North Cohasset — the part of the Town of Cohasset closest to Hingham — doesn't draw from a separate Cohasset water system for this service area. Along with Hingham and Hull, it's supplied by the Weir River Water System, operated by Aquarion Water Company from sources in Hingham — Accord Brook, Accord Pond, and eleven groundwater wells across the Weir Watershed. Whatever shows up in EPA testing of the Weir River system's source water and treatment process is what actually reaches North Cohasset taps, regardless of town lines.
Hingham Water Watch was started to track that data in plain language. We're a Hingham-based volunteer effort, but since the water supply is shared, so is the relevant data.
EPA's Fifth Unregulated Contaminant Monitoring Rule (UCMR5) found five PFAS compounds in the Weir River system's testing results:
| Compound | Detected level | EPA individual limit | Status |
|---|---|---|---|
| PFOA | 5.7 ppt | 4 ppt | Above EPA health-based limit |
| PFBA | 5.7 ppt | No individual MCL | Monitored, not yet regulated |
| PFBS | 3.3 ppt | No individual MCL | Monitored, not yet regulated |
| PFPeA | 3.1 ppt | No individual MCL | Monitored, not yet regulated |
| PFHxA | 3.1 ppt | No individual MCL | Monitored, not yet regulated |
ppt = parts per trillion. None of this represents an EPA violation — the system has recorded no health-based MCL violations since 2010. Source: EPA UCMR5 occurrence data. Full methodology and violation history on the Water data page.
System-wide data only tells part of the story — service lines, home plumbing, and private wells can all change what actually comes out of your tap.
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