“All those dams were built to power mills during the Industrial Revolution, but the mills aren’t in operation any more and the dams no longer serve an industrial function,” said Scott
associate director of the Rhode Island office of The Nature Conservancy, which
is a partner in several dam removal projects. “Dam removal is beneficial for
flood abatement, it reduces the risk of dam failure, and reconnecting the river
is important for target fish species like river herring and shad.”
|Bradford Dam prior to removal (Ayla Fox)|
The Pawcatuck River has been the main focus of dam removal efforts in the region for several years. The White Rock dam – the first obstruction that fish encounter as they try to make their way upriver – was removed in 2015. The Potter Hill dam, a few miles further upstream, was left in place, but improvements were made to its fish ladder in 2016 after sediment build-up around the ladder created what Comings called a reverse eddy, which spun the fish around and directed them away from the ladder.
The next dam on the Pawcatuck, the Bradford dam, was removed last year in a six-month project that involved construction of a temporary bypass channel to divert water around the dam, demolition of the dam, and the repositioning of hundreds of boulders into the river to create a series of step-like weirs and pools to enable fish to swim upstream. It also allows canoes and kayaks to navigate the waterway safely without portaging and reduces the risk of upstream flooding.
“Connectivity is the golden word in this project,” Comings said. “By reconnecting the river, everything that depends on the river will benefit – not just the fish, but freshwater mussels, mammals, reptiles, birds and amphibians, too.”
The next dam to be removed in South County is in North Kingstown adjacent to the Shady Lea Mill on the Mattatuxet River. The former textile mill is now being used as artist studios. Following the 2010 floods, the state inspected the dam and deemed it a high hazard, which increased the liability on the dam’s owner and required preparation of an emergency action plan. The owner ultimately decided to have the dam removed, and she is working with Save the Bay to complete the project this year.
“We’re always looking for good habitat restoration sites,” said Rachel Calabro, Save the Bay’s Riverkeeper and the coordinator of the Shady Lea project. “There’s a large fish run just downstream at the Gilbert Stuart Museum, and this will open up another half mile of the river for herring, eels and trout.”
Work began last October, when a section in the middle of the dam was removed to lower the water level behind the dam so the sediments could dry out. It also allowed archaeologists to examine and photograph the historic dam, which was found to have been originally constructed of fieldstone in the 1800s and later capped with cement.
This spring and summer, contractors will remove the sediments, which have already been tested and found to be free of contaminants, and then the spillway will be dismantled.
“We can already see that the stones are really loose, so I know when we go in to remove it, the dam will come down in a day,” said Calabro. “Some of those stones will be placed in the channel below the dam to create pools and make riffles in the stream for the fish to navigate. That’s the finesse part of a habitat restoration project like this.”
Once the dam is removed, Calabro said that native plants will sprout to revegetate the site.
“We’ll let the river naturally find its channel, and we’ll end up with a nice stream running through a vegetated wetland,” Calabro said.
Save the Bay will use this project as a showcase of dam removal techniques to encourage other private dam owners to undertake similar efforts to remove their liabilities and restore habitat.
“We’re not just interested in getting fish from point A to point B,” Calabro said. “We want native species to be able to migrate and also have better water quality, better dissolved oxygen, and the other things that happen when you remove a dam. We’re always looking for opportunities to improve stream health, which also improves resilience by removing vulnerable infrastructure.”
Not every dam in the region can or should be removed, however. Some deserve to be protected for their historic attributes, for aesthetic reasons, or because there are alternatives to removal.
“Every site is different,” said Andres Aveledo, a conservation engineer for The Nature Conservancy and the Rhode Island Department of Environmental Management. “The best conservation alternative is through removal of the dam, but we sometimes select alternative approaches because stakeholders want the impoundment to remain.”
The dam on the Saugatucket River near Main Street in Wakefield, for instance, is on the state’s list of historic places, and the town of South Kingstown did not want to lose its attractive waterfall. Yet the site’s fish ladder, which was built in the 1960s, was not working. So in 2016 the fish ladder was re-engineered to ensure more herring make it over the dam and into Indian Lake.
A similar effort is planned this year at the 12-foot dam at the Palisades Mill Complex in Peace Dale, enabling fish to swim even further up the Saugatucket.
And in Charlestown, fish now have better access to Factory Pond from Green Hill Pond and the Charlestown Breachway, thanks to an aluminum device called a steep pass that was installed in 2017 to help fish surmount the modest private dam on Factory Brook.
“That little run can now support about 20,000 river herring,” said Aveledo. “That’s a lot of bang for our buck.”