What was found in Lewiston'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 | 19700 µg/L 197% of the EPA limit, at the 95th percentile of samples — 10000 µg/L Highest in the city: EATON MOBILE HOME COURT · 94 people · 2019 | 5/9 | SYR4 |
| Nitrate-Nitrite | 6882 µg/L 69% of the EPA limit 10000 µg/L Highest in the city: LEWISTON CITY OF · 15,001 people · 2019 | 4/9 | SYR4 |
| Fluoride | 3086.5 µg/L 77% of the EPA limit 4000 µg/L Main supplier: LEWISTON ORCHARDS IRRIGATION DIST · 20,000 people · 2018 | 9/9 | SYR4 |
| Nitrite | 374.3 µg/L 37% of the EPA limit 1000 µg/L Highest in the city: LEWISTON CITY OF · 15,001 people · 2019 | 1/9 | SYR4 |
| Barium | 14.87 µg/L 0.7% of the EPA limit 2000 µg/L Main supplier: LEWISTON ORCHARDS IRRIGATION DIST · 20,000 people · 2019
Highest in the city: 113 µg/L — LEWISTON CITY OF · 15,001 people · 2019 | 9/9 | SYR4 |
| Copper | 55.34 µg/L 4.3% of the EPA limit 1300 µg/L Highest in the city: EATON MOBILE HOME COURT · 94 people · 2016 | 2/9 | SYR4 |
| TTHM | 12.28 µg/L 15% of the EPA limit 80 µg/L Main supplier: LEWISTON ORCHARDS IRRIGATION DIST · 20,000 people · 2019
Highest in the city: 51.58 µg/L — LEWISTON CITY OF · 15,001 people · 2019 | 4/9 | SYR4 |
| Lithium | 39.4 µg/L No EPA limit set Main supplier: LEWISTON ORCHARDS IRRIGATION DIST · 20,000 people · 2024
Highest in the city: 43.8 µg/L — LEWISTON CITY OF · 15,001 people · 2025 | 2/9 | UCMR-5 |
| Total Haloacetic Acids (HAA5) | 3.347 µg/L 5.6% of the EPA limit 60 µg/L Main supplier: LEWISTON ORCHARDS IRRIGATION DIST · 20,000 people · 2019
Highest in the city: 37.73 µg/L — LEWISTON CITY OF · 15,001 people · 2019 | 3/9 | SYR4 |
| Combined Uranium | 24.521 µg/L 82% of the EPA limit 30 µg/L Highest in the city: LEWISTON CITY OF · 15,001 people · 2019 | 3/9 | SYR4 |
| Gross Beta Particle Activity | 8.206 pCi/L No EPA limit set Highest in the city: LEWISTON CITY OF · 15,001 people · 2019 | 2/9 | SYR4 |
| Gross Alpha, Excl. Radon And U | 0.1434 pCi/L 1% of the EPA limit 15 pCi/L Main supplier: LEWISTON ORCHARDS IRRIGATION DIST · 20,000 people · 2016
Highest in the city: 7.245 pCi/L — LEWISTON CITY OF · 15,001 people · 2019 | 4/9 | SYR4 |
| Chloroform | 6.31 µg/L No EPA limit set Highest in the city: LEWISTON CITY OF · 15,001 people · 2019 | 1/9 | SYR4 |
| Selenium | 3.364 µg/L 6.7% of the EPA limit 50 µg/L Highest in the city: LEWISTON CITY OF · 15,001 people · 2019 | 5/9 | SYR4 |
| Bromodichloromethane | 3.2 µg/L No EPA limit set Highest in the city: LEWISTON CITY OF · 15,001 people · 2019 | 1/9 | SYR4 |
| Chromium | 1.6565 µg/L 1.7% of the EPA limit 100 µg/L Main supplier: LEWISTON ORCHARDS IRRIGATION DIST · 20,000 people · 2019
Highest in the city: 2.91 µg/L — LEWISTON CITY OF · 15,001 people · 2019 | 8/9 | SYR4 |
| Arsenic | 1.34 µg/L 13% of the EPA limit 10 µg/L Main supplier: LEWISTON ORCHARDS IRRIGATION DIST · 20,000 people · 2019
Highest in the city: 2.38 µg/L — EATON MOBILE HOME COURT · 94 people · 2019 | 7/9 | SYR4 |
| Lead | 2.308 µg/L 15% of the EPA limit 15 µg/L Highest in the city: EATON MOBILE HOME COURT · 94 people · 2016 | 2/9 | SYR4 |
| Combined Radium (-226 And -228) | 0.7094 pCi/L 14% of the EPA limit 5 pCi/L Main supplier: LEWISTON ORCHARDS IRRIGATION DIST · 20,000 people · 2019
Highest in the city: 1.2612 pCi/L — EATON MOBILE HOME COURT · 94 people · 2018 | 7/9 | SYR4 |
| Picloram | 1.2105 µg/L 0.2% of the EPA limit 500 µg/L Highest in the city: RED ROCK WATER LLC · 60 people · 2018 | 2/9 | SYR4 |
| Dibromochloromethane | 1.15 µg/L No EPA limit set Highest in the city: LEWISTON CITY OF · 15,001 people · 2019 | 1/9 | SYR4 |
| Cadmium | 1.07 µg/L 21% of the EPA limit 5 µg/L Highest in the city: LEWISTON CITY OF · 15,001 people · 2019 | 1/9 | SYR4 |
| Toluene | 0.7800 µg/L 0.1% of the EPA limit 1000 µg/L Highest in the city: VIEW POINT SUBDIVISION · 56 people · 2019 | 1/9 | SYR4 |
| PFBS | 0.0056 µg/L No EPA limit set Highest in the city: LEWISTON CITY OF · 15,001 people · 2025 | 1/9 | UCMR-5 |
| Pfpea | 0.0047 µg/L No EPA limit set Highest in the city: LEWISTON CITY OF · 15,001 people · 2025 | 1/9 | UCMR-5 |
| Pfhxa | 0.0043 µg/L No EPA limit set Highest in the city: LEWISTON CITY OF · 15,001 people · 2025 | 1/9 | UCMR-5 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: LEWISTON ORCHARDS IRRIGATION DIST · 20,000 people · 2024
Highest in the city: 0.0010 mg/L — LEWISTON CITY OF · 15,001 people · 2025 | 9/9 | LCR |
| Asbestos | -0.34 MFL -4.9% of the EPA limit 7 MFL Main supplier: LEWISTON ORCHARDS IRRIGATION DIST · 20,000 people · 2013
Highest in the city: -0.13 MFL — LEWISTON CITY OF · 15,001 people · 2013 | 2/9 | SYR4 |
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 Lewiston
| Supplier | Population served |
|---|---|
| LEWISTON ORCHARDS IRRIGATION DIST | 20,000 |
| LEWISTON CITY OF | 15,001 |
| RED PHEASANT WATER COMPANY LLC | 480 |
| COUGAR RIDGE WATER & SEWER | 173 |
| EAGLES POINTE SUBDIVISION | 110 |
| WAHA GLEN WATER DIST | 100 |
| EATON MOBILE HOME COURT | 94 |
| RED ROCK WATER LLC | 60 |
| VIEW POINT SUBDIVISION | 56 |
Frequently asked questions about Lewiston tap water
Is Lewiston tap water safe to drink?
EPA testing detected 28 contaminants in the water serving Lewiston. 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 Lewiston?
9 public water suppliers report drinking-water monitoring for Lewiston, Idaho to the EPA. Each is listed above with its population served.
What contaminants are in Lewiston's water?
The contaminants EPA monitoring detected in Lewiston include Nitrate, Nitrate-Nitrite, Fluoride, Nitrite, Barium. 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.