Recent heavy rainfall has resulted in more than 20 million gallons of combined sewer overflow at oceanside locations in both Swampscott and Lynn.

The sewage overflow, caused by stormwater flooding the city’s combined water and sewer pipe system, pumped millions of gallons of raw or partially treated sewage into the ocean shores. CSO location 5 near the Lynnway led the way with nearly 20 million gallons alone, while the adjacent CSO location 4 saw approximately 1.7 million gallons. Near the Swampscott-Lynn town line, King’s Beach saw more than 57,000 gallons of sewage. Swampscott resident Andrea Amour started “Save King’s Beach” in 2021 to raise more awareness about the issue.

“I really think the state needs to think way more critically about our sewer infrastructure as a critical piece,” Amour said. “We focus on things like bridges and roads and the MBTA, and our underground infrastructure continually gets neglected.”

She explained that while King’s Beach has seen a decrease in sewer overflow output due to the sewer separation project, there is still much work to be done with the combined sewer system.

“As you can see from the numbers themselves, the sewer separation project had a significant impact on avoiding CSO ejections into King’s Beach,” Amour explained.

She emphasized that she feels while both municipalities have the same effect, their causes differ. She said she believes Swampscott’s main issue is old and broken pipes, while Lynn has unauthorized sewer line connections that should not be there.

The state has provided Lynn with “very low interest” grants to improve the sewer and stormwater infrastructure, but Amour worries that the cost could still ultimately cause financial issues for the city.

“It’s going to pile up to the tune of a quarter of a billion dollars over the next two to three decades to fix these CSOs,” Amour said. “So I think that to foot the city of Lynn with that kind of bill, even though it’s a low-interest loan, is incredibly challenging.”

Amour hopes this most recent CSO incident moment inspires both municipalities to focus more on the situation, as she feels they have sought “parallel” solutions instead of overhauling the entire infrastructure.

“If we just fix this at its source and actually invest in our sewer infrastructure itself, we won’t need to worry about any of these parallel solutions,” Amour said.

Swampscott Town Administrator Sean Fitzgerald has proposed the idea of an outfall extension, which would funnel sewer water out to the middle of the ocean in the hopes that it will be dilute enough to not affect the beaches.