Dec. 09–WESTERLY, R.I. — In just over a week, workers will restore the path of the Pawcatuck River and allow it to start flowing over the rocky fishway that is nearing completion where the Bradford Dam once stood.
But don’t expect a deluge of water to come barreling through all at once. It will be a trickle and it will take some time to fill the newly sculpted riverbed.
“Bring a lunch,” said Suzanne Paton, senior biologist with the U.S. Fish and Wildlife Service.
“And a dinner,” added Scott Comings, associate state director of The Nature Conservancy.
Although it won’t be a visually astounding event, the release of the river will be momentous all the same. It will signal the end of a decades-long series of projects by Fish and Wildlife, the Conservancy, the Wood-Pawcatuck Watershed Association, the R.I. Department of Environmental Management and others to restore fish passage along the 34-mile-long river that is the heart of the largest watershed in Rhode Island.
Three of the six major dams on the Pawcatuck have been removed, while the three others all have fishways, meaning that this spring after more than a century, alewife and blueback herring, as well as trout and shad, will be able to swim up the entire length of the river to their historical spawning grounds.
That is expected to have benefits throughout the ecosystem. Shad and herring are a critical link in the food chain, serving as prey for predators such as striped bass and bluefish, wading birds, ospreys and seabirds. If the project boosts the numbers of migratory fish in the Pawcatuck, it will help all the animals that depend on them, not to mention the recreational and commercial fishing industries.
The new fishway consists of six rows of boulders with gaps in between each row and a notch cutting down the center of the rows. The river will wash over the boulders, its waters slowed enough to allow weak-swimming shad and herring to move against the flow.
Pools will form between the rows, or weirs, giving the fish a place to rest on their way. And when the river is low, they will be able to swim straight up the notch.
Because the first weir will take the brunt of the river’s force, it’s reinforced with a sheet-pile wall that’s been driven some 15 feet into the river bed. Rocks will be aligned along the wall to hide the steel reinforcement. The boulders in the descending weirs weigh between 5 and 8 tons each and will also be able to withstand extreme flows that will come with heavy storms.
On Friday morning, the six top weirs were visible, while the bottom two were just underwater. A worker with contractor SumCo Eco-Contracting sprayed sediments in between the rocks to lock them together. When the project is complete, only the crowns of the rocks will be visible above the waterline.
The engineering of the fishway got its first big test during the rainstorms in late October. Everything held together well, though the channel that was dug out to redirect the river had to be reinforced with stones after flood waters threatened to wash away its banks.
The section of the Pawcatuck in Bradford started to industrialize in 1780 with construction of a sawmill on its north bank. A century later, the Bradford Dyeing Association mill went up on the opposite bank, and the river was dammed to power the sprawling complex.
Over time, after construction of the dam, a pond and wetlands formed behind it. Although it’s not a natural creation, the area has become home to birds and fish and so it is being preserved as part of the project. The rock weirs are being constructed in such a way to maintain the water level in the pond.
“There’s really sensitive habitat there now,” Paton said. “You have to weigh the balance.”
The $1.8-million project is being funded in part through relief money allocated by Congress after superstorm Sandy. One of the program’s goals is to alleviate flood risks in vulnerable areas.
So, as part of the Bradford project, an open-air mill race that ran into the factory buildings now operated by Bradford Dyeing and Finishing was replaced by a closed culvert. The bank along the complex was also widened to about 15 feet.
And the demolition of the rock-and-timber dam removed a potential flood hazard, too. It was crumbling and if it had collapsed, a torrent of water and debris would have washed downstream.
If the testing of the river’s flow — set to take place around Dec. 18 — goes well, then the bypass channel will be filled in and construction work should finish up by the beginning of the new year.
In the spring, Paton will work with researchers at the University of Rhode Island and other groups to tag fish and monitor where they go to help determine if the fishway is working.
“It should help every species that uses this habitat,” Comings said. “You had a wall that impeded their movement.”
On Twitter: @KuffnerAlex