What was found in Thornton's water
The level at the city's main supplier, the highest level anywhere in the city, the EPA limit for each, and where every figure comes from.
| Contaminant | Level vs EPA limit | Suppliers | Source |
|---|---|---|---|
| Nitrate | 930.5 µg/L 9.3% of the EPA limit 10000 µg/L Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Fluoride | 902.5 µg/L 23% of the EPA limit 4000 µg/L Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Nitrate-Nitrite | 870 µg/L 8.7% of the EPA limit 10000 µg/L Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Nitrite | 591 µg/L 59% of the EPA limit 1000 µg/L Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| TTHM | 56.55 µg/L 71% of the EPA limit 80 µg/L Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Barium | 49.525 µg/L 2.5% of the EPA limit 2000 µg/L Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Lithium | 34 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2023 | 1/8 | UCMR-5 |
| Total Haloacetic Acids (HAA5) | 28.97 µg/L 48% of the EPA limit 60 µg/L Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Chloroform | 25 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Bromodichloromethane | 20.33 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Dibromochloromethane | 15.55 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Dichloroacetic Acid | 12 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Trichloroacetic Acid | 8.235 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Bromoform | 7.215 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Combined Uranium | 6.047 µg/L 20% of the EPA limit 30 µg/L Main supplier: THORNTON CITY OF · 226,465 people · 2018 | 1/8 | SYR4 |
| Gross Beta Particle Activity | 5.856 pCi/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2017 | 1/8 | SYR4 |
| Dibromoacetic Acid | 5.075 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Gross Alpha, Excl. Radon And U | 2.64 pCi/L 18% of the EPA limit 15 pCi/L Main supplier: THORNTON CITY OF · 226,465 people · 2018 | 1/8 | SYR4 |
| Chromium | 1.66 µg/L 1.7% of the EPA limit 100 µg/L Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Bromate | 1.44 µg/L 14% of the EPA limit 10 µg/L Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Monobromoacetic Acid | 1.0975 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Arsenic | 0.8990 µg/L 9% of the EPA limit 10 µg/L Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Combined Radium (-226 And -228) | 0.8105 pCi/L 16% of the EPA limit 5 pCi/L Main supplier: THORNTON CITY OF · 226,465 people · 2018 | 1/8 | SYR4 |
| Antimony, Total | 0.2655 µg/L 4.4% of the EPA limit 6 µg/L Main supplier: THORNTON CITY OF · 226,465 people · 2019 | 1/8 | SYR4 |
| Pfhxa | 0.0126 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2023 | 1/8 | UCMR-5 |
| Pfpea | 0.0124 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2023 | 1/8 | UCMR-5 |
| Pfba | 0.0104 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2023 | 1/8 | UCMR-5 |
| PFBS | 0.0081 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2023 | 1/8 | UCMR-5 |
| PFOA | 0.0071 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2023 | 1/8 | UCMR-5 |
| PFHXS | 0.0059 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2023 | 1/8 | UCMR-5 |
| PFOS | 0.0050 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2023 | 1/8 | UCMR-5 |
| Pfhpa | 0.0037 µg/L No EPA limit set Main supplier: THORNTON CITY OF · 226,465 people · 2023 | 1/8 | UCMR-5 |
| Lead | 0.0023 mg/L 15% of the EPA limit 0.0150 mg/L Main supplier: THORNTON CITY OF · 226,465 people · 2025
Highest in the city: 0.0030 mg/L — WOODLAND HILLS MHC · 1,740 people · 2025 | 8/8 | LCR |
Each bar shows the measured level as a share of the EPA limit: green is
well under, amber is close to it, red is over. For lead and copper the
limit applies to exactly the 90th-percentile figure shown, so red there
means a real exceedance. For everything else the limit applies to a
running annual average while the figure is the 95th percentile of the
system's samples — over 100% is worth reading, but is not by itself a
violation.
Formal violations are listed separately.
These are the utilities' own EPA-reported results, not a city-wide
average. A detection means the lab measured the
substance — it isn't the same as exceeding a legal limit. Hover a source
tag to see the EPA program and years behind each figure.
Water suppliers serving Thornton
| Supplier | Population served |
|---|---|
| THORNTON CITY OF | 226,465 |
| WOODLAND HILLS MHC | 1,740 |
| REDWOOD ESTATES | 1,500 |
| THE GROVE AT ALTA RIDGE | 1,300 |
| FRIENDLY VILLAGE OF THE ROCKIES | 1,046 |
| AVILLA EASTLAKE | 410 |
| CHAPARRAL VILLAGE MHP | 303 |
| THORNTON ESTATES | 300 |
Frequently asked questions about Thornton tap water
Is Thornton tap water safe to drink?
EPA testing detected 33 contaminants in the water serving Thornton. A detection isn't the same as a violation — most detected levels are within federal limits. Check the level and source for each contaminant above, and your utility's annual Consumer Confidence Report for the official compliance status.
How many water suppliers serve Thornton?
8 public water suppliers report drinking-water monitoring for Thornton, Colorado to the EPA. Each is listed above with its population served.
What contaminants are in Thornton's water?
The contaminants EPA monitoring detected in Thornton include Nitrate, Fluoride, Nitrate-Nitrite, Nitrite, TTHM. The full list, with the level at the main supplier and the data source, is in the table above.
Where does this data come from?
Every figure is official EPA drinking-water monitoring — the Lead & Copper Rule, the UCMR-5 nationwide testing program, and the EPA Six-Year Review — not our own testing. Each number is labelled with its source and period.