We started this initiative expecting Plymouth's size to be the whole story — nearly 64,000 residents, more than a dozen wells, a system big enough that something usually shows up somewhere. Instead, the actual public data told us something more specific. Every regulated PFAS compound tested across Plymouth's municipal wells comes back well under both the Massachusetts 20 ppt combined standard and the federal 4 ppt individual limit for PFOA and PFOS — the highest reading anywhere in the system is 2.39 parts per trillion of PFOA at the Wannos Pond Well. Lead results are similarly clean, at roughly a quarter of the federal action level.
What makes Plymouth genuinely distinctive isn't a contamination finding — it's what 2026 reporting by the Plymouth Independent describes as an active, sourced local disagreement over whether the town's own growth could put that clean record at risk. Plymouth depends entirely on the Plymouth-Carver Sole Source Aquifer, with no backup water source if it were ever compromised at scale. The same reporting documents 488,000 cubic yards of sand and gravel mining approved at a single Route 3 site, ongoing tree clearing near the aquifer's recharge areas, and a real dispute between town officials balancing development against tax revenue and environmental advocates who argue the town's PFAS testing program — broad as it is, at 29 compounds — may not be enough to catch problems early given how fast Plymouth is growing. We think that's a more honest launch story than manufacturing a crisis the test results don't support: the water is clean right now, and the real question is what keeps it that way. See the full breakdown on our Water data page.
In 1990, the EPA designated the Plymouth-Carver Aquifer a "sole-source aquifer" — a formal label meaning the region has no reasonably available alternative drinking water source if this one were ever significantly contaminated. It was one of the first such designations in New England. The aquifer doesn't just serve Plymouth: Carver, Kingston, Wareham, Plympton, Middleborough, and Bourne all draw on the same regional groundwater resource, each through its own independent wells and distribution system.
We specifically checked whether Plymouth's water system has any actual shared pipes, wholesale purchase agreement, or interconnection with neighboring Kingston, Duxbury, or Carver — rather than assuming either total independence or a hidden connection. We found none. Sharing an aquifer is a geological fact, not an operational one: each town's wells, water bills, and compliance record are entirely its own. That's good news for insulation from a neighboring town's problem, but it also means protecting the aquifer's recharge areas — the land where rain actually replenishes the groundwater — is a genuinely regional challenge that no single town's water department controls by itself.
That's the backdrop for a real local debate: with no backup water source, activists have raised concerns about sand and gravel mining, tree clearing, and septic system density near the aquifer's recharge zones, while town officials describe balancing that protection against the jobs and tax base that come with continued development. Neither side disputes today's test results are clean — the disagreement is about what happens to that record over the next decade of growth.
Sources: Plymouth Independent, "The town's water supply is fragile. Is enough being done to protect it?"; Mass.gov, Plymouth-Carver Aquifer Advisory Committee; USGS, Hydrogeology and Simulation of Groundwater Flow in the Plymouth-Carver-Kingston-Duxbury Aquifer System.
Long before there was a federal PFAS rule, there was a Massachusetts one. In October 2020, MassDEP finalized an enforceable drinking water standard — a Maximum Contaminant Level, or MCL — of 20 parts per trillion for the combined total of six PFAS compounds, a grouping the state calls "PFAS6": PFOS, PFOA, PFHxS, PFNA, PFHpA, and PFDA.
At the time, this made Massachusetts one of a small number of states with any enforceable PFAS standard at all. For Plymouth, testing under this standard since it took effect has found only trace PFOA at two of its many wells — 2.39 ppt at Wannos Pond and 1.93 ppt at North Plymouth — with every other regulated compound coming back non-detect across the entire system, comfortably under the state's 20 ppt threshold.
Source: Mass.gov — Massachusetts PFAS Drinking Water Standard (MCL).
Until April 2024, there was no federal limit on PFAS in drinking water at all — only the Massachusetts state standard set in 2020. That changed when EPA finalized its National Primary Drinking Water Regulation (NPDWR) for PFAS: the first time PFAS compounds have been individually, enforceably regulated at the federal level.
The rule set limits of 4 parts per trillion (ppt) each for PFOA and PFOS, 10 ppt each for three additional compounds (PFHxS, PFNA, and HFPO-DA), and a combined "Hazard Index" limit for mixtures of those plus PFBS. Water systems nationwide were given until 2027 to complete initial monitoring and until 2029 to come into full compliance.
For Plymouth, the relevant numbers are the Wannos Pond Well's 2.39 ppt PFOA reading and the North Plymouth Well's 1.93 ppt — both comfortably under the new 4 ppt individual limit, and both the highest readings found anywhere in the system. It's a genuinely reassuring result, not a close call dressed up to sound reassuring.
Source: Federal Register — PFAS National Primary Drinking Water Regulation.
On May 18, 2026, EPA announced two proposals affecting the federal PFAS rule described above. The first would let water systems request a two-year extension — from 2029 to 2031 — to comply with the enforceable limits for PFOA and PFOS. The second would rescind the individual limits for three other PFAS compounds (PFHxS, PFNA, and HFPO-DA/GenX) and the combined Hazard Index limit for mixtures of those plus PFBS.
What doesn't change: the 4 ppt limits for PFOA and PFOS individually aren't part of either rescission proposal. For a system like Plymouth's, whose highest PFOA readings to date are already well under that 4 ppt threshold, this rulemaking mostly affects compliance paperwork timelines rather than anything that would change what's actually coming out of Plymouth taps.
EPA held a virtual public hearing on July 7, 2026, and the combined comment dockets closed yesterday, July 20, 2026, with more than 15,000 comments submitted. As of today, neither proposal has been finalized; EPA has said it intends to act before the end of 2026. Treat the 2024 rule as the current legal baseline until EPA actually finalizes a change, and check back here as that process plays out.
See the full regulatory timeline for how this fits with the 2020 state standard and the 2024 federal rule.
System-wide data only tells part of the story — which well serves your street, your home's plumbing, and fixtures can all change what actually comes out of your tap.
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