Data & Methodology — Big Stone County

Full contaminant data, sample history, and sourcing for Big Stone County. For readers who want to go beyond the summary.

Contaminant Data — All Analytes

46 well testing events on record, covering 19 analytes. Data spans 1952 to 2023.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. MN Avg
Iron 34 1963–2007 100%
717% of limit ~ typical
Manganese 34 1963–2007 97%
624% of limit ↑ 27% above
Sulfate 36 1963–2014 100%
168% of limit ↑ 788% above
Arsenic 9 1994–2006 89%
20% of limit ↓ 76% below
PFOA municipal 4 2024 50%
179% of limit ↓ 58% below
Uranium 4 2006 100%
1% of limit ↓ 78% below
Lead 9 1994–2006 78%
1% of limit ↓ 98% below
Chloride 43 1963–2025 100%
5% of limit ↓ 34% below
Nitrate 30 1963–2007 83%
6% of limit ↓ 75% below
Fluoride 34 1963–2007 91%
8% of limit ~ typical
HFPO-DA (GenX) municipal 2 2024 0%
— —
Nitrite 14 1979–2007 79%
0% of limit ↓ 87% below
PFHxS municipal 2 2024 0%
— —
PFNA municipal 2 2024 0%
— —
PFOS municipal 2 2024 0%
— —
Sodium 33 1963–2007 100%
— ↑ 377% above
pH 18 1963–1981 100%
— ~ typical
PFBS municipal 2 2024 0%
— —
Hardness 18 1963–1981 100%
— ↑ 40% above

Distribution shows the share of samples in each concentration band relative to the EPA Maximum Contaminant Level (MCL): Low = below half the MCL, Moderate = between half and the MCL, High = above the MCL. Analytes without an MCL (e.g. sodium, pH) show — in the limit columns. State average is based on county median values across MN.

Compare your result with Big Stone County

Of the 43 chloride tests on record for Big Stone County (1963–2025), 0% found none, and half were below 12.7 mg/L.

Of the 34 fluoride tests on record for Big Stone County (1963–2007), 9% found none, and half were below 300 µg/L.

Of the 34 iron tests on record for Big Stone County (1963–2007), 0% found none, and half were below 2.15 mg/L.

Of the 34 manganese tests on record for Big Stone County (1963–2007), 3% found none, and half were below 276 µg/L.

Of the 30 nitrate tests on record for Big Stone County (1963–2007), 17% found none, and half were below 77.5 µg/L.

Of the 36 sulfate tests on record for Big Stone County (1963–2014), 0% found none, and half were below 420 mg/L.

Have a number from your lab? Enter it to see where it falls. Nothing is sent anywhere.

Want the full picture for your well? Check all your results.

Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Iron 34 samples
  • Manganese 34 samples
  • Sulfate 36 samples
  • Chloride 43 samples
  • Nitrate 30 samples
  • Fluoride 34 samples
  • Sodium 33 samples
  • pH 18 samples
  • Hardness 18 samples

Limited data (<15 samples) — interpret with caution

  • Arsenic 9 samples
  • PFOA 4 samples
  • Uranium 4 samples
  • Lead 9 samples
  • Nitrite 14 samples

Public vs. Private Water in Big Stone County

17 Active public water systems
4,078 Residents on public water
26% Households on private wells

Public water systems in Big Stone County are regulated by the EPA and must test and report contaminant levels. Private well owners are responsible for their own testing — there is no routine monitoring of private wells by any government agency.

CDC Health Outcome Correlations

Where contaminants detected in Big Stone County have established associations with specific health outcomes, we cross-reference CDC PLACES county-level prevalence data. This is a contextual signal, not a causal claim.

Contaminant Associated Condition Big Stone County Prevalence MN Average Source Year
Arsenic Cancer prevalence 9.5% 7.0% 2020
Arsenic Kidney disease rate 3.9% 2.9% 2020
Lead Heart disease rate 9.6% 6.6% 2020

Source: CDC PLACES county-level estimates. Raw data: Download Big Stone County CDC PLACES data →

Data Sources

This report aggregates data from the following public databases:

Methodology

Raw records are downloaded from the Water Quality Portal and normalized to µg/L (ppb). Records are deduplicated by sample ID and date, and certified outliers are excluded. Analyte names are mapped to EPA canonical forms. Detection rates, distribution bands, and MCL comparisons are computed from the normalized dataset.

Distribution bands use the EPA Maximum Contaminant Level as the threshold: concentrations below 50% of the MCL are classed as Low, between 50% and 100% as Moderate, and above 100% as High. For analytes without an MCL (sodium, hardness, pH), distribution is not computed.

State comparison uses the median of county median values across all counties in MN with at least one sample for that analyte.

Last updated: 2026-08-04

Full methodology →