What was found in Onalaska'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 | 8450 µg/L 85% of the EPA limit 10000 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2017 | 1/1 | SYR4 |
| Nitrate | 6400 µg/L 64% of the EPA limit 10000 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Copper | 1373 µg/L 106% of the EPA limit, at the 95th percentile of samples — 1300 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2017 | 1/1 | SYR4 |
| Fluoride | 840.2 µg/L 21% of the EPA limit 4000 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Total Haloacetic Acids (HAA5) | 112.921 µg/L 188% of the EPA limit, at the 95th percentile of samples — 60 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Monochloroacetic Acid | 109.775 µg/L No EPA limit set Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Barium | 97.68 µg/L 4.9% of the EPA limit 2000 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2017 | 1/1 | SYR4 |
| TTHM | 11.3852 µg/L 14% of the EPA limit 80 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Bromodichloromethane | 3.99 µg/L No EPA limit set Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Chloroform | 3.7495 µg/L No EPA limit set Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Lead | 3.5015 µg/L 23% of the EPA limit 15 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2017 | 1/1 | SYR4 |
| Dibromochloromethane | 3.251 µg/L No EPA limit set Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Combined Radium (-226 And -228) | 3.092 pCi/L 62% of the EPA limit 5 pCi/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2017 | 1/1 | SYR4 |
| Dichloroacetic Acid | 2.974 µg/L No EPA limit set Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Gross Alpha, Excl. Radon And U | 2.71 pCi/L 18% of the EPA limit 15 pCi/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2014 | 1/1 | SYR4 |
| Trichloroacetic Acid | 1.5855 µg/L No EPA limit set Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Bromoform | 1.155 µg/L No EPA limit set Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Dibromoacetic Acid | 1.042 µg/L No EPA limit set Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Arsenic | 1 µg/L 10% of the EPA limit 10 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2017 | 1/1 | SYR4 |
| Tetrachloroethylene | 0.6831 µg/L 14% of the EPA limit 5 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Selenium | 0.6000 µg/L 1.2% of the EPA limit 50 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2017 | 1/1 | SYR4 |
| Combined Uranium | 0.5000 µg/L 1.7% of the EPA limit 30 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2017 | 1/1 | SYR4 |
| Thallium, Total | 0.5000 µg/L 25% of the EPA limit 2 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2017 | 1/1 | SYR4 |
| Monobromoacetic Acid | 0.4990 µg/L No EPA limit set Main supplier: ONALASKA WATERWORKS · 18,000 people · 2019 | 1/1 | SYR4 |
| Mercury | 0.4000 µg/L 20% of the EPA limit 2 µg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2017 | 1/1 | SYR4 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: ONALASKA WATERWORKS · 18,000 people · 2023 | 1/1 | 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 Onalaska
| Supplier | Population served |
|---|---|
| ONALASKA WATERWORKS | 18,000 |
Frequently asked questions about Onalaska tap water
Is Onalaska tap water safe to drink?
EPA testing detected 26 contaminants in the water serving Onalaska. 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 Onalaska?
1 public water supplier report drinking-water monitoring for Onalaska, Wisconsin to the EPA. Each is listed above with its population served.
What contaminants are in Onalaska's water?
The contaminants EPA monitoring detected in Onalaska include Nitrate-Nitrite, Nitrate, Copper, Fluoride, Total Haloacetic Acids (HAA5). 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.