What was found in Boulder'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 | 150 µg/L 1.5% of the EPA limit 10000 µg/L Main supplier: BOULDER CITY OF · 166,080 people · 2019
Highest in the city: 3400 µg/L — SPRING VALLEY MUTUAL WA · 100 people · 2019 | 5/10 | SYR4 |
| Fluoride | 810 µg/L 20% of the EPA limit 4000 µg/L Main supplier: BOULDER CITY OF · 166,080 people · 2019
Highest in the city: 1869 µg/L — SHANNON WSD · 450 people · 2019 | 5/10 | SYR4 |
| Nitrate-Nitrite | 1100 µg/L 11% of the EPA limit 10000 µg/L Highest in the city: SPRING VALLEY MUTUAL WA · 100 people · 2012 | 2/10 | SYR4 |
| Barium | 22.35 µg/L 1.1% of the EPA limit 2000 µg/L Main supplier: BOULDER CITY OF · 166,080 people · 2019
Highest in the city: 114.8 µg/L — SANS SOUCI COOPERATIVE · 150 people · 2019 | 5/10 | SYR4 |
| TTHM | 58.575 µg/L 73% of the EPA limit 80 µg/L Main supplier: BOULDER CITY OF · 166,080 people · 2019
Highest in the city: 99.425 µg/L — PINE BROOK HILLS WD · 1,100 people · 2019 | 10/10 | SYR4 |
| Total Haloacetic Acids (HAA5) | 65.05 µg/L 108% of the EPA limit, at the 95th percentile of samples — 60 µg/L Main supplier: BOULDER CITY OF · 166,080 people · 2019 | 10/10 | SYR4 |
| Chloroform | 29.71 µg/L No EPA limit set Main supplier: BOULDER CITY OF · 166,080 people · 2019
Highest in the city: 58.445 µg/L — VISTA VILLAGE MHP · 750 people · 2019 | 9/10 | SYR4 |
| Trichloroacetic Acid | 13.925 µg/L No EPA limit set Main supplier: BOULDER CITY OF · 166,080 people · 2019
Highest in the city: 31.27 µg/L — VISTA VILLAGE MHP · 750 people · 2019 | 7/10 | SYR4 |
| Bromodichloromethane | 4.5035 µg/L No EPA limit set Main supplier: BOULDER CITY OF · 166,080 people · 2019
Highest in the city: 21.2 µg/L — PINE BROOK HILLS WD · 1,100 people · 2019 | 9/10 | SYR4 |
| Dichloroacetic Acid | 11.575 µg/L No EPA limit set Main supplier: BOULDER CITY OF · 166,080 people · 2019
Highest in the city: 19.91 µg/L — VISTA VILLAGE MHP · 750 people · 2019 | 8/10 | SYR4 |
| Dibromochloromethane | 0.5896 µg/L No EPA limit set Main supplier: BOULDER CITY OF · 166,080 people · 2019
Highest in the city: 16.455 µg/L — EAST BOULDER COUNTY WD · 300 people · 2019 | 9/10 | SYR4 |
| Bromoform | 7.3 µg/L No EPA limit set Highest in the city: SHANNON WSD · 450 people · 2017 | 6/10 | SYR4 |
| Gross Alpha, Excl. Radon And U | 5.7275 pCi/L 38% of the EPA limit 15 pCi/L Highest in the city: SPRING VALLEY MUTUAL WA · 100 people · 2018 | 4/10 | SYR4 |
| Combined Uranium | 4.96 µg/L 17% of the EPA limit 30 µg/L Highest in the city: SPRING VALLEY MUTUAL WA · 100 people · 2018 | 1/10 | SYR4 |
| Dibromoacetic Acid | 4.432 µg/L No EPA limit set Highest in the city: SANS SOUCI COOPERATIVE · 150 people · 2019 | 6/10 | SYR4 |
| Selenium | 3.275 µg/L 6.6% of the EPA limit 50 µg/L Highest in the city: SANS SOUCI COOPERATIVE · 150 people · 2019 | 3/10 | SYR4 |
| Tetrachloroethylene | 3.1 µg/L 62% of the EPA limit 5 µg/L Main supplier: BOULDER CITY OF · 166,080 people · 2019 | 1/10 | SYR4 |
| Chromium | 1 µg/L 1% of the EPA limit 100 µg/L Main supplier: BOULDER CITY OF · 166,080 people · 2019
Highest in the city: 2.8 µg/L — SANS SOUCI COOPERATIVE · 150 people · 2019 | 5/10 | SYR4 |
| Monochloroacetic Acid | 2.5 µg/L No EPA limit set Highest in the city: PINE BROOK HILLS WD · 1,100 people · 2019 | 6/10 | SYR4 |
| Combined Radium (-226 And -228) | 2 pCi/L 40% of the EPA limit 5 pCi/L Highest in the city: SANS SOUCI COOPERATIVE · 150 people · 2019 | 3/10 | SYR4 |
| Monobromoacetic Acid | 1.2 µg/L No EPA limit set Highest in the city: LEFTHAND WSD LAKE PINES · 250 people · 2019 | 2/10 | SYR4 |
| Arsenic | 1 µg/L 10% of the EPA limit 10 µg/L Highest in the city: PINE BROOK HILLS WD · 1,100 people · 2019 | 1/10 | SYR4 |
| Lead | 0.0020 mg/L 13% of the EPA limit 0.0150 mg/L Main supplier: BOULDER CITY OF · 166,080 people · 2025
Highest in the city: 0.0040 mg/L — LEFTHAND WSD LAKE PINES · 250 people · 2006 | 9/10 | 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 Boulder
| Supplier | Population served |
|---|---|
| BOULDER CITY OF | 166,080 |
| PINE BROOK HILLS WD | 1,100 |
| MILE HI WATER INC HAULER | 1,000 |
| BASELINE WD | 820 |
| VISTA VILLAGE MHP | 750 |
| SHANNON WSD | 450 |
| EAST BOULDER COUNTY WD | 300 |
| LEFTHAND WSD LAKE PINES | 250 |
| SANS SOUCI COOPERATIVE | 150 |
| SPRING VALLEY MUTUAL WA | 100 |
Frequently asked questions about Boulder tap water
Is Boulder tap water safe to drink?
EPA testing detected 23 contaminants in the water serving Boulder. 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 Boulder?
10 public water suppliers report drinking-water monitoring for Boulder, Colorado to the EPA. Each is listed above with its population served.
What contaminants are in Boulder's water?
The contaminants EPA monitoring detected in Boulder include Nitrate, Fluoride, 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.