What was found in Stonington'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 | 442.3 µg/L 4.4% of the EPA limit 10000 µg/L Main supplier: AQUARION-MYSTIC · 10,788 people · 2019
Highest in the city: 1640 µg/L — AQUARION-ARLINGTON ACRES · 392 people · 2019 | 2/3 | SYR4 |
| Nitrate-Nitrite | 412.1 µg/L 4.1% of the EPA limit 10000 µg/L Main supplier: AQUARION-MYSTIC · 10,788 people · 2019
Highest in the city: 1598 µg/L — AQUARION-ARLINGTON ACRES · 392 people · 2019 | 2/3 | SYR4 |
| Copper | 262.5 µg/L 20% of the EPA limit 1300 µg/L Main supplier: AQUARION-MYSTIC · 10,788 people · 2019
Highest in the city: 946.5 µg/L — AQUARION-ARLINGTON ACRES · 392 people · 2019 | 3/3 | SYR4 |
| Fluoride | 912 µg/L 23% of the EPA limit 4000 µg/L Main supplier: AQUARION-MYSTIC · 10,788 people · 2019 | 2/3 | SYR4 |
| TTHM | 82 µg/L 102% of the EPA limit, at the 95th percentile of samples — 80 µg/L Main supplier: AQUARION-MYSTIC · 10,788 people · 2019
Highest in the city: 87.1 µg/L — CTWC - SHORELINE REGION-MASONS ISLAND · 445 people · 2019 | 2/3 | SYR4 |
| Chloroform | 67 µg/L No EPA limit set Main supplier: AQUARION-MYSTIC · 10,788 people · 2019 | 3/3 | SYR4 |
| Total Haloacetic Acids (HAA5) | 67 µg/L 112% of the EPA limit, at the 95th percentile of samples — 60 µg/L Main supplier: AQUARION-MYSTIC · 10,788 people · 2019 | 2/3 | SYR4 |
| Trichloroacetic Acid | 36 µg/L No EPA limit set Main supplier: AQUARION-MYSTIC · 10,788 people · 2019
Highest in the city: 42 µg/L — CTWC - SHORELINE REGION-MASONS ISLAND · 445 people · 2019 | 2/3 | SYR4 |
| Barium | 31 µg/L 1.6% of the EPA limit 2000 µg/L Main supplier: AQUARION-MYSTIC · 10,788 people · 2019
Highest in the city: 32.8 µg/L — AQUARION-ARLINGTON ACRES · 392 people · 2019 | 2/3 | SYR4 |
| Dichloroacetic Acid | 27 µg/L No EPA limit set Main supplier: AQUARION-MYSTIC · 10,788 people · 2019 | 2/3 | SYR4 |
| Bromodichloromethane | 17 µg/L No EPA limit set Main supplier: AQUARION-MYSTIC · 10,788 people · 2019 | 2/3 | SYR4 |
| Lead | 4 µg/L 27% of the EPA limit 15 µg/L Main supplier: AQUARION-MYSTIC · 10,788 people · 2019
Highest in the city: 16.375 µg/L — CTWC - SHORELINE REGION-MASONS ISLAND · 445 people · 2019 | 3/3 | SYR4 |
| Monochloroacetic Acid | 3 µg/L No EPA limit set Main supplier: AQUARION-MYSTIC · 10,788 people · 2019
Highest in the city: 6.085 µg/L — CTWC - SHORELINE REGION-MASONS ISLAND · 445 people · 2019 | 2/3 | SYR4 |
| Dibromochloromethane | 4 µg/L No EPA limit set Main supplier: AQUARION-MYSTIC · 10,788 people · 2019 | 2/3 | SYR4 |
| Combined Radium (-226 And -228) | 2.5 pCi/L 50% of the EPA limit 5 pCi/L Highest in the city: AQUARION-ARLINGTON ACRES · 392 people · 2019 | 1/3 | SYR4 |
| Combined Uranium | 1.717 µg/L 5.7% of the EPA limit 30 µg/L Highest in the city: AQUARION-ARLINGTON ACRES · 392 people · 2019 | 1/3 | SYR4 |
| Dibromoacetic Acid | 1 µg/L No EPA limit set Main supplier: AQUARION-MYSTIC · 10,788 people · 2019
Highest in the city: 1.2 µg/L — CTWC - SHORELINE REGION-MASONS ISLAND · 445 people · 2019 | 2/3 | SYR4 |
| Cadmium | 1 µg/L 20% of the EPA limit 5 µg/L Main supplier: AQUARION-MYSTIC · 10,788 people · 2019 | 1/3 | SYR4 |
| Monobromoacetic Acid | 1 µg/L No EPA limit set Main supplier: AQUARION-MYSTIC · 10,788 people · 2019 | 1/3 | SYR4 |
| PFBS | 0.0040 µg/L No EPA limit set Main supplier: AQUARION-MYSTIC · 10,788 people · 2025 | 1/3 | UCMR-5 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: AQUARION-MYSTIC · 10,788 people · 2026
Highest in the city: 0.0019 mg/L — AQUARION-ARLINGTON ACRES · 392 people · 2025 | 3/3 | 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 Stonington
| Supplier | Population served |
|---|---|
| AQUARION-MYSTIC | 10,788 |
| CTWC - SHORELINE REGION-MASONS ISLAND | 445 |
| AQUARION-ARLINGTON ACRES | 392 |
Frequently asked questions about Stonington tap water
Is Stonington tap water safe to drink?
EPA testing detected 21 contaminants in the water serving Stonington. 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 Stonington?
3 public water suppliers report drinking-water monitoring for Stonington, Connecticut to the EPA. Each is listed above with its population served.
What contaminants are in Stonington's water?
The contaminants EPA monitoring detected in Stonington include Nitrate, Nitrate-Nitrite, Copper, Fluoride, 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.