What was found in Harlem'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-Nitrite | 30 µg/L 0.3% of the EPA limit 10000 µg/L Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019
Highest in the city: 1260 µg/L — MNIHNAPA WATER SYSTEM · 220 people · 2019 | 6/6 | SYR4 |
| Fluoride | 200 µg/L 5% of the EPA limit 4000 µg/L Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2018
Highest in the city: 850 µg/L — NORTH HARLEM COLONY · 42 people · 2012 | 5/6 | SYR4 |
| Copper | 53.6 µg/L 4.1% of the EPA limit 1300 µg/L Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019
Highest in the city: 837.7 µg/L — NORTH HARLEM COLONY · 42 people · 2019 | 6/6 | SYR4 |
| TTHM | 167.9 µg/L 210% of the EPA limit, at the 95th percentile of samples — 80 µg/L Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019 | 4/6 | SYR4 |
| Lead | 1 µg/L 6.7% of the EPA limit 15 µg/L Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019
Highest in the city: 142 µg/L — HARLEM CITY OF · 820 people · 2018 | 6/6 | SYR4 |
| Chloroform | 134 µg/L No EPA limit set Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019 | 4/6 | SYR4 |
| Barium | 79 µg/L 4% of the EPA limit 2000 µg/L Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2018
Highest in the city: 109.5 µg/L — HAYS/WHITE COW CANYON WS · 840 people · 2018 | 3/6 | SYR4 |
| Total Haloacetic Acids (HAA5) | 76.8 µg/L 128% of the EPA limit, at the 95th percentile of samples — 60 µg/L Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019
Highest in the city: 91.45 µg/L — HARLEM CITY OF · 820 people · 2019 | 4/6 | SYR4 |
| Trichloroacetic Acid | 57 µg/L No EPA limit set Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019 | 3/6 | SYR4 |
| Dichloroacetic Acid | 39 µg/L No EPA limit set Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019
Highest in the city: 45.65 µg/L — HARLEM CITY OF · 820 people · 2019 | 4/6 | SYR4 |
| Bromodichloromethane | 42 µg/L No EPA limit set Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019 | 4/6 | SYR4 |
| Dibromochloromethane | 28.6 µg/L No EPA limit set Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019 | 4/6 | SYR4 |
| Monochloroacetic Acid | 11.42 µg/L No EPA limit set Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019 | 2/6 | SYR4 |
| Chromium | 6 µg/L 6% of the EPA limit 100 µg/L Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2018
Highest in the city: 10 µg/L — OLD HAYS · 80 people · 2018 | 4/6 | SYR4 |
| Gross Alpha, Excl. Radon And U | 8.3 pCi/L 55% of the EPA limit 15 pCi/L Highest in the city: NORTH HARLEM COLONY · 42 people · 2019 | 1/6 | SYR4 |
| Dibromoacetic Acid | 7.58 µg/L No EPA limit set Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019 | 4/6 | SYR4 |
| Selenium | 1 µg/L 2% of the EPA limit 50 µg/L Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2018
Highest in the city: 6.95 µg/L — OLD HAYS · 80 people · 2018 | 4/6 | SYR4 |
| Combined Uranium | 1.3 µg/L 4.3% of the EPA limit 30 µg/L Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019
Highest in the city: 6 µg/L — OLD HAYS · 80 people · 2016 | 5/6 | SYR4 |
| Bromoform | 5.6 µg/L No EPA limit set Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019 | 3/6 | SYR4 |
| Arsenic | 2 µg/L 20% of the EPA limit 10 µg/L Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2018
Highest in the city: 2.8 µg/L — HARLEM CITY OF · 820 people · 2019 | 4/6 | SYR4 |
| Combined Radium (-226 And -228) | 1 pCi/L 20% of the EPA limit 5 pCi/L Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019
Highest in the city: 1.865 pCi/L — HARLEM CITY OF · 820 people · 2018 | 4/6 | SYR4 |
| Monobromoacetic Acid | 1.42 µg/L No EPA limit set Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2019 | 2/6 | SYR4 |
| Chlorobenzene | 0.6200 µg/L 0.6% of the EPA limit 100 µg/L Highest in the city: NORTH HARLEM COLONY · 42 people · 2019 | 1/6 | SYR4 |
| Hexachlorocyclopentadiene | 0.1580 µg/L 0.3% of the EPA limit 50 µg/L Highest in the city: HARLEM CITY OF · 820 people · 2018 | 1/6 | SYR4 |
| Lead | 0.0010 mg/L 6.7% of the EPA limit 0.0150 mg/L Main supplier: FORT BELKNAP AGENCY WATER SYSTEM · 2,600 people · 2025
Highest in the city: 0.0020 mg/L — HAYS/WHITE COW CANYON WS · 840 people · 2023 | 6/6 | 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 Harlem
| Supplier | Population served |
|---|---|
| FORT BELKNAP AGENCY WATER SYSTEM | 2,600 |
| HAYS/WHITE COW CANYON WS | 840 |
| HARLEM CITY OF | 820 |
| MNIHNAPA WATER SYSTEM | 220 |
| OLD HAYS | 80 |
| NORTH HARLEM COLONY | 42 |
Frequently asked questions about Harlem tap water
Is Harlem tap water safe to drink?
EPA testing detected 25 contaminants in the water serving Harlem. 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 Harlem?
6 public water suppliers report drinking-water monitoring for Harlem, Montana to the EPA. Each is listed above with its population served.
What contaminants are in Harlem's water?
The contaminants EPA monitoring detected in Harlem include Nitrate-Nitrite, Fluoride, Copper, TTHM, 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.