Dam removal: An engineer returns to restore a Connecticut river of his childhood
November 14, 2023
America¡¯s aging dams are coming down. Mike Chelminski returned to his childhood river and led a dam removal project to improve Long Island Sound.
There is a photo of a towheaded kid, circa 1970, hanging in my office. The picture is me, holding a migratory American eel that I caught in the Norwalk River in Connecticut, near Dana Dam. I am gazing at the slippery eel with a look of wonderment. Look closely and you can see an angler¡¯s excitement in those 8-year-old eyes.
Fast forward more than 50 years. I am a Â鶹´«Ã½ engineer who, like that American eel, has returned to my natal waters of the Norwalk River. I am leading an ecosystem restoration project to remove Dana Dam.?
America¡¯s old dams are coming down. For more than two decades, I¡¯ve been working on dam removals in mostly the US Northeast but also across North America. I¡¯ve witnessed how communities and companies are looking more closely at the financial and environmental costs of failing dams. They are realizing the benefits of removing these dams outweigh the costs of repairing them.
The author as a young boy, holding an American eel he caught in the Norwalk River.
Our team has been working for the past four years with our client, the nonprofit to design and plan for removing Dana Dam. In the summer of 2023, the dam was taken down. Our team has reshaped the stream channel, repositioned sediment, and restored the river upstream of the dam.
Removing dams for fish passage
When I was growing up, my dad tended dairy cows at what is now Merwin Meadows Park, a stone¡¯s throw or two from Dana Dam. I have great childhood memories of fishing for eels, white sucker, and trout in the river upstream and downstream from the dam.
But today, I¡¯m looking forward to the results of removing Dana Dam, which will give migratory fish access to the upstream five miles of the Norwalk River. Fish passage and ecosystem restoration are the top goals for dam removal across North America.
Removing dams is restoring thousands of miles of habitat for fish and other animals. Some migratory fish, like salmon, were nearing extinction because of dams. Organizations and government agencies are making it a priority to remove dams and old culverts to improve fish passage.
According to the conservation group American Rivers, engineers took down 65 dams in the United States in 2022. Removing the dams connected more than 430 miles of river in 20 states. In 2021, the number was 57 dams in 22 states and 2,131 reconnected river miles. STS has worked since 2015 to remove outdated dams in the Long Island Sound watershed. Their goal? To improve habitat for migratory fish, connect fragmented ecosystems, and improve water quality in the Long Island Sound.
Moving the Norwalk River channel away from railroad tracks helped prevent erosion.
The Dana Dam removal project is a notable example of a strong partnership between a nonprofit organization, the local community, and our team at Â鶹´«Ã½. Dam removal is complicated business. But with creativity, timeliness, and an eye on the budget, we worked with STS and the community and took down the dam and brought a section of Norwalk River back to life.
Working in communities, addressing infrastructure
Frank Dana, who once owned a home along Norwalk River, built his namesake dam to create a pond for recreation. The dam was not large. It was 12 feet high, 200 feet long, with a 5-foot drop of water. It was never used to generate electricity. The dam was in Wilton, a residential suburban community of 18,500, located about 10 miles upstream from Long Island Sound.
Dana Dam was small, but removing even a small dam in communities has challenges. It so happens that Â鶹´«Ã½¡¯s ecosystem restoration experts have plenty of experience removing dams in urban and suburban areas, such as the Elm Street Dam in Kingston, Massachusetts. One of the biggest projects I¡¯ve worked on was the removal of the Ballville Dam in Fremont, Ohio. It is one of the largest ecosystem restoration projects ever undertaken in Ohio. By removing the dam, we restored 22 miles of walleye habitat and spawning areas in an important commercial fishery in the Great Lakes.
America¡¯s old dams are coming down.
Existing infrastructure often poses a challenge to dam removal. Underground utility lines, nearby bridges and roads, residential and recreational facilities¡ªthey often require an engineer to find creative solutions. In the case of Dana Dam, we had to consider a commuter railroad along one shoreline and the popular Norwalk River Valley Trail on the other.
The railroad tracks were particularly challenging. Prior to our work, the tracks were just a dozen feet from the river flow. We determined that removing the dam would increase erosion along the railroad embankment.
We solved that problem with a design that moved the river channel away from 300 feet of railroad embankment to a smaller, existing channel just west of the railroad. In a sense, nature provided us with a viable solution readily on site. Moving the channel reduced potential for erosion and our design provides a more natural channel alignment and increases resilience to floods.
Our design also avoided impacts to the Norwalk River Valley Trail, and we worked around visits from school children to the area. We also provided three construction access routes to accommodate the contractor¡¯s work, which gave the contractor the flexibility to further reduce impacts.
Removing Dana Dam will help fish passage in the Norwalk River.
Sediment is a key dam removal challenge
One challenge with dam removal is dealing with the sediment that has built up, often for decades, behind the dam. In some cases, regulators will allow¡ªeven prefer¡ªfor the sediment to wash downstream for stream habitat reasons. In other cases, the sediment might contain toxins that require it to be removed. Sometimes, sediment washing downstream might impact infrastructure.
Dealing with sediment is one of the big puzzles in dam removal. We want to consider what is the best sediment solution for aquatic fish and animals, water quality, impacts to downstream infrastructure, and the cost of removal.
In the case of Dana Dam, we were looking at removing 80 years of sediment behind the dam. There was up to 8 feet of accumulated sediment, so much that it reached just a foot below the water tumbling over the dam. We calculated that trucking it away would have been enormously expensive and out of our budget. Instead, our design repositioned the sediment to fill the old river channel near the railroad embankment.
Our creative sediment plan solved two problems. We moved the sediment away from the old dam, creating the new channel, and used it to seal off the old channel near the railroad embankment, thus directing water away from the railway. In all, the construction contractor repositioned about 500 dump truck loads of sediment.
How long did this take? From conceptual design through permitting and detailed design and then construction, about four years. And that included time lost during the COVID-19 pandemic. That timeline represents good progress in the dam removal business.
The author¡¯s parents visiting Dana Dam. They instilled a love of rivers in the author.
Reconnecting with Long Island Sound
With Dana Dam removed, we have reconnected approximately 12 miles of free-flowing river with Long Island Sound. Resident and migratory fish, including brook trout, river herring, sea lamprey, and American eel, can move freely upstream to historic spawning grounds.
Who values rivers? Lots of people, including my family. My love of rivers started on the banks of the Norwalk River and has taken me to rivers across North America. My photo album of the Norwalk River now includes a picture of my parents proudly viewing our construction site at Dana Dam. They taught me to love rivers, and now I¡¯m returning the favor to the rivers I know.