The sinkhole is filled, the visitor center didn’t miss a beat, and the contractor is digging again on Water Street in a sprint to the finish for the long-delayed, troubled effort to replace an aging sewer pipe that runs under part of the harbor.
“As of Tuesday, there were no immediate indications that construction activity posed a concern, and the project was cleared to proceed,” Plymouth Department of Public Works Director William Coyle wrote in an email to the Independent.
The project has been plagued with a series of problems almost since the beginning, prompting infighting and finger-pointing. The latest snafu first surfaced Tuesday, Sept. 29, when a survey crew doing regularly scheduled measurements in the construction zone reported the southeast corner of the Plymouth Waterfront Visitor Center on Water Street had dropped nearly 2 inches from the previous reading.
Then, on the afternoon of Friday, Oct. 2, part of the asphalt in the parking lot behind the center cracked and fell in, revealing a 3-foot-deep sinkhole, which has since been filled and paved over.
As a result, the contractor shut down the dewatering wells installed in the construction zone that draw down groundwater to allow for stable digging. The town then ordered a survey of the area with ground-penetrating radar to search for other possible voids in the ground that could be problematic.
The radar survey was done on Friday, Oct. 9. A preliminary report found no additional problems, officials said, but “the town has not yet received the (final) radar report, which will provide additional information to help assess the situation,” Coyle wrote. “It is possible that the sinkhole developed over an extended period, and vibrations associated with the sheet pile installation may have exacerbated an existing condition.”
While a survey team reported a corner of the visitor center had dipped nearly 2 inches, that measurement may have been an outlier.
“The visitor center had four targets, placed on each corner of the building. The initial evaluations were established in December 2025, when the temperatures were in single digits. Then, in the fall, one corner of the visitor center showed a 1.8-inch drop,” Coyle wrote.
“This corner was the one most exposed to the winter elements,” Coyle continued. “It is very possible that this movement was caused by the freeze/thaw cycle as there are no physical signs of structural damage in or around the building. Out of an abundance of caution, the town will continue to monitor the building for any changes.”
In this final phase, the contractor, Northern Construction, is to replace the last 70 feet of sewer pipe – out of the quarter mile of new pipe already installed – because it had settled more than expected into unstable soil. That last 70 feet runs in front of the visitor center near the rotary at Water Street and Town Wharf.
The project’s objective is to replace an aging quarter-mile section of 30-inch sewer pipe installed in 1969 that runs under the edge of the harbor adjacent to Water Street. Town officials were concerned a break in the old line would be an environmental disaster for the waterfront.
Work began in December 2022 and was supposed to be finished by the end of June 2023. But in March 2023, during the first phase of excavation, groundwater problems, shifting soils, and damage to the street, sidewalks, and five buildings on Water and Chilton streets forced a shutdown of the project.
One building was damaged so badly that it had to be razed. The owners of the affected buildings are suing both the town and Northern Construction, seeking more than $5 million in damages.
Michael Cohen can be reached at michael@plymouthindependent.org.