It was just a trickle at first, but around 3 p.m. on Wednesday, Aug. 15, water breached the Cannondale Dam. It was the first time in some three centuries that the Norwalk River flowed unencumbered through the stretch.

It was just the latest breakthrough in the process of removing old dams, no longer in use, to open the river to migratory fish. Like that trip, dam removal is a meandering trip, sometimes upstream.

A quarter century ago, Wilton native Jeff Yates was just becoming an angler and member of Trout Unlimited, and talk began of removing dams along the Norwalk River.

“The Mianus Chapter started talking with the DEP, town of Wilton, private landowners and USDA’s Natural Resources Conservation Service when I was about 11. I’m 37 now, so 26 years since we started conversations about removing these dams, and the process has taken lots of twists and turns. Dam removals are often challenging for many reasons.”

First, Yates said, removing a dam is expensive. Water upstream has to be tested for contamination before any work is done. A solution must be engineered so removal of the barrier will not cause any downstream flooding or disturbances.

“Once we have a viable project, it’s usually five years,” said Steve Gephard, supervising fisheries biologist for the Connecticut Department of Energy and Environmental Protection, who was there when the dam was breached.

“The problem is, when do you start? All of these projects we are doing are voluntary,” he added.

First, Gephard said, is negotiating with the owner of the dam.

Then money must be raised, usually through grants, as was done for Cannondale. The project is engineered, a final cost is determined, money is raised again and final permits are secured, Gephard said.

With the Cannondale Dam, Yates said the landowner, “who’s been wonderful with us since the beginning,” wanted to keep the mill pond and his view of it, so a bypass channel that preserved the pond was constructed.

“That fellow isn’t wedded to the dam anyway, and Mother Nature put a hole in it and it wasn’t holding water anyway,” Gephard said.

That fellow is Marc Gueron, who owns Cannondale Village. “A dam or waterfall is pretty, but there are complications,” he told The Bulletin. “Ponds fill up and can become like swamps in the summer. Maintenance is difficult.”

“The riverbed looks very pretty,” he said of the project, and when it is complete there will be grass down to the river “like a park, but a flood basin when needed.”

Eventually, the dam, which is six feet tall and 60 feet wide, according to Gueron, began to fail and needed to be removed in its entirety.

“Now we have full fish passage,” Yates said. “It’s a cool thing, it’s a very cathartic thing to see happen.”

The dam in Cannondale had been in place since the 1890s, preventing fish from getting upstream “whether they were coming in from the ocean or were fish that lived here in the river,” Yates said.

Trout were not the only species affected. Eels, lamprey, herring, alewives, sculpins and others were physically prevented from accessing the entire Norwalk River system.

“When fish can’t move through an entire ecosystem, they have a challenge surviving at different times of the year,” Yates said. He explained that fish need to swim upstream to spawn, downstream to find cooler water during summer droughts, and to other spots to raise their young or hide from predators.

“Dams block that from happening,” Yates said.

“Obviously there’s good fishing in the Norwalk River now, but by getting rid of these dams we let more fish come up, more nutrients come up, cool down the Norwalk River, make it more suitable for the trout,” Gephard said.

Fewer dams should also mean more fish.

“These dams have been holding back fine sediment, and we know trout need clean substrate to spawn in,” he added.

With a barrier in place, sand and small rocks in pebbles from which trout create nests, called redds, get trapped behind the dam. The streambed beneath becomes large stones and bedrock, with no spawning habitat, Gephard said.

“When you remove the dam and get natural sediment transfer going, you get pockets (where trout can spawn),” he said.

Removal of the Cannondale Dam opened another five miles of the Norwalk River in Wilton, and combined with recent demolition of the Flock Dam in Norwalk, near Merritt 7, has opened access for fish from the Long Island Sound to Georgetown.

Next on the list to come down is the Dana Dam at Merwin Meadows. On April 16, the Board of Selectmen gave authorization to sign permit applications for removal of the dam originally built by Charles Dana to create a skating pond for his children.

That project could be complicated, Gephard said, and could cost as much as $1.5 million. Most grants, relied on heavily to pay for dam removal, cap out at $250,000, he added.

“We need to sharpen our pencils on that,” Gephard said, explaining that contamination is just one of the challenges.

“That’s going to get a bit more complicated because we do have a design,” he said, “but it’s an old design, and we don’t know if it’s going to be tweaked, and we know because it’s an old design it’s going to be expensive and we don’t have any money yet.”

“There are 20,000 dams across New England like the Cannondale Dam,” Yates said. “One of the challenges we face is they take a long time to come out.”

In the interim, he said, those interested in the health of fisheries and rivers can advocate for the removal of antiquated, disused dams.

“It’s one of the best ways to have an instant impact on an ecosystem,” Yates said.