Water from Mill Pond no longer cascades over the historic Ambursen-style dam on the Oyster River. And the pond itself has disappeared, as crews gradually drained it over the past month to make way for the removal of the dam.
It’s quite a sight from the bridge that carries Route 108 over that part of the Oyster River. Construction equipment can now be seen near the middle of what once was the pond.
When the dam is finally removed by late fall, it will mark the first time in over 400 years that this stretch of the Oyster River will flow freely again as a tidal river.
“This will be the first time the Oyster River has run free since the colonial settlers first began to dam the river there,” said Todd Selig, Town Administrator in Durham. “The ecosystem will transition to its natural state.”
Engineers have identified where the natural channel of the river is, and will re-establish it, Selig said, offering a project update during a recent phone interview.
Contractors lowered the water level of the pond by about 6 inches a day over the past month – waiting until the seasonal fish run was completed. This was also coordinated with experts from the New Hampshire Fish and Game Department, monitoring impacts for birds and mammals, where the waterway serves as a “wildlife highway.”
Selig’s updates he provides on the town’s website speak of ongoing “turbidity monitoring,” erosion and sediment control, and note the initial dam breach will begin as early as the week of July 13.
Mill Pond Road has closures. There is a detour in that neighborhood, which is a stone’s throw from Durham Town Hall.
The $3.1 million project, with 60% being covered by grant sources, will mostly be wrapped up by this fall, with some native planting planned for spring of 2027, according to Selig.
There will also be a historical interpretation process, including history of the dam and a taping of the sound of the dam. Part of the dam will be preserved as part of that process to help people understand its role, Selig said.
The dam, built in 1913, has a structural height of 13 feet and it stretches about 140-feet across the Oyster River, a river that begins in Barrington and also flows through Lee and Madbury.
The project aims to improve water quality and wildlife habitat, and fish will migrate naturally, instead of with a fish ladder.
“It’s a very exciting time for naturalists and environmentalists who really see the value in restoring rivers to their free-flowing conditions,” Selig said.
This development did not happen overnight, and it did not come without controversy. Some residents wanted to keep the dam, and preserve the pond above it for its beauty and for recreational activities.
Almost a decade ago, the New Hampshire Department of Environmental Services identified problems with the dam. After an inspection, DES cited flaws such as concrete degradation and exposed rebar in the dam, and highlighted the need for repairs or reconstruction.
In 2021, the Durham Town Council voted 7-2 to remove the dam. Opponents gathered over 1,000 signatures for a petition to call for a referendum vote of the town. “People feel that this movement of taking all the dams down should not apply to Durham,” one of the petition supporters said at the time.
In 2022, the town voted overwhelmingly in support of removing the dam.
Over the past two decades, some other Great Bay tributary rivers with similar dam impoundments have been revisited. They include the Winnicut River Dam in Greenland, which was removed in 2009, and the Great Works Dam on the Exeter River, which was removed in 2016.
Dams limit access to spawning habitat for fish that migrate between freshwater and salt water. Removal of the Oyster River Dam will improve access to approximately two miles of habitat in the lower river, according to Fish and Game. In its assessment, Fish and Game said that a faster stream flow following the dam removal will likely favor blueback herring over alewives.
Fish and Game says the Oyster River is primarily considered a blueback herring run, though alewives have been observed in the fish ladder at Mill Pond.
The Oyster River gets its name from its shellfish. It was an important waterway for Native Americans going back 11,000 years, according to the state DES history of the river. Indigenous people here called it “Shankhassick.”
