open for local traffic from the north and south. Public safety officials, including the fire department and the Coast Guard, will have plans in place for responding during the bridge closure.
The span is very carefully balanced so that it requires very little power to open and close it, a job that can actually be done with a hand-held drill in the event that the motor fails. But in humid weather, the span is sometimes difficult to open, and then will not seat itself in the fully closed position. If the bridge doesn't lower fully, locking pins do not enter the sockets designed to receive them, and that prevents the safety gates from automatically opening, as well as several other problems. Occasionally, bridge operators have had to drive vehicles on top of the span to force it to completely close.
Keon said he’s glad that MassDOT is standing by the project.
“They’ve been quite responsive. They have not tried to walk away from these issues,” he said. Designers knew that the unique bridge could have problems related to timber swelling and made some provisions in the design to address those problems, but the swelling was more severe than anticipated.
“I think this just caught all these design engineers off guard,” Keon said.
The bridge was entirely funded by the Massachusetts Department of Transportation through the federal Accelerated Bridge Program. It took more than six years to design and build the span, thanks largely to contentious negotiations over a design that would be both functional and historically sensitive.
This article was updated on 3/28/19 to include new information.