A 300-foot-long earthen dam in Bear Brook State Park may be removed next year as part of efforts to take out some of New Hampshire’s hundreds of outdated dams.
But if you’re afraid of what removing the dam on Catamount Brook will do to Hayes Marsh, don’t fret: Beavers will probably replace it.
“We really think that beaver will move right back in and create some sort of natural beaver pond,” said Charlie Krautmann, chief of engineering and construction for the state Dam Bureau. “The marsh will be healthier, with more dissolved oxygen in the water. Most of the wildlife would appreciate it going back to its natural state.”
The Hayes Marsh dam is one of more than 275 that the Department of Environmental Service’s Dam Bureau manages in cooperation with several state agencies including the Fish and Game Department and the Department of Natural and Cultural Resources. Most are small and were built decades ago, and they have often outlived their original purpose, such as powering a mill or creating a drinking water supply that is no longer used.
From an environmental perspective dams chop up creeks and streams into segments, making it hard for fish and invertebrates to move and limiting the dispersal of nutrients. Dams can also be dangerous if they fail and release the water backed up behind the dam all at once.
A 2023 study estimated it would cost $414 million to bring all these dams up to date with modern safety standards. That’s why the state is getting rid of some.
New Hampshire isn’t alone in this. Around the country, many governments and environmental groups are removing old dams.
Some projects can cost millions of dollars, such as taking out three huge dams on the Klamath River in the Pacific Northwest or the removal of dams and culverts on the Penobscot River in Maine. The latter has seen huge environmental returns, notably a resurgence of migrating alewife in numbers not seen for a century or more.
The Hayes Marsh dam removal is not in that ballpark. Final cost depends on more details but it will probably not be much more than $100,000, Krautmann said.
It is one of four small removals proposed for next year, all of them involving earthen dams built in the 1960s with corrugated metal pipe outlets which have outlived their normal service life.
Besides Hayes Marsh, the other removal projects are the Bellamy River wildlife pond in Dover, Hoyt Pond in Madbury and Adams Point Wildlife Pond in Durham. The cost of each project will depend on details, such as whether pedestrian bridges must be built, but will be in the “five- or six-figure range,” Krautmann said.
“This is low-hanging fruit,” he added.
In accordance with state law (RSA 482:13), the Dam Bureau will notify the public of the drawdown of water behind the dams and have public meetings, probably this fall or winter. The goal is to remove the dams next year.
David Brooks can be reached at dbrooks@cmonitor.com
