A community divided by a derelict dam
Melissa Paly of the Conservation Law Foundation (left) attends a Valentine’s Day rally to campaign for removal of the Mill Pond Dam. (Amanda Gokee | New Hampshire Bulletin)
The town of Durham is divided over the fate of the historic Mill Pond Dam, as residents and environmental organizations pushing for its removal have met with resistance from a group intent on its preservation.
After the town council voted, 7-2, in favor of removing the dam in September, proponents of keeping it gathered around 1,000 petition signatures, enough local support to put the question on a referendum for town meeting voters this month.
The fight over what to do with the dam in Durham illustrates a larger issue, with 2,617 active dams altering the natural flow of waterways across the state. And there are more than 1,000 other “exempt” dams – they no longer meet the state’s definition of a dam but can still create significant environmental impacts, according to Bill Thomas, the river restoration coordinator for the Department of Environmental Services.
Thomas’ position at DES was created in the early 2000s, when there was a growing movement around the country, and especially in New England, to remove obsolete dams that had fallen into disrepair. At that point, many dams were already 50 years past their expected lifespan, Thomas said, and had reached a breaking point that required action.
“There’s been an environmental movement to restore connectivity and flood resiliency … to try to make them a better system,” said Thomas, also noting that often the owner of a dam doesn’t have money for ongoing, and often expensive, maintenance. When removing a dam creates environmental benefits, there’s typically grant money available to pay for it. And that’s especially true now with funds specifically set aside for this purpose in the bipartisan infrastructure bill that recently passed Congress.
The National Oceanic and Atmospheric Administration received $400 million for its community-based restoration grant program to restore fish passage; the U.S. Fish and Wildlife Service got another $200 million for its national fish passage program; and $115 million went to the U.S. Army Corps of Engineers for its aquatic ecosystem restoration program. Additional funds were earmarked for dam safety – including $678 million for FEMA’s national dam safety program.
Dam removal has become a priority for some environmental groups, such as the Nature Conservancy, because of the damage to ecosystems caused by leaving derelict dams intact, and the benefit of restoring the natural flow of rivers around the state.
New Hampshire politicians have also taken up the issue. Last summer, Rep. Annie Kuster introduced a bill to provide for the rehabilitation, retrofitting, or removal of around 2,500 dams in New Hampshire – and some 90,000 across the country – citing climate, energy, and safety reasons for doing so. Some dams can be dangerous; 169 New Hampshire dams are rated as high-hazard dams that would likely cause loss of human life were they to fail. (Mill Pond Dam is rated as a low-hazard dam, which could create damage to roads but wouldn’t pose a risk to human life were it to fail.)
Fish and climate change
In Durham, the environmental stakes are high because the Mill Pond Dam holds back a head of the tide river, creating an artificial barrier in the estuary where freshwater and saltwater would naturally converge and preventing fish that spawn in fresh water from reaching it. Thomas said removing dams that fall along the head of the tide can provide a significant environmental benefit.
“Whenever we have a dam that is at the head of the tide and blocking clear passage to those fish upstream, it’s obviously a higher priority structure,” Thomas said.
Dam removal is especially important in preparing for climate change, said Jim O’Brien, director of external affairs at the Nature Conservancy in New Hampshire. Removing a head of the tide dam could improve the area’s resiliency, to help prevent flooding and to allow salt marshes, an important part of the local ecosystem, to migrate up the riverway as sea levels are projected to rise. A dam would block that from happening.
Melissa Paly, the Great Bay-Piscataqua waterkeeper with the Conservation Law Foundation, called the Mill Pond Dam in Durham a disaster for fish. While a fish ladder was built in 1974, fish are able to traverse it only with the help of people wielding nets to give them a lift. Some fish are able to spawn but then die if the water is too low and they can’t make it back to sea. Water quality in the pond created by the dam is another problem; it’s been designated as impaired by the state, and Paly said there’s so little oxygen in the water it can also kill the fish. Algal blooms are another problem, and over time, the pond is filling up with sediment. Flooding, Paly said, happens down river when there’s a high tide and the water is stopped short of the floodplain by the dam.
“With climate change and sea level rise, having the river function as it should – as a tidal river – will be more resilient, an improvement for the community,” said Paly, who has been a vocal advocate of removing the dam in light of these issues.
The dam divide
The dam itself is deficient – it hasn’t been up to state standards since the early 2000s, with inspections in 2017, 2019, and 2021 all revealing continued structural deterioration, according to the town of Durham. “The concrete is crumbling,” said Sally Tobias, who is on Durham’s town council and voted in favor of removing the dam. The town has spent around $500,000 on several studies to examine the issue, and Tobias said that for her, after extensive study, “I don’t even really see it as a choice; I see it as just simply the right thing to do.”
She recognized that people are attached to the dam as a historic landmark – it’s recognized by the New Hampshire Division of Historical Resources. But the maintenance options discussed would involve encasing the dam in concrete in order to reinforce it, an option Tobias saw as ruining the historical character of the dam that some are intent on preserving. And the town’s studies raised concerns of future flooding in the event of a 100-year flood. For Tobias, removing the dam is the sustainable thing to do.
Proponents of keeping the dam intact are unpersuaded by those arguments – and raise climate counter arguments of their own. In a future with increased drought, they say, having a dam will keep the river from running dry. Jeff Hiller is one Durham resident who has rallied to preserve the dam, creating a website for the cause: Save Mill Pond Dam.
In the nearly 375 years that there has been a dam of some sort on Oyster River, it has become a local landmark, and residents have fond memories of skating on the pond in winter or canoeing on it in the summer. The most recent structure was built in 1913, replacing a series of timber dams dating back to 1649, according to the Durham Historic District.
“I drive by it so many times a day. It’s breathtaking,” Hiller said. To him, the dam is a town treasure that should remain intact. He agrees that something needs to be done to address water quality issues and the state of disrepair the dam is in but would prefer the town repair the dam rather than do away with it. And Hiller points to a 2014 study by the town showing that the poor water quality in the pond is linked to phosphorus coming from College Brook. He says the pollution should be addressed at the source.
“I look at the dam as a messenger. It’s telling us in no uncertain terms, we have a huge problem,” he said. Without the dam, he said, pollutants would flow from Oyster River directly into Great Bay. “It’s telling us: ‘You guys need to stop polluting your watershed.’”
One study commissioned by the town estimated that to improve water quality in Mill Pond, phosphorus loading would have to be cut by 53 percent or 2,685 pounds per year: a multi-town effort that would have to include towns across the watershed, including Lee, Nottingham, Barrington, and Madbury.
But some environmentally minded Durham residents agree with Hiller – including Nancy Sandberg, who was instrumental in the successful fight to keep an oil refinery out of Durham in the 1970s. Sandberg now serves as the curator of the Durham Historical Association, and supports preservation efforts of the dam as a historical, cultural, and recreational resource.
“When dams are protecting water supplies or critical estuarine environments, they should not be removed,” she said, pointing to past pollution locked in the pond’s sediment that could be released downstream if the dam were removed.
There isn’t heavy industry around the river, but agricultural runoff containing pesticides has made it into the waterway. Sandberg also pointed to a local laundry that dumped its waste into the river, and levels of mercury that have been found in the sediment.
Sediment sampling by the town found polycyclic aromatic hydrocarbons – a class of chemical that is naturally occurring in coal, crude oil, and gasoline – in Mill Pond and downstream of the dam. Burning these materials also produces PAHs, as does burning wood, garbage, and tobacco, and according to the CDC, the health effects of environmental exposure to PAHs is unknown. Additional sediment testing would be required by the state to determine if special disposal of the sediment is necessary as a part of the dam removal process, according to the town.
And Sandberg and Hiller both feel the debate has wrongfully ignored the presence of another UNH dam, about a mile upstream. That dam, they say, would prevent the Oyster River from truly running free. Thomas, who works on dam removal for the state, said removing the lower dam would improve water quality and fish passage, in turn creating an incentive to address low flow concerns from the upper reservoir and to investigate fish passage at that dam.
Ultimately, the question will be put to voters to decide. But the divide in Durham, which has created rifts in friendships and left the town’s historical association and conservation commission on opposite sides of the issue, makes clear that the decision will not be an easy one.
Our stories may be republished online or in print under Creative Commons license CC BY-NC-ND 4.0. We ask that you edit only for style or to shorten, provide proper attribution and link to our web site. Please see our republishing guidelines for use of photos and graphics.