The New London Day 9/19/2026
The Nature Conservancy wants you to start thinking about culverts.
The tubes and tunnels that channel water under roads and rail lines are everywhere — and as the climate changes, their ability to function is more critical than ever, for both the people who cross over them and the aquatic life that swim through them.
But despite their crucial role, most culverts remain unmapped and unassessed, leaving major questions about their age, condition and performance.
The Nature Conservancy is working to change that.
The nonprofit set out to assess around 300 culverts and tidal stream crossings in Southeastern Connecticut this summer to compile the state’s first comprehensive inventory within the Long Island Sound Coastal Watershed.
Thanks to a $384,000 grant from the National Fish and Wildlife Foundation and help from state and local partners, The Nature Conservancy now has data on more than 600 culverts — information that will be shared with cities and towns so that local governments can prioritize funding for repair and replacement projects.
Systems in action
On a sunny Wednesday morning, Matt Manjos of The Nature Conservancy waded into waist-high waters near a culvert on Brook Street in Noank.
Manjos gauged the width and depth of the culvert with a large measuring stick and compared it to the high and low-tide marks as Julia Laich, a fellow stream barrier assessment crew member, recorded the measurements on a tablet.
Manjos and Laich assessed about 10 crossings a day this summer, traveling Southeastern Connecticut’s shoreline from East Lyme to Stonington, and following rivers and streams as far north as Voluntown.
Along the way, the team found several culverts near complete collapse, allowing just inches of water to flow through spaces that should have been at least two feet wide.
Some were clogged with debris that blocked both water and wildlife from effectively passing through. Several more crossings had dirt deposits on the roadway — indicating that water frequently overtopped the culvert. Others were built either so low that the culvert was always submerged, or so high above the waterline that fish could not access the culvert at all.
The Brook Street crossing, a large concrete box culvert that seamlessly connected a freshwater creek to the salt marsh at Palmer Cove, was one of the better crossings they had come across.
As Manjos continued to take measurements, hundreds of juvenile alewives and silversides glittered under just below the surface of the brackish water as the schools passed in and out of the culvert.
“Anadromous fish species are becoming more and more rare, which are fish that swim out of the ocean into the rivers to spawn,” Manjos said. “(Here) it’s like a nursery habitat for the baby fish essentially.”
“The salt marsh is one of the most endangered habitats in Connecticut and all of New England,” Manjos said. “Crossings like this allow fish like alewives and silversides — which are very important for the health of the sound and the rivers themselves — (to) properly use the river, and it helps impact bird habitats and all the other living organisms that require clean and connected rivers to survive.”
Laich explained that when an assessment team encounters a culvert, each crossing is evaluated for three concerns: the structural integrity of the structure, how effectively the stream can pass through and how well they accommodate the passage of aquatic species.
“My favorite part has been seeing successful aquatic organisms enjoying the spaces that they’re supposed to have access to. It gives me the motivation to keep going out and assessing these culverts to make sure that eventually all of them are like that,” Laich said.
“A lot of people that we talk to while doing these culvert assessments have told us that their basements flood, their yard floods. So that’s also a big motivation for us to get out there and try to help as many people as we can,” Laich added.
Gaps in data, performance
Emily Hadzopulos, a senior freshwater restoration project manager for The Nature Conservancy, said that if a culvert is insufficient for fish, it is likely an insufficient passage for water, especially during flood conditions.
“The two problems really go hand in hand,” Hadzopulos said. “When you have culverts that are inadequate for fish passage, they’re also usually really vulnerable to things like sea level rise, and they’re vulnerable to storm surges and flooding and failure.”
Hadzopulos said Connecticut is home to an estimated 26,000 culverts — but data only exists for a small fraction.
As of 2024, the Connecticut of Department of Transportation has mapped more than 6,400 of the estimated 13,000 culverts on state roads. Of those mapped, just 40% have undergone an inspection.
Hadzopulos said state policy is starting to catch up with the gaps. Starting in May of 2028, culvert mapping will become an annual requirement for cities and towns.
Under a state law passed in 2025, municipalities will need to submit data on each local culvert and bridge — including the structure’s location, age and dimensions — in a geospatial file that will ultimately be shared with the Connecticut Office of Policy and Management.
While the law states that the regional council of governments must report any municipality that does not submit a data file by the annual May 1 deadline, it does not list any penalties for noncompliance.
Hadzopulos said The Nature Conservancy’s upcoming inventory will assign a condition score to each culvert, offering cities and towns a head start at identifying the crossings in most need of upgrades.
According to the Department of Transportation’s 2024 culvert drainage fact sheet, more than 13% of culverts inspected on state roads are in poor condition.
The department found that most of the culverts were made of reinforced concrete or corrugated metal pipes and that 85% of the structures were built between the 1920s and 1960s. Less than 1% were constructed within the last 20 years.
Hadzopulos said these older crossings tend to be undersized and were constructed with little consideration for overall river health and extreme weather performance.
“The culverts that were built were not meant to keep up with the kind of rainstorms … and the deluges that we’re seeing today,” Hadzopulos said.
Prioritizing upgrades
Culvert performance during recent record-setting rainfall events has shown that infrastructure improvements can have a major impact on safety and repair costs.
In August of 2024, when severe flooding ripped through the western part of the state, the Connecticut Institute for Resilience and Climate Adaptation said the town of Southbury recorded $91 million in municipal damage to culverts and roads.
However, the institute wrote in a report that “the catastrophic storm had no effect on the other upgraded culverts and bridges throughout town that had recently replaced outdated culverts.”
The institute estimated that the town dodged more than $18 million in storm damage by upgrading this infrastructure before the storm hit.
Beyond the structural benefits, Hadzopulos said larger, upgraded culverts provide critical safe passages, from the smallest fish, turtles and frogs to the largest bears, bobcats and deer.
“Better culverts allow for more free-flowing wildlife through the system, but it also allows us to drive more freely and safely because you’re reducing the chances of those wildlife vehicle collisions,” Hadzopulos said.
Looking back on the summer, Hadzopulos said she is proud of the culvert data The Nature Conservancy collected in collaboration with Save the Sound, the Connecticut National Estuarine Research Reserve, the Connecticut Department of Energy and Environmental Protection, the Southeastern Connecticut Council of Governments, and the University of Connecticut Center for Land Use, Education and Research.
“We’re going to be able to give all the towns, especially in Southeastern Connecticut, information so that they can better prioritize those crossings that are in most need,” Hadzopulos said. “We’re going to be continuing these assessments into next year, and probably focus in on a different part of the state.”
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