What was found in Williston'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 |
|---|---|---|---|
| Fluoride | 810 µg/L 20% of the EPA limit 4000 µg/L Main supplier: WILLISTON CITY OF · 26,426 people · 2016 | 1/5 | SYR4 |
| Nitrate-Nitrite | 300 µg/L 3% of the EPA limit 10000 µg/L Main supplier: WILLISTON CITY OF · 26,426 people · 2019 | 1/5 | SYR4 |
| Copper | 49.92 µg/L 3.8% of the EPA limit 1300 µg/L Main supplier: WILLISTON CITY OF · 26,426 people · 2017
Highest in the city: 245 µg/L — INSPIRE COMMUNITIES-SPRINGBROOK · 300 people · 2019 | 4/5 | SYR4 |
| Lithium | 79 µg/L No EPA limit set Main supplier: WILLISTON CITY OF · 26,426 people · 2023 | 2/5 | UCMR-5 |
| Lead | 3.037 µg/L 20% of the EPA limit 15 µg/L Main supplier: WILLISTON CITY OF · 26,426 people · 2017
Highest in the city: 69.6 µg/L — INSPIRE COMMUNITIES-SPRINGBROOK · 300 people · 2019 | 3/5 | SYR4 |
| TTHM | 36.2665 µg/L 45% of the EPA limit 80 µg/L Main supplier: WILLISTON CITY OF · 26,426 people · 2019
Highest in the city: 40.72 µg/L — INSPIRE COMMUNITIES-SPRINGBROOK · 300 people · 2019 | 4/5 | SYR4 |
| Chloroform | 27.1275 µg/L No EPA limit set Main supplier: WILLISTON CITY OF · 26,426 people · 2019
Highest in the city: 30.535 µg/L — INSPIRE COMMUNITIES-SPRINGBROOK · 300 people · 2019 | 4/5 | SYR4 |
| Total Haloacetic Acids (HAA5) | 17.274 µg/L 29% of the EPA limit 60 µg/L Main supplier: WILLISTON CITY OF · 26,426 people · 2019
Highest in the city: 17.668 µg/L — NORTHWEST RURAL WATER DISTRICT · 5,102 people · 2019 | 4/5 | SYR4 |
| Dichloroacetic Acid | 14.32 µg/L No EPA limit set Main supplier: WILLISTON CITY OF · 26,426 people · 2019
Highest in the city: 14.42 µg/L — NORTHWEST RURAL WATER DISTRICT · 5,102 people · 2019 | 4/5 | SYR4 |
| Barium | 14.3 µg/L 0.7% of the EPA limit 2000 µg/L Main supplier: WILLISTON CITY OF · 26,426 people · 2016 | 1/5 | SYR4 |
| Bromodichloromethane | 8.007 µg/L No EPA limit set Main supplier: WILLISTON CITY OF · 26,426 people · 2019
Highest in the city: 8.443 µg/L — INSPIRE COMMUNITIES-SPRINGBROOK · 300 people · 2019 | 4/5 | SYR4 |
| Monochloroacetic Acid | 2.444 µg/L No EPA limit set Main supplier: WILLISTON CITY OF · 26,426 people · 2019
Highest in the city: 3.944 µg/L — NORTHWEST RURAL WATER DISTRICT · 5,102 people · 2019 | 2/5 | SYR4 |
| Gross Alpha, Excl. Radon And U | 3.9 pCi/L 26% of the EPA limit 15 pCi/L Main supplier: WILLISTON CITY OF · 26,426 people · 2017 | 1/5 | SYR4 |
| Trichloroacetic Acid | 3.853 µg/L No EPA limit set Main supplier: WILLISTON CITY OF · 26,426 people · 2019 | 4/5 | SYR4 |
| Dibromochloromethane | 2.4855 µg/L No EPA limit set Main supplier: WILLISTON CITY OF · 26,426 people · 2019 | 4/5 | SYR4 |
| Selenium | 1.44 µg/L 2.9% of the EPA limit 50 µg/L Main supplier: WILLISTON CITY OF · 26,426 people · 2016 | 1/5 | SYR4 |
| Chromium | 1.17 µg/L 1.2% of the EPA limit 100 µg/L Main supplier: WILLISTON CITY OF · 26,426 people · 2016 | 1/5 | SYR4 |
| Dibromoacetic Acid | 1.1325 µg/L No EPA limit set Main supplier: WILLISTON CITY OF · 26,426 people · 2019 | 3/5 | SYR4 |
| Combined Radium (-226 And -228) | 0.7800 pCi/L 16% of the EPA limit 5 pCi/L Main supplier: WILLISTON CITY OF · 26,426 people · 2017 | 1/5 | SYR4 |
| Bromoform | 0.2800 µg/L No EPA limit set Highest in the city: PRAIRIE VIEW HOA · 226 people · 2019 | 1/5 | SYR4 |
| Pentachlorophenol | 0.0300 µg/L 3% of the EPA limit 1 µg/L Main supplier: WILLISTON CITY OF · 26,426 people · 2017 | 1/5 | SYR4 |
| Pfba | 0.0063 µg/L No EPA limit set Highest in the city: NORTHWEST RURAL WATER DISTRICT · 5,102 people · 2023 | 1/5 | UCMR-5 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: WILLISTON CITY OF · 26,426 people · 2023 | 4/5 | LCR |
| Combined Uranium | -0.44 µg/L -1.5% of the EPA limit 30 µg/L Main supplier: WILLISTON CITY OF · 26,426 people · 2017 | 1/5 | SYR4 |
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 Williston
| Supplier | Population served |
|---|---|
| WILLISTON CITY OF | 26,426 |
| NORTHWEST RURAL WATER DISTRICT | 5,102 |
| INSPIRE COMMUNITIES-SPRINGBROOK | 300 |
| PRAIRIE VIEW HOA | 226 |
| WESTERN AREA WATER SUPPLY AUTHORITY | 0 |
Frequently asked questions about Williston tap water
Is Williston tap water safe to drink?
EPA testing detected 24 contaminants in the water serving Williston. 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 Williston?
5 public water suppliers report drinking-water monitoring for Williston, North Dakota to the EPA. Each is listed above with its population served.
What contaminants are in Williston's water?
The contaminants EPA monitoring detected in Williston include Fluoride, Nitrate-Nitrite, Copper, Lithium, Lead. 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.