What was found in Great Falls'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 | 270 µg/L 2.7% of the EPA limit 10000 µg/L Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019
Highest in the city: 3843.5 µg/L — PLEASANT PARK COMMUNITY INC · 125 people · 2019 | 10/27 | SYR4 |
| Fluoride | 900 µg/L 23% of the EPA limit 4000 µg/L Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019
Highest in the city: 3065 µg/L — GORE HILL COUNTY WATER DIST · 500 people · 2018 | 10/27 | SYR4 |
| Copper | 1176 µg/L 90% of the EPA limit 1300 µg/L Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019
Highest in the city: 1482.5 µg/L — MALMSTROM AIR FORCE BASE · 8,850 people · 2018 | 13/27 | SYR4 |
| TTHM | 67 µg/L 84% of the EPA limit 80 µg/L Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019
Highest in the city: 81 µg/L — MALMSTROM AIR FORCE BASE · 8,850 people · 2019 | 8/27 | SYR4 |
| Lithium | 80.8 µg/L No EPA limit set Main supplier: GREAT FALLS CITY OF · 60,000 people · 2023 | 2/27 | UCMR-5 |
| Chloroform | 53 µg/L No EPA limit set Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019
Highest in the city: 71.5 µg/L — MALMSTROM AIR FORCE BASE · 8,850 people · 2019 | 4/27 | SYR4 |
| Total Haloacetic Acids (HAA5) | 69.8 µg/L 116% of the EPA limit, at the 95th percentile of samples — 60 µg/L Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019 | 7/27 | SYR4 |
| Barium | 50 µg/L 2.5% of the EPA limit 2000 µg/L Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019 | 2/27 | SYR4 |
| Trichloroacetic Acid | 40 µg/L No EPA limit set Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019 | 4/27 | SYR4 |
| Dichloroacetic Acid | 30.6 µg/L No EPA limit set Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019 | 4/27 | SYR4 |
| Arsenic | 4 µg/L 40% of the EPA limit 10 µg/L Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019
Highest in the city: 29.4 µg/L — SOUTH WIND WATER AND SEWER DISTRICT · 200 people · 2018 | 7/27 | SYR4 |
| Gross Alpha, Excl. Radon And U | 3.2 pCi/L 21% of the EPA limit 15 pCi/L Main supplier: GREAT FALLS CITY OF · 60,000 people · 2014
Highest in the city: 23.5 pCi/L — SPRING TREE RIDGE · 80 people · 2018 | 7/27 | SYR4 |
| Selenium | 19.8 µg/L 40% of the EPA limit 50 µg/L Highest in the city: PARK GARDEN ESTATES · 50 people · 2019 | 7/27 | SYR4 |
| Combined Uranium | 1 µg/L 3.3% of the EPA limit 30 µg/L Main supplier: GREAT FALLS CITY OF · 60,000 people · 2014
Highest in the city: 18.8 µg/L — PARK GARDEN ESTATES · 50 people · 2019 | 8/27 | SYR4 |
| Bromodichloromethane | 14 µg/L No EPA limit set Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019
Highest in the city: 14.8 µg/L — HIGHWOOD MOBILE HOME PARK · 400 people · 2014 | 5/27 | SYR4 |
| Lead | 8 µg/L 53% of the EPA limit 15 µg/L Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019
Highest in the city: 14.4 µg/L — PARK GARDEN ESTATES · 50 people · 2018 | 11/27 | SYR4 |
| Dibromochloromethane | 2.8 µg/L No EPA limit set Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019
Highest in the city: 13.5 µg/L — SUN PRAIRIE WATER DISTRICT · 350 people · 2019 | 5/27 | SYR4 |
| Bromoform | 12.75 µg/L No EPA limit set Highest in the city: SUN PRAIRIE WATER DISTRICT · 350 people · 2019 | 6/27 | SYR4 |
| Gross Beta Particle Activity | 11 pCi/L No EPA limit set Highest in the city: PLEASANT PARK COMMUNITY INC · 125 people · 2019 | 1/27 | SYR4 |
| Chromium | 8.8 µg/L 8.8% of the EPA limit 100 µg/L Highest in the city: PARK GARDEN ESTATES · 50 people · 2019 | 1/27 | SYR4 |
| Dibromoacetic Acid | 0.6500 µg/L No EPA limit set Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019
Highest in the city: 6.84 µg/L — SUN PRAIRIE WATER DISTRICT · 350 people · 2019 | 7/27 | SYR4 |
| Combined Radium (-226 And -228) | 4.8 pCi/L 96% of the EPA limit 5 pCi/L Highest in the city: SPRING TREE RIDGE · 80 people · 2013 | 7/27 | SYR4 |
| Monochloroacetic Acid | 2.735 µg/L No EPA limit set Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019 | 2/27 | SYR4 |
| Monobromoacetic Acid | 1.475 µg/L No EPA limit set Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019 | 3/27 | SYR4 |
| Hexachlorocyclopentadiene | 0.1195 µg/L 0.2% of the EPA limit 50 µg/L Main supplier: GREAT FALLS CITY OF · 60,000 people · 2019 | 1/27 | SYR4 |
| Lead | 0.0120 mg/L 80% of the EPA limit 0.0150 mg/L Main supplier: GREAT FALLS CITY OF · 60,000 people · 2026 | 19/27 | LCR |
| Pfba | 0.0070 µg/L No EPA limit set Highest in the city: MALMSTROM AIR FORCE BASE · 8,850 people · 2023 | 1/27 | UCMR-5 |
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 Great Falls
Frequently asked questions about Great Falls tap water
Is Great Falls tap water safe to drink?
EPA testing detected 27 contaminants in the water serving Great Falls. 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 Great Falls?
27 public water suppliers report drinking-water monitoring for Great Falls, Montana to the EPA. Each is listed above with its population served.
What contaminants are in Great Falls's water?
The contaminants EPA monitoring detected in Great Falls include Nitrate-Nitrite, Fluoride, Copper, TTHM, Lithium. 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.