- PWSID
- CO0101150
- State
- Colorado
- System type
- community water system (CWS)
- Population served
- 226,465
- City
- Thornton
- Counties
- Adams County
- Primary source water
- surface water
- UCMR 5 sampling
- 2023-02-14 to 2023-11-27 · 2 entry point(s) · water types: SW
- Service-area boundary
- authoritative
PFOA 1–3 × its limit highest single result
PFOA below its limit worst entry-point average
Open on the Colorado map · All Colorado 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) | 7.1 | 3.4 | 4 |
| PFOS (ppt) | 5 | 2.38 | 4 |
| Hazard Index | 0.594 | 0.255 | 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 Colorado standards
| Highest single result | Worst entry-point average* | Colorado | |
|---|---|---|---|
| PFOA (ppt) | 7.1 | 3.4 | 4 |
| PFOS (ppt) | 5 | 2.38 | 4 |
| PFNA (ppt) | 0 | 0 | 10 |
| PFHxS (ppt) | 5.9 | 2.52 | 10 |
| HFPO-DA (GenX) (ppt) | 0 | 0 | 10 |
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 2023-02-14 to 2023-11-27 · 2 entry point(s) · water types: SW · 8 sampling visits. PFAS in ppt (ng/L).
| Date | Entry point | Event | PFOA | PFOS | HI | Other detections |
|---|---|---|---|---|---|---|
| 2023-02-14 | Thornton Treatment Plant (SW) | SE1 | 7.1 | 5 | 0.594 | PFBA 10.4, PFHpA 3.7, PFHxA 12.6, PFPeA 12.4, lithium 34 µg/L |
| 2023-05-30 | Thornton Treatment Plant (SW) | SE2 | 6.5 | 4.5 | 0.423 | PFBA 8.3, PFHpA 3.2, PFHxA 10.4, PFPeA 10, lithium 26.8 µg/L |
| 2023-05-30 | Wes Brown TP (SW) | SE2 | <4 | <4 | 0.002 | PFBA 8.7, PFHxA 4.8, PFPeA 8.2, lithium 30.5 µg/L |
| 2023-06-14 | Thornton Treatment Plant (SW) | SE1 | n/a | n/a | n/a | none |
| 2023-06-14 | Wes Brown TP (SW) | SE1 | <4 | <4 | 0.002 | PFBA 9.6, PFHxA 7.5, PFPeA 8.8, lithium 28.7 µg/L |
| 2023-08-14 | Thornton Treatment Plant (SW) | SE3 | <4 | <4 | 0.002 | PFHxA 4.1, PFPeA 4.1, lithium 21.9 µg/L |
| 2023-08-14 | Wes Brown TP (SW) | SE3 | <4 | <4 | 0.002 | PFBA 8.1, PFHxA 5.8, PFPeA 7.5, lithium 25.5 µg/L |
| 2023-11-27 | Thornton Treatment Plant (SW) | SE4 | <4 | <4 | 0.002 | PFBA 6, PFHxA 5.6, PFPeA 5.5, lithium 21.3 µg/L |
“<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
210 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.
Thornton Treatment Plant facility 022 · sample point 022 · surface water
| Compound | MRL | 2023-02-14 SE1 | 2023-05-30 SE2 | 2023-06-14 SE1 | 2023-08-14 SE3 | 2023-11-27 SE4 |
|---|---|---|---|---|---|---|
| PFBA | 5 ppt | 10.4 | 8.3 | – | < 5 | 6 |
| PFBS | 3 ppt | 8.1 | 7.1 | – | 3.1 | 4.2 |
| PFHpA | 3 ppt | 3.7 | 3.2 | – | < 3 | < 3 |
| PFHxA | 3 ppt | 12.6 | 10.4 | – | 4.1 | 5.6 |
| PFHxS | 3 ppt | 5.9 | 4.2 | – | < 3 | < 3 |
| PFOA | 4 ppt | 7.1 | 6.5 | – | < 4 | < 4 |
| PFOS | 4 ppt | 5 | 4.5 | – | < 4 | < 4 |
| PFPeA | 3 ppt | 12.4 | 10 | – | 4.1 | 5.5 |
| 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 |
| 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 |
| 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 | 34 | 26.8 | – | 21.9 | 21.3 |
Wes Brown TP facility 00001 · sample point 00001 · surface water
| Compound | MRL | 2023-05-30 SE2 | 2023-06-14 SE1 | 2023-08-14 SE3 |
|---|---|---|---|---|
| PFBA | 5 ppt | 8.7 | 9.6 | 8.1 |
| PFBS | 3 ppt | 3.2 | 4.8 | 3.6 |
| PFHxA | 3 ppt | 4.8 | 7.5 | 5.8 |
| PFPeA | 3 ppt | 8.2 | 8.8 | 7.5 |
| 11Cl-PF3OUdS | 5 ppt | < 5 | < 5 | < 5 |
| 4:2 FTS | 3 ppt | < 3 | < 3 | < 3 |
| 6:2 FTS | 5 ppt | < 5 | < 5 | < 5 |
| 8:2 FTS | 5 ppt | < 5 | < 5 | < 5 |
| 9Cl-PF3ONS | 2 ppt | < 2 | < 2 | < 2 |
| ADONA | 3 ppt | < 3 | < 3 | < 3 |
| HFPO-DA | 5 ppt | < 5 | < 5 | < 5 |
| NEtFOSAA | 5 ppt | < 5 | < 5 | < 5 |
| NFDHA | 20 ppt | < 20 | < 20 | < 20 |
| NMeFOSAA | 6 ppt | < 6 | < 6 | < 6 |
| PFDA | 3 ppt | < 3 | < 3 | < 3 |
| PFDoA | 3 ppt | < 3 | < 3 | < 3 |
| PFEESA | 3 ppt | < 3 | < 3 | < 3 |
| PFHpA | 3 ppt | < 3 | < 3 | < 3 |
| PFHpS | 3 ppt | < 3 | < 3 | < 3 |
| PFHxS | 3 ppt | < 3 | < 3 | < 3 |
| PFMBA | 3 ppt | < 3 | < 3 | < 3 |
| PFMPA | 4 ppt | < 4 | < 4 | < 4 |
| PFNA | 4 ppt | < 4 | < 4 | < 4 |
| PFOA | 4 ppt | < 4 | < 4 | < 4 |
| PFOS | 4 ppt | < 4 | < 4 | < 4 |
| PFPeS | 4 ppt | < 4 | < 4 | < 4 |
| PFTA | 8 ppt | < 8 | < 8 | < 8 |
| PFTrDA | 7 ppt | < 7 | < 7 | < 7 |
| PFUnA | 2 ppt | < 2 | < 2 | < 2 |
| lithium | 9 µg/L | 30.5 | 28.7 | 25.5 |
Statistics by compound
| Compound | Results | Detected | Highest (date) | Mean bounds | KM median | P75 | P90 | P95 |
|---|---|---|---|---|---|---|---|---|
| PFBS | 7 | 100% | 8.1 2023-02-14 | 4.87–4.87 | 4.2 | 7.1 | 8.1 | 8.1 |
| PFHxA | 7 | 100% | 12.6 2023-02-14 | 7.26–7.26 | 5.8 | 10.4 | 12.6 | 12.6 |
| PFPeA | 7 | 100% | 12.4 2023-02-14 | 8.07–8.07 | 8.2 | 10 | 12.4 | 12.4 |
| lithium | 7 | 100% | 34 2023-02-14 | 26.96–26.96 | 26.8 | 30.5 | 34 | 34 |
| PFBA | 7 | 86% | 10.4 2023-02-14 | 7.3–8.01 | 8.3 | 9.6 | 10.4 | 10.4 |
| PFHpA | 7 | 29% | 3.7 2023-02-14 | 0.99–3.13 | <MRL | 3.2 | 3.7 | 3.7 |
| PFHxS | 7 | 29% | 5.9 2023-02-14 | 1.44–3.59 | <MRL | 4.2 | 5.9 | 5.9 |
| PFOA | 7 | 29% | 7.1 2023-02-14 | 1.94–4.8 | <MRL | 6.5 | 7.1 | 7.1 |
| PFOS | 7 | 29% | 5 2023-02-14 | 1.36–4.21 | <MRL | 4.5 | 5 | 5 |
Never detected (21): 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.
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 2023-01-03 to 2026-05-07; 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 e835c17dd18b · 2026-10-18T04:06Z · UCMR 5 release Jul2026 · SDWIS 2026Q3. Data and methods.