In 2023, Connecticut removed Strong Pond Dam after 20 years of planning. 3 years later, 10 upstream miles are open to fish, reconnecting 20 miles of habitat for wildlife

For more than two decades, plans were taking shape to remove Strong Pond Dam from Connecticut's Norwalk River. That work finally became reality in September 2023, when the dam, also known as Dana Dam or Merwin Meadows Dam, was removed in Wilton. The project restored natural stream flows, improved aquatic habitat and opened 10 upstream miles of the Norwalk River to fish and other aquatic organisms, as per a report by the U.S. EPA Connecticut Department of Energy and Environmental Protection.

Together, the restored area now contributes to 20 miles of connected riverine habitat stretching from Long Island Sound.

Why was Strong Pond Dam removed?

The Norwalk River runs for about 20 miles from its headwaters in Ridgefield to Long Island Sound in Norwalk. The watershed also includes Wilton, where Strong Pond Dam stood for decades.

Unlike many dams that were built to support mills or generate power, Strong Pond Dam was constructed in the 1940s to create a pond for ice skating and swimming for the original landowner's family.

Over time, however, the dam became an important barrier in the river.

The Norwalk River Watershed Action Plan identified Strong Pond Dam as a significant impoundment in 1998. An update in 2011 again highlighted the way the dam altered the river's natural conditions.

The impoundment disrupted the movement of sediment and nutrients. Materials that would normally travel downstream instead accumulated behind the dam, contributing to legacy pollutants and reducing channel depth.

The slower water created by the impoundment also affected dissolved oxygen and water temperatures. Warmer, slower-moving water increased nutrient attenuation within the impoundment and encouraged algal growth and eutrophication.

The channel behind the dam was also wider than the river's natural channel. That reduced riparian habitat and limited the stream features favored by fish.

Strong Pond Dam was particularly significant because it was the first barrier on the Norwalk River for diadromous fish. These include alewife, blue-back herring, sea lamprey, American eel and American shad.

Removing that barrier therefore offered an opportunity to reconnect river habitat that had been separated.

How long did the restoration take?

The idea of removing Strong Pond Dam was not new.

Planning and coordination continued for more than 20 years. The 1998 and 2011 watershed action plans had already identified the dam's environmental effects, but design, permitting and construction did not begin until funding became available in 2020.

Save the Sound received funding through different stages of the project.

The Long Island Sound Study supported the initial design phase from 2020 through 2022. A Clean Water Act Section 319 grant supported Construction Phase 1 between 2020 and 2021.

The Long Island Sound Study then funded Construction Phase 2, which covered most of the construction work, including the removal of Strong Pond Dam in September 2023.

Post-construction work followed from 2023 to 2024. Bipartisan Infrastructure Law funding through the Long Island Sound Study supported activities including riparian stabilization.

The Connecticut Department of Energy and Environmental Protection committed $3.09 million to pre-project planning and coordination, engineering design, permitting, implementation planning, construction and riparian stabilization.

Additional support came from the U.S. Fish and Wildlife Service, private donations and foundations.

Save the Sound worked with the Town of Wilton, Trout Unlimited's Mianus Chapter and subcontractors. Coordination was also required with the Connecticut Department of Transportation because of the project's proximity to rail lines, as well as with the U.S. Army Corps of Engineers for permitting.

What changed after the dam came out?

The physical changes to the river were significant.

The project restored approximately 1,400 feet of natural stream flows and reconstructed about 800 feet of pool-riffle channel. It also created approximately one acre of new riparian buffer habitat.

The restoration helped bring the river closer to natural conditions while improving habitat along its banks.

Water quality improvements were also observed downstream. These included lower stream temperatures and increased dissolved oxygen conditions associated with the restored riparian buffer habitat and the dam removal.

Perhaps one of the most important results was the reconnection of aquatic habitat.

The removal made 10 upstream miles of the Norwalk River accessible to fish and other aquatic organisms. That created 20 miles of connected riverine habitat extending from Long Island Sound.

For diadromous fish, which move between freshwater and saltwater environments, reconnecting these stretches of river was an important benefit of removing the barrier.

The project also eliminated hazards and risks associated with the old dam.

Strong Pond Dam did not provide flood control or flood protection. Converting the former impoundment into a buffered river channel instead allows the area to attenuate energy, stabilize banks during floods and improve climate resiliency.

Did the project improve water quality?

The dam removal added to improvements in the Norwalk River watershed, although it is important to distinguish those improvements from the earlier bacteria delisting.

The Norwalk River segment where Strong Pond Dam was located had previously been impaired for recreation because of bacteria. It was listed in 2004 for pathogens, specifically E. coli, and was delisted in 2022.

That delisting happened independently of the Strong Pond Dam removal.

The river's bacteria problems had been associated with sources including failed or poorly maintained septic systems, urban stormwater, illicit discharges to storm sewers, and bacteria carried by runoff from farms, wildlife and pets.

Local stakeholders had already carried out substantial work to improve those conditions. The segment was removed from the impaired list based on indicator bacteria data collected through a Clean Water Act Section 319 project.

The dam removal therefore represents another layer of restoration rather than the reason for the 2022 bacteria delisting.

Its contribution has instead focused on hydromodification, natural stream flows, aquatic habitat connectivity, fish passage and conditions such as temperature and dissolved oxygen.

What happens to the river next?

The Norwalk River is expected to continue moving toward a natural equilibrium over time.

Monitoring will continue through the Connecticut Department of Energy and Environmental Protection and local stakeholders. Future monitoring will include water quality parameters as well as studies of diadromous fish populations.

The restoration also aligns with goals identified by the Long Island Sound Study's 2015 Comprehensive Conservation and Management Plan, including riparian buffer improvements, habitat connectivity and river restoration.

With the dam gone, the former barrier no longer separates the upstream portion of the river from habitat downstream.

After more than 20 years of planning, the removal of Strong Pond Dam has restored 1,400 feet of natural stream flows, added riparian habitat and opened 10 upstream miles of the Norwalk River to aquatic organisms.

The result is a connected stretch of approximately 20 miles of riverine habitat from Long Island Sound, while the river continues to be monitored as its restored channel adjusts over time.

FAQs

When was Strong Pond Dam removed?
September 2023.

How much habitat was reconnected?
About 20 miles.