- PWSID
- MA2002000
- State
- Massachusetts
- System type
- community water system (CWS)
- Population served
- 21,285
- City
- Acton
- Counties
- Middlesex County
- Primary source water
- groundwater under the influence of surface water
- UCMR 5 sampling
- 2023-03-13 to 2024-03-22 · 3 entry point(s) · water types: GU;GW
- Service-area boundary
- authoritative
PFOA ≥ 3 × its limit highest single result
PFOA 1–3 × its limit worst entry-point average
Open on the Massachusetts map · All Massachusetts systems · All results
These are monitoring results collected under EPA's Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) at entry points, where treated water enters the distribution system; they are not tap-water samples. They are not compliance determinations: compliance with EPA's 2024 PFAS limits is judged on running annual averages of compliance monitoring, required from 2029, so a single UCMR 5 result at or above a limit is not a violation. “< MRL” means the compound was not quantified at EPA's minimum reporting level; it does not mean zero.
Compared with EPA's 2024 values
| Highest single result | Worst entry-point average* | Limit | |
|---|---|---|---|
| PFOA (ppt) | 13.4 | 11.55 | 4 |
| PFOS (ppt) | 4.9 | 4.55 | 4 |
| Hazard Index | 0.32 | 0.08 | 1.0† |
“<MRL” = every result for the compound was below its reporting limit. * Mean of all samples at each entry point with non-detects = 0 (EPA compliance convention; the Hazard Index also uses non-detects = 0); a screening comparison, not a formal running annual average. † Rescission proposed May 2026. PFOA/PFOS MCL 4 ppt (2024 NPDWR, in effect). PFHxS, PFNA, HFPO-DA (10 ppt each) and the Hazard Index (1.0) are 2024 NPDWR values; EPA proposed rescinding them on 18 May 2026 (comment period closed 20 Jul 2026).
Compared with Massachusetts standards
| Highest single result | Worst entry-point average* | Massachusetts | |
|---|---|---|---|
| PFAS6 (sum) (ppt) | 19.1 | 16.95 | 20 |
Sum standards add the listed compounds within each sample (non-detects = 0). State compliance is normally judged on averages over time; these are screening comparisons.
Sampling history
Sampled 2023-03-13 to 2024-03-22 · 3 entry point(s) · water types: GU;GW · 11 sampling visits. PFAS in ppt (ng/L).
| Date | Entry point | Event | PFOA | PFOS | HI | Other detections |
|---|---|---|---|---|---|---|
| 2023-03-13 | Central Acton WTP (GW) | SE1 | 5.1 | 4.9 | 0.002 | PFHxA 3 |
| 2023-03-15 | North Acton WTP (GU) | SE1 | 11.3 | <4 | 0.32 | PFBA 11.8, PFHpA 4.6, PFHxA 5.2, PFPeA 4.4 |
| 2023-03-15 | South Acton WTP (GU) | SE1 | 6.1 | 4.2 | 0.002 | PFHxA 5.5, PFPeA 6.4 |
| 2023-06-05 | South Acton WTP (GU) | SE2 | 7.1 | 4.6 | 0.002 | PFHxA 7.1, PFPeA 8.1 |
| 2023-06-28 | North Acton WTP (GU) | SE2 | 13.4 | <4 | 0 | PFBA 14.1, PFHpA 5.2, PFHxA 5.8, PFPeA 4.9 |
| 2023-09-18 | South Acton WTP (GU) | SE3 | 7.3 | 4.7 | 0.002 | PFHxA 6.3, PFPeA 8.1 |
| 2023-09-21 | North Acton WTP (GU) | SE3 | 11.9 | <4 | 0 | PFBA 20.6, PFHpA 4.8, PFHxA 5.4, PFPeA 4.6 |
| 2023-09-25 | Central Acton WTP (GW) | SE2 | 4.7 | 4.2 | 0 | none |
| 2023-12-06 | South Acton WTP (GU) | SE4 | 7.2 | 4.7 | 0.002 | PFHxA 6.6, PFPeA 8.4 |
| 2024-01-05 | North Acton WTP (GU) | SE4 | 9.6 | <4 | 0 | PFBA 18.3, PFHpA 3.8, PFHxA 4.7, PFPeA 4.9 |
| 2024-03-22 | North Acton WTP (GU) | SE3 | n/a | n/a | n/a | none |
“<4” = not detected at the reporting limit shown; “n/a” = not analyzed in that sample. Highlighted = at or above the 4 ppt MCL. HI computed per sample with non-detects as 0. Other detections lists every other quantified compound (lithium in µg/L).
All results by entry point
300 results. Each column is one sampling visit (date and UCMR 5 sample event). A number is a measured concentration; “< 4” = below the minimum reporting level shown; “–” = not analyzed in that visit. PFAS in ppt (ng/L); lithium in µg/L.
Central Acton WTP facility 00048 · sample point MULT16 · groundwater
| Compound | MRL | 2023-03-13 SE1 | 2023-09-25 SE2 |
|---|---|---|---|
| PFBS | 3 ppt | 3.5 | < 3 |
| PFHxA | 3 ppt | 3 | < 3 |
| PFOA | 4 ppt | 5.1 | 4.7 |
| PFOS | 4 ppt | 4.9 | 4.2 |
| 11Cl-PF3OUdS | 5 ppt | < 5 | < 5 |
| 4:2 FTS | 3 ppt | < 3 | < 3 |
| 6:2 FTS | 5 ppt | < 5 | < 5 |
| 8:2 FTS | 5 ppt | < 5 | < 5 |
| 9Cl-PF3ONS | 2 ppt | < 2 | < 2 |
| ADONA | 3 ppt | < 3 | < 3 |
| HFPO-DA | 5 ppt | < 5 | < 5 |
| NEtFOSAA | 5 ppt | < 5 | < 5 |
| NFDHA | 20 ppt | < 20 | < 20 |
| NMeFOSAA | 6 ppt | < 6 | < 6 |
| PFBA | 5 ppt | < 5 | < 5 |
| PFDA | 3 ppt | < 3 | < 3 |
| PFDoA | 3 ppt | < 3 | < 3 |
| PFEESA | 3 ppt | < 3 | < 3 |
| PFHpA | 3 ppt | < 3 | < 3 |
| PFHpS | 3 ppt | < 3 | < 3 |
| PFHxS | 3 ppt | < 3 | < 3 |
| PFMBA | 3 ppt | < 3 | < 3 |
| PFMPA | 4 ppt | < 4 | < 4 |
| PFNA | 4 ppt | < 4 | < 4 |
| PFPeA | 3 ppt | < 3 | < 3 |
| PFPeS | 4 ppt | < 4 | < 4 |
| PFTA | 8 ppt | < 8 | < 8 |
| PFTrDA | 7 ppt | < 7 | < 7 |
| PFUnA | 2 ppt | < 2 | < 2 |
| lithium | 9 µg/L | < 9 | < 9 |
North Acton WTP facility 00030 · sample point 19252 · groundwater under the influence of surface water
| Compound | MRL | 2023-03-15 SE1 | 2023-06-28 SE2 | 2023-09-21 SE3 | 2024-01-05 SE4 | 2024-03-22 SE3 |
|---|---|---|---|---|---|---|
| PFBA | 5 ppt | 11.8 | 14.1 | 20.6 | 18.3 | – |
| PFHpA | 3 ppt | 4.6 | 5.2 | 4.8 | 3.8 | – |
| PFHxA | 3 ppt | 5.2 | 5.8 | 5.4 | 4.7 | – |
| PFHxS | 3 ppt | 3.2 | < 3 | < 3 | < 3 | – |
| PFOA | 4 ppt | 11.3 | 13.4 | 11.9 | 9.6 | – |
| PFPeA | 3 ppt | 4.4 | 4.9 | 4.6 | 4.9 | – |
| 11Cl-PF3OUdS | 5 ppt | < 5 | < 5 | < 5 | < 5 | – |
| 4:2 FTS | 3 ppt | < 3 | < 3 | < 3 | < 3 | – |
| 6:2 FTS | 5 ppt | < 5 | < 5 | < 5 | < 5 | – |
| 8:2 FTS | 5 ppt | < 5 | < 5 | < 5 | < 5 | – |
| 9Cl-PF3ONS | 2 ppt | < 2 | < 2 | < 2 | < 2 | – |
| ADONA | 3 ppt | < 3 | < 3 | < 3 | < 3 | – |
| HFPO-DA | 5 ppt | < 5 | < 5 | < 5 | < 5 | – |
| NEtFOSAA | 5 ppt | < 5 | < 5 | – | < 5 | < 5 |
| NFDHA | 20 ppt | < 20 | < 20 | < 20 | < 20 | – |
| NMeFOSAA | 6 ppt | < 6 | < 6 | – | < 6 | < 6 |
| PFBS | 3 ppt | < 3 | < 3 | < 3 | < 3 | – |
| PFDA | 3 ppt | < 3 | < 3 | < 3 | < 3 | – |
| PFDoA | 3 ppt | < 3 | < 3 | < 3 | < 3 | – |
| PFEESA | 3 ppt | < 3 | < 3 | < 3 | < 3 | – |
| PFHpS | 3 ppt | < 3 | < 3 | < 3 | < 3 | – |
| PFMBA | 3 ppt | < 3 | < 3 | < 3 | < 3 | – |
| PFMPA | 4 ppt | < 4 | < 4 | < 4 | < 4 | – |
| PFNA | 4 ppt | < 4 | < 4 | < 4 | < 4 | – |
| PFOS | 4 ppt | < 4 | < 4 | < 4 | < 4 | – |
| PFPeS | 4 ppt | < 4 | < 4 | < 4 | < 4 | – |
| PFTA | 8 ppt | < 8 | < 8 | – | < 8 | < 8 |
| PFTrDA | 7 ppt | < 7 | < 7 | – | < 7 | < 7 |
| PFUnA | 2 ppt | < 2 | < 2 | < 2 | < 2 | – |
| lithium | 9 µg/L | < 9 | < 9 | < 9 | < 9 | – |
South Acton WTP facility 00032 · sample point MULT14 · groundwater under the influence of surface water
| Compound | MRL | 2023-03-15 SE1 | 2023-06-05 SE2 | 2023-09-18 SE3 | 2023-12-06 SE4 |
|---|---|---|---|---|---|
| PFBS | 3 ppt | 3.2 | 3.7 | 3.4 | 3.6 |
| PFHxA | 3 ppt | 5.5 | 7.1 | 6.3 | 6.6 |
| PFOA | 4 ppt | 6.1 | 7.1 | 7.3 | 7.2 |
| PFOS | 4 ppt | 4.2 | 4.6 | 4.7 | 4.7 |
| PFPeA | 3 ppt | 6.4 | 8.1 | 8.1 | 8.4 |
| 11Cl-PF3OUdS | 5 ppt | < 5 | < 5 | < 5 | < 5 |
| 4:2 FTS | 3 ppt | < 3 | < 3 | < 3 | < 3 |
| 6:2 FTS | 5 ppt | < 5 | < 5 | < 5 | < 5 |
| 8:2 FTS | 5 ppt | < 5 | < 5 | < 5 | < 5 |
| 9Cl-PF3ONS | 2 ppt | < 2 | < 2 | < 2 | < 2 |
| ADONA | 3 ppt | < 3 | < 3 | < 3 | < 3 |
| HFPO-DA | 5 ppt | < 5 | < 5 | < 5 | < 5 |
| NEtFOSAA | 5 ppt | < 5 | < 5 | < 5 | < 5 |
| NFDHA | 20 ppt | < 20 | < 20 | < 20 | < 20 |
| NMeFOSAA | 6 ppt | < 6 | < 6 | < 6 | < 6 |
| PFBA | 5 ppt | < 5 | < 5 | < 5 | < 5 |
| PFDA | 3 ppt | < 3 | < 3 | < 3 | < 3 |
| PFDoA | 3 ppt | < 3 | < 3 | < 3 | < 3 |
| PFEESA | 3 ppt | < 3 | < 3 | < 3 | < 3 |
| PFHpA | 3 ppt | < 3 | < 3 | < 3 | < 3 |
| PFHpS | 3 ppt | < 3 | < 3 | < 3 | < 3 |
| PFHxS | 3 ppt | < 3 | < 3 | < 3 | < 3 |
| PFMBA | 3 ppt | < 3 | < 3 | < 3 | < 3 |
| PFMPA | 4 ppt | < 4 | < 4 | < 4 | < 4 |
| PFNA | 4 ppt | < 4 | < 4 | < 4 | < 4 |
| PFPeS | 4 ppt | < 4 | < 4 | < 4 | < 4 |
| PFTA | 8 ppt | < 8 | < 8 | < 8 | < 8 |
| PFTrDA | 7 ppt | < 7 | < 7 | < 7 | < 7 |
| PFUnA | 2 ppt | < 2 | < 2 | < 2 | < 2 |
| lithium | 9 µg/L | < 9 | < 9 | < 9 | < 9 |
Statistics by compound
| Compound | Results | Detected | Highest (date) | Mean bounds | KM median | P75 | P90 | P95 |
|---|---|---|---|---|---|---|---|---|
| PFOA | 10 | 100% | 13.4 2023-06-28 | 8.37–8.37 | 7.2 | 11.3 | 11.9 | 13.4 |
| PFHxA | 10 | 90% | 7.1 2023-06-05 | 4.96–5.26 | 5.4 | 6.3 | 6.6 | 7.1 |
| PFPeA | 10 | 80% | 8.4 2023-12-06 | 4.98–5.58 | 4.9 | 8.1 | 8.1 | 8.4 |
| PFOS | 10 | 60% | 4.9 2023-03-13 | 2.73–4.33 | 4.2 | 4.7 | 4.7 | 4.9 |
| PFBS | 10 | 50% | 3.7 2023-06-05 | 1.74–3.24 | <MRL | 3.5 | 3.6 | 3.7 |
| PFBA | 10 | 40% | 20.6 2023-09-21 | 6.48–9.48 | <MRL | 14.1 | 18.3 | 20.6 |
| PFHpA | 10 | 40% | 5.2 2023-06-28 | 1.84–3.64 | <MRL | 4.6 | 4.8 | 5.2 |
| PFHxS | 10 | 10% | 3.2 2023-03-15 | 0.32–3.02 | <MRL | <MRL | <MRL | 3.2 |
Never detected (22): 11Cl-PF3OUdS, 4:2 FTS, 6:2 FTS, 8:2 FTS, 9Cl-PF3ONS, ADONA, HFPO-DA, NEtFOSAA, NFDHA, NMeFOSAA, PFDA, PFDoA, PFEESA, PFHpS, PFMBA, PFMPA, PFNA, PFPeS, PFTA, PFTrDA, PFUnA, lithium.
Left-censored Kaplan–Meier statistics (Helsel 2005; Helsel & Lee 2006, NADA for R). Units: ppt; lithium µg/L. Each compound has one reporting limit, so the Kaplan–Meier mean equals the upper mean bound (non-detects at the MRL); the lower bound sets non-detects to 0. “<MRL” = the percentile falls below the reporting limit and cannot be estimated. These describe this system's UCMR 5 samples, not population estimates.
Sources
- EPA UCMR 5 occurrence data text files (UCMR5_All.txt; samples 2023-01-09 to 2026-05-28; data summary dated Jul 2026)
- EPA SDWIS via ECHO SDWA downloads, quarter 2026Q3
- EPA Public Water System Service Areas v3 (Mar 2026)
- US Census Bureau cartographic boundary counties 1:500k, 2024
- EPA/USGS NHDPlus V2 (medium resolution) flowlines, Strahler order 2+
Data build a6eeb89a233e · 2026-10-18T04:09Z · UCMR 5 release Jul2026 · SDWIS 2026Q3. Data and methods.