To the editor:
In Summer 2025, Lynn and Swampscott installed and operated a UV Disinfection System on the municipal border about 200 feet inland from King’s Beach. The system was aimed to be a short-term pilot program. It was loud and disrupted the neighborhood. It became clogged with seaweed early on and had to be reengineered to continue operating. And depending on your taste for mechanical objects, it probably couldn’t be considered pretty.
But the UV System was worth every penny and was a resounding success for two reasons.
First, it worked. Every drop of water coming out of the system was disinfected of the bacteria that has plagued Stacey’s Brook since it was culverted and turned into a combined sewer and later separated into just a stormwater system for Lynn and Swampscott. This was not surprising, and in fact was fully expected because that’s what UV does. The fact that it only functioned during dry weather was also expected. Most beaches in the region and in other urban areas see some bacterial impact from rainstorms, and the first priority of the UV system was to keep King’s Beach clean during the dry days.
Second, the system provided crucial new information on Stacey’s Brook that we simply did not have before. Though the UV system disinfected the water, tests showed that bacterial counts sometimes spiked again 200 feet later as the brook emptied onto the swimming beach. For the last nine years, Swampscott and Lynn have been searching for source of the bacterial loads throughout the system, patching up cracked pipes, and removing illicit connections from sewers. Now we have a new lead to what many hope will be a key source of bacteria that can be identified and addressed.
For 2026, in consultation with Lynn, Swampscott, Save the Harbor, Save King’s Beach, Lynn Water and Sewer Commission, and several engineers, the King’s Beach Steering Committee has created a plan to take the next steps toward a safe and swimmable King’s Beach with a four-part scope.
- Sediment testing will help determine whether the sediment deposits in the Lynn and Swampscott culverts may be contributing to the bacteria concentrations of the discharged drainage flows to King’s Beach.
- Independent culvert testing in both the Lynn and Swampscott outfalls five days a week from April to September will replicate the 2017 study that led to the current IDDE strategies and tell us if and how the last nine years of work have impacted Stacey’s Brook.
- Flow level monitoring will help evaluate bacterial loading from each municipality based on volume, rather than the simple snapshot of a traditional bacterial sample. Additionally, this data may help refine sizing assumptions for a future UV system.
- Wet weather testing will help specify specific and detailed windows during which the UV system would or would not be effective due to turbidity and flow. Should a complementary solution be agreed to in the future, this data will help improve the efficiency of the system.
Our hope is that, as in 2025, a targeted, methodical approach will lead us to actionable information that can further the cause of cleaning up King’s Beach. Potential outcomes are identifying the origin of bacteria in the sediment that could then be cleaned or dredged out; understanding the past nine years of IDDE and how pipe repair work have improved bacterial levels overall, which could inform future work and help predict a remaining timeline.
We want to highlight that IDDE will continue as a permanent staple of our operations; currently, Swampscott is nearing completion of its pipe-sleeving project while the Lynn Water and Sewer Commission is finishing their current round of comprehensive system inspections. The 2017 study indicated that IDDE alone would not be sufficient to fully eliminate bacterial contamination on the beach, which is why we have layered this work with a complementary system. UV treatment is currently our leading contender. The lessons learned during last summer’s pilot, along with our upcoming phase of research, will allow us to confirm or update the 2017 conclusion and advance with the proper evaluation, planning and implementation needed for a path forward.
There are so many variables at work in a complex system like Stacey’s Brook and King’s Beach, but one thing that we can all celebrate is the overall improvement in water quality at King’s Beach in 2025. Whether due to the UV system, the dry summer weather, the improvements to the pipes over the last several years, or a combination of these factors, King’s Beach achieved something not seen in recent history. The beach received a 90% water quality rating, meaning bacteria levels at all three testing sites were within safe swimming limits simultaneously 90% of the time. This is a significant jump over the six-year average of 69% and 2023’s record low of 55%.
If we keep working together toward this common cause, we can all look forward to sunny, swimmable days on this beautiful stretch of coast.
Sincerely,
Chris Mancini
Chris Mancini is the executive director of Save the Harbor/Save the Bay. He is a member of the King’s Beach Steering Committee and a Swampscott Resident.
