Well water in Sioux County, Nebraska
In Sioux County, 6% of 118 tested well samples exceeded the EPA limit for nitrate (10 mg/L), based on public data from USGS Water Quality Portal and Nebraska Groundwater Quality Clearinghouse.
312 individual samples from 79 wells, 1954 to 2024. Data refreshed September 9, 2026.
What individual samples found
Each row summarizes every public sample for that contaminant inside Sioux County. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.
| Contaminant | Samples | Detected | Above limit | Median | Highest | Limit | |
|---|---|---|---|---|---|---|---|
| Nitrate 1979 to 2024 | 118 | 99% | 6% | 3.35 | 34 | 10 mg/L EPA limit | |
| Radon 1991 to 1999 | 312 | 99% | no limit | 350 | 1,910 | 2,000 pCi/L health guideline | |
| Sodium 1996 to 1998 | 11 | 100% | no limit | 48 | 53.5 | 20 mg/L health guideline |
Sampled fewer than 10 times, too few to summarize: Uranium (6), Radium (226 + 228) (5), Fluoride (3), Arsenic (1), Chloride (6), Manganese (4), Iron (4).
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What this means
The contaminants most often above their limit here are nitrate (6% of 118 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.
Chloride is widespread in local groundwater. It is mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Sioux County
- Nitrate6% of 118 local samples were above the limit.
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 350 pCi/L.
- FluorideDetected in 100% of local samples.
- ChlorideDetected in 100% of local samples.
Treatment that fits the local profile
- Nitrate
- Point-of-use reverse osmosis; Anion exchange; Distillation
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
- Chloride
- Point-of-use reverse osmosis; Distillation
Get your Sioux County water tested at home
A licensed local water treatment company tests your tap water in your home, walks you through the numbers, and quotes treatment only if something needs fixing. Free, about 30 minutes, no obligation. Tell us what you need and we match you with a company that serves Sioux County.
Common questions
Is there arsenic in well water in Sioux County?
Arsenic was detected in 100% of 1 public well samples in Sioux County, and 0% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.
How high is radon in well water in Sioux County?
The median radon level across 312 public samples in Sioux County was 350 pCi/L, with a high of 1,910 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Sioux County?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Sources
- USGS Water Quality Portal: 360 samples in Sioux County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- Nebraska Groundwater Quality Clearinghouse: 110 samples in Sioux County. Groundwater quality results compiled by the Nebraska Department of Environment and Energy, University of Nebraska and Nebraska Department of Agriculture in the Groundwater Quality Clearinghouse, contributed by Natural Resources Districts and state agencies. Retrieved September 9, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.