What was found in Yellowstone Np'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 | 2520 µg/L 63% of the EPA limit 4000 µg/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 2/2 | SYR4 |
| Copper | 58.85 µg/L 4.5% of the EPA limit 1300 µg/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2017
Highest in the city: 177.8 µg/L — YNP-MAMMOTH HOT SPRINGS · 2,600 people · 2018 | 2/2 | SYR4 |
| Nitrate-Nitrite | 30 µg/L 0.3% of the EPA limit 10000 µg/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019
Highest in the city: 170 µg/L — YNP-MAMMOTH HOT SPRINGS · 2,600 people · 2019 | 2/2 | SYR4 |
| Barium | 70 µg/L 3.5% of the EPA limit 2000 µg/L Highest in the city: YNP-MAMMOTH HOT SPRINGS · 2,600 people · 2019 | 1/2 | SYR4 |
| TTHM | 65.85 µg/L 82% of the EPA limit 80 µg/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 2/2 | SYR4 |
| Total Haloacetic Acids (HAA5) | 49.3 µg/L 82% of the EPA limit 60 µg/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 2/2 | SYR4 |
| Chloroform | 45.4 µg/L No EPA limit set Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 2/2 | SYR4 |
| Trichloroacetic Acid | 25.75 µg/L No EPA limit set Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 2/2 | SYR4 |
| Dichloroacetic Acid | 21 µg/L No EPA limit set Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 2/2 | SYR4 |
| Bromodichloromethane | 16.45 µg/L No EPA limit set Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 2/2 | SYR4 |
| Arsenic | 12.4 µg/L 124% of the EPA limit, at the 95th percentile of samples — 10 µg/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 1/2 | SYR4 |
| Lead | 8.25 µg/L 55% of the EPA limit 15 µg/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2017 | 2/2 | SYR4 |
| Dibromochloromethane | 7.07 µg/L No EPA limit set Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 1/2 | SYR4 |
| Gross Alpha, Excl. Radon And U | 3.425 pCi/L 23% of the EPA limit 15 pCi/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019
Highest in the city: 5.4 pCi/L — YNP-MAMMOTH HOT SPRINGS · 2,600 people · 2019 | 2/2 | SYR4 |
| Monochloroacetic Acid | 3.6 µg/L No EPA limit set Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 2/2 | SYR4 |
| Selenium | 2.85 µg/L 5.7% of the EPA limit 50 µg/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 1/2 | SYR4 |
| Thallium, Total | 2.29 µg/L 115% of the EPA limit, at the 95th percentile of samples — 2 µg/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 1/2 | SYR4 |
| Di(2-ethylhexyl) Phthalate | 2.1 µg/L 35% of the EPA limit 6 µg/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2017 | 1/2 | SYR4 |
| Antimony, Total | 1.9 µg/L 32% of the EPA limit 6 µg/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 1/2 | SYR4 |
| Combined Radium (-226 And -228) | 1.6 pCi/L 32% of the EPA limit 5 pCi/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 2/2 | SYR4 |
| Dibromoacetic Acid | 1.275 µg/L No EPA limit set Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 1/2 | SYR4 |
| Bromoform | 1.17 µg/L No EPA limit set Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 1/2 | SYR4 |
| Combined Uranium | 1 µg/L 3.3% of the EPA limit 30 µg/L Highest in the city: YNP-MAMMOTH HOT SPRINGS · 2,600 people · 2019 | 1/2 | SYR4 |
| Monobromoacetic Acid | 0.8000 µg/L No EPA limit set Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2019 | 1/2 | SYR4 |
| Lead | 0.0060 mg/L 40% of the EPA limit 0.0150 mg/L Main supplier: YNP-OLD FAITHFUL · 7,675 people · 2025 | 2/2 | 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 Yellowstone Np
| Supplier | Population served |
|---|---|
| YNP-OLD FAITHFUL | 7,675 |
| YNP-MAMMOTH HOT SPRINGS | 2,600 |
Frequently asked questions about Yellowstone Np tap water
Is Yellowstone Np tap water safe to drink?
EPA testing detected 25 contaminants in the water serving Yellowstone Np. 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 Yellowstone Np?
2 public water suppliers report drinking-water monitoring for Yellowstone Np, Wyoming to the EPA. Each is listed above with its population served.
What contaminants are in Yellowstone Np's water?
The contaminants EPA monitoring detected in Yellowstone Np include Fluoride, Copper, Nitrate-Nitrite, Barium, 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.