What was found in Napa'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 | 942600 µg/L 9426% of the EPA limit, at the 95th percentile of samples — 10000 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019 | 2/14 | SYR4 |
| Barium | 37.85 µg/L 1.9% of the EPA limit 2000 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019
Highest in the city: 4715 µg/L — NAPA RIVER RANCH · 70 people · 2019 | 12/14 | SYR4 |
| Nitrate | 1900 µg/L 19% of the EPA limit 10000 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019 | 9/14 | SYR4 |
| Fluoride | 213.4 µg/L 5.3% of the EPA limit 4000 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019
Highest in the city: 786 µg/L — MONDAVI FARM WORKER CENTER · 66 people · 2019 | 10/14 | SYR4 |
| Chlorite | 245 µg/L 25% of the EPA limit 1000 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019 | 1/14 | SYR4 |
| Arsenic | 4.617 µg/L 46% of the EPA limit 10 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019
Highest in the city: 120 µg/L — CALISTOGA FARM WORKER CENTER · 65 people · 2019 | 12/14 | SYR4 |
| TTHM | 99.15 µg/L 124% of the EPA limit, at the 95th percentile of samples — 80 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019
Highest in the city: 110 µg/L — BERRYESSA ESTATES (LBRID) · 474 people · 2019 | 9/14 | SYR4 |
| Copper | 96 µg/L 7.4% of the EPA limit 1300 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019 | 3/14 | SYR4 |
| Chromium | 92.115 µg/L 92% of the EPA limit 100 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019 | 6/14 | SYR4 |
| Chloroform | 77 µg/L No EPA limit set Main supplier: NAPA, CITY OF · 84,804 people · 2019
Highest in the city: 90.9 µg/L — BERRYESSA HIGHLANDS · 715 people · 2019 | 9/14 | SYR4 |
| Total Haloacetic Acids (HAA5) | 57.16 µg/L 95% of the EPA limit 60 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019
Highest in the city: 67.56 µg/L — BERRYESSA HIGHLANDS · 715 people · 2019 | 8/14 | SYR4 |
| Trichloroacetic Acid | 31.68 µg/L No EPA limit set Main supplier: NAPA, CITY OF · 84,804 people · 2019
Highest in the city: 46.45 µg/L — BERRYESSA ESTATES (LBRID) · 474 people · 2019 | 6/14 | SYR4 |
| Lead | 44.28 µg/L 295% of the EPA limit, at the 95th percentile of samples — 15 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019 | 2/14 | SYR4 |
| Bromodichloromethane | 25 µg/L No EPA limit set Main supplier: NAPA, CITY OF · 84,804 people · 2019
Highest in the city: 31.45 µg/L — BERRYESSA ESTATES (LBRID) · 474 people · 2019 | 9/14 | SYR4 |
| Dichloroacetic Acid | 23 µg/L No EPA limit set Main supplier: NAPA, CITY OF · 84,804 people · 2019
Highest in the city: 31.025 µg/L — BERRYESSA HIGHLANDS · 715 people · 2019 | 9/14 | SYR4 |
| Dibromochloromethane | 12 µg/L No EPA limit set Main supplier: NAPA, CITY OF · 84,804 people · 2019
Highest in the city: 22.75 µg/L — BERRYESSA ESTATES (LBRID) · 474 people · 2019 | 8/14 | SYR4 |
| Selenium | 16.9 µg/L 34% of the EPA limit 50 µg/L Highest in the city: MONDAVI FARM WORKER CENTER · 66 people · 2019 | 2/14 | SYR4 |
| Monobromoacetic Acid | 1.7 µg/L No EPA limit set Main supplier: NAPA, CITY OF · 84,804 people · 2019
Highest in the city: 16.605 µg/L — BERRYESSA HIGHLANDS · 715 people · 2019 | 4/14 | SYR4 |
| Dibromoacetic Acid | 2.355 µg/L No EPA limit set Main supplier: NAPA, CITY OF · 84,804 people · 2019
Highest in the city: 12.6 µg/L — NAPA RIVER RANCH · 70 people · 2012 | 6/14 | SYR4 |
| Monochloroacetic Acid | 8.36 µg/L No EPA limit set Main supplier: NAPA, CITY OF · 84,804 people · 2019 | 3/14 | SYR4 |
| Bromoform | 1.755 µg/L No EPA limit set Main supplier: NAPA, CITY OF · 84,804 people · 2019
Highest in the city: 7.82 µg/L — BERRYESSA ESTATES (LBRID) · 474 people · 2019 | 4/14 | SYR4 |
| Bromate | 5.775 µg/L 58% of the EPA limit 10 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019 | 1/14 | SYR4 |
| Combined Uranium | 2.831 µg/L 9.4% of the EPA limit 30 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019 | 1/14 | SYR4 |
| Cadmium | 2.245 µg/L 45% of the EPA limit 5 µg/L Main supplier: NAPA, CITY OF · 84,804 people · 2019 | 1/14 | SYR4 |
| Gross Beta Particle Activity | 1.6255 pCi/L No EPA limit set Main supplier: NAPA, CITY OF · 84,804 people · 2018 | 1/14 | SYR4 |
| Toluene | 1.1 µg/L 0.1% of the EPA limit 1000 µg/L Highest in the city: MILTON ROAD WATER COMPANY · 44 people · 2015 | 1/14 | SYR4 |
| Thallium, Total | 1 µg/L 50% of the EPA limit 2 µg/L Highest in the city: NAPA RIVER RANCH · 70 people · 2019 | 1/14 | SYR4 |
| Asbestos | 0.9980 MFL 14% of the EPA limit 7 MFL Highest in the city: BERRYESSA ESTATES (LBRID) · 474 people · 2018 | 2/14 | SYR4 |
| Beryllium, Total | 0.1700 µg/L 4.3% of the EPA limit 4 µg/L Highest in the city: CIRCLE OAKS WATER DISTRICT · 500 people · 2019 | 1/14 | SYR4 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: NAPA, CITY OF · 84,804 people · 2024
Highest in the city: 0.0082 mg/L — MEYERS WATER CO. · 250 people · 2025 | 14/14 | 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 Napa
| Supplier | Population served |
|---|---|
| NAPA, CITY OF | 84,804 |
| BERRYESSA HIGHLANDS | 715 |
| CIRCLE OAKS WATER DISTRICT | 500 |
| BERRYESSA ESTATES (LBRID) | 474 |
| BERRYESSA PINES WATER SYSTEM | 261 |
| MEYERS WATER CO. | 250 |
| HESS WINERY | 250 |
| SPANISH FLAT WATER DISTRICT | 230 |
| NAPA RIVER RANCH | 70 |
| RIVER RANCH FARM WORKER CENTER | 66 |
| MONDAVI FARM WORKER CENTER | 66 |
| CALISTOGA FARM WORKER CENTER | 65 |
| MILTON ROAD WATER COMPANY | 44 |
| R RANCH AT THE LAKE | 28 |
Frequently asked questions about Napa tap water
Is Napa tap water safe to drink?
EPA testing detected 30 contaminants in the water serving Napa. 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 Napa?
14 public water suppliers report drinking-water monitoring for Napa, California to the EPA. Each is listed above with its population served.
What contaminants are in Napa's water?
The contaminants EPA monitoring detected in Napa include Nitrate-Nitrite, Barium, Nitrate, Fluoride, Chlorite. 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.