by Ravi | November 5, 2025 | Carlisle Mosquito

The Conservation Commission (ConsCom) heard a presentation from Dan Cook, the town’s representative to the Sudbury, Assabet, and Concord Wild and Scenic River Stewardship Council, regarding a request from the Council for a letter of support for the removal of the historic Talbot Mill Dam in Billerica.

According to Cook, the project would represent “the most extensive restoration of migratory fish breeding habitat of any dam removal project in Massachusetts.” The removal would open 399 square miles of habitat, including about 100 miles of tributaries, 35 miles of mainstem rivers, and 260 acres of lakes and ponds across the Concord, Assabet, and Sudbury Rivers.

The lengthy effort to remove the 314-year-old Talbot Mill Dam has completed extensive studies and permitting. “We’re just about to get it over the hurdle,” Cook said, “and the Billerica Historical Committee decided that they had jurisdiction and jumped in.” A hearing on that jurisdictional question has been scheduled for December 1.

Cook explained that the removal of the dam would particularly benefit alewife, a migratory fish species. “For the last four years, I’ve been trying to count alewives coming up through a fish ladder,” he said. “We have seen none.” Once the dam is removed, Cook said that “hundreds of thousands of alewives” migrating up the Merrimack River would be able to access the Concord River and its tributaries.

Cook also discussed broader ecological benefits, including water quality improvements through freshwater mussel activity. “Freshwater mussels filter as much as 20 gallons of water per day,” he said, describing how mussels depend on fish migration for reproduction and dispersal. 

He said the dam’s private owner supports the removal and has cooperated with project leaders. “All the environmental studies have been done,” Cook said, adding that “part of the dam will still remain.” 

ConsCom Chair George Shepherd asked, “So, you’re only taking down part of it?” Cook replied, “They’re taking most of it down. It’s just a little section they’re going to keep for historical perspective.” Shepard also asked whether the mussels in question were invasive zebra mussels. Cook assured him they were not.

ConsCom member Brian Murphy said that he wanted more information on the potential effects on wetland species upstream before the commission voted on a letter of support. Cook responded that the impacts would be “primarily very, very positive,” noting that water levels would change only about four inches because of a natural dam farther upstream.

ConsCom member Melissa Webster asked whether the project would benefit other species such as shad, river herring, or Atlantic salmon. Cook replied, “That would be nice; salmon don’t come up the Merrimack River, unfortunately.” 

Cook added that the Talbot Mill Dam is “the primary dam that’s really blocking the way” for migratory fish. A smaller dam upstream, the Centennial Dam, already has a fish ladder project in progress. He confirmed that the dam, built in 1711, had undergone changes but continued to block fish passage since that time.

The ConsCom agreed to place the item on the commission’s November 6 agenda to allow members time to review the materials. 

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