Independent community water quality initiative

Protecting Cohasset's drinking water, one household at a time

We track MassDEP and EPA testing data for the Cohasset Water Department's own system — Lily Pond, the Aaron River Reservoir, and the Ellms Meadow well-field — and help Cohasset families understand what's really coming out of the tap, in plain language, sourced from public records.

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7,550
residents served by the Cohasset Water Department (about 90% of town)
25.8 ppt
highest PFAS6 reading recorded in town system data since 2018 — above MA's 20 ppt limit
12.08 ppt
2023 quarterly average PFAS6 level — currently within the state standard

What's really in your tap water?

Cohasset's own water system — separate from the Weir River system that serves the North Cohasset section of town — draws from two surface supplies, Lily Pond and the Aaron River Reservoir, plus the Ellms Meadow groundwater well-field. It's operated by the town's elected Board of Water Commissioners, not a private utility.

The town's 2023 Consumer Confidence Report shows the system currently testing within Massachusetts' PFAS6 standard: a quarterly average of 12.08 parts per trillion (ppt), against the state's 20 ppt limit. But a separate compilation of MassDEP data going back to 2018 shows this same system's PFAS6 level peaked at 25.8 ppt at some point in that window — above the state limit. We think both facts are worth knowing.

MeasureLevelMA PFAS6 standard
Historical peak (since 2018, per third-party MassDEP data compilation)25.8 ppt20 ppt
2023 quarterly average (town CCR)12.08 ppt20 ppt
2023 range detected (town CCR)5.5 – 16.1 ppt20 ppt

Sources: Cohasset Water Department 2023 Consumer Confidence Report; Sierra Club Massachusetts PFAS tracker (MassDEP data, since 2018). See the full breakdown on the Water data page.

Aaron River Reservoir in Cohasset, Massachusetts, one of the surface water sources feeding the Cohasset Water Department's system
South Main Street in downtown Cohasset, Massachusetts

Built by Cohasset neighbors, for Cohasset neighbors

Cohasset Water Watch is a volunteer-run initiative started by residents who wanted a plain-language, independent source for what MassDEP and EPA testing actually shows about the town's own water supply — separate from the Water Department's own reporting.

We read the Consumer Confidence Reports so you don't have to, track new PFAS and EPA monitoring data as it's published, and help neighbors figure out whether their household should be doing anything differently.

Read our story

Concerned about your household's water?

Request a free in-home water test and a volunteer will follow up to walk through what your results mean.

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