Walk the loop around Horn Pond on any weekday evening and you will see the same cast of characters. Someone teaching a kid to ride a bike without training wheels near the boat launch on Lake Avenue. A retiree with a fishing rod working the shoreline for largemouth bass. Dogs on leashes, because that is the rule, dragging their owners past the community garden toward the benches where everyone seems to end up watching the sunset. It is the kind of place that does not announce itself. It just works, the way it has for the people who use it several times a week for years.
This fall, that loop gets noisier. Construction fencing, heavy equipment, and a parking lot that has been under some form of renovation since last year are converging on the south end of the pond near Scalley Dam. The reason has nothing to do with erosion or safety violations. It has to do with fish, and with a number that should have been a triumph and instead exposed a problem the city has been trying to fix for years.
The Number Nobody Expected
River herring returned to Horn Pond in 2018 for the first time in nearly a century, after the city built a rough bypass channel around Scalley Dam. About 25,000 fish made the swim that year. Three years later, the count hit a high of roughly 42,000. Then it fell apart. In the years that followed, counts dropped back below 20,000, a swing that had less to do with the fish and more to do with the channel they were swimming through.
By 2024, the run had recovered to at least 37,500 fish, according to state Division of Marine Fisheries estimates, a number that gave local monitors reason to think the population was stabilizing. Then came 2025, and the number that actually explains why there is a construction crew at your walking loop this fall.
| Year | Herring Counted at Horn Pond | Context |
|---|---|---|
| 2018 | ~25,000 | First return in nearly a century |
| 2021 | ~42,000 | Previous high water mark |
| 2024 | At least 37,500 | State-estimated recovery |
| 2025 | 6,900 | Regional Mystic River run hit a record 815,000 fish |
That last row is the whole story. In 2025, the broader Mystic River herring run through the fish ladders in Medford and Winchester set a record, an estimated 815,000 fish making the trip upstream from the ocean. At Horn Pond specifically, only 6,900 of them completed the final leg. The fish were there. The river was healthier than it had been in years. Horn Pond's own bypass simply could not move them through.
Why the Old Bypass Couldn't Keep Up
The 2018 fix was a riprap channel, essentially a rough stone ramp that lets fish climb around the dam when water conditions cooperate. It worked well enough to prove herring could return to Horn Pond at all. What it could not do was hold up to drought years, seasonal dry spells, or any flow inconsistent with the narrow band it was designed for. When conditions were right, herring surged through. When they weren't, the same fish that made it past two dams downstream in Medford and Winchester hit Scalley Dam and mostly turned back.
That is the part of the story that rarely makes it into the press release language about "habitat restoration." This was never really a fish population problem. The Mystic River watershed is producing more herring than it has in a documented history. Horn Pond's bottleneck was a piece of 2018 infrastructure that could not keep pace with 2025 success.
What's Actually Being Built at Scalley Dam
The fix is a pool-and-weir fish passage, a more permanent, more engineered structure than the old riprap ramp, built directly into Scalley Dam. It works by giving herring a series of stepped pools to move through gradually rather than one steep climb dependent on water level. The design also includes new educational signage and an ADA-accessible pathway leading to an underwater viewing window, so anyone walking the loop can actually watch the migration happen instead of reading about it on a sign afterward.
City Engineer Alex Rozycki has described the construction timeline directly:
"The fish ladder will be in construction all summer long and operational by the fall."
The funding took three separate sources and roughly three years to fully lock down. Back in 2023, the City Council committed $1 million toward the project, drawn from a larger $3.4 million settlement Woburn received after the EPA ordered companies responsible for pollution at the Industri-Plex Superfund site to pay restitution. That got the project moving but not fully funded. It took a North American Wetlands Conservation Act grant and a separate $1 million gift from an anonymous foundation to the Mystic River Watershed Association to close the gap, a milestone the city and the watershed association only confirmed this past March. If the fishway comes in on the timeline officials have described, it should be operational before the spring 2027 herring run begins, giving the fish access to more than 100 acres of spawning habitat in Horn Pond that the old channel could never reliably deliver them to.
The Parking Lot Work Comes First
Before any of that, the more immediate disruption for regular visitors has been the parking lot itself. The city began reconfiguring the lot in fall 2025 and picked the work back up in spring 2026, expanding the footprint to add roughly 30 more spaces, including additional handicap parking, plus new sidewalks and ADA-accessible ramps. Woburn Mayor Michael Concannon framed the upgrade as recognition of how much the pond already gets used, calling the walking paths and community garden a draw for "countless families" who treat Horn Pond as a fixture of daily life, not just a scenic stop.
Tucked into that same parking project is a rain garden, designed to filter stormwater runoff before it reaches the pond rather than letting it wash straight in from the lot. Curb cuts route water into a sediment basin, where it filters through biofiltration material before soaking into the ground, with a timber check dam to prevent standing water. It is not a glamorous addition, but it is the kind of detail that tells you the city expects a lot more foot and car traffic here once the underwater viewing window opens, and wants the water quality to hold up under it.
What This Means for Your Next Walk
A few practical notes if you are used to having Horn Pond to yourself on a weekday morning:
- The main construction activity is concentrated at the south end near Scalley Dam and the Lake Avenue boat launch lot. The Sturgis Street entrance near Ice House Park has historically been a quieter alternate access point for the loop.
- Expect the fishway work to run through the fall. Based on the timeline officials laid out earlier this year, the goal is to have it operational before construction season ends, well ahead of the spring 2027 herring migration.
- If you want to see the mechanics up close rather than wait for the finished viewing window, the Mystic River Watershed Association runs a volunteer herring counting program at Horn Pond each spring, and the Friends of Horn Pond group hosts its own calendar of talks and events throughout the year. The city's Conservation Commission has also organized a Horn Pond cleanup day each spring with MyRWA on site.
None of this changes what Horn Pond is for most people who live near it, a place to walk the dog, watch the water, and not think too hard about infrastructure. But the next time you notice the fencing near the dam, it is worth knowing what it actually represents: not a pond in decline, but a fix finally catching up to a fish population that outgrew its own bypass.
If you are watching Woburn from the outside and wondering what makes a neighborhood worth that kind of long-term public investment, projects like this one are part of the answer. A city does not spend three years chasing funding for a fish ladder unless enough residents already treat the place as worth protecting.
If you are curious what else is shifting in Woburn this season, from Main Street's newest additions to the market itself, Jodi Fitzgerald keeps a close eye on both. Reach out to schedule a free consultation whenever you are ready to talk about what is happening in this market, not just at the pond.
