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It took 300 years or so to block off nearly every New England stream larger than a trickle with walls of earth, stone and concrete.
Originally built to power mills or hydroelectric plants, or capture streamwaters into lakes and ponds for reservoirs, recreation and flood control, many of the dams have now outlived their purpose. Their owners are long gone, or unable or uninterested in investing in repairs.
Now, a decade into a movement to dismantle obsolete dams wherever feasible, Linda and Bill Rutan of Pawcatuck are poised to become some of the latest contributors to the trend.
"After the floods in 2009 and 2010, we started to see the fragility of this whole thing," said Bill Rutan, standing atop the warped earthen wall of a 100-year-old dam that pools the waters of Anguilla Brook into a small pond. Nearby were a row of sandbags and a couple of man-sized holes that remain from the deluges.
Repairing the structure would be prohibitively expensive for the couple, but leaving it as is would risk a potentially dangerous collapse of the dam next time the brook swells with floodwaters.
"It's had some years of neglect," he said.
Because the brook empties into a tidal cove and historically was an important passage for migratory herring and eels - the name "Anguilla" is biologists' nomenclature for American eel - the Rutans' dam turned out to be an ideal candidate for removal with the help of state, local and national groups that work on river and wildlife restoration projects.
Once the dam is torn down, which could be as soon as this summer, and a fish ladder built over another dam downstream, herring and eels will be able to swim unimpeded from Long Island Sound to ancestral waters near Route 184, where they spend their adult lives. And with the brook once again flowing, the water and habitat quality for river species are expected to improve.
"With two relatively small activities (the dam removal and fish ladder installation) we'll open up a whole basin for fish habitat," said Duncan Schweitzer, vice president of the Avalonia Land Conservancy, a local group that's one of the partners in the Rutan dam project. "It's cost-effective restoration."
Engineers are working on plans to execute the step-by-step dismantling of the dam, starting with a drawdown of the pond behind it. Applications have been submitted for the required state and federal permits. Along with Avalonia, which recently received a $75,000 state grant toward its part of the work, the state Department of Environmental Protection, the U.S. Fish & Wildlife Service and the Nature Conservancy are partners in the project. The remainder of the costs will be covered with other grants and contributions of expertise from the various partners.
Brian Graber, Northeast river restoration program director for the nonprofit group American Rivers, traced the recent surge in interest in dam removal to 1999. That year, federal utility regulators ordered an old hydroelectric dam on the Kennebec River in Maine removed for ecological reasons. It opened 17 miles of fish habitat, sparked the return of species such as shad, striped bass and herring and turned the area into a hub for recreation. Since then, according to American Rivers, more than 450 dams have been taken down nationwide, 60 of them in 2010 alone, as more groups realize how collecting water behind so many dams diminishes water and habitat quality and biodiversity.
Native fish and other aquatic populations become genetically isolated from one another, and migratory fish that are important food for wildlife can't reach spawning areas and carry micronutrients from marine waters to freshwaters upstream. Additionally, the many dam blockages are believed to be one of the factors that have caused the declines of species such as river herring.
While the Rutan dam may be relatively small compared to others that have been demolished around the country in recent years, its upcoming removal would occur during a banner year for dam removals.
Several large, well-known and high-impact dams are also slated to come down in 2011, among them two on the Penobscot River in Maine and three in Washington state.
When the movement began, Graber said, dam removals were mainly being done as part of larger efforts to restore rivers and fish populations, and public safety was a secondary benefit. Now, the balance has shifted.
"The biggest issue now is public safety" because of the dangers of dams left in disrepair, particularly during floods, he said. "Our general feeling is that removal is the most cost-effective solution."
American Rivers has been a partner in two dam removal projects in southeastern Connecticut, both on the Eightmile River, which is one of two rivers in the state to be part of the National Parks Service's Wild and Scenic Rivers program. In 2005, a dam in East Haddam was taken down, and two years later, the Zemko dam in Salem came down in a project overseen by the Nature Conservancy.
Adam Whelchel, director of conservation programs at the conservancy, said his organization would like to see another Eightmile dam removed, at Ed Bill's Pond in Lyme. It considers the Zemko project a success, he said, based on the quick recovery of native plant and insect life to the area where a mill pond was located before the dam removal. The fish populations, however, are another story.
Barry Chernoff, professor of environmental studies and director of the College of the Environment at Wesleyan University, has been studying the fish populations in the section of the Eightmile where the Zemko dam was located since 2004. Chernoff said he's had some unsettling findings from comparing the numbers and diversity of fish before and after the dam removal, and comparing it to nearby control sites. That section of the river isn't used by migratory marine fish species, but is populated by native freshwater fish.
"Immediately the population below the dam dropped, and it became a very uninteresting community of brown bullheads and eels," he said, prefacing his remarks by saying that he has long been an advocate of removing dams whenever feasible. "The numbers of tessellated darters are much smaller than it was, and I'm not seeing blacknose or longnose dace. I am really worried that this little section of stream hasn't recovered in this amount of time. But the part that is recovering is the section above where the impoundment was. The question is, 'Why?'"
Sediments above the dam were tested for contaminants before the removal, Whelchel said, and no concerns raised, so he doubts sediment releases are affecting the fish. In addition, the pond was drained gradually so that as much sediment as possible would remain in place. Chernoff's work, which is continuing, demonstrates that more research is needed to understand the dynamics of dam removals and habitat recovery, Whelchel said. He remains convinced that given enough time, the fish populations will catch up with the rest of the restoration of the Zemko site.
"It's already exceeded our expectation as far as the vegetation, but it's too soon as far as the fish go," he said.
Also of significance to southeastern Connecticut is American Rivers' partnership with the Wood-Pawcatuck Watershed Association in last year's removal of the Lower Shannock Falls dam on the Pawcatuck River, a waterway shared by both states. On the association's website, one of several photos of the backhoes and bulldozers at the site is accompanied by an anecdote from a doctor who was passing by. He likened removing dams to repairing a clogged artery.
Across Connecticut, nine dams have been removed in the last decade, beginning with three on the Naugatuck River, said Steve Gephard, supervising fisheries biologist for the state Department of Environmental Protection. Six more projects including the Rutan dam are in the works, and several more are in early stages. One future project the DEP hopes to undertake would remove a series of dams from a stretch of the Moosup River in Plainfield.
With hundreds of old dams around the state to choose from and limited resources, Gephard said, the state picks its projects based on several criteria. The best candidates for removal have willing owners; are in areas important for fish habitat; can attract local, private and national partners; and don't have ponds full of contaminated sediment that would be expensive to dredge and dispose of, or better left in place. The contaminants are often the remnants of whatever industry was once located at the dam site.
"You never want to be in a position of letting those sediments go, because that could damage healthy habitat downstream," he said. He's seen good results from dam removal projects the DEP has been involved in, with native plants repopulating areas where dams had been located within a single growing season, and fish soon after learning that a new section of the river is now open to them.
The emergence of dam removal as a key tool in the river and fish restoration field, he said, is the result of a convergence of historical economic forces and wider recognition of the environmental and public safety benefits of getting rid of obsolete dams.
"From the mid-1700s until about 1920, we were building a lot of dams for specific purposes, and because people were making money from them, they were taking care of them," Gephard said. "When these companies went out of business, there was no longer anybody to take care of them. A lot of these are earthen dams, and they're like ticking time bombs. There's not a town or a watershed in the state that doesn't have a dam, and all streams have been impacted."