Nitrate in Idaho well water
In Idaho, 7% of 10,012 tested private well samples exceeded the EPA limit for nitrate (10 mg/L).
Nitrate reaches wells from fertilizer, septic systems and manure. Above the limit it can cause methemoglobinemia (blue baby syndrome) in infants under six months, and long-term exposure is associated with some cancers. Shallow and dug wells near farmland or dense septic systems are most at risk.
Check your nitrate number
Type the value from your lab report. It is compared to the EPA limit, the same way the full interpretation does it.
Getting it fixed
Book a free in-home water test with a licensed local company, or see the treatment guide for what removes nitrate.
By county, from individual samples
Public monitoring samples against the EPA limit (10 mg/L); counties with at least 30 samples.
| County | Samples | Detected | Above EPA limit | Median | Highest |
|---|---|---|---|---|---|
| Washington | 263 | 76% | 35% | 5.25 | 92.7 mg/L |
| Lewis | 96 | 99% | 18% | 2.01 | 79.5 mg/L |
| Minidoka | 286 | 85% | 17% | 3.85 | 130 mg/L |
| Owyhee | 266 | 68% | 16% | 1.02 | 106 mg/L |
| Cassia | 255 | 98% | 11% | 4.19 | 17 mg/L |
| Canyon | 1,530 | 89% | 10% | 3.2 | 30.4 mg/L |
| Payette | 534 | 83% | 9% | 3.31 | 61 mg/L |
| Elmore | 358 | 87% | 9% | 1.32 | 73.3 mg/L |
| Gooding | 151 | 99% | 9% | 1.89 | 20.6 mg/L |
| Bingham | 251 | 99% | 8% | 1.85 | 47.3 mg/L |
| Fremont | 202 | 94% | 8% | 1.62 | 42.6 mg/L |
| Twin Falls | 632 | 98% | 7% | 4.59 | 30.5 mg/L |
| Gem | 282 | 71% | 7% | 1.17 | 21 mg/L |
| Power | 193 | 96% | 6% | 1.6 | 43 mg/L |
| Boundary | 116 | 66% | 6% | 0.084 | 31 mg/L |
- Fort Hall CCD, Bingham County48% of 42
- Weiser CCD, Washington County37% of 246
- Nezperce CCD, Lewis County35% of 31
- Heyburn CCD, Minidoka County29% of 84
- Grand View CCD, Owyhee County26% of 98
- Wilder CCD, Canyon County25% of 146
- Gooding CCD, Gooding County22% of 50
- Rupert CCD, Minidoka County20% of 116
- West Salmon Falls CCD, Twin Falls County18% of 44
- Marsing CCD, Owyhee County17% of 47
- Fruitland CCD, Payette County17% of 147
- Burley CCD, Cassia County17% of 84
- Bonners Ferry CCD, Boundary County16% of 45
- Notus CCD, Canyon County15% of 111
- Bruneau CCD, Owyhee County14% of 37
- Ashton CCD, Fremont County13% of 64
- Eagle CCD, Ada County12% of 227
- Emmett Bench CCD, Gem County11% of 180
- Buhl CCD, Twin Falls County10% of 105
- Orchard CCD, Ada County10% of 115
Sources
- Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. nitrate counts and shares are listed on each county and town page with their sources.