What was found in Thousand Oaks'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 | 619999.9999999995 µg/L 6200% of the EPA limit, at the 95th percentile of samples — 10000 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Nitrate | 1000 µg/L 10% of the EPA limit 10000 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Fluoride | 900 µg/L 23% of the EPA limit 4000 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Nitrite | 425 µg/L 43% of the EPA limit 1000 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Copper | 264.99999999999943 µg/L 20% of the EPA limit 1300 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Barium | 77.615 µg/L 3.9% of the EPA limit 2000 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| TTHM | 43.785 µg/L 55% of the EPA limit 80 µg/L Main supplier: CITY OF THOUSAND OAKS WATER DEPARTMENT · 53,157 people · 2019 | 2/2 | SYR4 |
| Bromoform | 17.624999999999996 µg/L No EPA limit set Main supplier: CITY OF THOUSAND OAKS WATER DEPARTMENT · 53,157 people · 2019 | 2/2 | SYR4 |
| Selenium | 14.25 µg/L 28% of the EPA limit 50 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Total Haloacetic Acids (HAA5) | 10 µg/L 17% of the EPA limit 60 µg/L Main supplier: CITY OF THOUSAND OAKS WATER DEPARTMENT · 53,157 people · 2019
Highest in the city: 14 µg/L — CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 2/2 | SYR4 |
| Chromium | 13.999999999999957 µg/L 14% of the EPA limit 100 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Dibromochloromethane | 13.7 µg/L No EPA limit set Main supplier: CITY OF THOUSAND OAKS WATER DEPARTMENT · 53,157 people · 2019 | 2/2 | SYR4 |
| Bromodichloromethane | 7.669999999999999 µg/L No EPA limit set Main supplier: CITY OF THOUSAND OAKS WATER DEPARTMENT · 53,157 people · 2019 | 2/2 | SYR4 |
| Combined Uranium | 7.5766499999999946 µg/L 25% of the EPA limit 30 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Dibromoacetic Acid | 7 µg/L No EPA limit set Main supplier: CITY OF THOUSAND OAKS WATER DEPARTMENT · 53,157 people · 2019 | 2/2 | SYR4 |
| Bromate | 6.7 µg/L 67% of the EPA limit 10 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Lead | 6.379999999999998 µg/L 43% of the EPA limit 15 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Dichloroacetic Acid | 4 µg/L No EPA limit set Main supplier: CITY OF THOUSAND OAKS WATER DEPARTMENT · 53,157 people · 2019
Highest in the city: 6 µg/L — CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 2/2 | SYR4 |
| Dinoseb | 6 µg/L 86% of the EPA limit 7 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Monobromoacetic Acid | 3 µg/L No EPA limit set Main supplier: CITY OF THOUSAND OAKS WATER DEPARTMENT · 53,157 people · 2019
Highest in the city: 6 µg/L — CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 2/2 | SYR4 |
| Monochloroacetic Acid | 3 µg/L No EPA limit set Main supplier: CITY OF THOUSAND OAKS WATER DEPARTMENT · 53,157 people · 2019
Highest in the city: 6 µg/L — CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 2/2 | SYR4 |
| Chloroform | 4.639999999999997 µg/L No EPA limit set Main supplier: CITY OF THOUSAND OAKS WATER DEPARTMENT · 53,157 people · 2019
Highest in the city: 5.9899999999999975 µg/L — CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 2/2 | SYR4 |
| Arsenic | 5.899999999999999 µg/L 59% of the EPA limit 10 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Gross Beta Particle Activity | 4 pCi/L No EPA limit set Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Trichloroacetic Acid | 2 µg/L No EPA limit set Main supplier: CITY OF THOUSAND OAKS WATER DEPARTMENT · 53,157 people · 2019
Highest in the city: 3.700000000000003 µg/L — CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 2/2 | SYR4 |
| Dichloromethane | 3.4400000000000017 µg/L 69% of the EPA limit 5 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Xylenes, Total | 1.175 µg/L 0% of the EPA limit 10000 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Cadmium | 0.2000 µg/L 4% of the EPA limit 5 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Mercury | 0.1620 µg/L 8.1% of the EPA limit 2 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| 1,2-DIBROMO-3-CHLOROPROPANE | 0.0100 µg/L 5% of the EPA limit 0.2000 µg/L Highest in the city: CALLEGUAS MUNICIPAL WATER DIST · 0 people · 2019 | 1/2 | SYR4 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: CITY OF THOUSAND OAKS WATER DEPARTMENT · 53,157 people · 2025 | 1/2 | 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 Thousand Oaks
| Supplier | Population served |
|---|---|
| CITY OF THOUSAND OAKS WATER DEPARTMENT | 53,157 |
| CALLEGUAS MUNICIPAL WATER DIST | 0 |
Frequently asked questions about Thousand Oaks tap water
Is Thousand Oaks tap water safe to drink?
EPA testing detected 31 contaminants in the water serving Thousand Oaks. 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 Thousand Oaks?
2 public water suppliers report drinking-water monitoring for Thousand Oaks, California to the EPA. Each is listed above with its population served.
What contaminants are in Thousand Oaks's water?
The contaminants EPA monitoring detected in Thousand Oaks include Nitrate-Nitrite, Nitrate, Fluoride, Nitrite, Copper. 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.